Powder coating composition employing mixture of polyepoxide resin with modified polyester resin

Claim 1

A homogeneous pulverulent substantially unreacted thermosettable composition comprising a mixture of: (1) 4% to 25% by weight of a polyepoxide compound or mixture of compounds, the molecules of which contain an average of at least two epoxy groups, and (2) 75.% to 96% by weight of a solid modified polyester resin having an acid number of from 30 to 100, and which softens in the range 60° C. to 130° C., said solid modified polyester resin comprising the reaction product of: (a) an anhydride of a polybasic, organic carboxylic acid, and (b) a polyester resin having a hydroxyl number of from 15 to 50, the acid component of this polyester resin comprising a dibasic, aromatic carboxylic acid and the alcohol component comprising: (c) from 0 to 100 mole % (based on the total alcohol component of the polyester) of an alcohol having the general formula: ##STR3## in which R 1 and R 2 represent alkylene groups having from 2 to 4 carbon atoms, R 3 represents a direct bond between the rings or an alkylidene group having from 1 to 4 carbon atoms or a cycloalkylidene group having 6 carbon atoms, or a carbonyl group, or a sulphone group, x and y are numerals each being at least one, the sum of x and y being not greater than 6, and R 4 and R 5 represent a hydrogen atom or alkyl radical having from 1 to 6 carbon atoms; (d) from 0 to 40 mole % (based on the total alcohol component of the polyester) of a glycidyl ester of the general formula: ##STR4## in which R is a straight or branched chain, saturated or unsaturated hydrocarbon radical having from 4 to 20 carbon atoms, or a substituted or unsubstituted benzene nucleus, and (e) from 0 to 100 mole % (based on the total alcohol component of the polyester) of at least one dihydric, aliphatic alcohol, the sum of the alcohol components (c), (d), and (e) being 100 mole %, and said composition having a good powder stability.