Patent ID: 6194069
Filing Date: 2001-02-27
Classification: B01J,G02F,Y10T

Abstract:
A process for the production of insulator-coated black particles, which comprises the steps of(1-a) dispersing particles of silica or a metal oxide in an alcohol-based solvent consisting mainly of an intermediate alcohol to obtain a dispersion of the above particles;(1-b) adding an alkaline aqueous solution to the dispersion obtained in step (1-a) to activate a surface of each of the metal oxide particles;(1-c) forming a titanium oxide coating of TiO.sub.2 on the surface of each of the particles whose surfaces have been activated in the above step, to obtain titanium oxide-coated particles;(1 -d) calcining the titanium oxide-coated particles obtained in the above step in a reducing and/or nitriding atmosphere and thereby blackening the above titanium oxide coatings to obtain black particles; and(1-e) forming an electrical insulator coating on a surface of each of the black particles obtained in the above step, to obtain insulator-coated black particles;wherein step (1-c) is carried out by adding a titanium alkoxide or its partial hydrolyzate to the dispersion of the particles whose surfaces have been activated in the above step (1-b), hydrolyzing and dehydratively condensing the titanium alkoxide or the partial hydrolyzate to form a titanium oxide coating on each of the above particles, separating the resultant titanium oxide-coated particles from the above dispersion, dispersing them in neutral water, heat-treating them, then, separating the titanium oxide-coated particles from the above neutral water and treating them under dry heat.