What are the specific requirements of titanium dioxide for ink

Influence on the whiteness of oil ink

The influence of impurities in titanium dioxide on the whiteness of oil ink：

Inks made of titanium dioxide with good whiteness are durable and non-yellowing, and can keep the color of printed products bright and vivid in various environments. In general, if there are trace amounts of iron, chromium, cobalt, copper and other impurities mixed into titanium dioxide, the prepared ink will produce color bias, whiteness is reduced. This is caused by impurity ions in titanium dioxide, especially metal ions, which distort the crystal structure of titanium dioxide and lose its symmetry.

Rutile titanium dioxide is more sensitive to impurities, such as iron oxide in rutile titanium dioxide content is greater than 0.003% will show color, and its content in anatase titanium dioxide is greater than 0.009% will produce color reaction. Therefore, it is very important to choose fine and impurity free titanium dioxide.

The influence of the shape, size and distribution of titanium dioxide particles on whiteness：

High-quality titanium dioxide particles have smooth appearance and no edges. If the titanium dioxide with edges on the surface of the particles is used, the reflection of light will be greatly weakened and the whiteness of the ink will be reduced.

The size of titanium dioxide particles should be controlled at 0.2~0.4μm, which is equivalent to about 1/2 of the wavelength of visible light, in order to obtain high scattering ability, so that its color appears whiter. When the particle size is less than 0.1μm, the crystal is transparent, if the particle size is more than 0.5μm, it will reduce the scattering ability of the pigment to light, affecting the whiteness of the ink.

For this reason, the particle size of titanium dioxide is required to be appropriate and evenly distributed to show good whiteness. Practice has proved that rutile titanium dioxide has better covering power than anatase titanium dioxide, so it is more widely used in ink production.

The influence of ink covering power

The level of the titanium dioxide crystal’s own refractive index will directly affect the size of the ink covering power：

In the printing process of gravure composite film ink, in order to make the printed matter get a bright color and beautiful effect, white ink must be used as the base, and then color printing is carried out. This requires titanium dioxide to have good coloring power and hiding power, otherwise the effect will be poor. In general, the refractive index of titanium dioxide is the best in white pigments, and titanium dioxide with high refractive index should be selected when preparing white ink to enhance the hiding power of white ink.

The effect of particle size, particle structure and dispersion of titanium dioxide on the covering power of white ink：

Generally, in the range of more than 1/2 of the visible light wavelength, the smaller the particle size, the smoother the particle surface, the better the dispersion of titanium dioxide in the resin binder, and the stronger its hiding power. Because titanium dioxide itself has an obvious crystal structure, its refractive index is larger than that of the spreading agent, and the greater the difference in refractive index between the two, the stronger the hiding power of titanium dioxide used.

The impact on the dispersion of titanium dioxide particle shape and light reflection is uniform, directly affect the dispersion of titanium dioxide. If the surface of titanium dioxide particles is smooth and uniform, its dispersion is good, and the prepared white ink gloss and whiteness are also good; On the contrary, the particle surface is rough, the diffuse reflection increases, it will greatly reduce the gloss, and the dispersion is poor, which directly affects the whiteness and transfer performance of the white ink. For this reason, titanium dioxide must be treated before it can be used.

In addition, there are the following factors affecting the ink:

Good light and weather resistance: If the printed matter is placed outdoors for a long time, it is necessary to ensure that the titanium dioxide has good light and weather resistance, otherwise the ink will turn yellow and powder.

Good heat resistance: for baking iron printing inks, the baking temperature of the printing process reaches about 180° and the time is up to 2 hours. Such printing conditions require that the titanium dioxide in the ink has excellent heat resistance, otherwise the white ink will turn yellow at high temperatures, lose luster, and even make the print scrap.

Oil absorption: With the improvement of printing speed and technology, it is necessary to reduce the viscosity of the ink, and the oil absorption of titanium dioxide has become the key. In the case of constant color concentration, reduce the oil absorption as much as possible, which is conducive to improving the preparation of viscosity ink.