Infrared-reflective coatings

Abstract

A composition includes polymer and dispersed infrared-reflective clusters of titanium dioxide primary particles. The titanium dioxide primary particles are cemented together with precipitated silica and/or alumina to form clusters. The titanium dioxide primary particles have an average particle diameter in the range of from about 0.15 to about 0.35 micron, while the clusters of titanium dioxide primary particles have an average cluster diameter in the range of from about 0.38 to about 5 microns and a geometric standard deviation (GSD) in the range of from about 1.55 to about 2.5.

1 . A composition comprising infrared-reflective clusters comprising titanium dioxide primary particles and a precipitate, wherein the titanium dioxide primary particles are cemented together with the precipitate to form the infrared-reflective clusters, wherein the titanium dioxide primary particles have an average particle diameter in a range of from about 0.15 to about 0.35 microns, and the infrared-reflective clusters have a geometric mass mean cluster diameter in a range of from about 0.38 to about 5 microns and a geometric standard deviation (GSD) in a range of from about 1.55 to about 2.5. 
     
     
         2 . The composition of  claim 1 , wherein the infrared-reflective clusters have a geometric mass mean cluster diameter in a range of from about 0.38 to about 1 micron. 
     
     
         3 . The composition of  claim 1 , wherein the infrared-reflective clusters have a geometric standard deviation (GSD) in a range of from about 1.55 to about 2.00. 
     
     
         4 . The composition of  claim 1 , wherein the precipitate cementing the titanium dioxide primary particles together comprises at least one of precipitated silica and precipitated alumina. 
     
     
         5 . The composition of  claim 4 , wherein the precipitate comprises precipitated silica present in the infrared-reflective clusters at an amount in a range of from about 2 wt. % to about 20 wt. % based on the weight of titanium dioxide in the clusters. 
     
     
         6 . The composition of  claim 4 , wherein the precipitate comprises precipitated alumina present in the infrared-reflective clusters at an amount in a range of from about 2 wt. % to about 10 wt. % based on the weight of titanium dioxide in the clusters. 
     
     
         7 . The composition of  claim 1 , wherein the precipitate cementing the titanium dioxide primary particles together consists essentially of silica, alumina or a combination of silica and alumina. 
     
     
         8 . The composition of  claim 1 , wherein the titanium dioxide primary particles have a rutile crystal structure. 
     
     
         9 . The composition of  claim 1 , wherein the titanium dioxide primary particles have an anatase crystal structure. 
     
     
         10 . The composition of  claim 1 , further comprising unagglomerated titanium dioxide primary particles having an average particle diameter in the range of from about 0.15 to about 0.35 micron. 
     
     
         11 . The composition of  claim 1 , further comprising at least one colorant. 
     
     
         12 . The composition of  claim 1 , further comprising base rock or mineral granules. 
     
     
         13 . The composition of  claim 12 , wherein the infrared-reflective clusters at least partially cover the base rock or mineral granules. 
     
     
         14 . The composition of  claim 13 , wherein the infrared-reflective clusters at least partially covering the base rock or mineral granules form a water resistant coating material at least partially covering the base rock or mineral granules. 
     
     
         15 . A method of making infrared-reflective clusters of titanium dioxide primary particles comprising the steps of:
 treating an aqueous slurry of titanium dioxide particles to deposit a precipitate thereon;   drying the treated titanium dioxide particles to form infrared-reflective clusters comprising the titanium dioxide primary particles and the precipitate, wherein the titanium dioxide primary particles are cemented together with the precipitate to form the infrared-reflective clusters, wherein the infrared-reflective clusters have a geometric mass mean cluster diameter in a range of from about 0.38 to about 5 microns, and a geometric standard deviation (GSD) in a range of from about 1.55 to about 2.5.   
     
     
         16 . The method of  claim 15 , wherein the titanium dioxide particles are produced by the chloride process. 
     
     
         17 . The method of  claim 15 , wherein the titanium dioxide particles are produced by the sulfate process. 
     
     
         18 . The method of  claim 15 , further comprising packaging the infrared-reflective clusters without micronization such that the infrared-reflective clusters retain a geometric mass mean cluster diameter in a range of from about 0.38 to about 5 microns. 
     
     
         19 . The method of  claim 15 , further comprising micronizing the infrared-reflective clusters using a steam or air pressure low enough to result in infrared-reflective clusters having an average cluster diameter in a range of from about 0.38 to about 1 microns. 
     
     
         20 . The method of  claim 15 , wherein the precipitate cementing the titanium dioxide primary particles together comprises at least one of precipitated silica and precipitated alumina. 
     
     
         21 . The method of  claim 20 , wherein the precipitate comprises precipitated silica present in the infrared-reflective clusters at an amount in a range of from about 2 wt. % to about 20 wt. % based on the weight of titanium dioxide in the clusters. 
     
     
         22 . The method of  claim 20 , wherein the precipitate comprises precipitated alumina present in the infrared-reflective clusters at an amount in a range of from about 2 wt. % to about 10 wt. % based on the weight of titanium dioxide in the clusters. 
     
     
         23 . The method of  claim 15 , wherein the precipitate cementing the titanium dioxide primary particles together consists essentially of silica, alumina or a combination of silica and alumina. 
     
     
         24 . The method of  claim 15 , wherein the titanium dioxide primary particles have a rutile crystal structure. 
     
     
         25 . The method of  claim 15 , wherein the titanium dioxide primary particles have an anatase crystal structure. 
     
     
         26 . The method of  claim 15 , further comprising adding at least one colorant to the aqueous slurry of titanium dioxide particles. 
     
     
         27 .- 67 . (canceled)