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.

Description

[0001]This application is a Continuation Application of International Application Serial No. PCT / US2011 / 020044, filed on Jan. 3, 2011, which claims the benefit of U.S. Provisional Application Ser. No. 61 / 291,546, filed on Dec. 31, 2009, both of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]Embodiments of the present invention are directed toward roofing articles that carry (i.e. are coated with) mullite-containing granules.BACKGROUND OF THE INVENTION[0003]Asphaltic roofing membranes, also known as bituminous membranes, have been employed to cover flat or low-sloped roofs. These membranes are typically installed by unrolling a roll of material on a roof surface and then heat seaming adjacent membranes together to form an impervious water barrier on the roof surface.[0004]As part of the manufacturing process, the asphaltic roofing membranes are often coated with granular material. Among the benefits associated with the use of these granules is the ability to r...

AI Technical Summary

Benefits of technology

The present invention provides a roofing article comprising a substrate and granules made of calcined kaolin and mullite-containing granules on the surface of the substrate. The grain size of the granules is between 0.01 μm and 5 μm and the granules have a calumina content between 35 wt % and 55 wt % and a silica content between 45 wt % and 65 wt%. This roofing article has improved heat resistance and fire retardant properties. It also has improved solar reflectance, with a mullite phase content of at least 35 wt % and a mullite crystallite size of at least 25 nm and at most 65 nm. The present invention also provides a composition suitable for roofing granules with a solar reflectance of at least 30% and a mullite phase content of at least 35 wt % and a mullite crystallite size of at least 25 nm and at most 65 nm.

Problems solved by technology

However, as further stated in U.S. Pat. No. 6,933,007, kaolin clay alone lacks the brightness and opacity needed to hide the dark underlying base rock of the granule and frequently require appreciable amounts of TiO2 to achieve desired color specifications.

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