Titanium dioxide is polycrystalline compound, its molecular formula is TiO2. It has high whiteness, small particles. Its particle size is 0.1-0.7μm, refractive index is 2.72, and oil absorption is 45%-48%. Besides, it has a strong coloring power and optical diffusion. When titanium dioxide separates in the medium, the covering power of ink can be enhanced to 45-75g/m2. In addition, titanium also has good light resistance, heat resistance, alkali resistance, weather resistance and water-repellent. Therefore, the application of high quality titanium dioxide has the most excellent effect in white ink and it's one of the most indispensable materials in ink and Melamine Paper industry.
The types and requirements of titanium dioxide
Type: there are three kinds of crystalline pattern titanium dioxide in the nature--- rutile pattern, anatase pattern and brookite pattern. Because brookite pattern is very unstable, the types suitable for ink production are only rutile pattern and anatase pattern. Both of them have stable physical and chemical properties; small particles; high refractive index and the colors are pure white.
Technical requirements: in the production of ink, different types of ink have different requirements on titanium dioxide quality. Practice has proved that rutile pattern titanium dioxide have an ideal application performance, which can be widely used in preparation of various ink types.
Offset print uses exclusion principle of oil and water. Therefore, the resin binders used in offset print ink should have good anti-emulsifying and excellent water repellency. In addition, the presswork which is placed in outdoor for a long time, offset print white ink’s preparation---titanium dioxide must have good light resistance and weather resistance. Otherwise white ink will turn yellow or be pulverized.
For the gravure composite film inks, in order to make printing colorful and beautiful, industries would use white ink primer to under-paint and then print color. Therefore, titanium dioxide must have excellent tinting strength and covering power.
For the Thermal Post Cure metal decorating white ink, its temperature is about 180 â„ƒ after baking, and the baking time up to 120 minutes. Therefore, titanium dioxide must have excellent heat resistance or it will turn yellow and full in the high-temperature baking and even can be declared worthless.
The requirements of titanium dioxide quality in printing ink are as following: good whiteness, durable and non-yellowing, can make the color in a variety of environment to maintain bright color; good wettability, easy to grind; small particles, easy to separate in the vehicle of printing ink; strong covering power, good tinting strength; good weather resistance and heat resistance, chemical performance is stable; good anti-waterborne.