Roofing Granules, Roofing Products Including Such Granules, and Process for Preparing Same

Abstract

A coating composition including an inorganic sol material and an organic colorant is applied to mineral particles and cured at a temperature less than 200 degrees Celsius.

1 . A process for producing roofing granules, the process comprising:
 (a) providing base particles selected from particles comprising stone dust, the base particles having a solar reflectance of at least 10 percent and a reflectance to ultraviolet radiation of at least 80 percent;   (b) providing a sol-gel precursor material selected from tetra C 2 -C 5  alkyloxysilanes and C 1 -C 4 -alkyl-tri-C 2 -C 5 -alkyloxysilanes;   (c) acidifying the sol-gel precursor material to provide an intermediate material;   (d) adding base to the intermediate material to form a sol;   (e) forming a coating composition including the sol and at least one organic colorant;   (f) applying the coating composition to the base particles to form a coating layer on the base particles;   (g) curing the coating layer at a temperature less than 200 degrees Celsius to form a gel; and   (h) curing the gel to form an impervious coating layer.   
     
     
         2 . Roofing granules prepared according to the process of  claim 1 . 
     
     
         3 . Bituminous roofing materials including roofing granules according to  claim 2 . 
     
     
         4 . A process for producing roofing granules, the process comprising:
 (a) providing base particles;   (b) providing a first coating composition comprising an inorganic sol material and at least one first organic colorant;   (c) applying the first coating composition to the base particles to form a first coating layer on the base particles;   (d) curing the first coating layer at a temperature less than 200 degrees Celsius   (e) providing a second coating composition comprising an inorganic sol material and at least one second organic colorant;   (f) applying the second coating composition to the base particle having a first coating layer on the base particles; and   (g) curing the second coating layer at a temperature less than 200 degrees Celsius.   
     
     
         5 . Roofing granules prepared according to the process of  claim 4 . 
     
     
         6 . Bituminous roofing materials including roofing granules according to  claim 5 . 
     
     
         7 . A roofing granule comprising:
 (a) a base particle; and   (b) a first coating layer comprising an inorganic sol gel coating composition including at least one organic pigment.   
     
     
         8 . The roofing granule according to  claim 7  wherein the granule further comprises a second coating layer disposed on the base particle, the second coating layer being disposed on the first coating layer. 
     
     
         9 . Bituminous roofing materials including roofing granules according to  claim 7 . 
     
     
         10 . Bituminous roofing materials including roofing granules according to  claim 8 .