Biocidal roofing granules, roofing products including such granules, and process for preparing same

Abstract

Biocidal roofing granules include a mineral core covered with an outer layer of mesoporous silica including photocatalytic nanoparticles of anatase titanium dioxide as a biocide and an optional organic biocide.

1 . Biocidal roofing granules comprising: 
 a mineral core; and    an exterior coating covering the mineral core; and    at least one biocidal photocatalytic metal oxide;    the exterior coating including at least one porous layer having a network of pores formed therein; and    the porous inorganic layer containing the at least one biocidal photocatalytic metal oxide in the network of pores.    
   
   
       2 . Biocidal roofing granules according to  claim 1 , wherein the at least one porous layer comprises an inorganic material selected from the group consisting of silica, alumina, zirconia and titania, and mixtures thereof.  
   
   
       3 . Biocidal roofing granules according to  claim 2 , wherein the at least one porous layer has an average pore diameter of between 1 nm and 100 nm.  
   
   
       4 . Biocidal roofing granules according to  claim 1 , wherein the at least one porous layer has a total pore volume of at least 0.5×10 −3  cm 3 /g and less than 0.1 cm 3 /g for pores having an average diameter less than 100 nm.  
   
   
       5 . Biocidal roofing granules according to  claim 4 , wherein the at least one porous layer has a total pore volume of between 0.7×10 −3  cm 3 /g and 1×10 −2  cm 3 /g for pores having an average diameter less than 76 nm.  
   
   
       6 . Biocidal roofing granules according to  claim 1 , wherein the at least one porous layer has an average thickness no greater than about 40 μm.  
   
   
       7 . Biocidal roofing granules according to  claim 1 , wherein the at least one porous layer has an average thickness between about 0.5 μm and 10 μm.  
   
   
       8 . Biocidal roofing granules according to  claim 1 , wherein the at least one porous layer has an average thickness between about 1 μm and 5 μm.  
   
   
       9 . Biocidal roofing granules according to  claim 1 , wherein the photocatalytic metal oxide is selected from the group consisting of photocatalytic titanium oxide, photocatalytic copper oxide, photocatalytic vanadium oxide, and photocatalytic zinc oxide, and mixtures thereof.  
   
   
       10 . Biocidal roofing granules according to  claim 9  further comprising at least one metal selected from the group consisting of Pt, Au, Os, Pd, Ni, Sn, Cu, Fe, Mn, Rh, Nb, and Ru, and mixtures thereof.  
   
   
       11 . Biocidal roofing granules according to  claim 1 , wherein the photocatalytic metal oxide comprise from about 0.1 to 10 percent by weight of the exterior covering.  
   
   
       12 . Biocidal roofing granules according to  claim 1 , wherein said granules further comprise a second biocidal composition selected from the group consisting of inorganic biocides and organic biocides.  
   
   
       13 . A process for preparing biocidal roofing granules, the process comprising: 
 (a) providing a mineral core;    (b) preparing a gel-forming inorganic coating medium;    (c) providing at least one biocidal photocatalytic metal oxide;    (d) coating the mineral core with the inorganic sol;    (e) forming a porous coating layer on the mineral core from the inorganic sol, the porous coating layer having a pore network; and    (f) disposing the at least one photocatalytic metal oxide in the pore network.    
   
   
       14 . A process according to  claim 13  wherein the gel-forming inorganic coating medium is selected from the group consisting of silica sol-gels, colloidal silica media, colloidal zirconia media, colloidal titania media, and colloidal alumina media  
   
   
       15 . A process according to  claim 13  wherein the coating medium is an aqueous suspension prepared from at least one precursor selected from the group consisting of alkylsilanes, alkoxysilanes, zirconium oxychloride, zirconium alkoxides, titanium chloride, titanium alkoxides, aluminum chloride, aluminum alkoxides, sodium silicate, potassium silicate, pyrogenic silica, pyrogenic alumina, pyrogenic titania, pyrogenic zirconia, and mixtures thereof.  
   
