Application of titanium dioxide in ink industry

Application of titanium dioxide in the ink industry

titanium dioxide is a polycrystalline compound with molecular formula of TiO2, high whiteness, fine particles, and particle size of 0.1 ~ 0.7 μ m. The refractive index is 2.72, the oil absorption is 45% - 48%, and it has strong coloring power and light diffusion. When titanium dioxide is dispersed in the medium, the hiding power of the ink can be enhanced to 45 ~ 75g/m2. In addition, titanium dioxide also has good light resistance, heat resistance, alkali resistance, weather resistance and hydrophobicity (hydrophobicity). Therefore, it is particularly effective in high-quality white ink. It is one of the indispensable raw materials in the ink industry at present

type and requirements of titanium dioxide for ink

1 There are three kinds of crystalline titanium dioxide in nature, namely rutile, anatase and plate titanium. Because the crystal form of titanium dioxide is extremely unstable, there are only two kinds of titanium dioxide suitable for ink production: rutile and anatase, both of which are tetragonal. They have stable physical and chemical properties, pure white color, fine particles and high refractive index

2. Technical requirements in ink production, different types of ink products have different quality requirements for titanium dioxide. Practice has proved that rutile titanium dioxide has ideal application performance and can be widely used in the preparation of various types of inks. Table 1 shows the comparison of the performance indexes of two kinds of titanium dioxide

it is not difficult to see from the table that rutile titanium dioxide is superior to anatase titanium dioxide in terms of crystal shape, refractive index, coloring power and fluorescence index. Therefore, rutile titanium dioxide is widely used in ink production. In addition, titanium dioxide with different properties should be selected according to the specific characteristics and requirements of various inks in the process of ink preparation

(1) offset printing is based on the principle that oil and water repel each other. Therefore, the resin binder used in offset printing ink should not only have good demulsibility, but also have excellent hydrophobicity. Otherwise, offset white ink is easy to emulsify; In addition, the offset white ink used for long-term outdoor printing requires that the titanium dioxide used for its preparation must have good light resistance and weather resistance, otherwise the white ink will turn yellow or chalky

(2) for gravure composite film inks, in order to make the prints colorful and beautiful, white ink is used for backing first, and then color printing is carried out. Therefore, titanium dioxide must have excellent coloring power and hiding power

(3) for baking iron printing white ink, the post printing baking temperature is about 180 ℃, and the baking time is about 120 minutes

therefore, the titanium dioxide in the iron printing white ink must have excellent heat resistance, otherwise, the white ink will turn yellow and lose luster during high-temperature baking, and even cause the scrap of printing products in serious cases

therefore, according to the requirements of different types of inks and different printability, the reasonable selection of titanium dioxide is the key to manufacturing excellent white inks. The quality requirements of titanium dioxide for comprehensive ink mainly include the following points:

① good whiteness, durability and no yellowing, which can keep the color of prints bright and bright in various environments

② good wettability and easy grinding

③ the particles are small and easy to be evenly dispersed in the ink binder

④ strong covering power and good coloring power

⑤ good weather resistance, heat resistance and stable chemical properties

⑥ good water resistance

the influence of titanium dioxide quality on inks

titanium dioxide is relatively large in the manufacture of various types of inks, ranging from 25% to 50%, and some even greater. Therefore, titanium dioxide plays a vital role in the quality of ink

1. Influence on the whiteness of ink (1) the influence of impurities in titanium dioxide on the whiteness of ink. Generally speaking, if a trace of iron, chromium, cobalt, copper and other impurities are mixed into titanium dioxide, the prepared ink will produce color deviation and reduce whiteness. This is caused by the distortion and loss of symmetry of the crystal structure of titanium dioxide caused by impurity ions, especially metal ions in titanium dioxide. Rutile titanium dioxide is more sensitive to impurities. For example, when the content of iron oxide in rutile titanium dioxide is greater than 0.003%, it will show color, while when the content of iron oxide in anatase titanium dioxide is greater than 0.009%, it will produce color reaction. Therefore, it is very important to choose fine and impurity free titanium dioxide

(2) the influence of the shape, size and distribution of titanium dioxide particles on whiteness. High quality titanium dioxide particles have smooth shape and no edges and corners. If titanium dioxide with edges and corners 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 within 0.2 ~ 0.4 μ m. That is, it is equivalent to about 1/2 of the wavelength of visible light to obtain high scattering ability and make its color appear whiter. When the particle size is less than 0.1 μ M, the crystal is transparent, if the particle size exceeds 0.5 μ m. It will reduce the scattering ability of the pigment to light and affect the whiteness of the ink. Therefore, the particle size of titanium dioxide is required to be appropriate and evenly distributed to show good whiteness

2. Influence on ink coverage (1) the refractive index of titanium dioxide crystal will directly affect the ink coverage. Generally, the refractive index of titanium dioxide is the best among white pigments. When preparing white ink, titanium dioxide with high refractive index should be selected to enhance the hiding power of white ink

(2) the influence of particle size, particle structure and dispersion of titanium dioxide on the coverage of white ink. Generally, in the range greater than 1/2 of the wavelength of visible light, 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 coverage. Due to the obvious crystal structure of titanium dioxide itself, its refractive index is larger than that of color developing agent, and the greater the difference between the two refractive indexes, the stronger the hiding power of titanium dioxide used. Practice has proved that rutile titanium dioxide has better hiding power than anatase titanium dioxide, so it is more widely used in ink manufacturing

3. Influence on the tinting power of ink the tinting power of titanium dioxide depends on the scattering ability of titanium dioxide to visible light, and it has a direct impact on the tinting power of ink. The larger the scattering coefficient is, the stronger the tinting power is; The higher the refractive index of titanium dioxide, the stronger the coloring power. Titanium dioxide has the highest refractive index among white pigments, and the refractive index of rutile titanium dioxide is higher than that of anatase titanium dioxide. Therefore, titanium dioxide with strong scattering ability and high refractive index should be selected

4. The influence on dispersion performance of titanium dioxide particle shape and light reflection uniformity directly affect the dispersion performance of titanium dioxide. If titanium dioxide particles have smooth surface and uniform reflection, their dispersion is good, and the gloss and whiteness of the prepared white ink are also good; On the contrary, if the particle surface is rough and the diffuse reflection increases, the gloss will be greatly reduced and the dispersion will be poor, which will directly affect the whiteness and transfer performance of white ink. Therefore, titanium dioxide must be treated before use

to sum up, with the domestic reports that Huang believes that the carbon nanotube with a diameter of 0.7nm has superconductivity through calculation and the rapid development of the outer packaging and publishing and printing industry, the market demand for ink will increase day by day. The material testing machine is a material testing machine that integrates the functions of stretching, bending, tightening, shearing, ring stiffness and so on. As a very important white pigment in ink, A little less titanium dioxide in the heart has many properties and functions that cannot be replaced by any other material. Therefore, the use of titanium dioxide in ink will increase year by year, and the market application prospect will be very broad