Isethionate

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Isethionates are esters of long-chain (C 8 -C 18 ) aliphatic carboxylic acids with isethionic acid or its salts, such as. B. ammonium or sodium isethionate and are also referred to as acyl isethionate or acyloxyethane sulfonate.

Like the taurides, they form a class of particularly mild anionic surfactants which, unlike ordinary soaps , retain their washing properties even in hard water.
Isethionates are produced on an industrial scale by reacting carboxylic acid mixtures, such as those obtained from the hydrolysis of animal fats ( tallow ) and vegetable oils - preferably coconut oil , but also palm oil , soybean oil or castor oil - with salts of isethionic acid (2-hydroxyethanesulphonic acid) with acid catalysis z. B. made with methanesulfonic acid.

SCI synthesis

Isethionates are solids to which fatty acids (up to 30% by weight) are often added to lower their solidification point. Despite its low solubility in water (100ppm at 25 ° C), the cheaper sodium cocoyl isethionate has become more widespread than the excellent water-soluble ammonium salt (> 25% by weight at 25 ° C). Mixtures with amphoteric surfactants , such as cocamidopropyl betaine , are proposed to solubilize the sparingly soluble isethionates and taurides . Highly concentrated, clear and transparent aqueous concentrates that are liquid at room temperature can be produced from such mixtures.

Isethionates are characterized by excellent skin compatibility, excellent foam formation, even in hard water, good cleaning properties and a pleasant skin feel. They are non-toxic and easily biodegradable. In contrast to the taurides , as carboxylic acid esters, however, they are not long-term stable outside a pH range of 5 to 8.
Isethionates are used in solid soaps, so-called syndet bars, and in other personal care products, such as. B. lotions, washing and shower gels, shampoos , liquid soaps , shaving foams, and other cosmetic and dermatological preparations.

Individual evidence

  1. ↑ M. Friedman, Chapter 5: Chemistry, Formulation, and Performance of Syndet and Combo Bars . In, Spitz, L. (ed), SODEOPEC Soaps, Detergents, Oleochemicals, and Personal Care Products, AOCS Press, Champaign, IL, 2004 and Patent EP0725812 : Process for the preparation of salts and esters of isethionic acid. Filed October 20, 1994 , published August 14, 1996 , Applicant: Henkel Corp., Inventor: Timothy John Cassady, Richard P. Crews, Norman Milstein. ‌
  2. ↑ Patent EP0585071 : Process for the production of acyl isethionates. Applied on August 20, 1993 , published July 24, 1996 , applicant: Hoechst Celanese Corp., inventor: James F. Day, Wolf-Dieter Mueller, Rainer HR Muth. ‌
  3. ↑ Patent EP2033624 : Aqueous concentrates made from isethionate, taurate and betaine. Registered on August 22, 2008 , published on March 11, 2009 , applicant: Clariant International Ltd., inventor: Matthias Loeffler. ‌

literature

Wilfried Umbach (Ed.), Cosmetics and Hygiene from Head to Toe , Wiley-VCH Verlag GmbH & Co. KGaA, 3rd completely revised. u. exp. Edition (July 27, 2012), ISBN 978-3-527-30996-2