Alkyl Polyglycosides: Technology, Properties, and Applications

Alkyl Polyglycosides Edited by K. Hill, W. von Rybinski, G. Stoll

0VCH Verlagsgesellschaft mbH, D-69451 Weinheim (Federal Republic of Germany) 1997 Distribution: VCH, P.O.Box 10 1161, D-69451 Weinheim, Federal Republic of Germany Switzerland VCH, P.O. Box, CH-4020 Basel, Switzerland United Kingdom and Ireland: VCH, 8 Wellington Court, Cambridge CB1 l H Z , United Kingdom USA and Canada: VCH, 220 East 23rd Street, New York, NY 1001011606,USA Japan: VCH, Eikow Building, 10-9Hongo 1-chome, Bunkyo-ku, Tokyo 113,Japan

ISBN 3-527-29451-1

Alkyl Polyglycosides Technology, Properties and Applications

Edited by K. Hill,W. von Rybinski, G. Stoll

+

VCH

Weinheim - New York Base1 - Cambridge - Tokyo

Dr. KarlheinzHill Dr. Wolfgang von Rybinski Dr. Gerhard Stoll Henkel KGaA D-40191 Dusseldorf Germany

This book was carefully produced. Nevertheless, authors, editors and publisher do not warrant the information contained therein to be free of errors. Readers are advised to keep in mind that statements,data, illustrations, proceduraldetailsor other items may inadvertentlybe inaccurate. I

I

Publishedjointly by VCH VerlagsgesellschaftmbH, Weinheim (Federal Republic of Germany) VCH Publishers Inc., New York, NY (USA) Editorial Director: Dr. Michael Bar Translation: Roger C. S. Tunn, Sevenoaks, GB Library of Congress Card No. applied for.

A catalogue record for this book is available from the British Library. Die Deutsche Bibliothek - CIP Einheitsaufahme Alkyl polyglycosides /ed. by K. Hill ... [Transl.: Roger C. S . Tunn]. Weinheim ;New York ;Basel ;Cambridge ;Tokyo : VCH, 1996 ISBN 3-527-29451-1 NE: Hill, Karlheinz [Hrsg.]

0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim (Federal Republic of Germany), 1997

Printed on acid-free and chlorine-free paper. All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form - by photoprinting,microfilm, or any other means - nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law. APG", Agrimul", GlucopoP, PlantacareO and Plantaren- are registered trademarks of the Henkel Group for alkyl polyglycoside products. Printed in the Federal Republicof Germany Setting: Graphics: Reproduction: Printing: Bookbinding:

Dr. Ulrich Zeidler, Henkel KGaA, D-40191 Diisseldorf, Germany Design-Studio Venek, D-40191 Dusseldorf, Germany Satzmaker GmbH, D40595Diisseldorf Betzdruck GmbH, D-64291 Darmstadt GrohbuchbindereiJ. Schaffer GmbH & Co.KG, D-67269 Griinstadt

Foreword

With the beginning of the development of alkyl polyglycosides more than 15 years ago, the foundations were laid for another important milestone in the history of fatty alcohol derivatives. The product concept is more relevant now than ever, embracing as it does the exclusive use of renewable raw materials, namely sugars, for example glucose from starch, on the one hand and fatty alcohol from vegetable oil on the other. The research and development work was successful in solving both the chemical and performance-related problems and also technological problems. As a result, alkyl polyglycosides have been commercially available in industrial quantities for some time. At Henkel, these surfactants are now manufactured in two production plants-one in the USA and one in Germany-in a total capacity of almost 50,000tonnes per year and are used in a variety of products. In recent years, scientific institutes and companies active in the alkyl polyglycoside field have published a multitude of results in the form of patent specifications,papers and articles in specialist scientific journals. However, there has never been a comprehensive account of alkyl polyglycosides as a class of substances. We would like to fill this gap with the present book. Authors in the Henkel Group have put together results from the various fields. Scientific principles are discussed and fields of application considered. There can of course be no claim to completeness. The individual contributions intentionally show the hand of their authors to whom we express our sincere thanks. We very much hope that this compilation will lead to an even better understanding of alkyl polyglycosides and to stimulating discussions. We would also like especially to thank Dr. Karlheinz Hill, Dr. Wolfgang von Rybinski and Dr. Gerhard Stoll who were responsible for the conception of the book and for putting the various contributions together. We deeply mourn the loss of our colleague, Dr. Stoll, who died shortly before the book was completed.

Dr. Wilfried Umbach

Dr. Harald Wulff

Dusseldorf, November 1996

Contents

Foreword

V

Contents

VII

1. History of Alkyl Polyglycosides

Karlheinz Hill 1. Developments in industry 2. Chemistry 2. Technology and Production of Alkyl Polyglycosides Rainer Eskuchen and Michael Nitsche 1. Raw materials for the manufacture of alkyl polyglycosides 2. Degree of polymerization 3. Synthesis processes for the production of alkyl polyglycosides 4. Requirements for the industrial production of water-soluble alkyl polyglycosides 5. Production of water-insoluble alkyl polyglycosides 6. Examples of technical products 3. Analysis of Alkyl Polyglycosides and Determination in Consumer Products and Environmental Matrices Heinrich WaldhofiJudith Scherler, Michael Schmitt, and Jan R. VarviI 1. Analytical characterization of main and trace components in alkyl polyglycosides 2. Alkyl polyglycoside analysis in formulated products 3. Alkyl polyglycoside trace determination in environmental matrices 4. Future demands in alkyl polyglycoside analysis 4. Physicochemical Properties of Alkyl Polyglycosides

Dieter Nickel, Thomas Forster, and WoIfang von Rybinski 1. Phase behavior 2. Rheological properties 3. Interfacial properties 4. Microemulsion phases 5. Adsorption on solid surfaces

1 1

2

9 9 11 12

14

18 21

23

24 30 35 38

39 39 49

51 57 63

VIII

Contents

5. Alkyl Polyglycosides in Personal Care Products Hoker EsmannJorg Kahre, Hermann Hensen, and Barry A. Salka 1. Cosmetic cleansing formulations 2. Performance properties 3. Cosmetic emulsion preparations 4. Miscellaneous applications 5. Formulations

71 72 76 82 86 87

6. Alkyl Polyglycosides in Hard Surface Cleaners

and Laundry Detergents Hans AndreeJ. Frederick Hessel, Peter Krings, Georg Meine, Sirgit Middelhauve, and Iczrl Schmid 1. Alkyl polyglycosides in manual dishwashing detergents 2. Alkyl polyglycosides in cleaners 3. Alkyl polyglycosides in laundry detergents 7. Alkyl Polyglycosides -New Solutions for Agricultural Applications Roger Garst 1. Favorable features 2. Agricultural product line 3. Regulatory status 4. Comparative physical properties 5. Salt tolerance and adjuvancy 6. New adjuvant formulations 7. Adjuvant efficacy 8. Environmental effects 9. Conclusions

99

99 117 125

131 131 132 132 132 134 135 136 136 137

8. New Nonionic Derivatives of Alkyl Polyglycosides-

Synthesis and Properties Oliver Rhode, Manfed Weuthen, and Dieter Nickel 1. Synthesis of alkyl polyglycoside glycerol ethers 2. Synthesis of alkyl polyglycoside carbonates 3. Synthesis of alkyl polyglycoside butyl ethers 4. Interfacial properties 9. Toxicology of Alkyl Polyglycosides Walter Aulmann and Walter Stenel 1. Acute toxicity 2. Dermal irritation 3. Mucous membrane irritation (eye irritation) 4. Skin sensitization

139 140 14 1 143 144

151 152 154 156 159

IX

Contents

5. Mutagenicity 6. Toxicokinetics and metabolism 7. Subchronic toxicity 8. Conclusions

10. Dermatological Properties of Alkyl Polyglycosides

161 163 163 165

169

Worfang Matthies, BettinaJackwerth, and Hans- Udo Krachter Open application Occlusive application Application tests Use test Market observation in regard to unwanted effects Overall dermatological picture

169

11. Ecological Evaluation of Alkyl Polyglycosides

177

1. 2. 3. 4. 5. 6.

169

172 174 175 175

Josef Steber, Walter Guhl, Norbert Stelter, and Frank Roland Schroder 1. Biodegradation data 2. Ecotoxicological data 3. Environmental risk assessment and conclusions

12. Life-Cycle Inventory of Alkyl Polyglycosides

177 184 187

191

Frank Hirsinger 1. Manufacturing process 2. Total resource requirements and environmental emissions 3. Improvement opportunities

13. Patent Situation in the Field of Alkyl Polyglycosides

191 197 209

211

Bernd Fabry 1. 2. 3. 4.

Production of alkyl polyglycosides Mixtures of alkyl polyglycosides and other surfactants Alkyl polyglycoside derivatives Conclusions

14. Surfactants in Consumer Products and Raw Material Situation-A Brief Survey

213 215 221 222

225

Gunter Kreienfeld and Gerhard Stoll 1. Historical review

2. 3. 4. 5.

Present situation Basic oleochemicals Raw materials Outlook

225 227 228 231 233

Contributors

235

Index

237

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

1. History of Alkyl Polyglycosides Karlheinz Hill 1. Developments in industry

Alkyl glucosides-or alkyl polyglycosides as the industrially manufactured products are widely known-are a classic example of products which, for a long time, were of academic interest only. The first alkyl glucoside was synthesized and identified in the laboratory by Emil Fischer more than 100 years ago [ 11. The first patent application describing the use of alkyl glucosides in detergents was filed in Germany some 40 years later [21. Thereafter, another 40 to 50 years went by before research groups in various companies redirected their attention on alkyl glucosides and developed technical processes for the production of alkyl polyglycosides on the basis of the synthesis discovered by Fischer. In the course of this development, Fischer's early work, which involved the reaction of glucose with hydrophilic alcohols, such as methanol, ethanol, glycerol, etc., was applied to hydrophobic alcohols with alkyl chains from octyl (Cs) up to hexadecyl (C16)-the typical fatty alcohols. Fortunately, with regard to their applicational properties, not pure alkyl monoglucosides, but a complex mixture of alkyl mono-, di-, tri-, and oligoglycosides,are produced in the industrial processes. Because of this, the industrial products are called alkyl polyglycosides. The products are characterized by the length of the alkyl chain and the average number of glycose units linked to it, the degree of polymerization (Figure 1). Rohm & Haas was the first to market an octyl/decyl (C8/1~) polyglycoside in commercial quantities in the late seventies,followed by BASF and later SEPPIC. However, owing to the unsatisfactory performance of this short-chain version as a surfactant and its poor colour quality, applications were limited to few market segments, for example the industrial and institutional sectors.

I

,

:

L

HO

OH IDP

R = (fatty) alkyl group DP = average number of glycose units/alkyl chain (R) (degree of polymerization)

Figure 1. Molecular formula of alkyl polyglycosides

2

Karlheinz Hill

The product quality of such short chain alkyl polyglycosides has been improved in the last couple of years and new types of octyl/decyl polyglycoside are currently being offered by various companies, among them BASF, SEPPIC, Akzo Nobel, ICI and Henkel. At the beginning of the 1980s, several companies started programs to develop alkyl polyglycosides in a longer alkyl chain range (dodecyl/tetradecyl, Cn/14)with a view to making a new surfactant available to the cosmetics and detergent industries. They included Henkel KGaA, Diisseldorf, Germany, and Horizon, a division of A. E. Staley Manufacturing Company of Decatur, Illinois, USA. Using both the know-how of Horizon, which it had acquired in the meantime, as well as experience from research and development work at Henkel KGaA, Diisseldorf,Henkel Corporation built a pilot plant to manufacture alkyl polyglycosides in Crosby, Texas. The pilot plant had a capacity of 5000 t p. a., went on line in 198811989 and was mainly intended to determine process parameters, to optimise product quality under industrial production conditions and to prepare the market for a new class of surfactants. During the period from 1990 to 1992, other companies announced their intention to manufacture alkyl polyglycosides with dodecyMetradecy1chains, including Chemische Werke Hiils, Germany, ICI, Australia, Kao, Japan, and SEPPIC, France. New peaks in the commercial exploitation of alkyl polyglycosides were reached in 1992 with the inauguration of a 25,000 t p. a. production plant for APG' surfactants by Henkel Corporation in the USA and in 1995 with the opening of a second plant of equal capacity by Henkel KGaA in Germany 131. 2. Chemistry

Besides technology, science has always been interested in the synthesis of glycosides since this is a very common reaction in nature. The broad synthesis potential range has recently been reviewed in articles by Schmidt and Toshima and Tatsuta t41 as well as in a number of references cited there. In the synthesis of glycosides, a polyfunctional sugar component is combined with a nucleophile, such as an alcohol, a carbohydrate or a protein. If a selective reaction with one of the hydroxyl groups of the carbohydrate is required, all other functions have to be protected in a first reaction step. In principle, enzymatic or microbial procedures, by virtue of their selectivity, can replace complicated chemical protection and deprotection steps where regioselective formation of glycosides is required. Nevertheless, the use of enzymes in glycoside synthesis has not yet been widely enough investigated and applications are presently limited to the laboratory [51. Owing to problems of avail-

3

History of Alkyl Polyglycosides CH20Ac

AC0*Cl Ac 0

CH,OH

EtOH

OAc

____t

Horn

HO OAr

2 -

1 -

Figure 2. Synthesis of aryl glucosides according to Michael

ability of suitable enzyme systems and the high manufacturing costs anticipated, enzymatic syntheses of alkyl glycosides are not yet ready for upgrading to the industrial level, chemical procedures being preferred. The history of synthetic routes eventually leading to glycosides began in 1870 when M. A. Colley [61 reported the synthesis of “acetochlorhydrose” (1, Figure 2 ) by reaction of dextrose (glucose) with acetyl chloride. Tetra-0-acetyl-glucopyranosyl halides (acetohaloglucoses)were later found to be useful intermediates for the stereoselective synthesis of pure alkyl glucosides. In 1879,Arthur Michael [71 succeeded in preparing well-defined, readily crystallizablearyl glucosides starting from Colley’s intermediate and phenolates (ArO-, Figure 2 ) . The crucial application of Michael’s synthesis to a broad range of carbohydrates and hydroxylic aglycons occurred in 1901, when W. Koenigs and E. Knorr introduced their improved stereoselective glycosidation process [81 (Figure 3 ) .The reaction involves an S,2 substitution at the anomeric carbon and proceeds stereoselectively with inversion of configuration, producing for example the a-glucoside 4 from the p-anomer of the acetobromoglucose intermediate 3. The Koenigs-Knorr synthesis takes place in the presence of silver or mercury promotors. A fundamentally different approach to the synthesis of alkyl glucosides was proposed by Emil Fischer in 1893 [ll. This process is now well known as the “Fischer glycosidation” and comprises an acid-catalyzed reaction of glycoses with alcohols. Any historical account should nevertheless also include A. Gautier’sfirst reported attempt, in 1874,to convert dextrose with anhydrous ethanol CHgAc

CH20H

Br

0 ‘

2. ROH 1. OHe

AcO OAc

3

Ho2!i.5& HO OR

R = alkyl

4 -

Figure 3. Stereoselective synthesis of glycosides according to Koenigs and Knorr

4

Karlheinz Hill

in the presence of hydrochloric acid [91. Due to a misleading elemental analysis, Gautier believed he had obtained a “diglucose”.Fischer later demonstrated [l I that Gautier’s “diglucose”was in fact mainly ethyl glucoside (Figure 4). The structure of ethyl glucoside was defined correctly by Fischer, as may be seen from the historical furanosidic formula (“Fischerprojection”)proposed. In fact, Fischer glycosidation products are complex, mostly equilibrium mixtures of a@-anomers and pyranoside/furanoside isomers which also comprise randomly linked glycoside oligomers [lo]. Accordingly, individual molecular species are not easy to isolate from Fischer reaction mixtures, which has been a serious problem in the past. After some improvement of this synthesis method [ 111, Fischer subsequently adopted the Koenigs-Knorr synthesis for his investigations. Using this process, E. Fischer and B. Helferich in 1911 were the first to report the synthesis of a long-chain alkyl glucoside exhibiting surfactant properties 1121. As early as 1893, Fischer had correctly noticed essential properties of alkyl glycosides, such as their high stability towards oxidation and hydrolysis, especially in strongly alkaline media. Both characteristics are valuable for alkyl polyglycosides in surfactant applications. Research related to the glycosidation reaction is still ongoing and several interesting routes to glycosides have been developed in the recent past. Some of the procedures for the synthesis of glycosides are summarized in Figure 5 [131. In general, chemical glycosidation processes may be divided into processes leading to complex oligomer equilibria in acid-catalysed glycosyl exchange

CYOH H

BOH

O

HO

OH

CbOH

+ EtOH [HCI1 H o s O E t --+

HO

+ HoHO %oEt

OH

Ethyl-P-D-glucO pyranoside

A. Gautier (1874)

“Diglucose”

E. Fischer

“Ethyl glucoside” (historical Fischer projection)

Dextrose

(1893)

Figure 4. Synthesis of glycosides according to Fischer

Ethyl-ctD-gluCopyranoside

V

TROH

Oligomerization equilibria

4

1

1986)

Fluoride

1

Chloride/brornide

I

OR

(Koenigs-Knorr [81, 1901) Conversions in HF + pyridine (Noyori [151, 1984) HX (Szarek [151, 1984) (Defaye 1141, 1991)

I

I

Halogenoses

Figure 5. Summary of methods for the synthesis of glycosides [131

\

Anorners

1 I

Catalysis by strong acids (Fischer [l], 1893d conversibns in HF (Defaye [141,

II

I I

V

@OR

ROH

1

I

CCI,

ClECN NaH

(Schmidt [171, 1980)

"Trichloracetirnidate

Stereospecific processes

Sulfonium group

I

Other derivatives

I

U

/

(direct 1-0-alkylation) [181

Base activation

I Enzyrnatic/rnicrobial procedures [5]

6

Karlheinz Hill

reactions (Fischer glycosidation and reactions in hydrogen fluoride (HF) with unprotected carbohydrate molecules) and kinetically controlled, irreversible, mostly stereospecific substitution reactions on suitably activated carbohydrate substrates. Procedures of the second type may result in the formation of individual species rather than in complex reaction mixtures, especially when combined with protective group techniques. Carbohydrates may be activated at the anomeric carbon by leaving groups, such as halogen atoms 17,8,14,151,the sulfonium group 1161, or the trichloroacetimidategroup 1173, or by base activation before conversion with triflate esters 1181. In the particular case of glycosidations in hydrogen fluoride or in mixtures of hydrogen fluoride and pyridine (pyridinium poly [hydrogen fluoridel) C153, glycosyl fluorides are formed in situ and are smoothly converted into glycosides, for example with alcohols. Hydrogen fluoride was shown to be a strongly activating, nondegrading reaction medium; equilibrium autocondensation (oligomerization) is observed similar to the Fischer process, although the reaction mechanism is probably different 1141. Chemically pure alkyl glycosides are only suitable for very special applications. For example, alkyl glycosides have been used successfully in biochemical research for the crystallization of membrane proteins, such as the three dimensional crystallizationof porin and bacteriorhodopsin in the presence of octyl pD-glucopyranoside (further experiments based on this work lead to the Nobel prize in chemistry for Deisenhofer, Huber and Michel in 1988) [191. During the course of the development of alkyl polyglycosides,stereoselective methods have been used on a laboratory scale to synthesize a variety of model substancesand to study their physicochemical properties 12,201.Owing to their complexity, the instability of intermediates and the amount and critical nature of process wastes, syntheses of the Koenigs-Knorr type and other protective group techniques would create significant technical and economic problems. Fischer-type processes are comparatively less complicated and easier to carry out on a commercial scale and, accordingly, are the preferred method for the production of alkyl polyglycosides on a large scale. References 1. E. Fischer, Ber. 26 (1893)2400 2. DRP 593422, H. Th. Bohme AG (1934) DRP 611055, H. Th. Bohme AG (1935)

3. J. Knaut, G. Kreienfeld, Chimica oggi 11 (1993) 41 4. K. Toshima, K. Tatsuta, Chem. Rev. 93 (1993) 1503 R. R. Schmidt in Comprehensive Organic Synthesis (E. Winterfeldt, ed.), Pergamon Press: Oxford, New York, Seoul, Tokyo, 1991,Vol. 6, p. 33

History of Alkyl Polyglycosides

7

5. F. Wagner, S. Lang, Proceedings 4th World Surfactants Congress,Barcelona, June 1996, Vol. 1, p. 124 K. Krohn, Nachr. Chem. Tech. Lab. 25 (1987) 930 K. G. I. Nilsson, Trends in Biotech. 6 (1988) 256 6. M. A. Colley, Ann. Chim. Phys. IV 21 (1870) 363 7. A. Michael, Am. Chem. J. 1 (1879) 305 8. W. Koenigs, E. Knorr, Ber. 34 (1901) 957 9. A. Gautier, Bull. SOC.Chim. 22 (1874) 145 10. B. Capon, Chem. Rev. 69 (1969) 389 R. J. Ferrier, Fortschr. Chem. Forsch. 14 (1970) 389 11. E. Fischer, L. Beensch, Ber. 27 (1894) 2478 E. Fischer, Ber. 28 (1895) 1145 12. E. Fischer, B. Helferich, Justus Liebigs Ann. Chem. 386 (1911) 68 13. P. Schulz, Chimica oggi 10 (1992) 33 14. J. Defaye, C. Pedersen, Zuckerind. 116 (1991) 271 J. Defaye, E. Wong, C. Pedersen, FR 2,567,891 (1986) 15. M. Hayashi, S. Hashimoto, R. Noyori, Chem. Lett. (1984) 1747

W. A. Szarek, G. Grynkiewicz, B. Doboszewski, G. W. Hay, Chem. Lett. (1984) 1751

16. A. C. West, C. Schuerch, J. Am. Chem. SOC.95 (1973) 1333 17. R. R. Schmidt, J. Michel, Angew. Chem. 92 (1980) 763 R. R. Schmidt, Angew. Chem. 98 (1986) 213 18. R. R. Schmidt, M. Reichrath, Angew. Chem. 91 (1979) 497 19. J. Deisenhofer, H. Michel, Angew. Chem. 101 (1989) 872 M. Clarke, Nature 335 (1988) 752

20. P. Rosevear, T. Van Aken, J. Baxter, S. Ferguson-Miller, Biochemistry 19 (1980) 4108

D. E. Koeltzow, A. D. Urfer, J. Amer. Oil Chem. SOC.61 (1984) 1651 A. J. J. Straathof, H. van Bekkum, A. P. G. Kieboom, Starch/Starke 40 (1988) 229, Starch/Starke 40 (1988) 438 J. Thiem, Th. Bocker, Tenside Surf. Det. 26 (1989) 318

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

2. Technology and Production of Alkyl Polyglycosides Rainer Eskuchen and Michael Nitsche

As described in Chapter 1, there are several preparative methods which lead to alkyl glycosides or alkyl polyglycoside mixtures. The various syntheses range from stereospecific synthesis routes using protective groups, which give defined compounds with high selectivity, to nonselective processes which lead to complex isomer and oligomer mixtures. Any production process suitable for use on an industrial scale must satisfy several criteria. The ability to produce products with suitable performance properties and process economy are the most important. There are other aspects, such as minimizing side reactions or waste and emissions. The technology used should have a flexibility which allows product properties and quality features to be adapted to market requirements. So far as the industrial production of alkyl polyglycosides is concerned, processes based on the Fischer synthesis have been successfully adopted. Their development began about twenty years ago and has significantly accelerated in the past ten years. Development work over this period has enabled the efficiency of this synthesis route to be increased to a level where it has finally become attractive for industrial application. Optimization work, particularly in the use of long-chain alcohols, such as dodecanol/tetradecanol (C12,14-OH), has resulted in distinct improvements in product quality and process economy. Modern production plants built on the basis of the Fischer synthesis are the embodiment of low-waste, virtually emission-free technologies. Another advantage of the Fischer synthesis is that the average degree of polymerization of the products can be precisely controlled over a wide range. Relevant performance properties, for example hydrophilicity/water solubility, can thus be adapted to meet requirements. Additionally the raw material base is no longer confined to water-free glucose 11-31. 1. Raw materials for the manufacture of alkyl polyglycosides 1.1 Fatty alcohols

Fatty alcohols can be obtained either from petrochemical sources (synthetic fatty alcohols) or from natural, renewable resources, such as fats and oils (natural fatty alcohols). Fatty alcohol blends are used in the alkyl polyglycoside synthesis to build up the hydrophobic part of the molecule. The natural fatty alcohols are obtained after transesterification and fractionation of fats and oils

Rainer Eskuchen and Michael Nitsche

10

(triglycerides),leading to the corresponding fatty acid methyl esters, and subsequent hydrogenation. Depending on the desired alkyl chain length of the fatty alcohol, the main feedstocks are oils and fats of the following composition: coconut or palm kernel oil for the C,,,,, range and tallow, palm or rapeseed oil for the C,,,,, fatty alcohols. 1.2 Carbohydrate source

The hydrophilic part of the alkyl polyglycoside molecule is derived from a carbohydrate. Based on starch from corn, wheat or potatoes, both polymeric and monomeric carbohydrates are suitable as raw materials for the production of alkyl polyglycosides. Polymeric carbohydrates include, for example, starch or glucose syrups with low degradation levels while monomeric carbohydrates can be any of the various forms in which glucose is available, for example waterfree glucose, glucose monohydrate (dextrose)or highly degraded glucose syrup. Raw material choice influences not only raw material costs, but also production costs. Generally speaking, raw material costs increase in the order starddglucose syrup/glucose monohydrate/water-free glucose whereas plant equipment requirements and hence production costs decrease in the same order (Figure 1).

-

Decreasing demands of the alkyl polyglycoside plant equipment Increasing raw material prices

~ 1~ ~

dextrose syrup

dextrose syrup

Two step process 1. Butanolysis

monohydrate

One step process

Starch or syrup/butanol

Acetalization Glucose/fatty alcohol

2. Transacetalization Butylglycoside/fatty alcohol

1 LI

Alkyl polyglycosides

IA

Figure 1. Carbohydrate sources for industrial-scale alkyl polyglycoside synthesis (DE = dextrose equivalent)

11

Technology and Production of Alkyl Polyglycosides

2. Degree of polymerization Through the polyfunctionality of the carbohydrate partner, the conditions of the acid-catalyzed Fischer reaction yield an oligomer mixture in which on average more than one glycose unit is attached to an alcohol mblecule. The average number of glycose units linked to an alcohol group is described as the (average) degree of polymerization (DP).Figure 2 shows the distribution for an alkyl polyglycoside with DP = 1.3. In this mixture, the concentration of the individual oligomers (mono-, di-, tri-, . . .-, glycoside) is largely dependent on the ratio of glucose to alcohol in the reaction mixture. The average degree of polymerization (DP) is an important characteristic with regard to the physical chemistry and applications of alkyl polyglycosides. In an equilibrium distribution, the DP-for a given alkyl chain length-correlates well with basic product properties, such as polarity, solubility, etc. In principle, this oligomer distribution can be described by a mathematical model. P. M. McCurry [41 showed that a model developed by P. J. Flory t51 for describing the oligomer distribution of products based on polyfunctional monomers can also be applied to alkyl polyglycosides. This modified version of the Flory distribution describes alkyl polyglycosides as a mixture of statistically distributed oligomers. The content

[Wt.-%l 100

r

OH

1

50 DP- 1

I

I

DP1

DP2

DP3

DP4

DP5

Figure 2. Typical distribution of dodecyl glycoside oligomers in a DP= 1.3 mixture (R = dodecyi)

12

Rainer Eskuchen and Michael Nitsche

of individual species in the oligomer mixture decreases with increasing degree of polymerization. The oligomer distribution obtained by this mathematical model accords well with analytical results (see Chapter 3). In simple terms, the average degree of polymerization (DP) of alkyl polyglycoside mixtures can be calculated from the mole percent piof the respective oligomeric species "i"in the glycoside mixture (Figure 2). 3. Synthesis processes for the production of alkyl polyglycosides

Basically, all processes for the reaction of carbohydrates to alkyl polyglycosides by the Fischer synthesis can be attributed to two process variants, namely direct synthesis and the transacetalization process. In either case, the reaction can be carried out in batches or continuously. Direct synthesis is simpler from the equipment point of view [6-81. In this case, the carbohydratereacts directly with the fatty alcohol to form the required long-chain alkyl polyglycoside. The carbohydrate used is often dried before the actual reaction (for example to remove the crystal-water in case of glucose monohydrate = dextrose).This drying step minimizes side reactions which take place in the presence of water. In the direct synthesis, monomeric solid glucose types are used as fineparticle solids. Since the reaction is a heterogeneous solid/liquid reaction, the solid has to be thoroughly suspended in the alcohol. Highly degraded glucose syrup (DE> 96; DE = dextrose equivalents) can react in a modified direct synthesis. The use of a second solvent and/or emulsifiers (for example alkyl polyglycoside)provides for a stable fine-droplet dispersion between alcohol and glucose syrup "3,101. The two-stage transacetalization process involves more equipment than the direct synthesis. In the first stage, the carbohydrate reacts with a short-chain alcohol (for example n-butanol or propylene glycol) and optionally depolymerizes. In the second stage, the short-chain alkyl glycoside is transacetalized with a relatively long-chain alcohol (C,,,,,-OH) to form the required alkyl polyglycoside. If the molar ratios of carbohydrate to alcohol are identical, the oligomer distribution obtained in the transacetalization process is basically the same as in the direct synthesis. The transacetalization process is applied if oligo- and polyglycoses (for example starch, syrups with a low DE value) are used [111. The necessary depolymerization of these starting materials requires temperatures of > 140"C. Depending on the alcohol used, this can create correspondingly higher pressures which impose more stringent demands on equipment and can lead to higher plant cost.

13

Technologyand Production of Alkyl Polyglycosides

Generally, and given the same capacity, the transacetalization process results in higher plant cost than the direct synthesis. Besides the two reaction stages, additional storage facilities and, optionally, working-up facilities for the shortchain alcohol have to be provided. Alkyl polyglycosides have to be subjected to additional or more elaborate refining on account of specific impurities in the starch (for example proteins). In a simplified transacetalization process, syrups with a high glucose content (DE > 960/0)or solid glucose types can react with short-chain alcohols under normal pressure 112-161. Continues processes have been developed on this basis [141. Figure 3 shows both synthesis routes for alkyl polyglycosides.

. HO

Starch

Butyl oligoglycosides intermediate

Dodecanol [Acid catalyst]

DP-1

-0

Dodecyl polyglycosides

1

CH,OH Butanol [Acid catalyst]

HO* OH OH Glucose

Dodecanol [Acid catalyst]

Figure 3. Alkyl polyglycoside surfactants-industrial synthesis pathways

\OH

14

Rainer Eskuchen and Michael Nitsche

4. Requirements for the industrial production of water-soluble alkyl polyglycosides

The requirements for or rather the design of alkyl polyglycoside production plants based on the Fischer synthesis are critically determined by the carbohydrate types used and by the chain length of the alcohol used. It is intended here to describe first the production of water-soluble alkyl polyglycosides on the basis of octanol/decanol (C,,,,-OH) and dodecanol/tetradecanol (C,,,,,-OH). Alkyl polyglycosides which, for a given DP, are insoluble in water on account of the alcohol used (number of C atoms in the alkyl chain 2 16)are dealt with separately (see 5. in this chapter). Under the conditions of the acid-catalyzed syntheses of alkyl polyglycoside, secondary products, such as polydextrose [17,181, ethers and colored impurities, are formed. Polydextroses are substances of undefined structure which are formed in the course of the synthesis through the polymerization of glycoses. The type and concentration of the substancesformed by secondary reactions are dependent on process parameters, such as temperature, pressure, reaction time, catalyst, etc. One of the problems addressed by development work on industrial alkyl polyglycoside production over recent years was to minimize this synthesis-related formation of secondary products. Generally, the production of alkyl polyglycosides based on short-chain alcohols (C,,,,-OH) and with a low DP (largealcohol excess)presents the fewest problems. Fewer secondary products are formed with the increasing excess of alcohol in the reaction stage. The thermal stress and formation of pyrolysis products during removal of the excess alcohol are reduced. The Fischer glycosidation may be described as a process in which, in a first step, the dextrose reacts relatively quickly and an oligomer equilibrium is reached. This step is followed by slow degradation of the alkyl polyglycoside. In the course of the degradation, which consists of dealkylation and polymerization steps, the thermodynamically more stable polydextrose is formed substantially irreversibly in increasing concentrations. Reaction mixtures which have exceeded an optimal reaction time may be described as over-reacted. If the reaction is terminated too early, the resulting reaction mixture contains a significant amount of residual dextrose. The loss of alkyl polyglycoside active substance in the reaction mixture correlates well with the formation of polydextrose, the reaction mixture in the case of over-reacted systems gradually becoming heterogeneous again through precipitating polydextrose. Accordingly, product quality and product yield are critically influenced by the time at which the reaction is terminated. Starting with solid dextrose, alkyl polyglycosides low in secondary products are obtained, providing other polar constituents (polydextrose)are filtered off to-

15

Technology and Production of Alkyl Polyglycosides

gether with the remaining carbohydrate from a reaction mixture which has not fully reacted [19,201. In an optimized process, the concentration of secondary products formed by etherification remains relatively low (depending on the reaction temperature and time, the type and concentration of catalyst, etc.).Figure 4 shows the typical course of a direct reaction of dextrose and fatty alcohol (C,,,,,-OH). In the Fischer glycosidation, the reaction parameters temperature and pressure are closely related. To produce an alkyl polyglycoside low in secondary products, pressure and temperature have to be adapted to one another and carefully controlled. Low reaction temperatures (<100“C)in the acetalization lead to alkyl polyglycosides low in secondary products. However, low temperatures result in relatively long reaction times (depending on the chain length of the alcohol) and low specific reactor efficiencies.Relatively high reaction temperatures (>100“C, typically 110-120“C)can lead to changes in color of the carbohydrates. By removing the lower-boiling reaction products (water in the direct synthesis, short-chain alcohols in the transacetalization process) from the reaction mixture, the acetalization equilibrium is shifted to the product side. If a relatively large amount of water is produced per unit of time, for example by high reaction temperatures, provision has to be made for the effective removal of this water

Concentration Over-reacted mixtures

7

E of alkyl glycoside oligomers

“Polydextrose” Etherification by products

Biphasic conversion

Slow irreversible polymerization/dealkylation

Rapid equilibration

Figure 4. Mass balance of the glycosidation process

7

Tim0 *,,,VG

16

Rainer Eskuchen and Michael Nitsche

from the reaction mixture. This minimizes secondary reactions (particularlythe formation of polydextrose) which take place in the presence of water. The evaporation efficiency of a reaction stage depends not only on pressure, but also on temperature and on the design of the reactor (stirrer, heat-exchange area, evaporation area, etc.). Typical reaction pressures in the transacetalization and direct synthesis variants are between 20 and 100 mbar. Another important optimization factor is the development of selective catalysts for the glycosidation process so that for example the formation of polydextrose and etherification reactions can be suppressed. As already mentioned, acetalization or transacetalization in the Fischer synthesis is catalyzed by acids. In principle, any acids with sufficient strength are suitable for this purpose, such as sulfuric acid, para-toluene- and alkylbenzene sulfonic acid and sulfo succinic acid. The reaction rate is dependent on the acidity and the concentration of the acid in the alcohol. Secondary reactions which are also catalyzed by acids, such as the formation of polydextrose, mainly take place in the polar phase (tracesof water) of the reaction mixture and can be reduced by using hydrophobic acids such as alkylbenzene sulfonic acids which, through the length of their alkyl chain, mainly dissolve in the less polar phase of the reaction mixtures [21-241. After the reaction, the acidic catalyst is neutralized by a suitable base, for example sodium hydroxide, magnesium oxide. The neutralized reaction mixture is a yellowish solution containing 50 to 80 Oo/ fatty alcohol. The high fatty alcohol content results from the molar ratios of carbohydrate to fatty alcohol. This ratio is adjusted to obtain a specific DP for the technical alkyl polyglycosides and is generally between 1:2 and 1:6. Several common technical products are specified and listed under 6. in this chapter. The excess fatty alcohol is removed by vacuum distillation. Important boundary conditions include: - Residual fatty alcohol content in the product must be <1% because otherwise solubility and odor are adversely affected. - To minimize the formation of unwanted pyrolysis products or discoloring components, thermal stressing and residence time of the target product must be kept as low as possible in dependence upon the chain length of the alcohol. - No monoglycoside should enter the distillate because the distillate is recycled in the reaction as pure fatty alcohol. In case of dodecanolhetradecanol these requirements for the removal of excess fatty alcohol are largely satisfied by multistage distillation. It is important to note that there is a distinct increase in viscosity with decreasing fatty alcohol content. This significantly impairs heat and mass transport in the last distillation stage. Accordingly, thin-layer or short-path evaporators are preferred [25,261. In these evaporators, the mechanically moved film provides for high

17

Technology and Production of Alkyl Polyglycosides

specific evaporation efficiency and a short product residence time and at the same time a good vacuum. The end product after distillation is an almost pure alkyl polyglycoside which accumulates as a solid with a melting range of 70 to 150 "C. Figure 5 summarizes the main process steps for the synthesis of alkyl polyglycosides. One or two alcohol recycle streams accumulate in alkyl polyglycoside production depending on the manufacturing process used: excess fatty alcohol and-in case of the transacetalization process-the short-chain alcohol which is almost completely recovered. These alcohols may be reused in subsequent reactions. The need for purifying or the frequency with which purifying steps have to be carried out depends upon the impurities accumulated in the alcohol. This is largely dependent upon the quality of the preceding process steps (for example reaction, alcohol removal). After removal of the fatty alcohol, the alkyl polyglycoside active substance is directly dissolved in water so that a highly viscous 50 to 70% alkyl polyglycoside paste is formed. In subsequent refining steps, this paste is worked up into a product of satisfactory quality in accordance with performance-related requirements. These refining steps may comprise bleaching of the product, the

Starch or dextrose syrup

1

I

4 Butanolysis

'

Anhydrous glucose or glucosemonohydrate (dextrose)

-1

Transacetaiization

I

Butanol

-

Fatty alcohol

alcohol

Butanol/water

Water

Neutralization

Water

-1

Dissolution

I

Bleaching

+

I I

Aqueous, refined alkyl polyglycosides

Figure 5. Simplified flow diagram for the production of alkyl polyglycosides based on different carbohydrate sources-direct synthesis and transacetalization

18

Rainer Eskuchen and Michael Nitsche

FOH Dextrose Catalyst Base

20-5096 APG 80-90%APG 50-80% FOH 10-20%FOH

Figure 6. Typical industrial-scale glycosidation process for

APG melt

k1% FOH) c12/14

APG (FOH =fatty

alcohol) adjustment of product characteristics, such as pH value and active substance content, and microbial stabilization. In the patent literature, there are many examples of reductive [271 and oxidative bleaching [28-321 and of two-stage processes of oxidative bleaching and reductive stabilization 1331.The effort and hence the cost involved in these process steps to obtain certain quality features, such as color, depend on performance requirements, on the starting materials, the DP required and the quality of the process steps. Figure 6 illustrates an industrial production process for long-chain alkyl polyglycosides (C,,,,, APG) via direct synthesis. 5. Production of water-insoluble alkyl polyglycosides

If fatty alcohols containing 16 or more carbon atoms per molecule are used in the synthesis of alkyl polyglycosides,the products obtained are soluble in water in only very low concentrations for typical DP of 1.2 to 2. They are referred to in the following text as water-insoluble alkyl polyglycosides. In these alkyl polyglycoside types, the nonpolar character predominates due to the longchain alkyl group. These cannot be used as surfactants but, instead, are mainly used as emulsifiers in cosmetic formulations [34,351. The observations of the reaction of glucose with dodecanol/tetradecanol largely apply to the synthesis of water-insoluble alkyl polyglycosides, such as

Technology and Production of Alkyl Polyglycosides

19

hexadecyl/octadecyl polyglycosides. The acid-catalyzed reaction is carried out at similar temperatures, pressures and molar ratios between the starting materials [341. However, refining and bleaching of the product as an aqueous paste is more difficult due to the low solubility of these products. It is all the more important to produce products that are low in side products and light in color directly after the reaction step, thus avoiding further treatment. The most important unwanted secondary product is polydextrose. It is yellow-brown and thus significantly deteriorates color. In addition, the presence of polydextrose in high concentrations make it difficult to concentrate the reaction mixture by distillation because the polydextrose tends to decompose very rapidly as temperature is increased. This can ultimately also impair the performance properties. Since the rate at which polydextrose is formed increases considerably towards the end of the reaction, the reaction is prematurely terminated at a glucose conversion of around 80% by reducing the temperature and neutralizing the catalyst. To guarantee uniform and reproducible product quality, on-line analysis is used to follow the conversion precisely. At the moment of termination, the unreacted glucose is present in the form of a suspended solid which can readily be removed by subsequent filtration. After removal of the glucose, the product contains around 1-2010 of polydextrose which is emulsified in the form of very fine droplets. By choosing the right filter aid, the polydextrose can be completely removed in a second filtration step [351. A substantially glycose- and polydextrose-free product containing 15 to 30% of long-chain (C,,,,,) alkyl polyglycosides and 85 to 70% of fatty alcohol

fatty Anhydrous alcohol glucose

c16/18

-1-

I

I

Acetalization (80%)

~

.S;Fnic

-

acid

Glucose/polydextrose

__c

Fatty alcohol (partly)

Figure 7. Flow diagram for the synthesis of C, alkyl polyglycoside/C,,,,, fatty alcoho1 (Emulgade PL 68/50)

Glucose/polydextrose

&/18

alkyl polyglycoside/ fatty alcohol

Rainer Eskuchen and Michael Nitsche

20

Table 1. Industrially manufactured APG surfactants Alkyl chain length Short-chain

c8/10

c911

Medium-/ long-chain')

ClU14 dl

Long-chain

16/18

Special products

Cs14: mainly composed of c8-P c l O - ?

c,,-, c,,-, alkyl polyglycosides

DP

Brand namesa)

1.5 1.5 1.7 1.5 1.7

Glucopon 215 CSUP Glucopon 220 UP Glucopon 225 DK Agrimulb) PG 2076 Agrimul PG 2067

1.6 1.6

APG 325 CS Agrimul PG 2069

1.4 1.4 1.4 1.4 1.6 1.6

Glucopon 600 CSUP Glucopon 600 UP Agrimul PG 2062 ~1antacare~)1200 UP, ~1antaren~)1200 UP Glucopon 625 UP Glucopon 625 FE Emulgade PL 68/50 Glucopon 425 Glucopon 600 EC Glucopon 650 EC Agrimul PG 2072 Plantacare 2000 UP, Plantaren 2000 UP Plantacare 818 UP

a) APG@, Agrimul? Emulgade@,Glucopon@, Plantacare@and Plantaren@are registered trademarks of the Henkel Group for alkyl polyglycoside products. b) Agrimul = agricultural product line c) In the alkyl polyglycoside literature both terms "medium-chain" and "longchain" are used for C12,14 alkyl polyglycosides. d) Contains 1-6% hexadecyl (c16) polyglycoside depending on specification e) Plantacare, Plantaren = cosmetic quality product line

(C,,,,,-OH) is obtained by this process. Since the product has an elevated melting point, it is normally marketed as a solid in the form of flakes or pellets. The high content of long-chain alcohol is acceptable because many cosmetic emulsions contain significant concentrations of the same alcohol. Accordingly, the alkyl polyglycoside may be directly used as an alkyl polyglycoside/fatty alcohol compound.

Technology and Production of Alkyl Polyglycosides

21

A fairly recent type of water-insoluble alkyl polyglycosides contains approximately 50 010 of alkyl polyglycoside, 50 Yo fatty alcohol. In this case part of the fatty alcohol is removed by vacuum distillation [361,with temperatures and residence time kept as low as possible to suppress thermal decomposition (Figure 7). This concentrated product type considerably extends the range of application for water-insoluble alkyl polyglycosides. 6. Examples of technical products Today alkyl polyglycoside products are manufactured for various applications using the technology described above. Table 1lists some of the APG surfactants, which are currently produced by Henkel. References

1. P. T. Schulz, Proc. BACS Symp., Chemspec Eur. 91, Amsterdam, 1991, p. 33 I? T. Schulz, Chimica oggi 10 (1992)33 2. M. Biermann, K. Schmid, P. T. Schulz, Starch/Starke 45 (1993) 281 3. K. Hill, M. Weuthen, Spektrum der Wissenschaft, June 1994, 113 4. P. M. McCurry, Henkel Corporation, unpublished results 5. P. J. Flory, J. Am. Chem. SOC.74 (1952)2718 6. EP 0437460 B1, Henkel(1988) 7. El' 0495174, Huls (1991) 8. El' 0617045 A2,Akzo (1994) 9. EP 0448799, Huls (1990) 10. WP 94104544, BASF (1992) 11. EP 0357969 B1, Henkel (1988) 12. EP 0301298 B1, Henkel (1987) 13. El' 0482325, Huls (1990) 14. W. Ruback, S. Schmidt in Carbohydrates as Organic Raw Materials I11 (H. van Bekkum, ed.), VCH Verlagsgesellschaft, Weinheim, 1996, p. 231 EP 0514627, Huls (1991) 15. El' 0099183, Staley (1982) 16. WO 93/10133, Henkel (1991) 17. Y. Z. Lai, F. Shafizadeh, Carbohydr. Res. 38 (1970) 177 18. G. R. Ponder, G. N. Richards, Carbohydr. Res. 208 (1974) 93 19. WO 90/06933, Henkel(1990) 20. EP 0492397, Kao (1990) 21. EP 0132043, Procter & Gamble (1987) 22. WO 90/07516, Henkel (1990) 23. US 5478930, Henkel (1993)

22

Rainer Eskuchen and Michael Nitsche

24. EP 0132046, Procter &I Gamble (1983) 25. DE-OS 3833780, Henkel (1988) 26. DE-OS 3932173, Henkel(1989) 27. EP-A 0388857, Kao (1989) 28. EP-A 0306650, Hiils (1989) 29. EP 389753, Hiils (1990) 30. WO 91/09043, Henkel(1984) 31. WO 93113113, Henkel (1991) 32. US 5432275, Henkel (1994) 33. EP-A 0387913, Kao (1990) 34. K. Hill in Carbohydrates as Organic Raw Materials (G.Descotes, ed.),VCH Verlagsgesellschaft, Weinheim, 1993, p. 163 35. M. Weuthen, R. Kawa, K. Hill, A. Ansmann, Fat Sci. Technol. 97 (1995)209 36. DE-P 19542572.3, Henkel (1995)

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

3. Analysis of Alkyl Polyglycosides and Determination in Consumer Products and Environmental Matrices Heinrich Waldhoff, Judith Scherler, Michael Schmitt, and Jan R.Varvi1

Over recent years, alkyl polyglycosides have developed into commercial surfactants which are produced on a large scale and which are now an ingredient in a wide range of technical and consumer products. To deal with the analytical tasks arising out of this evolution, specific methods have been developed for alkyl polyglycoside raw material characterization and quality control, for alkyl polyglycoside determination in formulated products and for trace analysis in environmental matrices. This chapter provides an overview of state of art alkyl polyglycoside analysis in these fields with emphasis on those analytical methods which have proven to be reliable in routine laboratory practice [ l l . Commercial alkyl polyglycosides are complex mixtures of species which differ mainly in the degree of polymerization (a typical distribution is given in Table 1) and in the length of the alkyl chains (see Chapter 2). Alkyl monoglycosides are the main group of components with a content of more than 500/0, followed by the diglycosides and higher oligomers up to heptaglycosides. Small amounts of more highly glycosidated species are also present. Species with a degree of glycosidation above 5 are not normally determined in routine analysis because the amounts involved are too small. The analytical tasks to be performed for the characterization of commercial alkyl polyglycosides are as follows: 1. Determination of the type, amount and distribution of alkyl mono- and oligoglycosides and the alkyl chain length and distribution of the fatty alcohol Table 1. Composition of two alkyl polyglycoside surfactants

Substances Monoglycosides Dtglycosides Tnglycostdes Tetraglycosides

Pentaglycosides Hexaglycosides Heptagtycosides

Sample 1

Sample 2

65%

51% 19% 13% 10% 4% 2% 1%

19% 9% 5% 2% 0% (<0.5%) 0%(<0.5%)

24

Heinrich Waldhoff,Judith Scherler,Michael Schmitt,and Jan R.Varvi1

bound in the product. The average degree of polymerization (DP) is calculated from these data. 2. Qualitative and quantitative analysis of minor components, such as traces of residual fatty alcohol and glucose. Special analyses, such as color, viscosity, ash content, dry residue, foam behavior, etc., have to be carried out for quality control purposes. The data are usually provided by the alkyl polyglycoside manufacturers in the technical data sheets. As the corresponding methods are not specific for alkyl polyglycosides, they will not be discussed here. 1. Analytical characterization of main and trace components in alkyl polyglycosides

The most important analytical techniques routinely used for the characterization of main and trace components in commercial alkyl polyglycosides are high performance liquid chromatography (HPLC) and gas chromatography (GC). 1.1 Alkyl polyglycoside determination by GC

The GC technique which has proven to be particularly suitable for the analysis of alkyl mono- and oligoglycosides is high temperature gas chromatography (HTGC). HTGC uses temperatures of up to 400 "C which enables oligomeric alkyl polyglycosides up to the very high boiling heptaglycosides to be analyzed. The hydroxyl groups in alkyl polyglycosides have to be converted into silyl ethers before analysis to prevent sample decomposition. The best silylation results have been obtained using a mixture of 2 ml of TriSil-Z (N-trimethylsilylimidazolein pyridine) and 0.4 ml of MSTA (N-methylN-trimethylsilyltrifluoroacetamide)as the silylating agent for about 30 mg of sample. The reaction is carried out at 80 "C; reaction time 0.5 h. A solution of the resulting silyl ether mixture in n-heptane is then injected into the system. A typical high temperature gas chromatogramof a commercial alkyl polyglycoside sample is shown in Figure 1. The first group of peaks relates to the alkyl monoglycosides. They are separated according to carbon chain length and, in addition, into furanosides and pyranosides and a-and P-anomers. The second group belongs to the alkyl diglycosides followed by higher oligomers which are superimposed by the polyglycoses-signals.The high separation efficiencyof HTGC is demonstrated in Figure 2 which shows a magnified segment of an alkyl polyglycoside HTGC chromatogram. Nearly all the species in this segment are baseline-separated and can therefore be clearly identified and quantified. Quantification is carried out by the

25

Analysis of Alkyl Polyglycosides Response [mVl 19.5 18.0 16.5 15.0 13.5

12.0 10.5

9.0

I

I

I

I

I

I

I

5

10

15

20

25

30

a C12,14,16 furanosides b C, monoglycosides c C, monoglycosides d C, monoglycosides e Diglycosides f Triglycosides g Tetraglycosides h Pentaglycosides

i Hexaglycosides j Heptaglycosides

Detector: FID 420'C Detector gas flow: Hydrogen 30 ml/min Air 300 ml/min Temp. program: 400°C 70'C 4 min isotherm 12 min 10 'C/min isotherm

I

35 40 Run time [rnin]

CoIumn: Duran glas capillary, 10 m x 0.53 mm ID, SlMDlS Injector: On column Inj. vol.: 1 1 Carrier gas: Hydrogen 20 rnl/min

Figure 1. HTGC chromatogram of long chain alkyl polyglycoside

(C12/14

APG)

internal standard method using pentadecanol as internal standard. The response factors and retention times are determined using the commercially available octyl-, decyl-, and dodecyl-p-D-glucopyranoside and dodecyl-p-D-maltoside for calibration. Components for which no calibration substance is available are quantified using the response factor of the nearest calibration substance of the same type. All alkyl oligoglycosides are quantified with the response factor of dodecyl-p-D-maltoside. A complete set of components identified and quantified by HTGC in a typical alkyl polyglycoside sample is shown in Table 2. All essential parameters for the characterization of alkyl polyglycoside samples, such as alkyl chain length and composition of the fatty alcohols used in the synthesis, the type and quantity of mono- and oligoglycosides present in the product, can be calculated from these data. The greatest advantage of alkyl polyglycoside analysis by high temperature gas chromatography is the high resolution which enables virtually all relevant components to be characterized.

26

Heinrich Waldhoff,Judith Scherler,Michael Schmitt,and Jan R.Varvi1

Response ImVl 24 22 20

il; I

7

1

gl

18 -

16-

e 1

I

14 -

c

12-

a 1 0 - L I 14 15

h

f

d

I.

16

17

18

19

1

a b

c d

e f g h i j k

I

furanoside a-glucopyranoside c 8 p-glucopyranoside Clo furanoside Clo a-glucopyranoside Clo p-glucopyranoside C12 furanoside CI2 a-glucopyranoside C12 P-glucopyranoside CI4 furanoside C14 a-glucopyranoside CI4 p-glucopyranoside c8 c8

Run time [minl

Figure 2. Segment of C W IAPG ~ HTGC chromatogram

A particularly important parameter for characterizing alkyl polyglycoside surfactants is the DP (average degree of polymerization) which describes the average number of glycose units in a specific alkyl polyglycoside product (see Chapter 2). The ratio can be calculated on the basis of the concentration of all alkyl glycosides present in significant amounts; these data are acquired by Table 2. Components in a CWMAPG sample determined by HTGC ~~

~

Substance Pentadecanol C8 furanosides C a-glucopyranoside C B-glucopyranoside Clo furanosides C a-glucopyranoside C p-glucopyranoside

furanosides a-glucopyranoside C 12 P-glucopyranoside Diglycosides Triglycosides Tetraglycosides Pentaglycosides Hexaglycosides Heptaglycosides C12 C 12

Weight-%

Area-%

-

-

0.5 8.7 4.8 0.5 9.3 4.5 0.1 0.4 0.2 12.2 7.2 5.3 4.1 2.0 1.o

0.8 13.9 7.7 0.9 15.0 7.1 0.1 0.7 0.4 19.6 11.5 8.5 6.6 3.2 1.6

27

Analysis of Alkyl Polyglycosides

HTGC. Another method of calculating DP uses the total amount of alkyl monoglycosides and a Flory algorithm [21. 1.2 Alkyl polyglycoside characterization by HPLC

Alkyl polyglycoside characterization by HPLC is routinely performed using an isocratic reversed-phase system. In most cases, no particular sample preparation is necessary; after dissolution in the eluent, the sample solution is filtered and directly injected into the system. A typical chromatogram and the chromatographic conditions are shown in Figure 3. The retention corresponds to the lipophilicity of the substances separated. The individual species are identified and quantified by the external standard method using commercially available alkyl glycosides for calibration (see 1.1 in this chapter). The alkyl monoglycosides are separated cleanly enough to allow sufficiently accurate quantification. Detailed determination of individual oligoglycosides and separation into 01 and anomers, pyranosides and furanosides are only possible with a more polar mobile phase that requires tediously long analyses times [31. The analysis of alkyl glycosides in commercial alkyl polyglycoside products by HPLC provides good results for analytical tasks which do not require high resolution of a broad spectrum of components. Typical applications include raw material identification, comparative alkyl polyglycoside analysis, quantifications and calculations solely on the basis of the alkyl monoglycoside contents.

