Roofing granules with high solar reflectance, roofing products with high solar reflectance, and processes for preparing same

Abstract

Solar reflective roofing granules include a binder and inert mineral particles, with solar reflective particles dispersed in the binder. An agglomeration process preferentially disposes the solar reflective particles at a desired depth within or beneath the surface of the granules.

1 . A process for preparing solar reflective roofing granules, the process comprising:
 (a) providing a binder, inert mineral particles, and solar reflective particles;   (b) dispersing the inert mineral particles and the solar reflective particles in the binder to form a mixture;   (c) forming the mixture into uncured granules; and   (d) curing the binder to form cured roofing granules.   
   
   
       2 . A process according to  claim 1  further comprising selecting the solar reflective particles to provide at least 60 percent solar reflectance. 
   
   
       3 . (canceled) 
   
   
       4 . (canceled) 
   
   
       5 . A process according to  claim 1  further comprising surface treating the cured roofing granules. 
   
   
       6 . A process according to  claim 1  wherein the inert mineral particles comprise uncalcined kaolin, the binder comprises metal silicate, and the binder is cured by heating the uncured granules at from about 500 degrees C. to 800 degrees C. 
   
   
       7 . A process for preparing solar reflective roofing granules, the process comprising:
 (a) providing a binder and inert mineral particles to form a mixture;   (b) forming the mixture into uncured granule bodies having an exterior surface;   (c) adhering solar reflective particles to the exterior surface of the uncured granule bodies; and   (d) curing the binder.   
   
   
       8 . A process according to  claim 7  wherein the solar reflective particles are mechanically adhered to the exterior surface of the uncured granule bodies. 
   
   
       9 . A process according to  claim 7 , further comprising mixing the solar reflective particles with a fluid carrier to form a paste and adhering the solar reflective particles to the exterior surface of the granule bodies by applying the paste to the exterior surface of the granule bodies. 
   
   
       10 . (canceled) 
   
   
       11 . (canceled) 
   
   
       12 . A process according to  claim 7  further comprising surface treating the cured roofing granules. 
   
   
       13 . A process according to  claim 7  wherein the inert mineral particles comprise uncalcined kaolin, the binder comprises metal silicate, and the binder is cured by heating the uncured granules at from about 500 degrees C. to 800 degrees C. 
   
   
       14 . Solar reflective roofing granules comprising:
 (a) a binder;   (b) inert mineral particles; and   (c) solar reflective particles;   
     the inert mineral particles and the solar reflective particles being dispersed in the binder. 
   
   
       15 . Solar reflective roofing granules according to  claim 14  wherein the solar reflective particles are selected from the group consisting of titanium dioxides, metal pigments, titanates, and metal reflective pigments. 
   
   
       16 . Solar reflective roofing granules according to  claim 14  wherein the inert mineral particles have an average particle size from about 0.1 micrometers to 40 micrometers. 
   
   
       17 . (canceled) 
   
   
       18 . Solar reflective roofing granules according to  claim 14  having an average particle size from about 0.1 mm to 3 mm. 
   
   
       19 . (canceled) 
   
   
       20 . Solar reflective roofing granules according to  claim 14  wherein the binder is selected from the group consisting of silicate, silica, phosphate, titanate, zirconate, and aluminate binders, and mixtures thereof. 
   
   
       21 . Solar reflective roofing granules according to  claim 20  wherein the binder further comprises an inorganic material selected from the group consisting of aluminosilicate and kaolin clay. 
   
   
       22 . A roofing product comprising solar reflective roofing granules according to  claim 14 . 
   
   
       23 . Solar reflective roofing granules according to  claim 14  wherein the solar reflective particles are preferentially located on or near an exterior surface of the roofing granules. 
   
   
       24 . Solar reflective roofing granules according to  claim 14  wherein the solar reflective particles have a first concentration near an exterior surface of the roofing granules, and a second concentration in an interior zone within the granules, and the first concentration is greater than the second concentration. 
   
   
       25 . (canceled) 
   
   
       26 . (canceled) 
   
   
       27 . (canceled) 
   
   
       28 . (canceled) 
   
   
       29 . A process for preparing solar reflective roofing granules, the process comprising:
 (a) providing ceramic particles;   (b) forming the ceramic particles into uncured granule bodies having an exterior surface;   (c) mechanically adhering solar reflective particles to the exterior surface of the uncured granule bodies; and   (d) sintering the uncured granule bodies to form solar reflective roofing granules.   
   
   
       30 . (canceled) 
   
   
       31 . A process according to  claim 29  further comprising providing a sintering binder and mixing the sintering binder with the ceramic particles to form a mixture and subsequently forming the mixture including the ceramic particles into uncured granule bodies. 
   
   
       32 . (canceled) 
   
   
       33 . (canceled)