Abstract: The present invention relates to a polyurethane-modified polyacrylate which is obtainableI. by polymerization with the additiona1) of an essentially carboxyl-free acrylate or of a mixture of acrylates,a2) of an ethylenically unsaturated monomer which carries at least one hydroxyl group per molecule and is essentially carboxyl-free or of a mixture of such monomers, anda3) of an essentially carboxyl-free, ethylenically unsaturated monomer which is different from (a1) and (a2), or of a mixture of such monomers,to give a polyurethane solution which contains no copoly-merizable double bonds,II. by subsequent further polymerization and additionb1) of at least one ethylenically unsaturated monomer which carries one carboxyl group per molecule, or of a mixture of such monomers, andb2) of an essentially carboxyl-free, ethylenically unsaturated monomer, or of a mixture of such monomers,after the monomers added in step I have been almost completely reacted, andIII.