Main Application And Research Progress Of Coal-measure Kaolin
Coal-measure kaolin, as an associated mineral in coal-bearing sedimentary rocks, is generally gray or black, and its kaolinite content can usually reach 70%, mostly in the form of massive structure or worm-like crystal aphanitic structure, with a high degree of crystallization order. This kind of kaolin has a certain genetic relationship with the coal seam, and the general thickness can reach 0.3-0.5m.
Coal-based kaolin can be widely used in papermaking, coatings, rubber, plastics, white carbon and other fields through calcination, decarbonization and impurity removal, ultra-fine grinding and surface modification.
1. Paper Industry
Compared with titanium dioxide, calcined kaolin has more advantages in terms of ink absorption, covering rate and price, and can completely replace expensive titanium dioxide, especially suitable for high-speed blade coating machines.
2. Paint Industry
Kaolin is also an additive in the paint industry, which is reflected by reducing the viscosity of the paint, slowing down the settling speed, and improving the leveling and adhesion properties. Kaolin can improve the storage stability of coatings, the anti-floating and blooming properties of coatings, etc. Coatings have many strict requirements in terms of performance and durability, and kaolin as an additive can just meet these requirements.
The increasingly important environmental issues have led the coatings industry to look for alternatives, and many new types of coatings have emerged, such as powder coatings, water-based coatings, high-solid coatings and radiation coatings, which have continuously increased the demand for kaolin.
3. Agricultural Plastic Film
Kaolin has a long history as a plastic additive. The infrared light radiated from 7 to 25 µm accounts for 90% of the heat emitted from the earth’s surface to the atmosphere at night, and the coal-measure calcined kaolin has a good blocking effect on the infrared radiation with a wavelength of 7 to 25 µm. Calcined kaolin, talc and parenteral are used in plastic films, they block infrared light, can improve the thermal insulation of plastic greenhouses, promote early germination and early maturity of crops, and greatly reduce the growth cycle of crops in cold regions.
4. Rubber Industry
In rubber products, in order to ensure superior product performance and uniform rubber texture, it is necessary to increase the dispersion of various compounding agents in the rubber. Modified calcined kaolin is easy to be wetted by the rubber material, and eats powder quickly, can play a reinforcing effect, improve the production process and the mechanical properties of the product, etc., and is just similar to the surface polarity of the rubber material.
5. Water Glass And White Carbon Black
In the process of using coal-based kaolin as raw material to produce aluminum sulfate, aluminum chloride and other aluminum salts, a large amount of residues mainly composed of SiO2 will be produced. Dissolve the residues after acid leaching with caustic soda, and then filter the residues to remove alkali-insoluble substance, a sodium silicate solution is prepared. White carbon black is obtained by adding electrolyte to sodium silicate solution, using dilute sulfuric acid or hydrochloric acid to treat the precipitate, and then filtering, washing, drying and other series of operations.
6. Solid Polyaluminum Chloride
Traditional polyaluminum chloride is prepared from aluminum ash, metal aluminum and aluminum hydroxide. Because aluminum ash contains heavy metal poisonous impurities, metal aluminum and aluminum hydroxide raw material sources are limited, the preparation of polyaluminum chloride is restricted. The production of polyaluminum chloride from coal-series kaolin can improve product quality, reduce costs, and is beneficial to the environment and has good benefits.
7. Synthetic Cordierite
Since the content of cordierite is relatively small in nature, its technological performance is good and its scope of action is relatively wide. Synthesize cordierite with coal series kaolin, add magnesia and talc at the same time, and burn at high temperature, the content of cordierite can reach 90%.