PROCESS FOR PREPARING CALCIUM CARBONATE

摘要

A process for preparing calcium carbonate wherein the causticizing step is utilized to prepare inexpensive spindle-shaped or acicular calcium carbonate which can impart as a papermaking filler the properties useful for paper, such as bulk, whiteness, opacity, prevention of wire wear, and retention. In the slaking as the first stage, the quick lime used has a calcium carbonate content of not more than 10 % by weight and a liquid having a pH of 5.5-13.5 is used, while the slaking is carried out in a concentration of 20 to 60 % to prepare a milk of lime. A causticizing reaction in the second stage is carried out under conditions of a green liquor addition rate of 0.02 to 0.5 cc (green liquor)/min/g (quick lime) and a reaction temperature of 20 to 150 ~C to prepare spindle-shaped or acicular calcium carbonate.