Improvement of Water Dispersibility of Titanium Dioxide
Titanium dioxide has been used more and more extensively in emulsion paints, paper, cosmetics and chemical fibres for whitening, matting, sun protection and improving opacity due to its excellent hiding power, whiteness, light reflectivity and light refractivity. As these applications are all water-based, the titanium dioxide used must have very good water dispersibility.
By aqueous dispersion we mean that the titanium dioxide is evenly suspended in the aqueous system and does not float on the surface of the water nor does it sink to the bottom. In other words, the surface of the titanium dioxide has to be in a critical state where it is neither hydrophilic nor hydrophobic.
Without surface treatment or only after conventional coating treatment, the surface of titanium dioxide is generally hydrophobic or hydrophobic, and the water dispersion is very poor. When titanium dioxide is added to an aqueous system, it either sinks to the bottom or floats on the water surface very quickly, even if it is strongly stirred with mechanical external force, it will sink to the bottom or float on the water surface again within 0.5-1 hour. In other words, titanium dioxide cannot be stably dispersed in aqueous systems. In the specific process of use, due to the poor dispersion of titanium dioxide pigments, they tend to delaminate with resins or dispersion carriers (e.g. water), resulting in failure to produce or use properly. Therefore, for titanium dioxide used in aqueous systems, special organic surface treatments must be applied to improve their water dispersibility.
In general, the main surface treatment agents used to improve the water dispersibility of titanium dioxide are low carbon polyhydroxy alcohols, long carbon chain unit alcohols, long carbon chain unit acids, low carbon polyhydroxy acids, fatty acid salts, organic amines, lipids, non-ionic surfactants, etc. With these materials, after a suitable treatment process, a relatively good water dispersion can also be obtained. However, such surface treatment agents have some disadvantages to varying degrees.
In the case of water dispersible titanium dioxide surface treatment agents, the main raw material used is polymeric active silicone, which does not contain any harmful solvents and does not release any harmful gases or electrolytes during use. This water-dispersible surface treatment does not cause an increase in the conductivity of the titanium dioxide production or use system, but at the same time can also significantly improve the whiteness of the titanium dioxide, colour extinction and weather resistance and other pigment indicators.
