Patent ID: 8557037

Claim:
A method of processing kaolin, comprising sequentially: subjecting a kaolin crude comprising at least 75 wt. % of gray kaolin to flotation to provide a kaolin having reduced titania content; centrifuging the kaolin having reduced titania content at high speeds to provide a coarse stream and a 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 hydrous kaolin pigment; said refining comprising flocculation, bleaching, filtering, spray drying, and pulverizing after spray drying, said ultrafine hydrous kaolin pigment comprising particles wherein at least about 97% by weight of the particles have a size of 2 microns or less, at least about 96% by weight of the particles have a size of 1 micron or less, at least about 89% by weight of the particles have a size of 0.5 microns or less, at least about 67% of the particles have a size of 0.3 microns or less, a surface area of the particles is more than 23 m 2 /g, and brightness of the particles is at least about 91; a moisture level less than about 1% by weight, from 0.29 to about 0.75% by weight of titania, and from 0.89 to about 1.5% by weight of iron oxide, said ultrafine hydrous kaolin pigment comprising no charged inorganic or organic molecules from selective flocculation, and wherein the method does not comprise selective flocculation.