Silicate coated roofing granules

Claim 2

A roofing granule comprising a base mineral granule substrate having a dehydrated, pigmented, moisture permeable, substantially water insoluble sodium silicate kaolin clay coating, said coating comprising an opaque, solid matrix having a layered plate-like structure aligned parallel with the substrate and containing light scattering closed voids uniformly and individually dispersed therein to thereby enhance the opacity of the coating, said voids also having a plate-like shape and being aligned parallel with the substrate with at least a majority of the voids being between about 0.05 and about 0.5 micron thick.

Claim 3

A roofing granule comprising a base mineral granule having a coating comprising insolubilized reaction product of a mixture of: (a) water; (b) kaolin clay; (c) sodium silicate; and (d) inorganic gas forming compound which is soluble in said mixture and decomposes to gaseous products below about 500° F. when dispersed in an alkaline silicate film.

Claim 4

A roofing granule comprising a base mineral granule having a coating comprising insolubilized reaction product of a mixture of: (a) water; (b) kaolin clay; (c) sodium silicate; and (d) inorganic gas forming compound which is soluble in said mixture and decomposes to gaseous products below about 500° F. when dispersed in an alkaline silicate film.

Claim 5

A roofing granule according to claim 2 wherein the gas forming compound is hydrogen peroxide or an alkali metal perborate.

Claim 6

A roofing granule according to claim 2 wherein the gas forming compound comprises sodium perborate and wherein boric acid is also present in an amount between about 50 and about 150 wt% based on sodium perborate.

Claim 7

A roofing granule according to claim 2 wherein clay is present in an amount between about 45 and about 65 wt% based on total coating on a dry basis.

Claim 8

A roofing granule according to claim 2 wherein sodium silicate is present in the coating composition in an amount between about 30 and about 40 wt% based on total coating composition on a dry basis and water is present in the coating composition in an amount between about 40 and about 60 wt% based on total coating composition.

Claim 9

A roofing granule according to claim 2 wherein the gas forming compound is selected from the group consisting of hydrogen peroxide, alkali metal perborates, alkali metal persulfates, alkali metal borohydrides, and alkali metal azides.

Claim 10

A roofing granule according to claim 2 wherein: (a) the gas forming compound is hydrogen peroxide or sodium perborate and is present in the coating composition in an amount between about 0.25 and about 2.5 wt% based on dry weight of the coating composition; (b) clay is present in an amount between about 45 and about 65 wt% based on coating composition on a dry basis; (c) sodium silicate is present in an amount between about 30 and about 40 wt% based on total coating on a dry basis; (d) water is present in an amount between about 40 and about 60 wt% based on coating composition; and (e) titanium dioxide is present in an amount between about 1 and about 5 wt% based on total coating on a dry basis.

Claim 11

A roofing granule according to claim 2 wherein gas forming compound is present in the coating composition in an amount between about 0.25 and about 2.5 wt% based on dry weight of the total coating composition.

Claim 12

A roofing granule according to claim 9 wherein the gas forming compound is hydrogen peroxide or sodium perborate.

Claim 13

A roofing granule according to claim 2 wherein pigment is also present in the coating composition in an amount between about 0.5 and about 10 wt% based on total coating composition on a dry basis.

Claim 14

A roofing granule according to claim 11 wherein the pigment is titanium dioxide and is present in the coating composition in an amount between about 1 and about 5 wt% based on total coating composition on a dry basis.