Patent ID: 6998154

Claim:
A coating composition comprising: (a) a binder component, which comprises a highly branched copolyester polyol having a number average molecular weight ranging from 1000 to 30,000, hydroxyl groups ranging from 5 to 200 per polymer chain and carboxyl groups ranging from 0 to 40 per polymer chain, said copofyester polyol being polymerized from a monomer mixture containing a chain extender selected from the group consisting of a hydroxy carboxylic acid, a lactone of a hydroxy carboxylic acid and a combination thereof; and one or more hyper branching monomers, said hyper branching monomer having one carboxyl group and two hydroxyl groups, two carboxyl groups and one hydroxyl group, one carboxyl group and three hydroxyl groups, or three carboxyl groups and one hydroxyl group, and wherein the weight ratio of the hyper branching monomer to the chain extender in said monomer mixture ranges from 1/0.3 to 1/20; and (b) a crosslinking component selected from the group consisting of a polyisocyanate having at least two reactive isocyanate groups, a melamine and a combination thereof, wherein ratio of said isocyanate groups on said polyisocyanate in said crosslinking component to said hydroxyl groups on said highly branched copolyester polyol ranges from 0.25/1 to 3/1 and amount of said melamine in said crosslinking component ranges from 10 weight percent to 40 weight percent, based on the total of said binder and crosslinking components.