Patent No. U.S. 7,166,331 B2
E. I. du Pont de Nemours and Company has received a patent for a process for producing a multi-layer coating on a substrate comprised of applying a waterborne primer-surfacer layer to the substrate, allowing evaporation of water and optional organic solvent from the waterborne primer-surfacer layer for 30 to 300 seconds at 15° to 40°C, baking the waterborne primer-surfacer layer and applying a topcoat layer to the waterborne primer-surfacer layer to form a multi-layer coating on the substrate; wherein the waterborne primer-surfacer has a binder solids content with a hydroxyl number of 100 to 250 mg KOH/g and contains free polyisocyanate or blocked polyisocyanate as a crosslinking agent (crosslinking agent) for the hydroxy-functional binder(s) in a molar ratio of OH/NCO of more than 2:1 to 5:1; whereby the binder crosslinks only by baking and only via an OH/NCO reaction.