Yuan Lei's Little Knowledge | Application of Kaolin in Coatings

Release time:

2024-01-29 09:35

my country is the world's major kaolin producer. In 2020, my country's kaolin production will be about 6.5 million tons, an increase of 30% year-on-year. It is expected that my country's kaolin production will also stabilize at about 6.4 million tons in 2021.

At present, China's kaolin export major provinces and cities for Guangdong Province, Fujian Province, Shanxi Province and Jiangsu Province. In 2021, Guangdong Province exported the largest amount of kaolin, 236600 tons, accounting for about 23.8 of the total kaolin exports, followed by Fujian Province, 227900 tons; Shanxi Province, 136400 tons; Jiangsu Province, 86000 tons.

In 2015, the consumption of calcined kaolin in China was about 4.37 million tons, and the consumption of ceramics, papermaking and coatings was the largest, totaling about 4.05 million tons, of which 400000 tons were consumed in the coating field, accounting for 9%.


Kaolin is mainly used as a filling skeleton in the production of paint coatings. At the same time, because kaolin has excellent dispersibility, stable chemical properties, corrosion resistance and fire resistance, it can be used as an additive in the production of coatings to improve the adsorption capacity and hiding capacity of coatings.

The raw material commonly used in the coating industry is titanium dioxide, which is expensive and prone to chemical pollutants. Replacing titanium dioxide with a chemically stable natural mineral kaolin can reduce costs and moderate pollution.



(1) Application in architectural coatings

Architectural coatings as a building decoration, protective materials painted on the surface of the building, it is required to have a certain degree of fineness, adhesion, hiding power, stain resistance, scrubbing resistance, aging resistance, heat resistance, leveling, shorter drying time, suitable lower film temperature, etc. Due to the plasticity, viscosity, high strength and chemical stability of non-metallic minerals, people in the preparation and modification of architectural coatings, commonly used non-metallic minerals are bentonite, diatomite, kaolin and rectorite.

With the development of the real estate industry, the global demand for architectural coatings is increasing, and people have higher and higher requirements for the quality and functionality of architectural coatings. High-performance, high-grade, and cost-effective coatings are becoming more and more popular. welcome. Especially for the improvement of environmental protection requirements, it is necessary to develop architectural coatings with anti-pollution and pollutant control properties. Kaolin has a special application in architectural coatings, and it will have a broad application prospect in the modification of architectural coatings.

(2) Application in paper coating industry

The pigments in paper coating are mainly kaolin and CaCO. And TiO2, of which kaolin accounts for about 90% or more.

All kaolin used for coating is dry or wet selection. The wet selection product is more uniform, contains fewer impurities, and has better brightness and whiteness than the dry selection product. The coated paper presents a strong pearl luster suitable for offset printing, mainly used for boutique packaging, business cards, high-end calendars.

(3) Application in latex coatings and paints

Kaolin has long been used as a filler in latex coatings and paints. This is due to its chemical inertness, good fluidity, white color and low price. At the same time, the surface is easy to modify, so that its suspension in the coating can be improved.

Kaolin has a wide range of particle sizes suitable for use in the coatings industry. For example, coarse-grained kaolin is used in matt or flat paints, and fine-grained kaolin is used in high-gloss paints or latex paints.

In the coating industry, there are two types of kaolin that are often used, one is washed ultrafine kaolin, and the other is calcined ultrafine kaolin. Calcined kaolin is a new type of functional filler developed in recent years. As a coating filler, it not only has high whiteness and opacity, but also can provide good stability and color in polymers, but also has good hiding power, soft and wear-resistant, and has anti-abrasion, non-shrinkage and other characteristics.

As a white filler, kaolin does not have hiding power by itself. However, if it is added to the white paint in a certain proportion, it can act as an extender and improve the hiding power of the paint. Adding an appropriate amount of kaolin and reducing the amount of the main pigment can still make the hiding power of the latex paint or paint unchanged, while the cost of the product is reduced.

(4) Application in waterborne coatings

Because of its white color, low price, good fluidity, stable chemical properties and large surface cation exchange, kaolin has long been used as a filler for coatings and paints. Kaolin used for coatings is generally washed ultrafine kaolin and calcined ultrafine kaolin. Calcinated kaolin is just developed in recent years, as a new functional additive, has good whiteness, coverage, softness, abrasion resistance, opacity, non-shrinkage, and in high polymer coating to maintain good color and stability. Kaolin itself is white, used as an additive and no coverage, but if the right amount is added to the white paint or paint, it can play a role in enhancing gloss and improving its covering ability.

It should be noted that the ratio of the matrix of the aqueous coating to the powdery material in the coating also has a great influence on the hiding power of kaolin. The reason is that the refractive index of the coating matrix is close to that of kaolin. When the matrix is used in a large amount, the interface of kaolin particles will be covered by it, thus reducing the refraction, reflection and scattering generated by the interface, thus reducing the hiding power.

In materials, kaolin, coatings, tons, as, with, construction, application, covering power, paint.

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