Titanium dioxide inorganic coating technology to enhance the role of

(1) Titanium dioxide coated with alumina

Titanium dioxide surface coating alumina is one of the common means to enhance the dispersion stability of titanium dioxide aqueous system in the industry. Among them, the microstructure of alumina coating layer on the surface of titanium dioxide has a direct impact on the surface properties such as hydroxyl density on the surface of the particles, surface free energy, surface potential, spatial resistance, etc., which in turn affects the dispersion stability of titanium dioxide in the aqueous system, and the microstructure of the alumina coating layer can be regulated and optimized through the control of the coating process factors.

(2) Zirconium dioxide coated titanium dioxide

Titanium dioxide has a certain photocatalytic activity, can absorb ultraviolet light to produce active groups, resulting in degradation of the surrounding organic media, reducing the service life of the product. Zirconium dioxide has a high refractive index (2.170), and the absorption of ultraviolet light is extremely weak. Therefore, continuous dense zirconium dioxide coating on the surface of titanium dioxide particles can not only reduce the absorption of ultraviolet light, but also impede the direct contact between the active groups and the surrounding media and the external environment, to enhance the light-resistant properties of titanium dioxide.

(3) Silica-coated titanium dioxide

Silica coating on the surface of titanium dioxide can hinder its direct contact with the surrounding medium and the external environment, to enhance the weathering performance of titanium dioxide. The microstructure of the silica coating layer on the surface of titanium dioxide directly determines the area of titanium dioxide particles exposed to the external environment or surrounding media, which in turn affects its weathering performance.

(4) Aluminum phosphate coated titanium dioxide

Titanium dioxide in papermaking, exterior coatings and other industrial applications need to have both high light resistance and excellent dispersion stability. At this stage, the main inorganic - organic composite coating of titanium dioxide to achieve practical application requirements. The development of a single inorganic coating can simultaneously meet the requirements of light resistance and dispersion stability of the product, can significantly reduce the cost of late organic coating. Aluminum-based materials as a better electron acceptor, can annihilate the photogenerated electrons generated by titanium dioxide absorption of ultraviolet light excitation, inhibit the generation of reactive groups, and improve the light resistance; and the introduction of phosphoric acid can regulate the surface potential of titanium dioxide particles, improve the dispersion stability. Therefore, coating aluminum phosphate on the surface of titanium dioxide can simultaneously improve the light resistance and dispersion stability of titanium dioxide.

The main role of the organic coating agent is to improve the properties of titanium dioxide in organic matter, the principle of its action is to change the characteristics of the surface of titanium dioxide, such as dispersion.

Titanium dioxide particles and organic film connection between the two main ways, one is chemical adsorption, is through the titanium dioxide particles on the surface of the hydroxyl group and the organic film coating agent reaction, so as to connect. The other is physical adsorption, organic coating agent in the physical form of the characteristics of the surface adsorption, the molecule consists of two parts, respectively, lipophilic and hydrophilic.

When the coating agent and titanium dioxide physical contact, titanium dioxide surface particles will adsorb the polar group, while the non-polar bond is exposed, thus forming a protective film. The titanium dioxide particles in this case present a free state, and in this state, the particles will be very easy to separate from each other, thus achieving the separation effect.

Organic surface modifier is mainly a variety of surfactants, and the molecule is composed of polar hydroxyl and non-polar hydroxyl two parts, when the titanium dioxide and modifier chemical reaction, titanium dioxide's properties will change very much, that is, the hydrophilicity will be converted to lipophilic.

There is another class of surfactants, such as sodium alkylbenzoate, which can ionize a large number of negatively charged ions in aqueous solution, making the double electric layer of titanium dioxide particles in aqueous solution thicker, thus improving the dispersion performance of titanium dioxide in aqueous media.