Thermosetting powder based on an unsaturated polyester resin

A process for the preparation of a thermosetting fiberless coating powder based on an unsaturated polyester resin having a softening temperature of at least 50.degree. C. comprising the steps of:

• (a) admixing to a melt a homogeneous mixture consisting essentially of 50 to 92 weight percent of an unsaturated polyester resin, 5 to 30 weight percent prepolymer of a diallylester of an aromatic dicarboxylic acid, and from 3 to 20 weight percent of a high-boiling point, cross-linking monomer having a boiling point greater than 200.degree. C. and a vapor pressure less than 10 mm mercury at 150.degree. C., in the absence of the hardening catalyst;
• and
• (b) admixing to the mixture of step (a), the hardening catalyst and the remaining portion, if any, of the components other than the polyester resin at a temperature that is at least 20.degree. C. lower than the temperature at which the half-life value of the hardening catalyst is 1 minute, in which operation the time during which the hardening catalyst is exposed to the higher temperature is a maximum of 30 seconds,
• after which the mixture is rapidly cooled and then ground.