Low temperature cure heat-curable powder coating composition comprising a crystalline polyester resin, an amorphous polyester resin, a crosslinking agent and a thermal radical initiator

Abstract

The invention relates to a heat-curable powder coating composition comprising i) at least one crystalline polyester resin present in an amount of at most 90 wt %; and ii) at least one amorphous polyester resin; and iii) at least one crosslinking agent; and iv) at least one thermal radical initiator, wherein, the at least one crystalline polyester resin and/or the at least one amorphous polyester resin has di-acid ethylenic unsaturations; wherein the at least one crosslinking agent is either crystalline or amorphous; wherein the at least one crosslinking agent has reactive unsaturations that are reactable with the ethylenic unsaturations of the di-acid ethylenic unsaturations of the at least one crystalline polyester resin and/or the at least one amorphous polyester resin to be crosslinked, said unsaturations of the crosslinking agent are different from the unsaturations of the at least one crystalline polyester resin and the unsaturations of the at least amorphous polyester resin; wherein the wt % is based on the total amount of i)+ii)+iii). The compositions of the invention may be cured to an acceptable degree at low temperature of for example at most 130° C. for at most 20 minutes, said compositions may be ground, sieved and extrudable and said compositions can upon heat cure form powder coatings that may also exhibit a good balance of properties between good flexibility, good smoothness and good adhesion. In addition, the compositions of the invention can suitably be used on heat- and/or non heat-sensitive, even if the composition is highly pigmented.