34 -

C

e

30 -

I

26 22

b

-

a

-

18 -

14 -

Figure 3. HPLC chromatogram of C I U IAPG ~ sample

Column: RP-8 Detection: Refractive index Eluent: Acetonitrile/water Flow: 1 ml/min a b c d e f g

Polydextrose C12 oligoglycosides C12 monoglycoside CI4 oligoglycosides C14 monoglycoside CI6 oligoglycosides C16 monoglycoside

28

Heinrich Waldhoff,Judith Scherler,Michael Schmitt, and Jan R.Varvi1

Response [mVl Column: Nova-Pack c18

100

Eluent: Acetonitrile/water/methanol 66 24 10

80 60

Flow: 1 ml/min

40 20

Detection: Refractive index

0

0

5

10

15

20

25

30 35 Run time [minl

Figure 4. Fatty alcohol in a Cs,lo APG sample-determination by HPLC

1.3 Determination of fatty alcohol Alkyl polyglycoside surfactants c o n t a i n small amounts (
Column: Fused silica capillay DB5, 15 m x 0.32 mm ID, 0.1 pm coating Carrier gas: Helium Pre pressure: 0.8 bar

80

60

Split: 20 ml/min 40

Inj. temp.: 280'C Inj. vol.: 1 pi

20

Detector: FID, 330'C I

0

10

a c 8 fatty alcohol b Clo fatty alcohol c C12 fatty alcohol

20

30

40 50 R~~ tirne [mini

d CI4 fatty alcohol e Pentadecanol

Detector gas flow: Hydrogen 30 ml/min air 300 ml/min Temp. program: 45'C 3 min isotherm 5'C/min

300'C 3 min isotherm

Figure 5. Fatty alcohol in alkyl polyglycoside products-determination by GC

29

Analysis of Alkyl Polyglycosides

HPLC system. The first very broad and intensive peak belongs to the shorter chain alkyl mono- and oligoglycosides. The alcohols are eluted thereafter according to their alkyl chain length. Quantification is carried out by the internal standard method using undecanol (Cs/l~ alkyl polyglycosides) and pentadecanol (CI2ll4alkyl polyglycosides) for calibration. For most commercial alkyl polyglycoside types, determination of residual fatty alcohol by HPLC provides satisfactory results. For some types, however, the separation of alkyl glycosides and Ca fatty alcohol is not sufficient. For these types, analysis by GC gives better results by virtue of the higher separation efficiency of this technique. The samples have to be silylated before analysis. A typical GC chromatogram and the conditions applied are shown in Figure 5. The fatty alcohol peaks are clearly separated from the rest of the components present. Quantification is based on the internal standard method using pentadecanol for calibration. Both HPLC and GC have proven to be reliable in routine analysis for the determination of residual fatty alcohol in alkyl polyglycosides. The particular method selected depends on the problem to be solved and on the experience and equipment available in the laboratory where the analysis is to be performed. 1.4 Determination of glucose

The determination of residual glucose in commercial alkyl polyglycosides is carried out by high temperature gas chromatography (HTGC) under the conditions already described for the characterization of alkyl mono- and oligoglycosides.Besides the main component peaks, there are additional peaks attribResponse [mVl

25.0

a b c d e

20.0

Pentadecanol Glucose C, fatty alcohol Glucose C,, fatty alcohol

15.0

10.0

3

6

9

12

15

18

21

Run time [minl

Figure G. Glucose determination in a C16118alkyl polyglycoside sampleHTGC chromatogram

30

Heinrich Waldhoff,Judith Scherler,Michael Schmitt,and JanR-Varvil

utable to glucose in the chromatogram of the silylated sample. This segment of a typical chromatogram is shown in Figure 6. Quantification is carried out by the internal standard method using pentadecanol for calibration. An alternative method routinely used for the analysis of glucose in alkyl polyglycosides is the determination with commercially available enzyme-based test kits (for example Boehringer, Cat. No. 716251). 2. Alkyl polyglycoside analysis in formulated products

Alkyl polyglycosides are used as ingredients in a broad range of consumer products, such as cosmetic formulations, dishwashing detergents, all-purpose cleaners, laundry detergents, and specialties.The analytical tasks in this area are to ascertain whether or not alkyl polyglycoside is present in a product and, if so, how much and which type. The analytical techniques most commonly used to perform these tasks are thin layer chromatography and HPLC. 2.1 Alkyl polyglycoside analysis by thin layer chromatography (TLC)

A normal-phase TLC system is used for qualitative and quantitative determination of alkyl polyglycosides. The alkyl polyglycoside type is identified by reversed-phase TLC. The normal-phase system is shown in Figure 7. In most cases, the analysis of samples by TLC does not entail any particular sample preparation. 10 ml of an ethanolic solution (0.5-1Vo) is applied to the TLC plate in the form of 1 cm lines together with solutions of alkyl polyglycoside calibration substances. The TLC plate is then placed in a TLC chamber and the chromatograms are developed. When the solvent front has moved 8 cm TLC normal-phase system

-

Monoglycosides

Solvent: CHCI3/CH$H 80:20 Coating material: Silica gel 60 F 254

Di-/oligoglycosides Stari

Coloring reagent: 0.5 g thymol in 95 mi ethanol + 5 ml conc. sulfuric acid

Alkyl polyglycoside sample

Figure 7. Normal-phase TLC system for alkyl polyglycoside analysis

31

Analysis of Alkyl Polyglycosides

from its starting position, the plate is removed from the chamber, dried, immersed in thymol solution and heated at 105 "C until the glycosides become visible as red spots. Identification is based on the color of the spots, which is relatively specific for carbohydrates, and on the distances of the spots to be analyzed from the baseline by comparison with those of the alkyl polyglycoside calibration substances chromatographed on the same plate. The alkyl polyglycosides are separated according to their polarity. The alkyl monoglycosides move ahead followed by the di- and oligoglycosides. For most samples, the spots produced by the alkyl monoglycosides are sufficiently intensive and clearly separated from the matrix. The spots produced by mixtures of alkyl polyglycosides with different alkyl chains are larger because the alkyl chain has some bearing on polarity. However, no clear separation of single alkyl polyglycoside types according to different alkyl chain lengths can be achieved by this method. Figure 8 shows a typical TLC chromatogram for alkyl polyglycoside analysis in household products. \lkyl glycoside c8 ClO c12

Detergent

Dishwashing agent

Dishwashing agent

1

2

APG

APG

c12/14

c8/10

Alkyl glycoside c8

ClO c12

Figure 8. Alkyl polyglycoside analysis in household products-TLC chromatogram

Heinrich Waldhoff,Judith Scherler,Michael Schmitt,and Jan R-Varvil

32

100

-

Start

I

80 -

Alkyl rnonoglycosides

60 -

/

40 -

20 -

r )

10

20

30

40

50

60

Run time [rninl Figure 9. Quantitative analysis of alkyl polyglycosides by TLC-typical densitogram

For semiquantitativealkyl polyglycoside determination, the spot intensity of the sample to be analyzed is visually compared with that of calibration solutions chromatographed under the same conditions on the same plate. The accuracy of this very simple method is of the order of & 15 Yo (relative)which is sufficient for many purposes. Very accurate quantification by TLC can be achieved with a densitometer. TLC reversed-phase system

Hydrophobic (C18) silica gel

0.5 g thyrnol in 95 ml ethanol

+ 5 rnl conc. sulfuric acid C8 to C,, alkyl monoglycosides Figure 10. Typical reversed-phase TLC chromatogram of alkyl monoglycosides

33

Analysis of Alkyl Polyglycosides

A typical densitogram and the accuracy of data provided by this method are shown in Figure 9. The data reflect the accuracy of this method which is comparable with that of HPLC or GC. The alkyl polyglycoside type is identified by reversed-phase TLC (RP TLC). The components in an alkyl polyglycoside sample are separated according to alkyl chain lengths. A typical chromatogram and conditions are shown in Figure 10.The stationary phase in this system is hydrophobic silica gel (octadecyl trichlorosilane derivative). The method is applied for a clear identification of the alkyl polyglycoside composition, either for an alkyl polyglycoside product itself or in consumer product analysis. A typical RP TLC plate from dishwashing detergent and laundry detergent analysis is shown in Figure 11. Normal-phase and reversed-phase TLC have proven to be fast, uncomplicated methods which give satisfactory results for most samples. Like every chromatographic method, however, TLC can be problematical if matrix sub-

Alkyl

Deter-

glycoside

gent

c8

c 10

c 12

DishDishwashing washing agent agent 1

APG

APG

C12/14

C8/10

2

Figure 11. Reversed-phase TLC chromatogram of dishwashing agent and detergent

Heinrich Waldhoff,Judith Scherler, Michael Schmitt,andJan R.Varvi1

34

stances underlay the sample spots. Accordingly, results should be carefully checked and, in the event of doubt, should be confirmed by a second method. 2.2 Alkyl polyglycoside analysis by HPLC

Another method routinely applied for alkyl polyglycoside analysis in formulated products is HPLC. Figure 12 shows chromatograms of a commercial C ~ 1 4 alkyl polyglycoside (standard) and a dishwashing agent. The chromatograpic conditions and equipment used are identical with those shown in Figure 3. The alkyl monoglycoside peaks are particularly significant. In the product chromatogram the monoglycosides are positioned in such a way that there is basically no interference from matrix components. The alkyl polyglycoside concentration is calculated from the monoglycosides using an alkyl polyglycoside type identical with that in the product as standard. Chromatograms of laundry detergents are shown in Figure 13.The influence of matrix components is relatively strong. In this case, the C12lI4alkyl poly-

55 50 45

-

40

-

Commercial alkyl polyglycoside

C12 rnonoglycoside

I

(standard) C14 monoglycoside

4

8

Response [ m y 55 50 45 40 35 30 25 20

12 16 20 24 28 32 36 40 44 Run time [minl

-

Dishwashing agent C12 monoglycoside

Alkyl polyglycoside content 2%

Figure 12. Determination of alkyl polyglycosides in a dishwashing agent by HPLC

Analysis of Alkyl Polyglycosides

35

Response [my a

Light duty detergent Alkyl polyglycoside content 3.1 %

4

8

Response [my

a

C12

b

C14

rnonoglycoside rnonoglycoside

12 16 20 24 28 32 36 40 44 Run time [rninl

Color heavy duty detergent Alkyl polyglycoside content 1.7%

a

C12

b

C14

rnonoglycoside rnonoglycoside

12 16 20 24 28 32 36 40 44 Run time [rninl Figure 13.Determination of alkyl polyglycosides in laundry detergents by HPLC 4

8

glycoside concentration is calculated first from the C,, monoglycoside peak and then additionally from the C,, monoglycoside peak. Only if both calculations produce the same result mistakes attributable to matrix components can be minimized. In the absence of a clear-cut result, analysis has to be preceded by special preparation of the sample (extraction with ethanol and isolation of the nonionic compounds by passage through a mixed-bed ion exchanger) Both methods-the relatively simple and inexpensive TLC and the more complicated and expensive, but higher resolving HPLC- have proven to be effective tools for determining alkyl polyglycosides in formulated products. 3. Alkyl polyglycoside trace determination in environmental matrices

Most alkyl polyglycoside containing consumer products, such as detergents, cleaners, etc., enter wastewater or the environment after use. A series of tests (details see Chapter 11) can be carried out to ensure environmental safety (Table 3 ). Substance-specificanalytical methods have been developed for this purpose.

36

Heinrich Waldhoff,Judith Scherler,Michael Schmitt, and Jan R.Varvi1

Table 3. Alkyl polyglycosides-selected environmental safety tests [41 Method

Matrix

OECD confirmatory test River simulation model Acute/chronic Daphnia toxicity Prolonged fish test

Sewage River water Synthetic test medium Tap water

Concentration [ppml

40 - <0.2 10 - <0.1 100/10 - <0.1 10 - <0.1

Those enable alkyl polyglycosides to be analyzed in environmental matrices with a detection limit in the ppb range. The first step is to preconcentrate and separate the material of interest from the matrix by solid-phase extraction. The solid-phase material used is hydrophobic silica gel (octadecyltrichlorosilane derivative). After preconditioning with methanol, 0.1-1 1 of sample solution is passed through the cartridge or empore disk. After rinsing with water, the adsorbed surfactant is eluted with methanol. Recovery is in the 95-100Yo range. In the extract, alkyl polyglycosides are determined by HPLC or GC methods identical or comparable with those already described. Figure 14 shows the HPLC chromatogram of an alkyl polyglycoside analysis from sewage. Alkyl polyglycoside determination was performed with the aid of a gradient HPLC system using an electrochemical detector to achieve sufficient specificity and sensitivity. Only the peaks of the monoglycosides are clearly Response [ m y Column: Lichrosorb RP-8 Eluent: Acetonitrile/water gradient

I

Flow: 1 ml/min Detector: Dionex PED

Figure 14. Determination of alkyl polyglycosides in sewage by HPLC

Analysis of Alkyl Polyglycosides

37

Response [mVl

l5

I

Concentration: 0.18 ppm

1

b

30

32.5

35

37.5

40

a Cp b C12 c c14 d c14

c

42.5

45

47.5

a-glucopyranoside p-glucopyranoside a-glucopyranoside p-glucopyranoside

50

Run time [rninl

Figure 15. Determination of alkyl polyglycosides in tap water (from the prolonged fish test) by gas chromatography

separated. Quantification is based on the external standard method. The alkyl polyglycoside sample used for calibration was identical with the alkyl polyglycoside used in the biodegradation test. Gas chromatography was used to analyze a water sample from a prolonged fish test. The chromatogram is shown in Figure 15. There are no problems in separating the different alkyl polyglycoside peaks from matrix components due to the high resolution of the GC method used. The sample was analyzed by Alkyl polyglycoside concentration [rng/ll

2

*\ I

-*-*I

4

6

I

I

10

8

number of stairs

Figure 16. River simulation model-alkyl polyglycoside concentration profile

38

Heinrich Waldhoff, Judith Scherler, Michael Schmitt, andJan R.Varvi1

normal temperature gas chromatography which is more suitable for alkyl polyglycoside trace analysis than HTGC. Figure 16 shows a typical alkyl polyglycoside concentration profile from an experiment using the river simulation model (see Chapter 11, 2.4) [41. The analytical method was again GC. 4. Future demands in alkyl polyglycoside analysis

A broad range of analytical methods has been developed to meet present demands in alkyl polyglycoside analysis. The analytical methods discussed here have been developed over the last ten years in the analytical laboratories of Henkel. Comparable methods for alkyl polyglycoside analysis were published by other groups in 1995 and 1996 [5-81. Future analytical tasks will be in the environmental sector to improve the sensitivitiesof analytical methods to limits below 1 ppb. This will be a realistic range for future alkyl polyglycoside concentrations in real matrices, such as sewage treatment plant effluents, etc. Further improvements will be made to enable methods to be adjusted to a broader range of consumer products. Existing methods for the analysis of commercial alkyl polyglycosides will have to be standardized with regard to the most important quality-relevant parameters. References 1. H. Waldhoff, J. Scherler, M. Schmitt, Proceedings 4th World Surfactant

Congress, Barcelona, June 1996, Vol. 1, p. 507 2. P. J. Flory, J. Am. Chem. SOC.74 (1952) 2718

3. Henkel Corp., unpublished results 4. J. Steber, W. Guhl, N. Stelter, F. R. Schroder, Tenside Surf. Det. 32 (1995) 515 5. R. Spilker,B. Menzebach, U. Schneider,I.Venn, Tenside Surf. Det. 33 (1996) 21 6. N. Buschmann, A. Kuse, S. Wodarczak, Agro Food Industry, Hi-Tech,January/February (1996) 6 7. N. Buschmann, S. Wodarczak, Tenside Surf. Det. 32 (1995)336 8. A. Bruns, H. Waldhoff, W. Winkle, Chromatographia 27 (1989) 340

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

4. Physicochemical Properties of Alkyl Polyglycosides Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

The favorable performance properties of surfactants are essentially attributable to specific physicochemical effects [ l l . This applies on the one hand to interfacial properties and on the other hand to behavior in solutions, for example phase behavior. In contrast to fatty alcohol ethoxylates (alkyl polyglycol ethers), there have hitherto been comparatively few studies of the physicochemical parameters of alkyl polyglycosides. In the course of those studies, alkyl polyglycosides were found to possess remarkable properties which, in some cases, differ clearly from those of other nonionic surfactants. The results obtained so far are summarized in the following. Significant differences in relation to the behavior of fatty alcohol ethoxylates in particular are highlighted. 1. Phase behavior 1.1 Binary systems

In contrast to systematic studies of fatty alcohol ethoxylates, only a few studies involving substances of different purity have hitherto been conducted into the phase behavior of alkyl polyglycosides. When comparing the results obtained, it is important to keep in mind that the presence of secondary components has a considerable influence on details of the phase diagrams. Nevertheless, basic observations can be made on the phase behavior of alkyl glycosides. The phase behavior of a technical C,,,, alkyl polyglycoside (CS/lO APG) is illustrated in Figure 1 [21. At temperatures above 20 "C, the C,,,, APG is present up to very high concentrations in an isotropic phase of which the viscosity increases considerably. A birefringent lyotropic phase of nematic texture is formed at around 95 010 by weight, which changes at around 98 010 by weight into a cloudy two-phase region of liquid and solid alkyl polyglycoside. At relatively low temperatures, a lamellar liquid crystalline phase is additionally observed between 75 and 85 Yo by weight. For a pure short-chain n-octyl-p-D-glucoside, the phase diagram was investigated in detail by Nilsson et al. [31and Sakya et al. [41. The individual phases were closely characterized by such methods as NMR and small angle X-ray scattering (SAXS). The phase sequence is illustrated in Figure 2. At low temperatures, a hexagonal, a cubic and finally a lamellar phase are observed with increasing surfactant content. Differences in relation to the C,, alkyl polyglycoside phase diagram (Figure 1) can be explained by different alkyl chain length cuts and by a different number of glucose units in the molecule (see below).

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

40

Temperature I'CI

Temperature ["CI

1001

401

3020 20

10 -

70

80

90 100 Concentration [wt.-%]

Figure 1. Phase diagram of the C ,, AF'GIwater system I21

60

80

Concentration Id.-%] Figure 2. Phase diagram of the n-octyl p-D-glucoside/water system [31

The phase diagram of the C,, alkyl polyglycoside (CWMAPGVwater system (Figure3 )differs clearly from that of the short-chain APG.At low temperatures, a region corresponding to a solid/liquid region below the Krafft point is formed over a wide concentration range. With an increase in temperature, the system changes into an isotropic liquid phase. Since crystallization is kinetically retarded to a considerable extent, this phase boundary changes position with the storage time. At low concentrations, the isotropic liquid phase changes above 35 "C into a two-phase region of two liquid phases, as is normally observed with nonionic surfactants [51. At concentrations above 60% by weight, a sequence of liquid crystalline phases is formed at all temperatures. It is important to mention that, in the isotropic single-phase region, a distinct streaming birefringence can be observed at concentrations just below the lyotropic phases,

:.p

Temperature ['Cl

80

-----

20

----a

, \,c: I

\

I

L

I

20

40

60 80 100 Concentration [wt.-%]

Figure 3. Phase diagram of the C,,,,, APG/water system [21

Physicochemical Properties of Alkyl Polyglycosides

41

disappearing again rapidly on completion of the shearing process. However, no multiphase regions separating this region from the L, phase could be found. In the dilute L, phase, there is another region with weaker streaming birefringence which is situated near the minimum of the liquid/liquid miscibility gap. Phenomenological investigations into the structure of the liquid crystalline phases were conducted by Platz et al. [61 using such methods as polarization microscopy. According to these investigations, there are three different lamellar regions in concentrated C,,,,,APG solutions: Lal, L, and La, Polarization microscopy shows that there are three different textures (Figure 4, a-c). After prolonged storage, a typical lamellar liquid crystalline phase develops dark pseudoisotropic regions under polarized light. These regions are clearly separated from the highly birefringent areas. The L, phase, which occurs in the medium concentration range of the liquid crystalline phase region, preferably at relatively high temperatures, shows such textures. Schlieren textures are never observed, although strongly birefringent oily streaks are usually present. Pseudoisomorphism is characteristic of lamellae which are isotropic in their plane and which are aligned parallel to the walls of the object slide. Such lamellae contain regions which, on average, are arranged at a right angle to the lamellar layers. Fluid lamellar structures fulfill these conditions. If the slide is tilted, there is no further pseudoisotropic orientation in the observation direction and strong birefringence occurs. In this way, pseudoisotropic orientation can be distinguished from isotropic phases.

a

b

C

Figure 4. Polarization micrographs of textures of lyotropic phases in C, APG solutions I21; a) L, with pseudoisotropism: 75 Yo by weight at 25 "C after heating to 70°C; b) L,: 90% by weight at 25 "C; c) La,-h:68% by weight at 70°C

42

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

If a sample containing an L, phase is cooled to determine the Krafft point, the texture changes below a characteristic temperature. The pseudoisotropic regions and the clearly defined oily streaks disappear. Initially, no C,,,,,APG crystallizes, instead, a new lyotropic phase (L,) showing only weak birefringence is formed. At relatively high concentrations, this phase expands up to high temperatures. The La, texture resembles that of a nematic rodlike micellar phase. In contrast to a genuine rodlike micellar phase, however, it is not possible to obtain an orientation in strong magnetic fields. In thermotropic liquid crystals, a corresponding texture is typical of optically biaxial thermotropic smectic C phases which contain regularly inclined unitsin their lamellar structure, causing anisotropy in the lamellar plane. The derivation of these results from various test methods is described in ref. [21. The lyotropic region which occurs at the lowest C,,,,,APG concentrations has a texture with fan-like structures. As in the case of the La, phase, there is no pseudoisomorphism in this region. The fan-like structures observed under a polarization microscope suggest the assumption that a hexagonal configuration is present. Such “brokenfocal cone textures”are characteristicof biaxial smectic thermotropic phases. The fact that the La,, phase has a lamellar rather than a hexagonal structure is supported by the formation of lamellar droplets in the two-phase L,,/isotropic solution region. The textures themselves also show significant differencesin their fine structure. If a hexagonal lyotropic phase is sheared, complete orientation occurs and remains permanently unchanged. Under the effect of shear forces, an L,.h texture is converted into an La,phase which changes back into an , L phase a few hours after shearing. If the L, phase is cooled below the Krafft temperature, an L, phase is formed in the same way as when the L d phase is cooled. In the vicinity of the phase boundary to the Ld phase, the L,-h phase is converted by heating into an L, phase. On cooling, the textures of the Laibhphase are reformed. The transition temperatures on heating are distinctly higher than the transition temperatures on cooling. This shows that a strong kinetic inhibition is present and makes exact determination of the phase boundaries difficult. The formation of such an L, phase by cooling of a lamellar phase with fluid lamellae (L,) below the Krafft temperature can be explained on the assumption that complete or partial crystallization requires an inclined position of the molecules which leads to a lamellar structure of relatively low symmetry and hence to a biaxial system. No transitions to multiphase regions could be found between the various lyotropic phases of CI2/,4APG.The reason for this may lie in the high viscosity of the system which prevents separation. However, it may also be that the regions are only separated from one another by phase transitions of a higher order.

Physicochemical Properties of Alkyl Polyglycosides

43

It is interesting that the crystalline precipitations, which are formed when dilute C,, APG solutions are cooled below the Krafft point, can be converted into a liquid crystalline La,texture under the effect of shear forces. The same does not apply to a “genuine” crystalline solid phase. Highly hydrated C, APG evidently forms a “quasi-crystalline”state [71. The broken line in Figure 3 represents the upper melting curve after cooling of the systems to 5 “C over a period of 12 h. It is noticeable that precipitation proceeds far more slowly in dilute solutions. The phase diagram of the relatively short-chain alkyl polyglycosides is considerably simpler. At low temperatures, a lamellar phase of the La,, type is formed at about 80 VOby weight. Given an apparently nematic texture at around 95% by weight, an L, phase is probably present. The influence of the degree of polymerization (DP) of alkyl polyglycosides on their phase behavior was described by Fukuda et al. [81. Figure 5 is a simplified illustration of the phase diagrams of Cl2 alkyl polyglycosides containing different numbers of glucose units in the molecule. The region in which the liquid crystalline phases occur is only slightly dependent on concentration with a slightly greater expansion in the case of alkyl polyglycosides containing a relatively large number of glucose units. For C12 alkyl polyglycoside with a DP of 1.1 and 1.4, it was demonstrated that the entire liquid crystalline region consists of a lamellar phase. The two more hydrophilic surfactants initially form a hexagonal liquid crystalline phase which is converted into lamellar liquid crystals at relatively high concentrations. The two alkyl polyglycosides containing relatively few glucose units have a two-phase region (see also Figure 3)at low concentrations which is reminiscent of the clouding phenomena of nonionic surfactants of the ethylene oxide type [51. It can be seen from Figures 1 and 3 that this effect is strongly dependent on the alkyl chain length so that, although the two-phase region occurs in the case of the C,,,,, APG, it is no longer in evidence in the case of a C,,,, APG. Balzer [91 investigated the clouding phenomena in dependence upon various parameters. He showed that the two-phase region is influenced to a far greater extent by the length of the alkyl chain than in the case of alkyl polyglycol ethers (C,E,). If it is assumed that the cloud point of alkyl polyglycol ethers is linearly dependent on the alkyl chain length, a shortening of the alkyl chain by two carbon atoms represents an increase in the cloud point of around 15“C. By contrast, in the case of alkyl polyglycosides, the lower consolute temperature of a C,,,,, alkyl polyglycoside is between about 20 and 40 “C, depending on the chain length distribution and the degree of polymerization. At temperatures of up to 100 “C, a C,,,,2 alkyl polyglycoside no longer shows any separation so that, in this case, the differentiation is at least 60 to 80 “C for of two carbon atoms in the alkyl chain.

44

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

loo-yL I I

’

L

2L

L

L.C.

I

I

I I

50-1 42 ’

/ 38

-’ S

S

100-

100L

L.C.

L

L.C.

ri 50 -

50 -

38 S

38

50 100 Concentration [wt.-%I

S

I

50 100 Concentration [wt.-%I

Figure 5. Schematic phase diagrams of four C,, alkyl polyglycoside/water systems with different DP: a) 1.1, b) 1.4, c) 1.6, d) 1.8 [81

The dependence of the two-phase region on the alkyl chain length was elucidated in more detail by mixing Clo/lzalkyl polyglycoside with C,,,,, APG. If increasing quantities of C10/12alkyl polyglycoside are added to C,,,,, APG, the initially broad miscibility gap becomes gradually narrower (Figure 6),the separation zone separates from the Krafft point curve and a lower separation point becomes visible. Accordingly, the dependence of the clouding effect for alkyl polyglycosides is comparable with that of alkyl polyglycol ethers, although the dependence on chain length is extremely strong for alkyl polyglycosides. In

45

PhysicochemicalProperties of Alkyl Polyglycosides

Temperature ['Cl

Figure 6. Phase diagrams of alkyl polyglycoside (DP = 1.3)for different alkyl chain lengths in the concentration range to 30 Yo by weight [91

5

10

20 25 30 Concentration [wt-%I

15

order to shift the cloud point from 25 "C to 90 "C, it is sufficient to change the alkyl chain length cut from C, to C,,,. In the case of alkyl polyglycol ethers, a corresponding change in chain length would signify a change in the cloud point of only 2 "C. An equally strong influence on the cloud point is observed when the degree of polymerization is changed [91. In this case, too, small changes have a considerable influence on clouding behavior. This may also explain the differing data described in the literature for the phase diagrams of alkyl polyglycosides which were determined on surfactants with different alkyl chain cuts and different degrees of polymerization. If small quantities of electrolyte are added to alkyl polyglycosides, clouding phenomena are also observed with relatively short-chain alkyl polyglycosides [91. In this case, the electrolyte effect is far more clearly pronounced than in the case of alkyl polyglycol ethers for which the influence of salt type and concentration has long been known [lo].The results for a CIzll4E7and a C,,,,, alkyl polyglycoside with a DP of 1.8 on addition of various sodium salts are compared with one another in Figure 7 (a,b) 191. In the case of C,,l,4E,, SCN- and Ianions increase the cloud point whereas all other anions investigated lead to a more or less pronounced reduction in the cloud point. The necessary concentration of electrolytes is very high. According to Balzer 191,these effects may be understood on the basis of a balance of the interactions between water and ethylene oxide (EO)groups. On the one hand, there is a highly ordered hydration shell of the ethylene oxide groups of the polyglycol ethers and, on the other hand, a more or less strong polarization of water by the ions. The very large and weakly polarizing anions I- and SCN- are presumably concentrated in the vicinity of the EO group, which contributes to an increase in the repulsing

46

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

Temperature Tc "C1

Temperature Tc "Cl

14

a

loo 80

/" /"

b NaSCN

80A

60*

.

c,O

H

R 0

*

-" N-aF

NaOH NaCl

NaF

0.06

0.08

I

0.'3 0:6

0:6

1.2

115

Concentration [mol/ll

0.02

0.04

0.1

Concentration [mol/ll

Figure 7. Cloud point temperatures T, of 5% surfactant solutions as a function of the electrolyte concentration: a) 5 Yo C,,,,4E,, b) 5 Yo C,,,,, alkyl polyglycoside (DP= 1.8) [91

electrostatic interaction of the micelles and increases the cloud point. With all other electrolytes,the strong hydration of the small and highly polarizing ions, together with the high concentration, probably disturbs the entropically unfavorable hydrate structure of the EO group. According to Kjellander [111, this leads to the displacement of the electrolyte from the vicinity of the EO group with a mutually attracting interaction of the micelles; the cloud point falls. In the case of alkyl polyglycosides, a different picture emerges. With the exception of NaOH, all electrolytes lead to a distinct reduction in the cloud point. The concentration range of the electrolyte is lower by about one order of magnitude than in the case of alkyl polyglycol ethers. Surprisingly, there are only very slight differences between the individual electrolytes. The addition of alkali produces a distinct reduction in the clouding phenomenon. As an explanation for the difference in behavior between alkyl polyglycosides and alkyl polyglycol ethers, it may be assumed that the cumulative OH groups of the glucose units undergo a different type of hydration compared with the ethylene oxide groups. The distinctly greater effect of electrolyteson alkyl polyglycosides suggests that there is a charge at the surface of the alkyl polyglycoside micelles of which the absence is postulated for alkyl polyglycol ethers 1121. Accordingly, the behavior of alkyl polyglycosides resembles mixtures of alkyl polyglycol ethers and anionic surfactants 1131.Investigations of the interactions between alkyl polyglycosides and anionic or cationic surfactants and 4 potential measurements on emulsions indicate that alkyl polyglycoside micelles have a nega-

PhysicochemicalProperties of Alkyl Polyglycosides

47

tive surface charge in the pH range from 3 to 9 [91. By contrast, the charge of micelles of alkyl polyglycol ethers is weakly positive or approximately zero. The reasons for the negative charge of the alkyl polyglycoside micelles have not yet been fully explained. 1.2 Multicomponent systems

The addition of fatty alcohols as a third component to alkyl polyglycoside/ water mixtures leads to the appearance of different lamellar phases over the entire concentration range 161. This behavior is typical of the influence of fatty alcohols on the phase behavior of binary surfactant/water systems 1141. The lamellar phases are surrounded by L, phases which are optically isotropic and, at the same time, shows strong streaming birefringence. Figure 8 shows the phase diagram determined for the addition of hexanol to various mixtures of C,,,,, APG and water. Three La phases can be seen: L,, L,, La,-h.The almost linear trend of the phases as a function of the alkyl polyglycoside and hexanol concentration indicates that the structure formed depends primarily on the alkyl polyglycoside/alcohol ratio. It is noticeable that, in all, three LJ phases occur. The L,, phase appears at hexanol concentrations below the lower lamellar La, phase. The L,m phase occurs at very low surfactant concentrations. With increasing surfactant concentration, it moves above the L,, phase. The upper L, phase (Lsh)lies above the phase. The L,, and L,m phases disappear at relatively high surfactant concentrations. The influence of the chain length of the fatty alcohol on the position of the phases in the ternary C,,,,, APG/water/alcohol systems is illustrated in Figure 9 for the example of a 5 010 C,,,,, APG solution. The quantity of alcohol added is Concentrationc,,, ht-%l 201 15 10

Figure 8 . Phase diagram of the C,,,,, AFG/hexanol/water system at 25 "C 161

J

I

40 60 Concentration C I Z , ~APG ~ [wt.-%]

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

48

ConcentrationCnOH [mmol/l]

Figure 9. Phase behavior of a 5 o/, C,,,,, APG solution on addition of alcohols varying in alkyl chain length n at 25 "C I61 18 I

n= 4

6

8

10

12

14

16

plotted against the chain length of the alcohols. When butanol is added, a liquidlliquid separation occurs. Alcohols with a longer alkyl chain (n> 4)promote the formation of liquid crystalline phases. It is clear that the relative sequence of the individual phases is almost the same with all alcohols.A marked dependence on concentration is evident in particular in the case of short-chain and medium-chain alcohols. The quantity of alcohol which has to be added to ensure that a certain phase is formed decreases drastically with increasing alkyl chain length of the alcohol. When relatively long-chain alcohols are added, the Ld.h phase becomes the dominant phase. In principle, the phase sequences observed with mixtures of alkyl polyglycosides and anionic surfactants, which are of particular importance in practice, are similar to those observed with the ternary systems of alkyl polyglycoside, alcohol and water [GI.This is illustrated in Figure 10 for a mixture of C,,,,, APG,sodium C,,,,, sulfate, hexanol and water with a constant concentration of alkyl polyglycoside. The L, phase disappears on the addition of fatty alcohol sulfates (FAS)and the L, region becomes very dominant. The phases which additionally contain ionic surfactants appear optically more transparent and have a higher viscosity and elasticity than systems consisting solely of alkyl polyglycoside and alcohol. Yield points which increase considerably with higher concentration of fatty alcohol sulfate are obtained in the La,-hand LZm phases of these systems. Dilute lamellar phases can only be obtained in C,,,,, APG solutions by addition of fatty alcohol. Fatty alcohol has to be added for steric reasons. Anionic surfactants have large head groups. Accordingly, in the case of systems containing fatty alcohol sulfates, relatively large quantities of

49

Physicochemical Properties of Alkyl Polyglycosides

Concentration

Figure 10. Phase behavior of a 5% C, APG solution on addition of hexanol (C,OH) and FAS (C,,,,,SO,Na) at 25°C [61

[rnrnol/ll

i

2

ConcentrationFns [wt.-%l

fatty alcohol are required to obtain a lamellar structure. This explains why the lamellar phases in these systems are displaced towards higher fatty alcohol concentrations. It is interesting that the repulsing forces between the charged lamellae and hence the elastic shear moduli are far greater than in uncharged systems. Relatively large viscous and elastic moduli were observed with all the anionic surfactants investigated. The addition of anionic surfactants also has an influence on the clouding phenomena. The cloud points are considerably increased by small quantities of alkyl sulfates. According to Balzer [91, small quantities of alkyl sulfate lead to a change in the electrical charge of the alkyl polyglycoside micelles. This results in a greater repulsing interaction between the micelles and leads to a distinct increase in the cloud point. 2. Rheological properties

The flow behavior of alkyl polyglycoside solutions is characterized by three different viscosity ranges: at low alkyl polyglycoside concentrations, the viscosity increases linearly with concentration. The results of measurements with an Ubbelohde capillary viscosimeter set out in Figure 11 show that C,,,, APG follows this linear relation to beyond 5 % while the long-chain C,,,,, APG barely follows it up to 0.05 9'0. In the case of C,,,, APG, the slope of the specific viscosity against the volume fraction of the surfactant is 3.9. For non-hydrated spherical micelles, a value of 2.5 would be expected on the basis of the Einstein equation.

50

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

Viscosityq [mPa.s]

Viscosityq, [mPa.s]

1

I

1

2

3

4

5

Concentration [%I Figure 11. Viscosities of dilute C,,,, and C,,,,, APG solutions [21

20

40

60

80

Concentration [%] Figure 12. Zero shear viscosities of CW~, and C ~ 1 APG 4 solutions from oscillating measurements at 30 “C 121

Above these concentrations, there is a region in which the viscosity of both surfactants increases considerably with concentration. In the case of C,,,,,APG, this increase is confined to a narrow concentration range of up to about 15o/o whereas C,,,, APG exhibits corresponding behavior up to the highest concentrations. The third viscosity range is only observed in the case of C,,,,, APG. Above 150!0,the viscosity only increases linearly with concentration up to almost the lyotropic phase. At very high concentrations, therefore, the viscosities of C,,,, and C,,,,, APG are almost identical on the logarithmic scale. The particularly high increase in viscosity is attributable in the case of C,,,,, APG to steric hindrances during the shearing of rodlike micelles which are formed even at very low concentrations and overlap one another in space. By contrast, in the case of C,, APG, the micelles are substantially spherical. Accordingly, viscosity remains low up to high concentrations. At the onset of the mutual steric hindrance of the spherical micelles, viscosity increases considerably and even reaches the values of C,,,,, APG solutions of equal concentration. Oscillating measurements with a Bohlin rheometer show that, at moderate shear rates, the solutions behave like Newtonian liquids up to very high concentrations. Figure 12 shows the zero shear viscosities determined with the Bohlin rheometer. In the case of C,, APG, not only the viscous component G” but also the elastic shear modulus G’ can be determined by the oscillating measurements at very high viscosities (Figure 13). The elastic components G’ increase with concentration, but remain smaller than G” up to high frequencies. The G’ values also increase with increasing temperature. The frequency behavior of the moduli G’ and G” correspond to a Maxwell liquid only in the isotropic phase.

51

Physicochemical Properties of Alkyl Polyglycosides

Structure relaxation time T Is]

G', G [Pal

10

20

30

40 50 60 Concentration [%I

Figure 13. G' and G" values of CI2m APG at 1 Hz and 2 5 "C [21

10

20

30

40 50 60 Concentration [%I

Figure 14. C,,,,, APG structure relaxation times at 25 "C [21

The structure relaxation times are shown in Figure 14. These times are extremely short and, in the case of C ,, APG, cannot be measured. It is noticeable that the structure relaxation time measured in the case of C, APG has a maximum value which lies at a concentration which substantially corresponds to the minimum of the miscibility gap. It may be assumed from this that the attractive interaction between the rodlike micelles formed from spherical micelles with increasing concentration becomes so great that degradation of the rodlike micelles begins when more surfactant is added. Only in the vicinity of the maximum structure relaxation time is a distinct streaming birefringence also observed when the solutions are sheared between two crossed polarizers. 3. interfacial Properties 3.1 Surface Tension

The surface tension of alkyl (po1y)glycosideswas investigated as a function of the alkyl chain and the degree of polymerization (DP)using samples differing in composition. In addition to pure surfactants for characterizing the basic dependencies, numerous data on surfactants of technical quality is available because of the interest in using alkyl polyglycosides on an industrial scale. Shinoda et al. t151 and Bocker et al. [161 determined the critical micelle concentration (cmc)and the surface tension values at the cmc from surface tension/concentration curves. A few selected values are set out in Table 1. Figure 15 shows the surface tension as a function of concentration for three alkyl monoglycosides (C,G1)and a technical C,,,, APG , at 60 "Ct171. The cmc values of the pure alkyl

52

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

Table 1. cmc values from surface tension measurements

Substance

cmc

Temperature ["CI

[mol/ll

25 25 25 25 60

2.5.10-' [151 1.8.10-2 [161 2.2.10-3 1151 1.9.104 [151 1.7.10-4 [161

polyglycosides and the technical alkyl polyglycosides are comparable with those of typical nonionic surfactants and decrease distinctly with increasing alkyl chain length. As the figures set out in Table 1 show, the alkyl chain length has a far stronger influence on the cmc by comparison with the number of glucoside groups of the alkyl polyglycosides. The surface tension behavior of surfactant mixtures of alkyl polyglycosides and anionic surfactants was investigated with reference to the example of an alkyl polyglycoside/fatty alcohol sulfate (FA9 mixture. Figure 16 shows the surface tensiodconcentration curves at GO "C for C,,,,APG, C,,,,, FAS and for two mixtures of these surfactants, as measured at GO "C [171. The values of the mixtures are near the curve for alkyl polyglycoside even despite a high anionic surfactant content. This corresponds to the normally observed behavior of

Figure 15. Static surface tension (T of alkyl glycosideswith different alkyl chain lengths as a function of the concentration in dist. water at 60°C [171

Figure 16. Static surface tension cs of C,,,,, APG and C,,,,, FAS and 1:l and 4:l mixtures thereof as a function of the concentration in dist. water at 60 "C [ 171

Physicochemical Properties of Alkyl Polyglycosides

53

mixtures of anionic and nonionic surfactants differing considerably in their cmc values [181. A weak attractive interaction between these surfactants can be derived on the basis of Rosen's theory [191. The kinetics involved in the establishment of surface tension were investigated by measurement of the dynamic surface tension. This describes the rate at which the surface tension of about 72 mN/m at an interface freshly formed between water and air is reduced by the influence of surfactants. Figure 17 shows the reduction in surface tension as a function of time for the same surfactant solutions at a concentration of 8.10-4moles/l at 40 "C1201. The curve of the pure FAS falls more quickly for short times than that of pure alkyl polyglycoside which shows that the FAS diffuses more quickly to the surface of the liquid than the alkyl polyglycoside with the same alkyl chain length. The mixtures of both surfactants reach lower surface tensions than the pure surfactants. It should be noted that surfactants of technical purity were compared with one another in these investigations. This factor can be important to the interpretation of the results of dynamic surface tension measurements because the individual components of the technical surfactants can have a different affinity for the surface D11. 3.2 Oil/water interfacial tension

The interfacial tension of surfactant solutions with respect to oils can be measured by various methods. If the values are very low, a spinning drop tensiometer G [mN/rnl 80

60

8-

40

64-

20

APG:FAS=4:1

2I,,,

5

10

15

20 Time [sl

Figure 17. Dynamic surface tension CT of C, APG and C,, FAS and 1:l and 4:l mixtures thereof as a function of time in dist. water at 40 "C and at a concentration of 8 . W moles/l [201

0.1

I

-

I , , , , , , ,

I

,,,,,,,,

I

I

I

1 10 40 Concentration [rnrnol/ll

Figure 18. Influence of alkyl glycosides (COG,)on decanelwater interfacial tension. Equilibrium values of the interfacial tension y as a function of the initial concentration of the surfactant in the water phase [221

54

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

is normally used. Investigating oils differing in structure and polarity provides important information on the property profile of a class of surfactants. The interfacial tensions of various alkyl polyglycosides against three oils (decane, isopropyl myristate and 2-octyl dodecanol) differing in structure and polarity was investigated by Kutschmann et al. [221. Figure 18 shows the interfacial tension of C,G,, C,,G, and C,,G, against decane at 60 "C in dependence upon the surfactant concentration. The concentrations at the break in the curves (c,) accord well with the cmc values obtained from surface tension measurements (Table 1). This means that, in the equilibrium state, the surfactant is completely present in the aqueous phase and is not measurably dissolved in the decane phase. Figure 19 shows the interfacial tension of C,G,, C,,G, and a technical C,,,, APG as a function of temperature. In the range from 25 to 60°C,there is no indication of dependence on temperature. This is a clear difference by comparison with the similarly nonionic fatty alcohol ethoxylates. Since electrolyte solutions are used instead of pure water in many applications, results on the influence of an electrolyte on the interfacial activity of alkyl polyglycosides are also available for a technical C,, APG. Even with extremely large additions of NaCl of more than 20% to the aqueous phase, the plateau value of the interfacial tension against decane remains substantially constant. These results also confirm earlier investigationsconducted by Shinoda et al. [151 in which it was shown that the addition of lyotropic salts to aqueous solutions of alkyl monoglucosides has no significant effect on surface tension. Only a slight shift in the cmc towards lower concentrations was observed. The influence of oil polarity is clearly illustrated by comparing the interfacial tensions of aqueous solutions of alkyl monoglycosides against the three oils. Figure 20a shows the interfacial tension curves of the three oils against the logarithmically plotted surfactant concentration for C,G,. For each oil, there is

31*-.-.-.-* Figure 19. Plateau values of the interfacial tension y, for various alkyl glycosides at the deanelwater interface as a function of the temperature [221

ClO G 1 30

40

50 60 Temperature I'C]

55

PhysicochemicalProperties of Alkyl Polyglycosides y [rnN/rnl

y [rnN/rnl

10 1 lsopropyl myristate

b

a

64-

2-

-..,..-.-

2-Octyl dodecanol L-.

I

,

8

10

7

20

30

40 Concentration [rnrnol/ll

I I

0.1

1.0

I , , ,

10

Concentration [rnrnol/ll

Figure 20. Influence of alkyl glycosides (a) C,G,; (b) C,,G, on oillwater interfacial tension y for three different oils as a function of the initial concentration of the surfactant in the water phase [221

a pronounced break and a constant plateau value which decreases in the order decane > isopropyl myristate > octyl dodecanol. For all three oils, the break occurs at substantially the same concentration of the surfactant in the water phase and accords well with the cmc values obtained from surface tension measurements on the aqueous solutions (see Table 1). This means that C,G, is not dissolved in any of the three oils. The corresponding curves for C,,G, are shown in Figure 2 0 b. For isopropyl myristate and octyl dodecanol, there is a distinct shift in the break of the isotherm towards higher concentrations of the surfactant. The position of the plateau value is also different. It lies at far higher values for octyl dodecanol than for the other two oils. The concentration at the breaks of the interfacial tension/concentration curves is shown in Figure 21 as a function of the alkyl chain length of the surfactants. It can clearly be seen how the position of the cmc apparently shifts towards higher values with increasing oil polarity. This effect is more pronounced, the longer the alkyl chain length of the glucoside. One possible explanation for this is the increase in the solubility of the surfactant in the oil phase with increasing alkyl chain length and, hence, hydrophobicity or increasing polarity of the oil. Figure 22 shows the plateau values r, of the interfacial tension of C,G, homologues and various technical alkyl polyglycosides against the three oils as a function of the chain length of the surfactant. For decanelwater and IPM/ water, y, decreases with increasing alkyl chain length and, hence, increasing hydrophobicity of the surfactant. By contrast, the curve of the octyl dodecanol/

56

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

Concentration cb [mmol/ll

y, [mN/ml

12 2-Octyl dodecanol

I

8

9

10 n

11

12

Figure 21. Concentration at the break in the interfacial tension/concentration curves cbin three different oil/water systerns as a function of the alkyl chain length of the surfactant n at 60 "C [221

I

8

12

10

n

14

Figure 22. Plateau values of the interfacial tension y, in three different oil/water systems as a function of the alkyl chain length of the surfactant n at 60°C [221

water system has a pronounced minimum in the case of C,,G, and increases steeply with increasing alkyl chain length. Since C,,G, is highly oil-soluble in the octyl dodecanol/water system, optimum affinity for the oil phase in this system is actually achieved in the case of C,,G,. The reduction in interfacial tension which can be achieved by surfactants can be expected to depend also upon the surface-active character of the oil. This dependence is illustrated by way of example for C,,G, in Figure 23. The empty circles represent the interfacial tension values yo in the pure oillwater system while the filled-in circles represent the plateau values of the interfacial tension y,. The yo value of octyl dodecanol/water is lower than that of isopropyl myristate/water. The reason for this may lie in the different hydrophobicity and Y [mN/ml

50i Figure 23. OiVwater interfacial tensions yo and plateau values of the interfacial tension y, for Cl,Gl in oil/ water systems with increasing amphiphilicity of the oil [221 (0)

(0)

1

n-Decane ?

;

I

25-1

lsopropyl rnyristate 0 2-Octyl dodecanol

; i I

I I

I

?

I I

Dyanol ? 0

Amphiphilic nature of the oil

Physicochemical Properties of Alkyl Polyglycosides

57

in the different sizes of the head groups of these two oils. For octyl dodecanol, the long alkyl chain provides for an additional surface-active character which should have a strong influence on interfacial behavior. Accordingly, the corresponding values for decanol are also included for comparison. In this case, a monolayer of decanol molecules can be expected at the boundary layer. In the presence of such a monolayer, surfactant molecules with a large head group should be incorporated less easily than might be expected for nonpolar oils or oils with a weakly pronounced surfactant character. 4. Microemulsion phases

Ternary systems of water, oil and nonionic surfactants can form microemulsions in dependence upon various parameters. Particular interest in this regard has been acquired by microemulsions of oil, water and ethoxylated nonionic surfactants which, on the one hand, are widely used in practice and which, on the other hand, are suitable as well-defined ternary mixtures for systematic experimental studies [23,241. One characteristic of these systems of oil, water and ethoxylated nonionic surfactant is their pronounced dependence on temperature which is the basis of the known phase inversion temperature (PIT) phenomenon [23,24,251. The phase behavior of simple alkyl polyglycoside/water mixtures differs in certain aspects from other nonionic surfactants (see 1. in this chapter). Temperature in particular is a parameter of minor importance in any comparison of alkyl polyglycosides with fatty alcohol ethoxylates. Whereas the hydrate shell of the ethoxylate head group depends largely on temperature, the interaction of the sugar unit of alkyl polyglycoside with water is only slightly influenced by temperature. This is reflected in the fact that the phase behavior of simple binary alkyl polyglycoside/water mixtures shows only comparatively weak temperature effects [6,26,271. Accordingly, no temperaturedependent phase inversion can be expected to occur in alkyl polyglycoside containing emulsions. Alkyl polyglycoside microemulsions are therefore only to be formulated in other ways. Similarly to anionic surfactants, alkyl polyglycosides react to the addition of co-solvents which increase the solubility of the surfactant in the oil phase. In the decane/water/alkyl polyglycoside system, the addition of the co-solvent ibutanol results in a drastic reduction in the interfacial tension between oil and aqueous phase and, hence, in the formation of a third phase, the microemulsion [281. As expected, the range in which this three-phase microemulsion exists is only slightly dependent on temperature and, in contrast to anionic surfactants, is also hardly affected by electrolytes [281. Systematic investigations of the phase behavior confirm these initial results for a number of simple hydrocarbons from hexane to hexadecane and aromatics [29,301.

