Kaolin is a mixture of inorganic nonmetals. Calcination of kaolin means that kaolin is sintered in a calcining furnace to a certain temperature and time, so that its physical and chemical properties can be changed to meet certain requirements.
Calcined kaolin is produced by ultrafine grinding and calcination modification with advanced equipment.The product has a pseudo-hexagonal porous and lamellar structure, and the porosity is about 75%.The porous and lamellar structure of kaolin has the advantages of plasticity, adhesion, dispersion, insulation, sintering, flame retardancy, fire resistance, adsorption, weathering resistance, chemical stability, high light scattering rate, good hiding power and so on.Widely used in papermaking, coating, papermaking filler, plastic, rubber, wire and cable, latex paint, road sign paint, powder coating and other fields.
Function of calcined kaolin in paints and coatings:
Calcined kaolin raw ore is mainly produced in the coal producing areas of North China, mainly Inner Mongolia and Shanxi. It belongs to sedimentary type. It is formed by grinding hard kaolin generated from coal seam for many times and calcining at high temperature. After such processing, calcined kaolin molecules lose crystal water and present fluffy porous sheet structure. Calcined kaolin has the characteristics of high whiteness, strong covering power, good fluidity, high oil absorption and good suspension. The properties of coatings and films obtained by adding this kind of fine calcined kaolin in latex paint will make us feel that kaolin is not only a common filler, but also a functional filler to improve the quality of paints and coatings.Calcined kaolin used in paints and coatings has the following advantages:
- Due to its hexagonal crystal structure and high refractive index, it greatly improves the contrast index (covering power) of the coating film and provides excellent color ductility.
- The flat property of kaolin can provide a good balance between the fluidity and leveling of paints and coatings. Flat particles also tend to have a flat surface.For sticky film, flat particles can improve the compressive adhesion of the paints and coatings.
- Kaolin is hydrophilic, so it is easy to disperse, with small bulk density and good suspension performance.
- It has a narrow range of colloidal particles, tends to keep the viscosity of the coating unchanged, and can provide the required rheological properties and contactdenaturation (high shear high flow and low shear low flow), so the film is relatively full, and can improve the floating color and the defects of the flower.
- Strong chemical inertness, small optical axis angle and high order of crystal shape will significantly increase the UV shielding ability of the paints and coatings.
Function of calcined kaolin in ceramics and glazes:
The function of kaolin in glazes is to form vitreous material.The ideal chemical formula of kaolin is Al2O3-2SiO2-2H2O, which, like quartz, feldspar, marble, etc., is the main component of forming glass.
Kaolin is mainly composed of Al2O3 and a small amount of silicon dioxide.Alumina content is more, can improve the viscosity of the glaze, so that the glaze fixed in the bad body is not easy to flow away, but relatively will also increase the firing temperature of the glaze, and will affect the diffusion of the glaze, so that the crystallization is more difficult to produce.
Function of calcined kaolin in paper industry:
Pure kaolin has high whiteness, soft quality, easy dispersion and suspension in water, good plasticity, high adhesion, and excellent electrical insulation performance.It has good acid solubility, low cation exchange capacity, good fire resistance and other physical and chemical properties.Therefore, kaolin has become a necessary mineral raw material for dozens of industries such as papermaking, ceramics, rubber, chemical, coating, medicine and national defense.Kaolin is widely used in paper industry.
There are two main areas, one is in the paper in the use of fillers, the other is in the surface coating process used pigments.Especially in recent years, the rapid development of modern science and technology has made the application of kaolin more extensive. Some high-tech fields begin to use kaolin as a new material in large quantities. Even the high-temperature resistant porcelain parts of atomic reactors, space shuttles and spacecraft are also made of kaolin.
The paper industry is the largest consumer of refined kaolin, accounting for about 60% of total kaolin consumption.
Application of kaolin in rubber industry:
Kaolin used in rubber industry is made of high-quality raw materials by washing and refining. The product has fine particle size, low moisture, stable PH and DPG absorbency, and the settlement volume is higher than the index stipulated by the Chemical Industry Department.All kinds of rubber products produced by this product have low abrasion, good strength and bending performance.The product is a semi-strong filler for the production of various rubber products.
Differences between calcined kaolin and washed kaolin:
First of all, calcined kaolin is calcined, and its crystal form and original soil have changed.Water – washed kaolin is only treated physically and will not change the nature of the original soil.
Secondly, the whiteness of kaolin varies greatly. Generally, after light burning, the whiteness of kaolin will increase, while that of washing will not increase significantly.
Third, different USES.According to different calcination temperature, kaolin can be used as papermaking additive and refractory aggregate.
Washable kaolin is commonly used as a papermaking filler.
In addition, calcined kaolin mainly refers to hard kaolin (coal measure kaolin). The original soil has no bonding property and cannot be directly used as raw material for papermaking or refractory materials, so it needs to be applied after calcination.The raw material of washable kaolin has adhesive property and can be used as refractory binder or papermaking filler directly.It can improve the aging-resistant ability of the film, prolong its service life, improve its heat preservation and promote the growth of crops.Changing the polarity of the film surface and inhibiting the formation of fog drops;And will be harmful to the crops ultraviolet light or green light into photosynthesis can use red orange light, referred to as longevity, high heat preservation, anti-fog drops and light four functions, is a new master with functional filler.
As a papermaking filler, calcined kaolin has a better whiteness and a higher cost.
Inner Mongolia Rational Industry Limited (IMRI) is a supplier of all kinds of high whiteness calcined kaolin clay such as 6250 mesh calcined kaolin,325 mesh calcined kaolin,2000 mesh calcined kaolin,1250 mesh calcined kaolin,4000 mesh calcined kaolin,etc.Please send your inquiry and get quotation from us if you need any kind of calcined kaolin.