GB416730A - Improvements in or relating to the manufacture of abrasive material - Google Patents

Abstract

Abrasive granules are treated, so that a binder such as glue will adhere to them more tenaciously, by applying a rough adherent coating to at least part of the surface of the granules. The granules may be mixed with a slurry of vitrifiable material such as clays, bentonite, talc, cryolite, fluorspar, or feldspar, or mixtures thereof, the excess slurry is drained off, forced drainage, e.g. by vacuum, being used if desired, and the granules are then heated to burn the coating produced. Fluxing materials such as borax, alkaline silicates, halides or hydroxides may be added to lower the fusion point of the coating material or to attach an infusible material to the granules. Temporary binders such as dextrin, powdered gums or sulphite cellulose liquor residues may be added to the coating material to increase its adhesiveness before the heat treatment. In one method, abrasive granules such as fused alumina or silicon carbide are stirred with a slurry composed of 5 per cent slip clay such as albany clay, 2 per cent borax, and 93 per cent water, and after the granules have been wetted the excess slurry is drained off and the granules are dried at about 150 DEG C. The granules are then heated to about 900 DEG C. to fuse the clay on to their surfaces. The granules are next cooled to about 250 DEG C., treated to remove loose foreign matter, e.g. by agitation in water, and dried, e.g. at 300 DEG C. or a lower temperature where high capillarity is not required. The product has increased resistance to flow which enables it to be more easily picked up by the glue when it is being attached to polishing wheels. Specification 193,081, [Class 91], is referred to.