| abstract |
Aqueous coating material comprising (A) water-dispersible hydroxy-functional binder component containing urethane groups, (B) water-dispersible binder component containing urethane groups and blocked isocyanate groups, (C) water-dispersible amino resin, and optionally (D) water-dispersible hydroxy-functional polyester, the binder component (B) being preparable by (B1) preparing a polyurethane prepolymer containing isocyanate groups from at least one polyol and at least one polyisocyanate, (B2) reacting the polyurethane prepolymer (B1) containing isocyanate groups with a chain extender to give a hydroxyl-containing chain-extended polyurethane prepolymer, (B3) reacting the hydroxyl-containing chain-extended polyurethane prepolymer (B2) with at least one polyisocyanate to give a further polyurethane prepolymer containing isocyanate groups, and (B4) blocking some or all of the isocyanate groups of the chain-extended polyurethane prepolymer (B3) containing isocyanate groups with a blocking agent to give a polyurethane containing blocked isocyanate groups, and then, where appropriate, (B5) reacting remaining free isocyanate groups in the polyurethane (B4) with a chain extender. |