Patent ID: 6022517
Filing Date: 2000-02-08
Classification: C01F,C01P

Abstract:
A process for the preparation of clustered calcium carbonate crystals having acicular calcite and acicular aragonite in the ratio of 75/25 to 25/75, wherein the clustered calcium carbonate crystals consist of rod-shaped or needle-shaped acicular crystals having an average equivalent spherical diameter of from about 2.0 microns to about 8.0 microns, a specific surface area of from about 5.0 m .sup.2 /g to about 10 m .sup.2 /g and rods or needles having a length of from about 1.0 microns to about 4 microns and a width of from about 0.1 microns to about 0.5 microns comprising effectively reacting calcium hydroxide or calcium oxide with carbon dioxide in the presence of a water soluble aluminum compound by controlling the specific conductivity in a range of greater than 4.0 milliSiemens per centimeter to about 7.0 milliSiemens per centimeter and having a reaction temperature of from about 25 degrees Centigrade to about 60 degrees Centigrade to form said acicular calcite and acicular aragonite crystals.