Alkyl polyglycosides

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Example of an APG based on glucose (m = 1 to 5 and n = 11 to 15).

Alkyl polyglycosides (APGs) are used as surfactants . They are nonionic surfactants and belong to the group of sugar surfactants . They are used as a surface-active ingredient in detergents , dishwashing detergents and cleaning agents. Alkyl polyglycosides consist entirely of the renewable raw materials sugar , obtained from sugar cane and sugar beet, and fatty alcohols , obtained from palm oils . They are biodegradable and have low toxicity .

history

As early as 1931, the first patent on alkyl glucosides was registered in Germany , which allowed the use of alkyl glucosides as emulsion , cleaning and wetting agents for. B. describes in soaps . It was not until the 1970s that methods for the industrial production of APGs were developed. This finally enabled Rohm and Haas to launch the first industrially produced alkyl glucoside at the end of the 1970s . The APG was an octyl / decyl polyglucoside. However, this APG could only be used for a few purposes, as it a. is an insufficient surfactant .

In the 1980s, production shifted to longer-chain alkyl radicals, e.g. B. dodecyl / tetradecyl polyglycosides. APGs were also increasingly being manufactured for cosmetic products. The industrial large-scale production of alkyl polyglycosides was finally initiated in 1992: The Henkel Group opened a plant with an annual capacity of approx. 25,000 tons in Cincinnati (USA), and in 1995 also in Düsseldorf . Worldwide there are capacities of more than 80,000 tons of alkyl polyglycosides per year. For Germany, the annual production volume is given as 50,000 tons.

properties

Alkyl polyglycosides generally consist of a sugar component, for example glucose , and a long-chain alkyl radical. The sugar component acts as a hydrophilic component, the long-chain alkyl radical represents the hydrophobic group in the alkyl polyglucoside. Molecules that contain any glucoside sugar are called alkyl polyglycosides. Alkyl polyglucosides, on the other hand, are compounds with glucose as a sugar component.

In industrial production, AGPs are available as a mixture of alkyl glucosides of various alkyl chain lengths, the degree of polymerization of the sugar, anomers and isomers . The fatty alcohols usually have a chain length of 8 to 14 carbon atoms, longer chains such as bsp. C 16 lead to very hydrophobic products. These fatty alcohols are obtained from palm oils . The degree of polymerization of the sugar is between 1 (alkyl monoglucoside) and 5 (alkyl polyglucoside).

APGs are skin-friendly, non-toxic and easily biodegradable. In connection with other surfactants, they have a strong synergistic effect, so that 20 to 50% can be saved.

raw materials

For the production of alkyl polyglycosides, glucose from sugar or starch- supplying plants is used as well as vegetable oils such as palm kernel oil , in rare cases coconut as a supplier of the alkyl residue.

Manufacturing

Today's production of alkyl polyglycosides is based on Emil Fischer's synthesis instructions . Here, both glucose itself and polymers of glucose ( starch , glucose syrup ) are converted into acid-catalyzed reactions with fatty alcohols (e.g. dodecanol ) as the starting material . The acid serves as a catalyst; sulfuric acid , p -toluenesulfonic acid , alkylbenzenesulfonic acid or sulfosuccinic acid are usually used. The reaction time and the course of the reaction must be carefully controlled, especially since the synthesis is not stereospecific.

There are two methods of making AGPs. Either these are in a direct synthesis from glucose and z. B. Dodecyl poly / tetradecyl polyglucoside synthesized in one step. This happens at temperatures of 120 ° C and a pressure of 2,000 Pa. The result is a complex mixture of alkyl mono-, alkyl oligo- and alkyl polyglucosides. In addition, other by-products such as ethers or glucose polymers can also be detected in the reaction mixture.

Alternatively, APGs can also be prepared in two stages via a transacetylation , which is more difficult in terms of apparatus. First, the implementation takes place with a short-chain alcohol, e.g. B. butanol at about 115 ° C and normal pressure for glucose and 140 ° C and 400,000 Pa for starch as the starting raw material. In a second reaction, the short chain alkyl glucoside is treated with a long chain alcohol, e.g. B. dodecanol , transacetalized at temperatures of 120 ° C and a pressure of 2,000 Pa to a long-chain alkyl glucoside.

use

Alkyl polyglycosides are resistant to hydrolysis and, due to their HLB value of> 10, they have good dirt loosening and dirt carrying capacity. They are highly foaming and have no skin-irritating ingredients, which is why they are often used in dishwashing detergents for hand washing and combined with linear alkylbenzenesulfonates (LAS) and fatty alcohol sulfates (FAS). They are also used as additives in light detergents due to their properties.

In the cosmetics industry , alkyl polyglycosides are used as components of shampoos , hair conditioners , bath additives and skin cleansers. Strongly hydrophobic APGs with 16-C carbon chains are used as emulsifiers in cosmetics and foam inhibitors.

Large-scale use is mainly concentrated in the area of ​​cleaning agents in the food and brewery industries, where nonionic or anionic surfactants cannot be used due to their poor solubility and strong foam formation. Together with modified fatty amine ethoxylates , low-foaming or even foam-retarding cleaners based on sodium hydroxide solutions can be produced.

literature

Individual evidence

  1. ↑ H. Th. Böhme AG, DRP (Offenlegungsschrift) 593422 1931.
  2. ↑ a b c d e f Keyword Alkyl Polyglycosides In: Hans Zoebelein (Hrsg.): Dictionary of Renewable Resources. 2nd edition, Wiley-VCH, Weinheim and New York 1996, ISBN 3-527-30114-3 ; P. 92.
  3. ↑ Fachagentur Nachwachsende Rohstoffe (Ed.) 2006: Market Analysis of Renewable Raw Materials. Gülzow ( pdf, 16 MB ).
  4. ^ A b Günter Wagner: detergents - chemistry, environment, sustainability . 4th edition. John Wiley & Sons, Weinheim 2011, ISBN 978-3-527-64366-0 , pp. 47–48 ( limited preview in Google Book search).
  5. ^ Wittko Francke and Wolfgang Walter : Textbook of organic chemistry . S. Hirzel Verlag Stuttgart; 24. revised 2004 edition, ISBN 3-7776-1221-9 ; P. 472.