1. The main way to improve and stabilize the whiteness of titanium dioxide powder
There are many factors that affect the whiteness of titanium dioxide, including the influence of mineral sources, equipment, and key technologies. Through experiments and field experience, the main factors affecting its whiteness are: hydrolysis quality, removal of impurities and calcination conditions.
The hydrolysis technology of titanium dioxide powder currently has two types in China: pressurized hydrolysis and atmospheric hydrolysis. From the perspective of hydrolysis quality and product quality, the atmospheric hydrolysis quality is good and the hydrolysis particle size is uniform. To ensure the quality of hydrolysis, it is necessary to strictly control the quality indicators of concentrated titanium solution, control the iron titanium ratio and solid content within the specified range, and increase the control of hydrolysis process operating conditions.
Another main factor affecting the whiteness of titanium dioxide is the presence of impurities such as colored elements such as iron, cobalt, nickel, etc., which must be removed by certain measures. For anatase titanium dioxide, when the high iron content is 120ppm, its whiteness is affected, and even photochromic reciprocity occurs. Bleaching technology is used to increase the washing strength of high iron, and some masking agents are added at the same time, such as Antimony trioxide and phosphoric acid, to complexly mask iron and reduce the influence of impurities on the whiteness of titanium dioxide. The control of calcination conditions is an important step in shaping the crystal nucleus of titanium dioxide powder. A good calcination temperature can enable complete desulfurization and dehydration of titanium dioxide powder, and try to avoid lattice defects in the crystal nucleus of titanium dioxide powder that affect its whiteness. Therefore, increase the control of key temperature points, while ensuring a reasonable match between the feed volume and kiln speed, increase the combustion chamber, and avoid material and flame contact, leading to sintering.
2. Ways to stabilize the particle size distribution of titanium dioxide and improve its dispersivity and hiding power
The particle size distribution of titanium dioxide 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 affecting the particle size distribution of titanium dioxide powder are complex. First, the size of the original particle size of hydrolysis is controlled and adjusted to make the original particle size within a certain range. Next is the calcination temperature. During the calcination process of metatitanic acid, the particles undergo a phase transition and growth period. Control the appropriate temperature to keep the growing particles within a certain range. Finally, the crushing of the product is usually achieved by modifying the Raymond mill and adjusting the analyzer speed to control the crushing quality. Other crushing equipment can also be used, such as universal mills, airflow crushers, and hammer grinding devices.
3. Improving the application performance of titanium dioxide powder through surface treatment
Titanium dioxide is a highly polar powder that is hydrophilic and oil repellent in nature. However, if air, water, and other pollutants are adsorbed on the surface, its dispersibility in water decreases, and surface treatment is often required. The commonly used treatment agents are hydrated alumina and hydrated silica. At present, there are many surface treatment agents on the market, such as organic silicon, coupling agent, etc., or some other inorganic pigments, such as Barium sulfate, Aluminium hydroxide, etc., to improve the surface characteristics of titanium dioxide and improve its dispersion.