| 摘要 |
<p>A high opacity, defined kaolin clay product having a relatively narrow particle size distribution, low colloidal particle content and an average particle surface aera of less than about 30 square meters per gram is prepared by defining an aqueous kaolin clay slurry via controlled centrifugation to remove a substantial portion of the colloidal particles therein. Prior to being subjected to centrifugation, the aqueous kaolin clay slurry is prepared so as to improve the defining process achieved via centrifugation by first subjecting the aqueous kaolin clay suspension (21) to scrub grinding (21) so as to break up agglomerates into individual kaolin clay particles without substantial delamination of the kaolin clay particles. Thence, the mechanically dispersed kaolin clay suspension (23) is dispersed to its optimum level by the addition of a chemical dispersant (5), most advantageously sodium hexamethaphosphate, and dilution water (7) is admixed into the aqueous kaolin clay suspension to reduce the solids content thereof to a level less than at least about 18 % solids by weight, and preferably to about 5 % to about 15 % by weight, prior to centrifugation (30).</p> |
