Abstract: The present invention relates to copolymers built up of a) 20-60%-wt. ethylenically unsaturated acid-groups-comprising monomers, b) 40-80%-wt. ethylenically unsaturated glycerol derivatives in which one hydroxyl group of the glycerol is unsubstituted, one hydroxyl group is etherified with (meth)-allyl alcohol and the third hydroxyl group is etherified with a C.sub.12 -C.sub.24 -alcohol or C.sub.12 -C.sub.24 -alkyl phenol or esterified with a C.sub.12 -C.sub.40 -monocarboxylic acid and c) 0-30%-wt. other ethylenically unsaturated monomers copolymerizable with the monomers a) and b), whereby the sum of the monomers a+b+c=100. The present invention further relates to the use of said copolymers for the softening of leather. The copolymers according to the present invention result in an improved exhaustion during the leather treatment.