Roofing granules with high solar reflectance, roofing products with high solar reflectance, and processes for preparing same
A solar heat-reflective roofing product includes a base sheet, and solar heat-reflective roofing granules on top of the base sheet. The granules have a base particle with a flake-like geometry covered by a uniform coating layer. The coating layer has a thickness of at least one mil and includes a coating binder and at least one solar heat-reflective pigment. The solar heat-reflective pigment provides a solar heat reflectance of greater than 70 percent to the granules and the roofing product. Roofing products including roofing shingles and roofing membranes are described.
1 - 20 . (canceled)
21 . Solar heat-reflective roofing granules comprising:
a base particle having a flake-like geometry, an average particle size from #5 US mesh to #50 US mesh, and UV opacity greater than 70 percent;
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;
wherein the roofing granules have an aspect ratio of at least 5 and a solar heat reflectance of at least 70 percent.
22 . Solar heat-reflective roofing granules according to claim 21 , wherein the roofing granules have an aspect ratio of at least 7.
23 . Solar heat-reflective roofing granules according to claim 21 , the base particles having UV opacity greater than 80 percent.
24 . Solar heat-reflective roofing granules according to claim 21 , wherein the coating layer has a thickness of at least 2 mils.
25 . Solar heat-reflective roofing granules according to claim 21 , wherein the base particles are selected from the group consisting of naturally occurring rocks.
26 . Solar heat-reflective roofing granules according to claim 12 , wherein the coating binder is selected from the group consisting of metal silicates, metal phosphates, silica coating binders, and sol-gel coating binders.
27 . Solar heat-reflective roofing granules according to claim 21 , wherein the coating binder is an organic binder.
28 . Solar heat-reflective roofing granules according to claim 21 , 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.
29 . Solar heat-reflective roofing granules according to claim 21 , which have (a* 2 +b* 2 ) 1/2 less than 6.
30 . Solar heat-reflective roofing granules according to claim 21 , wherein the coating weight per unit surface area varies by no more than 10 percent.
31 . Solar heat-reflective roofing granules according to claim 21 , wherein the coating completely covers the base particles.
32 . A solar heat-reflective roofing product comprising:
a base sheet, and
solar heat-reflective roofing granules laying flat on top of the base sheet, the granules comprising:
a base particle having a flake-like geometry, an average particle size from #5 US mesh to #50 US mesh, and UV opacity greater than 70 percent,
a 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,
wherein the granules have an aspect ratio of at least 5 and a solar reflectance of at least 70 percent.
33 . A solar heat-reflective roofing product according to claim 32 , wherein the granules cover at least 90 percent of the surface area of the base sheet.
34 . A solar heat-reflective roofing product according to claim 32 , wherein the roofing granules have an aspect ratio of at least 7.
35 . A solar heat-reflective roofing product according to claim 32 , the base particles having UV opacity greater than 90 percent.
36 . A solar heat-reflective roofing product according to claim 32 , wherein the coating layer has a thickness of at least 2 mils.
37 . A solar heat-reflective roofing product according to claim 32 , having a solar reflectance of greater than 70%.
38 . A solar heat-reflective roofing product according to claim 32 , further comprising a plurality of second granules disposed on the base sheet in interstices between the solar heat-reflective roofing granules.
39 . A process for preparing solar heat reflective roofing granules, the process comprising:
providing base particles having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh;
providing a coating composition including a coating binder and at least one solar heat-reflective pigment;
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.
40 . A process for preparing solar heat reflective roofing products, the process comprising:
providing base particles having a flake-like geometry, and an average particle size from #5 US mesh to #50 US mesh;
providing a coating composition including a coating binder and at least one solar heat-reflective pigment;
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;
providing a bituminous base sheet having an upper surface; and
applying the solar heat-reflective roofing granules to the upper surface of the base sheet, the solar heat-reflective roofing granules being applied to at least 85 percent of the upper surface.