Patent ID: 7261869

Claim:
A process for producing a particulate calcium carbonate which is suitable as a paper filler by taking advantage of a causticization step of a sulfate process or soda process, comprising: producing a milk or slurry of lime by a first slaking reaction step of (a) adding a white liquor to a quick lime containing 0.1 to 10% by weight of calcium carbonate on the basis of the weight of said quick lime to produce a quick lime mixture until a concentration of said quick lime reaches 0.5 to 60% by weight on the basis of the weight of said quick lime mixture before slaking; and slaking said quick lime of step (a) with stirring or kneading to prepare said milk or slurry of lime, wherein the quick lime to be added to the first step (a) is obtained from a source that is not from a causticization step of a sulfate process or soda process; a second causticizing reaction step of sequentially adding green liquor to said milk or slurry of lime, where said green liquor is obtained from a causticization step of a sulfate process or soda process and is added in an amount necessary to produce a white liquor and said particulate calcium carbonate having a spindle shape or rice shape, wherein said green liquor is added at a loading rate of 0.02 to 0.5 cc (green liquor)/min/g (quick lime) and at a reaction temperature of 20 to 105° C., and then separating said particulate calcium carbonate from said white liquor.