Colored solar-reflective roofing granules, roofing products including them, and methods for making them
The present disclosure relates to roofing granules, such as colored solar-reflective roofing granules, and to methods for making and their use in roofing products. One aspect of the disclosure provides a collection of colored solar-reflective roofing granules, wherein substantially each roofing granule includes an inner layer of a porous ceramic material, the pore size and material of the inner layer being selected such that the inner layer is substantially reflective of infrared radiation; and disposed about and substantially surrounding the inner layer, an outer layer of a substantially colored ceramic material, the outer layer of substantially colored ceramic material being substantially transmissive to infrared radiation, the collection of colored solar-reflective roofing granules having a L* of no more than 60 and a solar reflectivity of at least 30%.
1. A collection of colored solar-reflective roofing granules, wherein substantially each roofing granule comprises
an inner layer of a porous aluminum oxide-based ceramic material having a porosity in the range of 10-50%, the pore size and material of the inner layer being selected such that the inner layer is at least 80% reflective of infrared radiation; and
disposed about and substantially surrounding the inner layer, an outer layer of a substantially colored aluminum oxide-based ceramic material comprising at least one pigment and/or dopant, the outer layer of substantially colored ceramic material being at least 80% transmissive to infrared radiation, the outer layer having a porosity less than 1%,
the collection of colored solar-reflective roofing granules having a L* of no more than 50 and a solar reflectivity of at least 30%.
2. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the outer layer is disposed on an outer surface of the inner layer.
3. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule of the collection the inner layer is formed as a granule core.
4. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule of the collection the inner layer is formed as a layer surrounding a base particle.
5. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the porosity of the inner layer is at least 20%.
6. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the inner layer has a thickness of at least 25 microns and no more than 500 microns.
7. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the inner layer has a thickness of at least 250 microns and no more than 10 mm.
8. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the material of the inner layer is an aluminate, or aluminosilicate-based ceramic.
9. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the outer layer has a thickness of at least 100 nm and no more than 5 microns.
10. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the outer layer is a discrete layer from the inner layer, having a discrete boundary therebetween.
11. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the material of the outer layer is base ceramic material having the pigment and/or dopant dispersed therein.
12. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule the outer layer forms the outermost layer of the roofing granule.
13. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule a substantially transmissive coating is formed on the outer layer.
14. The collection of colored solar-reflective roofing granules according to claim 1 , wherein at least 80% of the granules have a surface roughness Ra of no more than 300 nm.
15. The collection of colored solar-reflective roofing granules according to claim 1 , wherein in substantially each roofing granule of the collection the inner layer is formed as a layer surrounding a base particle, the inner layer has a thickness of at least 25 microns and no more than 1 mm, and the outer layer has a thickness of at least 100 nm and no more than 5 microns.
16. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the aluminum oxide-based ceramic of the inner layer is based on alumina or alumina trihydrate.
17. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the aluminum oxide-based ceramic of the inner layer is based on kaolin or bauxite.
18. The collection of colored solar-reflective roofing granules according to claim 17 , wherein the outer layer is based on alumina.
19. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the outer layer includes one or more of iron(III) and chromium(III) as dopants.
20. The collection of colored solar-reflective roofing granules according to claim 1 , wherein the outer layer has a porosity less than 5%.
21. A roofing product comprising
a substrate;
a bituminous material coated on the substrate, the bituminous material having a top surface; and
the collection of solar-reflective roofing granules according to claim 1 disposed on the top surface of the bituminous material, thereby substantially coating the bituminous material in a region thereof.
22. A collection of colored solar-reflective roofing granules, wherein substantially each roofing granule comprises
an inner layer of a porous aluminum oxide-based ceramic material having a porosity in the range of 10-50%, the pore size and material of the inner layer being selected such that the inner layer is at least 80% reflective of infrared radiation; and
disposed about and substantially surrounding the inner layer, an outer layer of a substantially colored aluminum oxide-based ceramic material comprising at least one pigment and/or dopant, the outer layer of substantially colored ceramic material being at least 80% transmissive to infrared radiation, wherein the outer layer is free of infrared-reflective pigments and dopants,
the collection of colored solar-reflective roofing granules having a L* of no more than 50 and a solar reflectivity of at least 30%.
23. The collection of colored solar-reflective roofing granules according to claim 22 , wherein in substantially each roofing granule the outer layer is disposed on an outer surface of the inner layer.
24. The collection of colored solar-reflective roofing granules according to claim 22 , wherein in substantially each roofing granule the porosity of the inner layer is at least 20%.
25. The collection of colored solar-reflective roofing granules according to claim 22 , wherein in substantially each roofing granule the inner layer has a thickness of at least 25 microns and no more than 500 microns.
26. The collection of colored solar-reflective roofing granules according to claim 22 , wherein in substantially each roofing granule the inner layer has a thickness of at least 250 microns and no more than 10 mm.
27. The collection of colored solar-reflective roofing granules according to claim 22 , wherein the outer layer has a thickness of at least 100 nm and no more than 5 microns.
28. The collection of colored solar-reflective roofing granules according to claim 22 , wherein in substantially each roofing granule a substantially transmissive coating is formed on the outer layer.
29. A roofing product comprising
a substrate;
a bituminous material coated on the substrate, the bituminous material having a top surface; and
the collection of solar-reflective roofing granules according to claim 22 disposed on the top surface of the bituminous material, thereby substantially coating the bituminous material in a region thereof.