Isethionates are esters of long-chain aliphatic carboxylic acids (C8 – C18) with isethionic acid (2-hydroxyethanesulfonic acid) or salts thereof, such as ammonium isethionate or sodium isethionate. They are also referred to as acyl isethionates or acyloxyethanesulfonates.

Like the taurides, isethionates are a class of particularly mild anionic surfactants which, unlike ordinary soaps, retain their washing-active properties even in hard water. Isethionates are obtained on an industrial scale reacting mixtures of carboxylic acids with salts of isethionic acid under acidic catalysis e. g. with methanesulfonic acid. The mixtures of carboxylic acids are obtained from the hydrolysis of animal fats (tallow) or vegetable oils, preferably coconut oil, but also palm oil, soybean oil or castor oil.[1]

SCI-Synthese

Isethionates are solids which are often mixed with fatty acids (up to 30% by weight) to lower their freezing point.[2] Despite its low water solubility (100ppm at 25 °C), the lower-priced sodium cocoylisethionate has found more widespread use than its well water-soluble ammonium salt (> 25 wt.% at 25 °C). To solubilize the sparsely soluble isethionates and taurides, the formation of mixtures with amphoteric surfactants (such as cocamidopropyl betaine) are proposed. From such mixtures, it is possible to prepare liquid, clear and transparent aqueous concentrates which are liquid at room temperature.[3]

Isethionates are characterized by excellent skin compatibility, excellent foaming (even in hard water), good cleansing properties and a pleasant skin feel. They are non-toxic and readily biodegradable. However, in contrast to the taurides, 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 lotions, washing and shower gels, shampoos, liquid soaps, shaving creams, and other cosmetic and dermatological preparations.

List

name formula n Mol Wt CASNo EC Number UNII PubChem CID SMILES
Sodium butyl isethionateC6H11NaO5S0218.19961789-32-0263-052-5CID 123134487 from PubChemCCCC(=O)OCCS(=O)(=O)[O-].[Na+]
Sodium capryloyl isethionateC10H19NaO5S2274.30738207-61-3AR33Z8R7V7CID 71587139 from PubChemCCCCCCCC(=O)OCCS(=O)(=O)[O-].[Na+]
Sodium caproyl isethionateC12H23NaO5S3302.36129454-06-6249-638-37K2K7966INCID 73555691 from PubChemCCCCCCCCCC(=O)OCCS(=O)(=O)[O-].[Na+]
Sodium lauroyl isethionateC14H27NaO5S4330.4157381-01-3230-949-8M590021Z02CID 23668826 from PubChemCCCCCCCCCCCC(=O)OCCS(=O)(=O)[O-].[Na+]
Sodium palmitoyl isethionateC18H35NaO5S6386.52336915-65-8253-273-5O4087ZSO8UCID 23688965 from PubChemCCCCCCCCCCCCCCCC(=O)OCCS(=O)(=O)[O-].[Na+]

References

  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 und EP patent 0725812, Timothy John Cassady, Richard P. Crews, Norman Milstein, "Verfahren zur Herstellung von Salzen und Estern der Isethionsäure", issued 1996-08-14, assigned to Henkel Corp.
  2. EP patent 0585071, James F. Day, Wolf-Dieter Mueller, Rainer H.R. Muth, "Verfahren zur Herstellung von Acylisethionaten", issued 1996-07-24, assigned to Hoechst Celanese Corp.
  3. EP patent 2033624, Matthias Loeffler, "Wässrige Konzentrate aus Isethionat, Taurat und Betain", issued 2009-03-11, assigned to Clariant International Ltd.

Literature

Wilfried Umbach (Hrsg.), Kosmetik und Hygiene von Kopf bis Fuß, Wiley-VCH Verlag GmbH & Co. KGaA, 3. vollst. überarb. u. erw. Auflage (27. Juli 2012), ISBN 978-3-527-30996-2

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.