Kaolin pigments, their preparation and use

摘要

A pigment product suitable for use in a coating composition to provide a gloss coating on paper, the pigment product comprising a processed particulate kaolin produced from a naturally platy kaolin clay having a particle size distribution such that about 50% to 60% by weight of the particles have an esd less than 2 mum and less than 25% by weight of the particles have an esd less than 0.25 mum and a shape factor of at least 15. In processing, the crude kaolin is ground to a shape factor greater than 50 to produce even greater "platy" clay. The pigment product has a particle size distribution such that at least 80% by weight of the particles have an esd less than 2 mum and greater than 12% and less than 35% by weight of the particles have an esd less than 0.25 mum and whose surface area is greater than 12 m2/g when measured by the BET method.