WO1994024186B1 - Color-clear composite coatings having improved intercoat adhesion - Google Patents

Abstract

Curable coating compositions based on polyepoxide-containing polymers and polyacid curing agents are disclosed. The polyepoxide-containing polymers contain one or more pendant groups of carbamate, urea or urethane groups. The coating compositions are useful as clear coats in composite color plus clear coatings where the pendant groups provide for better intercoat adhesion.

Claims

- 39 -AMENDED CLAIMS[received by the International Bureau on 15 November 1994 (15.11.94); original claims 1-20 replaced by amended claims 1-17 (3 pages)]

1. A curable composition comprising an epoxy group- containing acrylic copolymer having pendant groups of the structure

H H

I I

X - C - N - R or - N - C - O - R'

II II O O

I wherein X is -N or -0; R is H or an alkyl of 1-18 carbon atoms, or R is bonded to X and forms part of a five- or six-membered ring; and R' is an alkyl of 1-18 carbon atoms, and a polyacid curing agent which is a carboxylic acid group-containing oligomer or polymer.

2. The composition of claim 1 where R is H or alkyl of 1-6 carbon atoms or R is bonded to X and forms part of a 5 or 6 membered ring and R' is alkyl of 1-6 carbon atoms.

3. The curable composition of claim 2 in which X is -0 and R is selected from the group consisting of H and alkyl having 1-6 carbon atoms.

I

4. The curable composition of claim 2 in which X is N-, R is bonded to X and is -CH2-CH2.

5. The curable composition of claim 1 in which the epoxy group-containing acrylic copolymer is a copolymer of glycidyl acrylate or glycidyl methacrylate with at least one other copolymerizable ethylenically unsaturated monomer.

6. The curable composition of claim 1 in which the epoxy group-containing acrylic copolymer has an equivalent weight - 40 -

of from about 5000 to 100,000 based on equivalents of pendant groups.

7. The curable composition of claim 1 where for each equivalent of carboxyl there are 0.8 to 1.5 equivalents of epoxy.

8. A process for applying a composite coating to a substrate which comprises applying to the substrate a colored film-forming composition to form a base coat and applying to said base coat a clear film-forming composition to form a transparent top coat over the base coat, characterized in that the clear film-forming composition is a crosslinkable composition comprising an epoxy group-containing acrylic copolymer and a polyacid curing agent, wherein the epoxy group-containing acrylic copolymer contains one or more pendant groups of the structure:

H H

I I

X - C - N - or - N - C - O -

II II O 0

I where X is -N or -O.

9. The process of claim 8 wherein the pendant groups are of the structure:

H H

I I

X - C - N - R or - N - C - O - R¹

II II 0 O

I where X is -N or -O and R is H or alkyl of 1-18 carbon atoms or R is bonded to X and forms part of a five- or six-membered ring and R' is alkyl of 1-18 carbon atoms.

10. The process of claim 9 where R is H or alkyl of 1-6 carbon atoms or R is bonded to X and forms part of a 5 or 6 membered ring and R' is alkyl of 1-6 carbon atoms. - 41 -

11. The process of claim 10 in which X is -0 and R is selected from the group consisting of H and alkyl having 1-6 carbon atoms.

I

12. The process of claim 10 in which X is N-, R is bonded to X and is -CH2-CH2.

13. The process of claim 13 in which the epoxy group- containing acrylic polymer is a copolymer of glycidyl acrylate or glycidyl methacrylate with at least one other copolymerizable ethylenically unsaturated monomer.

14. The process of claim 8 in which the polyepoxide- containing polymer has an equivalent weight of from about 5000 to 100,000 based on equivalents of pendant groups.

15. The process of claim 8 in which for each equivalent of carboxyl there are 0.8 to 1.5 equivalents of epoxy.

16. A substrate coated by the process of claim 8.

17. A substrate coated by the process of claim 9.