MINERAL FILLERS

摘要

A filler for paper or the like comprises particles of a white clay having (a) a particle size distribution such that it contains not more than 18% by weight of particles smaller than 2 microns equivalent spherical diameter, (b) an abrasion of less than 120 Valley, and (c) a brightness a white clay mineral to a two-stage particle size classification process, in order to obtain a product smaller than 2 microns equivalent spherical diameter, and thereafter subjecting it to a beneficiating process in order to reduce the number of particles having an abrasive character to a level such that the product has an abrasion of less than 120 Valley and removing or bleaching sufficient iron-containing impurities to ensure that the white clay mineral has a brightness of at least 76.