White reflective coating for modified bitumen membrane

1. A method of manufacturing a modified bitumen roofing membrane, the method comprising:

providing an aqueous dispersion of a polymeric binder, a polymeric carrier and an effective amount of a pigment that is capable of providing a coating that has an initial energy efficacy rating greater than or equal to 0.65 for a low-sloped roof, or an initial energy efficacy greater than or equal to 0.25 for a steep-sloped roof;

maintaining constant mixing of the aqueous dispersion under low shear conditions of about 60 rpm or less to create a top coating composition;

applying said top coating composition in-plant to an exterior surface of a modified bitumen substrate during manufacture of the roofing membrane; and

curing said top coating composition at the temperature of the environment in which the coated substrate is located.

2. The method of claim 1 wherein the polymeric binder is a thermoplastic polymer selected from the group consisting of acrylic or methacrylic polymers or copolymers, epoxy resins, and polyvinyl acetate.

3. The method of claim 1 wherein the polymeric carrier is water or a hydrocarbon solvent.

4. The method of claim 1 wherein the pigment comprises titanium dioxide, calcium carbonate, colemanite, aluminum trihydrate (ATH), borate compounds or mixtures thereof.

5. The method of claim 1 where the pigment is titanium dioxide.

6. The method of claim 1 wherein the polymeric binder and the polymeric carrier form an aqueous polymeric-based emulsion.

7. The method of claim 1 wherein the polymeric binder and the polymeric carrier form a solvent polymeric-based emulsion.

8. The method of claim 1 wherein the polymeric binder is present in said mixture in an amount from about 30 to about 60 wt. %.

9. The method of manufacturing a roofing membrane of claim 1 wherein the polymeric binder is an acrylic polymer that is present in said mixture in an amount from about 30 to about 60 wt. %.

10. The method of claim 1 wherein the polymeric binder is an acrylic polymer that is present in said mixture in an amount from about 40 to about 50 wt. %.

11. The method of claim 1 wherein the pigment is present in said mixture in an amount from about 1 to about 20 wt. %.

12. The method of claim 1 further comprising the addition of one or more optional components selected from the group consisting of dispersants, defoamers, fillers, solvents, microbiocides, thickening agents, coalescent agents, fire retardants, pH modifiers, wetting agents, light stabilizers, and adhesion promoters.

13. A method of manufacturing a modified bitumen roofing membrane, the method comprising:

(1) mixing the following ingredients as an aqueous dispersion under low shear conditions of about 60 rpm or less to create a top coating composition:

(a) 2-40% water;

(b) 0.1-0.6% potassium tripolyphosphate;

(c) 0.1-7.0% sodium salt of a carboxylic acid;

(d) 0.1-7.0% oil-based defoamer;

(e) 5-60% binder;

(f) 0.1-7% thickener;

(g) 0.5-7.0% coalescing agent;

(h) 5-45% alumina trihydrate;

(i) 0.1-4% microbiocide;

(j) 1-10% zinc borate;

(k) 0.1-4% zinc oxide;

(l) an effective amount of titanium dioxide that is capable of providing a coating that has an initial energy efficacy rating greater than or equal to 0.65 for a low-sloped roof, or an initial energy efficacy greater than or equal to 0.25 for a steep-sloped roof; and

(2) applying said top coating composition in-plant to an exterior surface of a substrate during manufacture of the roofing membrane.

14. The method of claim 13 , further comprising:

(3) curing said top coating composition at the temperature of the environment in which the coated substrate is located.