The invention relates to a cationically hydrophilized polyurethaneurea characterized in that it is synthesized froma) at least one aliphatic, araliphatic and/or cycloaliphatic polyisocyanate,b) polyols having a number-average molecular weight Mn≧400 and ≦6000 g/mol and a hydroxyl functionality of ≧1.5 and ≦4, comprising at least one polyester polyol b1), which has an amorphous structure and which comprises as synthesis component at least one aromatic dicarboxylic acid and/or the corresponding carboxylic anhydride, the fraction of aromatic dicarboxylic acids and/or their anhydrides in the polyester polyol being ≧35 wt %, based on the overall mass of the polyester polyol,c) at least one cationically hydrophilizing component which has at least one group that is reactive towards isocyanate groups, and has at least one cationic or potentially cationic group,d) at least one aliphatic, amino-functional compound which has at least two isocyanate-reactive amino groups,e) optionally at least one alcohol which has at least two hydroxyl groups and a molar mass ≧60 and ≦399 g/mol andf) optionally at least one compound which has a group that is reactive towards isocyanate groups.;The invention further relates to an aqueous dispersion comprising the polyurethaneurea and to a coating composition comprising the polyurethaneurea or the corresponding aqueous dispersion. Further subjects of the invention are a method for coating substrates using the coating composition of the invention, and the coated substrate obtainable in such a method.
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