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.

What is claimed is: 
     
         1 . A method of making an infrared-reflective coating comprising:
 dispersing infrared-reflective clusters comprising titanium dioxide particles and a precipitate into a coating formulation to form an infrared-reflective coating, wherein the titanium dioxide primary particles are cemented together with the precipitate to form the infrared-reflective clusters, and 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 method of  claim 1 , wherein the infrared-reflective clusters are dispersed into the coating formulation using a high speed disperser. 
     
     
         3 . The method of  claim 1 , wherein the infrared-reflective clusters are dispersed into the coating formulation using media milling. 
     
     
         4 . The method of  claim 1 , wherein the infrared-reflective clusters are dispersed into the coating formulation using mixing or agitation. 
     
     
         5 . The method of  claim 1 , wherein the titanium dioxide particles are produced by the chloride process. 
     
     
         6 . The method of  claim 1 , wherein the titanium dioxide particles are produced by the sulfate process. 
     
     
         7 . The method of  claim 1 , wherein the precipitate cementing the titanium dioxide primary particles together comprises at least one of precipitated silica and precipitated alumina. 
     
     
         8 . The method of  claim 7 , 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. 
     
     
         9 . The method of  claim 7 , 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. 
     
     
         10 . The method 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. 
     
     
         11 . The method of  claim 1 , wherein the titanium dioxide primary particles have a rutile crystal structure. 
     
     
         12 . The method of  claim 1 , wherein the titanium dioxide primary particles have an anatase crystal structure. 
     
     
         13 . The method of  claim 1 , further comprising adding at least one colorant to the coating formulation.