Ultrafine Hydrous Kaolin Pigments, Methods of Making the Pigments, and Methods of Using the Pigments in Gloss Paint Formulations

Abstract

Disclosed are methods of processing kaolin to produce ultrafine hydrous kaolin. The methods involve processing gray crude kaolin by subjecting the kaolin crude to flotation and then centrifuging the kaolin to provide a fine stream that is subject to refinement. Also disclosed are systems for the automated processing of gray crude kaolin to produce the ultrafine hydrous kaolin and paint compositions that contain the ultrafine hydrous kaolin.

1 . A method of processing kaolin, comprising sequentially:
 subjecting a kaolin crude comprising a super major amount of gray kaolin to flotation to provide a kaolin having reduced titania content;   centrifuging the kaolin kaolin having reduced titania content at high speeds to provide a coarse stream and fine stream, the coarse stream comprising kaolin wherein at least about 70% by weight has a size of 2 microns or less, the fine stream comprising kaolin wherein at least about 80% by weight has a size of 1 micron or less; and   refining the fine stream into an ultrafine kaolin pigment.   
     
     
         2 . The method of  claim 1 , wherein centrifuging at high speeds involves using “g” forces from about 1,000 to about 10,000. 
     
     
         3 . The method of  claim 1 , wherein the kaolin crude comprises at least about 75% by weight of gray kaolin. 
     
     
         4 . The method of  claim 1 , wherein flotation reduces the titania content of the kaolin to less than about 1% by weight. 
     
     
         5 . The method of  claim 1 , wherein flotation comprises one of froth flotation, ultraflotation, and TREP flotation. 
     
     
         6 . The method of  claim 1 , further comprising degritting the kaolin crude before subjecting the kaolin crude to flotation. 
     
     
         7 . The method of  claim 1  further comprising ozonating the kaolin having a reduced titania content before centrifuging the kaolin, ozonating comprising contacting the kaolin having a reduced titania content with about 0.1 to about 20 pounds of ozone per ton of kaolin. 
     
     
         8 . The method of  claim 1 , wherein refining the fine stream comprises at least two of flocculation, bleaching, filtering, and drying. 
     
     
         9 . The method of  claim 1 , wherein refining the fine stream comprises at least three of flocculation, bleaching, filtering, spray drying, and pulverization. 
     
     
         10 . The method of  claim 1 , with the proviso that the method does not comprise selective flocculation of the kaolin crude. 
     
     
         11 . The method of  claim 1  further comprising refining the coarse stream into a coarse engineered kaolin pigment. 
     
     
         12 . The method of  claim 1 , further comprising testing and generating data of at least one parameter of at least one of the kaolin crude, the kaolin having reduced titania content, the fine stream, or ultrafine kaolin pigment or at least one parameter of subjecting the kaolin crude to flotation and centrifuging the kaolin at high speeds; and controlling operation of at least one of subjecting the kaolin crude to flotation and centrifuging the kaolin at high speeds based on data generated by the tester. 
     
     
         13 - 20 . (canceled)