Retanning chrome-tanned leather comprises applying a reaction prod. of (a) glycerol monoester of a satd. 12-18C monocarboxylic acid, (b) TDI, hexamethylene diisocyanate (HMDI) or isophorone diisocyanate (IPDI) and (c) dimethylolpropionic acid. The molar ratio NCO gps. of (b):OH gps. of (a)+(c) = 0.5-1.05, pref. 0.8-1.0. Molar ratio (c):(a) = 0.7-1.5, pref. 0.8-1.2; and the carboxyl gps. originating from (c) are at least partially neutralised.