   
       16 . A process according to  claim 15  wherein the at least one precursor is selected from the group consisting of tetramethoxysilane, tetraethoxysilane, and methyl triethoxysilane.  
   
   
       17 . A process according to  claim 13 , wherein the coating medium further comprises the at least one biocidal photocatalytic material.  
   
   
       18 . A process according to  claim 13  wherein the biocidal roofing granules further comprise a second biocidal composition selected from the group consisting of inorganic biocides and organic biocides  
   
   
       19 . A process according to  claim 13  wherein the porous coating network is formed by drying the coating medium.  
   
   
       20 . A process according to  claim 13  wherein the coating medium further comprises at least one sacrificial template material.  
   
   
       21 . A process according to  claim 20  wherein the sacrificial template material is selected from the group consisting of multiblock polyalkylene oxide materials, polyvinyl alcohol, and quaternary ammonium salts.  
   
   
       22 . A process according to  claim 20  wherein the sacrificial template material is a polyethyleneoxide-polypropyleneoxide-polyethyleneoxide triblock material.  
   
   
       23 . A process according to  claim 20  wherein the sacrificial template material is cetyl trimethylammonium bromide.  
   
   
       24 . A process according to  claim 19  wherein the coating medium is dried out at a temperature between about 10 and 100° C., preferably between 20 and 80° C.  
   
   
       25 . A process according to  claim 13 , wherein the coating medium further includes a sacrificial template material, and wherein forming the porous network comprises calcining the sol at a temperature from about 200° C. to 1000° C., before disposing the at least one photocatalytic metal oxide in the porous network.  
   
   
       26 . A process according to  claim 25  wherein the sacrificial template material is an organic polymer.  
   
   
       27 . A process according to claims  13  wherein the at least one photocatalytic metal oxide is disposed in the porous inorganic layer by applying a suspension of the at least one photocatalytic material in a liquid carrier material to the porous inorganic layer, and evaporating the carrier material.  
   
   
       28 . A roofing shingle including roofing granules according to  claim 1 .  
   
   
       29 . A roofing shingle according to  claim 28  wherein the mass of roofing granules per unit of area is between about 0.5 and 2.5 kg/m 2 .  
   
   
       30 . A roofing shingle according to  claim 29 , wherein the roofing granules including the at least one photocatalytic metal oxide comprise from about 0.1% to 10% by weight of the total weight of roofing granules.  
   
   
       31 . A roofing product including a biocidal coating, the roofing product comprising: 
 a base material; and    an exterior coating covering the base material;    the exterior coating including at least one porous layer having a network of pores formed therein;    the porous inorganic layer containing at least one biocidal photocatalytic metal oxide in the network.    
   
   
       32 . A roofing product according to  claim 31 , wherein the at least one porous layer comprises an inorganic material selected from the group consisting of silica, alumina, zirconia and titania, and mixtures thereof.  
   
   
       33 . A roofing product according to  claim 31 , wherein the porous layer has an average pore diameter of between 1 nm and 100 nm.  
   
   
       34 . A roofing product according to  claim 31 , wherein the at least one porous layer has a total pore volume of at least 0.5×10 −3  cm 3 /g and less than 0.1 cm 3 /g for pores having an average diameter less than 100 nm.  
   
   
       35 . A roofing product according to  claim 31 , wherein the at least one porous layer has a total pore volume of between 0.7×10 −3  and 1×10 −2  cm 3 /g for pores having an average diameter less than 76 nm.  
   
   
       36 . A roofing product according to  claim 31 , wherein the at least one porous layer has an average thickness no greater than about 40 μm.  
   
   
       37 . A roofing product according to  claim 31 , wherein the at least one porous layer has an average thickness between about 0.5 μm and 10 μm.  
   
   
       38 . A roofing product according to  claim 31 , wherein the at least one porous layer has an average thickness between about 1 μm and 5 μm.  
   
