Algae resistant roofing system containing silver compounds, algae resistant shingles, and process for producing same
Algae-resistant roofing granules include inert base particles with an exterior coating including high-surface area silver as a biocide.
1. Algae-resistant roofing granules comprising:
(a) a base particle comprising an inert mineral;
(b) an exterior coating layer on the base particle, the exterior coating including biocidal particles selected from the group consisting of:
(1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.1 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds.
2. Algae-resistant roofing granules according to claim 1 wherein the biocidal particles materials include a core selected from the group consisting of:
(a) solid cores, the solid core being formed from at least one core material selected from the group consisting of metals and metal oxides, and
(b) hollow cores enclosed by a wall formed from glass or a ceramic material.
3. Algae-resistant roofing granules according to claim 1 wherein the exterior coating layer includes a binder selected from the group consisting of silicaceous coating binders and organic polymeric materials.
4. Algae-resistant roofing granules according to claim 1 wherein the silver biocide comprises from about 0.005 percent to about 5 percent by weight of the granules.
5. Algae-resistant roofing granules according to claim 1 wherein the silver biocide has a surface area of at least 1 square meter per gram of biocide.
6. A sheet roofing product including a bituminous base and algae-resistant roofing granules, the granules comprising:
(a) a base particle comprising an inert mineral;
(b) an exterior coating layer on the base particle, the exterior coating including biocidal particles selected from the group consisting of:
(1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.1 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds.
7. A sheet roofing product according to claim 6 wherein the biocidal particles include a core selected from the group consisting of:
(a) solid cores, the solid core being formed from at least one core material selected from the group consisting of metals and metal oxides, and
(b) hollow cores enclosed by a wall formed from glass or a ceramic material.
8. A sheet roofing product according to claim 6 wherein the exterior coating layer includes a binder selected from the group consisting of silicaceous coating binders and organic polymeric materials.
9. A sheet roofing product according to claim 6 wherein the silver biocide comprises from about 0.005 percent to about 5 percent by weight of the granules.
10. A sheet roofing product according to claim 6 wherein the silver biocide has a surface area of at least 1 square meter per gram of biocide.
11. A sheet roofing product including:
(a) a bituminous base including an upper layer formed from an asphaltic material, and
(b) biocidal particles embedded in the upper layer, the biocidal particles being selected from the group consisting of:
(1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.1 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds.
12. A sheet roofing product according to claim 11 wherein the biocidal particles include a core selected from the group consisting of:
(a) solid cores, the solid core being formed from at least one core material selected from the group consisting of metals and metal oxides, and
(b) hollow cores enclosed by a wall formed from glass or a ceramic material.
13. A sheet roofing product according to claim 11 wherein the exterior coating layer includes a binder selected from the group consisting of silicaceous coating binders and organic polymeric materials.
14. A sheet roofing product according to claim 11 wherein the silver biocide has a surface area of at least 1 square meter per gram of biocide.
15. A sheet roofing product including:
(a) a bituminous base including an upper layer formed from an asphaltic material, and
(b) a surface coating applied to the upper layer, the surface coating including biocidal particles selected from the group consisting of:
(1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.5 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds.
16. A sheet roofing product according to claim 15 wherein the biocidal particles include a core selected from the group consisting of:
(a) solid cores, the solid core being formed from at least one core material selected from the group consisting of metals and metal oxides, and
(b) hollow cores enclosed by a wall formed from glass or a ceramic material.
17. A sheet roofing product according to claim 15 wherein the exterior coating layer includes a binder selected from the group consisting of silicaceous coating binders and organic polymeric materials.
18. A sheet roofing product according to claim 15 wherein the surface coating includes a binder subject to controlled environmental degradation.
19. A sheet roofing product according to claim 15 wherein the silver biocide has a surface area of at least 1 square meter per gram of biocide.
20. A process for preparing algae-resistant roofing granules, the process comprising:
(a) providing base particles comprising inert material;
(b) coating the base particles with an exterior coating composition, the exterior coating composition comprising biocidal particles selected from the group consisting of:
(1) biocidal particles having an average size from about 0.1 micrometers to about 5 millimeters and having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(2) microcapsules having an average size from about 200 micrometers and 5 millimeters, and having a capsule wall environmentally degradable in a controlled manner and a core comprising a plurality of biocidal particles having an average size from about 0.1 micrometers to about 0.5 millimeters, the biocidal particles having a surface coating comprising at least one silver biocide selected from the group consisting of metallic silver and silver compounds; and
(c) curing the exterior coating composition.
21. A sheet roofing product according to claim 12 wherein the core is selected from the group consisting of titanium dioxide and zinc oxide.
22. A sheet roofing product according to claim 16 wherein the core is selected from the group consisting of titanium dioxide and zinc oxide.