Thermosetting acrylic resin powder coating compositions

Claim 1

A thermosetting acrylic resin powder coating composition comprising: (A) a mixture of 10 to 90% by weight of a glycidyl-containing acrylic resin comprising (i) 15 to 40% by weight of a glycidyl-containing vinyl monomer and/or methylglycidyl-containing vinyl monomer, (ii) 10 to 85% by weight of an acrylate and/or methacrylate and (iii) 0 to 50% by weight of other vinyl monomer, and 90 to 10% by weight of a hydroxyl-containing acrylic resin comprising (i) ' 5 to 40% by weight of a hydroxly-containing vinyl monomer, (ii) 10 to 95% by weight of an acrylate and/or methacrylate and (iii) 0 to 50% by weight of other vinyl monomer, or a glycidyl- and hydroxyl-containing acrylic resin comprising (i) 15 to 30% by weight of a glycidyl-containing vinyl monomer and/or methylclycidyl-containing vinyl monomer, (ii) 5 to 20% by weight of a hydroxyl-containing vinyl monomer, (iii) 10 to 80% by weight of an acrylate and/or methacrylate and (iv) 0 to 40% by weight of other vinyl monomer, (B) a blocked isocyanate compound having a melting point of 60° to 140° C. and solid at room temperature, (C) an aliphatic dibasic acid or anhydride thereof, and (D) at least one tin compound represented by the formula SnO 2 , R 2 SnO, R 2 SnX 2 , R 2 Sn(OCOR') 2 , ##STR7## R 3 SnX, R 3 Sn-O-SnR 3 ##STR8## or R 4 Sn wherein R is phenyl or alkyl having 1 to 18 carbon atoms, X is halogen, alkoxyl having 1 to 18 carbon atoms or hydroxyl, R' is alkyl or alkenyl having 1 to 18 carbon atoms and n is an integer of 1 to 5, each of the acrylic resins having a glass transition temperature of 50° to 90° C. and a weight average molecular weight of 5000 to 20000, wherein when said mixture is used as the component (A), the coating composition comprises 45 to 80% by weight of the mixture, 20 to 40% by weight of the blocked isocyanate compound (B), 3 to 20% by weight of the aliphatic dibasic acid or anhydride thereof (C) and 0.1 to 5% by weight of the tin compound (D), or when said glycidyl- and hydroxyl-containing acrylic resin is used as the component (A), the coating composition comprises 45 to 75% by weight of the acrylic resin, 22 to 40% by weight of the blocked isocyanate compound (B), 3 to 12% by weight of the aliphatic dibasic acid or anhydride thereof (C), and 0.4 to 4.0% by weight of the tin compound (D).