Coatings are mainly composed of four parts: film-forming substances, pigments, solvents and additives. The pigment in the paint has a certain hiding power. It can not only cover the original color of the coated object, but also give the coating film a bright color and achieve a bright and beautified decorative effect. At the same time, the pigment is tightly combined with the curing agent and the substrate, and integrated, can enhance the mechanical strength and adhesion of the coating film, prevent cracking or peeling, and can increase the thickness of the coating film, prevent the penetration of ultraviolet rays or moisture, and improve the coating. The anti-aging and durability properties of the film extend the service life of the coating film and the object to be protected.
In the pigment, the amount of white pigment is very large, and the performance requirements of the coating for white pigment: ①good whiteness; ②good grinding and wettability; ③good weather resistance; ④good chemical stability; ⑤small particle size, high covering power and lightening power, good opacity and gloss.
Titanium white powder is a kind of white pigment used in coatings. Its output accounts for more than 70% of inorganic pigments, and its consumption accounts for 95.5% of the total consumption of white pigments. At present, about 60% of the world’s titanium white powder is used in the manufacture of various coatings, especially rutile titanium dioxide, most of which are consumed by the coating industry.
TiO2 coating has bright colors, high hiding power, strong coloring power, low dosage, and many varieties. It protects the stability of the medium, and can enhance the mechanical strength and adhesion of the paint film, prevent cracks, and prevent ultraviolet rays and moisture from penetrating. To prolong the life of the paint film, the color matching of almost every pattern in the colorful pattern paint is inseparable from titanium dioxide.
Different types of titanium dioxide coatings for different purposes have different requirements for titanium dioxide. For example, powder coatings require the use of rutile titanium dioxide with good dispersibility. Anatase titanium dioxide has low decoloring power and strong photochemical activity. When used in powder coatings, the coating film is prone to yellowing. The rutile titanium dioxide produced by the sulfuric acid method has the advantages of moderate price, good dispersibility, good hiding power and color reducing power, and is very suitable for indoor powder coatings. In addition to good dispersibility, hiding power and lightening power, titanium dioxide for outdoor powder coatings also requires good weather resistance. Therefore, outdoor titanium dioxide coatings are generally rutile titanium dioxide produced by the chlorination method.