Abstract: The present invention relates to a process for retanning chrome-tanned leather comprising applying to leather a reaction product of(a) at least one glycerol monoester of a saturated C.sub.12-18 monocarboxylic acid,(b) at least one diisocyanate selected from the group consisting of toluene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, and(c) dimethylolpropionic acid,wherein(i) the components (a), (b) and (c) are so selected that the molar ratio of the isocyanate groups of component (b) to the sum of the hydroxyl groups of components (a) plus (c) is about 0.5 to about 1.05 and(ii) the molar ratio of compound (c) to compound (a) is about 0.7 to about 1.5 and wherein(iii) the carboxyl groups originating from compound (c) are at least partly neutralized.

Abstract: Process for retanning mineral-tanned leathers, characterised in that the retanning agents used are sulphonic acids and/or salts thereof of the general formula ##STR1## wherein R represents hydrogen, --CH.sub.3 or the radicals ##STR2## X represents hydrogen, an alkali metal ion, especially sodium, potassium or lithium ion, or an ammonium ion andn represents 1, 2, 3 or 4.