Patent ID: 6815494
Filing Date: 2004-11-09
Classification: C08G,C09D,Y10T

Abstract:
A method for making an aqueous coating material comprising:I. forming a water-dispersible binder component that contains groups comprising urethane groups and blocked isocyanate groups by a method comprising: (1) reacting at least one polyol and at least one first polyisocyanate to form a polyurethane prepolymer that contains groups comprising isocyanate groups, (2) reacting the polyurethane prepolymer that contains groups comprising isocyanate groups with a first chain extender to give a hydroxyl-containing, chain-extended polyurethane prepolymer, (3) reacting the hydroxyl-containing, chain-extended polyurethane prepolymer with at least one second polyisocyanate to give a further polyurethane prepolymer that contains groups comprising isocyanate groups, and (4) blocking at least a portion of the isocyanate groups of the chain-extended polyurethane prepolymer that contains groups comprising isocyanate groups with a blocking agent to give a polyurethane that contains groups comprising blocked isocyanate groups, and if there are free isocyanate groups remaining, (5) reacting remaining free isocyanate groups in the polyurethane with a second chain extender, adding water to the polyurethane; and II. mixing the water-dispersible binder component with (A) a water-dispersed hydroxy-functional binder component that contains groups comprising urethane groups, (B) a water-dispersible amino resin, (C) optionally, a coatings additive, and (D) optionally, a water-dispersible hydroxy-functional polyester.