Patent ID: 7097819

Claim:
A process for producing calcium carbonate in the form of aragonite crystals which is useful as a filler for papermaking via the causticization step of the sulfate or soda pulping process, which process comprises (1) adding an aqueous alkaline solution having a pH higher than 13.5, a hydroxide ion level of 3 mol/l or less and containing 0.1 mol/mol (carbonate ion/quick lime) or less of carbonate ion to quick lime and/or slaked lime, until the concentration of the quick lime reaches 1–60% by weight with stirring to prepare milk of lime, and then (2) adding green liquor to said milk of lime at a loading rate of 0.002–0.04 g (sodium carbonate)/min/g (quick lime) to perform a causticization reaction at a temperature of 30–105° C.