Papermaking is the third largest user of
Titanium Dioxide. In low grade paper, titanium dioxide will not be used in consideration of production cost, but porcelain clay, talcum powder and calcium carbonate are mainly used, but they will reduce the strength of paper and increase the weight of paper. Titanium dioxide must be used in decorative paper, Bible paper and banknotes (such as dictionaries, pictorials, magazine covers, computers, banknotes, copier paper and decorative paper, etc.). The paper with titanium dioxide has good whiteness, high strength, luster, thin and smooth, and does not penetrate when printing. Under the same conditions, the opacity is 10 times higher than that of calcium carbonate and talc powder, and the weight can be reduced by 15% ~ 30%.
Decorative paper, also known as titanium white paper, is mainly used to make furniture, flooring, wallpaper and other raw materials. Rutile must be used for paper with anti-aging requirements, and more rutile is used in high ash paper. This high ash paper must be rutile because the covering power of anatase titanium dioxide is not enough. Anatase titanium white is used in low ash paper, such as Bible paper and paper money. Bible paper requires good opacity, which can be satisfied by using anatase titanium dioxide. Mint paper also requires good opacity, mainly using anatase. In China, the amount of titanium dioxide used in decorative paper is much higher than that of the other two varieties. This situation is determined by the consumption level of China. Due to the large demand for house decoration and high-grade furniture, the consumption of decorative paper is gradually increasing; the cost of Bible paper is far higher than that of ordinary paper due to the use of titanium dioxide as raw material. In view of the domestic consumption level, the market of Bible paper is very limited; the manufacture and use of coin paper are controlled by the state, and the consumption is relatively stable, which will not affect the titanium dioxide market. According to incomplete estimates, the titanium dioxide used for decorative paper in China exceeds 30000 tons per year. The amount of titanium dioxide in decorative paper is 20-40%, and that in other paper is 1-5%. In recent years, the production of decorative paper is increasing rapidly due to the transformation of the production of decorative paper.
No matter what kind of paper (base paper), the production process is the same:
Rutile is used for weather resistant and high ash paper, while anatase is used for paper with low weather resistance and low ash content. The main reason for paper mills to choose titanium dioxide is the cost of paper making, that is, the cost performance of titanium dioxide. As the cost proportion of titanium dioxide in papermaking is as high as 30-50%, so the paper mill is very careful about the choice of titanium dioxide under the condition of meeting the user's requirements. If the titanium dioxide can be used, rutile will not be used. The paper industry's requirements for titanium dioxide quality are as follows
1) Covering power (opacity): the ability of paper containing the same titanium dioxide to cover the background color, which determines the cost performance of titanium dioxide. In short, the cost of titanium dioxide per ton of paper may be lower due to the high price of titanium dioxide with high covering power, but the amount of titanium dioxide used is small; the cost of titanium dioxide in each ton of paper is increased due to the low price but large amount of titanium dioxide;
2) Whiteness: the whiteness of titanium dioxide determines the appearance of paper after forming;
Difference between rutile titanium dioxide and anatase titanium dioxide
1. Physical property
1) Relative density
Among the common white pigments, the relative density of titanium dioxide is the smallest. Among the white pigments of the same quality, the surface area of titanium dioxide is the largest and the pigment volume is the highest.
2) Melting point and boiling point
Because anatase transforms into rutile at high temperature, the melting point and boiling point of anatase titanium dioxide are virtually nonexistent. Only rutile type titanium dioxide has melting point and boiling point. The melting point of rutile titanium dioxide is 1850 ℃, the melting point in air is (1830 ± 15) ℃, and the melting point in oxygen enriched titanium dioxide is 1879 ℃. The melting point is related to the purity of titanium dioxide. The boiling point of rutile titanium dioxide is (3200 ± 300) ℃, and the titanium dioxide is slightly volatile at this high temperature.
3) Dielectric constant
Because of its high dielectric constant, titanium dioxide has excellent electrical properties. When determining some physical properties of titanium dioxide, the crystal direction of titanium dioxide should be considered. The dielectric constant of anatase titanium dioxide is relatively low, only 48.
4) Conductivity
Titanium dioxide has the properties of semiconductor, its conductivity increases rapidly with the rise of temperature, and it is also very sensitive to hypoxia. The dielectric constant and semiconductor properties of rutile titanium dioxide are very important to the electronic industry, which can be used to produce ceramic capacitors and other electronic components.
5) Hardness
According to Mohs hardness scale, rutile titanium dioxide is 6-6.5, anatase titanium dioxide is 5.5-6.0, so anatase is used in chemical fiber matting to avoid abrasion of spinneret hole.
6) Hygroscopicity
Although titanium dioxide has hydrophilicity, its hygroscopicity is not very strong, rutile type is smaller than anatase type. The hygroscopicity of titanium dioxide is related to its surface area. The surface area is large and the hygroscopicity is high. It is also related to the surface treatment and properties.
7) Thermal stability
Titanium dioxide is a kind of material with good thermal stability.
2. Chemical properties
The chemical properties of titanium dioxide are very stable, which is a kind of ACID amphoteric oxide. It hardly reacts with other elements and compounds at room temperature, and has no effect on oxygen, ammonia, nitrogen, hydrogen sulfide, carbon dioxide and sulfur dioxide. It is not soluble in water and fat, nor soluble in dilute acid, inorganic acid and alkali, but only soluble in hydrofluoric acid. However, under the action of light, titanium dioxide can undergo continuous oxidation-reduction reaction and has photochemical activity. This kind of photochemical activity is especially obvious under ultraviolet irradiation. This property makes titanium dioxide a photosensitive oxidation catalyst for some inorganic compounds and a photosensitive reduction catalyst for some organic compounds.
3) Dispersibility: dispersant is generally used in papermaking process, so the water dispersibility of titanium dioxide is little different;
4) Weather resistance: domestic rutile can meet the requirements of most paper weatherability, only a few papers need rutile to provide high weatherability;
5) Retention rate: in the paper industry, the filtered water is recycled or retention aid is used. Generally, the recovery rate of titanium dioxide is more than 99%. The reason why this index is retained is that the international titanium dioxide companies provide retention aid formula and use method when promoting paper-making special titanium dioxide, so as to improve service quality and increase product competitiveness.
