Process for preparing powder coating composition

A process for the preparation of a powder coating composition, comprising the steps of:

• (a) providing a crystalline material consisting of two or more crystalline substances each of which has a melting point of at least 90.degree. C. and one of which has a melting point Mp that is lower than those of the other crystalline substances, said crystalline substances consisting of at least one crystalline epoxy resin and at least one crystalline curing agent;
• (b) providing a non-crystalline material consisting of one or more non-crystalline substances each of which has a softening point of at least 50.degree. C. and one of which has a glass transition point Tg which is lower than those of the other non-crystalline substances and which is lower than said melting point Mp, said non-crystalline substances being selected from the group consisting of non-crystalline epoxy resins, non-crystalline curing agents and mixtures thereof;
• (c) blending said crystalline material with said non-crystalline material to obtain a mixture having a content of said crystalline material of 55-90% by weight based on the total weight of said crystalline and non-crystalline materials and 5-45% by weight of said at least one crystalline curing agent based on the total weight of said crystalline and non-crystalline materials;
• (d) pressing said mixture at a temperature which is higher than said glass transition point Tg but lower than said melting point Mp and which is lower than any softening point of said one or more non-crystalline substances so that said crystalline substances and non-crystalline substances are bonded with each other with said non-crystalline substance having the glass transition point Tg serving as a binder;
• (e) then cooling the mixture obtained in step (d) to a temperature lower than said glass transition point Tg;
• and
• (f) then pulverizing the cooled mixture obtained in step (e).