Silica-calcium carbonate composition particles having the characteristics
of both synthetic silica and calcium carbonate are described along with
paper having the particles internally filled therein and a method for
making the particles.In the carbonation reaction, which typically
involves a step of forming calcium carbonate, while agitating a calcium
hydroxide slurry, a mixed gas of carbon dioxide and air is introduced
thereinto and synthetic silica, such as colloidal silica or the like, is
added before the carbonation rate arrives at 95% but after commencement
of the carbonation reaction, followed by further introduction of the
mixed gas to continue the carbonation reaction and completion of the
carbonation reaction at the time when the pH of the slurry reaches 7,
thereby providing the composite particles.