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 polyiso-cyanate to form a polyurethane prepoly-mer 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.
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