Cationically hydrophilized polyurethaneurea characterized in that it is synthesized from a) 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, (i) comprising at least one polyester polyol b1), which has an amorphous structure and which consists of aromatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, 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, and (ii) comprising at least one polyol b2), which consists of aliphatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, wherein the weight ratio between polyester polyol b1) and polyesterpolyol b2) is between 2:1 and 1:3; 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 and f) optionally at least one compound which has a group that is reactive towards isocyanate groups. a) 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, (i) comprising at least one polyester polyol b1), which has an amorphous structure and which consists of aromatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, 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, and (ii) comprising at least one polyol b2), which consists of aliphatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, wherein the weight ratio between polyester polyol b1) and polyesterpolyol b2) is between 2:1 and 1:3; (i) comprising at least one polyester polyol b1), which has an amorphous structure and which consists of aromatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, 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, and (ii) comprising at least one polyol b2), which consists of aliphatic dicarboxylic acids and/or the corresponding carboxylic anhydrides as acid component, 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 and f) optionally at least one compound which has a group that is reactive towards isocyanate groups.