| 摘要 |
<p>A method for producing a spherical calcium carbonate wherein a carbon dioxide gas or a carbon dioxide containing gas is blown into an aqueous suspension containing calcium hydroxide to react them, which comprises adding, after the start of the reaction, an aqueous solution or suspension of a water-soluble phosphoric acid or a water-soluble salt thereof to the reaction mixture at the time when the conversion of carbonation has reached 2 to 10 %, and continuing the reaction with a low gas blowing rate of 1.0 NL or less (step (a)), and subsequently adding an aqueous solution or suspension of an aqueous suspension containing calcium hydroxide and a water-soluble phosphoric acid or a water-soluble salt thereof to the resultant reaction mixture and introducing a carbon dioxide gas or a carbon dioxide containing gas for reaction. The method allows the production of a spherical calcium carbonate having an average particle diameter of 10 mum or more. The above method which further comprises carrying out the operation from the start of the reaction to the end of the step (a) under a high speed rotation condition defined in the specification allows the production of a calcite type spherical calcium carbonate which has an average particle diameter of 10 mum or more and a shape near a perfect sphere, and exhibits high whiteness and a reduced friction coefficient.</p> |
