PREPARATION OF CALCITE-TYPE CALCIUM CARBONATE CRYSTAL

摘要

PURPOSE:To prepare calcium carbonate crystal capable of imparting excellent white gloss, by blowing CO2 in an aqueous slurry containing calcite-type cubic calcium carbonate crystals at a specific concentration thereby maintaining the pH of the slurry at a specific level, and adding milk of slaked lime having a specific concentration to the slurry. CONSTITUTION:CO2 is blown in an aqueous slurry containing calcite-type cubic calcium carbonate crystals having particle size of about 0.03-0.05mu at a concentration of 50-200g/l to maintain the pH of the slurry at 6-12. The rate of blowing of CO2 is about 10-30l/min per 1kg of the calcite-type cubic calcium carbonate crystal. Then, slaked lime milk of a concentration of 50-250g/l is added to the slurry. The amount of the slaked lime is about 0.5-4mol per 1mol of the calcite-type cubic calcium carbonate crystal. The temperature at the initiation of the reaction of slaked lime with CO2 is pref. about 5-70 deg.C.