CALCIUM CARBONATE IN A PLATELET-LIKE PARTICULATE FORM AND A METHOD FOR THE PREPARATION THEREOF

摘要

A method for the preparation of a calcium carbonate powder of which the particles have a platelet-like particulate configuration and which is useful as a pigment or filler in various products with superiority to kaolin clays and mica powders. The method is a two-step carbonation method of a milk of lime of which the first step is performed by blowing carbon dioxide into the milk of lime until 10 to 70% of the calcium hydroxide is carbonated and the second step is performed by admixing the thus partially carbonated milk of lime with an aqueous carbonating solution containing an alkali metal carbonate or ammonium carbonate and an alkali metal hydroxide or ammonium hydroxide in specified concentrations to complete the carbonation of the calcium hydroxide. The first step carbonation is preferably preceded by a pretreatment of the milk of lime in which the milk of lime is subjected to shearing disintegration of the calcium hydroxide particles to cause a substantial increase of the viscosity up to a specified extent.