Titanium Dioxide is currently the world's best performing white pigment, widely used in industrial fields such as coatings, inks, papermaking, plastics, and rubber. Ink is a viscous adhesive fluid made by uniformly mixing its components and repeatedly rolling them. It is one of the important materials used for packaging material printing, presenting patterns, text, and other materials on the substrate through printing.
1： The application of titanium dioxide in different inks
1. Offset printing ink. In the printing process of offset ink, the printing process is usually completed based on the principle of "oil water repulsion" during offset printing. Therefore, offset printing ink titanium dioxide needs to have good anti emulsification and hydrophobicity. If printed materials are left outdoors for a long time, titanium dioxide also needs to have good light resistance and weather resistance, otherwise the ink will turn yellow and powdery.
2. Gravure composite film ink. In the process of gravure composite film ink printing, in order to achieve a bright and beautiful color effect, white ink must be used as a base before color printing. This requires titanium dioxide to have good coloring and covering power, otherwise the effect will be poor.
3. Baking type printed iron ink. For this ink, the baking temperature reaches around 180 ° C. The baking time should reach about 2 hours. Such printing conditions give the titanium dioxide in the ink excellent heat resistance, otherwise the white ink will turn yellow, lose its luster, and even scrap the printed material at high temperatures.
2： The influence of titanium dioxide on ink
In ink production, different types of ink products have different quality requirements for titanium dioxide powder. Rutile type titanium dioxide is generally used in ink production.
1. Oil absorption capacity. With the improvement of printing speed and technology, it is necessary to reduce the viscosity of ink, and the oil absorption of titanium dioxide powder becomes the key. Reducing the oil absorption as much as possible while maintaining the same color concentration is beneficial for improving the viscosity of ink preparation.
2. Particle size and distribution. High quality titanium dioxide particles have a smooth appearance, no edges, and the size and shape of the titanium dioxide particles are evenly distributed, which greatly affects the whiteness of titanium dioxide. The particle size of titanium dioxide is between 0.2 and 0.4um, which is equivalent to about half of the visible wavelength, and can achieve high scattering ability, making the color appear whiter.
3. Scattering ability and refractive index. The higher the refractive index of titanium dioxide, the stronger the coloring power, the larger the scattering coefficient, and the stronger the coloring power. Due to its distinct crystal structure, titanium dioxide has a higher refractive index and better coverage than colorants, making it widely used in inks.
3： Characteristics requirements of titanium dioxide for ink production
1. To follow the principle of low viscosity and high concentration ink
At present, domestic printing equipment is becoming more and more advanced, and many of them are synchronized with the international advanced level. After the advanced machines, the printing speed is doubled, and the higher the printing speed, the lower the viscosity adjustment of the ink. Low viscosity and high concentration ink are suitable for this development requirement. The viscosity of white ink is not only adjusted by the main Resin and additives, but also by the oil absorption of titanium dioxide powder. Try to reduce the oil absorption as much as possible while maintaining the same color concentration, which is beneficial for the preparation of high concentration and low viscosity inks. At present, some targeted products abroad have an oil absorption capacity of less than 15, while the domestic related titanium dioxide powder is about 20, and the gap is still quite large.
2. Grinding of titanium dioxide powder
The fineness of ink depends on the medium for pigments, and different grinding methods will have different color development effects on titanium dioxide. Currently, some titanium dioxide produced by domestic enterprises are suitable for high-strength grinding, while others are suitable for slow grinding. Due to the confidentiality of manufacturers, especially sales personnel who do not understand or do not understand, it leads to manufacturers not knowing different products, which brings trouble to downstream customers in the ink process. This is also the reason why some domestic ink companies have different evaluations of domestic titanium dioxide. In contrast, foreign companies have done very well, with most of the specialized ink types being general-purpose grinding.
3. Precipitation of white ink
This kind of problem is common in ink companies. After long-term storage, ink will have titanium dioxide precipitate at the bottom of the packaging barrel, and often these precipitates are not only titanium dioxide, but also some adsorbents of titanium dioxide, which are often functional additives. So, the white precipitate not only reduces the color concentration of the ink, but also affects the balance of system components, leading to a decrease in quality. In contrast, currently, foreign titanium dioxide specific ink types have solved the suspension effect of titanium dioxide particles in different systems, which means improving the encapsulation force of titanium dioxide particles in different resin systems. This will greatly affect the balance of the system and will not cause sedimentation of the ink.
4. The color spreading properties of titanium dioxide
The color development of titanium dioxide is closely related to the resin system of related enterprises. Some titanium dioxide powders exhibit good whiteness and covering power in one resin system, while the other system immediately presents a problem table. So, from a certain perspective, the performance of titanium dioxide cannot be determined solely based on its good or bad performance, but rather whether it is suitable or not for this ink system. Of course, so far there is no titanium dioxide that can adapt to all systems. So foreign manufacturers have targeted applications for ink, and even two or more specialized models of titanium dioxide, which is very worth learning from for domestic titanium dioxide manufacturers.
5. Weathering resistance of titanium dioxide
Usually, the vast majority of ink companies require the particle shape of the titanium dioxide they use to have a smooth contour and no sharp edges. Due to the use of titanium dioxide particles with sharp edges on the surface, the surface of the particles will greatly weaken the reflection of light, resulting in a decrease in whiteness. The domestic ink companies I have come into contact with require titanium dioxide particles to be between 0.2 and 0.4um, which is equivalent to half of the visible light wavelength range, in order to achieve high light scattering ability and make its color appear whiter. When the particle size is less than 0.1um, the crystal is transparent; If the particle size is too large, greater than 0.5um, it will reduce the pigment's ability to scatter light and affect its whiteness. For its titanium dioxide particles, it is required to have a uniform distribution and a narrow distribution to display the good whiteness of the ink.