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

58

Figure 24 shows the known “Kahlweit fish” [231 in a pseudoternary phase diagram. The ratio of dodecane to water was kept constant at 1:l. The ratio by weight of alkyl polyglycoside to alkyl polyglycoside/oil/water is shown in the lower half while the percentage content by weight of the co-solvent pentanol is shown on the left-hand side. With small alkyl polyglycoside contents of 5 to 25 O/o and small pentanol contents of 3 to 10Vo, three-phase microemulsions are formed. Of greater interest for practical applications are single-phase microemulsions (D)which are formed with an alkyl polyglycoside content of >25 O/o and a pentanol content of 100!0 in the system. Figure 24 includes the-almost identical-results for two different alkyl glycosides, namely a high-purity C,, monoglycoside and a C,,,, polyglycoside of technical purity with an average degree of polymerization of 1.3. In the technical product, the slightly increased degree of polymerization evidently compensates for the somewhat longer alkyl chain length cut. Co-solvents increase the solubility of the surfactant in the oil phase and thus modify the hydrophilic/lipophilic properties of the surfactant in the system I291. Another way of achieving balanced hydrophilic/lipophilic properties is to combine the hydrophilic emulsifier alkyl polyglycoside with a hydrophobic Pentanol

/

Oil/water

1/1

\

10

20

30

40 APG

Concentration [wt.-%l

Figure 24. Pseudoternary phase diagram for the systems dodecane/water in a ratio of 1: 1, pentanol, C,, monoglycoside (C,,G,) and C,,,,, alkyl polyglycoside (C,,,,,G,,,) at 40°C [291

Physicochemical Properties of Alkyl Polyglycosides

59

co-emulsifier. With reference to the example of cyclohexane/water emulsions, Figure 25 shows how both the mixing ratio of Clzalkyl polyglycoside (C12G)to the hydrophobic co-emulsifier alkyl glycerol ether and the oil/water ratio influence the type of emulsion 181. A total emulsifier concentration of 4 % for a balanced emulsifier mixing ratio is sufficient to form a single-phase microemulsion (D)which extends transversely through the diagram as a single-phase channel. The inserted graph demonstrates the temperature stability of the microemulsion. Representation of the microemulsion phases as a function of formulation parameters (for example temperature for systems containing fatty alcohol ethoxylate) and emulsifier concentration, as described in t23,311, has been successful as an aid for practical formulation work. A basically similar picture

0.261

I

I

0.2

0.4

0.6

0.8

1.0

Figure 25. Phase diagram for the system water, cyclohexane (c-C,H,,), 2-ethylhexyl glycerol ether (i-C,GE), C,, alkyl polyglycoside ( C I ~ Gat) 25 "C and a total emulsifier content of 4%. Detail: temperature dependence of the microemulsion range for an oil content of 40% (81

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

60

emerges for emulsions of oil, water and an emulsifier mixture of alkyl polyglycoside and a hydrophobic co-emulsifier when, instead of temperature as the formulation parameter, the mixing ratio of alkyl polyglycoside to hydrophobic co-emulsifier is varied 131,321.In the case of the specific emulsifier mixing ratio of 1:1, the system of dodecane, water, C,,,,, APG and sorbitan monolaurate (SML) as hydrophobic co-emulsifier forms microemulsions (Figure 26). The emulsionsformed with a relatively large SML content are w/o emulsions while the emulsions formed with a relatively large alkyl polyglycoside content are o/w emulsions. By varying the overall emulsifier concentration, a "Kahlweit fish" again appears in the phase diagram with three-phase microemulsionsin its body and a single-phase microemulsion in its tail. The similarity between alkyl polyglycosides and fatty alcohol ethoxylates is not confined to phase behavior, but also applies to the interfacial tension of the emulsifier mixture. With an alkyl polyglycoside/SML ratio of 4: 6, the hydrophilidlipophilic properties of the emulsifier mixture are balanced and the interfacial tension is minimal. It is remarkable that the alkyl polyglycoside/SML mixture produces a very low minimum interfacial tension value (around mN/m) which, once again, is lower by one order of magnitude than that observed in the case of the fatty alcohol ethoxylate system [18,23,331. C SML CAPG

+

CSML

a

b y [mN/ml

1

0.1

0.01

0.001

Figure 26. a) Phase behavior of the system dodecanelwater in a ratio of 1:1, C, APG, sorbitan monolaurate in dependence upon the ratio of APG to SML as a function of the total surfactant concentration; b) interfacial tension of the system dodecanelwater in a ratio of 1:1 C, APG, sorbitan monolaurate in dependence upon the ratio of APG to SML for a total surfactant concentration of 1.50/0[311

61

PhysicochemicalProperties of Alkyl Polyglycosides

In the case of the alkyl polyglycoside containing microemulsion, the high interfacial activity is attributable to the fact that the hydrophilic alkyl polyglycoside with the large polyglycoside head group is present in exactly the right mixing ratio with the hydrophobic co-emulsifier SML with its small head group at the oil/water interface. In contrast to ethoxylated nonionic surfactants, hydration and hence the effective size of the head group are hardly dependent on temperature [8,28,341, an attribute which can be utilized for formulating temperature-stable microemulsions 1351. Figure 27 shows by way of example the phase behavior of a system of dioctyl cyclohexane and water and also 15o!o of an emulsifier mixture of C,,,,,APG and glycerol monooleate (GMO).Irrespective of the temperature, the system forms transparent microemulsions or very fine-particle blue emulsions (particle size around 100 nm) of the o/w type, which was determined by measurement of the electrical conductivity, for CWM APG:GMO ratios of 60:40 to 75:25. In order to be able to use alkyl polyglycoside microemulsions for industrial or cosmetic applications, tailor-made formulations with certain desirable performance properties are necessary. Figure 28 shows the pseudoternary phase triangle of a five-component system of cosmetic raw materials which may serve as a model system for foaming and, at the same time, refatting body-care formulations [361.The water content is a constant 60 Yo, the oil component is dioctyl cyclohexane. In this example, the hydrophilic emulsifier used is a 5 : 3 mixture of alkyl polyglycoside and a fatty alcohol ether sulfate (FAES)which, as a highfoaming anionic surfactant, forms the basis of many body-care formulations. Although sorbitan monolaurate (SML) was chosen as the hydrophobic coemulsifier in this case, other co-emulsifiers, for example glycerol monooleate [351,are also suitable in principle. Accordingly, the indicated formulation in the blue o/w emulsion range contains 15% alkyl polyglycoside (C12/14 APG), 9 % FAES, 8 Yo SML, 8 Yo dioctyl cyclohexane and 60 Yo water. Temperature ['Cl 100

80 60 40

Figure 27. Phase behavior of the system water/dioctyl cyclohexane in a ratio of 1:l with 15% of mixtures of glycerol monooleate and C,,,,, APG [351

20

0

0 GMo

0.2

0.4

0.6

CGMOCApG + CAPG

I

0.8

1.0 APG

62

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

Starting out from an oil-free and co-emulsifier-free system, a 40% alkyl polyglycoside/FAES mixture in water is present as a viscous hexagonal liquid crystal (HIJ Even the replacement of a small part of the alkyl polyglycoside/ FAES mixture by the hydrophobic co-surfactant SML is sufficient to allow a low-viscosity lamellar phase (La)to be formed (Table 2). If the SML content is increased, the lamellar phase remains intact whereas the viscosity increases considerably and reaches levels which are even above those of the hexagonal phase. Like the hexagonal phase, the lamellar phases are also non-Newtonian, in other words their viscosity decreases with increasing shear rate (Table 2). The two liquid crystals react very differently to the addition of oil. Whereas the hexagonal liquid crystal is only capable of solubilizing very small quantities of oil, the existence range of the lamellar phase extends far towards the oil corner (Figure 28). The ability of the lamellar liquid crystal to incorporate oil increases distinctly with increasing SML content. Solubilizationof the oil leads to an increase in the lamellar layer spacing (from 9.7 nm to 11.9 nm where 20 Yo dioctyl cyclohexane is incorporated) which was measured by small angle X-ray scattering. Accordingly, the oil molecules are incorporated in the hydrophobic DOCH

H

101 c12/14 APG/ FAES = 5/3

20

40

60

80

100 SML

Concentration [wt.-%I

Figure 28. Pseudoternary phase diagram for emulsion systems of 60% water with dioctyl cyclohexane (DOCH), sorbitan monolaurate (SML) and sodium lauryl ether sulfate (FAES)/C,,,,, AF'G in a ratio of 3 5 at 25 "C 1311

63

PhysicochemicalProperties of Alkyl Polyglycosides

Table 2. Phase and viscosity behavior of selected systems (systems with a water content of 600/0at 25 "C, ref. [311) Alkyl polyglycoside/FAES/ SML/Dioctyl Cyclohexane

Phase

Repeat Distance h

Viscosity [Pa.sl at [l/sl / [1O/sI

25/15/0/0 22/14/4/0 10/6/24/0 10/6/16/8 10/6/8/16 5/3/16/16

HIa La La La o/w-ME w/'o-ME

61 70 97 119

113 /11 2.0/ 2.0 201 /19 151 /12 0.6/ 0.3 2.6/ 2.6

interior of the lamellar layers and not in the palisade layer parallel to the emulsifier molecules (for details, see [311). With relatively high percentage oil contents, blue emulsions or transparent microemulsions are formed. With a high percentage SML content (more than 50% in the emulsifier mixture), these emulsions are of the w/o type. For an optimal mixing ratio of hydrophilic alkyl polyglycoside/FAES compound to hydrophobic SML, the transparent microemulsion range extends very far towards the oil corner: at most 60% of dioctyl cyclohexane can be microemulsified. The microemulsions have low viscosities and are substantially Newtonian, the w/o microemulsions having slightly higher viscosities than the o/w microemulsions (Table 2). In conclusion, it may be said that alkyl polyglycoside microemulsions represent an interesting new application form for technical and especially for cosmetic uses. The future will show to what extent this new formulation concept will be accepted in practice. 5. Adsorption on solid surfaces

Similarly to the liquid/gas and liquidlliquid interfaces, surfactants also influence the interface of liquid systems with solid substrates by virtue of their amphiphilic structure. This affects many applications and, hence, may also be used for numerous processes. Examples are dispersions of solids in liquids [371, washing and cleaning processes [381 and the processing of ores [391. The systematic dependence of adsorption on the structure of nonionic surfactants was summarized in [401. In this case, the results apply predominantly to nonionic surfactants containing ethylene oxide groups. Hitherto, there have been very few investigations into the adsorption properties of alkyl glycosides on solids. Nickel et al. [411 report on the adsorption of alkyl glycosides to various types of solids and demonstrate a connection with the dispersion of solids. In those

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

64

investigations,the solids were selected so that, on the one hand, a broad spectrum of polarity would be guaranteed and, on the other hand, the adsorbents would have a sufficiently large surface: - Vulcan-3 carbon black (Cabot Corporation) was used as the hydrophobic surface;the particle size was 25 to 30 nm. BET measurements revealed a specific surface area of 69 m2g-'. A second hydrophobic adsorbent was a silica gel (Nucleosil-300) which had a specific BET surface area of 100 mzg-'and which had been hydrophobized by addition of octyl chains. - A mesoporous glass (Fluka) was used as a hydrophilic adsorbent. CPG-10 (controlled-pore glass) consists of substantially pure quartz glass with a narrow pore distribution. A sample with a pore radius of 24 nm and a specific BET surface area of 88 m2g-lwas used. Figure 29 shows the adsorption behavior of C,G, for graphitized carbon black at 22 "C. The adsorption isotherm is characterized by a very steep initial slope which did not enable adsorption to be measured at low surface coverages by any of the analytical methods available at the present time. This behavior is indicative of a high affinity of the alkyl glycosides for this solid surface. In addition to the adsorption curve, the theoretical monolayers are marked in flat and in vertical arrangements. For a flat arrangement of the molecule, the maximum monolayer concentration is 1.6.W moles m-2.If only the alkyl chain and the ether oxygen are adsorbed, which corresponds to a vertical arrangement,

70 -6050 40 3020 10.

-- -

- - - - - - - Cschains - -

120

-3 -2

-

.1

Figure 29. Adsorbed amounts madsof C,G, and surface concentration r of C,G, on graphitized carbon black as a function of the surfactant concentration in water at 22 "C [411

5

100

4

80

3

60 40 20

2 - - Molecule - - - - - - -

1

Figure 30. Adsorbed amounts madsof C,G, and surface concentration I- of C,G, on graphitized carbon black as a function of the surfactant concentration in water at 22 and 44 OC 1411

65

Physicochemical Properties of Alkyl Polyglycosides

the monolayer concentration is 3.2.10-6moles m-2.The first value is reached at a very low alkyl glycoside concentration of around 0.1 g/l. Thereafter the curve only climbs slightly and, in the concentration range investigated, does not approach the monolayer capacity for a vertical arrangement of the surfactant molecules. Figure 30 shows the corresponding curves for C,,G, at 22 "C and 44 "C. In the lower concentration range, the adsorption behavior is very similar to that of C,G,. The first limit is reached at an even lower concentration. In contrast to C,G,, the increase in the amounts adsorbed with higher concentration is more pronounced than in the case of the C,G, sample. In this case, the adsorption volume corresponding to a monomolecular layer with a vertical arrangement of the alkyl chain is exceeded at a concentration of around 0.15 g/l. The dependence of adsorption on temperature is very weakly pronounced. The 22 "C curve is slightly above the 44 "C curve. Comparison with the adsorption behavior of C,,E, on graphitized carbon black at three temperatures, as illustrated in Figure 31, shows clear differences between the surfactant types. A marked dependence on temperature in the upper concentration range can be seen for the fatty alcohol ethoxylate. In contrast to the alkyl glycosides, adsorption increases with higher temperature. The critical parameter for the dependence of the adsorption of C,,E, on temperature is clearly the cloud point (Tc=20 "C). The adsorption of C,,E, increases

0.1

0.2

0.3

Concentration

0.4

[ull

Concentration [g/ll

Figure 31. Adsorbed quantity madsof C,,E, and surface concentration r of C,,E, on graphitized carbon black as a

Figure 32. Adsorbed quantity madsof C,G, and surface concentration r of C,G, on Nucleosil-300 as a function of

function of the surfactant concentration in water at 19, 30 and 45 "C [411

25°C [411

the surfactant concentration in water at

66

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

dramatically at temperatures above T,. On the other hand, however, a C,E, with a cloud point of 40 "C also shows significantdependence of adsorption behavior on temperature below the cloud point [411. Adsorption on another hydrophobic surface, but with a different structure, is illustrated by the adsorption isotherms in Figure 32 which shows the curve for C,G, on Nucleosil-300 C-8. In contrast to adsorption on graphitized carbon black, the quantities adsorbed are smaller and the isotherms climb very uniformly over the entire concentration range investigated. These isotherms can be formally described by a Langmuir equation t421. Accordingly, the interaction between the solid surface and the adsorbed surfactant should be weaker than in the case of graphitized carbon black (Figure 29). Accordingly, adsorption on hydrophobic surfaces is clearly dependent upon the surface structure. The influence of surface structure is even clearer on hydrophilic surfaces. Smith et al. I431 studied the adsorption of technical alkyl polyglycosides with different chain lengths on titanium dioxide. It is known from adsorption studies that lauryl polyglycol ethers are not adsorbed onto the surface of titanium dioxide particles [441. The reason for this was assumed to be that the ether bonds of the nonionic surfactants preferentially enter into hydrogen bridge bonds with the unbound water molecules by comparison with the hydroxyl groups of the polar titanium dioxide surface. Alkyl glycosides show different behavior on polar solid surfaces. This is reflected in the adsorption isotherms of the following examples. Thus, alkyl polyglycosides are adsorbed onto a hydrophilic glass surface (Figure 33),although the amounts adsorbed are lower by a factor of about 100 than those adsorbed onto graphitized carbon black. A surface coverage with a close-packed monolayer is not remotely reached in the concentration range investigated below the cmc. This suggests that the alkyl glycoside molecules are

CIOG, /25 "C 3 '

0.2

Figure 33. Adsorbed amounts madsof 0.8 C,G, on CPG as a function of the surfactant concentration relative to the cmc 1411 Concentration/cmc

0.4

0.6

67

Physicochemical Properties of Alkyl Poiyglycosides

adsorbed as isolated individual molecules. There can be no associative interactions and hence no increased adsorption. Temperature also has only a slight influence in this adsorption system. Similarly to graphitized carbon black, the amounts adsorbed are slightly lower at relatively high temperatures. This figure shows the adsorption isotherms of C,G, and C,,G, on CPG-10 at two temperatures. In the interests of a better comparison, the concentration is plotted relative to the cmc. The adsorption isotherms of three technical alkyl polyglycosides on titanium dioxide are shown in Figure 34. In the identical concentration range investigated, the isotherm shapes differ in dependence upon the chain length of the alkyl polyglycoside mixtures. In the case of the short-chain C,,,, alkyl polyglycoside, the quantities adsorbed are almost linearly dependent on the concentration whereas a tendency towards a pronounced S form of the isotherms is observed with increasing alkyl chain length. A similar isotherm form is also observed for the adsorption of anionic surfactants onto polar solids, for example sodium dodecyl sulfate (SDS) onto titanium dioxide [451 and aluminium oxide [461. By way of explanation, it was stated in these examples that individual surfactant molecules with the polar head directed towards the surface are adsorbed by an acid/base interaction of the basic OH groups of the surface with the SDS anion. If the solution concentration of the surfactants is increased, two-dimensional aggregates-often referred to as “hemimicelles” r471-are formed via a hydrophobic interaction of the alkyl chains. This leads to a marked increase in the quantities adsorbed. A similar mechanism can also be postulated for the adsorption of alkyl polyglycosides with relatively long

mads

[mg/g]

,0 4 30

,

20 0

10 0

0.1

,;, ;; jl,

m a d s [rng/gl

,

0.3 0.5 0.7 Concentration [g/ll

0.1

,

,;

I

0.3

[mg/g] 40

0.5

20 30,,

,

~

,;;,

10

0.7

Concentration [g/ll

0.1

0.3 0.5 0.7 Concentration [g/ll

Figure 34. Adsorbed amounts madsof APG: a) C12/14 APG, b) Cg,ll APG, c ) CWIO APG on TI-PURE”R-960 as a function of the surfactant concentration in water at 25 “C [431

68

Dieter Nickel, Thomas Forster, and Wolfgang von Rybinski

alkyl chains. The hydroxyl groups of the surfactant have a slightly acidic character and are capable of entering into hydrogen bonds with the hydroxyl groups of the titanium dioxide surface. If a sufficient number of alkyl glycoside molecules is adsorbed onto the surface, other molecules are adsorbed onto the surface through an interaction of the alkyl chains. This leads to surfacecoverages above a theoretical monolayer which is confirmed by the adsorption measurements. Accordingly, the results on titanium dioxide clearly differ from the considerably lower adsorption of alkyl polyglycosides onto glass surfaces (see Figure 33). The effects of adsorption on the dispersion of pigments in aqueous solutions of alkyl polyglycosides and the rheology of dispersions were described by Nickel et al. [411 and by Smith et al. [431. References 1. D. Nickel, H.-D. Speckmann, W. von Rybinski, Tenside Surf. Det. 32 (1995) 470 2. G. Platz, J. Policke, Chr. Thunig, R. Hofmann, D. Nickel, W. von Rybinski, Langmuir 11 (1995) 4250 3. F. Nilsson, 0. Soderman, Langmuir 12 (1996) 902 4. P. Sakya, J. M. Seddon, R. H. Templer,J. Phys. 11Fr. 4 (1994) 1311

5. R. A. Mackay in Nonionic Surfactants; Physical Chemistry (M. J. Schick, ed.), Marcel Dekker, New York 1987, p. 297 6. G. Platz, Chr. Thunig, J. Policke, W. Kirchhoff, D. Nickel, Colloids and Surfaces A: Physicochem. Eng. Aspects 88 (1994) 113 7. D. E. Sadler, M. D. Shannon, P. Tollin, D. W. Young, M. Edmondson, P. Rainsford, Liq. Crist. 1 (1986) 509 8. K. Fukuda, 0.Soderman,B. Lindman, K. Shinoda, Langmuir 9 (1993)2921 9. D. Baker, Langmuir 9 (1993) 3375 10. M. J. Schick, J. Colloid Sci. 17 (1962) 801 11. R. Kjellander,J. Chem. SOC.Faraday Trans. 2 78 (1982) 2025 12. B. Lindman, G. Karlstrom, Z. Phys. Chem. N.F. 155 (1987) 199 13. L. Marzsall, Langmuir 4 (1988) 90 14. G. Platz, Chr. Thunig, H. Hofmann, Ber. Bunsenges. Phys. Chem. 96 (1992) 667 15. K. Shinoda, T. Yamaguchi, R. Hori, Bull. Chem. SOC.Jpn. 34 (1961) 237 16. Th. Bocker, J. Thiem, Tenside Surf. Det. 26 (1989) 318 17. D. Nickel, C. Nitsch, C.-P. Kurzendorfer, W. von Rybinski, Progr. Colloid Polym. Sci. 89 (1992) 249 18. F. Jost, H. Leiter, M. J. Schwuger, Colloid Polym. Sci. 266 (1988) 554 19. B. Y. Zhu, M. J. Rosen, J. Colloid Int. Sci. 99 (1984) 435 20. R. Hofmann, D. Nickel, W. von Rybinski, Tenside Surf. Det. 31 (1994) 63

Physicochemical Properties of Alkyl Polyglycosides

69

2 1. R. Miller, K. Lunkenheimer, Colloid Polym. Sci. 263 (1986) 273 22. E. M. Kutschmann, G. H. Findenegg, D. Nickel, W. von Rybinski, Colloid Polym. Sci. 273 (1995) 565 23. M. Kahlweit, R. Strey, Angew. Chem. 97 (1985)655 24. K. Shinoda, H. Kunieda in Encyclopedia of Emulsion Technology, Vol. 1 (P. Becher, ed.), Marcel Dekker, New York, 1983, p. 337 25. Th. Forster, W. von Rybinski, A. Wadle, Advances in Colloid and Interface Sci. 58 (1995) 119 26. G. G. Warr, C. J. Drummond, F. Grieser, B. W. Ninham, D. F. Evans,J. Phys. Chem. 90 (1986) 4581 27. W. D. Clemens, Ber. Forschungszentrum Jiilich 1994, 3028 28. D. Balzer, Tenside Surf. Det. 28 (1991) 419 29. M. Kahlweit, G. Busse, B. Faulhaber, Langmuir 11 (1995)3382 30. H. Kahl, K. Kirmse, K. Quitzsch, Tenside Surf. Det. 33 (1996) 26 3 1. Th. Forster, B. Guckenbiehl, H. Hensen, W. von Rybinski, Progr. Colloid Polym. Sci. 101 (1996) 105 32. G. H. Findenegg et al. to be published in Progr. Colloid Polymer Sci. 1996 33. R. Aveyard, B. P. Binks, P. D. I. Fletcher, Langmuir 5 (1989) 1210 34. R. Hofmann, D. Nickel, W. von Rybinski, G. Platz, J. Policke, Chr. Thunig, Progr. Colloid Polym. Sci. 93 (1993) 320 35. Th. Forster, B. Guckenbiehl, A. Ansmann, H. Hensen, Seifen, Ole, Fette, Wachse Journal 122 (1996) 746 30. Th. Forster, H. Hensen, R. Hofmann, B. Salka, Cosmetics Toiletries 110 (1995) 23 37. R. B. McKay, Technological Applications of Dispersions, Marcel Dekker, New York, 1994 38. M. J. Schwuger, J. Am. Oil Chem. SOC.59 (1982) 258 39. J. Leja, Surface Chemistry of Froth Flotation, Plenum Press, New York, 1982 40. W. von Rybinski, M. J. Schwuger in Nonionic Surfactants Physical Chemistry (M.J. Schick, ed.), Marcel Dekker, New York, 1987, p. 45 41. D. Nickel, W. von Rybinski, E. M. Kutschmann, C. Stubenrauch, G. H. Findenegg, Proceedings 4th World Surfactant Congress, Barcelona, June 1996, Vol 2, p. 371, Fett Lipid 98 (1996) in press 42. G. D. Parfitt, C. H. Rochester in Adsorption from Solution at the Solid/ Liquid Interface (R. H. Ottewill, ed.), Academic Press, London, 1983 43. G. A. Smith, A. L. Zulli, M. D. Grieser, M. C. Counts, Colloids Surf. A 88 (1994) 67 44. S. Fukushima, S. Kumagai,J. Colloid Int. Sci. 42 (1973) 539 45. C. Ma, Y. Xia, Colloids Surf. 68 (1992) 171 46. P. Chandar, P. Somasundaran, N. J. Tarro, J. Colloid Int. Sci. 117 (1987) 31 47. A. M. Gaudin, D. W. Fuerstenau, Trans AIME 202 (1955) 958

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH VerlagsgesellschaftmbH,1997

5. Alkyl Polyglycosides in Personal Care Products Holger Tesmann, Jorg Kahre, Hermann Hensen, and Barry A. Salka

Over the past decade, progress in the development of raw materials for personal-care products has mainly occurred in three areas: - mildness and care for the skin - high quality standards by minimization of by-products and trace impurities - ecological compatibility. At the same time, the variety of parameters to be tested for a new raw material has increased and their detection by subjective and objective methods has become more precise. Official regulations and the needs of the consumer have increasingly stimulated innovative developments which follow the principle of sustainability of processes and products. The use of renewable raw materials for the production of alkyl polyglycosides from vegetable oils and carbohydrates is one aspect of this principle. A life-cycle analysis has been published for the production of alkyl polyglycosides under European conditions (see Chapter 12) providing an overview of the energy and resource demands and the environmental emissions involved in the production of 1000 kg C12lI4 alkyl polglycosides [ll. The development of a commercial technology requires a high level of control of the raw materials and the reaction and working-up conditions to satisfy modern quality requirements for cosmetic raw materials at reasonable cost. In the cosmetic field alkyl polyglycosides represent a new class of surfactants which combine properties of conventional nonionics and anionics. By far the largest proportion of commercial products is represented by C,,, alkyl polyTable 1. Technical data of a l k y l polyglycosidesa' Plantacarem818

Plantacarea 1200 Plantaren@1200

INCI-Namebi COCOGlucoside Lauryl Glucoside Active substance (AS) 51-55% 50-53% pH value (20%) 11.5-12.5 11.5-12.5 Liquid Pasty Appearance (20%) Recommended 115°C 38-45 'C storage temperature Preservation None None a) See also Chapter 2, Table 1 b) Capital letters are used for INCI-names in the entire chapter.

Plantacare@2000 PIantaren@2OOO Decyl Glucoside 51-55% 11.5-12.5 Liquid

7O'c None

72

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

glycoside for cleansing formulations which are characterized by their skin and hair care properties. New applications are also reported where C,,,,, alkyl polyglycoside acts as an emulsifier in specific formulations and particularly in microemulsions. In addition, the performance of C,,,,, alkyl polyglycoside as a self-emulsifying o/w base blended with fatty alcohol is discussed. 1. Cosmetic cleansing formulations

At present, Henkel market three products under the brand names Plantacare and Plantaren for use in cosmetic cleansing formulations. Their composition (Table 1)is designed for optimum basic performance, such as foaming, viscosity and handling properties. 1.1 Dermatological properties

For body-cleansingformulations, a new modern surfactant must have excellent compatibility with the skin and mucous membranes. Dermatologicaland toxicological tests are essential for the risk assessment of a new surfactant and are designed above all to determine possible irritation of living cells in the basal layer of the epidermis (primary irritation). In the past, this was the basis for such claims as “mildness”of a surfactant. In the meantime, the meaning of mildness has changed considerably. Today, mildness is understood to be the all-round compatibility of a surfactant with the physiology and function of human skin, more precisely: the epidermis (see Chapter 10). The physiological effects of surfactants on the skin are investigated by various dermatological and biophysical methods starting with the surface of the skin and progressing via the horny layer and its barrier function to the deeper layer of the basal cells. At the same time, subjective sensations, such as the feeling on the skin, are recorded by verbalization of tactile sense and experience. Alkyl polyglycosides with C, to C,, alkyl chains belong to the group of very mild surfactants for body cleansing formulations. In a detailed study, the compatibility of alkyl polyglycosides was described as a function of the pure alkyl chain and the degree of polymerization [21. In the modified Duhring Chamber Test, C,, alkyl polyglycoside shows a relative maximum within the range of mild irritation effects whereas C,, C,, and C,,, C,, alkyl polyglycoside produce lower irritation scores. This corresponds to observations with other classes of surfactants. In addition, irritation decreases slightly with increasing degree of polymerization (from DP = 1.2 to DP = 1.65). On the other hand mucous membrane compatibility,as determined by the invitro test on the chorionallantois membrane of fertilized hens’ eggs (HET-CAM or CAM test, see also Chapter 9 )as an alternative to Drake’s mucous membrane

73

Alkyl Polyglycosides in Personal Care Products

compatibility test, shows a monotonic decrease from C, to C,, alkyl polyglycoside within the range of mild irritation. The DP causes only a slight differentiation of compatibility in this case. The commercial APG products (Plantacare/Plantaren 1200,Plantacare/Plantaren 2000 and Plantacare 818) with mixed alkyl chain lengths have the best overall compatibility with relatively high proportions of long-chain (C,,,,,) alkyl polyglycosides.They join the very mild group of highly ethoxylated alkyl ether sulfates, amphoglycinates or amphodiacetates and the extremely mild protein fatty acid condensates based on collagen or wheat protein hydrolyzates. Comparative tests have been carried out [3,41. Another in vitro test (RBC, Red Blood Cell Test) investigates the hemolysis of erythrocytes under the influence of surfactants. A so-called “mean index of ocular irritation” (MIOI)correlating sufficiently with the Draize test has been derived. For alkyl polyglycosides, the MI01 lies at very low values as it does for other very mild surfactants [5,61. Similarly, alkyl polyglycosides produce a very mild skin reaction in the modified Duhring Chamber Test [4,7,81. In mixed formulations with standard alkyl ether sulfate (Sodium Laureth Sulfate, SLES), the score for erythema decreases with increasing levels of alkyl polyglycoside without a synergistic effect being observed (Figure 1). A complete study of skin compatibility investigates surface conditions, the influence on the transepidermal water loss through the horny layer, dermatological parameters and subjective sensorial effects after surfactant application. This compilation test system also enables combination effects to be studied so that most compatible formulations can gradually be built up from basic surfactants, additives and special ingredients [81. A suitable test procedure is the arm flex wash test [91 which simulates the daily use of a product by open repeated application under accelerated condiRel. irritation score [%] 100

1 2 3 4 5

80 60 40

Sodium Laureth Sulfate

Decyl Glucoside

100 75 50 25 0

0 25 50 75 100

20

1

2

3

4

5

Figure 1. Modified Duhring Chamber Test with relative irritation scores for erythema formation

74

Holger Tesmann, Jorg Kahre, Hermann Hensen, and Barry A. Salka

tions [4,8,101. The condition of the skin surface can best be documented by a flexible microscope (see Chapter 10,Figure 6). A more detailed evaluation of a skin surface profile after application of alkyl polyglycoside is provided by profilometry. The various statistical parameters which differentiate roughness of the skin describe a skin smoothing effect for alkyl polyglycosides [5,8,111. The standardized mean swelling values (Q according to Zeidler) 1123 of the horny layer, as determined on isolated pig epidermis, lie in the swelling-inhibiting range. For C,,,,, alkyl polyglycoside (C,,,,, APG),Q values of -6% to -9% (+ 7 Yo with 95 010 confidence)were measured at pH 5.6. The lower swelling of the epidermis by an alkyl polyglycoside solution as compared with water is a sign of the functional compatibility of alkyl polyglycosides and contributes by way of compensation to limiting irritation mechanisms of other components in the formulation. In addition, on the basis of corneometer measurements [71, the loss of moisture content in the horny layer is lower by 30-40% under the effect of alkyl polyglycoside as compared with standard ether sulfate. This corresponds to the effect of the very mild zwitterionic amphodiacetates. The influence of surfactants on the barrier function of the epidermis either by deterioration of the functional structure or by elution of components (horny layer lipids, NMF) is characterized by evaporimeter measurements as a change of the natural transepidermal water loss ("EM). Investigations in connection with the arm flex wash test show that the changes in relation to the normal state of the skin barrier produced by standard surfactants are reduced in the presence of alkyl polyglycosides. This effect can be increased in the systematic build-up of formulations by incorporating further additives, such as protein derivatives [4,81. The dermatologicalfindings in the arm flex wash test show the same ranking as in the modified Duhring Chamber Test where mixed systems of standard alkyl ether sulfate and alkyl polyglycosides or amphoteric co-surfactants are investigated. However,the arm flex wash test allows better differentiationof the effects. Formation of erythema and squamation can be reduced by 20-30 Yo if around 25 o/o of SLES is replaced by alkyl polyglycoside (Figure 2). Of greater importance is the recording of subjective feelings of the volunteers (itching, stinging etc.) which indicates a reduction of about 600/0.In the systematic build-up of a formulation, an optimum can be achieved by the addition of protein derivatives or amphoterics [81. 1.2 Ecological properties

Alkyl polyglycosides have been extensively investigated with regard to their fate and effect in the environment [13,141 (see Chapters 11 and 12). The pre-

75

Alkyl Polyglycosides in Personal Care Products Erythema

Desquamation

Rel. irritation score

[%I

Sensory parameter

Rel. irritation score

[%I

Rel. irritation score

[%I

100

80 60

60

40

40

20

20 1

2

1

2

1

2

1 = Sodium Laureth Sulfate (SLES) 2 = Sodium Laureth Sulfate and Decyl Glucoside (3:l)

Figure 2. Skin effects in the arm flex wash test: dermatological assessment

scribed OECD method for detecting the biological primary degradation of nonionics is not applicable to alkyl polyglycosides because they do not contain any ethylene oxide groups and are thus not BAS-active. Nevertheless, it can be extrapolated from the very favorable ultimate degradation data that the primary degradation step also proceeds with ease. This was confirmed in the OECD Confirmatory Test by applying an alkyl polyglycoside specific analysis method. Ready ultimate biological degradation was observed with complete mineralization and/or assimilation of alkyl polyglycosides both under aerobic and under anaerobic conditions. In the Closed Bottle Test (OECD 301), the “ready biodegradability” criterion under aerobic conditions is fulfilled with the “ lo-day-window” requirement under which 60 Oo/ degradation must occur within 10 days of passing the 10Yo degradation level (Figure 3). The ultimate degradation of alkyl polyglycosides without residues and stable metabolites was confirmed in a modified Coupled-Units Test, the so-called “Test for Recalcitrant Metabolites”. In this test, the effluent of the test unit is circulated for about 6 weeks to detect possible accumulations of non-readily degradable substances [141. Under European standards, an overall evaluation of the environental risk of alkyl polyglycosides requires a realistic description of a scenario in which assessment of exposure in the environment of a substance (predicted environmental concentration) is compared with its effect in the environment (predicted no-effect concentration) H51. Such an evaluation leads to the conclusion that, even under unfavorable conditions, no environmental risk is involved in the use of alkyl polyglycosides.

Holger Tesmann,Jorg Kahre, Hennann Hensen, and Barry A. Salka

76

[%I 100

80 60

301 D (% BOD/COD) 301 E (% DOC removal) 301 A I% DOC removal) I

40

20 I

I

I

I

I

5

10

15

20

25

Figure 3. Biodegradation kinetics of C,,,

I

30 Timeid1

APG in standard tests

The ecotoxicological effects which, given rapid biodegradability of the substances, continue to lose relevance in an overall ecological risk assessment, show favorable findings in all test systems. The no-observed-effect concentrations (NOEC) for acute or chronic toxicity, as determined on single species or biocenotic communities of the aquatic and terrestrial environment, show that alkyl polyglycosides have comparatively low ecotoxicity [131. 2. Performance properties

2.1 Concentrates

Addition of alkyl polyglycosides modifies the rheology of concentrated surfactant mixtures so that pumpable, preservative-free and readily dilutable concentrates containing up to 60 O/o active substance can be prepared. These concentrated blends of several components may be generally used as cosmetic raw materials or specificallyas core concentrates in the production of cosmeticformulations (for shampoos,shampoo concentrates,foam baths, shower gels etc). Accordingly, the compositionswith alkyl polyglycosides are based on highly active anionics, such as alkyl ether sulfate (sodiumor ammonium salts),betaines and/or nonionic surfactants and as such are more gentle on the eyes and the skin than conventionalsystems.At the same time, they show excellent foam behavior, thickening behavior and processing properties. Super concentrates are preferred for economic reasons insofar as they are easier to handle and dilute without containing hydrotropes. The mixing ratio of the surfactant base is adapted to the performance requirements of formulations.

77

Alkyl Polyglycosides in Personal Care Products Viscosity [Pa,sl

100 j

I

10

20

-0

I

30

-40

50

60

70

80

Weight [%I

Figure 4. Rheology of Sodium Laureth Sulfate (SLES) and Plantacare 1200 (CWM APG) in admixture

A simple characteristic example is the compound of standard alkyl ether sulfate (for example Texapon@N70) and C,,,,,APG (Plantacare 1200) in a ratio of 2: 1 active substance (Plantacare PS 10). Alkyl polyglycoside disrupts the formation of the highly viscous hexagonal phase of the alkyl ether sulfate which, in turn, inhibits the crystallization of alkyl polyglycosides (Figure 4). The mixture is pumpable above 15 "C and can be cold-processed with normal mixing units (for example Ekato propeller). On dilution, viscosity passes through a flattened broad maximum at 40-45 Yo AS [3,161. 2.2 Formulation techniques

The nonionic class of alkyl polyglycosides differs from fatty alcohol ethoxylates by its characteristic structure which considerably affects the association of molecules in solution, the phase behavior and the interfacial activity. The hydrophilic head of the glucose ring, associated with the surrounding water molecules by hydrogen bonds is rather voluminous as compared to the alkyl chain. However, the hydration is low compared to fatty alcohol ethoxylates. Therefore, basic phenomena like cloud point, thermal phase inversion or gel formation in medium concentrations of pure solutions cannot be observed in case of the alkyl polyglycosides (see also Chapter 4).

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

78

The phase behavior of alkyl polyglycosides in aqueous solution gives important hints for the handling and formulation of a product in regard to viscosity, flow behavior and phase stability. The phase stability was investigated in pure solutions and systemsmixed with alkyl ether sulfate, alkyl sulfate,alkyl sulfate/ fatty alcohol. The phase diagram of C12/14 APG shows the main important characteristics (see Chapter 4, Figure 3). The Krafft temperature of a fresh solution of c12/14APG in water is approximately 20 to 22 "C at low concentration and increases to about 37 "C during storage time. Below the Krafft temperature a highly viscous dispersion of crystals and brine exists, whereas above a clear micellar solution exists (L1)in a wide range of concentration without lamellar phases. The consistency of the L1 phase is like honey and shows Newtonian flow behavior. At low concentration the micellar solution is limited by a two-phase area (w + L1)where a surfactant rich and a water rich phase coexist (coacervate).The area of coacervates is enlarged towards lower temperature and higher concentration, if electrolytes are added. It is destroyed by addition of anionics. Similarly, the Krafft temperature decreasesin the presence of ionic or other nonionic surfactants, so that neither phase separation by coacervate formation nor crystallization is observed at concentrations typically used in cleansing formulations. Foaming is an essential quality feature of cosmetic cleansing formulations. Alkyl polyglycosides foam considerably better than fatty alcohol ethoxylates, the foam volume increasing with increasing percentage of short carbon chains in the alkyl polyglycosides. They are comparable with betaines and sulfosuccinates but do not match the initial foam behavior or foam volume of alkyl (ether) sulfates,such as sodium lauryl ether sulfate (SLES;INCI-name: Sodium Laureth + AfterI 30 sec IAfter 20 min

Foam [mll

400 1

300 200 100

Lauryl

COCO

Glucoside

Glucoside

Decyl Glucoside

SLES

Cocamido-

Sulfo-

propyl betaine succinate

Cocoamphoacetate

Figure 5. Foaming properties of surfactants (1 g ASA, 15 "dH, 0.1 g/I sebum, perforated disc method DIN 53 902)

79

Alkyl Polyglycosides in Personal Care Products

Sulfate, sometimes referred to as fatty alcohol ether sulfate, FAES) [3,4,5,7,101 (Figure 5). On the other hand, alkyl polyglycosides can stabilize the foam of anionics in hard water and in the presence of sebum so that up to 200!0of total surfactant can be saved for the same foaming power [3,4,71. The structure of the foams of alkyl ether sulfates and alkyl polyglycosides was investigated by image analysis and provides a basis for understanding the observed properties [4,71. Alkyl polyglycoside foam consists of finer bubbles and is more creamy than Sodium Laureth Sulfate foam (Figure 6). Alkyl polyglycosides with alkyl chains longer than C,, contribute readily to the build-up of rodlet-like mixed micelles in solutions of anionics and thus make a considerable contribution towards increasing viscosity [4,101(Figure 7). This effect on the one hand is somewhat weaker in standard ether sulfate formulations than with alkanolamides, but on the other hand is more pronounced with sulfosuccinates and highly ethoxylated alkyl ether sulfates which are very difficult to thicken with alkanolamides. Alkyl polyglycoside formulations without anionics can best be thickened by adding polymeric thickeners, such as xanthan gum, alginate, polyethoxylated esters, carbomers etc.

2.3 Cleansing effect The cleansing properties of surfactants can be compared in a fairly simple test. Pig epidermis which has been treated with a mixture of sebum and soot is washed with a 3 010 solution of a surfactant for two minutes. Under a microLauryl Glucoside

Fine Wet

Spherical Stable

Sodium Laureth Sulfate

Coarse Dry

0 0

Polyhedral Unstable

Figure 6. Foam structure of surfactants after 15 minutes (magnification 30 x)

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

.

A

= 0

Sodium Laureth Sulfate + Lauryl Glucoside

+ Decyl Glucoside + COCOGlucoside

Figure 7. Increase of viscosity by alkyl polyglycosides (100/0AS SLES and 3 Yo AS alkyl polyglycoside at 25 "C)

scope, the grey value is determined by digital image analysis and compared with untreated pig epidermis. This method leads to the following ranking of cleansing properties: the best effects are produced by Lauryl Glucoside and the worst by Cocoamphoacetate. Betaine, sulfosuccinate and standard alkyl ether sulfate are in the middle range and cannot be significantly differentiated from one another. Only Lauryl Glucoside achieved a deep pore cleansing effect in this low concentration. Using a Schrader skin washing machine, tests were carried out on the forearms of volunteers [5,61. By applying a model soil containing dyes, Decyl Glucoside was found to have a poorer cleansing effect than typical anionics or betaines, although it still performed satisfactorily under in-use conditions. 2.4 Effects on hair

The mildness of alkyl polyglycosides towards the skin is also reflected in a caring effect on damaged hair. The tensile strengths of permed hair tresses are reduced far less by treatment with alkyl polyglycoside solutions than by standard ether sulfate solutions [4,71. By virtue of these caring properties and their alkali stability, alkyl polyglycosides are also suitable as surfactants in coloring, permanent-waveand bleaching formulations.Investigationsof permanent-wave formulations revealed that the addition of alkyl polyglycosides favorably influences the alkali solubility of the hair and the waving effect U71. Direct proof of the adsorption of alkyl polyglycosides onto hair can be qualitatively provided by the X P S technique (X-ray photoelectron spectroscopy).Hair tresses were divided into two halves which were respectivelysham-

81

Alkyl Polyglycosides in Personal Care Products

pooed with 12 010 AS surfactant solutions of Sodium Laureth Sulfate and Lauryl Glucoside at pH 5.5 and then rinsed and dried. Both surfactants can be detected on the hair surface by XPS. The oxygen signals of the keto and ether functions are increased by comparison with the untreated hair. Because this method is very sensitive even to small amounts of adsorbed material, shampooing and rinsing just once is not sufficient to differentiate between the two surfactants. However, if the process is repeated four times, no change in the X P S signals is observed in case of Sodium Laureth Sulfate by comparison with the untreated hair. By contrast, slightly increased oxygen contents and an increase in the keto functionality signals are measured for Lauryl Glucoside. This result shows that alkyl polyglycoside is more substantive to the hair than standard ether sulfate. The substantivity of surfactants to hair influences combability. Measurements of shampoo formulations on wet hair by objective methods (combing robot) and subjective methods (half-head test) showed that alkyl polyglycoside does not significantly reduce wet combability. However, a synergistic reduction in wet combability of about 50 Yo was observed in the case of mixtures of alkyl polyglycosides with cationic polymers. By contrast, dry combability is considerably improved by alkyl polyglycosides. Increased interactions between the single hair fibers provide the hair with volume and manageability [4,71. The increased interactions and film-forming properties also contribute towards styling effects. All-round bounce makes the hair appear vital and dynamically aesthetic. The bounce behavior of a hair curl can be determined in an automated test arrangement (Figure 8)which investigates the torsional properInductive force transducer

Amplifier

Computer

1 F “IN1 3

\ ‘i

2

\

\

Curl

1

0 -1 -2

-3

Figure 8. Characterization of hair curl oscillations

1

2

3

4

5 6 Time [sl

82

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

ties of hair fibers (bending modulus) and hair curls (stretch forces, attenuation, frequency and amplitude of oscillation).The hair curl is stretched by the release rod and the force function of the free attenuated oscillation is recorded by a measuring instrument (inductiveforce transducer) and processed by a computer. Styling products multiply the interactions of the individual hair fibers and lead to increased stretching work, amplitude, frequency and attenuation values of the curl oscillation. Formulations of alkyl polyglycosides and protein hydrolyzate are as effective in regard to bounce and manageability as a 2 Yo solution of polyvinyl pyrrolidone (PVP) [31 which is the conventional basis for hair spray formulations and setting lotions. From the practical point of view, easy rinsing of these products may also be an advantage over PVP formulations. The effect of alkyl polyglycosides in setting lotions is further demonstrated by curl retention as compared with a water wave. Hair tresses on curlers are respectively treated with water and a setting lotion. After the treatment, the tresses are left hanging under their own weight in a chamber with controlled relative humidity (rH). The change in overall length after 6 hours is used as a measure of curl retention. The combination of Lauryl Glucoside and Hydrolyzed Collagen is equivalent to the PVP formulation with 75 % curl retention at 70% rH [31. In rinses and conditioners based on fatty alcohol and quaternary ammonium compounds, the synergism of alkyl polyglycoside/quaternary ammonium compound (QUAT) is favorable in reducing wet combability whereas dry combability is only slightly reduced in these applications. Oil components may also be incorporated in the formulations, further reducing the necessary QUAT content and imparting improved luster to the hair. Such o/w emulsions may be used as “rinse-off or “leave-on”preparations for the aftertreatment of hair [31. 3. Cosmetic emulsion preparations

The solubilizationof comparably small amounts of oil components in rinse and shampoo formulations demonstrates the basic emulsification properties which alkyl polyglycosides should be expected to show as nonionic surfactants.However, a proper understanding of phase behavior in multicomponent systems is necessary in order to evaluate alkyl polyglycosides as powerful emulsifiers in combination with suitable hydrophobic coemulsifiers [161. In general, the interfacial activity of alkyl polyglycosides is determined by the carbon chain length and, to a lesser extent, by the degree of polymerization (DP).Interfacial activity increases with the alkyl chain length and is at its highest near or above the CMC with a value below 1 mN/m. At the waterlmineral oil interface, C,,,,, APG shows lower surface tension than C,,,,, alkyl sulfate [181.

83

Alkyl Polyglycosides in Personal Care Products

Interfacial tensions of n-decane, isopropyl myristate and 2-octyl dodecanol have been measured for pure alkyl monoglucosides (C8, C,,, CJ and their dependence on the solubility of alkyl polyglycosides in the oil phase has been described [191. Medium-chain alkyl polyglycosides may be used as emulsifiers for o/w emulsions in combination with hydrophobic coemulsifiers [201. Alkyl polyglycosides differ from ethoxylated nonionic surfactants in that they do not undergo temperature-induced phase inversion from oil-in-water (o/w) to water-in-oil (w/o) emulsions. Instead, their hydrophiWlipophilic properties can be balanced by mixing with a hydrophobic emulsifier, such as glycerol monooleate (GMO)or sorbitan monolaurate (SML). In fact, the phase behavior and interfacial tension of such alkyl polyglycoside emulsifier systems closely resemble those of conventional fatty alcohol ethoxylate systems if temperature is replaced as a key phase behavior parameter by the mixing ratio of the hydrophilic/lipophilic emulsifiers in the non-ethoxylated system [211. The system for dodecane, water, Lauryl Glucoside and Sorbitan Laurate as a hydrophobic coemulsifier forms microemulsions at a certain mixing ratio of C12/14 APG to SML of 4:6 to 6:4 (Figure 9). Higher SML contents lead to w/o emulsions whereas higher alkyl polyglycoside contents produce o/w emulsions. Variation of the total emulsifier concentration results in a so-called “Kahlweit fish” in the phase diagram, the body containing three-phase microemulsions and the tail single-phase microemulsions, as observed with ethoxylated emulsifiers as a function of temperature (see Chapter 4). The high emulSML [%I in APG/SML-mixture SML1.0-

O 8-

Interfacial tension [mN/rnl

&”+,$& ’

a,cfr a%

%z&

w+o

01:

0.4-

APG 0.

’

0

2

4

6

8

10

0.001 0

APG Total emulsifier conc.

[%I

02

0.4

0.6

08

10 SML

SML in APG/SML mixture [%I

Figure 9. Phase behavior and interfacial tension of a Lauryl Glucoside (C12/14 APGV Sorbitan LaurateIDodecane mixture in water (C12H26: water = 1:1 at 25 “C)

84

Holger Tesmann, Jorg Kahre, Hermann Hensen, and Barry A. Salka

sifying capacity of the C12/14APG/SML mixture as compared with a fatty alcohol ethoxylate system is reflected in the fact that even loo/, of the emulsifier mixture is sufficient to form a single-phase microemulsion. The similarity in the pase inversion pattern of both surfactant types is not limited to phase behavior, but can also be found in the interfacial tension of the emulsifying systems. The hydrophilic-lipophilic properties of the emulsifier mixture are balanced at an C12/~4 APG/SML ratio of 4:6 where interfacial tension is at its lowest. It is remarkable that a very low minimum interfacialtension (around mN/m) is observed with the C I ~APG/SML, / ~ ~ mixture. In the case of alkyl polyglycoside containing microemulsions, the high interfacial activity is attributable to the fact that the relatively hydrophilic alkyl polyglycoside with its large glucoside head group is mixed in the ideal ratio with a hydrophobic coemulsifier having a smaller head group at the oil-water interface. In contrast to ethoxylated nonionic surfactants,hydration (and hence the effective size of the head group) is not too much temperature-dependent. Accordingly, paralleling interfacial tension, only a slight dependence on temperature is observed for the phase behavior of the non-ethoxylated emulsifier mixture t211. This provides for interesting applicationsbecause, in contrast to fatty alcohol ethoxylates, temperature-stable microemulsions can be formed with alkyl polyglycosides. By varying the surfactant content, the type of surfactant used and the oillwater ratio, microemulsions can be produced with custom-made performance properties, such as transparency, viscosity, refatting effect and foaming behavior. In mixed systems of for example alkyl ether sulfates and nonionic coemulsifiers, extended microemulsion areas are observed and may be used for the formulation of concentrates or fine-particle o/w emulsions [ 16,211. An evaluation has been made of pseudoternary phase triangles of multicomponent systems containing alkyl polyglycoside/SLES and SML with a hydrocarbon (Dioctyl Cyclohexane) [161 and alkyl polyglycoside/SLES and GMO with polar oils (Dicaprylyl Ether/Octyl Dodecanol) [211. They demonstrate the variability and extent of areas for o/w, w/o or microemulsions for hexagonal phases and for lamellar phases in dependence upon the chemical structure and mixing ratio of the components.If these phase triangles are superimposed on congruent performance triangles indicating for example foaming behavior and viscosity properties of the corresponding mixtures, they provide a valuable aid for the formulator in finding specific and well-designed microemulsion formulations for e. g. facial cleansers or refatting foam baths. As an example, a suitable microemulsion formulation for refatting foam baths can be derived from the phase triangle in Figure 10. The oil mixture consists of Dicaprylyl Ether (CS-O-CS)and Octyl Dodecanol in a ratio of 3:1. The hydrophilic emulsifier is a 5:3-mixture of COCO Glucoside

Alkyl Polyglycosides in Personal Care Products

85

( c 8 - 1 4 APG) and Sodium Laureth Sulfate (SLES). This high-foaming anionic surfactant mixture forms the basis of many body cleansing formulations. The hydrophobic coemulsifier is Glyceryl Oleate (GMO).The water content is kept constant at 600/0. Starting from an oil- and coemulsifier-free system, a 40% c 8 - 1 4 APG/SLES mixture in water forms a hexagonal liquid crystal (HIa).The surfactant paste is highly viscous and non-pumpable at 25 "C. Only a fraction of the C8-14 APG/SLES mixture needs be replaced by the hydrophobic cosurfactant GMO to obtain a lamellar phase of medium viscosity (La, point (a) with a value of 23,000 m P a s at 1 s-'). In terms of practical application, this means that the high-viscosity surfactant paste changes into a pumpable surfactant concentrate. Despite the increased GMO content, the lamellar phase remains intact. However, the viscosity increases significantly and reaches levels for the liquid gel which are even above those of the hexagonal phase. In the GMO corner, the mixture of GMO and water forms a solid cubic gel. When oil is added, an inverse hexagonal liquid (H,J is formed with water as the internal phase. The hexagonal liquid crystal rich in surfactants and the lamellar liquid crystal differ considerably in their reactions to the addition of oil. Whereas the hexagonal liquid crystal can only take up very small quantities of oil, the

Dicaprylyl Ether/Octyl Dodecanol = 3/1

SLES = 5/3

GMO

-

Figure 10. Pseudoternary phase triangle of a 6-component system (60% water, 25 "C)

86

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

lamellar phase area extends far towards the oil corner. The capacity of the lamellar liquid crystal to take up oil clearly increases with increasing GMO content. Microemulsions are only formed in systems with low GMO contents. An area of low-viscosity o/w microemulsions extends from the CB-14 AI'GISLES corner along the surfactant/oil axis up to an oil content of 14940. At point (b), the microemulsion consists of 24 Yo surfactants, 4 010 coemulsifier and 12010 oil, representing an oil-containing surfactant concentrate with a viscosity of 1600 mF'asat 1 s-,. The lamellar area is followed by a second microemulsion are at point (c).This microemulsion is an oil-rich gel with a viscosity of 20,000 m P a s at 1 s-' (12O/o surfactants, 8 Oo/ coemulsifier,20 010 oils) and is suitable as a refatting foam bath. The c8-14APG/SLES mixture contributes towards cleansing performance and foam while the oil mixture acts as a refatting skin-care component. In order to obtain a refatting effect with a microemulsion, the oil must be released, i. e. the microemulsion must break up during application. A microemulsion of suitable composition breaks up during rinsing-off when it is heavily diluted with water, thus releasing the oil for refatting effects on the skin. In conclusion,it may be said that microemulsions can be produced with alkyl polyglycosides in combination with suitable coemulsifiers and oil mixtures. They are distinguished by their transparency and by their high temperature stability, high storage stability and high solubilizing capacity for oils. The properties of alkyl polyglycosides with relatively long alkyl chains (C16 to C,,) as o/w emulsifiers are even more pronounced. In conventional emulsions with fatty alcohol or glyceryl stearate as coemulsifier and consistency regulator, long-chain alkyl polyglycosides show better stability than the medium-chain c,,,,,APG described above. Technically, the direct glycosidation of C, fatty alcohol leads to a mixture of C,, alkyl polyglycoside and cetearyl alcohol from which cetearyl alcohol cannot be completely distilled off by usual techniques to avoid color and odor deterioration (see Chapter 2). Utilizing the residual cetearyl alcohol as co-emulsifier, self-emulsdying o/w bases containing 20-600/0 C,,, alkyl polyglycoside are the most suitable in practice for formulating cosmetic cremes and lotions based entirely on vegetable raw materials. Viscosity is easy to adjust through the amount of C,,, alkyl polyglycoside/ cetearyl alcohol compound and excellent stability is observed, even in the case of highly polar emollients, such as triglycerides [221. 4. Miscellaneous applications

By a special process based on brief exposure to high temperatures (flash drying), a water-containing paste of C,,,,, APG can be converted into a white non-caking

Alkyl Polyglycosidesin Personal Care Products

87

alkyl polyglycoside powder with a residual moisture content of about 10/0 1231. Alkyl polyglycosides may thus also be used in soaps and syndets. They exhibit good foam and skin feel properties and, by virtue of their excellent skin compatibility, represent an attractive alternative to conventional syndet formulations based on alkyl sulfates. Similarly, C, APG may be used in toothpastes and other oral hygiene formulations. Alkyl polyglycoside/fatty alcohol sulfate combinations show improved mildness towards oral mucous membrane and, at the same time, produce a rich foam. C,,,,, APG was found to be an effective booster for special antibacterial agents, such as chlorohexidine. In the presence of alkyl polyglycoside, the quantity of bactericidal agent can be reduced to about one quarter without losing any bactericidal activity. This provides for the everyday use of high-activity products (mouth washes) which would otherwise be unacceptable to the consumer because of their bitter taste and their discoloring effect on the teeth 1241. 5. Formulations

By virtue of their physicochemical and performance profile, alkyl polyglycosides are a class of products which represent a new concept in compatibility and care in cosmetics. Alkyl polyglycosides are multifunctional raw materials which are moving closer to the centre of modern formulation techniques. They may advantageously be combined with conventional components and can even replace them in new types of formulations. To exploit the rich spectrum of supplementary effects of alkyl polyglycosides on the skin and hair, changes have to be made to conventional techniques involving the widely used alkyl (ether) sulfate/betaine combinations. 5.1 Alkyl polyglycoside and betaine

In a comparison of two formulations containing alkyl polyglycoside and betaine as primary surfactants by the half-head test involving 10 volunteers, formulations 1 and 2 (Table 2 ) were evaluated in regard to initial foam, foam volume and feel. Although the results obtained were comparable, alkyl polyglycosides are preferred to betaines for their skin compatibility. In another test, formulations 3 to 6 were compared for their hair-conditioning performance. It is well-known that combinations of betaine and QUAT only provide conditioning effects in the presence of anionic surfactants. Neither alkyl polyglycosides on their own nor the addition of betaine leads to any reduction in wet combability (formulations 3 and 5). However, in combination with cationic substances, alkyl polyglycosides significantly reduce wet comb-

88

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

Table 2. Formulations of alkyl polyglycosides and betaine

No.

