Multi-component coating method for porous substrates

1. A method of coating a porous fibrous cement substrate, comprising the steps of:

providing a multi-component coating composition comprising:

a first component comprising an isocyanate compound, and

a second component comprising an amino-functional compound reactive with the isocyanate compound or a hydroxyl-functional compound reactive with the isocyanate compound, wherein each component in the multi-component coating composition is housed in a separate container prior to application to a surface of a porous fibrous cement substrate;

applying each of the first and the second component to the surface at a selected application rate for each component, wherein the first component is applied to the surface before the second component is applied to the surface, and wherein the first component penetrates into the surface for a penetration time before applying the second component;

removing at least a portion of the first component from the surface after allowing at least some of the first component to penetrate into the surface for the penetration time;

allowing the first component and the second component to mix on the surface to form the multi-component coating composition thereon, wherein the first component and the second component undergo a chemical reaction on the surface.

2. The method of claim 1 , wherein the porous fibrous cement substrate comprises a fibrous cement board.

3. The method of claim 1 , wherein the second component comprises an amino-functional compound.

4. The method of claim 3 , wherein the amino-functional compound comprises at least one group with a nitrogen atom having a lone pair of electrons.

5. The method of claim 4 , wherein the group is selected from NH or NH 2 .

6. The method of claim 1 , wherein the multi-component coating composition further comprises at least one additive selected from the group consisting of a catalyst, a wetting agent, or a rheology control agent.

7. The method of claim 1 , wherein the penetration time for the first component is about 0.5 seconds to about 5 seconds.

8. The method of claim 1 , wherein removing at least a portion of the first component of the multi-component coating composition from the surface of the porous substrate comprises directing a gas stream against at least a portion of the surface after allowing at least some of the first component to penetrate into the surface for the penetration time.

9. The method of claim 1 , wherein applying each component to the surface comprises coating the component onto the surface by one or more of brush coating, knife coating, direct roll coating, reverse roll coating, spray coating, extrusion die coating, curtain coating, flood coating and vacuum coating.

10. The method of claim 1 , further comprising drying the first component on the surface prior to application of the second component.

11. The method of claim 1 , further comprising heating the surface before and after applying the first or the second component.

12. A method, comprising:

housing a first component in a first container, wherein the first component comprises an isocyanate compound;

housing a second component in a second container different from the first container, wherein the second component comprises an amino-functional compound reactive with the isocyanate compound;

applying the first component to a surface of a fiber cement substrate at a selected first component application rate;

removing at least a portion of the first component from the surface by directing a gas stream against at least a portion of the surface, wherein the first component is removed after allowing at least some of the first component to penetrate into the surface for a penetration time;

applying the second component on the first component at a selected second component application rate; and

allowing the first component and the second component to mix on the surface, wherein the first component and the second component undergo a chemical reaction on the surface.

13. The method of claim 12 , wherein the fiber cement substrate comprises a fibrous cement board.

14. The method of claim 12 , wherein the amino-functional compound comprises a group selected from NH or NH 2 .