Overview of the uses of calcium carbonate
Calcium carbonate is divided into two categories: light calcium carbonate and heavy calcium carbonate. In nature, it exists in limestone, calcite, chalk, marble and other minerals, and also in clams, oysters and other shells. According to the crystal structure, it is mainly divided into the following three categories: ① Aragonite. It is an orthorhombic white crystal. ②Calcite type (Calcite). Hexagonal white crystal. Insoluble in water, soluble in acid and ammonium chloride, and also soluble in water containing carbon dioxide. ③In addition to the above two types, there is also a vaterite type calcium carbonate, which is actually calcium carbonate hexahydrate and is not commonly available on the market.
Uses of calcium carbonate
Calcium carbonate is used as a raw material for building materials, ceramics, glass, lime, cement, etc.; it is also used in the manufacture of chalk, putty, artificial stone, fillers, pigments, neutralizing agents, polishing agents; sugar clarifiers; super Finely divided calcium carbonate is used in medicine. Light calcium carbonate is mainly used in the paper industry, interior decoration materials, handicrafts, and medicine.
Use of calcium carbonate 1. Application in rubber industry
Calcium carbonate was first used in the rubber industry and is one of the most widely used fillers. The rubber industry is also one of the main application markets of nano calcium carbonate. It can be used in rubber products such as tires, hoses, tapes, sealing rings, and auto parts. Nano calcium carbonate first has the properties of ordinary calcium carbonate. At the same time, due to its ultra-pure, ultra-fine, and surface-modified characteristics, it has a spatial three-dimensional structure and good dispersion in rubber, which can improve the tensile properties of the material. Reinforcement and anti-aging properties. It can not only be used as a reinforcing filler alone, but can also be used in combination with other fillers (white carbon black, carbon black, light or heavy calcium carbonate, titanium dioxide, clay, etc.) to fill, reinforce, color, and improve product performance. and processing technology to reduce the glue content or partially replace expensive white fillers such as titanium dioxide and white carbon black to reduce costs. Nano-calcium carbonate used in the rubber industry requires small particle size, high surface activity and good dispersion. Nano-calcium carbonate was compounded with UV surface-treated SB pinacol ester S rubber, and the effect of nano-calcium carbonate on the surface oxidation of SBS rubber was studied.
Use of calcium carbonate 2. Application in plastic industry
At present, the industry with the most mature application technology of nano-calcium carbonate is the plastics industry, and the demand for calcium carbonate in the plastics industry is also very large. Because nanometer calcium carbonate has unique and excellent properties, it can become a regulator, reinforcing agent and semi-reinforcing agent for plastics. Nano-calcium carbonate has small particle size and good dispersion. It can reduce pores and voids in plastics and make the mixing and shrinkage of plastics more uniform. Therefore, it can be filled in polymers such as polystyrene, polyvinyl chloride, aldehydes, and phenolic plastics. to improve the dimensional stability, hardness and rigidity of plastic products. At the same time, because active nano-calcium carbonate has lipophilic and hydrophobic properties, it can greatly improve the toughness, rigidity, bending strength and smoothness of the product, improve its heat resistance, dimensional stability and other processing properties, and can partially replace other expensive fillers and auxiliary materials. agents, thereby reducing product production costs and improving market competitiveness.
Use of calcium carbonate 3. Application in paper industry
The use of nano-calcium carbonate in the paper industry has the following advantages: 1) The whiteness and light-shielding properties of paper products are significantly improved; 2) Nano-calcium carbonate causes less wear on paper, making paper products more uniform and smooth; 3 ) Reduce the amount of pulp and increase the amount of filler, reducing production costs; 4) Nano-calcium carbonate has good oil absorption, which improves the pigment fastness of colored paper; 5) When filling neutral paper or cardboard, nano-calcium carbonate can improve their tightness Spend. At present, nano-calcium carbonate is mainly used in thin printing paper, recording paper, high-whiteness coated paper, cigarette paper, disposable diapers, high-end sanitary napkins, etc. Nano-calcium carbonate can also improve the apparent fineness, bulk and water resistance of paper; increase the printing speed and strength of special paper; adjust the burning speed of cigarette paper, etc.
Use of calcium carbonate 4. Application in coating industry
Nano calcium carbonate is the market with the most development potential as a pigment filler. At present, the amount of calcium carbonate used in the coatings industry is growing rapidly. Calcium carbonate has the advantages of fineness, uniformity, high whiteness, and good optical properties in the coating industry. When added to water-based coatings, it can greatly improve the reinforcement, transparency, thixotropy, and leveling properties of the system, and significantly improve the quality of the coating. Stain resistance, wash resistance, adhesion, and anti-settling effect. The application of nano-calcium carbonate in exterior wall coatings can improve its pollution resistance and crack resistance due to the strong hydrophobicity of the coating. Nano-calcium carbonate can replace expensive titanium dioxide in large quantities, while reducing the amount of tetrafluoroborate used in other additives, significantly reducing the production cost of coatings.
Use of calcium carbonate 5. Application in ink industry
The ink formulated with nano-calcium carbonate has good texture and viscosity, good printing performance and good stability. Because the particles are small, the printed product is smooth, with complete dots and strong hiding power. Nano-calcium carbonate is used as a filler to improve the brightness and gloss of the ink. It can also show good ink absorption during the ink printing process, which helps to improve the quick-drying performance of the ink. When nano-calcium carbonate is used as a filler in ink, in addition to the role of a general ink filler, it also has the advantages of good stability, high gloss, strong adaptability, and does not affect the drying characteristics of the ink. It is also cheap and can reduce costs. Nano-calcium carbonate is used in high-end inks, which can improve the adhesion of the ink, reduce the wear of the ink on machinery, and is suitable for high-speed printing.
How to use calcium carbonate
Light calcium sulfate is made by crushing and roasting limestone to generate lime milk, then moving it into a reaction tank, and finally precipitating calcium carbonate, filtering and drying. The production method of heavy calcium carbonate is to crush the raw limestone into granules of 60 to 200 mesh and 100 to 150 mesh according to different uses. This method is dry crushing. It can also be crushed by wet method, that is, limestone is washed and dried. The preparation method of purer calcium carbonate is to use an aqueous solution of sodium carbonate, add calcium chloride solution to it, and carry out a metathesis reaction. What is prepared in this way is called precipitated calcium carbonate.
Calcium sulfate can also be produced by passing carbon dioxide into milk of lime. If natural marble is used as raw material, it can be decomposed with dilute hydrochloric acid (12%) to generate a calcium chloride solution, to which calcium hydroxide is added. After removing iron and manganese impurities, the filtrate is heated, and ammonium carbonate is added to precipitate calcium sulfate. , a small amount of calcium hydroxide in the solution is also converted into calcium sulfate and precipitated. Finally dried at 200°C.