1 ~~~~

~

INCl declaration

Decyl Glucoside Cocamidopropyl Betaine Sodium Laureth Sulfate PEG55 Propylene Glycol Oleate

Polyquaternium-10 Water, preservative pH value Residual wet combability [%I

2

3

4

5

6

24.0 10.0

24.0

~

AS

[wt.-%l

[%I

55 30 30 30

20.0 -

7.0 3.0

33.3 7.0

24.0 -

3.0

-

24.0

-

10.0

-

-

-

-

0.3 0.3 ad 100 ad 100 ad 100 ad 100 ad 100 ad 100 5.5 5.5 5.5 5.5 5.5 5.5 -

-

-

-

-

120

47

98

57

ability with or without addition of betaines (formulations 4 and 6).To provide alkyl polyglycoside containing formulations with conditioning properties, any of the usual cationic materials may be used, including for example cationic proteins, cationic cellulose and guar derivatives, Polyquaternium types, etc. 5.2 Subjective assessment and acceptance of shampoos

The performance of shampoo formulation 7 under home-use conditions was judged by 8 volunteers to be good to excellent in regard to consistency, distribution on the skin and hair, initial foam, foam volume and rinse-out behavior (Table 3). In wet hair, the formulation was characterized as soft and readily combable. Its feeling on the skin was described as pleasant. Formulation 8 containing Plantacare 1200 as primary surfactant was compared with one of the new successful shampoos on the market in a salon test. Initial foam, the feeling in the hair, the feeling of the foam in the hand, the appearance of the foam and rinse-out behavior were evaluated by five experts. The market product was found to be very dull, above all in wet hair and on wet skin. The foam produced by formulation 8 was slightly unstable but visually finer and more uniform. All other parameters were found to be comparable. This comparison test is conclusive in that it is possible to develop a product containing a very mild surfactant combination and a large amount of Plantacare 1200 which is entirely comparable in its performance with leading market products. This can be shown in a half-head test with formulation 9 which was compared with another successful market shampoo.

Alkyl Polyglycosides in Personal Care Products

89

Table 3. Shampoo 7

No. INCl declaration Lauryl Glucoside Cocamidopropyl Betarne Hydrolyzed Almond Protein Xanthan Gum Disodrum Laureth Sulfosucctnate Laureth-2 Polyquaternium-10 Potassium Cocoyl Hydrolyzed Collagen Water, preservative pH value

AS [%I

9

[A:%]

50

8.0

30 22

27.0 2.0 1.0

40

-

30

8

12.0 7.0

ad 100 5.5

0.2 6.0 ad 100 5.5

12.0 7.0

8.0 1.5

0.2 ad 100 5.5

In addition to the use of alkyl polyglycosides in very mild formulations for frequent use, alkyl polyglycosides can be also used with advantage in special products for greasy hair and fine hair. In this case, a mild surfactant base is combined with special hair-care ingredients which do not challenge the hair. One such product is represented by formulation 10 (Table 4).Wet hair is easy to comb while dry hair shows volume and managability. A special protein deriva-

Table 4. Shampoo for fine, greasy hair No. INCl declaration Decyl Glucoside Sodium Laureth Sulfate Cocamidopropyl Betarne Potassium Abietoyl Hydrolyzed Collagen Laureth-2 Sodium Chloride Polyquaternium-10 Water, preservative pH value Residual wet cornbability [%I Residual dry cornbability [%I

10

AS [%I

[wt.-%l

55 30

10.0 14.3 10.0 5.1

30 31

1.0 1.0 0.2 ad 100 5.5

60.0 180.9

90

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

Table 5. Baby Shampoo

No. INCl declaration Sodium Laureth Sulfate (and) Lauryl Glucoside Cocamidopropyl Betaine Laurdimonium Hydroxypropyl Hydrolyzed Wheat Protein Polyquaternium-10 Laurethd Water, preservative pH value

Irritation score (HET-CAM1 Irritation score (HET-CAM) standard

11 AS

[%I

60 30 35

[Wt.-%l 12.0 14.0 3.0 0.1

3.0 ad 100 5.5

0.58 0.87

tive (PotassiumAbietoyl Hydrolyzed Collagen)serves as an effective ingredient against refatting of the hair. This was confirmed by objective measurements (shadow imaging method) and by a salon test [251. Another important speciality application are baby-care shampoos which utilize the excellent dermatological compatibility of alkyl polyglycosides as a surfactant base in combination with other mild ingredients. For conditioning effects, incorporation of a cationic wheat protein hydrolyzate has a remarkably low irritation potential in the hens’ egg test (HET-CAM).Formulation 11 (Table 5) is one example of such a product. It shows significantly improved in vitro mucous membrane compatibility by comparison with a well-known market product which has been used as a standard for years. The two formulations are comparable in their foam properties and conditioning effects. 5.3 Shower baths

The feeling on the skin of shower baths and gels is an important factor in consumer acceptance. A pleasant feeling on the skin can be achieved with the same conditioning agents as described for shampoos. Formulations 12 and 13 (Table 6)represent examples of such products. They were evaluated in a test against a market standard involving 8 volunteers. The feeling on the skin in both the wet state and the dry state was assessed on a six-stage scale (from pleasant to dry). The market product achieved an average score of 2.8 while formulations 12 and 13 achieved an average score of 2.1.

Alkyl Polyglycosides in Personal Care Products

91

Table 6. Shower baths No.

12

AS [%I

INCl declaration Sodium Laureth Sulfate Decyl Glucoside Cocamidopropyl Betaine Laurdirnonium Hydroxypropyl Hydrolyzed Wheat Protein Guar Hydroxypropyl Trirnonium Chloride PEG-7 Glyceryl Cocoate Glycol Distearate (and) Laureth-4 (and) Cocarnidopropyl Betaine Laureth-2 Sodium Laureth Sulfate (and) Lauryl Glucoside Water, preservative pH value

30 55 30 35

45

60

13 [Wt.-%I

25.0

6.0 10.0 2.0 0.5 1.0 3.0 1.0

10.0 2.0 -

2.0

20.0 ad 100 ad 100 5.5 5.5

An interesting concept for the highly regarded “shower and lotion” products is the incorporation of oil-containing emulsions in a surfactant base. The skin-care effect of such formulations can be evaluated, for example, by determination of the transepidermal water loss (TEWL).A market product and formulation 14 (Table 7 )were applied to the inside of the right and left forearms of 10 Table 7. Shower bath “shower and lotion” No. INCl declaration Sodium Laureth Sulfate Lauryl Glucoside Polyglyceryl-2-PEG-4Stearate Octyl Dodecanol Ceteareth-20 Sodium Chloride Water, preservative pH value Rel. TEWL Rel. TEWL (standard)

14 AS [%I

[Wt.-%]

30 50

22.0 16.0 4.0 3.0 1.0 0.4 ad 100 5.5 1.1 g/rn*h 1.75 g/m2h

92

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

Table 8. Exfoliating shower bath 15

No.

INCl declaration Decyl Glucoside Texapon @ASV, Henkel Sodium Laureth Sulfate Flora Beads Jojoba 40/60 Jade, Rovi Flora Beads Jojoba 28/60 Sapis, Rovi Flora Beads Jojoba 40/60 Gypsyrose, Rovi Xanthan Gum Water, preservative pH value

AS

[%I

55 30 30

17

Iwt.-%l 20.0 6.7 1.0 -

2

16

50.0 ad 100 5.5

20.0 6.7 1.0 50.0 ad 100 5.5

20.0 7.2 1.0 50.0 ad 100 5.5

volunteers. One hour after the treatment, the TEWL was measured with an evaporimeter. The TEWL value of formulation 14 is better than that of the market product. The two products differ from one another with a statistical significance of 95 O h . With regard to convenience, satisfaction and reuse, the two products were judged to be equal. 5.4 Peeling preparations

Shower baths with peeling properties, a new market trend, can also be formulated with alkyl polglycosides. Soft abrasive particles, such as hardened jojoba wax, walnut bark, cellulose granules, apricot kernels etc., are incorporated to remove scales and to achieve a specific feel. In addition, the abrasive particles promote circulation through a gentle massaging effect on the skin. The exfoliating effect must be carefully adapted to the type of skin and the specific consumer group and can best be evaluated by a panel test. The forearm is washed and foaming properties, exfoliating effects and the appearance of the products are assessed. Formulations 15 to 17 (Table 8 ) are clear formulations with good initial foam, a creamy feel and a slight to medium exfoliating effect. 5.5 Bath oils (microemulsion)

Good foaming and refatting performance characterize an alkyl polyglycoside microemulsion which is mild to the skin (Table 9, formulation 18) and which breaks up through dilution on application.

93

Alkyl Polyglycosides in Personal Care Products

Table 9. B a t h oil 18

No. INCl declaration

AS

[%I

[wt.-%l

50 55

Lauryl Glucoside Decyl Glucoside Glyceryl Oleate Dicaprylyl Ether Octyl Dodecanol Citric acid Water, preservative DH value

23.3 15.1 6.0 28.0 7.0

0.8 ad 100

5-6

5.6 Facial cleansers

Facial cleansers are speciality formulations. The dermatological properties of alkyl polyglycosides and their good deep pore cleansing effects commend them for use in many types of clear formulations, for example 19 to 21 (Table lo), utilizing the phase behavior of medium- and long-chain alkyl polyglycosides. Table 10. Facial cleanser 19

No. INCl declaration Lauryl Glucoside Sodium Laureth Sulfate Cocoamphodiacetate Carbomer Aloe Vera Hydrolyzed Wheat Protein Panthenol Allantoin Polyquaterniurn-10 Sodium Chloride PEG-7 Glyceryl Cocoate Glycerol Cetearyl Alcohol Cetearyl Glucoside Water, preservative

AS

[%I

50

30 30

40

50

21

[wt.-%l 10.0 3.6 -

-

0.5 0.2 0.2 -

86

20

12.0 2.0 1.5 0.8 0.2

10.0 -

-

0.2 0.1

1.0

-

-

-

5.0 3.0 12.0 3.0

ad 100

ad 100

-

ad 100

94

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

Table 11. Hair rinse

22

No.

INCl declaration

AS [%I

[Wt.-%l

50

2.0 3.5

Lauryl Glucoside Dipalrnitoyl Hydroxyethylrnonium Methosulfate (and) Cetearyl Alcohol Cetearyl Alcohol Glyceryl Stearate Octyl Dodecanol Water, preservative pH value

0.5 0.5 1.0 ad 100 3.5

5.7 Alkyl polyglycosides in hair aftertreatments

For the same reasons and by virtue of their positive influence on combability, coupled with the fact that they may readily be combined with cationic compounds, alkyl polyglycosides can be formulated as the basis of rinses and conditioners. Formulation 22 (Table 11) is one example of such products. In combination with an esterquat as a conditioner, alkyl polyglycosides can be used to develop rinses based on vegetable materials.

Table 12. Styling gel 23

No. ~~

INCl declaration

AS

[%I

Lauryl Glucoside Hydrolyzed Collagen

50 50

Carbomer

2

Propylene Glycol PEG-40 Hydrogenated Castor Oil Sodium Hydroxide Tetrasodium EDTA Water, preservative pH value

[wt.-%]

4.0 1.5 60.0 3.0 2.0

10 40

3.0 0.2 ad 100 5.6

95

Alkyl Polyglycosides in Personal Care Products

Table 13. Perming/Fixing No. INCl declaration Thioglycolic Acid Ammonia Etidronic Acid Ammonium Carbonate Decyl Glucoside Hydrogen Peroxide Xanthan Gum Water, preservative pH value

24 Perming AS

[%I

98 25 60 55 35 2

25 Fixing [wt.-%]

8.0 10.0 0.3 3.0 1.0

ad 100 8.5

-

0.3 -

1.0 7.5 15.0 ad 100 3.5

5.8 Styling and permanent-wave products

The effects of alkyl polyglycosides in styling formulations are based on their substantivity to hair. Formulation 2 3 (Table 12) is one example of a styling gel. In permanent-wave formulations, the use of alkyl polyglycosides provides for an improved permanent-wave effect and, at the same time, reduces hair damage. Formulations 24 and 25 (Table 13) are examples of such products. 5.9 Shampoo concentrates The development of specific cleansing concentrates as a new marketing concept is a consequence of consumer demand and legislation to reduce packaging waste. Highly concentrated raw materials are required for such formulations in order to control the water balance. However, formulations of this type are normally very viscous and require special processing techniques for dilution. By adding alkyl polyglycosides, it is possible to develop highly concentrated yet easily dilutable consumer products. Some examples are given in Table 14 (formulations 26 to 28). 5.10 Cremes and lotions

A long-chain alkyl polyglycoside compound provides a simple solution for vegetable based products, especially for sensitive skin (Table 15, formulations 29 to 31). The oil mixtures follow the concept of the sliding cascade of emolliency for a smooth and pleasant feeling of the skin.

96

Holger Tesmann,Jorg Kahre, Hermann Hensen, and Barry A. Salka

Table 14. Shampoo concentrate

No. INCl declaration

26 AS [%I

Sodium Laureth Sulfate Decyl Glucoside Cocamidopropyl Betaine Laurdimonium Hydroxypropyl Hydrolyzed Collagen PEG-7 Glyceryl Cocoate PEG-3 Distearate (and) Sodium Laureth Sulfate Sodium Chloride PEG-400 pH value

27

28

[wt.-%l

70 55 30 35

19.0 6.0 1.0 2.0

45.0 5.0 8.0 3.0

40.0 10.0 15.0 -

40

2.0 5.0

-

-

1.0 5.5

2.0 10.0 5.5

3.0 10.0 5.5

15,000

4,500

3,500

30

31

Viscosity 20°C [mPa.sl (Brookfield)

Table 15. Creams and lotions No. INCl declaration

29 AS [%I

Cetearyl Alcohol Cetearyl Glucoside Dicaprylyl Ether Decyl Oleate Caprylic/Capric Triglyceride Oleyl Erucate Dimethicone a-Tocopherol Glycerol Water, preservative Viscosity 23'C [mPa.sl (Brookfield)

87

[wt.-%l 6.0 1.5 2.0 4.0 4.0 3.0 0.5 1.0 3.0 75.0

0.5 1.0 3.0 80.0

2.3 3.6 2.0 4.0 4.0 3.0 0.5 1.0 3.0 76.6

75,000

6,000

150,000

3.6 0.9 2.0 2.0 4.0

3.0

Alkyl Polyglycosides in Personal Care Products

97

5.11 Summary

The main important properties and corresponding applications are summarized in the following: Property nonionic surfactant based on renewable raw materials - extremely mild - readily biodegradable - ecotoxicologically safe - goodfoamer - viscosity enhancer - cleansing power - rheology modifier - substantivity to hair

- influence on strength and interaction of hair fibers

- stable at alkaline pH value - emulsifier - microemulsion formation

Use basic or co-surfactant for all kinds of personal care and cleansing products - shampoo - shower bath - baby products - oil bath - syndet bars - dental care products - blends and core concentrates - shampoo concentrate - setting lotions - styling gels - hair conditioners - shampoo for fine or damaged hair - volume and body of hair - perms - hair rinses - hair colours - perfume solubilization - creams and lotions for sensitive skin - refatting preparations - facial cleansers

References 1. F. Hirsinger, K. P. Schick, Tenside Surf. Det. 32 (1995) 193 2. W. Matthies, H.-U. Krachter,W. Steiling,W. Weuthen, 18th IFSCC,Venice,

1994, Poster Vol. 4, p. 317 3 . P. Busch, H. Hensen, J. Kahre, H. Tesmann, Agro-Food-Ind. Hi-Tech 1994

(Sept/Oct) 23 4. P. Busch, H. Hensen, H.-U. Krachter, H. Tesmann, Cosmetics & Toiletries Manuf. Worldwide 1994, 123 5. K. H. Schrader, M. Rohr, Euro Cosmetics 1994, 18 6. K. H. Schrader, Parfiimerie und Kosmetik 75 (1994) 80 7. P. Busch, H. Hensen, H. Tesmann, Tenside Surf. Det. 30 (1993) 116

98

Holger Tesrnann,Jorg Xahre, Hermann Hensen, and Barry A. Salka

8. B. Jackwerth, H.-U. Krachter, W. Matthies, Pafimerie und Kosmetik 74 (1993) 143, Engl. edition 74 (1993) 142 9. D. D. Strube, S. W. Koontz,R. I. Murata, R. F. Theiler,J. SOC.Cosmet. Chem. 40 (1989) 297 10. B. Salka, Cosmetics Toiletries 108 (1993) 89 24 11. M. Rohr, K. H. Schrader, Euro Cosmetics 1994 (8), 12. U. Zeidler, J. SOC. Cosmet. Chem. Japan 20 (1986) 17 13. J. Steber, W. Guhl, N. Stelter, F. R. Schroder, Tenside Surf. Det. 32 (1995) 515 14. P. Gerike, W. Holtmann, W. Jasiak, Chemosphere 13 (1984) 121 15. EEC (1994) Commission Regulation (EC) No. 1488/94; EEC (1994) Risk

Assessment of Existing Substances,Techn. Guidance Document, European Commission DG X I , Brussels 16. Th. Forster, H. Hensen, R. Hofmann, B. Salka, Cosmetics & Toiletries 110 (1995) 23; Parfiimerie und Kosmetik 76 (1995) 763 17. J. Kahre, D. Goebels, Agro-Food-Ind. Hi-Tech 1995 (March/April), 29; 41st Annual Conference SEPAWA 1994,36 18. D. Nickel, C. Nitsch, C.-P. Kurzendorfer, W. von Rybinski, Progr. Colloid Polym. Sci. 89 (1992) 249 19. E. M. Kutschmann, G. H. Findenegg, D. Nickel, W. von Rybinski, Colloid Polymer Sci. 273 (1995) 565 20. K. Fukuda, 0. Sodermann, B. Lindman, K. Shinoda, Langmuir 9 (1993) 2921 21. Th. Forster, B. Guckenbiehl, A. Ansmann, H. Hensen, Seifen, Ole, Fette, Wachse Journal 122 (1996) 746 22. M. Weuthen, R. Kawa, K. Hill, A. Ansmann, Fat Sci. Technol. 97 (1995)209 23. DE-P 19534371, Henkel (1995) 24. EP 0304627 A2,Henkel(1988) 25. P. Busch, H. Hensen, D. Fischer, A. Ruhnke, J. Franklin, Seifen, Ole, Fette, Wachse Journal 120 (1994) 339; Cosmetics & Toiletries 110 (1995) 59

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

6. Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents Hans Andree, J. Frederick Hessel, Peter Krings, Georg Meine, Birgit Middelhauve, and Karl Schmid

This chapter concerns with the use of alkyl polyglycosides in hard surface cleaners. Cleaners of this type include manual dishwashing detergents as well as all-purpose cleaners and a range of special-purpose cleaners such as bathroom and toilet cleaners and window cleaners. Possibilities for using alkyl polyglycosides in laundry detergents are also discussed. 1. Alkyl polyglycosides in manual dishwashing detergents

Since the introduction of manual dishwashing detergents (MDD),the requirements which the consumer expect this group of products to satisfy have continually changed. For modern manual dishwashing detergents, the consumer wants different aspects to be considered to a greater or lesser extent according to hidher personal relevance (Figure 1). The possibility of using alkyl polyglycosides on an industrial scale began with the development of economic production processes and the establishment of large capacity production plants (see also Chapter 2). Alkyl polyglycosides with an alkyl chain length of C,,,,, (C12/,., APG, Glucopon 600)is preferred for manual dishwashing detergents. The typical average degree of polymerization (DP) is around 1.4.

Performance

Economy

Figure 1. Requirements for manual dishwashing detergents

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H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

For the product developer, alkyl polyglycosides have a number of interesting properties [l-51: - Synergistic performance interactions with anionic surfactants - Good foaming behavior - Low skin irritation potential - Excellent ecological and toxicological properties - Completely derived from renewable resources. The basic properties of alkyl polyglycosides in combination with other surfactants are discussed and their use in the individual markets of Europe, North and Latin America and Asia is then described. 1.1 Basic properties of alkyl polyglycosides in combination with other surfactants

- Dishwashing performance In conjunction with anionic surfactants, alkyl polyglycosides show significant synergisticeffects which can be demonstrated not only by physicochemical methods (see Chapter 41, but also by methods of greater relevance to the consumer, for example the plate test. Typical soils in the plate test are fats (as sole soil component) and so-called mixed soils (mixtures of fat, starch and protein). C12/I4 AI'G show pronounced synergisms with the three primary surfactants linear alkyl benzene sulfonate (LAS), secondary alkane sulfonate (SAS) and fatty alcohol sulfate (FAS). These synergisms are far more pronounced than those observed with fatty alcohol ether sulfate (FAES) (Figure 2). In contrast to alkyl polyglycosides, other nonionic surfactants, such as fatty alcohol polyethylene glycol ether (FAEO),do not show any synergisms with FAES (Figure 3). Three primary surfactant systems are found worldwide in manual dishwashing detergents, namely: LAS, SAS and €AS, often in combination with FAES. The performance of these primary surfactant systems can be enhanced by so-called co-surfactants,for example betaines or fatty acid alkanolamides and, above all, alkyl polyglycosides (Figure 4) t41. The dishwashing performance of the FASIFAES-based surfactant system, which is relatively poor in contrast to the LASIFAES and SAS/FAFS systems, can be significantlyincreased simply by replacing small quantities of the primary surfactants with co-surfactants. The combination of alkyl polyglycosides with betaine has been particularly beneficial in performance evaluation using mixed soil El. - Foaming behavior A feature of many conventional nonionic surfactants, such as FAEO, is their relatively low foaming capacity, alone or in combination with conventional anionic surfactants. In contrast, alkyl polyglycosides, which, when combined

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

101

a

mc cn

c

v)

w

0

102

H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

Number of plates washed

FAES/FAEO

15

Test method: Plate test Test soil: Beef tallow Concentration:

10

0.1 g/l active substance Temperature: 50'C

5

Water hardness: 16'd

80 20

60 40

40

20

60

80

0

[%I FAES

loo[%]FMOor APG

Figure 3. Dishwashing performance of tion with FAES

CWMAPG compared with FAEO in combina-

with anionic sufactants, show favorable foaming behavior, i. e. increases the foam volume or keeps it at a high level. Figure 5 shows by way of example the influence of C ~ 1 APG 4 on the foaming capacity of FAS and FAES. - Dermatological behavior Manual dishwashing detergents belong to the category of products which very frequently come into contact with the skin of the consumer,albeit in dilute form. Accordingly, the skin compatibilityof this group of products is of particular interest. Alkyl polyglycosides are not only mild on the skin, but can significantly reduce the skin irritation by anionic surfactants.Initial indications of the skin compatibility of surfactants or surfactant combinations on a direct comparison basis can be obtained by a patch test t61. The concentration of the test solutions is intentionally selected to produce a skin reaction, albeit slight. The dermatologist evaluates the degree of change in the skin according to the following criteria: erythema, edema, squamation and fissures, on a predetermined points scale. The test results obtained with the primary surfactantsLAS, SAS and €AS and combinations thereof with alkyl polyglycosides are set out in Figure 6. In every case, a distinct reduction in the relative total irritation scores is achieved when alkyl polyglycoside is combined with LAS, SAS, or FAS at same active substance content. Equally positive results are obtained in the in-vitro test on the chorionallantois membrane on fertilized hens' eggs (HET-CAM, see also Chapter 9 ) (Figure7 )for determining mucous membrane compatibility [71. Whereas hardly any improvementin mucous membrane compatibilityis obtained by addition of

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

c .a, c 0 L

Qc:

103

m

c

cn

m-

s c 0

a

Dm

I

w

104

H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid after 20 sec

Foam volume [ml] 700

Iafter 20 min

600 500

Test method: Whipped foam test (DIN 53902)

400

300 Concentration: 1 g/l active substance

200 100

Temperature: 20°C APG

FAS

FAS/APG

FAES FAES/APG

(3:l)

Figure 5. Foaming behavior of

(3:l)

Water hardness: 16"d

APG containing surfactant mixtures

C1z/14

betaines, a significant improvement is obtained by increasing additions of alkyl polyglycosides. 1.2 Alkyl polyglycoside containing manual dishwashing detergents in Europe

Within the group of hard surface cleaners, manual dishwashing detergents are the most important in terms of tonnage. Thus, around 1.3 million tonnes of manual dishwashing detergents were produced in Europe in 1992 [81. At the present, in Europe there are three segments: conventional manual dishwashing

Test method: Patch test

FAES (Standard) APG

Test conditions: 20 healthy volunteers (male and female)

LAS LAS + APG (1:l) SAS

Concentration: 1%active substance

SAS + APG (1:l)

Mode of application: Once, occlusive

FAS FAS + APG (1:l)

0

100

200 300 400 Rel. irritation score [%I

Duration of application: 24 h

Figure 6. Skin compatibility of CI2ll4APG and binary surfactant combinations

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents Rel. irritation score [%I

105 FAES/APG

IFAES/Betaine

12001 1000

Test method: HET-CAM

800

Concentration: 3 % active substance

600 400

200 80 20

60

40 60

40

Figure 7. Mucous membrane compatibility of combination with FAES

20 [%I FAES 80 [%I APG or Betaine

APG compared with betaine in

C121~4

detergents, or high active manual dishwashing detergents (concentrates) and manual dishwashing detergents with excellent skin compatibility. The most significant segment today is still that of conventional manual dishwashing detergents. However, they are by no means a homogeneous group from the formulation point of view. On the contrary, they may be divided into three groups (Table 1) which differ significantly in their active substance content and hence in their performance (for the same dosage).Products of relatively low concentration are found in Southern Europe while products of relatively high concentration are found, for example, in Great Britain. Since their introduction in Europe (Spain: 1984, Germany: 1992), very high active products that are used at half or one third the dose of conventional dishwashing detergents have

Table 1. Segmentation of conventional manual dishwashing detergents Group

Surfactants [wt-%]

Countries

1

10-15

Portugal, Spain

2

15-27

Austria, France, Germany, Italy, Switzerland

3

35-40

United Kingdom

H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

106

Table 2. General formulations for conventional and concentrated manual dishwashing detergents of the European market

Ingredients

[wt.-%l

-~

Anionic surfactants

Lin. alkylbenzene sulfonate

10-35

Sec. alkane sulfonate Alkyl sulfate Alkyl ether sulfate

Nonionic surfactants

Alkyl polyethylene glycol ether Alkyl polyglycoside Fatty acid glucamide Fatty acid alkanolarnide Alkyl dirnethyl amine oxide

115

Amphoteric surfactants

Al kyl betaine Al kylarnidobetaine

<5

Minor ingredients

Protein

<2

Hydrotropes Fragrances Preservatives Colorants Salts Water

Polymer
Balance

experienced continual growth. Manual dishwashing detergents with excellent skin compatibility for consumers with sensitive skin were first introduced onto the European market by two manufacturers of branded goods at the end of 1992. Alkyl polyglycoside containing manual dishwashing detergents which satisfy all consumer requirements are now available for all three market segments. - Dishwashing performance The core property of a manual dishwashing detergent, namely its high cleaning performance, is still demanded by the consumer. Table 2 illustrates the formulation scope available to the product developer. In Europe today, all three primary surfactant systems (LASIFAES-, SASIFAES-, FAS/FAES-based) are represented in the market both in conventional manual dishwashing detergents and in the concentrates. The synergistic interactions of alkyl polyglycosides with the various primary surfactant systems enables the product developer to formulate even more effective products for the same active substance content or to reduce the active substance content without affecting the performance level (Figure 8),resulting in possible cost advantages.

Alkyl Polyglycosidesin Hard Surface Cleaners and Laundry Detergents

107

Number of plates washed

19%AS

15 1

14%AS Test method: Plate test

10

Test soil: Beef tallow

5

Concentration: 0.5 g/l product 9.0 9.0 1.0 -

8.0 8.0 1.0 2.0

7.0 7.0 1.0 4.0

[%I [%I [%I [%I

FAS FAES

5.7

Betaine APG

0.9

5.7 1.7

4.9 4.9 0.9 3.3

Temperature:

50°C Water hardness: 16'd

Figure 8 . Dishwashing performance of conventional manual dishwashing detergents containing C l ~ / l 4APG

- Foaming behavior Although foam volume and foam structure both in the dishwashing liquor and under running water do not directly determine product performance, they are experienced by the consumer and thus lead to purchasing decisions. In alkyl polyglycoside, the product developer has a nonionic surfactant that improves the foam properties of the product. Both foam height and foam stability under mechanical influence can be investigated by the stress stability of foam test. In this test, the foam is produced by introducing air into the surfactant solution in defined quantities through a sieve of predetermined mesh width. The foams formed can be observed in regard to appearance and volume as a function of time. Additional information can be obtained by subjecting the foams thus produced to mechanical impact. Information on the sensitivity of the foams to fatty soil can be acquired by adding the soil at the beginning of the test and including it in the foaming process. The test results obtained with various commercial concentrates, even in the presence of soil, are set out in Figure 9. In this case, a mechanical impact was applied to the foam after 10 minutes and the foam height was determined in the following 5 minutes. The results show that the alkyl polyglycoside containing dishwashing detergent produces an elastic foam which is relatively unaffected by soil. - Dermatological properties The product developer obtains initial indications of the skin compatibility of manual dishwashing detergents by the patch test. This enables him to test

H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

108

Foam height without soil Foam height with vegetable oil

Foam height [cml 351 30

Test method: Stress stability of foam

25

Concentration: 1 g/l product

20

Temperature: 50'C

15 Water hardness: 16'd

10 5

0 5 10 15' A

0 5 10 15* 0 5 10 15* Time [minl B C

A Alkyl polyglycoside containing concentrate B Glucamide-containing concentrate C SAS-based concentrate * with mechanical impact

Figure 9. Foaming behavior of concentrated manual dishwashing detergents

different formulations at the same time. In general, further dermatological studies are subsequently carried out under conditions of greater practical relevance. They include the hand immersion test [91 in which the consumers (at least 20 volunteers) every day immerse their hands in dishwashing liquid solutions under controlled conditions for several days. A dermatologist evaluates the degree of changes in the skin according to various criteria. When the first alkyl polyglycoside containing manual dishwashing detergent was nationally introduced in Europe in 1989,the hand immersion test was used to investigate Irritation score 2oo

Erythema

1

Sum of erythema, edema, squamation and fissure Test method: Hand immersion test Test conditions: 20 healthy volunteers (male and feniale) Concentration: 1% product Duration of application: 30 min, 5 d

A Brand claiming good skin compatibility

A

B

B First brand containing alkyl polyglycosides

Figure 10. Skin compatibility of conventional manual dishwashing detergents

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

109

the skin compatibility of the product in comparison with a marketed product claiming high skin compatibility. Figure 10 shows that the alkyl polyglycoside containing manual dishwashing detergent has significant advantages. In particular, it is distinguished by a distinct reduction in the formation of erythema and squamation. Nevertheless, there are significant numbers of consumers who still have problems using these conventional manual dishwashing detergents so that they often wear gloves. For these consumers with sensitive and dry skin, products have been available since the end of 1992 which are demonstrably superior in skin compatibility to the products known up to that time. One manufacturer uses large quantities of nonionic surfactants (FAEO with a particular alkyl chain length and a special degree of ethoxylation) while another has marketed an anionic-surfactant-based formulation containing alkyl polyglycosides and other skin protective components. Figure 11 shows the results of a dermatological study on a group of volunteers with normal skin. The alkyl polyglycoside containing product has the best skin compatibility of all the products tested. Further studies, including the hand immersion test with a selected group of volunteers, proved that these products are also tolerated significantly better than conventional and concentrated manual dishwashing detergents, even by volunteers with dry and sensitive skin. Reactions show that consumers with sensitive skin fare excellently with this new product category. This is also reflected in the increase in sales figures. Irritation score 8o

Erythema

Sum of erythema, edema, squamation and fissure

1

Test method: Patch test Test conditions: 20 healthy volunteers (maleand female)

60

Concentration: 1%active substance Mode of application: Once, occlusive

40

Duration of application: 24 h A Brand, claiming good skin compatibility

20

B Market product for sensitive skin A

B

C

C Market Drodukt for sensitive skin with alkyl poiyglycoside

Figure 11. Skin compatibility of conventional manual dishwashing detergents as compared to manual dishwashing detergents with excellent skin compatibility

110

H. Andree,J. F. Hessel, P. Krings, G. Meine, B.Middelhauve,and K. Schmid

Ecological compatibility As shown in Table 2, surfactants are by far the most important group of active substances in manual dishwashing detergents. Accordingly, they play a key role in the ecological compatibility of a dishwashing detergent. In many European countries, a minimum biological degradation rate is legally stipulated. However, the object of product development should be to use raw materials with total biodegradability, i. e. proven ultimate biodegradation, preferably raw materials which are degraded not only aerobically but also anaerobically. The toxicological and ecological properties of alkyl polyglycosides are discussed in detail in the Chapters 9,10 and 11. As can be seen from that accounts, alkyl polyglycosides are distinguished by optimal toxicological and ecological data. The combination of alkyl polyglycosides with other surfactants characterized by very good biodegradability leads to products which fully satisfy the requirements of consumers and authorities in regard to the ecological compatibility of this product category. Table 3 illustrates how high-performance commercial dishwashing detergents can be formulated with alkyl polyglycosides for a significantly lower surfactant content at the same time. The following estimation illustrates the environmental impact of reducing the surfactant content of formulations. In 1992,around 300,000 tons of surfactants were used in manual dishwashing detergents in Europe. Now, if high-quality alkyl polyglycoside containing products with an active substance content lower, for example, by 20 010 were to be brought onto the market, the discharge of surfactants into domestic wastewater would be reduced by 60,000 tons. -

Table 3. General formulations of conventional manual dishwashing detergents (MDD) with similar performance Ingredients

MDD without

C12/14

[wt.-%l Sec. alkane sulfonate Alkyl sulfate Alkyl ether sulfate Alkyl polyglycoside Alkylarnidobetaine Ethanol Fragrances Colorants Water ~~~~~~

APG

MDD with C12114 APG

[wt.-%I

15-25

-

-

2-10 5-15 1- 5 1-5
2-10 -


Balance

~

Total amount of surfactants

20

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

111

1.3 Alkyl polyglycoside containing manual dishwashing detergents in America

Since the products used in North America and in Latin America differ distinctly in their composition and consistency, the manual dishwashing detergents of the North American market will be described first and those of the Latin American market thereafter. - Manual dishwashing detergents in North America In North America, there are at present four manual dishwashing detergents segments, namely: conventional manual dishwashing detergents (private label and premium products), concentrates, manual dishwashing detergents with an excellent skin compatibility and manual dishwashing detergents containing an antibacterial agent. The most important segment today is that of conventional manual dishwashing detergents (premium products) which are essentially based on two surfactant systems: LAS/FAES/fatty acid alkanolamide and FAES/ betainelamine oxide. The inexpensive private label products (economy brands) have distinctly lower active substance contents and, accordingly, are of significantly lower performance for the same dosage. Nearly crystal-clear manual dishwashing detergents with excellent skin compatibility were introduced onto the market in 1992. They are based on FAEO and betaine and contain relatively small quantities of anionic surfactants, for example FAES. In 1995, various manufacturers began marketing manual dishwashing detergents which can also be used as a liquid hand soap and which contain an antibacterial agent. In North America, too, the advantages of alkyl polyglycosides (performance, foaming behavior and skin compatibility) have already resulted in the reformulation of more than 10 brands. - Conventional manual dishwashing detergents The majority of conventional dishwashing detergents are based on LAS due to the relatively high cost of FAES as compared with LAS. As in Europe, alkyl polyglycosides are used as co-surfactants in these products. The optimum cost/ effectiveness ratio of LAS/alkyl polyglycoside surfactant combinations under American conditions is between 3:l and 4:l. Formulations and selected performance figures both for LAS- and FAES-based products are shown in Figure 12. The performance of both the LAS- and the FAES-based premium product is comparable with that of the market leader in the premium segment. Various manufacturers have meanwhile introduced such alkyl polyglycoside containing products onto the market. - Concentrated manual dishwashing detergents Concentrated manual dishwashing detergents known as ultra liquids were brought onto the market in 1995 by various manufacturers. These products are marketed in 14.7 oz. bottles in contrast to the conventional 22 oz. bottles. The recommended dosage is one third lower than that of conventional products for

112

H. Andree,J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

Performance soil [gl 4

A B C D Test method 1

Performance pellets [number] 4

Market leader in the premium category Test method 1: Tergotometer Test soil: Fat, protein on cotton swatches Concentration: 1.5 g/l product Temperature: l l O ' F (43 "C) Water hardness: 150 ppm (Ca:Mg=3:2)

Test method 2: Modified Shell Test soil: Fat, protein, starch Concentration: 40 g/l product Temperature: l l O ' F (43 "C) Water hardness: 150 ppm (Ca:Mg=3:2)

A B C D Test method 2 ~~~

Ingredients

Lin. alkylbenzene sulfonate Alkyl ether sulfate Alkyl polyglycoside Alkylamidobetaine Fatty acid dialkanolamide Ethanol Xylene sulfonate Water

Economical manual dishwashing detergents based on LAS/APG A

FAES/APG

12.6 3.2 1.0 1.o 1.8 1.6 Balance

9.8 3.2 5.0

B

2.5 BaI anc e

Premium manual dishwashing detergents based on LAS/APG FAES/APG C D 19.2

-

4.8 2.0 2.0 3.2 3.2 Balance

14.2 4.6 7.2

6.5 Balance

Figure 12. Conventional C12/14 APG containing manual dishwashing detergents in North America

the same performance. Ultra liquids contain around 45 to 500!0 surfactants as compared to about 30 010 in conventional dishwashing detergents. Accordingly, the use of alkyl polyglycosidesis an advantage in ultra liquids because, by virtue of the interactions with anionic surfactants described earlier, highly effective products with relatively low active substance contents can be formulated with alkyl polyglycosides. In addition, alkyl polyglycoside containing ultra liquids require less hydrotrope than alkyl polyglycoside free ultra liquids for making up. As in the case of conventional dishwashing detergents, the partial or complete replacement of FAES by alkyl polyglycosides leads to increases in per-

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

Table 4.

113

APG containing ultra concentrates in North America

C12,14

Ingredients

LAS/APG

[wt.-%l Ltn. alkylbenzene sulfonate Alkyl ether sulfate Alkyl polyglycostde Fatty alkohol ethoxylate Alkylamtdopropylbetaine Fatty acid dtalkanolamide Fatty acid amidopropyl arntne oxide Sodium chloride Ethanol Xylene sulfonate Water

FAES/APG [wt.-%]

FAES/APG

[wt-%l

24.0

-

-

-

28.0 7.2 6.0

30.0 10.0

-

3.0 3.0 5.0 6.0

6.0

6.0 Balance

Balance

Balance

6.0 8.0 3.2 3.0

-

-

-

8.0 -

formance. Table 4 contains examples of alkyl polyglycoside containing ultra liquids which are comparable in cost and performance with leading ultra liquids of the North American market. - I & I solid blocks In addition to liquid manual dishwashing detergents, so-called solid blocks are also available on the American I&I market. Doses of these products are dispensed by means of a jet of water which dissolves out part of the solid block and carries it into the dishwashing liquor. Apart from performance aspects, including for example fat dissolving power and foaming behavior, in the case of solid blocks, processing, hardness and dissolving behavior are also important. Effective alkyl polyglycoside containing formulations (Table 5 ) with favorable dissolving behavior can be provided for this segment also. The hardness of the blocks can be controlled through the ratio of fatty acid monoethanolamide to fatty acid diethanolamide. - Manual dishwashing detergents in Latin America In Latin America, there are three segments to the manual dishwashing detergent market, namely: highly viscous, liquid manual dishwashing detergents of relatively low concentration, low active low viscous manual dishwashing detergents, and paste-form manual dishwashing detergents which, besides surfactants, can also contain builders, abrasives and fillers. In Latin America, too, the advantages of alkyl polyglycosides (performance, foaming behavior, skin compatibility and increase in viscosity in products of relatively low concentration) have also resulted in the introduction of alkyl polyglycoside containing products.

114

H. Andree,J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

Table 5.C12/14 APG containing solid block dishwashingformulations in North America Ingredients

Lin. alkylbenzene sulfonate Alkyl ether sulfate Fatty acid Alkyl polyglycoside Fatty acid monoalkanolarnide Fatty acid dialkanolamide Nonyl phenol ethoxylate Al kylarnidobetaine Ethanol Urea Sodium hydroxide Water (from raw materials)

Solid block 1

Solid block 2

Solid block 3

[Wt.-%l

[wt.-%l

[wt.-%l

13.2 12.0 6.0 4.0 10.0 4.5 6.0 3.0 20.0 0.75 Balance

13.2 12.0 6.0 4.0 10.0 4.5 6.0 3.0 20.0 0.75 Balance

13.2 12.0 6.0 4.0 5.0 5.0 4.5 6.0 3.0 20.0 0.75 Balance

- Liquid manual dishwashing detergents Consumers in some Latin American countries prefer high-viscosity products (around 1000 d a d with high foaming behavior. Typical market products are based on LAS or on combinations of LASIFAES and contain 10 to 15% of active substances.Table 6 shows typical formulations which satisfy Latin American requirements both in regard to viscosity and performance. - Manual dishwashing pastes Many Latin American markets are dominated by dishwashing pastes which are now available in two forms, namely: conventional pastes containing solids and the new clear pastes which contain no solids. The conventional pastes consist of LAS, abrasives (calcium carbonate), builders (sodium tripolyphosTable 6.Manual dishwashing detergents in Latin America Ingredients

Lin. alkylbenzene sulfonate Alkyl ether sulfate Alkyl polyglycoside Fatty acid dialkanolarnide Alkylarnidobetaine Ethanol Sodium chloride

Premium product

Economy product

[Wt.-%l

[wt.-%l

12.6

4.8 3.75 1.25 3.0 1.0 1.0

-

4.0 1.0 1.0 0.25

Alkyl Polyglycosides in H a r d Surface Cleaners and Laundry Detergents

Foam height [mll

Pellets [number]

15

400

115

Market paste C12/14 APG containing paste Test method A: Sponge foam Concentration: 1 g/l product Temperature: room temperature Water hardness: 50 ppm (Ca:Mg=2:l)

300

10 200

5 100

A

B

C

Test method B: Inverted cylinder Concentration: 0.5 g/l product Test soil: Fat, protein, starch Temperature: room temperature Water hardness: 150 ppm (Ca:Mg=3:2) Test method C: Modified Shell Test soil: Fat, protein, starch Concentration: 40 g/l product Temperature: 110-F (43 'C) Water hardness: 150 ppm (Ca:Mg=3:2)

Figure 13. Performance of dishwashing pastes

phate), hydrotropes and fillers. The use of alkyl polyglycosides in these products significantly improves both dishwashing performance and foaming behavior. The performance of an alkyl polyglycoside containing paste is compared with that of a market product in Figure 13. In the alkyl polyglycoside containing paste, 2 To of the active LAS in the market product was replaced by 1% of the active FAES:C12/14 APG (3:l).The results prove that even the use of small quantities of APG can lead to a distinct improvement in performance. The clear pastes are also based on LAS. They contain large quantities of hydrotropes. Examples of alkyl polyglycoside containing pastes which may be both transparent and opalescent in appearance are given in Table 7. The hardness of the pastes can be controlled either through the pH value (low pH value =soft paste) or through the concentration of fatty acid. In addition, an LAS with a high content of 2-phenyl isomers is required for the production of opalescent pastes. 1.4 Alkyl polyglycoside containing manual dishwashing detergents in Asia

In the Asian countries, consumers are concerned mainly with the dermatological properties of manual dishwashing detergents; in addition, there should be no risk to health if foods (for example fruit and vegetables) come into contact with these products. The demand for products highly compatible with the skin is understandable from the different dishwashing customs in most Asian countries as compared with Europe and North America. Whereas in Europe dishes

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H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

Table 7. Opalescent and transparent pastes containing CI2fl4APG Jngredients

Lin. alkylbenzene sulfonic acid Alkyl ether sulfate Fatty acid Alkyl polyglycoside Nonyl phenol ethoxylate Fatty acid dialkanolamide Ethanol lsopropanol Polyethylene glycol 400 Urea Sodium hydroxide Water

Opalescent paste

Transparent paste

[wt.-%l

[wt.-%I

6.7 10.0 5.0 17.5 15.0 5.0 20.0 4.3 Balance

10.0 10.5 4.0 4.0 -

4.0 1.0 3.0 10.0 20.0 3.7 Balance

are mainly washed in dilute detergent solutions (around0.8 to 4.0 g of product/l wash liquor), the consumer in Asian countries usual washes up with a sponge impregnated with the concentrated detergent. Accordingly, this method of dishwashing leads to far more direct skiddetergent contact than in Europe. In order to meet the stringent skin compatibility requirements, manual dishwashing detergents with high contents of nonionic surfactants are produced in such countries as Japan, Korea, Hong Kong and Taiwan and recently in Malaysia and Thailand. FAEO, alkyl polyglycosides, fatty acid alkanolamides, amine oxides and also betaines are preferably used as the nonionic surfactants. The anionic surfactant used in these countries is FAES containing 3 moles of ethylene oxide which is more compatible with the skin than the FAES containing 2 moles of ethylene oxide often used in Europe and North America. FAS is not used at all. The first alkyl polyglycoside containing conventional dishwashing detergent was introduced onto the Japanese market in 1989. In the meantime, alkyl polyglycoside containing concentrates have also been brought onto the market. In Asian countries, in contrast to Europe and North America, alkyl polyglycoside is used as a primary surfactant and not as a co-surfactant. Table 8 shows formulations of concentrated products containing primary surfactants that are particularly mild to the skin. It can be seen that, from the formulation point of view, product stability requirements are best satisfied by alkyl polyglycosides. The use of alkyl polyglycosides as a primary surfactant enables dishwashing detergents to be formulated with a performance level previously only obtained by anionic surfactant-basedformulations.In addition, these prod-

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

117

Table 8 . Stability of concentrated manual dishwashing detergents

Ingredients Alkyl ether sulfate Alkyl polyethylene glycol ether Fatty acid alkanolamide Alkylamidobetaine Fatty acid glucamide Alkyl polyglycoside

Appearance at 68 'F (20'C) Pourpoint

Storage test, 3 weeks, 41'F (5'C)

Product 1 [Wt.-%l

Product 2

10

10 15

15

[wt.-%l

18

Product 3 [wt-%]

Product 4 [Wt-%l

10 15 -

10 15 -

-

18

Cloudy

Gel

Clear

Clear

-

Solid

54'F (12 'C) Solid

32 'F (0'C) Clear liquid

Solid

ucts have excellent skin compatibility. Moreover, the solubilizing capacity of alkyl polyglycosides also enables the use of reduced hydrotrope levels. In Indonesia, the Philippines, Malaysia and Thailand, in addition to the conventional low concentration dishwashing detergents based on linear or branched alkyl benzene sulfonate, there are creamy products for the general cleaning of hard surfaces. Here also skin compatibility can be further optimized by the use of alkyl polyglycosides. 2. Alkyl polyglycosides in cleaners

The relatively long-chain alkyl polyglycosides with an alkyl chain length of C, and a DP of around 1.4 have proved to be of particular advantage for manual dishwashing detergents. However, the relatively short-chain alkyl polyglycosides with an alkyl chain length of C,, and a DP of about 1.5 (CW~O APG, Glucopon 215, 220) are particularly useful in the formulation of all purpose and specialty cleaners. Formulations for cleaners containing surfactants and surfactant combinations based on a petrochemical and vegetable feedstocks are sufficiently wellknown. Extensive knowledge has been built up on this subject [lo].Now that light-colored short-chain alkyl polyglycosides are also available on the market, many new applications are being found for alkyl polyglycosides by virtue of their broad performance spectrum: - Good cleaning efficiency - Low environmental stress cracking potential (ESC) for plastics

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H. Andree, J. F. Hessel, P. Krings, G. Meine, B.Middelhauve, and K. Schmid

- Transparent residues - Good solubility - Good solubilization Stable against acids and alkalis Improvement of low temperature properties of surfactant combinations Low skin irritation - Excellent ecological and toxicological properties. Today, alkyl polyglycoside containing products are found both in all-purpose cleaners and in special cleaners, such as bathroom cleaners, toilet cleaners, window cleaners, kitchen cleaners and floor-care products [I 11. -

2.1 All-purpose cleaners

The broad range of soil types found in the home require modern all-purpose They have to perform effectively against both emulsifiable oilcleaners (APC). and fat-containing soils and against dispersible solid soil particles. Today, there are three segments for the European all-purpose cleaner market: conventional all-purpose cleaners, concentrated all-purpose cleaners and all-purpose cleaners with excellent skin compatibility. Table 9 illustrates the formulation scope for the product developer. Essential ingredients are surfactants and builders. Table 9. General formulations for conventional and concentrated all-purpose cleaners Ingredients

Conventional APC

Double conc. APC

[Wt.-%I

[Wt.-%I

5-10

10-20

Surfactants

Lin. alkylbenzene sulfonate Sec. alkane sulfonate Alkyl sulfate Alkyl ether sulfate Soap Alkyl polyalkylene glycol ether Alkyl polyglycoside

Builders

Citrate Gluconate Bicarbonate/carbonate

1-2

1-3

Solvents/hydrotropes

Curnene sulfonate Alcohol Glycol ether

0-5

1-6

Additives

Fragrances Colorants Preservatives

<1

<2

Balance

Balance

Water

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

119

Alkyl polyglycoside containing products are now available on the market for all three segments. Alkyl polyglycosides themselves have an excellent cleaning performance which can be determined, for example, in accordance with the IPP quality standard [121. The cleaning performance can be further increased by small additions of anionic surfactants and/or polymeric boosters. Thus, it is possible to formulate products comparable in cleaning performance to the market leaders at significantly lower surfactant contents. All-purpose cleaners with particularly good skin compatibility should be slightly acidic rather than alkaline. With alkyl polyglycoside, the product developer has a surfactant of which the high cleaning performance level is hardly affected by changes in the pH value. Consumers today prefer all-purpose cleaners with moderate or low foaming behavior. The foaming capacity of alkyl polyglycoside containing cleaners can readily be reduced by using small quantities of soaps or increased by adding small quantities of anionic surfactants. A suitable foaming capacity can thus be adjusted for each country. Alkyl polyglycoside has proved to be the problem solver in the formulation of concentrated all-purpose cleaners with excellent ecological compatibility. With alkyl polyglycosides, it is possible to formulate concentrates which have a correspondingly higher content of builders and perfume oils and require lower quantities of hydrotropes. Table 10. General formulations for bathroom cleaners Ingredients

[wt-%]

Surfactants

Lin. alkylbenzene sulfonate Sec. alkane sulfonate Alkyl sulfate Alkyl ether sulfate Alkyl polyethylene glycol ether Alkyl polyglycoside

2.0-8.0

Builder

Citrate, etc.

