Algae resistant roofing granules with controlled algaecide leaching rates, algae resistant shingles and process for producing same

Abstract

Algae-resistant roofing shingles are prepared with granules are formed by coating mineral particles with a clay-silicate binder including a metal oxide algaecide and small organic particles. When the particles are heated to cure the binder, the organic particles pyrolyse to form pores in the coating. Release of the algaecide is controlled by the structure of the granules.

1 . An algae-resistant roofing product produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a roofing product stock material, the algae-resistant roofing granules being produced by a process comprising:
 (a) providing inert base particles;   (b) forming first intermediate particles by coating the inert base particles with a first mixture including at least one algaecidal material comprising cuprous oxide, and a void-forming material, the void-forming material releasing gaseous material at temperatures above 90 degrees C., and having an average particle size no larger than 2 mm, to form a first layer on the inert base particles;   (c) forming second intermediate particles by coating the first intermediate particles with a second mixture including a binder and a coloring material and not including a void-forming material; and   (d) heating the second intermediate particles to release the gaseous material and form pores in the first layer to produce the roofing granules   
     
     
         2 .- 14 . (canceled) 
     
     
         15 . An algae-resistant roofing product produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a roofing product stock material, the algae-resistant roofing granules being produced by a process comprising:
 (a) providing inert base particles;   (b) forming first intermediate particles by coating the inert base particles with a first mixture including; a binder; at least one algaecidal material, and a void-forming material, the void-forming material releasing gaseous material at temperatures above 90 degrees C., and having an average particle size no larger than 2 mm, to form a first layer on the inert base particles;   (c) forming second intermediate particles by coating the first intermediate particles with a second mixture including a binder and a coloring material and not including a void-forming material to form a second coating having a thickness of from about 2 micrometers to about 25 micrometers; and   (d) heating the second intermediate particles to release the gaseous material and form pores in the first layer to produce the roofing granules.   
     
     
         16 .- 28 . (canceled) 
     
     
         29 . An algae-resistant roofing product produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a roofing product stock material, the algae-resistant roofing granules being produced by a process comprising:
 (a) providing inert base particles;   (b) forming green granules by coating the inert base particles with a mixture including;
 at least one algaecidal material, and 
 a void-forming material, the void-forming material releasing gaseous material at temperatures above 90° C., and having an average particle size no larger than 2 mm, 
 at least one coloring material; and 
 a heat curable binder; and 
   (c) heating the green granules to release the gaseous material to form pores and cure the binder to produce the roofing granules.   
     
     
         30 . An algae-resistant roofing product produced by a process comprising producing algae-resistant roofing granules, and adhering the granules to a roofing product stock material, the algae-resistant roofing granules being produced by a process comprising:
 (a) providing inert base particles;   (b) forming first intermediate particles by coating the inert base particles with a first mixture including at least one algaecidal material, and a void-forming material, the void-forming material releasing gaseous material at temperatures above 90° C., and having an average particle size no larger than 2 mm, to form a first layer on the inert base particles;   (c) forming second intermediate particles by coating the first intermediate particles with a second mixture including a coloring material; and   (d) heating the second intermediate particles to decompose the void-forming material and form pores in the first layer to produce the roofing granules.   
     
     
         31 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the first mixture further includes a binder, the binder comprising an aluminosilicate material and an alkali metal silicate. 
     
     
         32 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the second mixture further includes a binder, the binder comprising an aluminosilicate material and an alkali metal silicate. 
     
     
         33 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the at least one algaecidal material is selected from the group consisting of copper compounds and zinc compounds. 
     
     
         34 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the at least one algaecidal material comprises cuprous oxide. 
     
     
         35 . The algae-resistant roofing product of  claim 34 , wherein in the process for producing the algae-resistant roofing granules, the cuprous oxide comprises at least 2 percent of the algae resistant granules. 
     
     
         36 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the at least one algaecidal material further comprises zinc oxide. 
     
     
         37 . The algae-resistant roofing product of  claim 36 , wherein in the process for producing the algae-resistant roofing granules, the zinc oxide comprise at least 0.1 percent by weight of the algae-resistant granules. 
     
     
         38 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the void-forming material comprises a substance selected from the group comprising ground walnut shells, sugar, and carbon black. 
     
     
         39 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the void-forming material comprises at least 0.1 percent by weight of the algae-resistant granules. 
     
     
         40 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the coloring material is selected from the group comprising transition metal oxides. 
     
     
         41 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the second intermediate particles are heated to a temperature of at least 500 degrees C. 
     
     
         42 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the granules have a pore size in the range of about 0.1 to 20 micrometers. 
     
     
         43 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the first intermediate layer has a thickness of about 30 micrometers. 
     
     
         44 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the second intermediate layer has a thickness of about 5 micrometers. 
     
     
         45 . The algae-resistant roofing product of  claim 30 , wherein in the process for producing the algae-resistant roofing granules, the second mixture further includes at least one algaecidal material.