Asphaltic membrane with mullite-containing granules

Abstract

A roofing article comprising (i) an asphaltic substrate; and (ii) a plurality of granules disposed on a surface of the substrate, said granules including calcined kaolin that has been calcined at a temperature of at least 1000° C. and less than 1300° C.

1 . A roofing article comprising:
 (i) an asphaltic substrate; and   (ii) a plurality of granules disposed on a surface of the substrate, said granules including calcined kaolin that has been calcined at a temperature of at least 1000° C. and less than 1300° C.   
     
     
         2 . The article of  claim 1 , where the calcined kaolin has been calcined at a temperature of at least 1050° C. and less than 1250° C. 
     
     
         3 . The article of  claim 1 , where the calcined kaolin has been calcined at a temperature of at least 1100° C. and less than 1200° C. 
     
     
         4 . The article of  claim 1 , wherein the article is a membrane in the form of a roll. 
     
     
         5 . The article of  claim 1 , wherein the article is a shingle. 
     
     
         6 . The article of  claim 1 , wherein the plurality of granules covers at least 95% of the bituminous substrate surface. 
     
     
         7 . A roofing article comprising:
 (i) an asphaltic substrate; and   (ii) a plurality of granules disposed on a surface of the substrate, said granules characterized by an grain size of at least 0.01 μm and less than 5 μm, an alumina content of at least 35 wt % and less than 55 wt %, and a silica content of at least 45 wt % and less than 65 wt %.   
     
     
         8 . The article of  claim 7 , wherein the plurality of granules covers at least 95% of the surface of the substrate. 
     
     
         9 . 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.   
     
     
         10 . 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 x-ray diffraction, and where the mullite is in the form of crystallites having an average size of at least 25 nm and at most 65 nm, as determined by the isolated (110) x-ray diffraction peak.   
     
     
         11 . The article of  claim 10 , wherein the mullite concentration is at least 45 wt % and at most 55 wt % as determined by x-ray diffraction, and the average mullite crystallite size is at least 35 nm and at most 55 nm as determined by the isolated (110) x-ray diffraction peak. 
     
     
         12 . The article of  claim 10 , wherein the said mullite crystallites have an aspect ratio of at least 1.5, where the aspect ratio is a ratio of the average mullite crystallite size by the isolated (001) x-ray diffraction peak to the mullite crystallite size by the isolated (110) x-ray diffraction peak. 
     
     
         13 . The article of  claim 10 , wherein the said mullite crystallites have an aspect ratio of at least 1.7. 
     
     
         14 . The article of  claim 10 , where the mullite is calcined kaolin. 
     
     
         15 . The article of  claim 14 , wherein the calcined kaolin is thermally prepared at a calcination temperature of at least 1000° C. and at most 1300° C. 
     
     
         16 . The article of  claim 15 , wherein the calcined kaolin is thermally prepared at a calcination temperature of at least 1050° C. and at most 1200° C. 
     
     
         17 . The article of  claim 10 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 3.5 wt %. 
     
     
         18 . The article of  claim 17 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 1.0 wt %. 
     
     
         19 . The article of  claim 18 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 3.5 wt %. 
     
     
         20 . The article of  claim 19 , wherein the chemical composition of the granules includes a total alkali and alkaline earth content of at most 1.0 wt %. 
     
     
         21 . 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.