Patent ID: 6914115

Claim:
A polyurethane powder coating composition, comprising: A) at least one uretdione-containing powder coating hardener derived from one or more aliphatic, (cyclo)aliphatic, cycloaliphatic, or aromatic polyisocyanates and one or more hydroxyl-containing compounds, and/or one or more monoamines, and having a melting point from 40 to 130° C., a free NCO content of less than 5% by weight, and a uretdione content of 6-18% by weight, B) at least one hydroxyl-containing polymer having a melting point from 40 to 130° C., and an OH number between 20 and 200 mg KOH/gram, and C) at least one catalyst of the formula [NR 1 R 2 R 3 R 4 ] + [R 5 ] − , in which R 1 -R 4 simultaneously, or independently of one another, are alkyl, aryl, aralkyl, heteroaryl or alkoxyalkyl radicals, and wherein each R 1 -R 4 is aromatic, linear or branched, or unbridged or bridged with other radicals, R 1 -R 4 , to form cyclic, bicyclic or tricyclic systems, and wherein the bridging atoms include carbon and/or heteroatoms, and wherein R 1 -R 4 each independently has 1-18 carbon atoms, and wherein each radical R 1 -R 4 optionally contains one or more alcohol, amino, ester, keto, thio, urethane, urea or allophanate groups, double bonds, triple bonds or halogen atoms; and R 5 is either OH or F, and wherein components A) and B) are present in a ratio, such that for each hydroxyl group of component B), there is from 0.3 to 1 uretdione group of component A), and the fraction of component C) is 0.001-3% by weight of the total amount of components A) and B).