Binder compositions for powder coatings

Claim 2

A process for producing a cross-linked coating having a non-gloss surface comprising applying to a substrate a powder coating composition comprised of a binder composition comprising at least two saturated cross-linking polyester resins and a cross-linking agent, said resins exhibiting different reactivities with respect to said cross-linking agent wherein the resin exhibiting the highest reactivity has a hydroxyl index between about 175 and 185 and the resin exhibiting the lowest reactivity has a hydroxyl index between about 40 and 60, and heating the thus applied coating to a temperature between about 160° and 220° C. for a period of time between about 5 to 40 minutes to effect cross-linking.

Claim 3

The process of claim 1, wherein the coating composition applied to the substrate further comprises coating additives selected from the group consisting of fillers, pigments, colorants, spreading agents and mixtures thereof.

Claim 4

An article coated by the process of claim 1 or 2.

Claim 5

A process for producing a cross-linked coating having a non-gloss surface comprising applying to a substrate a powder coating composition comprised of a binder composition comprising at least two saturated cross-linking resins wherein said at least two saturated cross-linking resins comprise resins selected from the group consisting of saturated polyester and epoxy resins, and a cross-linking agent, said resins exhibiting different reactivities with respect to said cross-linking agent such that a system comprising the most highly reactive resin and the cross-linking agent, with said system having a weight ratio of cross-linking agent/resin such that there is stoichiometric equilibrium, exhibits a curve on a mechanical spectrometer in an isothermal enclosure at 200° C. having a slope, in its rectilinear part, that is between 0.5×10 5 and 10 6 dynes/cm 2 /minute, and that a system comprising the lesser reactive resin and the cross-linking agent, same having a weight ratio of cross-linking agent/resin such that the ratio of the reactive functions of the cross-linking agent to those of the resin is between about 1.5 and 4 times the stoichiometric ratio, exhibits a curve on a mechanical spectrometer in an isothermal enclosure at 200° C. which has a slope, in its rectilinear part, that is between about 10 3 and 6×10 3 dynes/cm 2 /minute, and then heating the applied coating to a temperature between about 160° and 220° C. for a period of time between about 5 to 40 minutes to effect cross-linking.

Claim 6

A process for producing a cross-linked coating having a non-gloss surface comprising applying to a substrate a powder coating composition comprised of a binder composition comprising at least two saturated cross-linking resins wherein said at least two saturated cross-linking resins comprise resins selected from the group consisting of saturated polyester and epoxy resins, and a cross-linking agent, said resins exhibiting different reactivities with respect to said cross-linking agent such that a system comprising the most highly reactive resin and the cross-linking agent, with said system having a weight ratio of cross-linking agent/resin such that there is stoichiometric equilibrium, exhibits a curve on a mechanical spectrometer in an isothermal enclosure at 200° C. having a slope, in its rectilinear part, that is between 0.5×10 5 and 10 6 dynes/cm 2 /minute, and that a system comprising the lesser reactive resin and the cross-linking agent, same having a weight ratio of cross-linking agent/resin such that the ratio of the reactive functions of the cross-linking agent to those of the resin is between about 1.5 and 4 times the stoichiometric ratio, exhibits a curve on a mechanical spectrometer in an isothermal enclosure at 200° C. which has a slope, in its rectilinear part, that is between about 10 3 and 6×10 3 dynes/cm 2 /minute, and then heating the applied coating to a temperature between about 160° and 220° C. for a period of time between about 5 to 40 minutes to effect cross-linking.

Claim 7

The process of claim 4, wherein the coating composition applied to the substrate further comprises coating additives selected from the group consisting of fillers, pigments, colorants, spreading agents and mixtures thereof.

Claim 8

The process of claim 5, wherein the binder composition of the powder composition applied to the substrate comprises a cross-linking agent which is prepared by the reaction of trimellitic anhydride with an aliphatic diol containing from 2 to 10 carbon atoms at a temperature between about 180° and 250° C. in which the ratio of trimellitic anhydride to diol is between about 2:1 to 2:1.5.

Claim 9

The process of claim 6, wherein the cross-linking agent is the product of the reaction of trimellitic anhydride and ethylene glycol.

Claim 10

An article coated by the process of claim 4 or 5.