Sugar surfactants
Sugar surfactants are nonionic surfactants in which carbohydrates form the hydrophilic part of the surfactant molecule . Fatty alcohols or fatty acids act as hydrophobic components , which are chemically linked to the carbohydrates in different ways depending on the desired property of the surfactants. The carbohydrates used are sucrose , glucose and sorbitol for the production of sucrose esters , alkyl polyglycosides , N-methyl glucamides and sorbitan fatty acid esters .
raw materials
Only renewable raw materials are used for the industrial production of sugar surfactants . Like sucrose, carbohydrates are obtained from sugar beet or sugar cane , glucose from starch and sorbitol by reducing glucose. The fatty acids originate i. d. Usually from palm oil , in individual cases from coconut fat . The fatty alcohols can be produced by reducing the fatty acids .
general structure
Sugar surfactants consist of a polar, water-soluble head group and a non-polar, fat-soluble tail. They can be divided into ethers , esters , amines and amides based on the chemical bond between the sugar and the alkyl group . The HLB values of sugar surfactants depend on the degree of polymerization of the sugar as a polar group and the number and length of the alkyl chains. Molecules with multiple alkyl chains are very hydrophobic. If the head group is a disaccharide, the surfactant is more hydrophilic.
Types
Alkyl polyglycosides
→ Main article: alkyl polyglycosides
Alkyl polyglycosides are the most important class of sugar surfactants industrially. They are used in laundry detergents, dishwashing detergents and cleaning products.
Methyl glycoside esters and ethyl glycoside esters
Another group are fatty acid esters of methyl or ethyl glycosides. Compared to alkyl polyglycosides, they are somewhat more stable when used as a surfactant, but they are less water-soluble and serve as an emulsifier.
Sorbitan ester
→ Main article: Sorbitan fatty acid esters
Some sorbitan esters are approved as food additives in the EU. In addition, ethoxylated derivatives, the polysorbates, are also important as surfactants.
N -methyl glucamides
To synthesize N -methylglucamides, glucose is first reacted with methylamine under reducing conditions . This creates N -methylglucamine . In a further reaction step with fatty acid methyl esters, N-methylglucamide is formed. They are used in powder and liquid detergents as well as in hand dishwashing detergents.
Sucrose ester
Sucrose esters are obtained from sucrose and fatty acid methyl esters via transesterification . It formed Zuckerester . The usual representation leads to a complex mixture of one to fivefold esterified molecules. Therefore, industrial products are always a mixture. These mixtures are very hydrophobic and therefore have a limited range of applications. Increasing the proportion of monoesters by changing the reaction conditions is technically possible, but too expensive.
Sucrose esters are particularly mild on the skin and are used as emulsifiers in cosmetic products and in Asia also as additives to special detergents. Sucrose esters of fatty acids are approved as food additives ( E 473 ) and also serve as an emulsifier for preparations.
use
Sugar surfactants are environmentally friendly and generally show good skin tolerance. In contrast to other nonionic surfactants such as polyalkylene glycol ethers , their effect as an emulsifier is less sensitive to temperature, which is the result of stronger hydrogen bonds between the hydroxyl groups of the sugar and water molecules. Because of these properties, sugar surfactants are used as components of detergents, cosmetics and as food additives. Sorbitan esters are used as auxiliaries for textiles and leather and as food emulsifiers. Sucrose esters serve as food and cosmetic emulsifiers. Alkyl polyglycosides are used in the production of detergents, cosmetics and hand dishwashing detergents. N -methyl glucamides are part of liquid and powder detergents as well as hand dishwashing detergents.
literature
- K. Hill, O. Rhode: sugar-based surfactants for consumer products and technical applications. In: fat / lipid. 101, No. 1, ISSN 0931-5985 , 1999, pp. 25-33.
- C. Stubenrauch: sugar surfactants- aggregation, interfacial, and adsorption phenomena. In: Current opinion in colloid and interface science. 6, No. 2, 2001, pp. 160-170 ( doi : 10.1016 / S1359-0294 (01) 00080-2 ).