The present application relates to novel copolymers and processes for the preparation thereof, where the copolymers comprise, as building blocks: a C1-20-alkyl (meth)acrylate and/or C8-20-vinylaromatics (monomer a); a monoethylenically unsaturated, hydrophilic monomer comprising at least one sulfonic acid group (—SO3M) (monomer b); and a monoethylenically unsaturated monomer comprising at least one oxazoline group (monomer c); and where the fraction of the monomers a) and b) is in total less than 50% by weight, based on the total amount of the monomers in the copolymer A.