Spherically shaped precipitated calcium carbonate, its preparation and use

Abstract From the Canadian patent

Abstract A precipitated calcite of substantially spherical morphology having an average spherical diameter of from 2 to 10 microns and a specific surface area of from 1 to 15 square meters per gram is prepared by introducing carbon dioxide gas into an aqueous slurry of calcium hydroxide containing dissolved polyphosphate in the amount of from 0.1 to 1.0 percent, calculated as grams of phosphorus per 100 grams of the calcite equivalent of the calcium hydroxide, the starting temperature of the carbonation being 15 to 50°C. The spherical calcite is particularly suitable for use in dull finish coated paper.