Post-functionalized roofing granules and process for preparing same

Abstract

Roofing granules having a color coating layer are covered with a clear, transparent or translucent outer coating composition including a functional material, such nanoparticles of anatase titanium dioxide.

1 . Functionalized roofing granules comprising:
 (a) base roofing granules having a first coating layer, the first coating layer including at least one coloring material; and   (b) a cured clear or transparent outer coating layer comprising an outer coating binder and at least one photocatalytic functional material, wherein said photocatalytic functional material comprises at least one photocatalytic metal oxide selected from a group consisting of titanium oxide, copper oxide and zinc oxide.   
     
     
         2 . Functionalized roofing granules according to  claim 1  wherein the outer coating binder is selected from the group consisting of binders including at least one alkali metal silicate, binders including at least one alkaline earth metal silicate, binders including colloidal silica, binders including at least one metal phosphate, binders including at least one titanate, binders including at least one zirconate, and binders including at least one organic polymer. 
     
     
         3 . Functionalized roofing granules according to  claim 1  wherein the at least one photocatalytic functional material is a particulate having an average particle size less than 0.2 microns. 
     
     
         4 . Functionalized roofing granules according to  claim 1  wherein the at least one photocatalytic functional particulate material has biocidal activity. 
     
     
         5 . Functionalized roofing granules according to  claim 1  wherein the outer coating layer comprises a colloidal silica binder and photocatalytic anatase titanium dioxide dispersed in the binder. 
     
     
         6 . Functionalized roofing granules according to  claim 2  wherein said binder is a binder including at least one organic polymer selected from the group consisting of polyurethane polymers, acrylic polymers, polyurea polymers, silicone polymers, siliconized polymers, and sulfourethane silanol-based polymers, and their respective copolymers or mixtures hereof. 
     
     
         7 . Functionalized roofing granules according to  claim 1  wherein said binder comprises a vitreous silica material in which said photocatalytic functional material is dispersed. 
     
     
         8 . Functionalized roofing granules according to  claim 7  wherein said vitreous silica material is a vitreous glaze formed from material selected from a vitreous flux, particulate silica glass, or a mixture thereof. 
     
     
         9 . Functionalized roofing granules according to  claim 1  further comprising a second coating layer intermediate first coating layer and said outer coating layer. 
     
     
         10 . Functionalized roofing granules according to  claim 9  wherein the second coating layer comprises silicon dioxide. 
     
     
         11 . Functionalized roofing granules according to  claim 10  wherein the outer coating layer comprises a colloidal silica binder and photocatalytic anatase titanium dioxide dispersed in the binder. 
     
     
         12 . Functionalized roofing granules according to  claim 1  wherein said at least one coloring material includes an organic compound or ligand. 
     
     
         13 . Functionalized roofing granules according to  claim 1  wherein said photocatalytic functional material is photocatalytic anatase titanium dioxide. 
     
     
         14 . Functionalized roofing granules according to  claim 10  wherein said at least one coloring material includes an organic compound or ligand. 
     
     
         15 . Functionalized roofing granules according to  claim 10  wherein said photocatalytic functional material is photocatalytic anatase titanium dioxide.