Method of preparing homogeneous thermosetting powder paint composition

A method of preparing a powder paint composition comprising:

• A. introducing a liquid composition comprising a solution of inert solvent and an acrylic copolymer containing crosslinkable functional groups selected from the group consisting of epoxy, hydroxyl, amide and carboxyl groups, said copolymer having a glass transistion temperature in the range of 40.degree.C to 90.degree.C and a number average molecular weight of between about 1,000 and about 15,000, into a devolatilizing zone wherein:
• 1. the liquid composition is heated above the melting point of said copolymer and above the temperature at which said inert solvent begins to vaporize, but below the point at which degradation occurs;
• 2. the volatile components are withdrawn from the devolatilizing zone;
• and
• 3. the molten nonvolatile components are collected;
• B. feeding said nonvolatile components at a first stream under pressure at a selected flow rate into a static mixer comprising a conduit containing fixed elements;
• C. simultaneously feed a molten crosslinking agent for said copolymer as a second stream into said static mixer under substantially the same pressure as said nonvolatile components and at a flow rate calculated to provide the mixture with between about 70% and about 130% of the stoichiometric quantity of crosslinking agent for said copolymer, said second stream being introduced at about the center of said first stream;
• D. passing said molten nonvolatile components and said crosslinking agent through said static mixer, which is maintained at a temperature above the melting point of all components but below about 600.degree.F. to thoroughly intermix the same, the average residence time of the mixture within the static mixer being less than about one-half the gel time for the crosslinkable system;
• E. cooling said mixture of nonvolatile components and crosslinking agent to form a solid material;
• and
• F. pulverizing said solid material to form a powder.