Asphaltic membrane with mullite-containing granules
View Patent ↗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 granules disposed on a surface of the substrate, where said granules are mullite-containing granules that include mullite crystallites dispersed within a non-mullite phase, the granules including a mullite concentration of at least 35 wt. % and at most 63 wt. % as determined by quantitative x-ray diffraction, and where the mullite crystallites have a size of at least 25 nm and at most 65 nm as determined by x-ray diffraction line broadening by the isolated (110), and where the 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.
2. The article of claim 1 , 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.
3. The article of claim 1 , wherein the mullite crystallites have an aspect ratio of at least 1.7.
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 composition of claim 1 , wherein the chemical composition of the granules includes less than 3.5 wt. % alkali oxides or alkaline earth oxides combined.
7. The composition of claim 1 , wherein the chemical composition of the granules includes less than 1.0 wt. % alkali oxides or alkaline earth oxides combined.
8. The membrane of claim 1 , wherein the plurality of granules covers at least 95% of the asphaltic substrate surface.
9. The article of claim 1 , where said mullite-containing granules include mullite crystallites dispersed within a matrix that includes non-mullite aluminosilicates or non-mullite siliceous materials.
10. The article of claim 1 , where the granules include at least 40 wt. % alumina and at most 50 wt. % alumina.
11. The article of claim 10 , where the granules include at least 49 wt. % silica and at most 60 wt. % silica.
12. The article of claim 1 , where the granules include at least 42 wt % alumina and at most 45 wt % alumina.
13. The article of claim 12 , where the granules include at least 54 wt. % silica and at most 55 wt. % silica.
14. The article of claim 1 , where the non-mullite phase forms a matrix in which the crystallites are dispersed.
15. The article of claim 14 , where the amorphous material includes polymorphs of silica, amorphous silica, or combinations thereof.
16. The article of claim 14 , where the non-mullite phase is an amorphous phase.
17. The article of claim 16 , where the amorphous phase includes a glassy silica.
18. The article of claim 1 , where the granules have a number average particle size of at least 10 μm and less than 10 mm.
19. The article of claim 1 , where the granules have a size of from about −3½ to about +70 mesh.
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.
21. The membrane of claim 20 , where the non-mullite matrix includes non-mullite aluminosilicates or non-mullite siliceous materials.
22. The membrane of claim 20 , where the non-mullite matrix is amorphous.
23. The membrane of claim 22 , where the non-mullite matrix includes polymorphs of silica, amorphous silica, or combinations thereof.
24. The membrane of claim 20 , where the granules include at least 40 wt. % alumina and at most 50 wt. % alumina.
25. The membrane of claim 24 , where the granules include at least 49 wt. % silica and at most 60 wt. % silica.
26. The membrane of claim 20 , where the granules include at least 42 wt. % alumina and at most 45 wt. % alumina.
27. The membrane of claim 26 , where the granules include at least 54 wt. % silica and at most 55 wt. % silica.