0.5-2.0

Acids

Citric acid Acetic acid Lactic acid Dicarboxylic acid

3.0-6.0

Solvents

Alcohols Glycols

2.0-9.0

Additives

Fragrances Colorants Preservatives

Water

<1 Balance

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H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

Cleaning efficiency

[%I

Test method: IPP quality norm

100

Test soil: Oil, carbon black, inorganic pigments, paraffins

50

Concentration: Concentrated (spray product) Temperature: 20'C C8,qo APG

FAS

SAS

FAES

FAEO(8EO)

Water hardness: 16'd

Figure 14. Cleaning efficiency according to IFF

2.2 Bathroom cleaners Bathroom cleaners today are used in the form of liquid and foam pumps or aerosol packs. Table 10 shows the formulation scope for liquid bathroom cleaners. Bathroom cleaners are generally adjusted to an acidic pH although it is important to ensure that damage to sensitive enamels is avoided. A pH range of 3 to 5 is recommended for bathroom cleaners. The most common soils in bathrooms are greasy soils, lime soap residues and lime residues based on the hardness of the tap water. The performance of a cleaner consisting of 4Yo surfactant, 4 010 citric acidkitrate and 2.5 O!o ethanol against these soils is shown in Figure 14. The surfactant components investigated were C8jl0AF'G, FAEO (8 EO), FAS, SAS and FAES. Another important performance feature of bathroom cleaners besides their actual cleaning performance is the avoidance of environmental stress cracking in components made of plastic, including handles, water overflows in bath tubs, fittings or shower holders. Important bathroom plastics are listed according to their sensitivity to environmental stress cracking (ESC) in Table 11.By interacting with the various ingredients present in bathroom cleanTable 11. Plastics in bathrooms Plastic sensitve to environmental stress cracking

Plastic less sensitive to environmental stress cracking

Acrylonitril, butadiene, styrene ABS/polycarbonate Polycarbonate Polymethacrylate

Cellulose propionate Polyamide Polymethylene, polyformaldehyde Polypropylene

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

Plastic sample Unchanged

121

Test method: Modified test according to DIN 53449

I

Concentration: Concentrated product Exposure time of product: 15 rnin Observation time:

Cracks

Max. 24 h C 8/10 APG FAEO(8EO) FAEO(12EO) SAS

FAS

Temperature: Room temperature

Figure 15. Environmental stress corrosion of bathroom cleaners

ers, plastics can develop environmental stress cracks which, in the past, have resulted in considerable claims against the manufacturers. In the laboratory, environmental stress cracking effects can be simulated both by the pin impression method and by the ben strip method t131. In the pin impression method, the plastic is prestressed by indentation with a steel pin and is then immersed in the test solution for 15 minutes. The plastic is then dried and evaluated after 24 hours. In the ben strip method, plastic strips are prestressed by weights. The test solution is then allowed to act on the plastic strips for 15 minutes. The strips are then dried and likewise evaluated after 24 hours. The results obtained with low-concentration bathroom cleaners, for example of the aerosol type, are set out in Figure 15. C8/loAPG as a nonionic surfactant is as favorable in regard to preserving behavior as conventional anionic surfactants.

2.3 Liquid toilet cleaners The function of toilet cleaners is to remove effectively fecal soils, lime and rust deposits and urinary calculus. In the past, products based on inorganic acids, such as hydrochloric acid and phosphoric acid, in combination with surfactants have been used to remove these soils. Unfortunately, these formulations were the subject of public debate both for ecological and for safety reasons. As a result of the increasing environmental awareness of consumers, there is a demand for ecologically acceptable formulations containing readily biodegradable acids. Table 12 shows the formulation scope for toilet cleaners. Besides their high acid stability in formulations, alkyl polyglycosides also support the cleaning performance of formulations against both lime-containing and organic soils. The performance of toilet cleaners against the soils mentioned above can be deter-

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Table 12. General formulations for liquid toilet cleaners

[Wt.-%l

Ingredients

Table 13. General formulations for window cleaners

[Wt-%l

Ingredients

Surfactants 0.5-2.0 Lin. alkylbenzene sulfonate Sec. alkane sulfonate Alkyl sulfate Alkyl polyethylene glycol ether Alkyl polyglycoside

Surfactants Olefin sulfonate Sec. alkane sulfonate Alkyl sulfate Alkyl ether sulfate Alkyl polyglycoside

0.05-0.4

4.0-9.0

Solvents Ethylene glycol ether Propylene glycol ether Ethanol lsopropanol

3.0-20.0

Acids Citric acid Acetic acid Formic acid Lactic acid Hydrochloric acid Additives Fragrances Colorants

<1

Water

Balance

Additives Fragrances Colorants Water

<1

Balance

mined as follows. A black tile is soiled with a defined quantity of a mixture of acid-soluble calcium carbonate and hydrophobic calcium stearate. The tile is then immersed in the undiluted cleaner for 10 seconds and subsequently removed again. The adhering cleaner solution is left in contact with the soil for Soil removal [%I

Test method: Internal method

100

Test soil: Artificial soapscum (Ca stearate)

80 60

Concentration: Concentrated product

40 20

Temperature: Room temperature

2.0 -based formula

2.0 0.8 FAS-based formula

Figure 16. Soil removal of liquid toilet cleaners

123

Alkyl Polyglycosidesin Hard Surface Cleaners and Laundry Detergents

another 10 minutes by keeping the tile upright. The cleaner and the soil are then rinsed off under running water. The cleaning result is determined both visually and by weight analysis. Figure 16 shows results obtained with C8/l0APG containing cleaners in comparison with cleaners based on anionic surfactants. The formulations consist of 0.8 and 2.0 Yo of surfactant, 6 Yo of acetic acid, 2.5 o/o of ethanol and 0.4 Yo of a thickener. 2.4 Window cleaners

Modern window cleaners consist mainly of a surfactant component and a solvent component (Table 13).Besides a good wetting effect on the soil and the glass surfaces, the surfactants must also have a good fat-emulsification power. In addition, the surfactant residue on the surface must be transparent and easily removable by polishing. Normal use provides for the direct removal of soil in a single operation, i. e. spraying on, spreading the liquid with a clean cloth, then removing the liquid together with the detached soil with a view to obtaining a clean and streak-free window. If not properly applied, the product can dry and individual, nonvolatile components can remain behind in the form of troublesome coatings and greasy films. With reference to the example of formulations containing 0.1 to 0.4 Yo of surfactant, 1 to 3 010 of glycol ether and less than 1010 of perfume, it is shown that purely anionic surfactant-containing residues are more difficult to polish out than combinations of anionic surfactants with nonionic surfactants (Figure 17). The residue of an FAS/Cm APG containing formulation can be polished out particularly effectively. The optimum ratio of FAS to alkyl polyglycoside is dependent upon the perfume oil used and upon the associated total Polishability

Test method: Internal method

I

Easy

i

I FAS

FAES

I1

Concentration: Concentrated (spray product) Temperature: Room temperature

SAS FAS/CB/,o APG FAS/FAE0(4EO)

Figure 17. Polishability of residues

H. Andree,J. F. Hessei, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

124

Test method: Internal method

Foaming behavior

I

Excellent -

Satisfying FAS

1 I FAES

SAS

Concentration: Concentrated (sprayproduct) Room temperatiAre

FAS/C8/lo APG FAS/FAE0(4EO)

Figure 18. Foaming behavior of window cleaners

quantity of surfactant. Besides good polishability, the FAS/Cmo APG combination also shows advantages in favorable foaming behavior and very good solubilization of perfume oil. Good foaming behavior is generally difficult to obtain where butoxyethanol is used as the solvent. Figure 18 shows that the use of C8/10APG is also advantageous in this case. 2.5 Floor-care formulations

Floor-care formulations contain surfactants as a major component (Table 14).In contrast to all-purpose cleaners, care components are added to these products and remain behind on the floor whenever it is wiped. The floor is thus protected against abrasion by regular application. This applies to both elastic plastic surTable 14. General formulations for floor-care products

Ingredients

[wt.-%I

Wax component incl. emulsifier Carnauba wax Alkyl polyglycoside

Surfactants

Alkyl sulfate Alkyl polyethylene glycol ether

Additives

Fragrances Colorants

Water

1

1.0-2.0 0.3-0.6 2.0-5.0 2.0-5.0 <1

Balance

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

125

faces and to polished marble or sealed parquet. Besides plastics, waxes have also been successfully used as care additives. Natural waxes, for example carnauba wax, are of primary importance in this regard. In general, these waxes are separately dispersed and then combined with other ingredients. Here, too, alkyl polyglycosides-preferably the relatively long-chain C, APG-can be used. They have been successfully used for the production of very fine-particle natural wax dispersions consisting solely of water, carnauba wax and surfactant. Other waxes, for example montan ester waxes or candelilla wax, can also be dispersed. The anionic and nonionic surfactant combinations used in floor-care products may also contain the relatively short-chain alkyl polyglycosides.Apart from ecological advantages, low foaming, high cleaning performance and high residue transparency are particularly worth mentioning. 3. Alkyl polyglycosides in laundry detergents

For many consumers, laundry detergents are a product they use daily to bring soiled clothing back into a state fit for use. The necessary formulations are marketed in various forms, for example as extruded, powder, paste or liquid detergents. The choice of the particular formulation is determined by the type of soil, by consumer requirements in regard to ease of use and last but not least by the textile and its washing instructions. In addition, ecology has been an important factor in the development of laundry detergents, influencing the way in which they are developed t141. Apart from legislative measures, voluntary agreements by the industry and commercial preferences, the consumer ultimately makes the decision for or against the purchase of a certain product (Figure 19). The alkyl polyglycosides used in detergent formulations are those with an alkyl chain length of C, and a DP of around 1.4 (C12114 APG, Glucopon 600). Textiles Legislation

I

Consumer

t

Ecology

Figure 19. Influences on the development of detergents

Trade

Washing machines

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H. Andree, J. F.Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

As a nonionic surfactant, they are particularly effective against fatty soils. Optimized surfactant systems generally based on mixtures of anionic and nonionic surfactants are used in modern detergent formulations. Alkyl polyglycosides occur in these surfactant mixtures preferably as so-called co-surfactants which have the property of complementing or improving the quantitatively predominant main surfactants in regard to washing performance. Besides performance, the aesthetics of a detergent play an important part. Wool detergents, for example, are intended to produce a rich, stable foam. The consumer associates performance and care with foam. For machine washing, the correct foam height on the one hand determines textile care because the mechanical action on the wash load is reduced. On the other hand, this may cause a distinct reduction of the detergency performance. Alkyl polyglycosides in conjunction with anionic surfactants may alter the foaming behavior of the formulations. A general observation on foaming behavior is not possible, but is to a large extent dependent on the surfactants used and their quantity ratios to one another.

3.1 Liquid detergents Alkyl polyglycosides were first used in liquid laundry detergents in 1989. The composition of a liquid heavy-duty detergent (Table 15)is based on a combination of nonionic surfactants, anionic surfactants, soaps and hydrotropes. The hydrotropes-which do not contribute to cleaning-can be partly replaced by alkyl polyglycosides. It has surprisingly been found that alkyl polyglycosides positively influence the low-temperature and storage stability of such formulations. In addition, triethanolamine (TEA)soaps have been successfully replaced Table 15. General formulations of liquid detergents Ingredients

Heavy-duty liquid detergent concentrate

Anionic surfactants Nonionic surfactants Soap Alkyl polyglycoside Ethanol Glycerine Optical brightener Enzymes (protease, amylase) Fragrances, pearlescence Water

Heavy-duty liquid detergent

[wt.-%I

[wt.-%I

4-9 20-40 10-20 1.5-3 4-9 4-9

4-9 10-20

-k

Light-duty liquid detergent [wt.-%]

3-8

4-9 10-15 4-9 4-9 3 -8

3-8

-

+-

-

10-20 0.5-1.5

+

+

+ +

Balance

Balance

+ Balance

Alkyl Polyglycosides in Hard Surface Cleaners and Laundry Detergents

Reflectance at 460 nm

127

TEA soaps Sodium soaps (TEA = triethanol amine)

[%I 50

Test method: Washing performance test Concentration: 180 ml/wash load (Miele W760)

45

Temperature: 60'C

an ,"

Lipstick

Facial cream

Tea

Red wine

Water hardness: 16'd

Figure 20. Washing performance of heavy-duty liquid detergents

by the similarly acting sodium/potassium soaps [151. The diethanolamine contamination of triethanolamine, which may cause the formation of nitrosamines, was thus avoided. In addition, sodium soaps are less expensive so that, as a net result, the use of alkyl polyglycosides gives the formulation a price advantage. Washing tests show that these new formulations outperform their predecessors (Figure 20). Whereas, in the case of liquid heavy-duty detergents containing optical brighteners and enzymes, the emphasis is on performance, the care aspect is more in the foreground in the case of specialty detergents. The textile influence is dominant in this regard. Liquid specialty detergents are formulated having pH values of 28.5. In order to avoid shifts in color, optical brighteners are not used in the formulations [161. Also consumers expect such products to have an appearance comparable with cosmetic formulations, such as hair shampoos. By using alkyl polyglycosides, it is possible to fulfill these wishes D71. Thus, the viscosity of the liquid is increased by the use of C12/14 APG (Figure 21) 1181. These formulations are simple and safe to handle and for handwashing are preferred to powders. The storage stability of enzymes in liquid formulations is reduced when compared with powders. On account of the high surfactant content of certain formulations, the enzymes are partly deactivated and slowly loose their initial activity upon storage. In order to improve the storage stability of enzymes, such as proteases, lipases, amylases and/or cellulases, in liquid detergents, stabilizers (borates, phosphates, special esters) are added and the surfactant systems are adapted. It has been found that the storage stability of enzymes in liquid detergents can be distinctly improved by the use of C12114APG (Figure 22). Furthermore, alkyl polyglycosides have the advantage over the otherwise typical stabilizers of contributing to the washing performance.

H. Andree,J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

128

Viscosity [mPad Test method: Brookfield

400

Temperature: 25'C

300

Formula: 5 wt.-% Anionic surfactant 12 wt.-% FAEO (7 EO) ic12/14 APG 6 wt.-% Potassium soap Minors Ethanol, glycerine

200

100

LAS

FAS

0, 1.25, 2.5 and 5 wt.-% anionic surfactant in addition

MES

Figure 21. Increase of viscosity of liquid detergents (LAS=linear alkylbenzene sulfonate, FAEO =fatty alcohol ethoxylate, FAS =fatty alcohol sulfate, MES =methyl ester sulfonate)

3.2 Powder/extrudate detergents

Quantitatively the largest group, namely the heavy-duty powder detergents, are based on formulations which remove virtually all the soil types normally encountered (Figure 23). Particular emphasis is placed on washing performance. For this reason, a distinctly higher alkalinity is adjusted so that the pH value of such detergents is in the range from pH 9.5 to 10.5. Soil removal is thus greatly improved. In addition, heavy-duty detergents are provided with a bleaching system. Bleachable stains, such as tea, coffee, red wine, etc., are thus Storage stability [%I

5 wt.-% C12/14 APG containing formula Formula without G,,, APG

100

Test method: Rel. enzymatic activity Temperature: Room temperature

50

Storage time: 56 d

Cellulase

Lipase

Protease

Formula: Heavy-duty liquid detergent 42% surfactants pH 8.0

Figure 22. Stability of enzymes in liquid detergents

129

Alkyl I'olyglycosides in Hard Surface Cleaners and Laundry Detergents

Surfactants 35-45% Builder

Bleaching agents

Figure 23. Composition of a heavy-duty detergent

effortlessly removed. Fat- and oil-containing soils, such as sebum, olive oil, lipstick and facial cream, are difficult to remove, particularly at low temperatures. By using alkyl polyglycosides in powder-form detergents, these stains in particular can be removed considerably more effectively (Figure 24). By additionally using lipases, washing performance can be further increased. Henkel was the first German detergent manufacturer using alkyl polyglycosides in a powder detergent. This detergent without bleach and optical bright-

Reflectance at 460 nm

[%I

Standard + Lipolase@lOO1 without APG

5 wt.-% APG 5 wt-% APG + Lipolase@l00T 60 Test method: Washing performance test

55

50

Concentration: 98 g/wash load (Miele W717)

45

Temperature: 40'C

A0 .-

Oily stains

Dust/ sebum stains

Cosmetic Enzyme Water hardness: stains sensitive stains 16'd

Figure 24. Washing performance of heavy-duty detergents with C12/14APG

130

H. Andree, J. F. Hessel, P. Krings, G. Meine, B. Middelhauve, and K. Schmid

ener is used for fine and delicate textiles like silk and viscose. These high priced textiles need a detergent which is more sensitive to fibres without any damaging during the wash cycle. It is possible to generate a rich and creamy foam by using alkyl polyglycosides. This microfoam reduces the mechanic action during the wash cycle with the big advantage of an increased textile care. On the other hand this product has a very good washing performance mainly during the cold water wash-that means temperatures below 40 "C. Another benefit by using alkyl polyglycosides is a good skin care during wash cycles made by hand. References 1. C. F. Putnik, N. F. Borys, Soap Cosmet. Chem. Spec., June 86 (1986) 34 F. A. Hughes, B. L. Lew, J. Amer. Oil Chem. SOC.47 (1970) 162 2. H. Andree, B. Middelhauve, Tenside Surf. Det. 28 (1991) 413 P. A. Siracusa, HAPPI, April 92 (1992) 100 3. C. Nieendick, K. Schmid, Seifen, Ole, Fette, WachseJournal 121 (1995) 412 4. K. Schmid, 6e Giornale CID-Congress, Rome, 1995

5. K. Schmid in Perspektiven nachwachsender Rohstoffe in der Chemie (H.

Eierdanz, ed.), VCH Verlagsgesellschaft,Weinheim 1996, p. 41 P. Jiirges, A. Turowski in Perspektiven nachwachsender Rohstoffe in der Chemie (H.Eierdanz, ed.), VCH Verlagsgesellschaft,Weinheim 1996, p. 61 6. B. Jackwerth, H.-U. Krachter, W. Matthies, Parfiimerie und Kosmetik 74 (1993) 142 7. W. Sterzel, F. G. Bartnik, W. Matthies, W. Kastner, K. Kunstler, Toxicol. in Vitro 4 (1990) 698 8. H. Andree, B. Middelhauve, World Surfactant Congress, Montreux, Switzerland, 1992 9. W. Matthies, Seifen, Ole, Fette, Wachse Journal 119 (1993) 922 10. H. Heitland, H. Marsen in Surfactantsin Consumer Products CJ. Falbe, ed.), Springer Verlag, Berlin, Heidelberg, New York 1987, p. 306 11. B.-D. Holdt, P. Jeschke, R. Menke,J. D. Soldanski, Seifen, Ole, Fette, Wachse Journal 120 (1994) 42 12. IPP Quality Standard, Seifen, Ole, Fette, Wachse Journal 112 (1986) 371 13. DIN 53 449, Parts 1,2 and 3, Evaluation of Environmental Stress Cracking 14. H. Upadek, P. Krings, Seifen, Ole, Fette, Wachse Journal 117 (1991) 554 15. DE 3920480, Henkel (1989) 16. R. Puchta, P. Krings, H.-M. Wilsberg, Seifen,Ole, Fette, WachseJournal 116 (1990) 241 17. D. Balzer, N. Ripke, Seifen, Ole, Fette, Wachse Journal 118 (1992) 894 18. EP 553099, Henkel (1991)

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

7. Alkyl Polyglycosides-New Solutions for Agricultural Applications Roger Garst Alkyl polyglycosides have been known and available to agricultural formulators for many years. However, the supply, quality and the range of product types was extremely limited. Today, a wide range of alkyl polyglycoside surfactants is available from the Henkel Group. These versatile, biodegradable alkyl polyglycosides are supplied under the trade name of Agrimul@PG. 1. Favorable features

The features of alkyl polyglycosides that commend the products for agricultural applications are at least four in number. First, there are the excellent wetting and penetrating properties. Wetting performance is critical to the formulator of dry agricultural formulations and spreading on plant surfaces is essential to the performance of many pesticides and agricultural adjuvants. Second, no nonionic other than alkyl polyglycoside exhibits comparable tolerance for high concentrations of electrolytes. This property opens the door to applications which were previously inaccessible to typical nonionics and in which alkyl polyglycosides provide the desired properties of nonionic surfactants in the presence of highly ionic pesticides or high concentrations of nitrogen fertilizer. Third, alkyl polyglycosides with a certain range of alkyl chain length do not exhibit the inverse solubility with increasing temperature or “cloud point” phenomenon characteristic of alkylene oxide based nonionic surfactants (see Chapter 4). This removes a significant formulation constraint. Last, the ecotoxicity profiles of alkyl polyglycosides are among the most environmentally friendly that are known (see Chapters 9 and 11).The risk in their Table 1. Product composition-agricultural product line Alkyl polyglycoside Agrimul PG 2076 Agrimul PG 2067 Agrirnul PG 2069 Agrimul PG 2062 Agrimul PG 2065 Agrimul PG 2072

Alkyl chain

Average DP

[%I in water

8/10 (45:55) 8/10 (45:55) 9/10/11 (20:40: 40) 12/14/16 (68:26:6) 12/14/16 (68:26:6) 8/10/12/14/16 (30:37:22:9:2)

1.5 1.7 1.6 1.4 1.6 1.6

60 70 50 50 50 50

132

Roger Garst

use near critical locations, such as surface waters, is greatly reduced in relation to alkylene oxide based nonionic surfactants. 2. Agricultural product line

There are six products in the Agrimul PG product line (Table 1). Agrimul PG 2067 and 2076 are based on C,,,, fatty alcohol, 2069 on C,,,,, 2062 and 2065 on C,,,,, and 2072 on a combination of C, to C16.All Agrimul PG surfactants are supplied as aqueous solutions ranging from 50-70 weight percent. 3. Regulatory status

All products used as components of pesticide formulations in the United States must be approved by the United States Environmental Protection Agency (USEPA) under 40CFR 180.1001c, d,e. Surfactants are considered to be “inert ingredients” that are either inactive or only occasionally active as pesticides. Three Agrimul PG surfactants, 2067,2069 and 2076 are currently approved as inert ingredients. Reflecting their favorable toxicity profiles, these products enjoy the broadest possible approval.They can be used on growing crops or to raw agricultural commodities during, before or after harvest and applied to animals. Henkel has petitioned USEPA to approve the remaining three products. This kind of official recognition is of increasing importance to formulators working to serve the needs of the international agricultural chemical companies. 4. Comparative physical properties

Agricultural formulators are especially interested in the wetting, foaming and emulsification performance of the surfactants with which they work. Results from several standard tests used to measure properties related to these performance properties have been collected (Table 2). Corresponding values for the widely known and used standard nonionic surfactant in this industry, POE(9.5)nonylphenol (NPE9.51, were included for comparison. With the exception of Agrimul PG 2067, all of the alkyl polyglycosides are strong wetting agents. Performance in the Draves test or any other measure of surface tension reduction is not good enough to predict how well any surfactant will penetrate, wet or cause a solution to spread on a target substrate. However, it does provide a standard of comparison which is often used to guide a formulator’s selection of candidates to satisfy a particular application problem. The spreading of an aqueous solution over the waxy cuticle of a leaf can be simulated by using a paraffin coated microscope slide while following the change in contact angle with time (Figure 1). A comparison of one percent solutions of

133

Alkyl Polyglycosides-New Solutionsfor AgriculturalApplications

Table 2. Comparative physical properties Surfactant

Ross miles foam b, [mm] IFT mineral oil c1 [dyn/cml

Draves wettinga1[sl

Agrirnul PG 2076 Agrimul PG 2067 Agrimul PG 2069 Agrimul PG 2062 Agrirnul PG 2065 Agrimul PG 2072 NPE 9.5

0.1%

0.1%

0.1%

27 120 15 20 23 32 11

140 140 140 90 130 145 80

2.9 2.9 1.6 0.8 1.1 1.0 3

ASTM D2281-68 at 25°C b'ASTM D1173-53 at 25'C

"Spinning drop at 25'C

Agrimul PG 2067 and 2069 with POE(9.5)nonylphenol was made following the contact angle at two minute intervals. Agrimul PG 2067 matched the standard in this comparison while Agrimul PG 2069 was better. Bearing in mind the water content of the Agrimul PG surfactants, it is clearly expected that they will perform well as spreading agents and penetrators. Foam can be both an advantage and a disadvantage to the agricultural formulator. Alkyl polyglycosides produce foams which are quite beneficial to the formulator of the field foam marker type products. Field foam markers are used Contact angle YI

Goniometer

50 1

30i1

Model leaf substrate system Paraffin substrate .

*

O

.

o

Surfactants tested 1.0 wt-% in water

.'

. *

.

= . **

.

.

2o

0

I

I

5

10

15

20

25

30

Time [rninl

Figure 1. Wetting/penetrating study

Agrimul PG 2067 Agrimul PG 2069 NPE 9.5

134

Roger Garst

to generate globs of foam that are periodically dropped off the extremities of agricultural machinery, such as planters, cultivators and sprayers, in order to maintain the proper alignment of application. In this way both, under- and over-applicationare avoided.Foam is less desirable in the preparation of formulations or when the formulations are mixed with water in a spray tank just before application. The Ross Miles data place the performance of the Agrimul PG surfactants within a standard reference system so that the formulator can effectively manage the overall performance of his system. The ability of a surfactant to reduce interfacial tension is indicative of its utility value as an emulsifier 111 (see Chapter 4). Agrimul PG surfactants demonstrate superior potential as emulsifiers through their efficient lowering of interfacial tensions. They have been found to be useful in the preparation of microemulsions and concentrated emulsions of pesticide actives. Another product type, suspoemulsions, in which both an emulsion and a dispersion are present, also benefits from the inclusion of an alkyl polyglycoside. Watersoluble and highly ionic pesticides occasionally have to be combined with oil-soluble pesticides that are usually supplied as emulsion concentrates. These combination products can be stabilized with alkyl polyglycosides. The stability of spray tank mixes is often compromised by the combinations of pesticides used to control multiple target species with a single application. These mixes often require the addition of an agent that will result in a compatible mixture. Historically, compatibilizers have been based on anionic surfactants, such as phosphate esters. Laboratory tests have demonstrated that Agrimul PG 2067, 2076 and 2069 are excellent candidates for solving this important problem. No other nonionic surfactants have remarkable utility value in this application. 5. Salt tolerance and adjuvancy

One of the most important developments in the recent history of herbicides has been the introduction of several new classes of products that are post-applied. Post application occurs after the desired crop has germinated and is in the early growth stages. This technique allows the farmer to specifically identify and target the offending weed species instead of following the preemergent route which seeks to anticipate what might happen. These new herbicides enjoy very low application rates thanks to their high activity. This use is economical of weed control and favorable to the environment. It has been found that the activity of many of these post-applied products is potentiated by the inclusion in the tank mix of a nonionic surfactant. Polyalkylene ethers serve this purpose quite well. However, the addition of nitrogen-containing fertilizer is also beneficial and often herbicide labels recommend, indeed specify, the use of both adjuvants together. In such salt solutions,

135

Alkyl Polyglycosides-New Solutions for Agricultural Applications

a standard nonionic is not well tolerated and can “salt out” of solution. Beneficial advantage can be taken of the superior salt tolerance of the Agrimul PG surfactants 2067, 2069 and 2076. Concentrations of 30 Yo ammonium sulfate can be added to 20% solutions of these alkyl polyglycosides and remain homogeneous (Table 3). Two percent solutions are compatible with up to 40% ammonium sulfate. Agrimul PG 2076 can be directly substituted for Agrimul PG 2067 in any of these results and is an even better wetting agent. Field trials have shown the alkyl polyglycosides to provide the desired adjuvant effects of a nonionic surfactant. 6. New adjuvant formulations The combination of properties just discussed, wetting, salt tolerance, adjuvancy and compatibilization, affords the opportunity to consider combinations of additives that can create multiple-feature adjuvants. Such adjuvants are highly desired by farmers and custom applicators since they remove the inconvenience of measuring and mixing several separate adjuvants. Of course, this also reduces the possibility of mixing errors when the product is packaged in predetermined quantities corresponding to the label recommendations of the pesticide manufacturer. An example of such a combination adjuvant product would be one that included a methyl ester or phytobland petroleum spray oil plus a concentrated nitrogen fertilizer solution compatibilized with an alkyl polyglycoside. Preparation of a combination such as this and have it exhibit adequate storage stability is a formidable challenge. Such products are now being introduced onto the market. Table 3. Electrolyte tolerance of Agrimul PG productsa’ Product

10% NPE 9.5 2 % 2 phase NPE 9.5 5% 2 phase Agrimul PG 2067 2 % 1 phase Agrimul PG 2067 5 % 1 phase Agrimul PG 2067 10% 1 phase Agrimul PG 2067 20% 1 phase 1 phase Agrimul PG 2069 2 % Agrimul PG 2069 5 % 1 phase Agrimul PG 2069 10% 1 phase Agrimul PG 2069 20% 1 phase a) Ammonium sulfate solubility at 25 ’ C

Ammonium sulfate 20% 30% 2 phase 2 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase

2 phase 2 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase 1 phase

40% 2 phase 2 phase 1 phase 1 phase 2 phase 2 phase 1 phase 1 phase 2 phase 2 phase

136

Roger Garst

7. Adjuvant efficacy

Agrimul PG 2069 has been extensively tested with several post-applied herbicides in field trials over the period from1992 to 1995 [21. It was compared for efficacy with the adjuvant recommended on the pesticide label by the manufacturer. The types of recommended adjuvants included crop oils which are emulsifiable concentrates of phytobland petroleum oils, methylated seed oils which are supplied as emulsifiable concentrates of various fatty acid methyl esters and other nonionic surfactants. The standard among other nonionic surfactants is a formulated product containing mostly POE (9)nonylphenol. Studies were conducted on the two major row crops of the United States, namely soybeans and corn (Figures 2 and 3). The examples shown were taken from work with soybeans to illustrate the overall conclusions drawn from the studies that Agrimul PG 2069 was as effective as or more effective than the standard adjuvants recommended on the product label. 8. Environmental effects

Alkyl polyglycoside surfactants present very favorable ecotoxic profiles. Details are discussedin Chapters 9 and ll. They are extremely mild to aquatic biota and fully biodegradable. These features underly the broad approval that these surfactants enjoy under the USEPA regulations. Irrespective of whether the objective is to formulate a pesticide or an adjuvant, the knowledge that alkyl

[%I

100

14 days I 28 days

80

Rate = % v/v

Control

X-77 = nonionic spray adjuvant, 90% AS (Loveland Industries)

60 40

20

None

0.25 x-77

0.25 2069

0.50 2069

Figure 2. Control of giant foxtail in soybeans with Assure II (Du Pont Agricultural Products)

Alkyl Polyglycosides-New Solutionsfor Agricultural Applications Control [%I

loo

El 14 days I28 days

1

None

137

0.75

1.5

Sun-IT II

Sun-IT II

0.25 2069

0.50 2069

Figure 3. Control of common lambsquarters in soybeans with Pursuit (American Cyanamid Company)

polyglycosides provide functionality with minimal environmental and handling risks associated with their choice makes that choice increasingly comfortable to the formulator. 9. Conclusions

Agrimul PG alkyl polyglycosides are new, naturally derived, biodegradable and environmentally favorable surfactants with a spectrum of performance properties that commend ther consideration and use by progressive formulators of pesticide and agricultural adjuvant products. As the world seeks to maximize agricultural production while minimizing adverse environmental impact, Agrimu1 PG alkyl polyglycosides will help to ensure that outcome. References

R. H. Garst, R. Klima in Proceedings Fourth International Symposium on Adjuvants for Agrochemicals (R. E. Gaskin, ed.), 1995,p. 06 R. A. Aleksejczyk in Pesticide Formulations and Application Systems, Vol. 12, ASTM 1146 (B. N. Devisetti, D. G. Chasin, P. D. Berger, eds.), American Society for Testing and Materials, Philadelphia, 1993 2. J. Mueninghoff, Field Trial Summary: Alkyl Polyglycosides, Henkel Corporation, Emery Group Publication, 1996 1.

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

8. New Nonionic Derivatives of Alkyl PolyglycosidesSynthesis and Propetties Oliver Rhode, Manfred Weuthen, and Dieter Nickel

Today, alkyl polyglycosides are available in sufficient quantities and at competitive costs [ 1I so that their use as a raw material for the development of new speciality surfactants based on alkyl polyglycosides is arousing considerable interest. Thus, the surfactant properties of alkyl polyglycosides, for example foam and wetting, could be modified as required by chemical transformation. The derivatization of alkyl polyglycosides is currently being pursued with great commitment [21 (see also Chapter 13).A broad range of alkyl polyglycoside derivatives can be obtained by using relatively simple methods, for example nucleophilic substitution. Besides the reaction to esters or ethoxylates, ionic alkyl polyglycoside derivatives, such as sulfates and phosphates, can also be synthesized (Figure 1). Starting from alkyl polyglycosides having alkyl chains (R) of 8,10,12,14 and 16 carbon atoms ( C g to CI6)and an average degree of polymerization (DP) of 1.1 to 1.5,three series of alkyl polyglycoside derivatives were prepared. In order to investigate the change in the surfactant properties hydrophilic or hydrophobic Carbonates Glycerol ethers

z

t DP = 1.1 - 1.5 R = C8tO C16

haoR

c

A F Sulfosuccinates

/ Quaternaries

f

6

HOHO Esters

Butyl

4

Phosphates

EDoxide adducts

Figure 1. Alkyl polyglycoside derivatives

ethers

-

DP-I

I

{

Ether carboxylates

Sulfates

'

Ethoxylates

lsethionates

140

Oliver Rhode, Manfred Weuthen, and Dieter Nickel

substituents were introduced leading to alkyl polyglycoside glycerol ethers 131, carbonates [41 and butyl ethers 151. In view of their numerous hydroxyl groups, alkyl polyglycosides are overfunctionalized molecules. By far the most alkyl polyglycoside derivatizations are carried out by chemical transformation of the free primary hydroxyl group at the C6atom. Although primary hydroxyl groups are more reactive than secondary hydroxyl groups, this difference is not sufficient in most cases to achieve a selective reaction without protective groups. Accordingly, derivatization of an alkyl polyglycoside can always be expected to produce a product mixture of which the characterizationinvolves considerable analytical effort. A combination of gas chromatography and mass spectrometry was shown to be the preferred analysis method. In the synthesis of alkyl polyglycoside derivatives, it has proved effective to use an alkyl polyglycoside with a low DP value of 1.1, in the following referred to as alkyl monoglycosides. This leads to less complex product mixtures and as a consequence to less complicated analyses. 1. Synthesis of alkyl polyglycoside glycerol ethers

The synthesis of alkyl polyglycoside glycerol ethers was carried out by three different methods (Figure 2, instead of the alkyl polyglycoside mixture, only the alkyl monoglycoside is shown as the educt). The etherification of alkyl polyglycoside with glycerol by method A proceeds under basic reaction conditions. The ring opening of an epoxide by method B likewise takes place in the presence of basic catalysts. An alternative is the reaction with glycerol carbonate by method C which is accompanied by the elimination of CO, and which presumably proceeds via an epoxide as intermediate stage. The reaction involved in nucleophilic substitution by method A is particularly easy to control. Alkyl polyglycoside and glycerol are initially introduced into the reactor in a ratio of 1:2 and melted in a nitrogen atmosphere. When the reaction mixture is stirrable, 2 Yo by weight of potassium hydroxide are added.

Figure 2. Synthesis of alkyl polyglycoside glycerol ethers

New Nonionic Derivativesof Alkyl Polyglycosides

141

The reaction mixture is then heated 200°C over a period of 7 hours during which the water formed is continuously distilled off to displace the equilibrium as far as possible to the product side. As expected, alkyl polyglycoside di- and triglycerol ethers are formed in addition to the monoglycerol ether. Another secondary reaction is the self-condensation of glycerol to form oligoglycerols which are capable of reacting with the alkyl polyglycoside in the same way as the glycerol. Such high contents of higher oligomers can be entirely desirable because they further improve the hydrophilicity and hence for example the water solubility of the products. After the etherification, the products can be dissolved in water and bleached in a known manner, for example with hydrogen peroxide. Under these reaction conditions, the degree of etherification of the products is independent of the alkyl chain length of the alkyl polyglycoside used. Figure 3 shows the percentage contents of mono-, di- and triglycerol ethers in the crude product mixture for four different alkyl chain lengths. Reaction of the Clz alkyl polyglycoside provides a typical result. According to a gas chromatogram, mono-, di- and triglycerol ethers are formed in a ratio of approximately 3:2:1. The total content of glycerol ethers is around 35 To. 2. Synthesis of alkyl polyglycoside carbonates

Alkyl polyglycoside carbonates were prepared by transesterification of alkyl monoglycosides with diethyl carbonate (Figure 4).In the interests of thorough mixing of the reactants, it has proved to be of advantage to use the diethyl carbonate in excess so that it serves both as transesterification component and GC 40

[%I

63 Mono Di

I Tri

30

mc

20

10 HO n=

10

12

14

16

Figure 3. Composition of alkyl polyglycoside glycerol ethers

Oliver Rhode, Manfred Weuthen, and Dieter Nickel

142

Figure 4. Synthesis of alkyl polyglycoside carbonates

as solvent.2 Mole-% of a 50% sodium hydroxide solution are added dropwise to this mixture with stirring at around 120"C. After 3 hours under reflux, the reaction mixture is allowed to cool to 80 "C and neutralized with 859'0 phosphoric acid. The excess diethyl carbonate is distilled off in vacuo. Under these reaction conditions, one hydroxyl group is preferably esterified. The ratio of remaining educt to products is 1:2.5: 1 (Monoglycoside:Monocarbonate :Polycarbonate). Besides the monocarbonate, products with a relatively high degree of substitution are also formed in this reaction. The degree of carbonate addition can be controlled by skilled management of the reaction. For a C,, monoglycoside, a distribution of mono-, di- and tricarbonate of 7:3 :1 is obtained under the reaction conditions just described (Figure 5). If the reaction time is increased to 7 hours and if 2 moles of ethanol are distilled off in that time, the main product is C,, monoglycoside dicarbonate. If it is increased to 10 hours and 3 moles of GC .f%1_ 80

60 40

20

3

7

10

2 mol EtOH distilled off

3 mol EtOH distilled off

Time [hl

Figure 5. Alkyl polyglycoside carbonates-degree of carbonate substitution

143

New Nonionic Derivatives of Alkyl Polyglycosides

ethanol are distilled off, the main product ultimately obtained is the tricarbonate. The degree of carbonate addition and hence the hydrophilic/lipophilic balance of the alkyl polyglycoside compound can thus be conveniently adjusted by variation of the reaction time and the distillate volume. 3. Synthesis of alkyl polyglycoside butyl ethers

A property of alkyl polyglycosides often in demand is enhanced foaming. In many applications, however, this ability is actually regarded as a disadvantage. Accordingly, it is also of interest to develop alkyl polyglycoside derivatives which combine good cleaning performance with only a slight tendency to foam. With this goal in mind alkyl polyglycoside butyl ethers were synthesized. It is known in the literature that alkyl glycosides can be end-capped with alkyl halides or dimethyl sulfate in aqueous alkaline solutions [GI. On an industrial scale, the reaction in aqueous solution is a disadvantage because concentrated water-free products cannot be obtained without additional working-up steps. Therefore, a water-free process was developed, which is outlined in Figure 6. The alkyl polyglycoside is initially introduced into the reactor with an excess of butyl chloride and heated to 80 "C. The reaction is initiated by addition of potassium hydroxide as the catalyst. On completion of the reaction, the reaction mixture is neutralized, the potassium chloride precipitate is filtered off and the excess butyl chloride is distilled off. The product is composed of various alkyl polyglycosides and alkyl polyglycoside butyl ethers. According to GC analysis, the ratio of alkyl monoglycoside, alkyl monoglycoside rnonobutyl ether and alkyl monoglycoside polybutyl ether is 1:3 :1.5. The course of the reaction for the etherification of a C,, alkyl polyglycoside is shown in Figure 7. The monoglycoside content decreases from around 70% to less than 200/0. At the same time, the value for the monoether rises to 500/0. The more monobutyl ether present, the more polybutyl ethers can be formed therefrom. Only after 24 hours is there any significant formation of polybutyl ethers. As expected, the content of polyethers increases with increasing reaction time. However, a value of 20% is not exceeded. The average degree of etherifi-

HO % "OR R = C8 to C16

-

CI KOH

t

8O"C, 7 d

Figure 6.Synthesis of alkyl polyglycoside butyl ethers

H HO O

a

O OH

R

144

Oliver Rhode, Manfred Weuthen, and Dieter Nickel

HO

OH

l2

60 -

Monoether

40 -

20 -

_- - - _ _ - - _ _ - _- - - Polyether

,

Figure 7. Reaction of Cl2 alkyl polyglycoside with butylchloride

cation is one to three butyl groups per alkyl glycoside unit. The best results are obtained with a C,, alkyl polyglycoside. In the case of the alkyl polyglycoside butyl ethers where n = 8 or 16, the results deteriorate. It is clear from these three examples that derivatives of alkyl polyglycosides are readily accessible. The particular application envisaged is also determined by the surfate-active properties of these derivatives. 4. Interfacial properties [71

To characterize the interfacial properties of alkyl polyglycoside derivatives, surface tension/concentration curves were recorded and the critical micelle concentrations (cmc)and the plateau surface tension values above the cmc were determined from them. The interfacial tension against two model substancesoctyl dodecanol and decane-were investigated as further parameters (see Chapter 4). The cmc values obtained from these curves are shown in Figure 8. The corresponding data for a C,,alkyl monoglycoside and a C,,,,, alkyl polyglycoside are included for comparison. It can be seen that alkyl polyglycoside glycerol ethers and carbonates have higher cmc values than alkyl polyglycosides of comparable chain length whereas the cmc values of the monobutyl ethers are somewhat lower than those of the alkyl polyglycosides. The plateau surface tension values above the cmc were determined by further evaluation of the surface tension/concentration curves. These values are set out in Table 1. It can be seen that all the surfactants investigated have high surface

New Nonionic Derivatives of Alkyl Polyglycosides

145

cmc [g/ll

I

a Monoglycerol ethers

ox

X = CH&HIOH)CH20H

10

b Carbonates X = C(0)OEt

1

c Butyl ethers X = CH,CH,CH$H,

0,1

d Alkyl polyglycoside X=H

0 01

0.001 n = 10 12 14 a

12 b

8 12 14 12 C

1212/14 d

Figure 8. crnc values of alkyl polyglycoside derivatives

activity above the cmc. Only the alkyl polyglycoside tricarbonate does not compare as well because of its poor solubility. The interfacial tension measurements were carried out with a Kriiss spinning drop tensiometer. To simulate practical conditions, the measurements were performed in hard water (270ppm Ca :M g = 5 :1)at a surfactant concentration of 0.15 g/l and at 50 "C. Figure 9 shows a comparison of the interfacial tension of C 12 alkyl polyglycoside derivatives against octyl dodecanol. The C,, monobutyl ether has the highest interfacial tension and hence the lowest interfacial activity whereas the C, monoglycerol ether is substantially at the level of the C,, polybutyl ether. The C,, alkyl polyglycoside included for comparison lies at the level of the last two alkyl polyglycoside derivatives mentioned. Overall, the interfacial tension values against octyl dodecanol are relatively high. This means that, for practical applications, it is important to ensure that the surfactant mixtures used have a synergism towards polar oils. Figure 10 shows the values for the interfacial tension of C,, alkyl polyglycoside derivatives against decane. The polybutyl ether is somewhat lower compared with C,, alkyl polyglycoside and has a more favorable value than the monobutyl ether. The interfacial tension of the monoglycerol ether is between the two alkyl polyglycoside butyl ethers. The unfavorable value for the alkyl polyglycoside tricarbonate, which is attributable to its poor solubility, even at 50"C, contrasts with very low surface interfacial tensions for mono- and dicarbonate. Compared with the C, alkyl polyglycoside, the monocarbonate has a very favorable value for an individual surfactant.

Oliver Rhode, Manfred Weuthen, and Dieter Nickel

146

Table 1. Reduction of surface tension by AFG derivatives Surfactant

Surface tension [mN/ml

Clo Alkyl polyglycoside glycerol ether CI2Alkyl polyglycoside glycerol ether

28 28 26

C14 Alkyl polyglycoside glycerol ether

Alkyl polyglycosidetricarbonate

27 28 30

Alkyl polyglycoside monobutyl ether Alkyl polyglycoside monobutyl ether C14 Alkyl polyglycoside monobutyl ether C12 Alkyl polyglycoside polybutyl ether

27 28 27 27

C12

Alkyl polyglycoside monocarbonate

C12 Alkyl polyglycoside dicarbonate C12 C8

C12

C12

Alkyl polyglycoside

25 27

C12/14Alkyl polyglycoside

The dependence of interfacial tension on the alkyl chain length of various alkyl polyglycoside monoglycerol ethers is shown in Figure 11. Interfacial tension against decane decreases significantly with increasing chain length, the high value of the Cloglycerol ether being attributable to the fact that the cmc is y [mN/rnl

Monoglycerol ether X = CH,CH(OH)CH,OH

Concentration: 0.15 g/l Water hardness: 16 'dH

Butyl ethers X = CI$CH$H,CH,

Temperature: 50 'C Test oil: octyl dodecanol Time: 15 min

Alkyl polyglycoside X=H

Figure 9. Reduction of interfacial tension against octyl dodecanol

New Nonionic Derivativesof Alkyl Polyglycosides

147

ox

Y [mN/ml

Concentration: 0.15 g/l Water hardness: 16 'dH Time: 15 min Temperature: 50°C Test oil: decane

-.

a Monoglycerol ether X = CH2CH(OH)CH*OH

3

2

b Carbonates X = C(0)OEt

1

c Butyl ethers X = CH,CH$H,CH, a

b

d

C

d Alkyl polyglycoside X=H

Figure 10. Reduction of interfacial tension against decane

not reached at 0.15 g/l. Accordingly, it is important to ensure that the cmc of a surfactant mixture is lower than that of the Cloglycerol ether. The wetting power of two alkyl polyglycoside monocarbonates and the corresponding alkyl polyglucosides is illustrated in Figure 12.The wetting times were measured for two different water hardness values. The times for the monocarbonate with an alkyl chain length n of 8 are about half as long as for the corresponding alkyl polyglycoside. Less favorable values were obtained for the C,, alkyl polyglycoside monocarbonate than for the C,,,,, alkyl polyglycoConcentration: 0.15 g/l Water hardness: 16 "dH Time: 15 rnin Temperature: 50 'C Test oil: decane

Y [rnN/rnl

51

n=

10

12

14

Figure 11. Reduction of interfacial tension by alkyl polyglycoside monoglycerol ethers

148

Oliver Rhode, Manfred Weuthen, and Dieter Nickel

Time [secl

Conditions: DIN 53901 (1 g/l, 25 'C)

>300

300

O'dH

250

116'dH

200 150

HO

100 50 n=8

n=12

Carbonates X = C(0)OEt

n = 8,lO

n = 12,14

Alkyl polyglycosides X=H

Figure 12. Wetting time of alkyl polyglycoside carbonates

side. This monocarbonate shows poor wetting behavior above all at a water hardness of 1 6 O d H . The results of the foam tests are set out in Figure 13.The foaming behavior of various alkyl polyglycoside monoglycerol ethers and monocarbonates was measured by comparison with C,,alkyl polyglycoside for two water hardness [rnll 600

Conditions: DIN 53902 (0.5 g/l, 40°C)

500

30 sec 1 2 0 rnin a: O'dH

400

300 200

100 n=lO n=12 n=14 Monoglycerol ethers X = CH&H(OH)CH,OH

n=12

n = 8 n=12 Monocarbonates X = C(0)OEt

Figure 13. Foam volume of alkyl polyglycoside derivatives

b: 16"dH

New Nonionic Derivatives of Alkyl Polyglycosides

149

values in the absence of fatty soil. The measurements were conducted in accordance with DIN 53902. The C,, and C,, alkyl polyglycoside monoglycerol ethers produced a larger foam volume than the C,, alkyl polyglycoside. Foam stability is significantly greater in the case of the C,, monoglycerol ether than in the case of the C,, derivative at 1G"dH. The C,, alkyl polyglycoside monoglycerol ether does not compare with the C,, and C,, derivatives in its foaming power and, overall, rates worse than the C,, alkyl polyglycoside. The monocarbonates with alkyl chain lengths n of 8 and 12 are distinguished by very low foam volumes, as would be expected of a hydrophobic alkyl polyglycoside derivative.

References 1. J. Kahre, H. Tesmann, Seifen, Ole, Fette, Wachse Journal 121 (1995) 598

2.

3. 4. 5. 6. 7.

C. Nieendick, K. Schmid, Seifen, Ole, Fette, Wachse Journal 121 (1995)412 F. Hirsinger, K. P. Schick, Tenside Surf. Det. 32 (1995) 193 B. D. Holdt, P. Jeschke, R. Menke, H.-D. Soldanski, Seifen, Ole, Fette, Wachse Journal 120 (1994) 42 W. Ruback, S. Schmidt in Carbohydrates as Organic Raw Materials I11 (H. van Bekkum, ed.), VCH Verlagsgesellschaft, Weinheim, 1996, p. 231 B. Fabry, M. Philipp, J. E. Drach, HAPPI, August 94 (1994) 111 J. Thiem, Th. Backer, Tenside Surf. Det. 26 (1989) 318 DE 4335956 Al, Henkel(1993) WO 93120089, Henkel (1992) WO 93106115, Henkel (1991) El?-A1 0364852, BASF (1988) Henkel KGaA, unpublished results

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH VerlagsgesellschaftmbH,1997

9. Toxicology a Alkyl Polyglycosides Walter Aulmann and Walter Sterzel

Acquiring knowledge of the potential effects of substances on human beings and their environment is among the basic tenets in the worldwide “Responsible Care” initiative. In order to take responsible care seriously into account, manufacturers must ensure that their products do not endanger the health of consumers, the workforce or the general public. This responsibility relates both to direct exposure during production and use and to indirect exposure via the environment, including food and water. It is a current trend that product safety is increasingly regarded as part of product quality. The provider of chemical products assumes his responsibilities both retrospectively and prospectively. The retrospective approach includes indepth toxicological safety evaluations, participation in poison information systems, post-marketing surveillance, including consultation about appropriate handling and use and-last but not least-observation of the scientific and regulatory environment. Prospectively, toxicologists are consulted in the early stages of product development. Another prospective activity is the setting of safety standards which go beyond regulatory requirements. Such standards apply to the mode of both data generation and data evaluation. The final goal is the drawing of the toxicological profile of a substance. This is done by positioning its properties within the matrix of the classical antonyms of toxicology, local versus systemic effects, acute versus retarded effects and reversibility versus irreversibility (Figure 1). Retarded

m‘‘ 1

Reversible

9

+Systemic

Local

Figure 1. The dimensions of biological effects

/I

Irreversible

~

L

Acute

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Walter Aulmann and Walter Sterzel

Thus, as a result of a decade-long evolution, internal and external standards are available which could be applied to the systematic approach for the product safety of alkyl polyglycoside. Toxicologicalinvestigations started at a very early stage of product development. In the main, they addressed all the questions which have to be answered by any manufacturer who takes his responsibility for health and safety seriously: is my product toxic if swallowed?What effects could dermal contact have-systemic intoxication, irritation, corrosion or sensitization? Could accidental contact with the eyes cause serious damage? Does the product have any irreversible effects? What is its fate in the body? To find answers to these questions, a step-by-step toxicological testing program was undertaken. All studies within this program were conducted in compliance with internationally accepted guidelines, especially the “OECDGuidelines for the Testing of Chemicals” and the “Principles of Good Laboratory Practice” [lI. 1. Acute toxicity

To assess whether a product could be harmful or even toxic after ingestion or dermal contact, information is needed on its acute systemic toxicity. By definition, acute toxicity is the adverse effect occurring within a short time of administration of a single dose of a substance or multiple doses given over a short period of time. One important criterion of acute toxicity is the LD,,, a statistically derived single dose of a substance that can be expected to cause death in 50 percent of test animals when administered by the oral route. The acute toxicity of alkyl polyglycoside was comprehensively investigated. Variations of the test conditions involved homologues using either the shortchain (C,,,, APG) or the medium-chain (C,,,,, APG) alkyl polyglycoside. Other modifications included the application route which was either oral or dermal. 1.1 Acute toxicity after ingestion

Tests were performed in accordance with OECD Guideline No. 401 and also followed the US Toxic Substances Control Act (TOSCA-40 CFR 798)and the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA-40 CFR 158,162). Rats were used as test animals. Prior to the application of the test substance,the animals were acclimatized to the laboratory for at least 4 days, during which they had access ad libitum to a conditioned diet and tap water. The rats were then starved overnight and the substance was applied by gavage. During the post-administration period, the animals were observed for general signs of toxicity and death. Weight was recorded at certain intervals. At the end of the 14-day observation period, the animals were sacrificed, weighed and subjected to a general necropsy.

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The toxicity of alkyl polyglycoside was expected to be low. Accordingly, the acute toxicity studies were limit tests. In limit tests, only one high dose exceeding at least 2000 mg/kg is administered to a single group. Owing to different regulatory backgrounds, different limit doses were administered, namely 2000 or 5000 mg/kg body weight. The limit dose in the European Union is 2000 mg/kg body weight. Under EU regulations, an acute oral toxicity does not bring about a hazard classification providing that the LD,, exceeds 2000 mg/kg body weight. The results of the tests are set out in Table 1. None of the animals died during the observation period [2,3,41. When extremely high doses of 5000 mg/kg body weight were administered, few animals showed signs of intoxication. The records mention such symptoms as slight depression, urine stains, saliva stains around the mouth and reddening around the eyes. These symptoms can also be attributed to the high dose applied and cannot be regarded as a substance-specific effect. This is why the OECD and the EU recommend a dose of 2000 mg/kg body weight as the limit dose in order to avoid the volume effect as a misleading factor. Thus, it may be concluded that, irrespective of the type of alkyl polyglycoside, even extreme doses of 5000 mg/kg body weight were below the LD,,. The structure of the various test substances did not influence toxicity. Biological data did not correlate with the chain length or with the degree of polymerization. Moreover, alkyl polyglycoside did not have any toxicity on a specific strain. Neither of the two strains tested, namely Wistar and Sprague Dawley, showed specific sensitivity towards alkyl polyglycoside. On the basis of these tests, there would be no risk from alkyl polyglycosides if swallowed. Under EU and US classification rules, alkyl polyglycosides do not require hazard classification or labelling.

