An improved aqueous coating agent for providing a decorative and protective coating for wood or wood products contains as a binder polyacrylate resins having chemically incorporated therein air-drying, unsaturated fatty acid moieties and quaternary ammonium moieties, and said agent is prepared by reactingA) excess polyacrylates containing epoxide groups and having an epoxide group equivalent weight of 200 to 1,300 withB) drying fatty acids, in an addition reaction with ester formation,C) reacting at least some of the remaining epoxide groups in the A)-B) reaction product with monoamine ammonium salts which contain an N-H bond in an addition reaction, anddissolving the reaction product obtained from step C) and containing quaternary ammonium groups in water.