There are many factors influencing the whiteness of titanium dioxide, including the influence of mineral sources, as well as the influence of equipment and key technologies. Through experiments and field experience, the main factors affecting its whiteness are: hydrolysis quality, removal of impurity elements and calcination conditions.
The hydrolysis technology of titanium dioxide currently has two technologies: pressure hydrolysis and normal pressure hydrolysis. Based on the analysis of the hydrolysis quality and product quality, the normal pressure hydrolysis quality is better and the hydrolysis particle size is uniform. To ensure the quality of hydrolysis, the quality index of concentrated titanium liquid must be strictly controlled, the ratio of iron to titanium and solid content should be controlled within the specified range, and the control of the operating conditions of the hydrolysis process should be increased.
Another major factor that affects the whiteness of titanium dioxide is some impurities and colored elements, such as iron, cobalt, nickel, etc., certain measures must be taken to remove it. For anatase titanium dioxide, when the high iron content is 120ppm, the whiteness is affected , Even the phenomenon of light and color change. Using bleaching technology, increase the washing power of high-speed iron, and add some masking agents, such as antimony trioxide and phosphoric acid, to complex and mask the iron and reduce the influence of impurity elements on the whiteness of titanium dioxide.
- 1.Control of calcination conditions is an important part of the nucleation of titanium dioxide crystals. A good calcination temperature can completely desulfurize and dehydrate titanium dioxide, and try to avoid the lattice defects of titanium dioxide crystal nucleus and affect its whiteness. Therefore, increase the control of key temperature points, at the same time make the feed volume and the kiln body speed reasonable match, increase the combustion chamber, to avoid contact with the material and flame, sintering.
- 2. Ways to stabilize the particle size distribution of titanium dioxide and improve the dispersion and hiding power of titanium dioxide
Titanium dioxide particle size distribution is a comprehensive index, which seriously affects the performance of titanium dioxide pigment and product application performance. Therefore, the discussion of hiding power and dispersibility can be directly analyzed from the particle size distribution.
The factors that affect the particle size distribution of titanium dioxide are more complicated. The first is the size of the original particle size of hydrolysis. By controlling and adjusting the hydrolysis process conditions, the original particle size is within a certain range. The second is the calcination temperature. During the calcination of metatitanic acid, the particles undergo a crystal transformation period and growth period. The appropriate temperature is controlled so that the growing particles are within a certain range. Finally, the product is crushed. The modification of the Raymond mill and the adjustment of the analyzer speed are usually used to control the quality of the crushing. At the same time, other crushing equipment can be used, such as: universal mill, air jet mill and hammer mill device.
- 3. Through surface treatment, improve the application performance of titanium dioxide
Titanium dioxide is a very polar powder, which is hydrophilic and oil-repellent, but if air, water and other contaminants are adsorbed on the surface, the dispersibility in water decreases, and it is often necessary to perform surface treatment on it. The agent is hydrated alumina and hydrated silica. At present, there are many surface treatment agents on the market, such as: silicone, coupling agent, etc., or add some other inorganic pigments such as: barium sulfate, aluminum hydroxide, etc. to improve the surface characteristics of titanium dioxide, and improve its dispersion.