Asphaltic membrane with mullite-containing granules

Abstract

A roofing article comprising (i) an asphaltic substrate; and (ii) a plurality of mullite-containing granules disposed on a surface of the substrate, where said mullite-containing granules include a mullite concentration of at least 35 wt % and at most 63 wt % as determined by quantitative x-ray diffraction.

1 . A reflective roofing article, said roofing article comprising:
 (i) an asphaltic substrate; and   (ii) a plurality of mullite-containing granules disposed on a surface of the substrate, where said mullite-containing granules include a mullite concentration of at least 35 wt % and at most 63 wt % as determined by quantitative x-ray diffraction.   
     
     
         2 . The article of  claim 1 , where the mullite is in the form of crystallites having a size of at least 25 nm and at most 65 nm as determined by x-ray diffraction line broadening by the isolated (110) diffraction peak. 
     
     
         3 . The article of  claim 2 , wherein the mullite concentration is at least 45 wt % and at most 55 wt % as determined by quantitative x-ray diffraction, and the mullite crystallite size is at least 35 nm and at most 55 nm as determined by x-ray diffraction line broadening by the isolated (110) diffraction peak. 
     
     
         4 . The article of  claim 3 , wherein the said mullite crystallites have an aspect ratio of at least 1.5, where the aspect ratio is a ratio of the mullite crystallite size by the isolated (001) x-ray diffraction peak to the mullite crystallite size by the isolated (110) x-ray diffraction peak. 
     
     
         5 . The article of  claim 4 , wherein the said mullite crystallites have an aspect ratio of at least 1.7. 
     
     
         6 . The article of  claim 2 , where the mullite is calcined kaolin. 
     
     
         7 . The article of  claim 6 , wherein the calcined kaolin is thermally prepared at a calcination temperature of at least 1000° C. and at most 1300° C. 
     
     
         8 . The article of  claim 7 , wherein the calcined kaolin is thermally prepared at a calcination temperature of at least 1050° C. and at most 1200° C. 
     
     
         9 . The article of  claim 6 , wherein the calcined kaolin further includes crystalline polymorphs of silica, amorphous silica, or combinations thereof. 
     
     
         10 . The article of  claim 1 , wherein the article is a membrane in the form of a roll. 
     
     
         11 . The article of  claim 1 , wherein the article is a shingle. 
     
     
         12 . The composition of  claim 1 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 3.5 wt %. 
     
     
         13 . The composition of  claim 1 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 1.0 wt %. 
     
     
         14 . The membrane of  claim 1 , wherein the plurality of granules covers at least 95% of the bituminous substrate surface. 
     
     
         15 . A roofing article comprising:
 (i) an asphaltic substrate; and   (ii) a plurality of mullite-containing granules disposed on a surface of the substrate, said granules characterized by an grain size of about 0.05 μm.   
     
     
         16 . The membrane of  claim 15 , wherein the plurality of granules covers at least 95% of the surface of the substrate. 
     
     
         17 . A composition suitable for roofing granules characterized by a solar reflectance of at least 30%, wherein the composition is further characterized by a mullite phase content of at least 35 wt % and at most 60 wt % as determined by quantitative x-ray diffraction and a mullite crystallite size of at least 25 nm and at most 65 nm as determined by x-ray diffraction line broadening of the isolated (110) diffraction peak. 
     
     
         18 . The composition of  claim 17 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 3.5 wt %. 
     
     
         19 . The composition of  claim 18 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 1.0 wt %. 
     
     
         20 . An asphaltic membrane comprising:
 (i) an asphaltic substrate; and   (ii) a plurality of mullite-containing granules disposed on a planar surface of the substrate, where the mullite-containing granules include mullite-crystallites dispersed within a non-mullite matrix, and where the mullite-containing granules include less than 3.5 wt. % alkali oxides or alkaline earth oxides combined.