A New High Gloss Polyester Powder Coatings Catalyst

In polyester powder coatings, the standard catalyst of choice is either dibutyltindilaurate or stannous octoate diluted on a silica powder matrix. After applying this catalyzed polyester powder coating to a substrate, the temperature of cure is raised well above the melting point of the tin catalyst. As a result, the gloss finish of the coating is dull and becomes wavy due to the longer gel times and loss of flow control experienced. A new tin catalyst, hexadecanoic acid, tin (2+) salt, provides a solution to loss of reactivity, coating dullness, and scratch resistance in polyester powder coating formulations. The new tin catalyst provides a higher melting temperature and a higher boiling point to control powder coating flow and volatiles lost to the environment. Also, the catalyst reduces the deblocking temperature of the IPDI-uretidone isocyanate, or a blocked isocyanate hardner which accelerates the crosslinking reaction between the isocyanate moitey and the polyester polyol. The overall advantages the new catalyst produces in a polyester powder coating are better levelling, higher gloss, and scratch resistance coatings.