Diblock copolymer dispersants in polyester powder coatings

Poly(2-vinylpyridine)-b-poly( -caprolactone) copolymers have been used as dispersants for TiO2 pigments in a polyester/TGIC powder coating. In coatings without TGIC, the block copolymer dispersants prevented the flocculation of the TiO2 pigments at typical curing temperatures, by the formation of a steric barrier around the pigment particles. Consequently, non-crosslinked powder coatings with high gloss and excellent flow were obtained. In the presence of TGIC, the dispersants were found to catalyse the crosslinking reaction, leading to powder coatings with lower gloss and poor levelling. By replacing the basic poly(2-vinylpyridine) anchor block of the dispersants with an acidic or neutral anchor group, this undesired effect may be avoided. Alternatively, the poly(2-vinylpyridine)-b-poly( -caprolactone) dispersants are expected to be of special benefit in powder coatings with alternative crosslinking mechanisms, such as UV curable powder coatings.