Internally catalyzed sulfonate bearing hydroxyl terminated powder

Abstract

A hydroxyl functional polyester suitable for use in powder coating formulations and bearing sulfonate salt groups, its preparation, and its use in powder coating formulations with methoxyalkylene amino group bearing curatives are described. These polyester resins preferably have 200.degree. C. ICI cone and plate viscosities between about 10 and 90 Poise, have DSC determined glass transition temperatures of at least about 40.degree. C., have hydroxyl numbers between about 10 and 60, and have a sulfonate salt group content between about 0.25 and 4 weight percent. They are preferably synthesized by esterification or transesterification utilizing a sulfonate salt group bearing reactant such as 5-sodium sulfo isophthalic acid. The sulfonate salt groups, preferably alkali metal salt groups, serve to catalyze the curing reaction between the resin and the curative. A preferred powder coating composition involves a resin based on terephthalic acid, isophthalic acid and neopentyl glycol and tetramethoxymethyl glycol uril in a resin to curative weight ratio of between about 90:10 and 94:6.