Kaolin is an important non-metallic mineral resource, mainly composed of small flake, tubular, laminated kaolinite cluster minerals (kaolinite, clay, pearlite, Eloite, etc.) less than 2 microns, widely used in ceramics, paper making, coatings, rubber, plastics, catalysts, adhesives, agricultural carriers and other fields.

1. Paper Making

Kaolin used in paper can increase the brightness and luster of paper, and improve the ink acceptance and smoothness of fiber paper. Kaolin can also be used as a substitute for pulp. There are two basic types of clay used in paper: filler clay and coated clay.

Filler clay: The main function of kaolin as a filler is to replace the expensive pulp mesh, thus reducing the cost. Actual loading levels depend on the type of pulp used and the end product requirements. The main advantage of kaolin over its competitor calcium carbonate is also the chemical inertness of kaolin to other papermaking materials. In addition to reducing costs, kaolin fillers also improve opacity, brightness and printability.

Coating clay: Paper Unless properly coated, these papers are not suitable for modern printing. The filling paper can be thought of as a sheet of interlaced pulp fibers, with the Spaces between them partially filled with mineral particles. If this paper is printed in half tone, some of the tiny ink spots on the plate may not be able to contact the paper, which will lead to reduced printing quality. When kaolin is used as a coating clay, kaolin needs to meet the highest requirements in terms of quality, giving the paper a smooth, bright surface, and giving the paper good ink absorption properties and good opacity. In addition, the rheological properties of kaolin are also suitable for use in modern high-speed coating paper machines. A smooth surface is a prerequisite for the production of high gloss paper with good printability.

2, paint coating

Kaolin has excellent properties such as high chemical stability, high hiding power, high whiteness, good dispersion and suspension, which makes it occupy a large market share in the paint and coatings industry. At the same time, the specific surface area of kaolin after calcination will correspondingly increase, and the absorption capacity of ink will increase, in addition, the calcined kaolin is more resistant to brushing than the uncalcined, and the application effect is better in the exterior wall paint. It can be said that calcined kaolin makes kaolin have more good properties, making paint and coatings become the largest consumer market of calcined kaolin in China, especially high-grade coatings. At present, calcined kaolin with high whiteness and high quality is widely used in high-grade coatings.

3. Rubber

Kaolin is used in the rubber industry as a filler and reinforcing agent for rubber, which can improve the quality of rubber products. After adding kaolin powder into rubber, the physical and chemical properties of rubber products can be greatly improved, and the corrosion resistance, wear resistance and stability of rubber products can be improved. This is mainly because kaolin powder forms a composite material with better performance with rubber, the swelling index of modified kaolin composite is smaller, and the organic kaolin particles are better dispersed in the rubber matrix than kaolin. In addition, kaolin is rich in resources and low in price, which can significantly reduce the cost of rubber products. Therefore, rubber has become another important market for kaolin.

4. Plastic

Kaolin is mainly used as filler in the plastics industry. Because the calcined kaolin has a large adsorption area and activity, the application of it in plastics can adsorb conductive ions in plastics, thereby improving the performance of plastics, making plastics more flat, beautiful, and chemical corrosion resistance enhanced. In the plastics industry, calcined kaolin can replace titanium dioxide as a pigment, and calcined kaolin can replace more than 20% of titanium dioxide in plastics, and the optical properties of plastics are not significantly reduced. The addition of kaolin in the plastic film can also reduce the influence of infrared rays, and the insulation strength of plastics will be improved after the addition of calcined kaolin. Modified kaolin can also be applied to PE agricultural film, which can improve the night temperature in the greenhouse, make the light more uniform, and promote the thermal insulation effect of agricultural film.

5, wire and cable

Kaolin is also used in insulating electronic materials, organic polymer materials in insulating electronic materials accounted for a large proportion, because organic flame retardants have great harm to the environment, inorganic flame retardants are gradually replacing traditional organic flame retardants. Modified calcined kaolin has high insulation resistance, so it is widely used in insulating electronic materials. Because it also has the ability to resist seawater erosion, kaolin can also be used in the manufacture of submarine cables, so that the insulation performance of cables is greatly improved.

6. Ceramics and refractories

Clay is an essential raw material in ceramic products, accounting for 25-100% of the ceramic body. However, kaolin is just one of many clays used in the industry. The utilization rate of kaolin accounts for an average of 25% of pottery, 60% of porcelain, 20-30% of ceramic sanitary ware, and 20% of electric porcelain and wall tiles. Applications for refractories include the lining of open furnaces and blast furnaces in the steel industry, as well as cement and ceramic films.

The application of kaolin in the ceramics and refractory industry can be divided into two categories according to the firing color for the end use. White firing color is the most important in the production of ceramics and wall tiles. Firing color White is less important in refractory production.


7. Building materials

Kaolin is also widely used in cement-based materials. Metakaolin prepared by calcination and ultrafine grinding of kaolin at appropriate temperature is considered to be an admixture in a new generation of cement concrete, which can significantly improve and reduce the workability, strength and durability of cement base materials. At the same time, they also have a good inhibition effect on the self-shrinking and detachment phenomena that are common in high performance cement-based materials.

In addition to the above applications, kaolin also has many applications in refractory materials, environmental protection industry, textile industry, agriculture, medical chemical industry and other fields.

Post time: Sep-27-2023