Kaolin clay pigments, their preparation and use

摘要

A paper coating pigment manufactured from kaolin crude containing minor amounts of minerals is used in lightweight coated and ultra-lightweight coated applications. The pigments comprise a phyllosilicate assemblage of minerals that yield a final pigment MgO content ranging between 0.04 to 0.3 weight percent and a K2O content ranging between 0.12 and 0.8 weight percent based on the dry weight of the kaolin crude. The mica in the pigment product is 1.0% to 6.7% by weight, and smectite is 1.2% to 9.1% by weight of the kaolin. The presence of these weight percentages can be identified by a shape factor of 15 or greater. The viscous clay content of the feed to produce the pigment product is between 70 and 100 weight percent based on the dry weight of the kaolin clay. The pigment has a shape factor ranging between 35 and 60 or greater, and greater than 80% by weight of the particle are less than 2 microns, and greater than 12% are less than 0.25 microns.