Table 1. Alkyl polyglycosides (C8/10-,C12114APG) tested on acute oral toxicity in rats Chain length Degree of polymerization Concentration [% active substance] Rat strain Number of animals Sex, m=male - f=female Mortality Animals with gross necropsy observations LD50 [mg/kg body weight1 Reference

c12/14

c8/10

c12/14

1.6 50 Sprague-Dawley 5-5 m-f 0/5 - 0/5 0/5 - 0/5

1.6 50 Sprague-Dawley 5-5 m-f 0/5 - 0/5 0/5 - 0/5

1.4 60 Wistar 2-2 m-f 0/2 - 0/2 0/2 - 0/2

>5000 [21

>5000 131

>2000 [41

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Walter Aulmann and Walter Sterzel

1.2 Acute toxicity after contact with the skin

According to application patterns, the intended or envisaged use of alkyl polyglycosides is likely to involve dermal contact. Information is thus needed on potential health risks arising from short-term exposure of the skin. Tests were carried out under OECD Guideline No. 402 and also under the TOSCA and FIFRA regulations. The substance was applied to at least 10% of the surface area of rabbits which had been acclimatized for at least 4 days before being tested. A porous gauze dressing was wrapped around the animal and secured with tape. After 24 hours, the dressing was removed and any unabsorbed sample was gently wiped away with a towel moistened with water or other appropriate solvent. The animals were observed for signs of toxicity and behavioural changes at least once a day . Symptoms were to include erythema, oedema, atonia, desquamation, necrosis, coriaceousness, fissuring and other signs of irritation or injury. Body weight was recorded at certain intervals (after 0, 7 and 14 days). A general necropsy was performed at the end of the 14 day observation period. In this case, too, the protocol followed the procedure of a limit test. Two different types of alkyl polyglycoside were tested. The results are shown in Table 2. In neither case did any substance-related fatalities occur [5,61. Accordingly, it is safe to conclude that 24 hours’ contact with the skin is harmless. On the basis of these data, contact with the skin is unlikely to involve any risk. Alkyl polyglycoside is not acute toxic after dermal application under the EU classification scheme. 2.

Dermal irritation

Irritation to the skin and eyes may be caused by accident. Whereas, in general, the consumer is only exposed to alkyl polyglycoside in dilute form, contact with the undiluted chemical is also possible, particularly during production and handling. Accordingly, information is required on the surface effects of neat alkyl polyglycoside on the skin which might possibly be characterized either as irritation or as corrosion. Dermal irritation/corrosion is defined as the production of reversiblehrreversible changes to the skin following application of the test substance. 2.1 In-vitro studies

The isolated perfused bovine udder skin (BUS)model 171was originally introduced as a natural in-vitro model to study the interaction of xenobiotics with the skin. Udders from slaughtered cows are perfused in the laboratory with a

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Toxicologyof Alkyl l'olyglycosides

Table 2. Alkyl polyglycosides (C8/10-rC12/14APG) tested on acute dermal toxicity in rabbits Chain length Degree of polymerization Concentration [% active substance] Rabbit strain Number of animals Sex, m=male - f=female Mortality LD50 [mg/kg body weight] Reference

c8/10

c12/14

1.6 50 New Zealand White 5-5 m-f 0/5 - 1/5* >2000 [51

1.6 50 New Zealand White 5-5 m-f 0/5 - 0/5 >zoo0 [61

*One mortality due to Tyzzer's disease

cellfree, oxygenized liquid (Tyrode's solution). The udder skin remains over eight hours in viable state which is also monitored biochemically and physically. Under the in-vitro conditions metabolization reactions comparable to living skin take place in perfused skin models only. Due to this state additional information concerning time-dependent skin irritation (modified methyl tetrazolium assay, measurement of the prostaglandin E2 concentration) after topical exposure in a Finn' chamber can be obtained in punched skin biopsies. The skin compatibility of alkyl polyglycosides (3 Yo, 100/0, pH 5.5)was tested in the BUS model performing an occlusive exposure up to five hours. The biological effects in the epidermal and dermal layers were characterized by means of prostaglandin E2 assay and methyl tetrazolium salt dye conversion (MTT). The results in general demonstrate a very good skin mildness of alkyl polyglycosides even after an occlusive exposure period of five hours regarding cytotoxicity or irritancy, for example synthesis of preinflammatory mediators. After one hour of exposure the cytotoxicity is predominantly influenced by physicochemical processes. Alkyl polyglycoside 3 O/o did not show a cytotoxic potential (MTT values in relation to untreated sites) during the first hour of exposure. Even the application of alkyl polyglycoside 10O/o induced less cytotoxic impairment to the epidermal and dermal layers after one hour exposure than the application of SLS 3 Yo (Sodium Lauryl Sulfate, pH 5.5) which is used for comparison as a widely used model skin irritant. The corresponding prostaglandin E2 concentration showed no dose-relationship after the exposure period of one respectively five hours to alkyl polyglycoside 3 Yo and 10 Yo in contrast to the increase of prostaglandin E2 synthesis observed after the topical application of SLS 3 Yo and 100/0 [81.

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2.2 In-vivo studies Investigations were conducted in accordance with OECD Guideline No. 404, the international standard method for testing dermal irritation. Several tests with alkyl polyglycoside were carried out. The substance was applied to one flank of the shaved back of rabbits. The untreated area of each animal served as control. The test conditions were varied in regard to chain length and concentration. The results are shown in Table 3. The data provide clear information on structure-response and concentration-response relationships. Short-chain (C,,,,) alkyl polyglycoside in commercial concentrations would appear to have no irritating effects [9,101. Mediumchain (C,,,,,) alkyl polyglycosides in the same concentration range (40 to 600?0) are irritating to the skin 111,12,131. The irritation responses justifying classification start at concentrations exceeding 30 Yo, i. e. concentrations below 30 O!o cannot be classified as “irritating to the skin”[14,151.With increasing concentration, the number of animals responding with erythema increases. The unusual value from the primary dermal irritation index (PDII) detected in the test with the 30 Yo sample is attributable to a single animal which showed extreme responses. Disregarding this animal, the corrected PDII is 2.2. At 60 To, a plateau is reached. Concentrations of 60 Yo and higher produced significant erythema in all the test animals. The same applies to animals which had received a 100 Yo alkyl polyglycoside sample: a C,,,,, alkyl polyglycoside in a concentration of 1000/0 was irritating, but not corrosive MI. Dermal irritation was not pH-dependent (data not shown in the table). A sample with a pH of 7 produced responses similar to those of the commercial product with a pH of 11.5 [17,181. From the results of the skin irritation tests, it can be concluded that C,, alkyl polyglycoside and C,,,,, alkyl polyglycoside in a concentration of up to 3 0 % do not require classification or labelling. C,,,,, alkyl polyglycosides in concentrations of >30 Yo to 100Yo fall within the R 38 (“irritatingto the skin”)category of the EU risk classification.

3. Mucous membrane irritation (eye irritation) Accidents affecting the eyes are always a possibility and, to the person involved, may appear disastrous. Since skin patches with alkyl polyglycoside did not cause any corrosion, even in the highest concentrations, additional investigations into the effects on mucous membrane were called for in order to obtain information on possible damage to the eyes. The aim of the investigations to be conducted was to evaluate the potential of alkyl polyglycoside to cause eye irritation or corrosion with reversible or

1 100

::

[% active

0/3 0/3 2/3 0/3 1/6 2/3 4/4 3/3

1.27 1.20 2.80 1.50 1.99 3.70

Iabs.1

0 17 67 100 100

67

0 0

[in %J

0/3 3/4 0/3

0/6

0/3

0/3

0/3 0/3

1.2 1.7 2.1 2.9 2.2

1.8

1.1 0.9

1.25 0.9 0.9 2.1 1.6

1.8

0.3 0.0

“Positive” responder = animals with score >2 mean values (24/48/72 hours) erythema oedema erythema oedema

1.30 0.80

PD I1

Table 3. Alkyl polyglycosides (C8/,0-, CI2/14APG) tested on dermal irritation in rabbits

no no yes, R38 yes, R38 yes, R38

yes, R38

no no

[I21 [I31 1141 [151 [I61

H11

[91 I101

classification Reference as “irritating”

-4

m

-

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Walter Aulmann and Walter Sterzel

irreversible changes to the eyes following the application of the test substance to the anterior surface of the eye. Taking the aspect of animal welfare into consideration, a step-by-step test strategy was launched. Accordingly, results of in vitro screening tests were used to obtain initial data on the potential effects on the eyes.

3.1 In vitro studies

- Hens’ egg tests with chorionallantois membrane (CAM test) The C A M test [191 is suitable as a screening method for in vitro eye irritation. The test substance is applied to the chorionallantois membrane ( C A M )of hens’ eggs. If haemorrhaging, lysis or coagulation on the membrane occurs within 5 minutes, the substance is regarded as having a potential irritant effect. Ethersulfate, which is a well known eye irritant, is used as a positive control. A C,,,,, alkyl polyglycoside was tested in its commercial concentration (50Yo active substance)both at pH 11.5 and at pH 7. Hens’ eggs had been fertilized for 9 days beforehand. Only slight reactions could be observed in the vascular system of the chorionallantois membrane, indicating a limited irritating potential. At pH 11.5, the alkyl polyglycoside produced only 55 940 of the effects of the ethersulfate. Neutralization to pH 7 reduced this rate to as low as 19% [20,211. - Red blood cell test

In addition to the CAM test, the red blood cell test may be regarded as a sensitive criterion for the local tolerance of a substance. The haemolytic activity of a material can be investigated in vitro in human erythrocytes. The substancespecific damage to the membrane of erythrocytes and/or oxidation of haemoglobin to methaemoglobin is determined. An erythrocyte suspension is incubated with the test substance under standardized conditions. To quantify membrane damage, the extinction of the released haemoglobin is directly determined by photometry at 525 or 540 nm. The H,, value is used to quantify haemolytic activity, being defined as the concentration which induces 50 oh haemolysis under defined test conditions. Total or 100% haemolysis is the quantitative lysis of erythrocytes in distilled water. A C,,,,, alkyl polyglycoside was subjected to the red blood cell test. A steep concentration-response relationship was observed: a concentration of 80 pg/g did not induce any haemolysis whereas a concentration of only 120 pg/g produced total haemolysis. The H,, value was found to be 104 pg/g. Accordingly, It may be concluded that C,,,,, alkyl polyglycoside has moderate haemolytic activity [221.

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3.2 In vivo irritation of rabbits’ eyes

The investigations were conducted in accordance with OECD Guideline No. 405 under which the substance to be tested is applied to one eye of each of at least three rabbits. The untreated eye of each animal serves as control. An aliquot of a 0.1 ml aqueous solution of the sample was instilled once into the eyes of 4 rabbits for an intended contact time of 24 hours. The eyes were assessed by awarding scores at certain intervals after application under the Draize scheme. The 24/48/72 hour mean scores were determined for the cornea, for conjunctiva and for the iris. All responses were checked for reversibility for 21 days. In addition, in-depth investigations were carried out after the eyes had been coloured with fluorescein. The results are given in Table 4. Just as in the skin irritation tests, a difference was again observed between the two alkyl polyglycoside types which are mainly distinguished by chain length and degree of polymerization. The short-chain alkyl polyglycoside proved to be more compatible 1231 than the C,, alkyl polyglycoside [241. C, alkyl polyglycoside does not have to be classified as a hazard or labelled as such whereas C,,,,, alkyl polyglycosides fall within theR 30 (“irritatingto the eyes”) category of the EU risk classification. 4. Skin sensitization

Skin sensitization (allergic contact dermatitis) is an immunologically mediated cutaneous reaction to a substance. In human beings, the responses may be characterized by pruritus, erythema, oedema, papules, vesicles, bullae or a combination thereof. In other species, the reactions may differ and only erythema and oedema may be observed. Guinea pigs are generally used as the test animals. The international standard test method is OECD Guideline No. 400 (corresponding to EU Guideline No. BG) which also lists the test protocols generally accepted by the relevant authorities. In the first phase of the test, the induction phase, the skin of the test animals is treated with a mildly irritating concentration of the test substance. After a certain time interval, the animals are chalTable 4. Alkyl polyglycosides Chain length c8/10 c12/14

(C8/10-,

CI2/,4APG) tested on eye irritation in rabbits

Concentration Mean values (24/48/72 hours1 [% AS1 Cornea Iris Conjunctiva (erythema)

Classification as “irritating”

Reference

0.6 0.7

2.4

no

2.5

yes, R36

[231 P41

70 50

1.8 1.25

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lenged with the maximum non-irritating concentration. Signs of potential hyperreactivity are evaluated 24 and 48 hours after the end of the challenge. Tests were carried out either by the Magnusson/Kligman method or by the Buehler method to investigate the sensitizing potential of a C,,,l, alkyl polyglycoside in female guinea pigs of the Pirbright White strain. The only difference between the two methods lies in the mode of induction. Thus, the Magnusson/Kligman method, in the initial induction phase, uses an intracutaneous injection and stimulates the immune system by addition of oil coated bacteria whereas the Buehler method uses a 6 hour closed epicutaneous patch for induction. 24 and 48 hours after removal of the challenge patch, dermal reactions are assessed by scoring. The test conditions and results are summarized in Table 5. None of the tests produced responses which could be attributed to an allergic reaction [25-281. On the evidence of these tests, alkyl polyglycoside does not require classification or labelling. This was confirmed by a human repeated insult patch test in which alkyl polyglycoside did not induce any sensitization in volunteers (see Chapter 10). Thus, the animal model provided clear predictions of effects on human beings. Aldehydes as by-products were assumed to be critical parameters for sensitizing properties. Thus, a test was conducted with a sample artificially produced under “worst case scenario” conditions, resulting in an aldehyde content of 51 ppm. This content exceeds the aldehyde content of 50 ppm specified for commercial C,,,,, alkyl polyglycoside. After three epicutaneous applications of a 12SYo solution and a 9 % challenge, no distinct dermal effects were visible by comparison with the control [281 and with the “bestcase”product [271. It could be demonstrated that the 50 ppm specification for the commercial product safely ensures that alkyl polyglycoside is free from any sensitizing effects. Table 5. Alkyl polyglycosides (C8/10-,CI2ll4APG)tested on skin sensitization in guinea Pigs Method

Concentrations [% AS]for Inductions

Magnusson-

Intracutaneous:1%

Kligrnan

Topical: 60%

Intracutaneous:0.1% Topical: 10% Buehler

Topical: 20% Topical: 12.5%

Challenge

Number of

positive responders

Classification Reference as “sensitizing to the skin”

1.0%

0/20

no

[251

1.25 2.5

0/20 0/20

no

P61

0/20 0/20

no no

I271 [281

20% 9%

Toxicology of Alkyl Polyglycosides

161

5. Mutagenicity Genetic toxicology evolved in response to concerns that chemicals known to induce mutations in various experimental systems may conceivably affect the incidence of hereditary disease in human beings. Subsequently,it was confirmed that many carcinogenic chemicals have mutagenic activity and are therefore used to investigate chemical substances both for mutagenic effects and for possible carcinogenic properties. Mutagenicity may lead to changes in the hereditary material of an organism involving changes in the genes or chromosomes. 5.1 Gene mutations

Gene mutations can be investigated by the Salmonella typhimurium reversion (“Ames”)test. The international standard test method is OECD Guideline No. 471. This microbial assay is based on reverse mutations of Salmonella typhimurium from auxotrophism (histidine-dependent) to prototrophism (nonhistidine-dependent). When mutated Salmonella typhimurium is exposed to a mutagen, mutation to the non-histidine-dependent form takes place in a proportion of the bacterial population. This proportion can readily be detected from its ability to grow on histidine-deficient medium. Since many compounds do not develop their mutagenic activity until they have been metabolized by enzyme systems not available in the bacterial cell, the test substance and the bacteria were incubated both in the absence and in the presence of a cofactor-supplemented post-mitochondria1 fraction prepared from the livers of male rats treated with the enzyme-inducing agent Aroclor 1254 6 - 9 mix). 4-Nitro-o-phenylenediamine, 9-aminoacridine and sodium azide were used as positive controls for the test preparations without the S-9 mix. 2Aminoanthracene was used for the test preparations activated with the S-9 mix. The alkyl polyglycoside assay was conducted with the Salmonella typhimurium strains TA 98, TA 100,TA 1535,TA 1537 and TA 1538 in two independent experiments both with and without metabolic activation by the S-9 mix. The test doses were 8,40,200, 1000 and 5000 g/plate in the first test and 1.25, 5, 20, 80 and 240 g/plate in the second test. Bacteriotoxic effects were observed in the range from 200 to 5000 glplate. Alkyl polyglycoside did not induce reverse mutations in the tested strains of Salmonella typhimurium either with or without metabolic activation. Accordingly, alkyl polyglycoside is regarded as non-mutagenic in this in vitro bacterial mutagenicity test [291. In order to simulate worst case scenario conditions during the production of alkyl polyglycosides, samples with an elevated aldehyde level and with normal aldehyde levels were tested for their mutagenic potency (see also 4. in this

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chapter). None of the tested materials showed mutagenic activity in this bacterial test system [30,311. 5.2 Chromosomal mutations

Chromosome mutations can be detected by the in vitro cytogenetic test in Chinese hamster V79 lung fibroblasts. The international standard test method is OECD Guideline No. 473.This in vitro mammalian cytogenetic test indicates the damage to chromosomes by structural aberrations or may provide an indication of the induction of numerical aberrations by chemical substances. Structural aberrations are changes in the chromosome structure visible in the metaphase stage of cell division (mitosis). Structural aberrations are induced by mutagenic agents through damage to the DNA and are expressed either directly or after defective repair or misreplication in the next mitosis. Numerical aberrations are induced during mitosis and are expressed in the next cell division. Accordingly, they cannot be detected in the first mitosis after treatment with the test substance. Cells undergoing mitosis are arrested with colcemide at the metaphase stage and are prepared for evaluation of chromosomal aberrations by optical microscopy. Structural aberrations different from the modal karyotype occur to a very limited extent in cells of untreated cell cultures. The test is based on a significant increase in the number of aberrations in cells treated with test substance by comparison with cells in control cultures. Normally, the induction of numerical aberrations (aneuploidy, polyploidy, genome mutations) cannot be evaluated. Nevertheless, indications of the induction of genome mutations are recorded and reported. To evaluate the test, reference mutagens were tested alongside the test substance under the same conditions. In the experiment, ethylmethanesulfonate was used without the S-9mix and cyclophosphamide with the S-9 mix to control the activation conditions. In the cytogenetic experiment with alkyl polyglycoside, chromosomes were prepared 7,20and 28 hours after the beginning of the treatment with the test substance. The treatment interval was 4 hours with and without metabolic activation. All cultures were run in duplicate. In an experiment on plating efficiency, strong toxic effects were recorded at 5 g/ml and higher without metabolic activation and above 100 g/ml with the S-9mix. Alkyl polyglycoside was applied to the V 79 cell cultures in concentrations of up to 16 g/ml without and up to 160 g/ml with metabolic activation. No biological activity in the induction of chromosomal aberrations was observed after application of alkyl polyglycoside either with or without the S-9 mix. There was no significant increase in chromosomal aberrations after the treatment by comparison with the current and historical control values. In

Toxicology of Alkyl Polyglycosides

163

addition, there was no indication of any increase in the frequency of polyploid metaphases after the treatment with the test substance. Accordingly, alkyl polyglycoside is considered to be non-mutagenic in this chromosome aberration test t321. 6. Toxicokinetics and metabolism

Toxicokinetics is the study of the rates of absorption, distribution, metabolism and excretion of substances. Metabolism describes all the processes by which a particular substance is handled in the human body. Data from toxicokinetic studies are desirable for the evaluation of test results from other toxicological studies and for the extrapolation of data from animals to human beings. Literature studies are available on the behaviour of several alkyl-8-glycosides in the mammalian organism. Octyl-~-D-[U-14C1-glucoside, [l-'dC1-dodecyl-~D-maltoside and [l- 14C1-hexadecyl-~-D-glucoside were used as test substances representative of alkyl polyglycosides 1331. After oral application to NMRI mice, the metabolism and organ distribution were determined by radiometry. Two hours after gavage, the animals were sacrificed and radioactivity was determined in sections of various organs. The highest levels were found in the stomach, intestine, liver and kidneys. The high level in urine indicated rapid degradation and elimination of the substance tested. Hydrolysis occurred rapidly in the stomach and intestine and in the mucosa. The hydrolysis products, the sugars and the fatty alcohols were either further metabolized or partly used for specific de novo syntheses of products occurring under physiological conditions in the mammalian organism, for example fatty acids, wax esters etc. The substances under investigation were readily degraded in the mammalian body. In no stage of the metabolic process were any toxic intermediates formed. The toxicokinetic studies also demonstrated that alkyl polyglycosides are physiologically compatible. 7. Subchronic toxicity

While acute toxicity is concerned with the adverse effects of single doses, a more common form of human exposure to chemical substances are repeated doses which do not produce immediate toxic effects. Delayed effects may occur through accumulation of the chemical substance in tissues so that it is important to identify any potential for these delayed effects by subchronic testing. Subchronic testing provides information on possible health hazards, for example to target organs, arising from repeated exposure over a limited period of time and

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is a useful tool for estimating a no-effect exposure level or a no-adverse-effect exposure level which can be helpful in establishing safety criteria for human exposure. Subchronic toxicity is the adverse effect produced by the repeated daily administration of a chemical substance to experimental animals for part (not more than 100/0) of their lifespan. The international standard test method for oral application is OECD Guideline No. 408. The test substance was orally administered in graduated daily doses to severalgroups of experimental animals at a rate of one dose per group (consisting of 10 male and 10 female animals) over a period of 90 days. Over that period, the animals were subjected to routine clinical observations. In addition, their body weight and food and water consumption were recorded to enable signs of toxicity to be detected. Haematological, clinicochemical and ophthalmoscopic investigations were performed during week 7 and 13. At the end of the treatment period, all the animals were subjected to general pathological examination and organ weight analyses. A wide range of tissues was fixed and examined by microscope. A subchronic toxicity study was carried out with a C ,,, alkyl polyglycoside in male and female Wistar rats. After repeated oral doses of 0, 250, 500 and 1000 mg/kg body weight (groups 1 to 41, the compatibility of the test substance was investigated. In addition to groups 1and 4, 5 male and 5 female animals were used to determine the reversibility of possible unfavourable substancerelated findings. There were two fatalities,neither of which was linked to the test material. In clinical studies, no effects were observed on food consumption or on haematological and clinicochemical parameters. Statistically significant differences in relation to the control were found in isolated parameters, such as weight gain, increased number of thrombocytes, etc., but were not dose-related and, accordingly, were considered to be due to normal animal variation. General pathological examination revealed ulcers and oedema confined to the forestomach of the 1000 mg/kg group. Histological tissue examination revealed slowly reversible, dose-related irritation and ulceration of the mucous membrane of the forestomach of the animals of the 1000 mg/kg group. The animals of the 250 mg/kg group did not show any lesions attributable to the treatment with alkyl polyglycoside. According to the described results, a daily dose of 1000 mg/kg did not lead to any cumulatively toxic effects. This dose is thus classified as a “no-observedadverse-effect-level” (NOAEL).The observed histological changes-local irritations of the mucous membrane of the forestomach-have to be interpreted as symptoms of a local adverse effect rather than a systemic effect. Thus, a noobserved-adverse effect-concentration(NOAEC)of 2.5 O/o may be estimated for local compatibility D41.

Toxicology of Alkyl l’olyglycosides

165

8. Conclusions

The object of toxicological studies is to assess the hazard potential of chemical products in order-on the basis of these findings-to asses the risks to the health of the user and to prevent possible adverse effects, even after improper use. The biological endpoints which have to be considered in toxicological studies follow the state of science and, for the most part, are included in current legal regulations (EC Directive 93/35/EEC). It should be noted that the main concern of these studies is to determine the toxic potential of a substance (hazard). This often involves conditions which considerably exceed normal exposure levels. Toxicological studies thus provide information on the inherent toxicological potential of chemical substances. An assessment of the actual risks is only possible if the corresponding exposure conditions, i. e. mode of application, duration and frequency of contact, are included in these considerations. If these principles are disregarded by arbitrarily equating hazard with risk, wrong conclusions will inevitably be drawn. The toxicological safety strategy for chemical products should be based on the following objectives: - Correct handling should rule out unwanted side effects - Foreseeable improper use should not cause serious health damage - Even long-term exposure via environmental pathways should not involve any health risk. Alkyl polyglycosides varying in chain length and purity have been subjected to the most relevant toxicological endpoints necessary for a sound risk assessment. On the basis of the information available, alkyl polyglycosides are not considered as toxic or harmful in acute toxicity tests, but in high concentrations have to be classified as irritating to the skin and eyes. In addition, sensitizing effects are unlikely to occur. A NOAEL of 1000 mg/kg body weight can be estimated for toxicity after repeated oral application. In in vitro tests, alkyl polyglycosides did not show any potential for gene and chromosome mutations. Safety in use and handling also includes foreseeable improper use, such as the accidental swallowing of cosmetic products by children. By virtue of their low acute oral toxicity, alkyl polyglycosides do not contribute to the toxicity of cosmetic and other household products. The acute oral toxicity values (LD,,) are of the order of several grams per kilogram body weight. In other words, it is virtually impossible to be seriously poisoned by these products. Several authors have provided estimates of the daily oral intake of surfactants from various sources. Drinking water (1-2 mg/day) [35,361,dental hygiene products (0.1-0.9 mg/day) [371and residues of dishwashing detergents (0.3-0.4

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Walter Aulmann and Walter Sterzel

mg/day) [38,39,401 are among the sources mentioned. On the basis of these estimates, the total daily intake per person is of the order of 0.3-3 mg [35,371. Assuming that the maximum daily intake per person is 3 mg, the calculated dose for a person weighmg GO kg is 0.05 mg/kg body weight. If this maximum daily intake is compared with the no-effect-level established in studies on systemic chronic toxicity, it is quite clear that these amounts may be regarded as harmless. The resulting safety factors are thus greater than 1000. In addition, considering the absence of any irreversible effects, the data presented show beyond any reasonable doubt that the safety margin is very considerable. Accordingly, there is no indication of any risk to the consumer, the workforce or the general public. References

1. Organisation for Economic Cooperation and Development-OECD (19811, Paris 2. Henkel Corp. (1987),unpublished results, Rep. No. TBD EX 0321 3. Henkel Corp. (1990), unpublished results, Rep. No. R9600989 4. Henkel KGaA (1986), unpublished results, Rep. No. TBD860297 5. Henkel Corp. (1987),unpublished results, Rep. No. TBD EX 0323 6. Henkel Corp. (1990), unpublished results, Rep. No. R9600990 7. M. Kietzmann, W. Loscher, D. Arens, P. Ma&, D. Lubach, J. Pharmacol. Toxicol. Meth. 30 (1993) 75 8. W. Pittermann, B. Jackwerth, M. Schmitt, In Vitro Toxicology (1997/1) in press 9. Henkel KGaA (19931, unpublished results, Rep. No. R9300408 10. Henkel KGaA (1993), unpublished results, Rep. No. R9300407 11. Henkel KGaA (1993),unpublished results, Rep. No. R9400 116 12. Henkel KGaA (1988),unpublished results, Rep. No. TBD880089 13. Henkel KGaA (1993), unpublished results, Rep. No. R9300115 14. Henkel KGaA (1988),unpublished results, Rep. No. TBD880405 15. Henkel KGaA (1994),unpublished results, Rep. No. R9400725 16. Henkel KGaA (1994),unpublished results, Rep. No. R9400459 17. Henkel KGaA (1993), unpublished results, Rep. No. RT930139 18. Henkel KGaA (19931, unpublished results, Rep. No. R930138 19. H. Spielmann,S . Kalweit, M. Liebsch, T. Wirnsberger, I. Gerner, E. Bertram Neis, K. Krauser, R. Kreiling, H. G. Miltenburger, W. Pape, W. Steiling, Toxicol. in vitro 7 (1993) 505 20. Henkel KGaA (1995),unpublished results, Rep. No. R9500934 21. Henkel KGaA (1993,unpublished results, Rep. No. R9501299 22. Henkel KGaA (1995), unpublished results, Rep. No. R9500783

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23. Henkel Corp. (1990), unpublished results, Rep. No. R9601003 24. Henkel Corp. (1990), unpublished results, Rep. No. R9601004 25. Henkel KGaA (1990), unpublished results, Rep. No. TBD900290 26. Henkel KGaA (19881, unpublished results, Rep. No, TBD880412 27. Henkel KGaA (1994), unpublished results, Rep. No. R9400208 28. Henkel KGaA (19931, unpublished results, Rep. No. R9300256 29. Henkel KGaA (19901, unpublished results, Rep. No. 900467 30. Henkel KGaA (1993), unpublished results, Rep. No. 9300209 31. Henkel KGaA (1994),unpublished results, Rep. No. 9300401 32. Henkel KGaA (1995), unpublished results, Rep. No. 9400243 33. N. Weber, Fette, Seifen, Anstrichmittel 86 (1984) 585 34. Henkel KGaA (1989),unpublished results, Rep. No. 890191 35. R. D. Swisher, Arch. Environ. Health 17 (1968) 232 36. J. Borneff, Arch. Hyg. Bakt. 141 (1957) 578 37. W. Sterzel in Anionic Surfactants: Biochemistry, Toxicology, Dermatology (C. Gloxhuber, K. Kunstler, eds.), Surfactant Science Series 43, Marcel Dekker: New York, Basel, Hong Kong 1992, p. 411 38. H. Wedell, Fette, Seifen, Anstrichmittel 68 (1966) 551 39. J. Schmitz, Tenside Detergents 10 (1973) 11 40. R. Kruger, Seifen, Ole, Fette, Wachse 86 (1960) 289

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

10. Dermatological Properties of Alkyl Polyglycosides Wolfgang Matthies, Bettina Jackwerth, and Hans-Udo Krachter

In recent years, the development of new washing-active raw materials has been increasingly under the influence of consumer demands for extreme mildness coupled with cleaning performance both on the body and on surfaces. Consumer expectations extend to all-round good compatibility with the skin and mucous membrane both on direct contact with the undiluted product and after repeated and, possibly, long-term application. Moreover, it is naturally assumed that such a product will not cause any allergies. With the introduction of alkyl polyglycosides, a type of molecule became available which, as a combination of sugar and fat, gave rise to expectations of modified adsorption properties on the surface of the skin, possibly reduced penetration into lower epidermal and dermal layers and hence an altogether reduced irritation potential. Today, defined test strategies [1,21 are available for characterizing biological properties. After toxicological safety screening, they provide for the direct testing of effects on the skin of volunteers and have also been applied comprehensively to alkyl polyglycosides. Thereafter, standardized tests in open or occlusive application are suitable for classifying or characterizing a test substance against known standards. Application-oriented methods are used in later studies to test formulations nearly ready for use. 1. Open application

The first stage comprises open application to the lower arm where a minimum contact time of 30 minutes should be achieved [31. Under these conditions, alkyl polyglycoside was tested in the form of a mixture with fatty alcohol ether sulfate in concentrations up to the undiluted product without any signs of irritative reactions [41. 2. Occlusive application

Far more rigorous are test conditions which provide for contact under occlusion. In the classical patch test with semiocclusive or fully occlusive chambers, the stratum corneum is hydrated according to the degree of occlusion so that the barrier function of the epidermis is critically weakened. The penetration and irritation properties of substances can thus be investigated under standardized application conditions in regard to the choice of chambers and the contact time.

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Alkyl polyglycoside in the form of a C,,,,, APG commercialproduct was patchtested in aqueous solution by comparison with known standard surfactants, such as linear alkylbenzene sulfonate (LAS),secondary alkane sulfonate (SAS), fatty alcohol sulfate (FAS),fatty alcohol ether sulfate (FAES)or-in other termssodium lauryl ether sulfate (SLES),and methylester sulfonate (MES).It showed a lower irritation potential than the standard surfactants both in regard to the parameter of erythema as an indicator of an irritative reaction and in regard to subsequent desquamation as a parameter for hydration of the stratum corneum with subsequent structural impairment. Mixtures of the standard surfactants mentioned with alkyl polyglycoside in a ratio of 1: 1 were also tested and, as expected, a reduction in the relative degree of irritation was observed where alkyl polyglycoside was used as co-surfactant [51. This relative improvement in dermal compatibility by mixing basic surfactants with alkyl polyglycosides was further investigated both for C,, APG and for C,,,,, APG, a clear correlation being found between the degree of substitution of a standard surfactant (sodium lauryl ether sulfate, SLES) with 1,2,3 or 4 parts of alkyl polyglycosides and a reduction in the irritation values [61. A typical example is shown in Figure 1. Alkyl polyglycosides with defined chain lengths of CSto CI6and c16/18were patch-tested on healthy volunteers over a contact time of 24 hours by comparison with two commercial products, C8-14APG and c~14 APG. 5 Yo and 10Yo aqueous solutions and suspensions in ethoxylated glyceryl cocoate in a ratio of 70 :30 were compared with one another. The result was that the aqueous solutions show a marked dependence on chain length with distinct maximal irritation produced by the C12 chain whereas the long chains in particular produce hardly any irritation. Alkyl polyglycoside in the form of the suspension in glyceryl cocoate showed this effect in further ROAT/antecubital fossa (erythema)

Patch test (erythema) Rel. reizscore

[%I

Rel. reizscore

100

100

80

80

60

60

40

40

20

20 1

2

3

4

5

[%I

1= SLES 2 = SLES and C 814 APG (3:l) 3 = SLES and C 814 APG (1:U 4 = SLES and C 8.14 APG (1:3)

1

2

5

5 = C8.14 APG

Figure 1. Reduction of irritative effects of a standard surfactant by substitution with C8-14 APG (Plantacare 2000) (ROAT = Repeated open application test)

DermatologicalProperties Rel. score

171

[%I

30 20

10

Alkyl chain

ClO

c8

5% in water

c12

c14

I5% in water/Glyceryl

c16

c16/18

c8-14*

c12/14'

cocoate

Figure 2. Results of patch tests with alkyl polyglycosides (DP= 1.4): influence of various alkyl chain length and the solvent (*commercial product)

weakened form (Figure 2). Accordingly, the commercial product with the higher percentage content of longer alkyl chain lengths has relatively better compatibility than the other type, both types showing equally minimized irritation potential in the form of suspensions in glyceryl cocoate 171. - Influence of the degree of polymerisation (DP) By comparison with alkyl polyglycoside types having the same chain length (CIJ but different degrees of polymerisation (1.2-1.G5), the aqueous solution also showed a clear dependence in the sense of a distinct reduction in irritation potential with increasing DP (Figure 3 ) .The reduction in the irritation level by suspension in glyceryl cocoate was demonstrated by this example also. These data show that, depending on the application intended, the type of product and Rel. score

*O 60

[%I

1

40

20 5% in water 5% in water/Glyceryl cocoate 1.65

1.3

1.2

DP

Figure 3. Influence of the degree of polymerisation on the irritation potential of a C U alkyl polyglycoside

Wolfgang Matthies, BettinaJackwerth, and Hans-Udo Krachter

172

the required performance pf the product, compatibilitycan be further optimized by choosing between various types of alkyl polyglycosides and also by careful choice of the solvent system.

3. Application tests The question of how far properties observed in standardized irritation models can be recreated under more practical conditions is of particular importance to the characterizationof a cosmetic substance. Simulated application tests are used for this purpose, the new substance being used in starting formulations which correspond in composition and concentration to its subsequent use in end products. The application conditions closely approximate the subsequent intended use of the product. Since alkyl polyglycosides are suitable for use as a surfactant or co-surfactant for many types of product (for example manual dishwashing detergents, cleaners, shampoos, shower baths, foam bath formulations, deodorants, face cleansers, etc., see Chapters 5 and 61,both compounds and end products were investigated in various simulated application situations and in use tests with actual product formulations. The commercial C I ~c8-14 , (Plantacare 2000) and Cl2Il4(Plantacare 1200) APG were normally used (see Chapter 2, Table 1). - Arm flex test In the arm flex test, the influence of alkyl polyglycoside as a co-surfactant with sodium lauryl ether sulfate (2 EO) was tested against sodium lauryl ether sulfate (2 EO) (SLES)alone in a series of tests on healthy volunteers (Figure 4). Not only was a reduction in the visible development of erythema and in the drying of the skin (desquamation)after treatment with SLES alone observed, it Erythema

Scaling

Rel. irrit. score [%]

Rel. irrit. score

100

100

100

80

80

80

2 = SLES

60

60

3 = C8.14 APG

40

40

60 40

20

20

20

1

2

3

Sensoric parameters

[%I

Rel. irrit. score

[%I 1 = SLES and c8.14 APG (3:l)

1

2

3

Figure 4. Arm flex test: influence of sensory parameters

1

2

3

APG and SLES on erythema, scaling and

173

DermatologicalProperties Rel. transepidermal water loss

100 80

[%I

1 = SLES 2 = SLES and C8.14 APG (3:1) 3 = C8.14 APG

60 40

20 1

2

3

Figure 5. Arm flex test: influence of APG and SLES on the transepidermal water loss

was also found that various objective measurement parameters were positively influenced. Thus, the washing-initiated barrier damage by sodium lauryl ether sulfate (measurement of the TEWL with an Evaporimeter", Figure 5 ) and the surface roughness of the skin (as measured by profilometry) were reduced and the optical image of the surface (visible under an optical microscope, Figure 6 )

Treated

Untreated

SLES

SLES + APG (3: 1)

Figure 6. Arm flex test: influence of C8-14APG and sodium lauryl ether sulfate6LES) on the skin roughness (duration 14 d, inspection by flexible microscope, magnification SOX)

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Wolfgang Matthies, Bettina Jackwerth, and Hans-Udo Krachter

favourablyinfluenced by the alkyl polyglycoside substituted formulation. Similarly, subjective sensations felt by the volunteers, such as burning and itching, were also reduced by around 60% [81. Similar results were produced by investigations with various surfactant mixtures in which sodium lauryl ether sulfate with C ~ 1 4APG, Cs110 APG and a mixture of sodium lauryl sulfate with C12114 APG were tested against sodium lauryl ether sulfate alone. In this case, too, a significant reduction in barrier damage by the pure alkyl polyglycoside products of 65 to 75% was obtained after the treatment in the arm flex test [61. - Hand immersion test The hand immersion test was preferably used as a form of application for manual dishwashing detergents. In this case, too, alkyl polyglycoside containing formulations could be shown to have advantages over differently formulated market products, more particularly less influence on the barrier function and fewer drying out effects [91. A more detailed account can be found in Chapter 6. - pH value of the skin Besides the above-mentioned parameters of influencing the barrier function, surface structure, influencing penetration and the associated irritation potential, another parameter for the biological effect of a surfactant is its influence on the pH value of the skin. This may be interpreted as an expression of the change in the bacterial environment and is typically characterized by a shift towards the alkaline range after treatment with soaps or solely through frequent contact with moisture. To maintain a physiological situation, there should be relatively little change in pH or only the briefest disturbance to the equilibrium [lo]. Accordingly, alkyl polyglycoside containing shower bath formulations were tested against sodium lauryl sulfate in a concentration of 10To in washing tests in which the starting pH value of the skin was observed immediately before and after washing. Whereas sodium lauryl sulfate produced a distinct shift towards the alkaline range for a regeneration time of more than 5 hours, washing with the alkyl polyglycoside containing shower bath led to only a slight shift in the pH value and to restoration of the starting value in 2 to 3 hours [ 111 (Figure 7). 4. Use test

The ultimate parameter for the successful acceptance of a new product is the satisfaction of the user. Various alkyl polyglycoside containing products were tested under use test conditions. Acceptance in regard to compatibility with the skin and mucous membrane was generally very high. For example, for such products as a deodorant, cleansing milk or a cleansing lotion marketed as an alkyl polyglycoside microemulsion, extremely high satisfaction rates in regard

175

Dermatological Properties

6.5 -

Mean of all volunteers

65.5 54.5 -

-1

0

1

2

3 4 5 Hours after treatment lhl

Figure 7. Influence of C8-14APG (Plantacare 2000) and sodium lauryl sulfate (SLS) on the pH value of the skin

to dermal compatibility and general acceptance were achieved in use tests over 4 weeks involving the target group of users [12,131. 5. Market observation in regard to unwanted effects

Observations from marketing experience in regard to health-relevant claims over recent years show that, hitherto, alkyl polyglycosides have never been found to exhibit any irritating or sensitizing properties. From the epidemiological point of view and from experience gained in the meantime from several hundred applications to healthy volunteers, there has never been any suggestion of sensitizing potential in alkyl polyglycosides. 6. Overall dermatological picture Dermatologically, alkyl polyglycosides represent a new class of very mild surfactants which, depending on the type of product, are eminently suitable for use as sole surfactant or co-surfactant in the formulation of particularly gentle products. Optimized dermatological compatibility for many cleaning products can be achieved through careful choice of the chain length, the degree of polymerization, the vehicle or solvent and the particular formulation. On the basis of experience acquired thus far, alkyl polyglycosides are substances characterized by high dermatological safety and acceptance.

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References

1. W. Matthies, Parfiimerie und Kosmetik 73 (1992) 80 2. COLIPA; Cosmetic Product Test Guidelines for the Assessment of Human Skin Compatibility, Brussels, 1995 3. W. Matthies, Seifen, Ole, Fette, Wachse Journal 119 (1993) 992 4. Henkel Internal Test Report, RD 930078 5. Henkel Internal Test Report, RD 930004 6. B. Jackwerth, Skin Care Forum 12 (1995) 4 7. W. Matthies, H.-U. Krachter,W. Steiling, M. Weuthen, 18th IFSCC, Venice, 1994, Poster Vol. 4, 1994, p. 317 8. B. Jackwerth, H.-U. Krachter, W. Matthies, Parfiimerie und Kosmetik 74 (1993) 142 9. Henkel Internal Test Report, RD 920087 10. H.-C. Korting, M.-H. Schmid, Skin Care Forum 14 (1996) 7 11. Henkel Internal Test Report, RD 920127 12. Henkel Internal Test Report, R 9501237 13. Henkel Internal Test Report, R 9500746

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

11. Ecological Evaluation of Alkyl Polyglycosides Josef Steber, Walter Guhl, Norbert Stelter, and Frank Roland Schroder

Alkyl polyglycosides are mostly used in dishwashing and laundry detergents, cosmetics and cleaning products (see Chapters 5 and 6 )which are discharged into domestic wastewater after use and thus enter the aquatic environment. The environmental fate and effects of a chemical substance are the key criteria for any ecological safety assessment. Generally, the environmental fate of surfactants is inextricably linked with their biodegradation behaviour because biodegradation is the foremost mechanism for the ultimate elimination of chemical substances from aquatic and terrestrial environments. Thus, quick and complete biodegradability is the most important requirement for an environmentally compatible surfactant. The environmental impact of chemicals lies mainly in their ecotoxicity which is relatively high in the case of surfactants because of their surface activity and the resulting effects on biological membranes. According to broadly accepted risk assessment schemes for chemical substances 111, environmental compatibility requires proof that the use of the chemical will not result in environmental concentration levels higher than the ecotoxicological no-effect concentration. The study of the ecological evaluation of alkyl polyglycosides as presented herein provides the data and the conclusions which will form the basis for sound assessment of the environmental compatibility of this interesting class of surfactants. 1. Biodegradation data

The biodegradation tests with alkyl polyglycosides were carried out by internationally used and accepted standard methods (Figure l). The group of discontinuous tests is relatively simple in terms of design, but has a high stringency which, in the case of positive results, allows general conclusions to be drawn as to biodegradability in aquatic and terrestrial environments 121. The group of continuous activated sludge tests mainly comprises those tests which simulate the biodegradation process in a municipal sewage treatment plant. 1.1 Aerobic ready biodegradability

The biodegradability assessment of chemicals normally starts with screening tests. Although alkyl polyglycosides are nonionic surfactants, the routine analytical procedure used to follow the (primary) degradation of nonionic surfac-

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Josef Steber,Walter Guhl, Norbert Stelter, and Frank Roland Schroder

Screening tests Characteristics

Sewage treatment plant simul. tests Inflow Outflow

Single addition of test substance Test substance is C source 0 Duration of test up to 4 weeks 0 Stringent assessment 0

Continuous dosage of test substance and synthetic wastewater 0 Retention time: 3-6 hours 0 Evaluation close to reality 0

Examples: b Primary degradation (relevant for detergent legislation: anionic and nonionic surfactants) OECD Screening Test: demand 280%(MBAS. BIAS)

OECD Confirmatory Test: demand 280%(MBAS, BIAS)

b Ultimate degradation (relevant for chemicals law, EU classification “dangerous for the environment“) ~~~~

~

OECD tests for ready biodegradability: for example 0

Closed Bottle Test: 260 % 0, consumption*

0

Modified OECD Screening Test: 260 % carbon removal*

0

COz Evolution Test: 2 60 % C02 formation*

Coupled Units Test: measurement of DOC removal

[%I

‘Pass value for “ready biodegradability”

Figure 1. Standard procedures for determining the biodegradability of substances

tants, namely measurement of BAS removal 131, cannot be applied because alkyl polyglycosides do not react as bismuth-active substance (BiAS). Thus, legal biodegradability requirements in Europe for nonionics (280 010 BiAS removal) do not apply to this group of surfactants. However, the OECD ready biodegradabilitytests (OECD 301 series)[21represent a group of broadly applicable screeningtests which form the basis for the biodegradabilityevaluation of most chemicals. These tests determine t h e ultimate biodegradation of the test compound, i. e. the microbial transformation of the parent test substance into

179

Ecological Evaluation of Alkyl Polyglycosides

the final products of the degradation process, such as carbon dioxide, water and assimilated bacterial biomass. These discontinuous tests are characterized by their stringency which is attributable to the relatively high test compound/ inoculum ratio and to the test compound being the sole carbon source. CnIl4 alkyl polyglycoside (CI2ll4APG) was tested in three different ready biodegradability tests, the Closed Bottle Test (OECD 301 D), the Modified OECD Screening Test (OECD 301 E) and the DOC Die-Away Test (OECD 301 A).The results obtained (Table 1)reflect a very high degree of ultimate biodegradation over the Table 1. Biodegradation test data of C12/14and C S APG ~ Test method

Test results APG APG C

C

Analytical parameter

Remarks/ conclusions

804, /COD

10-d-time window fulfilled: “Readily biodegradable” according to OECD classification

b Ultimate degradation screening test: Closed Bottle Test (OECD 301 D)

73-88 %

81-82 %

Modified OECD Screening Test (OECD 301 E)

90-93 % 56-82 %

9 4% 88 %

DOC * TOC

DOC Die-Away Test (OECD 301 A)

95-96 % 66-81%

-

DOC * TOC

-

b Continuous activated sludge tests: OECD Confirmatory Test

>99.5 %

-

Removal of parent compound

Primary biodegradation

Coupled Units Test (OECD 303 A)

89*2 %

-

DOC removal

Ultimate biodegradation

101.8+2.0%

-

DOC removal

Residue-free ultimate degra dation

CO, + CH, production

Ultimate anaerobic biodegradation

Metabolite test

b Anaerobic biodegradability: ECETOC screening test removal (28 d)

84*15%

95+22%

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Josef Steber,Walter Guhl, Norbert Stelter,and Frank Roland Schroder

28-day test period in all tests. The Closed Bottle Test, which is the most exacting of all OECD 301 tests [41, reached mineralization levels of 88 940 (test concentration 2 mg/U and 72 Yo (5 mg/l), thus far exceeding the OECD limit for ready biodegradabilityevaluation (60O!o BOD/COD). The 10-daytime window” was also easily fulfilled (Figure2); this requires that the 60 Yo level is reached within 10 days of significant commencement (10940 degradation) of the degradation process. The other two ultimate biodegradabilityscreening tests conducted with C ~ 1 4 APG are based on measurement of the DOC removal. Due to the low degree of inoculation, the Modified OECD Screening Test (MOST) is also considered to be one of the most stringent ready biodegradability tests 141. Nevertheless, the final 28-day result of the MOST was very similar to the outcome of the DOC Die-Away Test, i. e. 90 940 DOC removal, which exceeds by far the 700/0pass level required for “ready biodegradability”.In addition, the degradation kinetics of the two tests clearly show that the 10-day time window requirement was easily satisfied (Figure2). In order to ensure that these high DOC removals are not overly influenced by physical elimination processes,TOC removal was also analyzed. This parameter enables the contribution of mineralization to the biodegradation level to be evaluated. The data given in Table 1 show that the high DOC removal is mainly due to the mineralization of alkyl polyglycosides, underlining once again the ready ultimate biodegradability of this surfactant. The same positive evaluation was obtained for the short-chain C8l10 alkyl polyglycoside (C8ll0APG) in the Closed Bottle Test and in the Modified OECD Screening Test (Table 1). To sum up, the results of various OECD ready biodegradability tests show unequivocally that alkyl polyglycosides are readily biodegradable and, according to the conclusions of the OECD [21,will undergo rapid and ultimate biodegradation in the environment.

OECD 301 D, BOD/COD

[%I

OECD 301 E, DOC-removal [%I OECD 301 A, DOC-removal [%I

Figure 2. Ultimate biodegradation kinetics of C W IAPG ~ in OECD ready biodegradability tests

Ecological Evaluation of Alkyl Polyglycosides

181

1.2 Biodegradation in sewage treatment plant simulation tests

Wastewaters containing inter alia the ingredients of spent detergents and cleaning products are usually purified in a sewage treatment plant before they enter receiving waters. Thus, the biodegradation behaviour of a chemical substance in sewage treatment plants determines the concentration of that substance in surface waters, river sediments, sludges, etc. The removal of C12,14APG under sewage treatment plant conditions was investigated in two model tests. The OECD Confirmatory Test t31, which simulates the biological stage of a wastewater treatment facility, enabled the removal of the parent compound (primary biodegradation) to be evaluated while the Coupled Units Test (OECD 301 A, [21) determined the removal of alkyl polyglycosides on the basis of ultimate biodegradation analysis parameters. In both tests, the hydraulic retention time was 3 hours which is considerably shorter than in modern sewage treatment plants. To measure primary biodegradation, a substance-specific analytical determination technique was developed on the basis of high performance liquid chromatography (HPLC) 151. Even during the working-in period of the model plant of one week, the elimination of alkyl polyglycosides exceeded 98 o/o. During the 3-week evaluation phase, no genuine alkyl polyglycoside could be detected in the effluent after the continuous addition of alkyl polyglycoside in concentrations of 20 mg C/1 and 10 mg C/1. Taking the alkyl polyglycoside concentrations determined in the model plant influent into account, the elimination rate was 99.5-99.8O/o (Table 1).At the same time, the degradation of the so-called synthetic wastewater-the main organic substrate continuously added to the model plant-amounted to 9496 O/o DOC removal. This shows impressively that alkyl polyglycosides have no adverse effect on the degrading organisms of the treatment plant, even at high concentrations. The outcome of studying CI2ll4APG in the Coupled Units Test (Table 1) confirms and specifies the conclusions to be drawn from the OECD Confirmatory Test data. Under comparable simulation conditions, i. e. with a 3-hour hydraulic retention time and in the presence of an excess of a readily biodegradable substrate (“synthetic wastewater”), the surfactant produced an 89 f2 010 DOC removal over the 39-day test period. This result confirms that the high primary degradation of alkyl polyglycosides promote substantial ultimate biodegradation under realistic sewage treatment plant conditions. The investigations into the biodegradation behaviour of alkyl polyglycosides in model wastewater treatment plants thus demonstrate the excellent primary and ultimate biodegradation of this surfactant which leads to extremely low concentrations of the parent surfactant and degradation intermediates in the plant effluent.

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1.3 Test for detecting recalcitrant metabolites

Although “readily biodegradable”substances are considered to undergo rapid ultimate biodegradation [21, there is still some uncertainty as to the completeness of the ultimate degradation process. Screening tests do not provide such exact results as to rule out definitively the formation of even small amounts of recalcitrant residual materials originating from the parent compound or its degradation intermediates. For evaluation purposes, even the slightest possibility of the formation of recalcitrant metabolites from alkyl polyglycosides is sufficient justification for the surfactant to be investigated by the “Test for Detecting Recalcitrant Metabolites”(metabolitetest) [61. In this modification of the Coupled Units Test (Figure31, the ultimate biodegradation potential of a test compound under practical conditions is evaluated by recycling the plant effluent daily to the continuous activated sludge unit and replenishing it with a concentrate of nutrients (“synthetic sewage”) and the test compound. C12~14 AF’G reached a DOC removal of 101.8f2.00/0in the metabolite test. This result rules out the possibility of any recalcitrant metabolite being formed during the biological degradation of the alkyl polyglycoside structure. The biodegradability assessment based on the screening and simulation test results has thus been confirmed and extended: alkyl polyglycosides were found to be residue-free and ultimately biodegradable under realistic environmental conditions. On the basis of the excellent comparability of the ultimate biodegradability screening test data for C12/14and C8/10APG (Table l),it is clear that these conclusions are also applicable to the shorter-chain homologue. 1.4 Anaerobic biodegradation

The issue of the complete biodegradability of chemical substances in the environment must also include their fate in anaerobic environmental compartments. Although aerobic biodegradation processes, i. e. in the presence of oxygen, are certainly most important for the ultimate removal of chemical substances, highly adsorbing compounds such as surfactants will still reach anaerobic parts of the environment in large measure. For example, in digesters of sewage treatment plants, household septic tanks, sediments of polluted rivers and flooded soils, the microbial degradation of a compound can only proceed if its chemical structure is accessible to anaerobic degradation. Thus, it is widely accepted that the anaerobic biodegradation behaviour of surfactants is relevant to assessments of their environmental compatibility [71. The ultimate anaerobic biodegradability of alkyl polyglycosides was tested by the recently developed ECETOC screening test [81 which quantifies the degree of degradation by measurement of the gaseous end products, methane

183

EcologicalEvaluation of Alkyl Polyglycosides Problem

Formation of poorly degradable intermediates?

Degradation also under anaerobic conditions?

