Coating system for cement composite articles
A coated article and method of employing a water-based coating composition on a fiber cement composite substrate is provided. The coating composition contains: an epoxy resin, a crosslinker having epoxide-reactive functional groups, a latex polymer distinct from the epoxy resin, and water.
1. A coated article, comprising:
a fiber cement composite substrate; and
a coating applied to the fiber cement composite substrate, wherein the coating is formed from a water-based coating composition comprising:
an epoxy resin;
a crosslinker having epoxide-reactive functional groups;
a latex polymer, distinct from the epoxy resin; and
water;
wherein the crosslinker is provided in an amount sufficient to react with and crosslink the epoxy resin.
2. The coated article of claim 1 wherein the crosslinker comprises at least one polymer having epoxide-reactive functional groups.
3. The coated article of claim 2 wherein the crosslinker contains active hydrogen groups.
4. The coated article of claim 1 , wherein the epoxy resin is water reducible or water dispersible.
5. The coated article of claim 4 , wherein the epoxy resin is water-dispersible.
6. The coated article of claim 1 , wherein the crosslinker comprises an amine.
7. The coated article of claim 1 , further comprising a latex topcoat layer.
8. The coated article of claim 1 , wherein the water-based coating composition has a molar excess of epoxide groups to epoxide-reactive functional groups.
9. The coated article of claim 8 , wherein the crosslinker comprises an amine and the water-based coating composition has a ratio of epoxide groups to amine groups greater than 1:1 and less than 6:1.
10. The coated article of claim 1 , wherein the water-based coating composition further comprises an aqueous dispersion of polymer particles.
11. The coated article of claim 1 , wherein the water-based coating composition further comprises an aqueous dispersion of polymer particles and a silicate salt.
12. The coated article of claim 11 , wherein the silicate salt is potassium silicate, sodium silicate, lithium silicate, ammonium silicate or a combination thereof.
13. The coated article of claim 11 , wherein the silicate salt is present in an amount of from about 2 to about 50% by weight of the water-based coating composition, based on the total weight of the non-volatile components.
14. The coated article of claim 1 , wherein the water-based coating composition further comprises one or more olefinic compounds.
15. The coated article of claim 1 , wherein one or both of the epoxy resin and the crosslinker are chemically blocked to delay onset of chemical reaction upon mixing; wherein a stimulus is used to de-block the epoxy resin or the crosslinker, allowing the crosslinker to react with and crosslink the epoxy resin.
16. The coated article of claim 15 , wherein the crosslinker has blocked amine groups, yielding a ketimine.
17. The coated article of claim 15 , wherein the stimulus is heat.
18. The coated article of claim 1 , wherein the water-based coating composition is prepared by adding the epoxy resin directly to the latex polymer and mixing.
19. The coated article of claim 1 , wherein the water-based coating composition is prepared by mixing a pre-emulsified epoxy resin with the latex polymer or by adding the epoxy resin to a latex monomer feed during latex polymer synthesis.
20. The coated article of claim 1 , wherein the latex polymer is a multistage latex composition.
21. The coated article of claim 1 , wherein the latex polymer is derived from acetoacetyl ethyl methacrylate.
22. The coated article of claim 1 , wherein the latex polymer is derived from acetoacetyl ethyl methacrylate and comprises amine functional groups.
23. The coated article of claim 1 , wherein the latex polymer comprises an epoxide-reactive functional polymer selected from epoxide reactive polyurethane, vinyl, polyamide, chlorinated polyolefin, acrylic, oil-modified polymer, polyester, or mixtures or copolymers thereof.
24. The coated article of claim 1 , wherein the latex polymer comprises an acetoacetyl-functional polymer selected from acetoacetyl-functional polyurethane, epoxy, polyamide, chlorinated polyolefin, acrylic, oil-modified polymer, vinyl, polyester, or mixtures or copolymers thereof.
25. The coated article of claim 1 , wherein the latex polymer has amine neutralized acid groups.
26. The coated article of claim 1 , wherein the latex polymer is functionalized with olefinic groups or other crosslinkable groups that enable the latex polymer to participate in radiation curing.
27. The coated article of claim 1 , wherein the coating is a dry film.
28. The coated article of claim 1 , wherein the coating is cured.
29. A method, comprising the steps of:
providing a fiber cement composite substrate;
applying to the fiber cement composite substrate a water-based coating composition comprising:
an epoxy resin;
a crosslinker having epoxide-reactive functional groups;
a latex polymer, distinct from the epoxy resin; and
water;
wherein the crosslinker is provided in an amount sufficient to react with and crosslink the epoxy resin.
30. The method of claim 29 , further comprising the step of allowing the water-based coating composition to harden.
31. The method of claim 29 , further comprising applying a latex topcoat layer to the water-based coating composition.
32. The method of claim 31 , wherein the latex topcoat layer is applied to the water-based coating composition while the water-based coating composition is in a liquid state.
33. The method of claim 31 , wherein at least some water from the water-based coating composition is removed prior to applying the latex topcoat layer.
34. The method of claim 33 , wherein a major portion of water from the water-based coating composition is removed prior to applying the latex topcoat layer.
35. The method of claim 31 , further comprising the steps of:
removing water from the water-based coating composition;
curing the water-based coating composition; and
applying the latex topcoat layer to the cured water-based coating composition;
wherein the water-based coating composition has a molar excess of epoxide groups to epoxide-reactive functional groups, and wherein the excess epoxide groups react with active hydrogen groups in the latex topcoat layer.
36. The method of claim 29 , wherein the water-based coating composition further comprises a silicate salt.