Aqueous polyurethane dispersions

A polyurethane obtained by reacting:

• a) an NCO-containing prepolymer comprising:
• a1) at least one polyesterpolyol selected from polycarbonatepolyol, carbonate group-free polyesterpolyol, polyestercarbonatepolyol, polyesteramidepolyol,—and polyesterdiol,
• wherein the polyesterpolyol has an average molecular weight, determined as the number average, greater than or equal to 500 g/mol;
• a2) at least one polyetherpolyol that differs from a1) and is free of ester groups selected from polyalkylene glycol,
• wherein the polyetherpolyol of a2) has a molecular weight, determined as the number average, greater than or equal to 500;
• a3) at least one polyol, having a molecular weight of less than 500 g/mol, that carries one or more ionic groups and/or one or more potentially ionic groups;
• a4) at least one aliphatic polyisocyanate, having a molecular weight of less than 500 g/mol;
• a5) optionally, a nonionic polyol having a molecular weight of less than 500 g/mol;
• and
• a6) optionally a monoalcohol with
• b) at least one polysiloxane reactive towards NCO groups having a molecular weight, determined as the number average, of less than 1500 g/mol, and having 1 to 6, amino groups reactive towards NCO groups;
• c) at least one amine reactive towards NCO groups and having an average amino functionality of from 1 to 6 and a molecular weight, as determined as the number average, of less than 500 g/mol that is optionally substituted by hydroxyl groups and/or sulpho groups and/or carboxyl groups, and
• d) water,
• wherein the molar ratio of the hydroxy-functional compounds used for the preparation of the prepolymer a) to the polyisocyanate being from 1:1.1 to 1:2.5;
• and
• wherein the polyurethane has a silicone content of from 0.001 to 2.5 percent by weight based on the solid weight of the polyurethane and wherein the NCO prepolymer, is reacted with component b), the optionally present potentially ionic groups, are then neutralized with a base that is not reactive towards NCO groups, and this neutralized prepolymer is reacted with the component c) and water to give the polyurethane.