Patents

BASF Coatings patents aqueous

August 11, 2005

Patent No. 6,815,494 B2
BASF Coatings AG has been granted a patent for a method for making an aqueous coating material that is comprised of forming a water-dispersible binder component that contains groups comprising urethane groups and blocked isocyanate groups. The method is comprised of reacting at least one polyol and at least one first polyisocyanate to form a polyurethane prepolymer that contains groups comprising isocyanate groups, reacting the polyurethane prepolymer that contains groups comprising isocyanate groups with a first chain extender to give a hydroxyl-containing, chain-extended polyurethane prepolymer, 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 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, reacting remaining free isocyanate groups in the polyurethane with a second chain extender, adding water to the polyurethane; and mixing the water-dispersible binder component with a water-dispersed hydroxy-functional binder component that contains groups comprising urethane groups, a water-dispersible amino resin, optionally, a coatings additive, and optionally, a water-dispersible hydroxy-functional polyester.