Metabolite test

Test method

ECETOC test

Charac-

teristics

0

Continuous test with recycling of the effluent and new dosage of substance

0

Duration of test: up to 3 months

Measurement parameters

Evaluation

0

Static test with sludge

0

Duration of test : 4-8 weeks

C concentration in influent and effluent of test and control plant is measured. C removal [%I is investigated for significant difference 0

(theoretical) formation of an intermediate with more than 1 C atom must be excluded (basis of calculation: amount of C atoms of test substance)

Measurement of formation of digester gas [% of organic C of test substance]: - Measurement of pressure 0

230%:Indication of anaerobic (primary) degradation 260%:Good anaerobic ultimate biodegradation

Figure 3.Additional biodegradation issues: how complete is degradation?

and carbon dioxide (Figure 3).Under the rigorous conditions of this screening test, 84 f 15% of Cl2Il4AF'G was degraded over the 8-week test period. The short-chain C8jl0AF'G also produced a favourable degradation result of 95 k 22 010 after a 56-day incubation period (Table 1). These results reflect the excellent biodegradability of alkyl polyglycosides, even in the absence of oxygen. On the basis of the predictive value of this screening test result for the real environmental situation, it may be concluded that alkyl polyglycosides will undergo ultimate biodegradation in municipal and household digesters, so that significant contamination of river sediments and soils (where sewage sludges are used as agricultural fertilizers) by alkyl polyglycosides is unlikely. Accordingly, alkyl polyglycosides can join the ranks of surfactants with optimal biodegradation properties in that they are ultimately biodegradable under all environmental conditions.

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2. Ecotoxicological data

The ecotoxicological evaluation of alkyl polyglycosides is also based on standard tests [9,10,111 covering the acute, subchronic and chronic toxicity of alkyl polyglycosides towards living organisms of the aquatic and terrestrial environments. The results of these investigations are summarized in Table 2. 2.1 Acute aquatic toxicity

The acute aquatic toxicity data of CI2ll4APG are typical of surfactants used in detergents [121. Nevertheless, the fish toxicity LC50 of 3.0 mg/l, the daphnia toxicity EC50 of 7.0 mg/l and the algal EC50 of 6.0 mg/l reveal a favourable acute ecotoxicity profile among the group of surfactants with this alkyl chain length. A structure/toxicity relationship is revealed by comparison of these data with those of C8/10 APG. As previously observed 1131, acute toxicity to fish and, in smaller measure, to daphnia and algae decreases with decreasing alkyl chain length of the surfactant. For this reason, the more detailed investigations into Table 2. Ecotoxicological data o f CI2ll4a n d Cs/loAPG from standard tests (all figures refer to active substance) Test

Evaluation parameter

b Acute toxicity Fish (Brachydanio rerio, 96 h) Daphnia (D. magna, 48 h) Algae (Sc. subspicatus, 72 h) Bacteria (Ps. putida, 30 min)

Mortality, LC50 Ability to swim, EC50 Cell multiplication, EC50 Oxygen consumption, ECO

b Subchronic/chronic toxicity Fish (Brachydanio rerio, 4 w) Daphnia (D.magna, 3 w) Algea (Sc. subspicatus, 72 h) Bacteria (Ps. putida, 18 h)

Growth, NOEC Reproduction, NOEC Cell multiplication, NOEC Cell multiplication, NOEC

b Terrestrial toxicity Earthworm (Eisenia foet., 2 w) Terrestrial plants (oat/turnip/tomato, 14 d)

Mortality, LCO Growth, NOEC

*Concentration analytically confirmed (see Chapter 3)

12/14

8/10

[mg/ll

[mg/ll

3.0* 7.0* 6.0 500

1.8'

LO* 2.0 5000

654 mg/kg 654 mg/kg, each

101 20 21

5.7 1700

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the long-term ecotoxicity of alkyl polyglycosides were conducted with the relatively more toxic C12114 alkyl polyglycoside homologue (c12/14 APG). The acute bacterial toxicity as determined in the oxygen consumption inhibition test was very low at ECO = 500 mg/l (maximum concentration tested). Since this test is very effective in estimating the toxic tolerance limits of model sewage treatment plants [141, it can be predicted that the risk of acute toxic effects of alkyl polyglycosides on microorganisms present in wastewater treatment plants will be virtually nil. 2.2 Long-term aquatic toxicity

Although acute toxicity data allow the ecotoxicological classificationof a chemical substance, the validity and the predictive value of an environmental risk assessment is significantly improved if the “predicted no effect concentration” (PNEC) is based on subchronic/chronic toxicity data. In the 4-week prolonged fish test using growth (length, weight) as test criteria, the “no observed effect concentration” (NOEC) of c12/14 APG was 1.8 mg/l; long-term fish toxicity is thus of the same order of magnitude as acute toxicity. In the daphnia 21-day reproduction test, a chronic toxicity NOEC of 1 mg/l was observed, representing the most sensitive end point of all the ecotoxicological investigations conducted. In the chronic algal cell multiplication inhibition test, the NOEC was 2 mg/l. On the other hand, the NOEC of the bacterial cell multiplication inhibition test was 5000 mg/l (maximum concentration tested) for Cl2ll4APG and 1700 mg/l for Cs/loAPG, confirming the very low bacterial toxicity of alkyl polyglycosides already observed in the acute bacterial toxicity test. 2.3 Terrestrial toxicity

Because surfactants can also enter terrestrial environments, for example where sludges are used as fertilizers for agricultural soils, the terrestrial toxicity of C W APG ~ ~ was determined in acute and chronic tests. The acute toxicity test on earthworms in artificial soil did not show any adverse effects, even at the highest concentration tested (654 mg/kg). The same alkyl polyglycoside concentration was found to be the NOEC for three different higher plant species in the chronic plant growth tests involving oats, turnips and tomatoes, demonstrating the very low terrestrial toxicity of this surfactant. 2.4 Biocenotic toxicity in a model river system

Finally, c12/14 APG was also tested in a river flow model system [15,161 to ascertain how the degradation and ecotoxicological properties of the surfactant

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Josef Steber, Walter Guhl, Norbert Stelter, and Frank Roland Schroder

would affect the biocenosis of surface waters. This “stage model” consisted of two lines of eight tanks arranged in stages and in tandem (Figure 4). The diluted (1/3 v/v) effluent of a model sewage treatment plant 131 fed with synthetic sewage without test substance was continuously added to the first tank of each river flow line; the hydraulic retention time in each tank was 3 hours. At the end of the 4-week working-in period of the model (without C ~ 1 4APG addition), the riverine model biocenoses in the two flow systems (lines) were comparable and consisted of 19 different species of algae, protozoans and small metazoans representing 6 different trophic levels. C12/14 APG was then continuously added to the effluent of the first tank of one of the river flow lines over a 4-week period; this resulted in an influent concentration of 5 mg/l of c12/14 APG in the second tank. The weekly biological analysis of the species and their abundance in each tank was based on biological parameters [171and enabled the biocenoses in the parallel tanks of the c12/14 APG-loaded line and the control line to be compared. In addition, the c12/14 APG concentrations in the individual tanks were analytically determined 3 times weekly over this period. A significant biocenotic difference between the No. 2 tanks of the two parallel flow systems was observed two days after the first CWMAPGaddition (Figure 4). This dissimilarity, indicative of a toxic effect, was only observed in tank 2 for the entire duration of the test, no dissimilaritybeing observed in any of the following tanks. This shows that the toxic level of the surfactant falls after only a 3-hour flow time corresponding to an C12/14APG concentration of 2.13.0 mg/l (as measured in tank 3). The results of the biological and chemical c12/14 APG analyses in the individual tanks of the river flow model test system are set out in Figure 4. The data show that the biocenotic NOEC of C12114APG Similarity [%I

APG Irng/ll

- 100

j:

- 90 - 80

2

- 70

1

- 60

Tank no.

Diluted STP effluent

Tank no.

Figure 4. Scheme of the river flow model and results from biological and chemical analyses after 4 weeks’ addition of C ~ 1 4APG

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in a model surface water is 22.1 mg/l and below 5 mg/l, the second concentration figure being the LOEC (lowest observed effect concentration). In addition, the regeneration time of the river model biocenosis was tested by biological analysis of tank 2 after the addition of C12/14MG had been stopped. No difference in relation to the control was found after 5 days, indicating a considerably faster reversibility of the ecotoxicological effects of c12/14APG as compared with other surfactants [181. Accordingly, even a significant local ecotoxicological effect attributable to high concentrations of alkyl polyglycoside in untreated wastewaters would not have any long-term impact on the river water biocenosis. 3. Environmental risk assessment and conclusions

The environmental compatibility assessment of chemicals is based on comparison of the Predicted Environmental Concentration (PEC) and the ecotoxicological Predicted No Effect Concentration (PNEC) [1,191. The PEC estimation (exposure assessment) and the PNEC prediction must be based on realistic worst-case assumptions, i. e. the scenarios used for evaluation of the environmental fate and effects of a compound have to rely on stringent but realistic conditions U91. Taking these requirements for the PEC assessment of alkyl polyglycosides into account, an exposure scenario clearly overestimating the role of alkyl polyglycosides in detergents and cleaners was selected. This may imply the increasing use of this new group of surfactants in a number of applications. This scenario presupposes the use of alkyl polyglycosides as sole nonionic surfactant in all heavy-duty detergents in Germany. Based on a population of 81 million, the use of 580,000 tons of this product group per year [201and an average water consumption of 200 lhnhabitantlday [191, it can be calculated that the concentration of detergent-range nonionic surfactants 6-10 010 content in detergents [211) in raw sewage will be 10 mg/l at most. Since alkyl polyglycoside removal in sewage treatment plants exceeds 99% (see 1.2), it can be predicted that the alkyl polyglycoside effluent concentration will be below 100 pg/l. Another conservative estimate widely used for exposure assessment [191 is the effluent/ river water dilution factor of 10. Accordingly, the PEC of alkyl polyglycosides in river water is less than 10 pgA. As previously mentioned, this figure stems from a clear overestimation of the real alkyl polyglycoside consumption figures and does not take the in-stream biodegradation of this surfactant in account. Such effective removal can be expected from the ready biodegradability of alkyl polyglycosides and has been demonstrated in the river flow model system (see 2.4).

A similarly conservative approach was used for the PEC assessment of alkyl polyglycosides in sludge-fertilized soil. Based on the worst-case scenario de-

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Josef Steber, Walter Guhl, Norbert Stelter,and Frank Roland Schroder

scribed above predicting a raw sewage influent concentration of 10 mg alkyl polyglycoside/l, the sewage plant sludge concentration was calculated using the HAZCHEM mathematicalfate model [221. The predicted sludge concentration of 8 g alkyl polyglycoside/kg dry matter suggested an alkyl polyglycoside concentration of about 0.8 mg/kg in digester sludge assuming at least 90% degradation of adsorbed alkyl polyglycoside during the sludge digestion process. Where digester sludge is used for agricultural purposes at an annual application rate of 0.5 kg/m2 [191,the predicted alkyl polyglycoside concentration in the top 20 cm layer of soil is 1.3 mg/kg. This figure ignores any biodegradation of alkyl polyglycosides in the soil. Thus, the low PEC value is a figure well above even the realistic concentrations. The effects assessment of alkyl polyglycosides for estimation of the PNEC is based on a broad range of ecotoxicological investigations into the acute, subchronic, chronic and biocenotic toxicity of this surfactant (Table 2). The relatively long-chain CWI~ APG was used for the PNEC evaluations because it is the more ecotoxic homologue. The NOEC (no observed effect concentration)values of alkyl polyglycosides in the bacteria1 growth inhibition test and in the respiration inhibition test are several orders of magnitude higher than the concentration expected in the aerator of a sewage treatment plant, being equivalent to the PEC in the plant effluent [191. In addition, the excellent purification performance of the model sewage treatment plant, even at alkyl polyglycoside influent concentrations of 36 mg/l (equivalent to 20 mg C/1, see 1.2), confirms the conclusion that the industrial use of alkyl polyglycosides will not have any adverse effects on wastewater treatment plants. The river water PNEC of alkyl polyglycosides was derived from the NOEC of the most sensitive species among the aquatic organisms tested in subchronic/ chronic tests. According to the EU guidance document on environmental risk assessment 1191,the result of the 21-day daphnia reproduction test (NOEC = 1 mg/l) led to a PNEC of 100 pg/l by application of an assessment factor of 10. In spite of the extremely conservative characteristics of the PEC value, the PEC/ PNEC ratio of 0.1 shows unequivocally that there is no environmental risk, even where alkyl polyglycosides are used in large quantities. The environmental safety of alkyl polyglycosides in surface waters is also assured in cases where discharges of untreated sewage may occur. As shown by the studies using the model river system, even an alkyl polyglycoside concentration of 5 mg/l would only result in a slight biocenotic effect at the immediate inflow site and would not have any adverse effects downstream by virtue of the rapid biodegradation of alkyl polyglycosides (half-life time _<2hours). In the final analysis, comparison of the very conservative PEC of alkyl polyglycosidesin sludge-fertilized soils with thePNEC of soil organisms (NOEC

Ecological Evaluation of Alkyl Polyglycosides

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divided by an application factor of 100) [191 also reveals no environmental risk (PEC < PNEC). Thus, the ready biodegradability of alkyl polyglycosides under all environmental conditions and their favourable ecotoxicological propertiesrecently confirmed by an independent study 1231-will ensure that even the use of alkyl polyglycosides in a variety of applications will not endanger the environment. This combination of favourable ecological properties was also the reason why alkyl polyglycosides were the first group of surfactants to be given the favourable class 1 rating under the German water hazard classification (WGK). In conclusion, it may be said that alkyl polyglycosides represent a class of modern nonionic surfactants which have been comprehensively studied for their ecological behaviour. They exhibit excellent environmental compatibility. References

1. EEC (1994) Commission Regulation (EC) No. 1488194 of June 28, 1994, Off. J. Europ. Comm. L 161, June 29, 1994 2. OECD (1993): OECD Guidelines for the Testing of Chemicals, Volume 1, Section 3 : Degradation and Accumulation, OECD, Paris 3 . EEC (1982): Council Directive of 31 March 1982 (82/242/EEC), Off. J. Europ. Comm. L 109, April 22, 1982 4. EEC (1986): Guidance Document of the Competent Authorities for the Implementation of Directive 79/831/EEC, Doc. XI/861/86 final 5. J. Steber, W. Guhl, N. Stelter, F. R. Schroder, Tenside Surf. Det. 32 (1995) 515 6. P. Gerike, W. Holtmann, W. Jasiak, Chemosphere 13 (1984) 121 7. P. Schoberl, Tenside Surf. Det. 31 (1994) 157 8. R. R. Birch, C. Biver, R. Campagna, W. E. Gledhill, U. Pagga, J. Steber, H. Reust, W. J. Bontinck, Chemosphere 19 (1989) 1527 9. EEC (1984):Commission Directive of April 25, 1984 (84/449/EEC), Off. J. Comm. L 241, Sept. 10, 1984 10. OECD (1993): OECD Guidelines for the Testing of Chemicals, Volume 1, Section 2: Effects on Biotic Systems, OECD, Paris 11. DIN 38412: German standard methods for the examination of water, waste water and sludges; bioassays (group 2) 12. P. Schoberl, L. Huber, Tenside Surf. Det. 2 5 (1988), 86 13. P. Berth, P. Gerike, P. Gode, J. Steber, Tenside Surf. Det. 2 5 (1988) 108 14. W. Guhl, P. Gode, Vom Wasser 72 (1989) 165 15. N. Scholz, F. J. Muller, Chemosphere 25 (1992) 563 16. W. Guhl, Z. angew. Zool. 74 (1987) 385 17. W. Guhl, Limnologica 18 (1987) 1

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18. W. Guhl, UBA-Forschungsbericht 10603057 (1989) 19. EEC (1994):Risk Assessment of Existing Substances, Technical Guidance Document, European Commission DG XI, Brussels 20. IKW (19941, IndustrieverbandKorperpflege- und Waschmittel e. V., FrankfUrt/M. 21. H. Upadek, P. Krings, Seifen, Ole, Fette, Wachse Journal 15 (1991) 554 22. ECETOC European Centre for Ecotoxicology and Toxicology of Chemicals) (19941, HAZCHEM, Special Report No. 8, ECETOC, Brussels 23. T. Madsen, G.Petersen, C. Seierra, J. Tnrrslrav, J. Am. Oil Chem. SOC.73 (1996) 929

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

12. ife-Cycle Inventory of Alkyl Polyglycosides Frank Hirsinger

This chapter describes the input and output of mass and energy flow for the production of alkyl polyglycosides based on coconut and palm kernel oil. The data used in this study were generated in accordance to the SETAC Code of Practice [ 1I. The method of calculating and aggregating the data and the results are reported and peer-reviewed in the European Surfactant Study of the Ecosol Group of the European Chemical Manufacturers Association (CEFIC) 12-14]. The Ecosol Group was founded by 13 major European surfactant producers with the aim of supplying realistic LCI data of the 7 most important surfactant types: linear alkylbenzene sulfonate (LAS) 1101, fatty alcohol sulfate (FAS) [6,13,141, alcohol ethoxylate (AE) [81, alkyl ether sulfate (AES)[91, secondary alkane sulfonate (SAS),soap [71 and alkyl polyglycosides [51 under European conditions. A Life Cycle Inventory (LCI) consists of the input of the raw materials for chemical and energetic conversion during processing and manufacturing of products and energy components (such as steam and electricity) and the output of products, emissions and waste associated with the various production steps (Figur 1).An LCI is part of a complete Life Cycle Analysis (LCA)which, besides the LC-Inventory, also includes an LC-Impact Assessment. The methodology for conducting such an Impact Assessment is still being established by SETAC and I S 0 working groups so that this procedure is not applied in this chapter. 1. Manufacturing process

The following steps are involved in the production of alkyl polyglycosides and have been included in the analysis (Figure 1): - Coconut oil (CNO) alcohol or palm kernel (PKO) alcohol production - Nitrogen (N) fertilizer production - Phosphate (P) fertilizer production - Potassium (K) fertilizer production - Limestone production - Lime production - Corn production - Sulfur production - Glucose monohydrate production - Caustic soda production - Alkyl polyglycoside production.

Limestone production

Lime production

fertilizer

Potassium

Phosphate fertilizer

femlizer

-

monohydrate production

-

Energy of material resource (EMR)

(CNO or WO)

--.

-

System border

Salt production

Sulfur production

Corn production

Production of alkyl polyglycosides

4

Final product

I 1

Process energy Transport energy Fossil feedstock energy Renewable feedstock energy

Atmospheric emissions Fossil/non-fossil CO2 NOx sox Particulates Hydrocarbons co

Figure 1. An LCI measures the overall input/output-situation of raw materials and energy and the derived products plus the different types of wastes and emissions. Inside: Flow diagram for the production of C 1 m alkyl polyglycoside.

Raw materials Rock salt Coal Sulfur Natural gas Fresh fruit bunches Petroleum

Solid waste

Wastewater BOD COD Dissolved solids Suspended solids

x $ I

r \I)

Life-Cycle Inventory of Alkyl Polyglycosides

193

Alkyl polyglycosides are produced from fatty alcohol and glucose by the Fischer-Synthesis (see Chapter 2). Two processes may be used: the direct synthesis (one-step) or the transglycosidation reaction (two-step). This chapter provides a detailed summary of the energy requirements and environmental emissions for the production of 1000 kg of c12/14 alkyl polyglycoside from glucose monohydrate and c12/14 fatty alcohol. The glucose monohydrate is derived from corn while the fatty alcohol is derived from coconut oil or palm kernel oil. This analysis includes all steps involved in the sequence of processes from raw material acquisition through final production and transportation of alkyl polyglycosides to detergent manufacturers. The making up of alkyl polyglycosides into detergents and the subsequent disposal of these products or of alkyl polyglycosides are not included in this analysis. The present analysis examines alkyl polyglycoside production in Europe. In 1995 commercial production in Europe had just started. A European average for fuel production and combustion was used to calculate the energy requirements of, and emissions from, the alkyl polyglycoside production step on the assumption that alkyl polyglycosides are produced in equal quantities in Belgium, France, Italy, Germany, Spain, the Netherlands, and the United Kingdom. It is assumed that the glucose raw material is derived from corn produced primarily in France, Germany, Italy and Spain and that the fatty alcohol raw material is derived from coconut oil and palm kernel oil. Fatty alcohols from coconut and palm kernel oil are produced primarily in France, Belgium, Germany and the United Kingdom. 1.1 Production of alkyl polyglycosides

Alkyl polyglycoside surfactants are derived from glucose and long chain linear alcohols in either a one-step or two-step process. The typical one-step process (direct synthesis) involves direct acetalization of alcohols with glucose. The resulting products are glycosides and water. Water is removed by low pressure evaporation. The two-step process involves the reaction of glucose or starch with a low-boiling alcohol, typically n-butanol, to form a butyl glycoside intermediate. This intermediate subsequently reacts with the fatty alcohol in the presence of a strong acid as catalyst. The resulting products are glycosides, butanol and water. The butanol is continuously removed from the glycoside product during the reaction. In both, the one-step and the two-step process, product properties are determined mainly by two parameters: chain length of the fatty alcohol and the degree of polymerization (DP) of the glycoside. The degree of polymerization is determined by the ratio of glucose to fatty alcohol. For the two-step process, it is assumed that n-butanol is recovered and recycled internally in the process with only negligible losses and, accordingly,is not

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Frank Hirsinger

included as a raw material input into this analysis. It is also assumed that data for alkyl polyglycoside production will be independent of the alcohol source. Depending on the process, several refinery grades of glucose may be used, including starch, glucose syrup, glucose monohydrate and anhydrous glucose. The present analysis is based on glucose monohydrate. Data for the one-step and two-step process have been aggregated. It is assumed that the degree of polymerization is about 1.4 and that C W Ifatty ~ alcohols are based on coconut and palm kernel oil of which the production is described separately 141. 1.2 Glucose production

The recurring monomer in alkyl polyglycosides is glucose derived from corn. The commercial material is in the form of the monosaccharide D-glucose,either anhydrous or as monohydrate. The production of glucose from corn begins with the wet milling process. Corn, with a moisture content of about 159'0,is first cleaned to remove coarse and fine materials. It then enters the wet milling process which begins with introduction of the corn into a solution of 0.12 to 0.2 9'0 sulfur dioxide (50"C for 50 hours), to soften the kernel and to assist in breaking down the protein-starch matrix. The softened corn is lightly milled, freeing the germ from the kernel. The germ is then separated from the kernel and processed for oil removal. The remaining corn fraction (mostly starch, protein and hulls) is then thoroughly milled. The starch is washed from the hulls from which it emerges as a starch slurry. The slurry goes through successive stages of cleaning and separation in which the protein fractions are removed and processed for sale. The starch slurry undergoes one or more hydrolytic processes to yield crystalline glucose. Three hydrolytic processes (acid, acidenzyme or enzyme-enzyme) may be used to produce glucose. The present study is based on enzyme-enzyme hydrolysis of starch into glucose. The first step in this process is liquefaction by the addition of bacterial amylase. After acidification, the break-down of starch into glucose is completed by the addition of fungal glucoamylase. The resulting high-purity liquor is crystallized and sent to rotary dryers. The production of 1000kg of glucose solids from corn is accompanied by the production of 493 kg of gluten and gluten meal (used in animal feed) and 108 kg of germ. These are considered as co-products and credit for them has been applied based on the relative mass of each product output. All coproducts are based on 1000/0 dry matter. 1.3 Corn growing and harvesting

The energy requirements and emissions ino the environment resulting from the production of corn vary greatly from region to region. Weather conditions, the

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length of the growing season, soil conditions, topography, and farming techniques affect the production process. Corn is a warm weather crop requiring a growing season of about 140 days with an average daytime temperature of 24 "C and nighttime temperatures above 14°C. The length of the growing season affects the moisture content of the harvested corn. The desired moisture content of corn is about 15 Yo. Corn harvested early will have a higher moisture content. Accordly, controlled crop drying may be necessary to reduce the moisture content to the optimum level. For this analysis, it is assumed that corn is harvested with an average moisture content of 2 5 % and is subsequently dried to a moisture content of 15010.Irrigation may also be necessary to supplement rainfall. For this analysis of corn grown in Europe, however, it is assumed that no irrigation is necessary. Fertilizers are often added to apply necessary nutrients to the soil. The fertilizer used on corn fields is a combination of nitrogen, phosphorus (phosphate), and potassium (potash).Lime is often applied with the fertilizer to adjust the soil pH to levels best suited for corn production. Since the application of fertilizers can vary greatly from region to region, average values typical of regions with sufficient rainfall to make irrigation unnecessary have been used for fertilizer application to European corn fields. Although not included in this analysis, some pesticides may also be used, depending on circumstances. The application of fertilizers and pesticides can result in waterborne emissions from run-off. These emissions are dependent upon topography, farming techniques, amounts of rainfall and irrigation and other regional factors and are therefore difficult to estimate. Accordingly, no waterborne emissions are examined in this analysis. The data are based on an average yield of 6.8 tonnes of cordhectare. Diesel fuel is used for cultivation and harvesting machinery. It has been assumed that liquefied petroleum gas (LPG) is used as the fuel and for drying the corn to reduce its moisture content from 2 5 010 to 15Yo. Modern harvesting removes only the corn from the field, leaving the stubble behind in the field. Stubble is not included in the analysis because it remains in the field to become compost and is plaughed back into the soil. Accordingly, no solid waste is included in the production of corn. No coproduct credit is given to the stubble. The energy of material resource has been calculated from the calorific value of field corn. 1.4 Lime and limestone production

Lime used in the production of corn and in the manufacture of glucose is produced by calcinating limestone so that the water present is driven off and the carbonate decomposes into lime (calciumoxide) and COZ.Limestone is quarried primarily from open pits. The most economical method of recovering the stone has been blasting, followed by mechanical crushing and screening.

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1.5 Nitrogen fertilizer production

Nitrogen as a single nutrient is commonly applied in the form of anhydrous ammonia (82%by weight nitrogen), primarily by steam reformation of natural gas. Natural gas and steam are fed into a tubular furnace where the reaction over a nickel reforming catalyst produces hydrogen and carbon oxides. The primary reformer products are then mixed with preheated air to produce the nitrogen needed for ammonia synthesis. The gas is cooled and subjected to a water shift reaction in which CO and steam are reacted to form COZand hydrogen. The COZis removed from the gas by absorption and the hydrogen and nitrogen are subsequently reacted in a synthesis converter to form ammonia. The following steps are involved in the processing of nitrogen fertilizer: - Natural gas production - Natural gas processing - Ammonia production - Nitrogen fertilizer production. 1.6 Phosphate fertilizer production

Phosphate fertilizer applied as a single nutrient is most commonly in the form of either superphosphate with 16 to 2 0 % available PZOS or triple superphosphate with 44 to 51% available P205. Superphosphates are produced by the action of sulfuric acid on phosphate rock while triple superphosphates are made by adding phosphoric acid to phosphate rock. It is assumed that the phosphate rock used to produce phosphate fertilizer is mined in the United States. The data for the production of phosphate fertilizers are based on half the phosphate being applied as superphosphate and half as triple superphosphate. 1.7 Potassium fertilizer production

Potash fertilizer is generally applied in the form of potassium chloride (KC1) which is sold in various agricultural grades containing 60 to 62 Yo, 48 to 52 010 or 22 Yo K20. The following steps are included in the production of potassium fertilizer: - Sylvite mining and processing - KCl production - Potassium fertilizer production. KC1 is obtained from sylvite ore and purified by fractional crystallization or flotation. Since no data were available for the production of sylvite ore, they were assumed. Sylvite mining and processing is similar to salt mining and processing. KCl is produced from sylvite ore by passing hot liquor through a

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197

series of steam-heated turbomixer dissolvers in countercurrent to a flow of crushed ore. KC1 and a small amount of NaCl pass into solution. When the solution is cooled from its boiling point, KC1 separates out. Tailings from the process, largely NaC1, are removed from the plant and stored as waste. A large part of the process liquor is decanted and reused. KC1 may be also produced from brines. The potash fertilizer analyzed in this study is based on application as KC1 containing 50 010 KzO.It is assumed that 75 010 of the KC1 is produced from sylvite and 2 5 % from brine extraction. These data are assumed to be representative of KC1 production in Europe. 2. Total resource requirements and environmental emissions 2.1 Raw material requirements (alkyl polyglycoside/CNO, alkyl polyglycoside/PKO)

The overall resource requirements for the production of alkyl polyglycosides from coconut (CNO) and palm kernel oil (PKO) are shown in Table 1. The amount of fossil chemical raw materials (18kg natural gas and 1 kg coal) is small when compared with 197 kg coconut oil and 229 kg palm kernel oil. This is, of course, an indication of the high proportion of renewable resources in the final product alkyl polyglycoside. For this presentation, the vegetable oils were chosen as the main product of interest rather than the harvested agricultural products coconuts and oil palm fresh fruit bunches (FFB).The 197 kg of coconut oil and the 229 kg of palm kernel oil are obtained from 1319 kg of husked coconuts and 1145 kg of FFB. These harvested agricultural products contain about 30 to 4OWo of water and 40 to 50% of low-value byproducts such as shells, residual husks and fibres. Choosing them as the primary product would be as unrealistic as taking the brine-and-crude-oil mixture which is normally pumped out of the well as the primary product. In this case, the values for crude oil would be about 10 times higher than listed in Table 1. For the same reason, the starch source is not the corn which is harvested from the field, but the 631 kg of corn starch obtained from the corn cobs in a 57 010 yield for a dry matter content of 85 O/o. 2.2 Energy requirements for coconut oil based alkyl polyglycoside

The total energy requirements for the alkyl polyglycoside production are set out in Table 2. The energy of material resource of corn, calculated as the calorific energy value of corn for 15010 moisture, represents 10 GJ of the total energy. The energy of material resource associated with coconut oil alcohol, which is the combustion energy value of the whole coconut, represents another 27.8 GJ. The total energy contribution of the husked coconuts (27.8 GJ) consists

198

Frank Hirsinger

Table 1. Overall resource requirements for the production of 1000 kg of alkyl polyglycoside/CNO and alkyl polyglycoside/PKO (SO010 active substance) Raw material

Energy resource [kgl

Total resource

[kgl

0 18.2 1 0 197 631 1

153 220 247 65 0 0 0

153 238.2 248 65 197 631 1

4 77 12.7 6.8 9.6

0 0 0 0 0

4 77 12.7 6.8 9.6

0 18.2 1 0 229 631 1

194 222 247 270 0 0 0

194 240.2 248 270 229 631 1

4 77 12.7 6.8 9.6

0 0 0 0 0

4 77 12.7 6.8 9.6

[kgl

b Alkyl polyglycoside/CNO

Crude oil Natural gas Coal Husked coconuts Coconut oil Corn starch Sulfur NaCl Limestone N-fertilizer P-fertilizer K-fertilizer b Alkyl polyglycoside/PKO Crude oil Natural gas Coal FFB Palm kernel oil Corn starch Sulfur

NaCl Limestone N-fertilizer P-fertilizer K-fertilizer

Source: FraI

in Associates, Ltd.

of the EMR (energy of material resource =“feedstock energy”)of 26.2 GJ and 1.6 GJ of fuel energy (burning of coconut shells in tapahan dryers for copra drymng). The major proportion of the total energy (Table 2) is the EMR (59.3O/o) whereas transportation is only a minor consumer of energy. At this point, the reader should be reminded that the EMR values in the case of alkyl poly-

Life-Cycle Inventory of Alkyl Polyglycosides

199

glycosides are mostly (98010)attributed to the renewable resources coconut oil and corn starch. These sources are of course based on the use of solar energy via plant photosynthesis and do not contribute to a depletion of fossil energy sources. The energy sources for the production of 1000 kg of alkyl polyglycoside are set out in Table 3. The energy totals of Tables 6 and 7 are of course the same. It is just interesting to compare the sourcing of the various energies (Table 7) and their use as process, transport and “feedstock” energy (EMR). Energy from biomass accounts for 58 010 of the total energy for alkyl polyglycosides. Approximately 73 o/o of this energy derived from biomass is the energy of material resource (EMR) attributed to whole coconuts in coconut oil alcohol production. The remaining 27010 of the biomass energy is the energy of material resource to corn used in glucose monohydrate production. Most of the total energy is consumed in the CNO alcohol production step and the alkyl polyglycoside processing step. The amount of total fossil and nuclear energy (nonrenewable) results in 27.1 GJ. This value is comparatively low when compared with the data for other surfactants listed in Figure 2. The data are taken from the ECOSOL publication [21. It is clear that different surfactants cannot be compared with one another in regard to energy data, especially if they differ in their chemical composition and the functions they perform in their applications. However, such comparisons may be used to provide a rough estimate of the consumption of non-renewable energy (fossil and nuclear energy) for different surfactants. alkyl polyglycoside surfactants are thus among the lowest energyconsuming surfactants, such as alcohol sulfates and soap. It may be concluded from this that alkyl polyglycoside surfactants consume less than half the total energy consumed in the manufacture of petrochemical surfactants such as LAS, petrochemical AS, petrochemical alcohol ethoxylate and petrochemical alcohol ether sulfate. 2.3

Environmental emissions for coconut oil based alkyl polyglycosides

2.3.1 Atmospheric emissions (alkyl polyglycoside/CNO)

The total atmospheric and waterborne emissions resulting from the production of 1000 kg of alkyl polyglycoside based on coconut oil are shown in Table 4. Emissions from the production and combustion of fuels account for most of the atmospheric emissions. Fuel-related emissions account for 99 010 of the nitrogen oxides, 94% of the hydrocarbons, 9 7 % of the sulfur oxides, 61% of the CO and over 9 9 % of the COZfrom fossil sources. Process emissions account for 64% of the particulate emissions, most of which come from the production of limestone, and for 91% of the methane

[%I

1.02 0.008 0.034 0.023 0.009 0.012 0.10 5.6.10-4

11.5 0.2 0.2 0.3

0 0.4 2.6 0 4.1 0 0.2 18.0 37.4

7.48 0.10 0.12 0.22 0.0075 0.23 1.70 0.0037 2.69 0.005 0.11 11.7 24.3

PKO alcohol N-Fertilizer P-Fertilizer K-Fertilizer

Limestone production Lime production Corn production Sulfur production

Glucose monohydrate production Salt production Caustic soda production Alkyl polyglycoside

Alkyl polyglycoside total

2.15

0.22 0.0055 0 0.72

3.3

0.3 0 0 1.1

0 0 0.2 0

1.6 0 0.1 0

Transport energy

[%I [GJI

Process energy [GJI

38.6

0 0 0 0

0 0 0 10

27.8 0.68 0.036 0

Table 2. Energy summary for the production of alkyl polyglycoside from coconut oil (in GJAOOOkg)

100

4.5 0 0.2 19.1

2.90 0.01 0.11 12.4 65.1

0 0.4 18.2 0

0.016 0.024 11.8 0.0042

55.8 1.2 0.3 0.4

36.3 0.79 0.19 0.24

Source: Franklin Associates, Ltd.

59.3

0 0 0 0

0 0 0 15.4

42.7 1.1 0.1 0

[%I

Total [GJI

!??

0 0

h,

0.011 0.0024 0.017 0.12 0.31 0.025 6.78.m4 1.83.10-4 0.28 0.0022 0.0057 3.30 6.82

7.16.10-4 0.095 1.43 0.0032 1.01 0.0025 0.021 4.45 12.2

Limestone production Lime production Corn production Sulfur production

Glucose monohydrate production Salt production Caustic soda production Alkyl polyglycoside

Alkyl polyglycoside total

6.51

0.99 0.0034 0.044 3.82

2.83 1.39 2.97.10-4 0.0029 0.039 0.06 0.017 0.046

4.14 0.79 0.044 0.16

CNO alcohol N-Fertilizer P-Fertilizer Potassium fertilizer

Coal

Crude oil

Natural gas

1.69

0.56 0.0021 0.033 0.75

0.002 0.011 0.025 1.47.10-4

0.25 0.0028 0.043 0.009

Nuclear

Biomass

0.3

27.1

37.6

0 0 0 0

0 0 10 0

65

2.9 0.01 0.11 12.4

0.016 0.24 11.8 0.0042

36.3 0.79 0.19 0.24

Total

Source:Franklin Associates, Ltd.

0.057 2.64.W4 0.0034 0.076

2.651.10-4 0.0015 0.0034 1.48.W5

0.15 27.5 3.80.W4 0 0.003 0 0.0017 0

Hydropower

2.84 0.01 0.11 12.34

0.016 0.24 1.8 0.0042

8.65 0.79 0.18 0.22

Total nonrenewable

Table 3. Energy profile for the production of alkyl polyglycoside from coconut oil (in GJAOOO kg)

202

Frank Hirsinger

FAS-PO

Fatty alcohol

FASP~ I I

Alrnhnl

I

I

AEWc AE3PKO AEXNO

.I--..-.

ethoxylate AE7-CNO

1

I

PKO CNO

Palm kernel oil Coconutoil

I

I

Ta

;

SAS

Tallow Secondary alkane

, I

I

I

II

I

,

I I I I

!!

CNOAa PKO/Ta CNO/PO PKO/PO

Al kyl polyglycoside

PKO CNO

I

I

1

I

20

40

60

I

I

I

AEllPO

I

I

I

I I I

,

I

I I

I

I

80

sulfonate

100 [GJ/1000 kg surfactantl

Figure 2. Profile of non-renewable (fossil and nuclear) energy consumption for different surfactant classes [21

emissions which occur during the esterificationof coconut oil into methyl ester, an intermediate in coconut oil alcohol production. Process emissions are also responsible for all the non-fossil COZ emissions. Of this non-fossil COZ, 79 o/o is produced from the burning of coconut shells in 3apahans". Tapahan dryers are the local copra drying facilities in the Philippines operated by burning coconut shells in open furnaces and drylng the copra on top. The remaining 21Yo comes from the calcination of limestone into lime. Accordingly, 31 kg of COz comes from a mineral source rather than from a fossil or biomass source. 2.3.2 Waterborne emissions (alkyl polyglycoside/CNO)

Fuel-related emissions also account for many of the waterborne emissions (Table 41, i. e. 90 Yo of the sulfides and all or nearly all the hydrocarbons, metal ions and fluorides. Process emissions account for 99 Yo of the acids which come from phosphate fertilizer production. Process emissions account for 97 O/o of the dissolved solids, of which 90 Yo stems from coconut water released during copra production. Process emissions account for 99% of the suspended solids, of which nearly all comes from phosphate fertilizer production.

203

Life-Cycle Inventory of Alkyl Polyglycosides

Table 4. Summary of atmospheric and waterborne emissions for alkyl polyglycoside produced from coconut oil (in kg/1000 kg)

Process emissions b Atmospheric emissions Particulates Nitrogen oxides Hydrocarbons Sulfur oxides

Carbon monoxide

Fossil COP Non-fossil CO2 b Waterborne

Dissoived solids Suspended solids Iron Nitrogen

7.54 0.053 1.01 0.39 1.11 1.71 150

4.17 13.1 14.6 13.7 1.76 1.622 0

2.24 20.7 12.1 6.34 6.98 1.96 1.96

0.019 0.58 0.083 0.013 0.018 1.94. 0

Total

emissions 11.7 13.1 15.7 14.0 2.87 1.623 150

emissions

Acid BOD COD

Fuel-related emissions

2.26 21.2 12.2 6.35 7.00 1.96 1.96

Most of the BOD and COD emissions stem from coconut water released during copra production. It is questionable whether the category of “waterborne emissions” is in fact applicable to this kind of discharge into the environment because it is a soilborne emission. Moreover, it represents a common agricultural practice in the Philippines. The water could of course also be collected, for example for irrigating trees, or could be processed to food products, as in the processing of desiccated coconuts. In many cases, this effluent is immediately treated by the soil bacteria, acting as a kind of local wastewater treatment facility, before it finally reaches groundwater or surface water. Accordingly, it should be measured after this “clarification”process in the same way as all the other process related emissions. Oil emissions are associated with the production of the coconut oil alcohol released during the esterification of coconut oil into methylester.

2.3.3 Solid waste (alkyl polyglycoside/CNO) Table 5 shows the total weight of solid waste generated from the production of 1000 kg of alkyl polyglycoside. Fuel-related solid waste accounts for 45 010 of

204

Frank Hirsinger

the total solid waste from the production of fuels and coal ash from the production of electricity. Process-related solid waste accounts for 55 010 of the total solid waste for the alkyl polyglycoside system. Although only 6 8 kg of phosphate fertilizer are required to produce 1000kg of alkyl polyglycoside, the production of this amount of phosphate fertilizer generates 49 kg of process solid waste, thus making up 66% of the total process solid waste. The solid waste from phosphate fertilizer production is primarily clay “slime”resulting from the processing of phosphate rock. The alkyl polyglycoside production step accounts for 32 o h of the total solid waste. Around 82 010 of the solid waste generated by the alkyl polyglycoside production process is fuel-related solid waste. The production of coconut oil alcohol, including all steps beginning with the harvesting of the coconuts and including the final production of the alcohol, accounts for 17 010 of the total solid waste for the alkyl polyglycoside system. 2.4

Energy requirements for palm kernel oil based alkyl polyglycosides

Table 6 shows the total energy requirements for alkyl polyglycoside production. The energy of material resource (”feedstockenergy”)of corn, calculated as the calorific energy value of corn for 15 Yo moisture, adds 10 GJ. The energy of material resource associated with palm kernel oil, which is the combustion Table 5. Total solid waste for alkyl polyglycoside produced from coconut oil (inkg/ 1000 kg)

1

Process solid waste Fuel-relatedsolid waste Total solid waste [kgl [%I [kgl [%I [kgl [%I

8.78 0.0031 49.0 0

6.5 0 36.2 0

Limestone production Lime production Corn production Sulfur production

0 7.07 0 0.0013

0 5.2 0 0

Glucose rnonohydrate prod. Salt production Caustic soda production Alkyl polyglycoside

0 0.14 0.036 7.66

0 0.1 0 5.7

CNO alcohol N-Fertilizer P-Fertilizer K-Fertilizer

Alkyl polyglycoside total

72.7

53.7

14.2 0.039 0.30 0.48 0.033 1.01 0.68 0.0022

10.5 0 0.2 0.4

0 0.7 0.5 0

23.0 0.042 49.3 0.48 0.033 8.09 0.68 0.0035

10.4 0.051 0.45 35.1

7.6 0 0.3 25.9

10.4 0.19 0.49 42.8

62.7

46.3

135

17.0 0 36.4 0.4

0 6 0.5 0 7.6 0.1 0.4 31.6 100

Life-Cycle Inventory of Alkyl Polyglycosides

205

energy value of the oil palm fresh fruit bunches, adds another 21.3 GJ to the total system energy. The total energy contribution of the oil palm fresh fruit bunches (21.3 GJ) consists of the energy of material resource (EMR) of 17.2 GJ and 4.1 GJ of fuel energy (burning of fibers and shells for self generated energy in the palm oil mill). The major proportion of the total energy is the EMR (52.9 O/o) whereas transport consumes only 3.3 Yo of the total energy. The EMR itself has a proportion of 97 O?o of biomass. The EMR is of course based on the use of solar energy via plant photosynthesis and does not contribute to a depletion of fossil energy sources. Table 7 shows the sources of energy for the production of 1000 kg of alkyl polyglycoside. The energy totals of Tables 6 and 7 are of course the same. It is just interesting to compare the sourcing of the various energies (Table 7 ) and their use as process, transport and “feedstock” (= EMR) energy. Energy from biomass accounts for 53 Yo of the total energy for alkyl polyglycoside. Around 68 % of this energy derived from biomass is the energy of material resource attributed to fresh fruit bunches in palm kernel oil alcohol production. The remaining 32 010 of the biomass energy is the energy of material resource attributed to corn used in glucose monohydrate production. Most of the total energy is consumed for the PKO alcohol production step and the alkyl polyglycoside processing step. The amount of the total fossil and nuclear energy (non-renewable) results in 29 GJ. This value appears comparatively low when compared with the data for other petrochemical surfactants (Figure 2). PKO based alkyl polyglycosides appears to be among the lowest energy-consuming surfactants allowing for the fact that the compared surfactants differ in their chemical composition and perform different functions in their applications. 2.5

Environmentalemissions for palm kernel oil based alkyl polyglycoside

2.5.1 Atmospheric emissions (alkyl polyglycoside/PKO)

The total atmospheric and waterborne emissions resulting from the production of 1000 kg of alkyl polyglycoside based on palm kernel oil are given in Table 8. Emissions from the production and combustion of fuels account for most of the atmospheric emissions. Fuel-related emissions account for 99 O/o of the nitrogen oxides, 93 O/o of the hydrocarbons, 94 Yo of the sulfur oxides, 65 010 of the CO, and 99 Yo of the COz from fossil sources. Process emissons are responsible for two-thirds of the particulate emissions, most of which come from the production of limestone. Process emissions account for over 99 Yo of the methane emissions which are produced during the anaerobic digestion of POME sludge from the palm oil mill in Malaysia. Process emissions also account for all the non-fossil COZ emissions. Of this non-fossil

0.0090 0.012 0.10 5.6.10-4

0 0.4 2.8 0 4.4 0 0.2 19.2 43.9

0.0075 0.23 1.70 0.0037 2.69 0.005 0.11 11.7 26.6

Limestone production Lime production Corn production Sulfur production

Glucose monohydrate production Salt production Caustic soda production Alkyl polyglycoside

Alkyl polyglycoside total

1.99

0.22 0.0055 0 0.72

0.86 0.008 0.034 0.023

16.1 0.2 0.2 0.4

9.79 0.10 0.12 0.22

PKO alcohol N-Fertilizer P-Fertilizer K-Fertilizer

[GJI

[%I

3.3

0.4 0 0 1.2

0 0 0.2 0

1.4 0 0.1 0

[%I

Transport energy

[GJI

Process energy

32.1

0 0 0 0

0 0 0 10

21.3 0.68 0.036 0

[GJI

52.9

0 0 0 0

0 0 0 16.5

0

35.1 1.1 0.1

[%I

Energy of material resource

Table 6. Energy summary for alkyl polyglycoside produced from palm kernel oil (in GJAOOO kg)

1

60.7

2.90 0.01 0.11 12.4

0.016 0.024 11.8 0.0042

32.0 0.79 0.19 0.24

[GJI

Total

100

4.8 0 0.2 20.4

0 0.4 19.5 0

52.7 1.3 0.3 0.4

[%I

0.0024 0.12 0.025 1.83.10-4 0.99 0.0034 0.044 3.82

0.011 0.017 0.31 6.78.10-4 0.28 0.0022 0.0057 3.30 8.59

7.161.10-4 0.095 1.43 0.0032 1.01

0.0025 0.021 4.45 12.2

Limestone production Lime production Corn production Sulfur production

Glucose monohydrate production Salt production Caustic soda production Alkyl polyglycoside

Alkyl polyglycoside total

6.51

0.046

0.06

1.39 0.0029

4.6 2.97.W4 0.039 0.017

Coal

4.23 0.79 0.044 0.16

Crude oil

PKO alcohol N-Fertilizer P-Fertilizer K-Fertilizer

Natural gas

1.69

0.56 0.0021 0.033 0.75

0.002 0.011 0.025 1.47,10-4

0.25 0.0028 0.043 0.009

Nuclear

29.0

2.84 0.01 0.11 12.34

0.016 0.24 1.8 0.0042

10.45 0.79 0.19 0.24

Total nonrenewable

Table 7. Energy profile for alkyl polyglycoside produced from palm kernel oil (in GJAOOO kg)

0.6

31.1

0 0 0 0

0 0 10 0

21.1 0 0 0

Biomass

60.7

2.9 0.01 0.11 12.4

0.0042

11.8

0.016 0.24

32.0 0.79 0.19 0.24

Total

Source: Franklin Associates, Ltd.

0.057 2.64,10-4 0.0034 0.076

2.65.10-4 0.0015 0.0034 1.48.10-5

0.45 3.80.m4 0.003 0.0017

Hydropower

Frank Hirsinger

208

Table 8. Summary of atmospheric and waterborne emissions for alkyl polyglycoside produced from palm kernel oil (in kg/lOOO kg)

b Atmospheric emissions Particulates Nitrogen oxides Hydrocarbons Sulfur oxides

co

Methane Fossil C02 Non-fossil CO2

Process emissions

Fuel-related emissions

Total emissions

8.58 0.15 1.19 0.87

4.28 14.9 15.2 14.5

12.9 13.0 16.4 15.4

1.16 10.9 1.71 343

2.15 0.0017 1792 0

3.31 10.9 1793 343

b Waterborne emissions

Dissolved solids Suspended solids BOD COD

4.66 12.7 0.34 1.71

0.68 0.084 0.014 0.019

5.34 12.8 0.35 1.73

COZ, 91010is produced in thecombustion of shells and fibres at the palm oil mill. The remaining 9 o/o stems from the calcination of limestone into lime. Accordingly, 31 kg of COZ comes from a mineral source rather than from a fossil or biomass source.

2.5.2 Waterborne emissions (alkyl polyglycoside/PKO)

Fuel-related emissions also account for many of the waterborne emissions. They contribute 91Yo of the sulfides and all or nearly all of the hydrocarbons, metal ions and fluorides. Process emissions account for 79% of the acids, which stem from phosphate fertilizer production, and for 87 010 of the dissolved solids, of which 45 o/o are released in the production of glucose monohydrate. Process emissions also account for 99% of the suspended solids, of which nearly all comes from phosphate fertilizer production. Most of the BOD, COD and oil are process emissions associated with the production of the palm kernel oil alcohol. 2.5.3 Solid waste (alkyl polyglycoside/PKO)

Table 9 shows the total weight of solid waste generated in the production of 1000 kg of alkyl polyglycoside. Fuel-related solid waste accounts for 44010 of

Life-Cycle Inventory of Alkyl Polyglycosides

209

the total solid waste. This waste results from the production of fuels and coal ash and from the generation of electricity. Process-related solid waste accounts for 58 Yo of the total solid waste for the alkyl polyglycoside system. Although only 0.8kg of phosphate fertilizer are required to produce 1000 kg of alkyl polyglycoside, the production of this amount of phosphate fertilizer generates 49 kg of process solid waste or 58 Yo of the total process solid waste. The solid waste from phosphate fertilizer production is primarily clay "slime" resulting from the processing of phosphate rock. The alkyl polyglycoside production step accounts for 29% of the total solid waste, of which 82% is fuelrelated. The production of palm kernel oil alcohol, including all steps beginning with the harvesting of the fresh fruit bunches and including the final production of the alcohol, accounts for 24% of the total solid waste for the alkyl polyglycoside system. 3. Improvement opportunities

Several opportunities for improving alkyl polyglycoside production are embodied in the raw materials used, particularly CNO and PKO, and are discussed elsewhere 131. Principal among them are drying processes of copra for the

Process solid waste [kgl [%I

19.5 0.0031 49 0

13.2 0 33.2 0

Limestone production Lime production Corn production Sulfur production

0 7.07 0 0.0013

0 4.8 0 0

Glucose monohydrate prod. Salt production Caustic soda production Alkyl polyglycoside

0 0.14 0.036 7.66

0 0.1 0 5.2

PKO alcohol N-Fertilizer P-Fertilizer K-Fertilizer

Alkyl polyglycoside total

83.4

56.4

Fuel-related solid waste [kgl [%I

15.9 0.039 0.3 0.48 0.033 1.01 0.68 0.0022

Total solid waste [kgl [%I

10.7 0 0.2 0.3

35.3 0.042 49.3 0.48 0.033 8.09 0.68 0.0035

0 0.7 0.5 0

10.4 0.051 0.45 35.1

7 0 0.3 23.8

64.4

43.6

23.9 0 33.4 0.3 0 5.5 0.5 0

10.4 0.19 0.49 42.8

7 0.1 0.3 29

148

100

I

Source: Franklin Associates, Ltd.

210

Frank Hirsinger

processing of CNO and energy self-sufficiencyin palm oil mills, both of which are responsible for substantial atmospheric emissions. In addition, methane formed during the treatment of wastewater from palm oil mills could be recovered and used as an energy source. Although, from a technical point of view, it would be highly desirable to introduce improvements in this regard, it is also important to bear in mind that such decentralized biofuel technologies have difficulty in reaching the standards of modern heat and power cogeneration plants or of municipal sewage treatment plants. Another aspect which is, of course, beyond a technical LCA approach is the high degree of sustainability which such decentralized technologies have achieved first by creating jobs and second by saving fossil energy sources. There is also room for improvement in fertilizer production for growing corn, particularly in phosphate fertilizer production which contributes 66 O/o of all the solid waste and most of the suspended solids of the waterborne emissions for alkyl polyglycoside production. One possibility may be a move to more organic farming and fertilization methods which could possibly reduce this burden by 50 to 80%. Another option is to assess the practices used for the handling and disposal of solid waste in the processing of phosphate rock. Another opportunity for improvement may lie in the refining step of glucose monohydrate production where it may be possible to reduce the waterborne emissions. References 1. F. Consoli et al., Guidelines for Life-Cycle Assessment: A “Code of Practice”, Society of Environmental Toxicology and Chemistry (SETAC), 1993 2. M. Stalmans et al., Tenside Surf. Det. 32 (1995) 84 3. F. Hirsinger, K. P. Schick, M. Stalmans, Tenside Surf. Det. 32 (1995) 420 4. F. Hirsinger, K. P. Schick, W. Schul, M. Stalmans, Tenside Surf. Det. 32 (1995) 398 5. E Hirsinger, K. P. Schick, Tenside Surf. Det. 32 (1995) 193 6. F. Hirsinger, K. P. Schick, Tenside Surf. Det. 32 (1995) 128 7. D. Postlethwaite, Tenside Surf. Det. 32 (1995) 171 8. W. Schul, F. Hirsinger, K. P. Schick, Tenside Surf. Det. 32 (1995) 193 9. H. Thomas, Tenside Surf. Det. 32 (1995) 157 10. J. L. Berna, L. Cavalli, C. Renta, Tenside Surf. Det. 32 (1995) 122 11. W. Klopffer, R. Griefihammer, G. Sundstrom, Tenside Surf. Det. 32 (1995)

3 78 12. D. Janzen, Tenside Surf. Det. 32 (1995) 110 13. F. Hirsinger, Skin Care Forum 13 (1995) 1 14. F. Hirsinger, Der Mathematisch Naturwissenschaftliche Unterricht - MNU (1996), in print

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

13. Patent Situation in the Field of Alkyl Polyglycosides Bernd Fabry

Since Emil Fischer reported on the nature of methyl glucoside towards the end of the last century, there have been more than 2000 publications which are concerned in one way or another with alkyl polyglycosides, their production, their properties and their use. Figure 1provides an overview of the development in the number of publications since 1980. Whereas, 10 years ago, there were still fewer than 50 publications (literature and patents), there are now almost four times that number. Few other fields in surfactant chemistry enjoy such interest and no reduction in the number of publications is foreseeable at the present time. What, however, is the reason for this unusual flood of publications? Alkyl polyglycosides are based on renewable vegetable raw materials, are ecotoxicologically safe like hardly any other surfactant, possess a range of astonishing properties and hence have good prospects of advancing from a speciality product to a basic surfactant in only a few years. Reason enough for a whole number of manufacturers seriously to concern themselves with this class of surfactants. Figure 2 shows the distribution of patentdpatent applications in the alkyl polyglycoside field of the five most important applicants.

