Biodegradable softeners have attracted recent attention in the prior art. For instance, in German patent no. 197 43 687, in the name of Henkel KGaA, readily biodegradable detergents are described, which contain oligomeric esterquats obtained by quaternizing oligoesters of mono and di-carboxylic acids in combination with alkylene oxide adducts on fatty acid amines.
The international patent application WO-A-01/47489, in the name of Cognis Deutschland GmbH and Bigorra Llosas et al., discloses fiber brightening and softening agents comprising esterquats obtained by reacting alkanol amines with mixtures of fatty acids and dicarboxylic acids, optionally alkoxylating the resulting esters, and quaternizing the products; and auxiliary materials selected from (non)quaternized fatty acid amides, betaines, nonionic surfactants, polyols and/or their derivatives, alcohols and/or hydrotropes.
In the European patent application 1 136 471, in the name of KAO Corporation S.A., alkanol amine esters are described which are based on the esterification reaction of alkanolamines, carboxylic acids and fatty alcohols. The alkanolamines and fatty alcohols are optionally alkoxylated. In addition, the cationic surfactants and esterquats obtainable therefrom are disclosed.
The cationic surfactants and the esterquats disclosed in said European patent application have a high degree of biodegradability, but compared to the biodegradable esterquats of the prior art also exhibit a high degree of efficacy in softening and conditioning natural and synthetic fibers, such as hair, or fibers used in textiles and paper.
In a further aspect, said European patent application relates to aqueous fabric-softening compositions which contain the cationic surfactants or esterquats, optionally together with other active softening substances. Particularly, these fabric softening compositions contain, in an aqueous medium optionally containing constituents selected from those normally used in fabric softener composition: (a) cationic surfactants or esterquats obtainable from the alkanolamines described, (b) one or more cationic surfactants which are active as fabric softeners, and (c) one or more non-ionic fabric-conditioning surfactants, wherein the amount of (a)+(b)+(c) is 2-60 wt. % based on the total composition; the amount of (a), based on the total of (a)+(b)+(c), being 2-100 wt. %; the amount of (b), based on the total of (a)+(b)+(c), being 0-98 wt. %; and the amount of (c), based on the total of (a)+(b)+(c), being 0-40 wt. %.