Shiraishi Kogyo Kaisha, Ltd.

Kao Soap Company, Ltd.

Hisashi Hasegawa

Setsuji Edagawa

Hiroji Shibazaki

Satoshi Kondo

Noboru Moriyama

Yoshisada Kayano

Takashi Takeuchi

Kazuo Ohnawa

Yukihiro Fukuyama

The invention provides a surface-treated calcium carbonate that when incorporated into a paste resin, can impart low viscosity and high thixotropy and offers excellent storage stability, and paste resin compositions containing the same. The surface-treated calcium carbonate is a calcium carbonate surface-treated with a surface treatment agent containing a sodium salt or potassium salt of a fatty acid, wherein the total content of a sodium salt and a potassium salt of lauric acid, a sodium salt and a potassium salt of palmitic acid and a sodium salt and a potassium salt of stearic acid in the surface treatment agent is 80% by weight or more, the content of the sodium salt and potassium salt of lauric acid is within the range of 30% to 60% by weight, the content of a sodium salt and a potassium salt of an unsaturated fatty acid in the surface treatment agent is 5% by weight or less, and the BET specific surface area is 10 m/g or more.

Surface-treated calcium carbonate and paste resin composition containing same

The invention provides calcium carbonate particles comprising a core and projections formed thereon, and process for preparing same. The calcium carbonates of this invention are useful as fillers and pigments for rubbers, plastics, papers, etc. because of their peculiar configuration and unique properties.

Calcium carbonate particles and processes for preparing same

The filled paper is filled with at least one of (i) a calcium carbonate in the form of particles comprising a core about 0.5 to about 6.5 .mu.m in average diameter and about 100 to about 4000 projections formed on the surface of the core and having a length (L) of about 0.25 to about 2.00 .mu.m, a diameter (D) of about 0.08 to about 0.20 .mu.m and an aspect ratio (L/D) of about 3 to about 10, the calcium carbonate having a void volume of about 1.0 to about 1.8 ml/g and an oil absorption of about 45 to about 60 ml/100 g, and (ii) a calcium carbonate in the form of particles comprising a core about 0.2 to about 2.0 .mu.m in average diameter and about 100 to about 4000 projections formed on the surface of the core and having a length (L) of about 0.15 to about 4.00 .mu.m, a diameter (D) of about 0.05 to about 0.20 .mu.m and an aspect ratio (L/D) of about 3 to about 20, the calcium carbonate having a void volume of about 1.8 to about 3.3 ml/g and an oil absorption of about 50 to about 100 ml/100 g. The paper has increased stiffness and enhanced opacity with reduced weight.

Filled paper

Calcium carbonate is dispersed by a dispersant comprising a salt of an acrylic acid/maleic acid copolymer.

Dispersant for calcium carbonate

Surface-treated calcium carbonate powders of this invention are easy to handle and highly dispersible in water, give slurries of high concentration and are useful as pigments and various other applications.

Calcium carbonate powders

Precipitated calcium carbonate of uniform particle size is produced by contacting a suspension of calcium hydroxide with a carbon dioxide-containing gas in three steps. The particle size of precipitated calcium carbonate can be optionally selected by suitably adjusting reaction conditions.

Process for preparing precipitated calcium carbonate

Cubic calcium carbonate crystals of uniform size are prepared by contacting with CO.sub.2 a starting aqueous suspension containing Ca(OH).sub.2 and cubic CaCO.sub.3 crystals less than 0.1.mu.m in size, adding Ca(OH).sub.2 to the suspension resulting from the first step and contacting the resultant mixture with CO.sub.2.

Growing community of inventors

Nishinomiya, Japan

Hisashi Hasegawa