   
       39 . A roofing product according to  claim 31 , wherein the photocatalytic metal oxide is selected from the group consisting of photocatalytic titanium oxide, photocatalytic copper oxide, photocatalytic vanadium oxide, and photocatalytic zinc oxide, and mixtures thereof.  
   
   
       40 . A roofing product according to  claim 31  further comprising a metal selected from the group consisting of Pt, Au, Os, Pd, Ni, Sn, Cu, Fe, Rh, Nb, and Ru, and mixtures thereof.  
   
   
       41 . A roofing product according to  claim 31 , wherein the photocatalytic metal oxide comprise from about 0.1 to 10 percent by weight of the exterior covering.  
   
   
       42 . A roofing product according to  claim 31 , wherein the biocidal coating further comprises a second biocidal composition selected from the group consisting of inorganic biocides and organic biocides.  
   
   
       43 . A roofing product according to  claim 31 , wherein the base material is selected from the group consisting of roofing shingles, roofing membranes and roofing granules.  
   
   
       44 . A process for preparing roofing materials, the process comprising: 
 (a) providing a base material;    (b) preparing a gel-forming inorganic coating medium;    (c) providing at least one biocidal photocatalytic metal oxide;    (d) coating the base material with the inorganic coating medium;    (e) forming a porous coating layer on the mineral core from the inorganic coating medium, the porous coating layer having a pore network; and    (f) disposing the at least one photocatalytic metal oxide in the pore network.    
   
   
       45 . A process according to  claim 44  wherein the gel-forming inorganic coating medium is selected from the group consisting of silica sol-gels, colloidal silica media, colloidal zirconia media, colloidal titania media, and colloidal alumina media  
   
   
       46 . A process according to  claim 44  wherein the coating medium is an aqueous suspension prepared from at least one precursor selected from the group consisting of alkylsilanes, alkoxysilanes, zirconium oxychloride, zirconium alkoxides, sodium silicate, potassium silicate, titanium chloride, titanium alkoxides, aluminum chloride, aluminum alkoxides, pyrogenic silica, pyrogenic alumina, pyrogenic titania, pyrogenic zirconia, and mixtures thereof.  
   
   
       47 . A process according to  claim 46  wherein the at least one precursor is selected from the group consisting of tetramethoxysilane, tetraethoxysilane, and methyl triethoxysilane.  
   
   
       48 . A process according to  claim 46 , wherein the coating medium further comprises the at least one biocidal photocatalytic metal oxide.  
   
   
       49 . A process according to  claim 46  wherein the porous coating network is formed by drying the coating medium.  
   
   
       50 . A process according to  claim 46  wherein the coating medium further comprises at least one sacrificial template material.  
   
   
       51 . A process according to  claim 50  wherein the sacrificial template material is selected from the group consisting of multiblock polyalkylene oxide materials, polyvinyl alcohol, and quaternary ammonium salts.  
   
   
       52 . A process according to  claim 50  wherein the sacrificial template material is a polyethyleneoxide-polypropyleneoxide-polyethyleneoxide triblock material.  
   
   
       53 . A process according to  claim 50  wherein the sacrificial template material is cetyl trimethylammonium bromide.  
   
   
       54 . A process according to  claim 46  wherein the coating medium further comprises a second biocidal composition selected from the group consisting of inorganic biocides and organic biocides.  
   
   
       55 . A process according to  claim 46  wherein the coating medium is dried out at a temperature between about 10 and 100° C.  
   
   
       56 . A process according to  claim 55  wherein the coating medium is dried out a temperature between about 20 and 80° C.  
   
   
       57 . A process according to  claim 55  wherein the coating medium comprises a sacrificial template and the sacrificial template material comprises an organic polymer.  
   
   
       58 . A process according to  claim 55  wherein the at least one photocatalytic metal oxide is disposed in the porous inorganic layer by applying a suspension of the at least one photocatalytic material in a liquid carrier material to the porous inorganic layer, and evaporating the carrier material.  
   
   
       59 . A process according to  claim 46  wherein the base material is selected from roofing shingles, roofing membranes and roofing granules.