Summary:Kaolin is a type of clay found in nature, It has a variety of other uses in products including papermaking, paint, rubber, cable insulation, specialty films and fertilizers.
Kaolin is a white or clay-like rock with various hues consisting mainly of tiny flaky or tubular kaolinite mineral crystals smaller than 2 microns. Kaolin is divided into three types: hard kaolin, soft kaolin and sandy kaolin. At present, there are more than 700 kaolin ore sites in China, and the proven reserves of more than 200 ore points are 3 billion tons.
Uses And Distribution Of Kaolin In Papermaking Industry
kaolin Uses In Papermaking Industry
Kaolin has become an essential mineral raw material for dozens of industries such as paper, ceramics, rubber, chemicals, coatings, medicine and national defense. Kaolin is widely used in the paper industry. There are two main areas, one is the filler used in the papermaking (or paper copying) process, and the other is the pigment used in the surface coating process. Kaolin is applied to papermaking, which can give the paper good coverage performance and good hiking gloss performance, and can also increase the whiteness, opacity, smoothness and printing adaptability of the paper, greatly improving the quality of the paper.
In the papermaking industry, the international market of kaolin is relatively prosperous, and its sales volume exceeds those of ceramics, rubber, paint, plastics, refractory materials and other industries.In pulp, kaolin usually does not react with its ingredients, is highly stable, and remains intact in the paper fiber.At the same time, kaolin particle size, strong mobility, mechanized production can ensure that the paper coating thickness is uniform.Because of the above properties, kaolin is generally used as paper filler and coating material in the production process.
As a filler, kaolin can fill the space between the paper fibers, increase the density of the paper, reduce the transparency of the paper, improve the flatness of the paper, and enhance the ability of the paper to absorb ink.Therefore, kaolin can partially replace expensive fillers as filling agent and brightening agent, without affecting the quality of products.Kaolin used as coating material, is the use of its coverage, the flake particles coated on the surface of the paper, enhance its smoothness, brightness, cleanliness, printability, opacity, etc., can improve the paper to ink inclusiveness, permeability and paper appearance.
Distribution Of Kaolin In China
The distribution of kaolin resources in China is relatively scattered, the grade is not high, most of them are coal-based kaolin (very few abroad), which need to be calcined or modified, and there are natural limitations for papermaking coating. According to the information currently understood, only the kaolin resources of Guangdong, Guangxi and Shahe in Hebei can be developed for paper coatings, so the resources are very valuable. In the mid-to-late 1990s, Shahe, Hebei Province, had fierce competition with Maoming kaolin in the domestic paper coating market, but it has gradually shrunk due to insufficient resources.
Application Of Kaolin In Other Industry
1.Application Of Kaolin In FCC Catalyst
Kaolin is used in FCC catalyst on the one hand as an adhesive catalyst carrier, mainly for FCC catalyst to provide good wear resistance, appropriate bulk density and other physical properties or as an active component accelerator;On the other hand, the all-clay type catalyst was prepared, that is, Y-type zeolite catalyst was directly grown by hydrothermal crystallization on kaolin microspheres.Due to the special preparation process, this kind of catalyst has excellent activity, stability, resistance to heavy metal, residual cracking property, gasoline selectivity, wear resistance and reproducibility, and the processing process is simple. It is a very promising FCC catalyst.
2.Application Of Kaolin In Ceramic Industry
In the ceramic industry, kaolin was used earlier than other industries and in very large quantities, usually accounting for about 20 to 30 percent of the formula.Kaolin can increase the content of Al2O3 in ceramics, and the mullite formation process is easier to proceed, thus improving the stability and sintering strength of ceramics.In ceramic sintering, the decomposition of kaolin into mullite is the process of forming the frame of ceramic body. This process can widen the firing temperature range, prevent the ceramic body from deforming easily, and improve the whiteness of ceramics.At the same time, kaolin itself also has the characteristics of bonding, plasticity, bonding, suspension and so on, which can improve the formability of porcelain clay and enamel, and is more conducive to the processing process of billet, grouting and ceramic forming.In addition, the ceramic process has requirements on the chemical properties, particle size, crystallization degree and other properties of kaolin. In order to ensure the quality of ceramic processing, various parameters of kaolin should be strictly controlled in industry.
3.Application Of Kaolin In Refractories Industry
Because of its high refractoriness, kaolin is usually used in the production and processing of refractory products.Refractory materials are mainly divided into firebrick and silicon aluminum cotton two categories, with high temperature resistance and pressure does not deformation characteristics.A series of high temperature clays, including kaolin, bauxite and bentonite, are collectively referred to as refractory clays.Some kaolin with low whiteness can not be used to process ceramics and papermaking, but it can become a high-quality raw material for refractories.Therefore, how to comprehensively develop and utilize kaolin, improve its utilization rate, and create an important market for refractory clay and refractory materials has become a new topic of concern.
