Kaolin is a non-metallic mineral, which is a type of clay and clay rock mainly composed of kaolinite group clay minerals. Due to its white and delicate appearance, it is also known as Baiyun soil. Named after Gaoling Village in Jingdezhen, Jiangxi Province.

Its pure kaolin is white, delicate, and soft in texture, with good physical and chemical properties such as plasticity and fire resistance. Its mineral composition is mainly composed of kaolinite, halloysite, hydromica, illite, montmorillonite, as well as minerals such as quartz and feldspar. Kaolin has a wide range of uses, mainly used in papermaking, ceramics, and refractory materials, followed by coatings, rubber fillers, enamel glazes, and white cement raw materials. In small amounts, it is used in plastic, paint, pigments, grinding wheels, pencils, daily cosmetics, soap, pesticides, pharmaceuticals, textiles, petroleum, chemical, building materials, national defense and other industrial sectors.

Process characteristics
Folding Whiteness Brightness

Whiteness is one of the main parameters for the technological performance of kaolin, and high-purity kaolin is white. The whiteness of kaolin is divided into natural whiteness and calcined whiteness. For ceramic raw materials, the whiteness after calcination is more important, and the higher the calcined whiteness, the better the quality. The ceramic process stipulates that drying at 105 ℃ is the grading standard for natural whiteness, and calcining at 1300 ℃ is the grading standard for calcined whiteness. The whiteness can be measured using a whiteness meter. The whiteness meter measures the brightness of 3800-7000Å A device for measuring the reflectivity of light at a wavelength of (i.e., 1 angstrom=0.1 nanometers). In a whiteness meter, the reflectance of the test sample is compared with that of the standard sample (such as BaSO4, MgO, etc.), resulting in a whiteness value (such as a whiteness of 90, which is equivalent to 90% of the reflectance of the standard sample).

Brightness is a process property similar to whiteness, equivalent to 4570Å The whiteness under (angstrom) wavelength light irradiation.

The color of kaolin is mainly related to the metal oxides or organic matter it contains. Generally containing Fe2O3, it appears rose red and brown yellow; Containing Fe2+, it appears light blue and light green; Containing MnO2, it appears light brown in color; If it contains organic matter, it appears in light yellow, gray, blue, black and other colors. These impurities exist, reducing the natural whiteness of kaolin. Among them, iron and titanium minerals can also affect the calcined whiteness, causing color spots or melt scars on porcelain.

Folding particle size distribution
Particle size distribution refers to the proportion of particles in natural kaolin within a given continuous range of different particle sizes (expressed in millimeters or micrometer mesh), expressed in percentage content. The particle size distribution characteristics of kaolin are of great significance for the selectivity and process application of ores. Its particle size has a significant impact on its plasticity, mud viscosity, ion exchange capacity, forming performance, drying performance, and firing performance. Kaolin ore requires technical processing, and whether it is easy to process to the required fineness has become one of the standards for evaluating ore quality. Each industrial department has specific requirements for the particle size and fineness of kaolin for different purposes. If the United States requires kaolin used as a coating to be less than 2 μ The content of m accounts for 90-95%, and the paper filling material is less than 2 μ M accounts for 78-80%.

Fold binding
Adhesion refers to the ability of kaolin to combine with non plastic raw materials to form plastic mud masses and have a certain degree of drying strength. The determination of binding ability involves adding standard quartz sand (with a mass composition of 0.25-0.15 particle size fraction accounting for 70% and 0.15-0.09mm particle size fraction accounting for 30%) to kaolin. Judging its height based on its highest sand content when still able to maintain a plastic clay mass and its flexural strength after drying, the more sand is added, the stronger the binding ability of this kaolin. Usually, kaolin with strong plasticity also has strong binding ability.

Folding adhesive
Viscosity refers to a characteristic of a fluid that hinders its relative flow due to internal friction. Its magnitude (acting on 1 unit area of internal friction) is represented by viscosity, in units of Pa · s. The determination of viscosity is generally measured using a rotational viscometer, which measures the rotational speed in kaolin mud containing 70% solid content. In the production process, viscosity is of great significance. It is not only an important parameter in the ceramic industry, but also has a significant impact on the papermaking industry. According to data, when using kaolin as a coating in foreign countries, the viscosity is required to be about 0.5Pa · s for low-speed coating and less than 1.5Pa · s for high-speed coating.

Thixotropy refers to the characteristics that the slurry that has been thickened into gel and no longer flows becomes fluid after being stressed, and then gradually thickens into the original state after being static. The thickness coefficient is used to represent its size, and it is measured using an outflow viscometer and a capillary viscometer.

The viscosity and thixotropy are related to the mineral composition, particle size, and cation type in the mud. Generally, those with high content of montmorillonite, fine particles, and sodium as the main exchangeable cation have high viscosity and thickening coefficient. Therefore, in the process, methods such as adding highly plastic clay and improving fineness are commonly used to improve its viscosity and thixotropy, while methods such as increasing diluted electrolyte and water content are used to reduce it.