Calcium carbonate reacts with all strong acids to generate water and corresponding calcium salts (such as calcium chloride CaCl2), while releasing carbon dioxide; at normal temperature (25°C), the concentration product of calcium carbonate in water is 8.7 × 10^ 29. The solubility is 0.0014, the pH value of calcium carbonate aqueous solution is 9.5~10.2, and the pH value of air-saturated calcium carbonate aqueous solution is 8.0~8.6. Calcium carbonate is non-toxic, odorless, non-irritating, usually white, and the relative density is 2.7~2.9.
The shape of light calcium carbonate Light calcium carbonate can be divided into spindle-shaped, cubic, needle-shaped, chain-shaped, spherical, sheet-shaped and tetragonal column-shaped calcium carbonate according to the shape of calcium carbonate grains. Calcium carbonate of these different crystalline forms can be prepared by controlling the reaction conditions. According to its original average particle size (d), light calcium carbonate is divided into: granular calcium carbonate (5μm), micropowder calcium carbonate (1~5μm), fine calcium carbonate (0.1~1μm), ultrafine calcium carbonate (0.02~0.1μm ), ultrafine calcium carbonate (0.02μm).
It is to burn limestone and other raw materials to produce lime (mainly composed of calcium oxide) and carbon dioxide, then add water to digest the lime to form milk of lime (mainly composed of calcium hydroxide), and then pass in carbon dioxide to carbonize the milk of lime to form calcium carbonate precipitation. It can be obtained by dehydration, drying and pulverization, or by metathesis reaction with sodium carbonate and calcium chloride to generate calcium carbonate precipitate, and then it can be obtained by dehydration, drying and pulverization.
The chemical formula of calcium carbonate is CaCO3, the sedimentation volume of light calcium carbonate is above 2.5ml/g, and the specific surface area is about 5m2/g. Light calcium carbonate particles are fine, the surface is rough, and the specific surface area is large, so the oil absorption value is relatively high, about 60~90ml/100g.
effect:
Light calcium carbonate has a wide range of functions and uses, and can be used in the following industries:
1. Rubber industry
Calcium carbonate is one of the earliest and largest fillers used in the rubber industry. A large amount of calcium carbonate is filled in rubber, which can increase the volume of the product, thereby saving expensive natural rubber and reducing costs. Filling calcium carbonate into rubber can obtain Compared with pure rubber vulcanizate, it has higher tensile strength, abrasion resistance, tear strength, and has a significant reinforcing effect in natural rubber and synthetic rubber, and can adjust the consistency at the same time.
2. Plastic industry
Calcium carbonate can play a skeleton role in plastic products, which has a great effect on the dimensional stability of plastic products, can improve the hardness of products, and can also improve the surface gloss and surface smoothness of products. Adding calcium carbonate to general plastic products can improve the heat resistance. Since the whiteness of calcium carbonate is above 90%, it can also replace expensive white pigments and play a certain role in whitening.
3. Paint industry
Calcium carbonate is used in a large amount in the paint industry, and it is an indispensable skeleton. The amount used in thick paint is more than 30%, and in phenolic enamel 4-7%, it is more than 39% in phenolic fine pattern wrinkle paint.
4. Water-based paint
The application in the water-based paint industry is more widely used. It can make the paint not settle, easy to disperse, and have good gloss. The dosage of water-based paint is 20-60%.
5. Others
In addition, calcium carbonate plays an important role in the paper industry to ensure the strength, whiteness and lower cost of the paper. It can play a certain insulating role in the cable industry. It can also be used as an abrasive in toothpaste