4.Application Of Kaolin In Rubber Industry
Kaolin used in rubber industry, fill to the colloid mixture, can enhance the wear resistance of rubber, chemical stability and mechanical strength, prolong the curing time, also can adjust the rubber mixing, rheology, sulfide, improve the consistency of unvulcanized products, to prevent the collapse of soft, sag, drooping, flat tube, deformation, etc.Its rubber products permeability, water resistance, chemical activity, fire resistance and other characteristics have been greatly improved accordingly.At the same time, kaolin as a filler can also reduce the amount of other raw materials in rubber, greatly reducing the production cost of rubber without significantly affecting the performance of rubber.
5.The Application Of Kaolin In Paint Industry
Ti02, CaC03, talc, kaolin are the main mineral raw materials used in the paint industry.Among them, kaolin has requirements for its dispersibility, particle size, and the content of colored oxides.Because kaolin has white color, low cost, good fluidity and suspension, chemical inert, strong covering power and other properties, so it mainly plays the role of filling material and color material substitute in paint, and can reduce the demand for expensive dyes.Kaolin can improve the hardness of the coating, improve the quality of the coating, and make the coating have good anti-corrosion, opacity and anti-sedimentation.Kaolin with different particle size can be used in different kinds of paints. Kaolin with smaller particle size can be used in processing high-light paints or latex pigments, while kaolin with larger particle size can be used in processing dim light paints or flat light paints.Rinse kaolin is soluble in water and suitable for making latex pigments.Calcined kaolin is suitable for high temperature wear-resistant paint, light color paint for wall painting, and bottom paint for metal products. Its good advantages make calcined kaolin develop rapidly in the paint production industry.
6.Kaolin Is Used In The Plastics Industry
Kaolin as a filler, the general dosage of plastic is 15%~60%, its role is to make plastic products surface smooth, accurate size, chemical corrosion resistance, reduce thermal shrinkage and thermal fission, is conducive to the polishing and grinding process.Kaolin is often used as a fortifier in the production of PVC to improve the wear resistance of plastic products.The modified kaolin can also be used as a functional additive to improve the mechanical, thermal and electrical properties of polyester, nylon and other plastic products.In the production process of fiberglass reinforced polyester, the addition of kaolin produces a uniform, high-strength whole, which greatly improves the flow performance of large products (automobile bodies, hulls, etc.).In addition, in some plastic systems, kaolin can improve the dispersion, which is conducive to the surface finishing.
7.Kaolin Is Used In The Manufacture Of Glass Fiber For The Pool Kiln
Kaolin, which has a low iron content, is used in fiberglass manufacturing, mainly as a source of aluminum and silicon, and also to dull its luster.Pool kiln glass fiber wire drawing technology content is high, for glass fiber forming, the requirement to reach the quasi optical level.The quality and stability of kaolinite homogenized micropowder are the primary factors affecting the drawing process of glass fiber in the pool kiln. The alkali free glass fiber in the pool kiln has strict quality requirements for kaolinite homogenized micropowder.The optimum proportion of mineral types can greatly improve the quality of glass solution. The particle size of kaolinite homogenized micro powder is proportional to the melting reaction speed. The particle size composition should be narrow, and the water content should be greater than 0.5%, so it can not be used.
8.Application Of Kaolin In Cement-based Materials
Kaolin becomes metakaolin by dehydrating.Cement is usually prepared by means of alkali activation or used as an additive to concrete.Kaolin can improve the strength, workability and durability of concrete, and resist the self-shrinking phenomenon of concrete.Kaolin cement-based materials have excellent properties and wide application fields, and the development prospect is worthy of attention. However, the research in this field started late in China.With the continuous development and utilization of this material, China's social and economic construction will make great progress.
With the development of economy and science and technology, the application scope of kaolin is also expanding, the market coverage from a single daily use, construction, ceramics, electric porcelain, refractory materials, the development of paper, petrochemical, rubber, plastics, coatings and other dozens of industries, especially in recent years the demand of high-tech industries, kaolin products put forward a new topic, ultra-fine, magnetic separation, modification, bleaching, calcined soil was born accordingly. The rising demand for kaolin has contributed to the optimism of the kaolin milling industry.
Calcination system of kaolin (divided according to calcination temperature) includes low temperature calcination (below 650 degrees Celsius), medium temperature calcination (650-1050 degrees Celsius), high temperature calcination (1300-1525 degrees Celsius) and so on. Different calcination temperatures, the performance and use of the resulting products are also different. Low temperature calcination products are high-altitude stone phase, amorphous phase, high chemical activity, used for the synthesis of molecular sieves, aluminum salt chemical and plastic, rubber functional materials. Medium temperature calcined kaolin is silicon aluminum spinel, its whiteness is good, high opacity, used in the paper industry, coating industry, instead of titanium dioxide as a structural pigment. High temperature calcined kaolin is mullite and galena phase, which is used to produce mullite sand, refractory materials and special ceramics. However, the application of cement cementitious materials is on the high side, and the calcination temperature is generally between 600-900 degrees Celsius, which belongs to the low and medium temperature calcination range.
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