ROOFING GRANULES WITH HIGH SOLAR REFLECTANCE, ROOFING PRODUCTS WITH HIGH SOLAR REFLECTANCE, AND PROCESS FOR PREPARING SAME

1 . Solar heat-reflective roofing granules comprising:

a) a base particle having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh,

b) a uniform coating layer on the base particle, the coating layer having a thickness of at least one mil, the coating layer comprising a coating binder and at least one solar heat-reflective pigment, the solar heat-reflective pigment providing a solar heat reflectance of greater than 70 percent to the granules.

2 . Solar heat-reflective roofing granules according to claim 1 , wherein the roofing granules have an aspect ratio of at least 3.

3 .- 4 . (canceled)

5 . Solar heat-reflective roofing granules according to claim 1 , wherein the coating layer has a thickness of at least 2 mils.

6 . Solar heat-reflective roofing granules according to claim 1 , wherein the base particles are selected from the group consisting of crushed slate, slate granules, shale granules, mica granules, metal flakes, and flake-like synthetic particles.

7 . Solar heat-reflective roofing granules according to claim 1 , wherein the coating binder is selected from the group consisting of metal silicates, fluoropolymers, metal phosphates, silica coating binders, sol-gel coating binders, polysiloxanes, silicones, polyurethanes, and polyacrylates.

8 . Solar heat-reflective roofing granules according to claim 1 , wherein the at least one solar heat-reflective pigment is selected from the group consisting of titanium dioxide, calcium carbonate, zinc oxide, lithopone, zinc sulphide, white lead, glass microspheres, glass microbubbles, microvoid pigments, and synthetic polymeric opacifiers.

9 . Solar heat-reflective roofing granules according to claim 1 , which have (a* 2 +b* 2 ) 1/2 less than 6.

10 . A solar heat-reflective roofing product comprising:

a) a base sheet, and

b) solar heat-reflective roofing granules on top of the base sheet, the granules comprising:

1) a base particle having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh,

2) a uniform coating layer on the base particle, the coating layer having a thickness of at least one mil, the coating layer comprising a coating binder and at least one solar heat-reflective pigment, the solar heat-reflective pigment providing a solar heat reflectance of greater than 70 percent to the granules.

11 . A solar heat-reflective roofing product according to claim 10 wherein the granules cover at least 85 percent of the surface area of the base sheet.

12 . (canceled)

13 . (canceled)

14 . A solar heat-reflective roofing product according to claim 10 , wherein the roofing granules particles have an aspect ratio of at least 3.

15 .- 20 . (canceled)

21 . A solar heat-reflective roofing product according to claim 10 wherein the solar heat-reflective roofing granules have (a* 2 +b* 2 ) 1/2 less than 6.

22 . A solar heat-reflective roofing product according to claim 10 , the solar heat-reflective roofing granules comprising primary roofing granules, the shingle further comprising secondary roofing granules interspersed among the primary roofing granules.

23 . A solar heat-reflective roofing product according to claim 22 , the secondary roofing granules including at least one algaecide.

24 . A process for preparing solar heat reflective roofing granules, the process comprising:

a) providing base particles having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh,

b) providing a coating composition including a coating binder and at least one solar heat-reflective pigment; and

c) coating the base particles with the coating composition to provide a uniform coating layer on the base particles, the solar heat-reflective pigment providing a solar heat reflectance of greater than 70 percent to the granules.

25 . A process for preparing solar heat reflective roofing products, the process comprising:

a) providing base particles having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh,

b) providing a coating composition including a coating binder and at least one solar heat-reflective pigment;

c) coating the base particles with the coating composition to provide a uniform coating layer on the base particles, the solar heat-reflective pigment providing a solar heat reflectance of greater than 70 percent to the granules, thus providing solar heat-reflective roofing granules;

d) providing a bituminous base sheet having an upper surface; and

e) applying the solar heat-reflective roofing granules to the upper surface of the base sheet, the solar heat heat-reflective roofing granules being applied to at least 85 percent of the upper surface.

26 . A process according to claim 25 wherein the solar heat-reflective roofing granules are applied to at least 90 percent of the upper surface.

27 . (canceled)

28 . Solar heat-reflective roofing granules according to claim 9 , having a value of L* of at least one of greater than about 80, greater than about 85 or greater than about 90.

29 .- 31 . (canceled)

32 . A solar heat-reflective roofing product according to claim 10 , wherein the roofing product is a roofing membrane.

33 . (canceled)

34 . A solar heat-reflective roofing product according to claim 10 , wherein the roofing product is a shingle.

35 .- 38 . (canceled)

39 . A process according to claim 24 , wherein the coating layer has an average coating thickness, and the coating thickness does not vary by more than about 25 percent of the average coating thickness.

40 . A process according to claim 25 , wherein the solar heat-reflective roofing granules comprise a first class of granules, and a second class of granules are provided, the second class of granules having a smaller average dimension than the first class of granules, and granules of the second class of granules are applied to the upper surface of the base sheet.

41 . A process according to claim 40 , wherein the granules of the second class have a size and a shape selected so that granules of the second class of granules will tend to lie in interstitial spaces between granules of the first class of granules.