Fillers in coatings have a great influence on the properties of most colored coatings. There are many kinds of fillers, high purity kaolin because of its high whiteness, soft, easy to disperse suspended in water, with good acid resistance solubility, very low cation exchange capacity, good fire resistance and other characteristics, become an essential mineral raw material in the coating industry.

Kaolin was originally consumed by the paper industry as a cheap filler and is still widely used today. In recent years, manufacturers are making kaolin suitable for the paint industry. The main function of kaolin in paint is filler and color substitute. The filling property, grinding property and mechanical strength of the coating can be improved by adding a certain amount of filler into the coating. Kaolin in paint industry is mainly to replace white pigment, especially titanium dioxide; Different size and type of kaolin used in different types of paint: coarse kaolin used in need dark glossy or matt paint, fine kaolin is used to produce high gloss paint, or used in the manufacture of emulsion paint, can make the coating has good opacity, anti-corrosion and subsidence prevention, improve the coating hardness, improve the quality of coating. The original production of kaolin is simply through air drying and flotation, but now it has been replaced by water washing, strict particle size control, calcination and surface treatment, thus improving the grade of products. In these reforms, calcination is the most important process, so the scale is very large. In addition to the characteristics of ordinary kaolin, calcined kaolin also has the advantages of irregular shape, excellent optical properties, high oil absorption rate and pigment volume concentration, not easy to aging, wear resistance and easy emulsification in water or oil medium, with high hiding power, etc., is widely used in the paint and coatings industry.

The coating is filled with calcined kaolin, which can shield uv radiation, improve the weather resistance of the coating, delay the powdery discoloration, enhance the comprehensive mechanical properties of the coating and pollution resistance, self-cleaning, acid, alkali, high temperature resistance, improve the heat resistance and anti-corrosion properties of the coating. Paint coating is the largest consumption area of calcined kaolin in China, accounting for about 65%~85% of the total consumption. High quality calcined kaolin with whiteness of more than 90 and particle size of more than 1250 mesh is widely used in special functional coatings such as interior and exterior wall coatings, anti-corrosion coatings, powder coatings, heat-resistant coatings, insulation coatings, landmark coatings, waterproof coatings, anti-radiation coatings and so on.

China is the first country to discover and use kaolin, and is also the most important producer of kaolin. The production of kaolin is concentrated in Inner Mongolia and Shanxi. In 2002, the total output of kaolin exceeded 3.5 million tons, but the output of washed, cleaned and calcined kaolin was only about 700,000 tons. In terms of import and export, China's kaolin export volume has been maintained above 400,000 tons before 1999, and reached 879,900 tons in 1997. However, after 1999, due to the central government's requirement to control excessive mining, the export volume has decreased year by year since 2000. At the same time, kaolin imports are rising year by year. It is worth mentioning that our export of kaolin is mainly low-value original minerals, and most of the imported products are high-value-added products after deep processing, and the import volume has exceeded the domestic similar products, indicating that there is a large gap in the demand for such products in China, and the domestic supply of high-quality products can not meet the market demand. This also shows that the market of calcined kaolin products still has great growth potential. The calcined kaolin used in coatings needs high whiteness, low viscosity and fine particle size, but the domestic products are rough and cannot meet the quality requirements. As for kaolin industry, it also faces the same problem as many domestic industries, that is, "big but not strong". Kaolin industry also needs to constantly upgrade itself to meet the increasing market demand, in order to withstand the tests from the market in many ways.

Paint with kaolin future market development optimistic forward

The impact of calcium carbonate, titanium dioxide and other related products on kaolin is one of the tests. In the mid-1980s, with the improvement of papermaking process, calcium carbonate began to increase its market share in papermaking filler and coating, posing a major threat to the kaolin industry. Heavy calcium rheology is good, light calcium opacity and high whiteness, a large number of paper filling, coating. Major factories in Europe and North America have improved the process, using CaCO3 as pigment. According to the analysis, in 1990, the proportion of calcium carbonate and kaolin in paper pigments respectively accounted for 45%, but by the middle of 2005, kaolin will drop to 30%-35%, and calcium carbonate will rise to 60%. However, due to the advantage of the flake structure of kaolin can ensure the smoothness of paper, printing gloss and other important quality indicators, light calcium can not completely replace kaolin in coatings. In the past, the view that kaolin, as a basic additive, is merely an extension of titanium dioxide, is clearly outdated today. The contribution of kaolin to the preparation of low VOC, high solid coatings, thinner and faultless smooth, bright coatings and other requirements of the current coating industry is constantly emerging.

At the same time, the consumption of Kaolin in various fields in China will be strong. In terms of the coating industry, the annual coating output in 2010 was 9.666 million tons, and the cumulative output from January to July in 2011 was about 5.791 million tons, with a cumulative growth rate of 18.91%. Although the growth rate slowed down in June and July this year, overall growth is still maintained. "Coating industry" twelfth Five-year plan "pointed out that benefited from industrial and civil demand pull, coating output is expected to maintain an average annual growth rate of 10%, coating output is expected to reach 12 million tons in 2015. The growth situation of coating industry will undoubtedly drive the sweat of the upstream industry including kaolin. With the continuous development of the market, the consumption of kaolin also grows faster, it is expected that the future Chinese coating needs kaolin will have a greater growth, its future development will be optimistic forward.