| 摘要 |
<p>A thermosetting powder coating composition according to the present invention comprises as binder a co-reactable particulate mixture of a carboxylic acid-functional polyester component and a curing agent having groups reactive with carboxylic acid groups, characterized in that the carboxylic acid-functional component comprises a semi-crystalline polyester having an acid value of from 10 to 70 mg KOH/g and a hydroxy value of no more than 11 mg KOH/g. Generally the semi-crystalline polyester has one or more Tg values less than 55 DEG C, a sharp melting point of 50 to 200 DEG C and preferably a number average molecular weight of at least 1600. The composition may, if desired, include an amorphous polyester and the curing agent may be, for example, an epoxy resin or a bis(beta-hydroxyalkylamide). Coating compositions of the invention cure faster than in the absence of semi-crystalline polyesters and the thermoset coatings prepared therefrom have improved appearance and mechanical properties (especially flexibility).</p> |
