Polyurethane powder coating compositions which have a low stoving temperature

摘要

The present invention relates to a polyurethane powder coating composition containing A) a binder component which is solid below 40 DEG C. and liquid above 130 DEG C. and has an OH number of 25 to 200 and a number average molecular weight of 400 to 10,000, B) a polyaddition compound which is solid below 40 DEG C. and liquid above 125 DEG C., contains uretdione groups and optionally free isocyanate groups and is prepared from aliphatic and/or cycloaliphatic diisocyanates and C) one or more catalysts containing N,N,N'-trisubstituted amidine groups which have an amidine group content (calculated as CN2; molecular weight=40) of 12.0 to 47.0 wt. %, provided that components A) and B) are present in amounts such that component B) has 0.6 to 1.4 isocyanate groups for each hydroxyl group present in component A) and the amount of component C) is 0.05 to 5 wt. %, based on the total weight of the coating composition. The present invention also relates to the use of this powder coating composition for coating heat resistant substrates.