Patent No. U.S. 6,541,595 B2
McWhorter Technologies Inc. has received a patent for a powder coating composition comprising a branched hydroxyl terminated oligoester polyol which has a hydroxyl value in the range of 15 to 250, an acid number of one to 25 and an average molecular weight in the range of 1000 to 7500 daltons. The branched hydroxyl terminated oligoester polyol is the reaction product of a hydroxyl terminated oligoester diol and a polyacid or anhydride having a carboxyl functionality of three or greater; and a uretdione crosslinking agent, the branched hydroxyl terminated oligoester polyol and crosslinking agent each being in relative amounts effective for curing the powder coating composition at a temperature of about 160° C without the use of an effective amount of urethane catalyst and at less than 160° C with the use of a urethane catalyst to provide a cured coating having a pencil hardness of HB or greater, a direct impact resistance of 80 lb. or greater and a reverse impact resistance of 80 lb. or greater at a cured film thickness of 0.8 to 4.0 mils.