Roofing Granules, Roofing Products Including Such Granules, and Process for Preparing Same

1 . A process for producing roofing granules, the process comprising:

(a) providing base particles selected from particles comprising stone dust, the base particles having a solar reflectance of at least 10 percent and a reflectance to ultraviolet radiation of at least 80 percent;

(b) providing a sol-gel precursor material selected from tetra C 2 -C 5 alkyloxysilanes and C 1 -C 4 -alkyl-tri-C 2 -C 5 -alkyloxysilanes;

(c) acidifying the sol-gel precursor material to provide an intermediate material;

(d) adding base to the intermediate material to form a sol;

(e) forming a coating composition including the sol and at least one organic colorant;

(f) applying the coating composition to the base particles to form a coating layer on the base particles;

(g) curing the coating layer at a temperature less than 200 degrees Celsius to form a gel; and

(h) curing the gel to form an impervious coating layer.

2 . Roofing granules prepared according to the process of claim 1 .

3 . Bituminous roofing materials including roofing granules according to claim 2 .

4 . A process for producing roofing granules, the process comprising:

(a) providing base particles;

(b) providing a first coating composition comprising an inorganic sol material and at least one first organic colorant;

(c) applying the first coating composition to the base particles to form a first coating layer on the base particles;

(d) curing the first coating layer at a temperature less than 200 degrees Celsius

(e) providing a second coating composition comprising an inorganic sol material and at least one second organic colorant;

(f) applying the second coating composition to the base particle having a first coating layer on the base particles; and

(g) curing the second coating layer at a temperature less than 200 degrees Celsius.

5 . Roofing granules prepared according to the process of claim 4 .

6 . Bituminous roofing materials including roofing granules according to claim 5 .

7 . A roofing granule comprising:

(a) a base particle; and

(b) a first coating layer comprising an inorganic sol gel coating composition including at least one organic pigment.

8 . The roofing granule according to claim 7 wherein the granule further comprises a second coating layer disposed on the base particle, the second coating layer being disposed on the first coating layer.

9 . Bituminous roofing materials including roofing granules according to claim 7 .

10 . Bituminous roofing materials including roofing granules according to claim 8 .