Coating compositions having improved early hardness

Abstract

A fast hardening clear coating composition for repairing a clear coat/color coat finish or a pigmented mono-coat of a vehicle comprising a film forming binder and an organic liquid carrier, where the binder contains a hydroxyl polymer component comprising (A) hydroxyl-containing acrylic polymer, (B) at least one hydroxyl-terminated component selected from the group consisting of (1) an organic diol having the formula

Description

Claims

1. A coating composition, containing a film forming binder and a volatile organic liquid carrier for the binder, wherein the binder contains (A) a hydroxyl polymer component comprising at least one hydroxyl-containing acrylic polymer;(B) at least one hydroxyl-terminated component selected from the group consisting of (1) an organic diol having the formula

2. The coating composition of claim 1 wherein (B) the at least one hydroxyl-terminated component selected from the group consisting of (1) an organic diol having the formula

3. The coating composition of claim 1 wherein the (B) hydroxyl terminated component consists of the reaction product of trimethylol propane and a lactone.

4. The coating composition of claim 1 wherein the (B) hydroxyl terminated component consists of methyl propane diol.

5. The coating composition of claim 3 wherein the lactone is selected from the group consisting of propiolactone, pivalolactone, butyrolactone, caprolactone and valerolactone.

6. The coating composition of claim 1, wherein the organic polyisocyanate component comprises a trimer of hexamethylene diisocyanate.

7. The coating composition of claim 1, wherein the organic polyisocyanate component comprises a mixture of a trimer of hexamethylene diisocyanate and a trimer of isophorone diisocyanate.

8. The coating composition of claim 7 wherein the organic polyisocyanate component further comprises at least one of an asymmetric hexamethylene diisocyanate trimer, a biuret of hexamethylene diisocyanate, a biuret of isophorone diisocyanate and any mixtures thereof.

9. The coating composition of claim 1, wherein the catalyst system comprises a mixture of at least one dialkyl tin dicarboxylate; at least one tertiary amine selected from the group consisting of trialkylene diamines and trialkyl amines, and mixtures thereof; and at least one aliphatic alkyl carboxylic acid.

10. The coating composition of claim 9 which contains in addition 0.0001 to 1% by weight, based on the weight of the binder, of at least one zinc salt of an aliphatic carboxylic acid or a calcium salt of an aliphatic carboxylic acid.

11. The coating composition of claim 9, wherein at least one of said tertiary amines in said catalyst system has an alkyl or alkylene portion that contains 6 or more carbon atoms.

12. The coating composition of claim 1 containing up to 50% by weight based on the weight of the binder of a hydroxyl terminated oligomer having a weight average molecular weight of about 500 to 2,000.

13. The coating composition of claim 1, wherein the composition is a two-pack coating comprising in the first pack, components (A) combined with components (B) and (D), and in the second pack, component (C), wherein the contents of each pack are mixed together just prior to use.

14. The coating composition of claim 1, wherein the composition is a clear coat for repairing a clear coat/color coat finish.

15. A clear coating composition containing about 25-90% by weight of a film forming binder and about 10-75% by weight of a volatile organic liquid carrier for the binder, wherein the binder comprises (A) a hydroxyl polymer component comprising about 50-98% by weight, based on the total weight of the components A and B, comprising a hydroxyl-containing acrylic polymer having a weight average molecular weight of about 2,000-20,000 and a glass transition temperature of about 10° C. to 90° C.;(B) at least one hydroxyl-terminated component comprising about 2-50% by weight based on the total weight of the components A and B, selected from the group consisting of (1) an organic diol having the formula

16. The coating composition of claim 15 wherein the hydroxyl containing acrylic polymer comprises 5 to 50% by weight, based on the weight of the acrylic polymer, of a hydroxyl acrylic polymer having a weight average molecular weight of above 10,000 to 20,000, 20-60% by weight, based on the weight of the acrylic polymer, of a hydroxyl acrylic polymer having a weight average molecular weight of above 7,000 and up to 10,000 and 20-70% by weight by weight, based on the weight of the acrylic polymer, of a hydroxyl acrylic polymer having a weight average molecular weight of 2,000 up to 7,000.

17. The coating composition of claim 15 wherein the hydroxyl terminated component (B) consists of the reaction of trimethylol propane and caprolactone.

18. The coating composition of claim 15, wherein the composition is a clear coat for repairing a clear coat/color coat finish.

19. A clear coating composition of claim 15 having a VOC content of less than about 0.6 kg/l.

20. The coating composition of claim 1 containing pigments in a pigment to binder ratio of about 0.1:100 to 300:100.

21. The coating composition of claim 15, wherein the composition is a two-pack coating comprising in the first pack, components (A), (B) combined with component (D), and in the second pack, component (C), wherein the contents of each pack are mixed together just prior to use.

22. The coating composition of claim 15, wherein the composition is a clear coat for repairing a clear coat/color coat finish.

23. A process for repairing a clear coat of a clear coat/color coat coating composition which comprises applying a layer of the clear coating composition of claim 1 to the clear coat and curing the layer of the applied clear coating composition.

24. A process for repairing a pigmented mono-coat finish which comprises applying a layer of the pigmented coating composition of claim 20 to the mono coat finish and curing the layer of the applied pigmented coating composition.