GB679552A - Improvements relating to methods and apparatus for grinding, crushing and disintegrating - Google Patents

Abstract

Pigments or fillers are milled in ball mills with sand, i.e. a collection of non-metallic particles the average granular size of which does not exceed 1/10th of an inch in diameter (see Group II) so as to reduce their particle size and thus improve the properties of hiding power and tinting strength. In one example, the raw pigment product obtained by calcining precipitated titanium oxide pulp is first subjected to a preliminary rough reduction, e.g. in a rotary hammer mill, and then subjected to dry or wet milling in the ball mill. In another example, previously-ground red iron oxide is subjected to wet milling in the ball mill. In the case of wet milling, the pigment is milled in the form of a dispersion in water, the milling operation being carried out in the presence of a wetting agent, e.g. sodium hexameta phosphate.ALSO:In ball mills for milling pigments or fillers so as to reduce their particle size and thus improve the properties of hiding power and tinting strength, the grinding medium comprises a sand, i.e. a collection of non-metallic particles the average granule size of which does not exceed 1 10 of an inch in diameter. The granule size is preferably within the range 50m to 150m , and, preferably, zircon sand is used. In one example, the raw pigment product obtained by calcining precipitated titanium oxide pulp is first subjected to a preliminary rough reduction, e.g. in a rotary hammer mill, and then subjected to dry or wet milling in the ball mill. In another example, previously-ground red iron oxide is subjected to wet milling in the ball mill. In the case of wet milling, the pigment is milled in the form of a dispersion in water, the milling operation being carried out in the presence of a wetting agent, e.g. sodium hexameta phosphate.