Thermosetting powder coating composition of an acrylic polymer, dodecanedioic acid, cellulose acetate butyrate and a cross-linking agent

Claim 1

A thermosetting polymer powder coating composition comprising finely divided particles having a particle size of about 1-100 microns; wherein the particles are an intimately mixed blend of constituents consisting essentially of about (A) 55-85% by weight of an acrylic polymer consisting essentially of (1) about 5-25% by weight, based on the weight of the acrylic polymer, of glycidyl methacrylate or glycidyl acrylate, (2) about 75-95% by weight, based on the weight of the acrylic polymer, of an alkyl methacrylate or an alkyl acrylate each having 1-12 carbon atoms in the alkyl groups or a mixture of said alkyl methacrylate and said alkyl acrylate; and wherein the acrylic polymer has a weight average molecular weight of 5,000-15,000, and a glass transition temperature of 50°-98° C.; (b) 5-15% by weight of dodecanedioic acid; (C) 5-20% by weight of cellulose acetate butyrate having a viscosity of about 0.005-1.0 seconds measured according to ASTM-D-134356 at 25° C. and a butyryl content of about 25-60%; (D) 2-8% by weight of an alkylated melamine formaldehyde cross-linking agent having 1-4 carbon atoms in the alkyl group; and (E) 0.1-2.0% by weight of a blocked acid catalyst wherein the molar ratio of carboxyl groups of the dodecanedioic acid to epoxy groups of the acrylic polymer is about 0.8-1.5.