Patent No. U.S. 6,884,845 B2
PPG Industries has been granted a patent for a stable aqueous dispersion of a polyester polyol and a carboxylic acid-containing acrylic polymer polyol as a first component, prepared by polymerizing a mixture of ethylenically unsaturated polymerizable monomers, in the absence of solvent. It is comprised of at least one carboxylic acid group-containing monomer; at least one primary alcohol group-containing monomer; at least one glycidyl ester of an aliphatic saturated monocarboxylic acid; and at least one polyester polyol. The polymerization is carried out by feeding a mixture comprising the carboxylic acid, primary alcohol and polyester polyol to a reaction vessel over a period of time. The equivalent ratio of the carboxylic acid groups from the carboxylic acid group-containing monomer to the epoxy group of the glycidyl ester of an aliphatic saturated monocarboxylic acid is greater than 1:1; the weight ratio of polyester polyol to acrylic polymer polyol is in the range of 10:90 to 30:70 and a polyisocyanate crosslinking agent as a second component, wherein the equivalent ratio of hydroxyl groups in to isocyanate functional groups in is from 0.8:1 to 1.7:1.