Kaolin The Cornerstone of Ceramics for Millennia, a Universal Layered Functional Mineral Powder for the Entire Industry

Caulino, also known as porcelain clay, has kaolinite as its core mineral. It is a typical 1:1 type layered hydrous silicate mineral, named after Gaoling Village in Jingdezhen, Jiangxi Province. It is one of the world's oldest and most widely used non-metallic mineral materials. With its core characteristics of high plasticity, high whiteness, fire resistance, insulation, adsorption stability, and excellent dispersibility, kaolin spans the traditional ceramics and papermaking industries, while also deeply empowering emerging industries such as coatings, rubber and plastics, fiberglass, new energy, and daily chemical pharmaceuticals. After washing, calcination, and surface modification, it forms a complete product system, making it an essential functional filler supporting the improvement of manufacturing quality, cost reduction, and green development.

1. Mineral Structure and Core Physicochemical Properties

Kaolin's microstructure consists of alternating layers of silicon-oxygen tetrahedra and aluminum-oxygen octahedra. The weak interlayer bonding makes it easily dispersed in water, resulting in unique processing adaptability. Pure white and delicate, with a Mohs hardness of only 1–2.5 and a soft texture; it has a high melting point of 1785℃, outstanding fire resistance, stable chemical properties, and is resistant to acids and alkalis at room temperature. It is non-radioactive, non-toxic, and harmless (according to Douyin Encyclopedia).

Superior plasticity and binding properties: Forms a uniform clay upon adding water, allowing for arbitrary shaping. After drying and firing, it exhibits a dense structure, making it a core raw material for ceramic body forming.

High whiteness and fine texture with excellent coverage: High-quality washed kaolin achieves a whiteness of over 90, while calcined products exceed 92. Particle size is controllable from 1250 to 8000 mesh, resulting in a smooth powder that can partially replace titanium dioxide, reducing formulation costs.

Insulating and high-temperature resistant: Dense lattice, low thermal conductivity, and high insulation strength make it suitable for high-temperature applications in cables, electronic substrates, and refractory materials.

Controllable adsorption and rheology: Layered pores possess physical adsorption capabilities. Washed kaolin exhibits excellent suspension properties, while calcined kaolin has a moderate oil absorption value, allowing for adjustment of thickening and anti-settling effects in coatings and resin systems.

Safe, environmentally friendly, non-irritating, and free of heavy metal impurities. After purification, it can be used in cosmetics, food additives, pharmaceutical carriers, and other applications involving contact with the human body.

Impurities such as iron and titanium oxides directly affect whiteness. Industry-standard magnetic separation, flotation, and bleaching processes are used for impurity removal, reducing iron content to below 0.1%, meeting stringent high-end manufacturing standards.

1. Mainstream Categories and Deep Processing TechnologiesBased on processing methods, the market is divided into three main categories: washed kaolin, calcined kaolin, and surface-modified kaolin. Dry and wet production lines operate in parallel to adapt to different mineral sources and demands.

1. Washed Kaolin(Hydrated Kaolin) is suitable for soft sedimentary kaolin ore. The wet process is as follows: raw ore pulping → gravity sand removal → high-gradient magnetic separation for iron removal → flotation bleaching → pressure filtration dewatering → spray drying → ultrafine grading. It retains natural crystal water, has excellent plasticity, fine particles, and strong water dispersibility, making it ideal for daily-use ceramics, paper coating, water-based coatings, and cosmetic raw materials. Its disadvantage is moderate thermal stability, making it unsuitable for long-term use in high-temperature environments.

2. The mainstream processing route for calcined kaolinfrom hard coal-series kaolinite involves crushing and grinding followed by high-temperature calcination at 600–900℃ to remove water of crystallization, resulting in crystal structure reorganization. After calcination, whiteness, hiding power, and temperature resistance are significantly improved. The pores are highly developed, adsorption capacity is enhanced, and it does not absorb water or soften. It is widely used in industrial coatings, plastics, rubber, refractory materials, and lithium battery separator coatings, and is one of the fastest-growing product categories in recent years, with the domestic market size exceeding 12 billion yuan.

III. Diversified Application Scenarios Across Industries

(I) Ceramic Industry (Traditional Core Track, accounting for 25% of total demand): Kaolin is hailed as the soul of porcelain. Adding it to the body imparts plasticity and forming strength to the clay, while enhancing the gloss and smoothness of the glaze. Applications include sanitary ware, tableware and teaware, architectural tiles, artistic ceramics, and refractory ceramics. High-purity, low-iron kaolin, after firing, is pure white and translucent, making it an essential raw material for high-end bone china and antique-style porcelain. Refractory-grade calcined kaolin is used in kiln furniture, refractory bricks, and high-temperature crucibles, withstanding temperatures up to 1000 degrees Celsius without deformation.

