Patent ID: 8303943

Claim:
An ampholytic copolymer obtainable by free-radical polymerization of: a) at least one α,β-ethylenically unsaturated monomer of the general formula I in which R 1 is hydrogen or C 1 -C 8 -alkyl, X 1 is O or NR 3 , where R 3 is hydrogen, alkyl, cycloalkyl, aryl or hetaryl, R 2 is branched C 3 -C 5 -alkyl, b) at least one compound with a free-radically polymerizable, α,β-ethylenically unsaturated double bond and at least one cationogenic and/or cationic group per molecule which is a combination of: N-[3-(dimethylamino)propyl](meth)acrylamide and quaternized N,N-dimethylaminoethyl (meth)acrylate with the proviso that at least some of the compounds b) have at least one quaternary nitrogen atom, and 5 to 99% of monomers b) are present in quaternized form; and c) at least one compound with a free-radically polymerizable, α,β-ethylenically unsaturated double bond and at least one anionogenic and/or anionic group per molecule; wherein the copolymer has a molar excess of cationogenic/cationic groups compared to anionogenic/anionic groups as characterized by a molar ratio of cationogenic/cationic groups to anionogenic/anionic groups of at least 1.01 to 1.