Patent ID: 6541595
Filing Date: 2003-04-01
Classification: C08G,C09D

Abstract:
A powder coating composition comprising:a branched hydroxyl terminated oligoester polyol which has a hydroxyl value in the range of from about 15 to about 250, an acid number of about 1 to about 25, and a number average molecular weight in the range of from about 1000 to about 7500 daltons, wherein 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 3 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 160Â° C. without the use of an effective amount of urethane catalyst and at a temperature of less than 160Â° C. with the use of a urethane catalyst to provide a cured coating having a pencil hardness of about HB or greater, a direct impact resistance of about 80 in lb or greater and a reverse impact resistance of about 80 in lbs or greater at a cured film thickness of about 0.8 to about 4.0 mils, the coating composition having a Tg of about 40Â° C. or greater.