Coal based kaolin is widely used in various industrial fields due to its simple mineral composition, pure chemical composition, high temperature resistance, good dispersibility, stable chemical properties, and excellent electrical insulation properties. For the development and application of coal based hard kaolin, specific introductions will be made to its application in the following industrial fields:
Chemical industry
(1) In the production of aluminum compounds, the content of Al2O3 in coal based kaolin is generally high, mostly between 35% and 39%. After in-depth chemical industrial processing, various high value-added aluminum salt products such as alumina and nanoscale can be produced α- Aluminum oxide.
① AlCl3- serves as a hardening agent in the field of precision casting; Used as a hydrocracking agent in the petroleum industry; Serve as a sizing and precipitation agent in the papermaking industry; In addition, it is also used as a wood preservative, sewage separation agent, etc.
② Aluminum sulfate is mainly used as filler in paper industry, and is also used in wood preservation, foam fire extinguishing, flocculant, mordant, medical astringent and other fields.
③ Al (OH) 3- used as a smokeless flame retardant filler in polyvinyl chloride plastics and polymers; Used as a catalyst and flame retardant filler for synthesizing rubber products; As a whitening and brightening agent, it is used in papermaking and as a filler for artificial carpets.
④ Nanoscale α- Al2O3 is used in the electronic industry to produce integrated circuit substrates, transparent ceramic lamps, magnetic tapes, and fluorescent powders as raw materials for high-performance structural ceramics and laser materials.
(2) Production of silicone, water glass, and white carbon black
During the chemical production of aluminum salts from coal based kaolin, a large amount of reaction residues are generated, mainly composed of SiO2, which can be used as raw materials for processing and producing sodium silicate and white carbon black. Dissolve the acid leaching residue in caustic soda, filter and remove the residue, then add an electrolyte to the sodium silicate solution, and through acidification treatment, precipitate the hydrated SiO2. After treatment, the product is filtered, washed, and dried to obtain white carbon black.
(3) Synthetic zeolite
In recent years, scholars have conducted in-depth exploration on the application of coal based calcined soil to prepare zeolite. High quality coal based kaolin has a molecular ratio of Al2O3/SiO2 similar to 4A molecular sieve, making it suitable for the production of zeolites. The hydrothermal crystallization method can generate different types of zeolites such as A, X, Y, etc. Among them, 4A zeolite is used as a detergent additive and can replace sodium tripolyphosphate in the production of phosphorus free laundry detergent and detergent, thereby reducing environmental pollution.
Application in the field of building materials
(1) Geopolymer cement
As a new type of cementitious material, geopolymer cement is mainly composed of amorphous minerals, and the mineral composition of geopolymer cement is significantly different from that of Portland cement. The main valence bonds of geopolymer cement are ionic bonds and covalent bonds, with van der Waals bonds only playing an auxiliary role, while traditional cement uses van der Waals bonds and hydrogen bonds as the main valence bonds, resulting in superior performance of geopolymer cement compared to traditional Portland cement.
(2) Concrete admixtures
After high-temperature calcination, the calcined product of kaolin (mainly metakaolin) exhibits an irregular arrangement of atoms inside, and is thermodynamically in a metastable state, making it prone to chemical hydration reactions with water. Hydrated products include CSH gel, hydrated calcium aluminate, hydrated sulfur calcium aluminate, etc., which can replace silica fume and generally fill in concrete admixtures.
(3) Paint coatings
At present, paint coatings are the main application area of calcined kaolin in China, and kaolin mainly serves as a filler and color substitute in paint coatings. For applications in paint coatings, calcined coal based kaolin has obvious advantages. In addition to having the chemical inertness of ordinary kaolin, high coverage ability, ideal suspension flowability, low cost, white color, and reducing the need for expensive dyes, it also has advantages such as excellent optical properties, irregular shape, high oil absorption rate, high pigment volume concentration, difficult aging, wear resistance, and easy emulsification in water or oil media.
Application in the rubber and plastic industry
After surface modification, the calcined coal based kaolin has similar surface polarity to the rubber material, is easy to be wetted by the rubber material, has a fast powder feeding efficiency, can enhance the dispersion effect of the rubber material, and achieve good reinforcement effect of the rubber particles.
(1) Application in rubber
After modification, conventional calcined kaolin can be added to rubber to achieve a semi reinforcing effect or more. In addition, it can promote colloid crosslinking and dispersion to a certain extent, improve vulcanization efficiency, enhance processing performance, and increase filling amount and economic benefits.
(2) Applications in plastics
Calcined kaolin is used as a filler in engineering and general plastics, with a filling amount generally ranging from 20% to 40%. Coal based calcined kaolin used for plastics can effectively improve and enhance performance parameters such as glass transition temperature, tensile strength, and modulus. In addition, coal based calcined kaolin is often used as an additive in agricultural plastic greenhouse films due to its ability to effectively block far-infrared radiation. It has the functions of maintaining a relatively appropriate day and night temperature inside the greenhouse, enhancing the fog free effect of agricultural films, and improving the uniformity of lighting. It is an ideal auxiliary for insulation of agricultural films.
Paper filling material
Calcined kaolin is applied in the papermaking industry, mainly as a filler in the papermaking industry. After surface modification and coating with titanium dioxide, coal based calcined kaolin has similar functions to titanium dioxide. Due to its high coloring and covering power, it is particularly suitable for use in high-speed scraper coating machines.
Industrial porcelain
(1) Ceramics
Ceramics for high-temperature structures have developed rapidly in recent years, widely replacing traditional metal materials in the field of high-temperature engineering materials. This type of ceramic material has good chemical corrosion resistance, thermal seismic resistance, and high-temperature stability. Using flowing argon gas for atmosphere control, SiCw/Al2O3 ceramic powder was prepared by compounding natural kaolin and nanoscale carbon black at high temperature. The generated SiC whiskers had a diameter of less than 200nm and a length exceeding 5um. The ceramic powder produced by this method has significantly improved properties such as fracture toughness, thermal shock resistance, and bending strength.
(2) Electric porcelain
In the research on the development and utilization of kaolin raw materials in the western region of Heilongjiang Province, high-voltage and low-voltage electrical ceramics that meet China's national industrial standards are produced based on ceramic raw materials from industrial sites, supplemented by raw materials from our province and other regions.
(3) Enamel
As a composite material, the main principle of enamel is to melt and condense inorganic glassy materials onto the matrix metal framework, thereby firmly connecting them. Kaolin is used for enamel and is filled with inorganic glassy materials. Enamel products are safe, non-toxic, and easy to clean. They are widely used as food utensils and washing utensils in daily life. There are a variety of enamel varieties, and according to their different uses, their industrial fields mainly include art, daily use, hygiene, architecture, industry, special and other different enamel categories.
Polymer materials
(1) Insulating electronic materials
Coal based calcined kaolin, after modification, can effectively improve its insulation resistance and is harmless to the environment. Therefore, it has been widely studied as a substitute for organic flame retardants that were previously harmful to the environment. Nowadays, modified coal based calcined kaolin flame retardants have been applied to phenolic resin type flame retardant copper-clad laminates and their laminated insulation boards.
(2) Raw materials for fiberglass products
Glass fiber, as a type of inorganic non-metallic material, is the main member of today's material system with excellent performance. Exploring the application of ultrafine kaolin in the production of alkali free tank kiln glass fiber and chlorinated butyl rubber based on the chemical composition and ore characteristics of kaolin. The exploration results show that this type of coal series kaolin has broad development prospects in the fields of glass fiber and rubber.
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