ALGAE RESISTANT ROOFING GRANULES WITH CONTROLLED ALGAECIDE LEACHING RATES, ALGAE RESISTANT SHINGLES, AND PROCESS FOR PRODUCING SAME
Algae-resistant roofing granules are formed by extruding a mixture of mineral particles and a binder to form porous granule bodies, and algaecide is distributed in the pores. Release of the algaecide is controlled by the structure of the granules.
1 . An algae-resistant roofing shingle, the shingle being produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a shingle stock material, the algae-resistant roofing granules being produced by a process comprising:
(a) providing porous, inert base particles; and
(b) providing at least one inorganic algaecide on or within the base particles to form algaecide-bearing particles.
2 . An algae-resistant roofing shingle according to claim 1 , wherein the base particles are prepared from a mixture including stone dust and a binder.
3 . An algae-resistant roofing shingle according to claim 2 wherein the binder comprises an aluminosilicate material.
4 . An algae-resistant roofing shingle according to claim 3 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.
5 . An algae-resistant roofing shingle according to claim 1 wherein the at least one inorganic algaecide is provided on the base particle by coating the base particle with the at least one inorganic algaecide.
6 . An algae-resistant roofing shingle according to claim 3 wherein the base particles are fired in a kiln to insolubilize the binder.
7 . An algae-resistant roofing shingle 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.
8 . An algae-resistant roofing shingle according to claim 7 wherein the inorganic algaecides are cuprous oxide and zinc oxide.
9 . An algae-resistant roofing shingle according to claim 7 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.
10 . An algae-resistant roofing shingle according to claim 9 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.
11 . An algae-resistant roofing shingle according to claim 7 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.
12 . An algae-resistant roofing shingle according to claim 11 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.
13 . An algae-resistant roofing shingle according to claim 1 further comprising coating the algaecide-bearing particles with a colorant composition.
14 . An algae-resistant roofing shingle according to claim 13 wherein the colorant composition includes a fusible binder, and further comprising heating the colorant-coated algaecide-bearing particles to fuse the binder.
15 . An algae-resistant roofing shingle, the shingle being produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a shingle stock material, the algae-resistant roofing granules being produced by a process comprising:
(a) mixing stone dust, a binder and at least one inorganic algaecide; and
(b) forming the mixture into particles by a forming process selected from press molding, cast molding, injection molding, extrusion, spray granulation, gel casting, and pelletizing.
16 . An algae-resistant roofing shingle according to claim 15 wherein the at least one inorganic algaecide is selected from the group consisting of copper materials, zinc materials, and mixtures thereof.
17 . An algae-resistant roofing shingle according to claim 16 wherein the inorganic algaecides are cuprous oxide and zinc oxide.
18 . An algae-resistant roofing shingle according to claim 15 , wherein the binder comprises an aluminosilicate material, and the process further comprises firing the particles in a kiln to insolubilize the binder.