Roofing granule mixtures for algae-resistant roofing shingles

Abstract

The present disclosure relates generally to a roofing granule mixture, the mixture comprising a first class of roofing granules consisting of non-algae-resistant roofing granules, and a second class of roofing granules consisting of algae-resistant roofing granules having a d50 particle size of at most 0.9 mm.

We claim: 
     
         1 . A roofing granule mixture, the mixture consisting of:
 a first class of roofing granules consisting of non-algae-resistant roofing granules; and   a second class of roofing granules consisting of algae-resistant roofing granules having a d50 particle size of at most 0.9 mm.   
     
     
         2 . The roofing granule mixture of  claim 1 , wherein the first class of roofing granules has a d50 particle size in the range of 1 mm to 5 mm. 
     
     
         3 . The roofing granule mixture of  claim 1 , wherein the first class of roofing granules has a d50 particle size in the range of 1.5 mm to 5 mm. 
     
     
         4 . The roofing granule mixture of  claim 1 , wherein the first class of roofing granules is present in an amount in the range of 70-99 wt % of the total mixture\. 
     
     
         5 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d50 particle size of at most 0.8 mm. 
     
     
         6 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d50 particle size of at most 0.5 mm. 
     
     
         7 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d10 particle size of at least 0.1 mm. 
     
     
         8 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d90 particle size of at most 1.0 mm. 
     
     
         9 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d50 particle size that is no more than 60% of the d50 particle size of the first class of roofing granules. 
     
     
         10 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules has a d50 particle size that is no more than 40% of the d50 particle size of the first class of roofing granules. 
     
     
         11 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules are present in an amount in the range of 1-30 wt % of the total mixture. 
     
     
         12 . The roofing granule mixture of  claim 1 , wherein the second class of roofing granules comprises an organic algaecide, an inorganic algaecide, or combinations thereof. 
     
     
         13 . The roofing granule mixture of  claim 1 , wherein each of the second class of roofing granules comprise an organic algaecide. 
     
     
         14 . The roofing granule mixture of  claim 1 , wherein each of the second class of roofing granules comprise an inorganic algaecide, wherein the inorganic algaecide of the second class of roofing granules is selected from the group consisting of copper species, zinc species, silver species and anatase titanium oxide. 
     
     
         15 . The roofing granule mixture of  claim 14 , wherein the inorganic algaecide of the second class of roofing granules is a copper species. 
     
     
         16 . The roofing granule mixture of  claim 14 , wherein the algaecide is present in the second class of roofing granule in the range of 1 wt % to 15 wt % of the granule mass. 
     
     
         17 . A method of producing a mixture of roofing granules accordingly to  claim 1  comprising:
 providing a plurality of base particles; 
 splitting the plurality of base particles into a first batch and a second batch,
 wherein the second batch of base particles have a d50 particle size of at most 0.9 mm; 
 
 applying a first top coat to the first batch to form a first class of roofing granules, wherein the first top coat comprises at least one colorant; 
 applying a second top coat to the second batch to form a second class of roofing granules, wherein the second top coat comprises at least one algaecide and at least one colorant; and 
 blending the first class of roofing granules and the second class of roofing granules,
 wherein the second class of roofing granules are present in an amount in the range of 1-30 wt % of the total mixture. 
 
 
     
     
         18 . The method of  claim 17 , wherein the splitting is performed by sieving, with base particles retained by a sieve being in the first batch, and base particles passing through the sieve being in the second batch. 
     
     
         19 . An algae-resistant roofing shingle comprising:
 a shingle substrate; and   adhered to a top surface of the shingle substrate, the roofing granule mixture according to  claim 1 .   
     
     
         20 . A method for producing an algae-resistant roofing shingle comprising:
 providing a shingle substrate; and   adhering to a top surface of the shingle substrate the roofing granule mixture according to  claim 1 .