21 ноября, 2015 
Pokraskin Calcium carbonate (CaCO)
Calcium carbonate is one of the most widely used fillers in the coating industry. Natural calcium carbonate is obtained by grinding of chalk (whiting), limestone, calcite and marble. Except for chalk, the other forms are crystalline. Synthetic calcium carbonate, often referred as precipitated calcium carbonate, is often produced by passing carbon dioxide through purified slaked lime, and sometimes produced as the byproduct of other industrial processes. Due to the better control over the precipitation process, as compared to mechanical grinding of natural minerals, synthetic grades are available in much finer and more uniform particle sizes with higher purity.
The widespread use of calcium carbonate is attributed to its allround properties — high brightness, low oil absorption, good flow, economic availability, good weather resistance and versatility of use with a variety of pigments. Calcium carbonate is an important extender used in water-based architectural paints, primers, anticorrosive paints, undercoats, putties and fillers. Very fine grade precipitated calcium carbonate is used to control flooding and floating of colored pigments in many formulations.
During natural deposition of carbonates, when magnesium salts are present, a mixture of magnesium and calcium carbonates are precipitated, which is known as dolomite. Dolomite contains about 40 to 45 % MgCO3 and 55 to 60 % CaCO3. Its properties are close to those of natural calcium carbonate, except that it is slightly denser and less bright and less sensitive to acid than calcium carbonate.
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