Patent ID: 6277917
Filing Date: 2001-08-21
Classification: B05D,C08L,C09D,Y10S,Y10T

Abstract:
A curable powder clear coating composition comprising:(I) from 60 to 99.99 percent by weight based on solids of the curable coating composition of at least one film-forming polymeric material, wherein the predominant film-forming polymeric material is a blend of at least two epoxy functional acrylic copolymers comprising:(a) a first epoxy functional acrylic copolymer having:A) a number average molecular weight in the range of about 1000 to 5500 grams;B) a calculated Tg in the range of 50.degree. C. to 85.degree. C.;C) a styrene content resulting from an amount of styrene monomer in the range of up to about 25 weight percent based on the weight percent of the monomers to form the copolymer;D) epoxy content from 35 to 85 from glycidyl functional ethylenically unsaturated monomer,said copolymer formed by polymerizing (i) 35 to 85 percent by weight of a glycidyl functional ethylenically unsaturated monomer, and (ii) 15 to 65 percent of a copolymerizable ethylenically unsaturated monomer or mixture of monomers free of glycidyl functionality to provide an effective amount of (ii) monomers including a high Tg component monomer to yield the Tg for the copolymer, where all percents by weight are based on the weight of (i) and (ii); and(b) a second epoxy functional acrylic copolymer having:A) a number average molecular weight in the range of about 500 to about 3000,B) a calculated Tg in the range of about 35.degree. C. to about 125.degree. C., andC) an epoxy content of 90 from glycidyl functional ethylenically unsaturated monomer;wherein each of the first and second copolymers of the blend are formed respectively by polymerizing (i) glycidyl functional ethylenically unsaturated monomer, and (ii) copolymerizable ethylenically unsaturated monomer or mixture of monomers free of glycidyl functionality and having a effective amount and type of other monomers (ii) to yield the Tg for the respective copolymer, so that for the blend of copolymers the epoxy functionality is derived from at least 35 percent by weight of (i) of the glycidyl functional ethylenically unsaturated monomer, and wherein the percent by weight is based on the weight of (i) and (ii); and wherein the blend of the first and second epoxy functional acrylic copolymers has a total styrene content in an amount up to 39 percent by weight; and(II) 10 to 40 percent by weight based on the weight of (I) and (II) of a polycarboxylic acid crosslinking agent, where the ratio of epoxy functionality for (I) to acid functionality for (II) is about 1:0.6 to 1.4.