Influencing factors and improving methods of dispersion of titanium dioxide in coatings

Titanium dioxide is a coating material, it can not only make the surface of the coated object bright and white, but also enhance the weatherability, resistance to powder and rheology of the coating. The dispersion of titanium dioxide is very important in the paint, and its advantages and disadvantages will directly affect the production process, production equipment and product quality of the paint. Understanding the dispersion factors of titanium dioxide in coatings can not only improve the quality of coatings, but also reduce pollution emissions, so that the national clean industry requirements can be better implemented.

1. Factors affecting dispersionIn solvent-based coatings, when the resin and solvent oil are determined, the application performance and performance characteristics of titanium dioxide determine its dispersion and dispersion stability.

First, the average particle size and particle size distribution affect the properties of titanium dioxide pigments. When the mass percentage of titanium dioxide particle size less than 200nm is about 30%, the Zeta potential is about -70mv; If the mass percentage is less than 20%, the Zeta potential is about -40mv, it can be seen that the particle size of titanium dioxide seriously affects its surface electrical properties, thus affecting the surface adsorption performance. It should be noted that the particle size can not be too small, otherwise it will affect the other properties of titanium dioxide, and it is best to control the particle size in (0115 ~ 013)Lm.

Secondly, the content of soluble substances affects the application performance of titanium dioxide. In the mixed coating dispersion system, the highly polar inorganic ions will both offset the charge on the surface of titanium dioxide, and can not form a strong double electric layer, so that the adsorption effect of the surface of titanium dioxide is weak, so that the resin can not be firmly adsorbed on the surface of titanium dioxide particles, thereby reducing the degree of titanium dioxide dispersion and stabilization, resulting in its return to coarse in the solvent based coating.

Thirdly, the level of oil absorption affects the dispersion or dispersion stability of titanium dioxide. After the grinding and dispersing of titanium dioxide with high oil absorption, part of the solvent oil will be absorbed by titanium dioxide, so that the oil of the dissolved resin is insufficient, the degree of resin solvation is reduced, and the absorption of titanium dioxide is weakened, resulting in the reduction of its dispersion and dispersion stability.

2. Ways to improve dispersion

First, strictly control particle size and particle size distribution. The factors affecting the particle size and particle size distribution of titanium dioxide are more complex, and it is more difficult to fully grasp, so the hydrolysis process and technology can be improved first to ensure that the generated primary particles are uniform. Secondly, the control of the key temperature point of calcination can be strengthened to make the titanium dioxide particles grow evenly. Finally, the product is pulverized, and the Raymond system can be replaced by the airflow crusher with high efficiency and good classification effect to stabilize the surface characteristics of titanium dioxide.

Second, strictly control the amount of oil absorption and water soluble matter. The amount of titanium dioxide oil absorption is mainly related to the calcination atmosphere or the calcination high temperature point temperature during the calcination process, if not properly controlled, it will cause the lattice defects of titanium dioxide particles and the irregular shape of particles, therefore, it is necessary to control the appropriate calcination temperature, adjust the reasonable match of the feed amount and the kiln body speed, and reduce the lattice defects of particles and the geometric shape of the particles.Third, strictly do a good job of surface treatment.

At present, most of the domestic manufacturers are anatase titanium dioxide, its dispersion in the paint is poor, in the context of the national promotion of clean industry, its application in the paint industry is gradually replaced by rutile titanium dioxide. For the coating enterprises that are still using anatase titanium dioxide, the surface characteristics can be changed by surface treatment, such as the selection of silicone, coupled nitrogen reagents or some polyphosphates.

Dispersion is an important indicator that titanium dioxide manufacturers are most concerned about, poor dispersion, not only the efficacy of titanium dioxide will be greatly reduced, pollution will also be intensified. With the rapid development of China’s economy and policies, especially the increasing improvement of environmental protection policies, industries related to titanium dioxide, especially the coating manufacturing industry, are developing with each passing day, which has brought unprecedented opportunities and challenges to China’s titanium dioxide manufacturing industry. Therefore, titanium dioxide enterprises should carefully study product performance, timely improve the production process, consolidate the foundation, let the national policy change from resistance to thrust, to achieve the stable take-off of enterprises.

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