Priority year

Figure 1. Number of publications on the subject of alkyl polyglycoside since 1980

213

Patent Situation in the Field of Alkyl Polyglycosides

1. Production of alkyl polyglycosides

1.1 Butanol route and direct acetalization

Alkyl polyglycosides are normally produced from glucose or starch syrup which are acetalized in the presence of acidic catalysts. In practice, a choice can be made between the earlier butanol route and the modern direct acetalization process (Figure 3, see also Chapter 2). In the butanol route, the sugar first reacts with butanol to form butyl polyglycoside which, in a subsequent transacetalication reaction with a longchain fatty alcohol, leads to the desired alkyl polyglycoside. The direct process does not involve the butyl polyglycoside step which is reflected, for example, in a higher odour quality of the products. Both processes-where they use sulfuric acid or p-toluene sulfonic acid as acidic catalysts-were described in Rohm & Haas patents which have meanwhile expired. Accordingly, the basic process is in the public domain. 1.2 Acetalization catalysts

Hitherto, several applications have been filed on the choice of catalysts. Of particular importance is EP-Bl 0132046 (Procter & Gamble) which was granted after opposition on the use of surface-activecatalysts such as, for example, alkyl benzene sulfonic acid or acidic alkyl sulfates; there is a corresponding patent in the USA. Originally, the wording of the patent also encompassed the acidic alkyl sulfate catalysts formed in situ from sulfuric acid and fatty alcohol. In view of the prior art, however, the patentee excluded these embodiments as not corresponding to the invention. Other acetalization catalysts described in the patent literature include alkyl naphthalene sulfonic acid [21, sulfosuccinicacid [31, sulfomonocarboxylic acids

+ BuOH

@OH HO OH

OH

OH

Butanol route

+ ROH

HO@OH

HO@OR

OH

Figure 3. Butanol route and direct acetalization

Direct acetalization

OH

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Bernd Fabry

[41, sulfonated triacetin [51and fluorosulfonic acids [61. Basically, therefore, any of a number of acidic catalysts may be used for the production of alkyl polyglycosides. Their choice is determined by availability, selectivity, reactivity, foaming and colour stability of the resulting alkyl polyglycosides.

1.3 Removal of fatty alcohols In order to displace the equilibrium of the acetalization reaction to the product side, the fatty alcohol is generally used in a large excess. This means that, after acetabtion and neutralization of the acidic catalyst, the excess fatty alcohol has to be removed. Corresponding processes were described for the first time in FR-A 2017240 (Rohm & Haas) from the yea 1970 an,10 years later, in DE-A1 3001064 (BASF). However, EP-B10092876 (Procter & Gamble), which was granted after opposition, is of greater importance in connection with the removal of fatty alcohol. This patent relates to a process for removal of the fatty alcohol which provides for the use of a thin-layer evaporator under turbulent flow conditions; corresponding patents exist in the USA and Japan. Sometime after this development, Hiils AG filed an application on a process for the removal of fatty alcohol (EP-A1 0531647) which only differs from the above-mentioned P&Gpatent in the fact that the thin-layer evaporator is operated under laminar flow conditions. The patent has already been granted in the USA; the outcome of the examination proceedings in Europe is still awaited. However, the question of the flow conditions in the thin-layer evaporator appears to be largely academic because the evaluation depends crucially on the point of measurement and the method of calculation. Henkel's patent EP-B1 0493495, which is at present in opposition proceedings, relates to a process in which the excess fatty alcohol is first partially removed in a falling-film evaporator. Complete removal takes place in a subsequent step carried out in a thin-layer evaporator. Another alternative is to carry out the distillation in a screw-type heat exchanger [71. Although removal of the fatty alcohol can certainly be carried out using the unprotected prior art, for example using only a falling-film evaporator, product quality is generally poorer. The production of alkyl polyglycosides by the butanol process is covered by a large number of patents owned by Huls AG. 1.4 Other process steps

Besides acetalization,neutralization and the removal of fatty alcohol, the bleaching and antimicrobial stabilization of the alkyl polyglycosides are important steps. Henkel's patent EP-B1 0437460 involved in opposition proceedings is of

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importance in this regard insofar as it claims a combination of various process steps from direct acetalization to alkaline bleaching. Other important patents in this connection are EP-B1 0387912, EP-B1 0387913 and EP-B10388857 (Kao)which relate to the alkaline working up of spent fatty alcohol and to the boranate aftertreatment of the alkyl polyglycosides. The antimicrobial stabilization of alkyl polyglycosides is covered by Henkel’s European patent EP-B 1 0556220 which is involved in opposition proceedings. According to the teaching of this patent, the water-containing alkyl polyglycoside pastes are alkalized. A Kao application has the same subject matter, but is anticipated by the Henkel patent 183. The deodorization of alkyl polyglycosides with hot steam is protected by German patent DE-C2 4312559 (Henkel). 2. Mixtures of alkyl polyglycosides and other surfactants 2.1 Mixtures with anionic surfactants

Among the application-oriented patents, Procter & Gamble’s European patent EP-B 1 0070074 occupies a central position. This patent relates to foaming mixtures of alkyl polyglycosides with surfactants containing a sulfate, sulfonate and/or carboxylate group. It can immediately be seen that virtually all anionic surfactants and also betaine surfactants are covered by this combination. Corresponding patents exist, for example, in the USA, Japan and Australia. However, the patent was clearly limited in the course of the opposition and appeal proceedings. Today, it only protects the use of long-chain C,, alkyl polyglycosides with the anionic surfactants mentioned for the production of manual dishwashing detergents. It no longer encompasses the use of alkyl polyglycoside/ anionic surfactant mixtures in the cosmetics field. Mixtures of short-chain alkyl polyglycosides with anionic surfactants are largely unprotected prior art in view of an old Rohm & Haas publication [91. In addition, the patentee declared during the appeal proceedings that betaines did not fall within the scope of the claim. One point which is repeatedly discussed in connection with this key patent is the average degree of polymerization (DP) of the alkyl polyglycosides. EP-B 1 0070074 contains a limitation in regard to the DP of the alkyl polyglycosides with a lower limit of 1.5. Various parties have repeatedly expressed the view that mixtures of, for example, C, alkyl polyglycosides with a DP of 1.3 and anionic surfactants do not fall within the scope of the Procter & Gamble patent and, accordingly, would be free under patent law. In order to be able to evaluate this view, it is necessary to understand what is meant by the degree of polymerization (Figure 4).

Bernd Fabry

216 Amount [wt.-%l loo

9

1

Mono-

0

Di-

Tri-

Tetra-

DP = DP = DP = DP =

1.8 1.57 1.34 1.12

Penta-

glycosides Figure 4. Degree of polymerization

As already mentioned, the acetalization of glucose with fatty alcohols is not strictly selective. In addition to 1 mole of glucose and 1 mole of fatty alcohol, oligoglycosides are also formed. Accordingly,alkyl polyglycosides are not pure monoglycosides (DP= l), but polyglycosides in which the average degree of polymerization (DP) is normally between 1.1 and 1.8 (see Chapter 2). As can be seen from Figure 4, the parameter DP does not stand for a discrete numerical value, but instead for a homologue distribution and, strictly speaking, for a mean value which can be derived from the area below the distribution curve. However, no curves or areas differing significantly from one another correspond to the DP 1.2,1.5 and 1.8,instead clear overlaps are apparent. Because of this, the argument that alkyl polyglycosides with DP of 1.1,1.5 and 1.8 are species to be strictly differentiated from one another is not tenable, neither from the point of view of the chemist nor from the point of view of the patent attorney, even though alkyl polyglycoside types with one DP or another can clearly be shown to have advantages from the performance point of view. Reference is made at this juncture to German patent application DE-A14414696 (Henkel)which relates to the use of alkyl polyglycosides with a low degree of polymerization. Although EP-B 1 0070074 basically discloses mixtures of alkyl polyglycosides with anionic surfactants and illustrates them with a number of examples, e. g. soaps, alkyl sulfates, alkyl ether sulfates, alkyl benzene sulfonates, olefin sulfonates, alkane sulfonates or alkyl betaines, it has left scope for selection inventions. For example, European patent EP-B10358216 (Kao) protects liquid dishwashing detergents containingalkyl polyglycosides and dialkyl sulfosuccinates.

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European patent EP-B1 0384983 (Hiils)relates to surface-active mixtures containing alkyl polyglycosides and ether carboxylic acids. In view of the prior art, however, this patent had to be limited to unsaturated ether carboxylic acids. Also of importance is International patent application WO 95/06702 (Henkel) which relates to mixtures of alkyl polyglycosides with monoglyceride sulfates. This patent application claims compounds with synergistic foaming power in which both the nonionic component and the anionic component are based on vegetable raw materials. German patent DE-C2 4139935 (Kao) claims liquid body-care formulations which contain monoglycerides in addition to anionic surfactants and alkyl polyglycosides. The use of alkyl polyglycosides in bar soaps is the subject of EP-B1 0463912 (Colgate).This patent claims so-called “combibars”which contain defined quantities of soap, anionic surfactants, alkyl polyglycosides and moisturizers. German patent DE-C2 4337031 (Henkel) also relates to combibars containing fatty alcohol ether sulfates and small quantities of alkyl polyglycoside. In addition, bar soaps containing anionic surfactants and 4 to 7 Yo by weight of alkyl polyglycosides are claimed in International patent application WO 95107975 (Henkel). The use of alkyl polyglycoside/anionic surfactant mixtures in dishwashing applications can be dependent upon the above-cited Procter & Gamble patent EP-B10070074. An exception is European patent EP-A10324451 (Kao)which relates to mixtures of alkyl polyglycosides with alkyl or alkyl ether phosphates. Alkyl phosphates do not contain any sulfate, sulfonate or carboxylate groups and, accordingly, do not fall within the scope of the basic patent. Although International patent application WO 94/21769 (Berol) does not relate to a mixture, it does relate to the use of certain short-chain, branched alkyl polyglycoside types, for example based on 2-ethyl hexanol, for the cleaning of hard surfaces. Finally, there is European patent EP-B 1 0432836 (Unilever) which protects the use of alkyl polyglycosides in rinse aids. Other interesting patentslpatent applications on mixtures of alkyl polyglycosides with anionic surfactants include: - DE-A1 4406746 and DE-A1 4406748 (Henkel, not yet granted): toothpastes containing alkyl polyglycosides and lauryl sulfate or coconut oil monoglyceride sulfates - DE-A1 4428823 (Henkel, not yet granted): mixtures of alkyl polyglycosides with acyl glutamates - EP-B1 0457965 and EP-B1 0474915 (Huls, granted): low-foaming detergents containing alkyl polyglycosides, soap and ether carboxylic acids or fatty alcohol ethoxylates - EP-B 1 0511466 (Huls, granted, opposed): water-based cosmetic surfactant compositions containing as thickener a mixture of alkyl polyglycosides and

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small quantities of selected polymers (for example xanthan gum) and optionally electrolyte salts - EP-A1 0572776 (Hiils, not yet granted): bath gels and shampoos containing alkyl polyglycosides, ether carboxylic acids and optionally sulfosuccinates in quantity ratios adapted exactly to one another. 2.2 Mixtures with nonionic surfactants

European patents EP-B1 0075995 and EP-B1 0075996 (Procter & Gamble) claim mixtures of alkyl polyglycosides and nonionic surfactants. Both patents have meanwhile been revoked in the last instance by the Technical Board of Appeal of the European Patent Office on the grounds of inadequate inventive step. However, this does not necessarily mean that mixtures of alkyl polyglycosides with nonionic surfactants are basically free. In view of old Rohm & Haas publications, this applies at best to the use of conventional nonionic surfactants with short-chain alkyl polyglycoside, such as octyl/decyl (C,,,,) polyglycoside. Mixtures of alkyl polyglycosides with mixtures of nonionic surfactants having different HLB values and with alkoxylated polyols are protected by Kao Corp., for example in European patents EP-Bl 0408965 and EP-Bl 0353735. Patent application EP-A2 0409005 (Kao) relates to mixtures of alkyl polyglycosides and sucrose fatty acid esters. International patent application WO 93/07249 (Henkel)relates to mixtures of short-chain (C,,,,) and relatively long-chain (C,,,,,) alkyl polyglycosides which are distinguished by particular performance properties. Corresponding products are marketed by Henkel (Plantacare 2000, Plantaren 2000). Synergistic mixtures of alkyl polyglycosides differingin their chain lengths and DP, which are distinguished by improved dermatologicalcompatibility, are claimed in International patent applicationsWO 94/29416 and WO 94129417 (Henkel). 2.3 Mixtures with cationic or amphoteric surfactants

Mixtures of alkyl polyglycosides with cationic surfactants of the quaternary ammonium compound type are largely in the public domain. However, combinations of alkyl polyglycosides with cationic surfactants of the quaternized fatty acid triethanolamine ester salt type, so-called “esterquats”,are the subject of International patent application WO 94/06899 (Henkel).Mixtures of alkyl polyglycosides and esterquats with oils and protein hydrolyzates are protected in DE-C2 4305726 and WO 95105802 (Henkel). Cationic polymers are a particularly important ingredient for the production of hair-care and hair-treatment formulations. Very broad mixtures containing

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219

alkyl polyglycosides and cationic polymers are protected in European patent EP-B1 0337354 (Kao)to which there is an equivalent in the USA. In the course of the examination proceedings, the patent application was limited to the extent that the presence of saponins in the formulations was excluded although this hardly affected the scope of the patent. In view of the pre-published prior art, however, serious doubts have been expressed about the legal validity of this patent which is at present involved in opposition proceedings. The combination of selected cationic polymers with alkyl polyglycosides is claimed in European patent application El'-A 1 0603078 (L'Oreal). Liquid cleaning compositions containing mixtures of alkyl polygly cosides and betaines are known from JP-A2 H21187499 (Mitsubishi). Similar mixtures are also mentioned in International patent application WO 95104592 (SEPPIC). Surfactant concentrates containing alkyl polyglycosides, betaines and optionally sulfosuccinates are claimed in International patent applications WO 96/ 10558 and WO 96110622 (Henkel).

2.4 Mixtures of alkyl polyglycosides with cosmetic ingredients

EP-B1 0398177 (Kao) is of particular importance for the production of certain hair shampoos. This patent, which has been opposed, relates to mixtures of alkyl polyglycosides with soluble silicones. However, the amino-modified silicones of the Amodimethicone type had tobe excluded in the course of the examination proceedings. Subsequently,German patent DE-C2 4229922, which protects mixtures of alkyl polyglycosides, silicones and quats, was also granted. The use of alkyl polyglycosides as an emulsifier for polysiloxanes is the subject of European patent EP-B1 0418479 (Huls). L'Oreal has filed two applications on mixtures of alkyl polyglycosides with silicones: European patent EP-B 1 0557399, which is involved in opposition proceedings, is so to speak the complement to Kao's patent EP-B 1 0398177 which claims water-insoluble silicones together with alkyl polyglycosides. Finally, application EP-A 1 0643961 relates to mixtures of alkyl polyglycosides with special polysiloxanes. Originally, combinations of alkyl polyglycosides with antibacterial agents were very broadly claimed in application EP-A2 0422508 (Kao). Ultimately, however, a patent was only granted on a combination with anti-dandruff agents. Combinations of alkyl polyglycosides with pearlescent waxes and glycerol are protected in European patents El'-B1 0376083 and EP-B1 0570398 (Henkel). Later International patent application WO 95/13863 (SEPPIC)also claims pearlescent concentrates based on alkyl polyglycosides. Finally, a combination of alkyl polyglycosides with pearlescent waxes and fatty alcohol sulfates is also the subject of International patent application WO 95/03782 (ICI).

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Bernd Fabry

The use of long-chain (C,) alkyl polyglycosides with fatty alcohols as emulsifiers is claimed in European patent EP-Bl 0553241 (SEPPIC).However, the emulsifyingproperties of alkyl polyglycosides had already been reported in Articles by Hughes and Putnik 1103. In addition, emulsions containing alkyl polyglycosides, polyols and oils, in which fatty alcohols may be present as consistency regulators, are known from an earlier published Japanese application in the name of Shiseido [ 111. Finally, US patent 3,547,828 (Rohm & Haas) discloses mixtures of long-chain alkyl polyglycosides and fatty alcohols which have particularly favourable emulsifying properties. Accordingly, the SEPPIC patent, which has been opposed for lacking an inventive step. Henkel filed a patent application on combinations of alkyl polyglycosides and fatty alcohols with monoglycerides (EP-B1 0554292). The addition of the third component improves the stability of the emulsions in storage. In addition, there are several German utility models in the name of Henkel KGaA which relate to mixtures of alkyl polyglycosides and fatty alcohols in selected quantity ratios and to ternary mixtures with selected surfactants. Finally, German patent applicationDE-A1 19533539 relates to emulsifier concentrates containing alkyl polyglycosides and polyglycerol poly-12-hydroxystearateswhich are liquid at room temperature. Other interesting patentdpatent applications in the cosmetics field include the following: - DE-A1 4107313 (Goldwell, not yet granted): use of alkyl polyglycosides in permanent wave sets - DE-Cl 4301994 (Wella, granted): hair and body shampoos containing fatty alcohol ether sulfates, sulfosuccinates, alkyl polyglycosides and nitrogenfree thickeners - EP-A1 502161 (Unilever,not yet granted):cosmetic formulations containing alkyl polyglycosides, waxes and optionally thickeners - EP-B1 0531943 (Kao, granted): tinting shampoos containing substantive dyes, alkyl polyglycosides, anionic surfactants and amine oxides - EP-A1 0538762 (Kao, not yet granted): hair-care formulations containing cationic surfactants, oils and alkyl polyglycosides - EP-Bl 0589407 (Kao, granted): liquid body shampoos containing anionic surfactants and defined quantities of triglycerol and, optionally, alkyl polyglycosides - EP-A1 0617954 (L'Oreal,not yet granted): cosmetic formulations containing alkyl polyglycosides and special copolymers based on maleic anhydride/ vinyl ether mixtures - WO 95/28143 (Henkel, not yet granted): mixtures of alkyl polyglycosides and lecithins.

22 1

Patent Situation in the Field of Alkyl Polyglycosides

3. Alkyl polyglycoside derivatives

The more alkyl polyglycosides emerge from the shadow of speciality products and acquire significance as chemical raw materials, the greater the interest in derivatives of this class of surfactants will be. The primary hydroxyl group above all is available as a centre for a chemical reaction. An overview of derivatization possibilities is given in Figure 5 (see also Chapter 8). Esters of alkyl polyglycosides, particularly methyl glucosides, with longchain fatty acids have often been described. The nonionic derivatives also include the alkylene oxide adducts although they do have surprising weaknesses in their biological degradability. By contrast, particularly low-foaming derivatives are alkyl polyglycoside mixed ethers which are obtained by the Williamson synthesis, i. e. by the base-catalyzed reaction of alkyl polyglycosides with butyl or benzyl chloride [121. According to International patent application WO 93/ 20089 (Henkel), a new group of nonionic surfactants is obtained by transesterification of dialkyl carbonates with alkyl polyglycosides. The end capping of alkyl polyglycosides by reaction of the primary hydroxyl groups with dimethyl sulfate is known from International patent application WO 93/21 197 (BASF). The esterification of methyl glucosides is covered by a number of patentdpatent applications in the name of Grillo [131. Finally, esters of alkyl

0-C-OR

Esters

Ethoxyiates

Sulfates

Ethers

Carbonates

t

t

t

T

t

i O(CH2)&OOX

Ethercarboxylates

I

I

1

OH I

Alkyl polyglycoside

Figure 5. Derivatives of alkyl polyglycosides

Quat. arnrn. cornp.

222

Bernd Fabry

polyglycosides with citric or tartaric acid are claimed in European patent EP-B1 0258814 (Auschem). Finally, silicone-modified alkyl polyglycosides are disclosed in European patent application EP-A1 0612759 of Wacker Chemie. Among the anionic derivatives, sulfation products above all are in the foreground. According to European patent application EP-A1 0326673 (Huls),the direct reaction of alkyl polyglycosides with sulfating agents, such as sulfur trioxide or chlorosulfonic acid, is normally only possible in a solvent and, because of this, is of hardly any interest for industrial application. An alternative is offered in European patent EP-BI 0511811 (Henkel),according to which alkyl polyglycoside/fatty alcohol mixtures accumulatingas intermediate products in the synthesis of alkyl polyglycosides are co-sulfated. The fatty alcohol acts as solvent and is converted into the alkyl sulfate. Finally, reference is made to alkyl polyglycoside sulfosuccinates1141, alkyl polyglycoside ether carboxylic acids [151 and alkyl polyglycoside isethionates [161, of which the production and use are protected, for example, by patent applications in the name of Kao, Rewo, BASF and Henkel. 4. Conclusions

The chemist concerned with patent law is repeatedly confronted by the question of teaching with respect to technical procedure. What conclusions can the product developer draw from the extremely complex patent situation? Are there any prospects at all of using alkyl polyglycosides without infringing a number of patents which are involved in examination or opposition proceedings or which have been validly granted? The answer to this question is a definite “yes”.Nowadays, the use of alkyl polyglycosides involves as much or as little risk from the point of view of patent law as the use of other surfactant commodities. It certainly presupposes the opportunity to be able to resort to careful documentation of the prior art. As for the rest, there are certain basic guidelines which may be applied: 1. The production of alkyl polyglycosides, for example, is largely in the public domain. Accordingly, a product of average quality may readily be produced without having to resort to protected technology. However, licences will have to be acquired for the development of high-quality products, for example using certain catalysts or a thin-layer evaporator for removing residual alcohol. 2. The use of short-chain alkyl polyglycosides, for example based on C,,,, fatty alcohols, is largely in the public domain. The same also applies to the combination of alkyl polyglycosides with conventional nonionic and cationic surfactants. The use of long-chain (C,,,,,) alkyl polyglycosides together with typical anionic surfactants for cosmetic applications is also largely unprotected and free state of the art.

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3. A number of documents represent unexamined patent applications and do not progress beyond that stage. Since, nevertheless, they can so to speak disconcert potential competitors, careful evaluation is absolutely essential. Finally, it is pointed out that, in 1993, Henkel KGaA concluded a worldwide licence agreement on alkyl polyglycosides with the Procter & Gamble Co. Through the amalgamation of those alkyl polyglycoside patent portfolios which are the most important not only in terms of the number of patents1applications listed therein, Henkel customers have been provided with a broad range of formulation possibilities which are validated in patent law. Thus, most typical formulations in the field of liquid laundry detergents, manual dishwashing detergents and many cosmetic products can be produced under the protection of these patent portfolios. This freedom to formulate without infringing is further broadened by licence agreements which Henkel KGaA have concluded in recent years with Kao Corp. and with Hiils AG. However, there is always an exception to the rule: whenever special problems arise, the opinion of a competent partner on the patent position should definitely be obtained. References

1. H. R. Wagner, Eurocosmetic 5 (1994) 32 B. Fabry, M. Philipp, J. E. Drach, HAPPI, August 94 (1994) 11 2. WO 90107516, Henkel(1988) 3. WO 92102742, Henkel(1990) 4. WO 93110132, Henkel (1991) 5. DE-A1 4215558, Henkel (1992) 6. DE-A1 432183, Henkel (1993) EP-A1 0615974, Akzo (1993) 7. WO 93/11143, Henkel (1991) 8. EP-A1 0513813, Henkel (1991) 9. G. Proserpio, G. Vianello, Rivista Ital. 56 (1974) 567 10. F. A. Hughes, B. W. Lew, J. Am. Oil. Chem. SOC.47 (1970)162 C. F. Putnik, N. F. Borys, SoapKosmKhem. Spec., June 86 (1986)34 11. JP-A 891203036, Shiseido (1989) 12. EP-A1 0364852, BASF (1988) WO 93/06115, Henkel (1991) 13. DE-A1 4015733, Grillo (1990) DE-C2 4313117, Grillo (1993) 14. EP-A1 0454321, Kao (1990) EP-A1 0507004, Rewo (1991) 15. EP-A1 0457155, BASF (1990) 16. DE-A1 4315810, Henkel (1993)

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

14. Surfactants in Consumer Products and Raw Material Situation-A Brief Survey Gunter Kreienfeld and Gerhard Stoll 1. Historical review [ll

Soap is the oldest synthetic washing and cleaning agent. As long ago as 2500 BC its manufacture was described by the Sumerians who also referred to its use as a washing and cleaning agent. Over the four and a half thousand years which have passed since then, it has undergone constant improvement through the use of suitable animal and vegetable oils and fats and the addition of perfume oils. In the second half of the 18th century, soap developed from an expensive luxury article into an inexpensive mass produced product within the means of most social classes. This was made possible by pioneering work in research and technology. Particularly worth mentioning in this regard are: - Chevreul’s findings on the structure of oils and fats - Leblanc’s work on the development of technology for the large-scale manufacture of soda. With increasing experience in the exploitation and treatment of oils and fats, such as extraction, splitting and hardening, soap manufacture developed into a large-scale industry in the 18th und 19th centuries. Depending on the type of application, there was a choice between bar soap, soft soap und powdered soap. Powdered soap in particular became very popular as a detergent. The use of additives such as soda and water glass meant that its performance could be increased. In Germany a new trend in detergents was started by Henkel with the introduction of Persil, the first “automatic”washing powder, onto the market in 1907. With the increasing importance of synthetic fibres (cellulose, acetate, etc.) and wool besides new textile dyes, the demands made of detergents became more stringent. The limitations of soap as a high-performance detergent became obvious (alkalinity, sensitivity to hard water). The change in the market situation called for surfactants with special property profiles. This was the challenge that faced chemists at the beginning of this century. In 1917, the chemist Fritz Giinther of BASF in Ludwigshafen achieved success in the alkylation and sulfonation of naphthalene. This synthesis of highfoaming substances with good wetting behaviour is generally considered to be the first attempt to produce a soap substitute. However, the hoped-for discovery of a satisfactory soap substitute did not materialize because the short chain alkylnaphthalene sulfonates did not have any distinct detergent properties.

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Giinter Kreienfeld and Gerhard Stoll

In 1928,H. Bertsch and colleagues, working at H. Th. Bohme AG in Chemexperiments. By sulfating this raw material they succeeded in developing the first modern synthetic washingactive substance. The next step was economic availability of the necessary raw material fatty alcohol. A fruitful cooperation program was developed between H. Th. Bohme AG and Deutsche Hydrierwerke AG, Rodleben. Both companies were to be taken over by Henkel at a later date. At the Deutsche Hydrierwerke, W. Schrauth was in charge of developing an economic process for manufacturing fatty alcohols from renewable raw materials. He succeeded in converting fatty acid esters into fatty alcohols by catalytic reduction with hydrogen under high pressure. This created the opportunity to market fatty alcohol sulfates at reasonable cost. The first detergents formulated with fatty alcohol sulfates were brought onto the market by Henkel in Germany in 1932 (FEWA@)and by Procter & Gamble in the USA in 1933 (Dreft@). This fatty alcohol based surfactant was soon followed by further products such as fatty acid condensation products (Igepone@types) and-in 1930-the first polyglycol ether of fatty alcohols (Athoxal@types), fatty acids and fatty amines. During this period, Henkel, Imhausen GmbH Witten and IG-Farbenindustrie collaborated with one another to produce the first alcohol ether sulfates (SulfoxaP types). It was not until many years later that alcohol ether sulfates assumed their pre-eminent position among fatty alcohol derivatives as washing-active substances, particularly for application in shampoos, foam baths and dishwashing liquids. Among the synthetic surfactants, alkylbenzene sulfonates occupy a leading position in regard to volume requirements. This group of surfactants was first synthesized by the former IG-Farbenindustrie AG und was subsequently developed to commercial maturity, in particular by National Aniline AG, New York. By the 1950s, the replacement of soap in detergent formulations by other surfactants was virtually complete in Europe and the USA. The principal substitute was tetrapropylenebenzene sulfonate which satisfied over 60O!o of surfactant demand in the western world at that time. Owing to its unfavourable biological degradability, tetrapropylenebenzene sulfonate was replaced by the more readily degradable linear alkylbenzene sulfonate in Europe, USA and Japan in the 1960s. A study of the developments in the surfactant sector over the years that followed shows that the introduction onto the market of innovative products with high potential demand goes back more than 20 years. The last group of nitz used fatty alcohol as feedstock for their

Surfactantsin Consumer Products and Raw Material Situation-A Brief Survey

227

surfactants to find significant market acceptance in Europe were the alkane sulfonates. For example, linear alkylbenzene sulfonate in dishwashing liquids was partly replaced by this surfactant. However, the origins of this surfactant class can be traced back to the 1930s. Even then and on into the 1940s, they were an ingredient of many detergents under the trade name of “Mersolate”’. Accordingly, their later and continuing success has to be seen more as a revival. Another successful class of surfactants are the distearyl dimethyl ammonium chlorides which have been on the market for 30 years now. However, their days would appear to be numbered because of their unsatisfactory ecological properties. Accordingly, it is clear that considerable difficulties are involved in the development of new surfactants which can be industrially used on a wide scale and, besides a favourable cost/eff ectiveness ratio, also meet the stringent ecological demands of our time. 2. Present situation [21

Having reviewed briefly the historical development of detergents in general and washing raw materials (surfactants) in particular, consideration is now given to the present situation. Nowadays the generic term surfactants applies to a host of surface active products, however, approx. 800!0of total demand is covered by a group of less than 10 types, the main ones being alkylbenzene sulfonate (LABS),fatty alcohol sulfate (FAS),fatty alcohol ether sulfate (FAES),fatty alcohol ethoxylate (FAEO) and the surfactant which still has the highest consumption worldwide, namely soap. It is significant that these types are used in almost all major market segments; in consumer products (detergents and cosmetics) and for industrial and institutional applications (food, textile and leather, plastics, paints, mining and oilfield chemicals). It is not the aim of this contribution to describe the development of the individual markets or demand forecasts for selected surfactants and provide various arguments to substantiate these findings. History has already shown that price and performance are the criteria for the success of any product. Apart from these two factors, it is ecology or the evaluation of a product with relevance to the environment which will gain in importance. Taking this into account, the future prospects for certain surfactants are outlined below. - Soap In 1994 approximately 5 million t of soap bars were used worldwide for washing clothes, whereby the highest demand is in Asia and South America. Including an estimated 2.5 million t of toilet soap, total consumption amounted to 7.5 million t.

228

Gunter Kreienfeld and Gerhard Stoll

- LABS,BABS Linear alkylbenzene sulfonate is currently the workhorse of the detergent industry. In some countries, particularly in the Asia/Pacific region and Latin America, the ecologically questionable branched alkylbenzene sulfonate is still used. However, due to its limited biodegradability it is only a matter of time before it is substituted by the already dominant linear type. - FAS Fatty alcohol sulfate will undoubtedly increase in importance. The ever increasing market share of the so-called compacts, i. e. detergent granules with a high washing active substance content, is a development which favours the crystalline behaviour of fatty alcohol sulfate as it leads to improved flowability of the end product. Combinations of fatty alcohol sulfate with a performance boosting cosurfactant such as alkyl polyglycoside in dishwashing liquid formulations are expected to prevail on the market. In the Asian region particularly the increased substitution of traditional soap with synthetic s&ac&nts offering higher performance can be expected. - FAES Dishwashing liquids and the increasing use of shampoos and surfactantbased bath preparations-mainly in Asia-are the major contributory factors in the annual growth rate of 4.5 % for fatty alcohol ether sulfates. - FAEO One of the major reasons for an annual growth rate of 4 % for fatty alcohol ethoxylates is the substitution of ecologically questionable alkyl phenol ethoxylates which are still being used in some parts of the world. - Carbohydrate-based surfactants As a nonionic, alkyl polyglycoside is the ideal co-surfactant with many of the advantages already mentioned in the previous chapters. The capacities of 60,000 t available at present will increase visibly by the year 2000 in order to meet increasing demand both in the detergent and cleaner market and in the cosmetics and toiletries field. Fatty acid glucamide is another sugar based surfactant. It is composed of glucose, methylamine and fatty acid methyl ester. At present, this surfactant is used only in detergents and cleaners 131. 3. Basic oleochemicals

Surfactants are the heart of the detergent formulation. They can be manufactured both petrochemically and by using renewable natural raw materials. The oleochemicals essential for the production of surfactants are available in abundance-the industry struggles with overcapacities (Figure 1).

Surfactantsin Consumer Products and Raw Material Situation-A Brief Survey n o 3

ti

3000

1993

229 I1996

1

2000

1000

Figure 1. Capacities of basic oleochemicals

Western Europe

North, South and Central America

Asia

- Fatty alcohol

This is especially true for fatty alcohols where the ratio between natural and synthetic alcohols has shifted to 40:GO in favour of the natural fatty alcohol. A major influencing factor has been the efforts by Asian countries, such as Malaysia and Indonesia, to start up their own processing facilities in order to utilize the raw materials growing in their own backyard. The world capacity for fatty alcohols is 1.6 million t whereas demand is only 1.3 million t (Figure 2). - Fatty acid Natural oils and fats are historically the basis for the manufacture of fatty acids. Although their production using petrochemicals is possible, economic

Capacity

[ l o 3 ti

4000 1

IUtilization

3000 .

2000 1000 -

Figure 2. Worldwide capacity and utilization of fatty acids and fatty alcohols

Fatty acids

Fatty alcohols

Gunter Kreienfeld and Gerhard Stoll

230

considerations are usually prohibitive. Of the approximately 3.7 million t of capacity available worldwide, only 65 O/o is being taken up (Figure 2). - Glycerine In oleochemistry, glycerine has always been a valuable by-product obtained from splitting oils and fats (triglycerides)and will remain so in future. Production and demand have been evenly balanced for decades. The strategic decision to substitute diesel oil with government subsidized biodiesel has resulted in a surplus of glycerine and this will continue to be the case as long as it remains policy to support this business. Manufacturers of synthetic glycerine are gradually pulling out of the market because it is more profitable for them to manufacture intermediate products rather than glycerine. Substitution products of glycerine, such as propylene glycol, ethylene glycol or sorbitol are also vulnerable to price and quantity fluctuation so that these products also have an influence on potential sales of glycerine. With all these unknown factors, it is difficult to make any forecasts for glycerine. Given historical growth, supply and demand should be equal by the year 2000. Should all the speculation prove correct, supply will outweigh demand by 90,000-200,000t. Given today’s capacity, that would be over 20010 (Figure 3). - Fatty acid methyl ester Fatty acid methyl ester is used almost exclusively for the production of natural fatty alcohols. Again, capacities were built for an expected demand that did not keep the pace. The present demand of 0.8 million t contrasts with a capacity of 1.2 million t. New sales areas outside the fatty alcohol feedstock are nowhere in evidence. [lo3 tl

400 300

1993

I1996

1

200 100

Western Europe

North, South and Central America

Figure 3. Capacity of glycerine

Asia

Surfactants in Consumer Products and Raw Material Situation-A Brief Survey

231

4. Raw materials 4.1 Oils and fats

During 1994 approx. 90 million t of natural oils and fats were obtained, an increase of 3.7 010 over 1993. Of these 90 million t, approx. 70 million t were vegetable based (Figure 4). Soybean was the most important oil, followed by palm oil and rapeseed oil. The oils used primarily for oleochemical processes were coconut and palm kernel oil for the midcut C ~ 1 and 4 palm oil and tallow for the longcut C16118. Palm oil has experienced the highest growth rate over the last few years. It has increased by 15 010 in volume by virtue of better cultivation processes and increased acreage, especially in Indonesia. - Consumption 80% of the processed oils and fats are used in human nutrition, 6010 in animal feeds and only the remaining 14% in chemical processes. 77010 are of vegetable origin and 23 Oo/ are animal based oils and fats (Figure 5). - Price The price development of oils and fats can be illustrated with reference to coconut oil. Periodically, its price has fluctuated enormously over the last 2 5 years. The highest average annual price was in 1984 when coconut oil cost DM 331 per 100 kg, but that was followed by a dramatic drop to DM 67 per 100 kg only two years later (Figure 6).

Total: 69 million t

20 15

10

5

Soybean

Palm oil

Sunflower oil

Rapeseed oil

Figure 4. Worldwide production of vegetable oils

Laurics

Others

232

Giinter Kreienfeld and Gerhard Stoll Animal feed

Animal oils and fats

Production (89.2)

Chemistry

Consumption

Figure 5. Production and consumption of vegetable and animal oils and fats (worldwide, million t)

4.2 Crude oil

The output in 1994 was approx. 3 billion t. Saudi Arabia and the USA were the leading producers with approx. 400 million t each, followed by the states of the former USSR. The total output of Western Europe was 284 million t, of which 90 Yo was produced in the UK and Norway. - Reserves The crude oil reserves of oil fields currently on stream and of future fields which current technology can be expected to open up at reasonable costs are estimated at 136 billion t. That would give us enough crude oil for the next 45 years; when the non-conventional sources of oil shale and tar are added, there should be sufficient reserves for several hundred years. 77 010 of all reserves are concentrated in the OPEC countries. Price [DM/100 kgl 350

300

250 200

150 100 50 1973

1980

Figure 6. Fluctuation of coconut oil price

1990 1994

Surfactantsin Consumer Products and Raw Material Situation-A Brief Survey

233

- Projection 2000

A strong influence on demand for crude oil will be the development in the automobile market in countries outside the established industrialized nations. If all forecasts and estimates for a country like China were to materialize, the result would be a drastic increase in demand for crude oil. According to a forecast undertaken by Shell, gasoline consumption is expected to rise to 5 billion t a year. - Price Abundant supplies coupled with a constant demand led to a drop in prices in 1994. The average price was $15,5 per barrel (158.99 liters) instead of the OPEC target of $ 2 1 per barrel. Crude oil prices have also experienced rollercoaster variations similar to natural oils and fats. The all-time high was $ 3 4 in 1982/83 whereas, by 1986, the price had fallen to as low as $ 8 per barrel. 5. Outlook

The market for detergents and cosmetics is in constant change, thus offering excellent opportunities for surfactants, especially when not only the washing performance is increased but also the ecological aspects are improved. Alkyl polyglycosides are a good example for a successful development in this direction. Today, alkyl polyglycosides are used in a large number of cosmetic preparations and household products worldwide. Due to their exceptional properties, alkyl polyglycosides represent a trend setting innovation; a statement being endorsed more and more by notable companies all over the world. Henkel has set the quality standard in the market, other companies will follow, possibly with other alternatives from sugar chemistry as well. References

1. H. Verbeek in Surfactants in Consumer Products-Theory, Technology and Application (J. Falbe, ed.), Springer Verlag, Heidelberg, 1987, p. 1 Deutsche Hydrierwerke (DEHYDAG),Stationen ihrer Geschichte, Schriften des Werksarchivs der Henkel KGaA, Diisseldorf, 1981 2. P. Hovelmann, B. Brackmann, 21st World Congress and Exhibition of the International Society for Fat Research (ISF),The Hague, 1995 P. Hovelmann in Proceedings of the 3rd World Conference on Detergents: Global Perspectives(A.Cahn, ed.),AOCS Press, Champaign, Ill., 1994, p. 117 W. J. B. Vogel in Proceedings of the 3rd World Conference on Detergents: Global Perspectives(A.Cahn, ed.),AOCS Press, Champaign, Ill., 1994, p. 123 3. P. Jiirges, A. Turowski in Perspektiven nachwachsender Rohstoffe in der Chemie (H.Eierdanz, ed.), VCH Verlagsgesellschaft,Weinheim, 1996, p. 61

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH VerlagsgesellschaftmbH,1997

Contributors

Dr. Hans Andree Dr. Walter Aulmann Dr. Rainer Eskuchen Dr. Bernd Fabry Dr. Thomas Forster Dr. Roger Garst* Dr. Walter Guhl Dr. Hermann Hensen Dr. J. Frederick Hessel** Dr. Karlheinz Hill Dr. Frank Hirsinger Bettina Jackwerth Dr. Jorg Kahre Dr. Hans-Udo Krachter Gunter Kreienfeld Dr. Peter Krings Dr. Wolfgang Matthies Dr. Georg Meine

99 151 9 211 39 131 177 71 99 1 191 169 71 169 225 99

169 99

Dr. Birgit Middelhauve 99 Dr. Dieter Nickel 39,139 Dr. Michael Nitsche 9 Dr. Oliver Rhode 139 Dr. Wolfgang von Rybinski 39 Barry A. Salka*** 71 Dr. Judith Scherler 23 Dr. Karl Schmid 99 Dr. Michael Schmitt 23 Dr. Frank Roland Schroder 177 Dr. Josef Steber 177 Dr. Norbert Stelter 177 Dr. Walter Sterzel 151 Dr. Gerhard Stoll t 225 Dr. Holger Tesmann 71 Jan R. Varvil* 23 Dr. Heinrich Waldhoff 23 Dr. Manfred Weuthen 139

Henkel KGaA, HenkelstraBe 67, D-40191 Diisseldorf * Henkel Corp., 4900 Este Avenue, Cincinnati, Ohio 45232-1491, USA ** Henkel Corp., 300 Brookside Avenue, Ambler, PA 19002-3498, USA *** Henkel Corp., 1301 Jefferson Street, Hoboken, NJ 07030, USA

Alkyl Polyglycosides Technology,Properties and Applications Edited by K.HiII,W.vonRybinski,G.Stoll 0 VCH Verlagsgesellschaft mbH,1997

Index

acetochlorhydrose 3 acidic catalysts 16, 213 adsorption 63 AE,see alcohol ethoxylates A E S , see alkyl ether sulfates agricultural applications 131 - adjuvant 131 - regulatory status 132 Agrimu1"PG 20, 131 alcohol ethoxylate 43, 65, 100, 191 algae 184 alkane sulfonates, see secondary alkane sulfonates alkylbenzene sulfonates 170, 227, 228 - branched 228 - linear 100, 104, 116, 119, 170, 191, 226,227,228 alkyl ether sulfates 73, 110, 191 alkyl monoglycosides 11,23,26,27, 31, 32, 51 alkylnaphthalene sulfonates 225 alkyl oligoglycosides 11, 23, 25 alkyl phenol ethoxylates 116, 132, 135, 136, 228 alkyl polyglycol ethers 43, 45, 65, 66, 106 amphoteric surfactants, combination with alkyl polyglycoside 87, 218 analysis 23 - gas chromatography 24,28,29,37 - - high temperature 24 - high performance liquid chromatography 27, 36 - in detergents 34, 35 - in environmental matrices 35 - in formulated products 30

- thin layer chromatography 30 anionic surfactants, combination with alkyl polyglycoside 48,52, 76,77, 100, 215 anomers 3, 4, 24, 27 antibacterical agents, boosting effect 87 antimicrobial stabilization 215 APG@surfactants 2 , 2 0 aryl glucosides 3 atmospheric emissions 199 average degree of polymerization, see degree of polymerization

BABS, see alkylbenzene sulfonates, branched bacteria 185 betaine 87 BIAS, see bismuth-active substance biodegradability 177 - anaerobic 182 - half-life time 188 - primary 178, 181 - ready 75, 76, 177 - ultimate 178 biological oxygen demand 180,203 biomass energy 199,202 bismuth-active substance 178 bleaching 17, 19,214 BOD, see biological oxygen demand Buehler test 160 butanol route 12, 13, 17,213 butyl chloride 143 butyl glycosides 12, 13, 17, 193

C A M test, see hens' egg test carbon black 64, 65

238 carbon dioxide 199 - fossil 203 - non-fossil 203 carbon monoxide 199,203 catalyst 13, 16, 18,213 cationic surfactants,combination with alkyl polyglycoside 87, 218 chemical oxygen demand 180,203 cleaners 117 - all-purpose cleaners 118 - bathroom cleaners 120 - concentrated 118 - dermatological behavior 102 - - hand immersion test 108, 109 - - mucous membrane 105 - floor cleaners 118 - hard surface cleaners 99 - manual diswashing detergents 99 - polishability 123 - toilet cleaners 121 - window cleaners 123 cloud point 46, 49, 65, 66 cmc, see critical micelle concentration CNO, see coconut oil coconut 197,202 - husked 197, 198 - oil 10, 193, 197, 198, 199 COD, see chemical oxygen demand compatibilizers 134 copra 198,202,209 corn 10, 193 -growing 194 - starch 10, 198 cosmetic ingredients 219,220 cosmetics 71, 72 - cleansing 72, 79 - concentrate 76 - emulsion 61, 82 - foaming 78, 79 - formulation techniques 61, 77, 87 - hair, see hair care

Index

- raw materials 76 co-solvents 58 critical micelle concentration 51, 144 crude oil 198, 232 cytogenetic test 162

daphniae 184, 185 DE, see dextrose equivalent decane 54, 55, 145, 147 degree of glycosidation 23, see also degree of polymerization degree of polymerization 1, 11, 14, 16, 18, 20,26, 43, 72, 171, 216 densitometry 32 derivatives of alkyl polyglycosides - benzyl ethers 221 - butyl ethers 143,221 - carbonates 141,221 - esters 139,221 - ether carboxylic acids 139,222 - glycerol ethers 140 - isethionates 139,222 - methyl ethers 221 - silicone modified 221 - sulfates 139,222 - sulfosuccinates 139, 222 - with citric acid 221 - with tartaric acid 221 dermal irritation 154, 155, 169 dermatological properties 72, 102, 107, 169 - arm flex wash test 73,75, 172, 173 - Duhring Chamber Test 73 - of detergents 102, 107, 130 - open application 169 - patch test 169, 170, 171 - skin compatibility 169 detergents 99 - conventional products 105, 111 - I&I dishwashing products 113 - liquid detergents 126

239

Index

- manual dishwashing detergents 99, 104, 111, 115 - pastes 114 - powder detergents 128 dextrose 10, 11, 14, 15 dextrose equivalent 12, 13 diethyl carbonate 141 “diglucose” 4 direct synthesis 12, 15, 18, 193, 213 dissolved organic carbon, see DOC distearyl dimethyl ammonium chloride 227 distillation 16, 17, 19, 21, 214 - multistage 16

DOC 179, 180 DP, see degree of polymerization EC 184, 188 Ecosol group 191 ecotoxicity 184 -acute 184 - aquatic 184, 185 - biocenotic 186 - chronic 184 - terrestrial 184 effect concentration, see EC EMR, see energy of material resource emulsions 57, 82 - concentrated 84, 134 - microemulsions 57, 83 -O/W

-

W/O

59,83 59, 83

energy of material resource 198,200 - fossil 192 - renewable 192 environmental concentrations 187 environmental risk assessment 187 environmental stress cracking 120 epidermis, swelling 74 epidermis, transepidermal water loss 74, 91

etherification 15, 140, 143 exposure assessment 187 eye irritation 156 FAEO, see fatty alcohol ethoxylate FAES, see fatty alcohol ether sulfate FAS, see fatty alcohol sulfate fatty acid 229 - glucamide 117,228 - methyl ester 230 fattyalcohol 9, 14, 15, 16, 18, 19,47, 86,226,229,230 - ether sulfate 61,79, 100, 170, 227, 228 - ethoxylate 39, 100, 228 - removal 16, 214 - residual 24, 28 - sulfate 48, 53, 87, 100, 172, 191, 226,227,228 - synthetic 9

feedstock energy, see energy of material resource FFB, see fresh fruit bunches filtration 14, 15, 19 Fischer synthesis 1, 3, 4, 9 Flory distribution 11, 27 foaming 78, 100, 107, 148 - markers 133 - perforated disc method 78 - Ross Miles method 131 - stress stability of foam test 107 - whipped foam test 104 fresh fruit bunches 197, 198 furanosides 4, 24 glucamides 117, 228 Glucopon@ 20,99, 117 glucopyranosides 25 - ethyl 4 - decyl 25, 26 - dodecyl 25,26

2 40

- octyl 25, 26 glucose 10, 12, 17, 19, 194 - monohydrate 10, 12, 17, 193 - production 194 - residual 29 -syrup 10, 12 glucoside, alkyl 1, 4 glucoside, ~ctyl-fi-D-[U-'~Cl-163 glucoside,[1-'4C1-hexadecyl-P-D- 163 glycerine 230 glycerol monooleate 61, 83 glycosyl fluorides 6 GMO, see glycerol monooleate haemolysis 158 hair care 80 -bounce 81 - conditioning 87 - curl retention 81, 82 - film-forming 81 - permanent-wave 80 - substantivity 81 hens' egg test 72, 90, 102, 158 herbicides 134 HET-CAM, see hens' egg test INCI-name 71 interfacial tension 54, 60,61, 83, 144, 145 isopropyl myristate 55 Kahlweit fish 58,61 K-fertilizer, see potassium fertilizer Koenigs-Knorr synthesis 3, 4 Krafftpoint 40

LABS, see alkylbenzene sulfonates, linear LAS, see alkylbenzene sulfonates, linear LC 184, 185

Index

LCA, see life cycle analysis lethal concentration, see LC licence agreements 223 life cycle analysis 191 limestone 195 - production 195 limit test 153 liquid crystals 39, 47, 48, 52 LOEC, see lowest observed concentration lowest observed concentration 187 magnesium oxide 16, 19 Magnusson-Kligman test 160 maltoside, [l-'4C1-dodecyl-P-D- 163 manual diswashing detergents 99 MES, see methyl ester sulfonate 170 metabolism 163 metabolite test 183 methyl ester sulfonate 170 methyl glucoside, esterification 221 micelles 50, 51 mutagenicity 161 naphthalene, sulfonation of 225 natural gas 198 N-fertilizer, see nitrogen fertilizer nitrogen fertilizer 196, 198 nitrogen oxides 199 NOAEC, see no observed adverse effect concentration NOAEL, see no observed adverse effect level NOEC, see no observed effect concentration nonionic surfactants, combination with alkyl polyglycosides 218 non-renewable energy 202 nonyl phenol ethoxylates 114, 132 no observed adverse effect concentration 164

Index

no observed adverse effect level 164 no observed effect concentration 185,187, 188 occlusive application 169 - application test 172 - substitution of standard surfactants 170 - use test 174 octyl dodecanol 55, 144, 146 oligomer distribution 11, 12,24,215 palm kernel oil 10, 193, 197, 204, 205 particulates 203 PEC, see predicted environmental concentration penetrators 133 personal care 71 pesticides 131 P-fertilizer, see phosphate fertilizer phase diagram 40,44,47,48,58,63, 83, 85 phase inversion temperature 57 phosphate fertilizer 196, 198 PKO, see palm kernel oil PlantacareR 20, 72, 76 PlantarenR 20, 72 plant capacity 2 plate test 101, 107 PNEC, see predicted no-effect concentration polydextrose 14, 19, 27 potassium fertilizer 196, 198 predicted environmental concentration 187 predicted no-effect concentration 185, 187 process energy 192, 200, 206 propyleneglycol 12 pyranosides 4, 24

24 1

QUAT, see quaternary ammonium compounds quaternary ammonium compounds 82, 87, 218 raw materials 9, 10, 231 RBC,see red blood cell test reaction pressure 15, 16 reaction temperature 15 red blood cell test 73, 158 repeated open application test 170 responsible care 151 rheology 49, 77 river biocenosis 186 river model system 186 ROAT, see repeated open application test Salmonella typhimurium reversion test 161 SAS, see secondary alkane sulfonates secondary alkane sulfonates 100, 104, 170, 191 sensitization 159, 175 sewage treatment plant model 178, 181 skin compatibility 73, 102, 107, 169 - patch test 102, 107, 170 - sensitization 159, 175 SLES, see sodium lauryl ether sulfate SML, see sorbitan monolaurate soap 225,227 sodium lauryl ether sulfate 73, 76, 82, 170 solid waste 203 sorbitan monolaurate 60, 83 spinning drop tensiometer 145 spreading agents 133 starch 10, 12, 13, 17, 194 storage stability 117, 128 - of enzymes 127, 128

2 42 sucrose fatty acid esters, combination with alkyl polyglycosides 218 sulfonic acids 16, 19,213 - alkylbenzene sulfonic acid 16 - para-toluene sulfonic acid 16 - sulfosuccinic acid 16 sulfur 198 sulfuric acid 16 sulfur oxides 203 surface tension 51, 144 suspoemulsions 134 synthesis 2, 9, 12, 14, 139, 213 - direct 12, 13, 15, 18 - enzymatic 2 - molar ratio 12, 16, 19 - selective 2, 6 tapahan dryers 198 tergotometer 112 tetrapropylenebenzene sulfonate 226 titanium dioxide, adsorption on 67 TOC 179 total organic carbon, see TOC toxicity -acute 152 - subchronic 163 toxicokinetics 163 transacetalization 10, 12, 13, 15, 17, 213 transport energy 192,200, 206

USEPA 132 vegetable oils 10, 231 viscosity 49, 77 waterborne emissions 202 water hazard class 189 wetting behavior 147, 148 WGK, see water hazard class

Index