Algae resistant roofing granules with controlled algaecide leaching rates, algae resistant shingles and process for producing same
Algae-resistant roofing shingles are formed by extruding a mixture of mineral particles and a binder to form porous granule bodies, and algaecide is distributed in the pores to provide alqae-resistant granules, which are subsequently applied to roofing shingles. Release of the algaecide is controlled by the structure of the granules.
1. A process for producing algae-resistant roofing shingles, the process comprising producing algae-resistant roofing granules, and adhering the granules to a shingle stock material, wherein the process for producing algae-resistant roofing granules comprises:
(a) providing porous, inert base particles; the base particles being prepared from a mixture including stone dust and a binder; the base particles being fired in a kiln to insolubilize the binder; and
(b) providing at least one inorganic algaecide within the base particles to form algaecide-bearing particles;
wherein the at least one inorganic algaecide is provided in the base particles after the base particles are fired, an algaecide-forming compound being dissolved in a fluid to form a solution, the solution being drawn into the pores in the base particles by capillary action to form solution-laden particles, the solution-laden particles being subsequently treated to convert the algaecide-forming compound to an inorganic algaecide.
2. A process according to claim 1 wherein the binder comprises an aluminosilicate material.
3. A process according to claim 2 wherein the mixture is formed into base particles by a forming process selected from press molding, cast molding, injection molding, extrusion, spray granulation, gel casting, pelletizing, compaction and agglomeration.
4. A process according to claim 1 wherein the at least one inorganic algaecide is selected from the group consisting of copper materials, zinc materials, and mixtures thereof.
5. A process according to claim 4 wherein the inorganic algaecides are cuprous oxide and zinc oxide.
6. A process according to claim 1 wherein the algaecide-forming compound is a soluble copper salt and the solution-laden particles are subsequently treated by heating the particles to convert the soluble copper salt to cuprous oxide.
7. A process for producing algae-resistant roofing shingles, the process comprising producing algae-resistant roofing granules, and adhering the granules to a shingle stock material, wherein the process for producing algae-resistant roofing granules comprises:
(a) providing porous, inert base particles; the base particles being prepared from a mixture including stone dust and a binder; the base particles being fired in a kiln to insolubilize the binder; and
(b) providing at least one inorganic algaecide within the base particles to form algaecide-bearing particles;
wherein the at least one inorganic algaecide is provided in the base particles after the base particles are fired, an algaecide-forming compound being mixed with a binder and a fluid to form a slurry, the slurry being drawn into the pores in the base particles by capillary action to form slurry-laden particles, the slurry-laden particles being subsequently treated to convert the algaecide-forming compound to an inorganic algaecide.
8. A process according to claim 7 wherein the algaecide-forming compound is a soluble copper salt and the slurry-laden particles are subsequently treated by heating the particles to convert the soluble copper salt to cuprous oxide.
9. A process according to claim 1 further comprising coating the algaecide-bearing particles with a colorant composition.
10. A process according to claim 9 wherein the colorant composition includes a fusible binder, and further comprising heating the colorant-coated algaecide-bearing particles to fuse the binder.
11. A process according to claim 7 wherein the binder comprises an aluminosilicate material.
12. A process according to claim 11 wherein the mixture is formed into base particles by a forming process selected from press molding, cast molding, injection molding, extrusion, spray granulation, gel casting, pelletizing, compaction and agglomeration.
13. A process according to claim 7 wherein the at least one inorganic algaecide is selected from the group consisting of copper materials, zinc materials, and mixtures thereof.
14. A process according to claim 13 wherein the inorganic algaecides are cuprous oxide and zinc oxide.
15. A process according to claim 7 further comprising coating the algaecide-bearing particles with a colorant composition.
16. A process according to claim 15 wherein the colorant composition includes a fusible binder, and further comprising heating the colorant-coated algaecide-bearing particles to fuse the binder.