Epoxy resin powder coating composition

Claim 2

A powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a maximum dimension not exceeding 150 microns wherein the particles are a blend of: (A) 9-25 parts by weight of an epoxy resin of the formula ##STR10## where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25° C. and having an epoxide equivalent weight of 575-700; (B) 0.9-3 parts by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equivalent weight of 660-810; (C) 20-38 parts by weight of an expoy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula ##STR11## where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860; (D) 0-25 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of O-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34; (E) 10-20 parts by weight of filler particles having a maximum dimension of 10 microns; and (F) 18-25 parts by weight of a resinous curing agent consisting essentially of: (1) 68-81 parts by weight of a compound of the formula ##STR12## and where x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards; (2) 17-30 parts by weight of bisphenol-A; and (3) 0.6-2.0 parts by weight of an alkylimidazole in which the alkyl group contains 1-4 carbon atoms.

Claim 3

The powder coating composition of claim 1 containing pigment in a pigment to binder ratio of 3/100 to 30/100.

Claim 4

The powder coating composition of claim 1 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.

Claim 5

The powder coating composition of claim 1 containing up to 3 percent by weight, based on the weight of the composition, of fumed silica.

Claim 6

The powder coating composition of claim 1 in which the filler particles are silica, barium sulfate, or a mixture of these.

Claim 7

The powder coating composition of claim 5 having: 10-15 parts by weight of Component A; 22-30 parts by weight of Component C; 20-25 parts by weight of Component D; and 21-25 parts by weight of Component F.

Claim 8

The powder coating composition of claim 6 containing pigment in a pigment to binder ratio of 3/100 to 30/100.

Claim 9

The powder coating composition of claim 6 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.

Claim 10

A powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a maximum dimension not exceeding 150 microns wherein the particles are a blend of: (A) 11-12 parts by weight of an epoxy resin of the formula ##STR13## where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25° C. and having an epoxide equivalent weight of 575-700; (B) 1 part by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equivalent weight of 660-810; (C) 22-23 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula ##STR14## where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860; (D) 22-23 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of O-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34; (E) 16-17 parts by weight of filler particles having a maximum dimension of 10 microns wherein the filler particles are silica, barium sulfate, or a mixture of these; and (F) 22-23 parts by weight of a resinous curing agent consisting essentially of: (1) 68-81 parts by weight of a compound of the formula ##STR15## and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards; (2) 17-30 parts by weight of bisphenol-A; and (3) 0.6-2.0 parts by weight of an alkylimidazole in which the alkyl group contains 1-4 carbon atoms.

Claim 11

A powder coating composition which consists essentially of finely divided particles at least 90 percent by weight of which have a maximum dimension not exceeding 150 microns wherein the particles are a blend of: (A) 11-12 parts by weight of an epoxy resin of the formula ##STR13## where n is sufficiently large to provide a resin having a Gardner-Holdt Viscosity of H-L measured at 40 percent polymer solids in diethylene glycol n-butyl ether at 25° C. and having an epoxide equivalent weight of 575-700; (B) 1 part by weight of an epoxy resin having the same general formula as (A) but having a value for n sufficiently large to provide a resin having a Gardner-Holdt Viscosity of K-P measured as above and having an epoxide equivalent weight of 660-810; (C) 22-23 parts by weight of an epoxy/epoxy novolac resin which is an epoxy resin of the formula of (A) modified with an epoxy novolac resin of the formula ##STR14## where n of the epoxy resin and m of the epoxy novolac resin have values sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of W-Z measured as in (A) and having an epoxide equivalent weight of 750-860; (D) 22-23 parts by weight of an epoxy/epoxy novolac resin of the formula of (C) but having values for n and m sufficiently large to provide an epoxy/epoxy novolac resin having a Gardner-Holdt Viscosity of O-S measured as in (A) and having an epoxide equivalent weight of 500-575, wherein the parts by weight of components (C) and (D) total at least 34; (E) 16-17 parts by weight of filler particles having a maximum dimension of 10 microns wherein the filler particles are silica, barium sulfate, or a mixture of these; and (F) 22-23 parts by weight of a resinous curing agent consisting essentially of: (1) 68-81 parts by weight of a compound of the formula ##STR15## and x is a positive number sufficiently large to provide a compound with a weight average molecular weight of 1250-1600, as determined by Gel Permeation Chromatography based on a linear calibration curve obtained from narrow molecular weight polystyrene standards; (2) 17-30 parts by weight of bisphenol-A; and (3) 0.6-2.0 parts by weight of an alkylimidazole in which the alkyl group contains 1-4 carbon atoms.

Claim 12

The powder coating compositing of claim 9 containing pigment in a pigment to binder ratio of 3/100 to 30/100.

Claim 13

The powder coating composition of claim 9 containing up to 1 percent by weight, based on the weight of the composition, of a poly alkylacrylate as a flow control agent.

Claim 14

The powder coating composition of claim 9 in which: component 1 of the curing agent is present in the amount of 70 parts by weight and has a molecular weight of 1312; component 2 of the curing agent is present in the amount of 30 parts by weight; and component 3 of the curing agent is 2-methylimidazole.

Claim 15

The powder coating composition of claim 9 containing up to 3 percent by weight, based on the weight of the composition, of fumed silica.