High solar-reflectivity roofing granules utilizing low absorption components
An uncolored roofing granule including a low solar absorption base and a low solar absorption and solar opaque coating presented on the base, the coating including a binder, a pigment, wherein the binder includes a curable component and a non-clay, thermally reactive curing agent.
1. A roofing granule comprising:
a low solar absorption base that absorbs less than 50% of the total solar spectrum;
and a low solar absorption and solar opaque coating presented on said base that transmits less than 60% of the total solar spectrum, said coating comprising a binder, a pigment, wherein said binder comprises about 0% by weight clay, wherein said binder comprises a curable component and a thermally reactive curing agent, wherein said curable component comprises a soluble alkali silicate;
wherein the roofing granule does not have specific absorption in the visible region of the solar spectrum,
wherein said base comprises a total solar reflectivity having a cup brightness of at least about 0.70 reflectivity and is selected from the group consisting of polycrystalline silicate, polycrystalline silica, glass ceramic, devitrified ceramic, phase-separated glass, polycrystalline fused oxide, white cement, and any combinations thereof.
2. The roofing granule of claim 1 , wherein said base is white cement, said white cement comprising one or more fillers selected from the group consisting of recycled glass, engineered glass, quartz, alumina, titania, and any combinations thereof.
3. The roofing granule of claim 1 , wherein said reactive curing agent comprises silica nanoparticles dispersed therein.
4. The roofing granule of claim 1 , wherein said pigment is selected from the group consisting of alumina, titania, zinc oxide, UV blocking powders, and any combinations thereof.
5. The roofing granule of claim 1 , wherein said coating has high reflectivity to visible and infrared (IR) light.
6. A roofing article comprising a substrate and a plurality of roofing granules according to claim 1 presented on said substrate, said article further comprising an overcoat presented on said substrate and roofing granules.
7. The roofing article of claim 6 , wherein said overcoat comprises fluorinated polyurethane silane with nanosilica particles dispersed in said fluorinated polyurethane silane.
8. The roofing article of claim 6 , wherein said overcoat comprises a first layer comprising acrylic and a second layer presented on said first layer, said second layer comprising fluorinated polyurethane silane with nanosilica particles dispersed in said fluorinated polyurethane silane.
9. The roofing article of claim 6 , wherein said overcoat comprises a mixture of acrylic and fluorinated polyurethane silane with nanosilica particles dispersed in said fluorinated polyurethane silane.