Roofing granules comprising sintered base particles
A roofing product can include roofing granules, wherein the roofing granules include base particles and a coating covering the base particles. The base particles are sintered. The coating has a depth of penetration into an outside surface of at least about 0.5% of an average radius of the base particles. In an embodiment, the coating has a depth of penetration into an outside surface of at least about 2.5 microns into the base particles. Further included is a process of forming the roofing granules.
1. A process of forming roofing granules comprising:
providing sintered base particles, wherein the sintered base particles have a surface morphology that is porous; and
forming a coating along an outside diameter of the base particles, wherein the coating has a depth of penetration into an outside surface of at least about 0.5% of an average radius of the base particles.
2. The process of claim 1 , wherein the base particles are sintered at a temperature of about 900° C. to about 1450° C. to provide the porous surface morphology.
3. The process of claim 1 , wherein the coating is present at about 1.0 wt. % to about 10.0 wt. % greater than the water absorption of the base particles.
4. The process of claim 1 , wherein the coating has a depth of penetration not greater than about 10.0%.
5. The process of claim 1 , wherein the roofing granules have a delta solar reflectance of less than about 0.20.
6. The process of claim 1 , wherein the base particles have a solar reflectance of at least about 0.25 prior to coating.
7. The process of claim 1 , wherein the coating has an L* value less than about 50, as measured by a CIE LAB color scale.
8. The process of claim 1 , wherein the coating comprises a metal silicate, a silicone, a fluoropolymer, a polysiloxane, an acrylic, a urethane, an epoxy, a silica, a sol-gel, a phosphate, a metal oxide, a powder, a thermal spray, or combination thereof.
9. The process of claim 1 , wherein the roofing granules have a solar reflectance of greater than about 0.25.
10. A process of forming roofing granules comprising:
providing sintered base particles, wherein the sintered base particles have a surface morphology that is porous; and
forming a coating along an outside diameter of the base particles, wherein the coating has a depth of penetration into an outside surface of at least about 2.5 microns into the base particles.
11. The process of claim 10 , wherein the depth of penetration into the outside surface is not greater than about 50 microns.
12. The process of claim 10 , wherein the base particles are sintered at a temperature of about 900° C. to about 1450° C. to provide the porous surface morphology.
13. The process of claim 10 , wherein the coating is present at about 1.0 wt. % to about 10.0 wt. % greater than the water absorption of the base particles.
14. The process of claim 10 , wherein the coating has a total average thickness of about 5 microns to about 50 microns.
15. The process of claim 10 , wherein the coating comprises an outer portion that has not penetrated into the base particles.
16. The process of claim 10 , wherein the roofing granules have a delta solar reflectance of less than about 0.20.
17. The process of claim 10 , wherein the base particles have a solar reflectance of at least about 0.25 prior to coating.
18. The process of claim 10 , wherein the coating has an L* value less than about 50, as measured by a CIE LAB color scale.
19. The process of claim 10 , wherein the coating comprises a metal silicate, a silicone, a fluoropolymer, a polysiloxane, an acrylic, a urethane, an epoxy, a silica, a sol-gel, a phosphate, a metal oxide, a powder, a thermal spray, or combination thereof.
20. The process of claim 10 , wherein the roofing granules have a solar reflectance of greater than about 0.25.