Abstract: The light calcium carbonate in the form of microparticle aggregate of the present invention has a BET specific surface area not smaller than 10 m2/g and not larger than 25 m2/g, a pore volume of 0.05 cm3/g or larger for pores having a pore diameter of 0 to 1000 ? as determined by the nitrogen adsorption method, and a pore volume ratio of 25% or more for pores having a pore diameter of 250 ? or smaller based on the total pore volume as determined by the nitrogen adsorption method, and shows an oil absorption of 100 cc/100 g or more as determined by using liquid paraffin. By using this light calcium carbonate as a filler of printing paper, superior ink absorbing property and opacity (especially opacity after printing) can be imparted to the printing paper.

Abstract: Carbon dioxide containing gas is blown into a calcium hydroxide slurry having a calcium hydroxide concentration of 100 to 400 g/L obtained by wet slaking calcined lime with 4 N hydrochloric acid activity (value at 3 minutes) of 150 to 400 mL to allow them to react until the carbonation rate becomes 50 to 85%, then 1 to 20% by volume of the calcium hydroxide slurry is added, and carbon dioxide containing gas is further blown in to terminate the reaction. The calcium carbonate obtained by this method is precipitated calcium carbonate aggregates having a secondary particle diameter of 1 to 10 ?m and consisting of primary particles having a long diameter of 0.5 to 3.0 ?m, a short diameter of 0.1 to 1.0 ?m and an aspect ratio of 3 or more, has superior characteristics due to a BET specific surface area in the range of 8 to 20 m2/g and a pore volume in the range of 1.5 to 3.5 cm3/g, can be uniformly dispersed in pulp fiber, and thereby can be used to manufacture high bulk paper.

Abstract: The light calcium carbonate in the form of microparticle aggregate of the present invention has a BET specific surface area not smaller than 10 m2/g and not larger than 25 m2/g, a pore volume of 0.05 cm3/g or larger for pores having a pore diameter of 0 to 1000 ? as determined by the nitrogen adsorption method, and a pore volume ratio of 25% or more for pores having a pore diameter of 250 ? or smaller based on the total pore volume as determined by the nitrogen adsorption method, and shows an oil absorption of 100 cc/100 g or more as determined by using liquid paraffin. By using this light calcium carbonate as a filler of printing paper, superior ink absorbing property and opacity (especially opacity after printing) can be imparted to the printing paper.

Abstract: A coating solution comprising: (A) an aragonite-type light calcium carbonate microparticle having an average major axis diameter of 1.0 to 2.8 ?m and an average minor axis diameter of 0.15 to 0.3 ?m, which is produced by diluting a calcium hydroxide slurry that has been treated by high-speed shearing until the slurry has a viscosity of 1000 cP or more at a concentration of 400 g/l to a concentration more than 50 g/l and then blowing carbon dioxide into the diluted slurry at a reaction starting temperature of 20 to 60° C. and at a rate of 1 to 3 l/min per kg of calcium hydroxide; and (B) a pigment comprising a wet heavy calcium carbonate cake. The coating solution enables to provide a coated paper having an excellent degree of brilliance and an excellent degree of whiteness, despite containing no kaolin.

Abstract: Carbon dioxide containing gas is blown into a calcium hydroxide slurry having a calcium hydroxide concentration of 100 to 400 g/L obtained by wet slaking calcined lime with 4 N hydrochloric acid activity (value at 3 minutes) of 150 to 400 mL to allow them to react until the carbonation rate becomes 50 to 85%, then 1 to 20% by volume of the calcium hydroxide slurry is added, and carbon dioxide containing gas is further blown in to terminate the reaction. The calcium carbonate obtained by this method is precipitated calcium carbonate aggregates having a secondary particle diameter of 1 to 10 ?m and consisting of primary particles having a long diameter of 0.5 to 3.0 ?m, a short diameter of 0.1 to 1.0 ?m and an aspect ratio of less than 3, has superior characteristics due to a BET specific surface area in the range of 8 to 20 m2/g and a pore volume in the range of 1.5 to 3.5 cm3/g, can be uniformly dispersed in pulp fiber, and thereby can be used to manufacture high bulk paper.