Surface Treatment of Titanium Dioxide in Foreign Countries
The production of titanium dioxide abroad began in 1916, and the development of production was affected by the purification of impurities such as Fe3+ and the uncontrollable particle size of the pigment. It was not until 1930 that anatase pigment titanium dioxide was produced. Since then, due to the discovery that titanium dioxide produces photochemical activity when used in paint, there is the same problem of accelerating the pulverization of film-forming materials, so inorganic oxides such as A12O3 and SiO2 are gradually used for surface treatment. Due to the development of surface treatment technology, the quality of titanium dioxide has been continuously improved, and there are hundreds of varieties. To sum up, the surface treatment and varieties of titanium dioxide are classified as follows:
1. Universal titanium dioxide
The output of universal titanium dioxide exceeds 60% of the total output of titanium dioxide. The surface treatment of these products is generally carried out with inorganic oxides such as AI 203, AI 20 3-SiO2 or A1 2O 3-SiO2-TiO2, which account for 2% to 5% of the total amount. Through the analysis of surface-treated general-purpose titanium dioxide products, it is found that the content of T iO2 is about 94%, and the amount of treatment agent is about 3% to 5%.
2. High weather resistance titanium dioxide
Shows excellent performance in weather resistance, which is especially required for coatings for outdoor use. The surface treatment agents used in such products are still inorganic oxides such as A12O3, SiO2, TiO2, ZrO2, and the addition amount is 7% to 10%. During the coating process, these oxides are deposited on the surface of TiO2 particles to form a skin-like dense film, which plays a good protective role against the natural oxidation-reduction process of the TiO2 surface.
3. Coating titanium dioxide with high pigment volume concentration
The titanium dioxide pigment used for flat latex paint should have a spongy coating after treatment, and the amount of treatment agent added is 10% to 15%. In order to make the hydrophilic performance of titanium dioxide better, the treatment amount of SiO2 is generally much higher than that of Al203. After the titanium dioxide coated with a large amount of porous Al2O3-SiO2 or aluminum silicate is crushed into a suitable particle size, the maximum coverage rate can be obtained in the latex paint.
4. Titanium dioxide treated with organic matter
Some varieties should be surface treated according to the special requirements of use. For example, treatment with a small amount of organic compounds can improve the dispersibility of titanium dioxide. Commonly used organic compounds are polyols, polyamines and silicone oils. When choosing an organic treatment agent, pay attention to its heat resistance, stability, and place of use.
The surface treatment of foreign titanium dioxide, in addition to attaching importance to treatment technology, also requires very strict surface treatment agents. Because of the precipitation of any colored impurities, it will affect the whiteness of titanium dioxide. Generally, the Fe3+ content in foreign titanium dioxide is mostly below 40PPm, and the purity of the surface treatment agent is very important.