(II) The paper industry (the world's largest consumer sector, accounting for 35% of demand) is divided into two categories: paper fillers and coated kaolin. Filler-grade kaolin is added to pulp to improve paper smoothness and opacity, reducing wood pulp consumption. Coated ultrafine kaolin is used in coated paper, art paper, and label paper, resulting in uniform ink absorption, high gloss, and significantly improved print clarity, making it an irreplaceable raw material in the printing industry. Global demand for kaolin in the paper industry has remained stable year-round, with high-end ultrafine peelable kaolin continuing to be imported and replaced. (III) Coatings and Inks Industry

Water-based coatings: Water-washed kaolin provides suspension stability, thickens and prevents sedimentation, improving film smoothness and washability.

Industrial oil-based paints and powder coatings: Calcined kaolin provides high opacity, weather resistance, and UV resistance, partially replacing titanium dioxide, reducing production costs, and enhancing film wear resistance and corrosion resistance.

Printing inks: Modified kaolin adjusts ink viscosity, prevents show-through, and improves color saturation, making it suitable for plastic printing and offset printing inks.

(IV) Plastics, Rubber, and Glass Fiber

Rubber and plastic fillers: Calcined modified kaolin fillers for PVC, PP, ABS, and various rubbers improve product rigidity, heat resistance, aging resistance, and dimensional stability, reducing resin usage; added to tires and seals to enhance wear resistance and tear resistance.

Glass fiber: As an aluminum-silicon raw material, kaolin stabilizes the melt composition of glass fiber, improves fiber strength, and reduces breakage rate; it is a standard mineral raw material in the glass fiber industry. (V) High-end New Energy and Electronics Sector (Growth Rate Over 18%): High-purity, ultrafine calcined kaolin is a special coating filler for lithium battery separators, offering high temperature resistance, insulation, and puncture resistance, significantly improving battery safety and cycle life; low-dielectric kaolin is used in 5G high-frequency substrates and wire and cable insulation layers to ensure signal stability; catalytic carrier-grade kaolin has abundant pores and is used for chemical waste gas catalysis and oil refining carriers, offering broad emerging growth potential.

(VI) Daily Chemicals, Pharmaceuticals, and Agriculture/Animal Husbandry:

Daily Chemicals: Purified kaolin adsorbs oils and is used in facial masks, talcum powder, and toothpaste abrasives, providing gentle skin protection;

Pharmaceuticals: Non-toxic, high-purity kaolin is used as an antidiarrheal excipient, a glidant for tablets, and an adsorption matrix for ointments;

Animal Husbandry: Feed-grade kaolin adsorbs intestinal mycotoxins, improves and conditions saline-alkali compacted soil, and retains fertilizer and water.

(VII) Refractory materials, including refractory castables, fireproof boards, white cement, and interior/exterior wall putty, enhance fire resistance, heat insulation, and crack resistance, improving the overall strength of building materials at low cost. IV. Domestic Industry Structure and Development Trends my country has abundant kaolin reserves, with Jiangxi, Guangdong, Jiangsu, Shanxi, and Inner Mongolia as core production areas. Soft washed ore and coal-series calcined ore resources complement each other, comprehensively covering the high, medium, and low-end markets. High-end processing: Upgrading from ordinary coarse powder to ultrafine, low-iron, nano-exfoliated, and surface-modified products; accelerating domestic substitution of high-purity kaolin for lithium batteries and electronics.

Green and intelligent production: Closed-loop recycling of wastewater from wet processing lines; low-carbon transformation of calcining kilns; intelligent mineral processing in mines to improve resource recovery rates and reduce dust pollution, aligning with dual-carbon policies.

Specialized product segmentation: Independently customized indicators for ceramic grade, paper coating grade, lithium battery coating grade, and rubber and plastic modified grade, precisely matching downstream operating conditions.

Comprehensive processing of coal-series kaolin, tailings, and associated mining waste to improve resource utilization and reduce raw material costs.

Conclusão: From the warm and lustrous porcelain of ancient towns to the exquisite printing of books, from home decoration wall coatings and plastic daily necessities to the safety barrier of new energy power batteries, kaolin has continuously empowered human production and life for thousands of years. Leveraging its unique layered silicate structure, kaolin possesses multiple advantages, including plasticity, fire resistance, insulation, adsorption, and low cost. It serves as a fundamental raw material for the traditional ceramics and papermaking industries, and is also a key functional powder for technological upgrades in new energy and high-end manufacturing. Against the backdrop of high-quality, green, and low-carbon development in manufacturing, the market for high-purity, ultrafine kaolin continues to expand as purification, calcination, and surface modification technologies continuously iterate. As a highly versatile non-metallic mineral material, kaolin will continue to play an irreplaceable supporting role in the upgrading of traditional industries and the breakthroughs in emerging industries.