Technical research to improve weather resistance of titanium dioxide
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Last Update: 2020-12-25
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Source: Internet
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Author: User
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Introduction
Titanium dioxide, or TiO2Pigment
, is a
chromication force
and the best covering force of white inormeric
pigment
, widely used in coatings, plastics, paper, printing
ink
, chemical fiber, rubber and cosmetics industries.
As an industrial grade titanium dioxide products need to be reprocessed according to the characteristics of different application areas (such as coatings, plastics, paper and other industries), the aim is to improve its application performance, such as improving the weather resistance of titanium dioxide, improve the dispersion of titanium dioxide in different media and application systems, improve the wetting of titanium dioxide, improve the masking power and gloss. Among them, weather resistance is the main application performance of high-grade titanium dioxide, but also in many applications to characterties of titanium dioxide quality of important indicators. Therefore, in the titanium white industry to improve the weather resistance of titanium dioxide technology has become an important symbol on behalf of the technical level of enterprises.1 Titanium white powder weather resistance
weather resistance is one of the pigment properties of titanium white powder, pigment after painting, coating by the sun and rain, by the sun, oxygen, water and temperature, such as the combined effect of yellowing, loss of light, powder and weight loss and other aging phenomena, pigments have the ability to resist the above changes (or the ability to resist UV erosion), called weather resistance.
the main reasons for the poor weather resistance of titanium dioxide are:
(1) the photochemical activity of pigments; The photochemical activity of titanium white powder is relatively strong, because of some defects in its lattice, in the sun, especially ultraviolet radiation and water, catalyst, titanium white powder ti4 plus is very easy to be reduced to Ti3 plus, while releasing a very strong reaction activity of primary ecological oxygen, resulting in the oxidation of organic matter as a paint base, the occurrence of polymer chain breakage and degradation, the formation of soluble or volatile substances, thus undermining the continuity of the coating.
In order to improve the weather resistance of titanium dioxide, titanium white powder can be coated with film treatment, in titanium white powder particles surface bread covered with a layer of "dense film", to prevent direct exposure to ultraviolet light, and titanium white powder particles and paint-based organic matter isolation, reduce the destructive power of photochemical effects, avoid degradation, and thus improve its weather resistance.2 Test Part
Before studying to improve the weather resistance of titanium dioxide, it is necessary to determine the application field of titanium dioxide, combined with the needs of the application field and the actual application environment, to determine the technical solution to improve the weather resistance of titanium dioxide. Because the crystal structure of the redstone (R) type titanium white powder is more closely than that of the sharp titanium (A) type titanium white powder structure, type A is 10 times more photoactive than type R, so type R has better weather resistance than type A. The titanium dioxide selected in this technical study is R-type titanium white powder.
In the weather-resistant treatment of titanium dioxide, titanium white powder is covered with aluminum or silicon oxides to increase weather resistance, anti-aging, and improve the dispersion of titanium-white particles in the medium, known as inorganic envelope method. Aluminum or silicon oxides are also commonly used in inorganic envelope coating reagents, this technology based on traditional methods to study the dense silicon coating technology, but also explore a new coating reagent coating technology, in different ways to ensure that titanium white in the application of excellent weather resistance. Based on an analysis of different models of
DuPont
(see Table 1), it was found that traditional coating methods allowed the identification of the primary weather resistance of silicon, while aluminum played a key role in gloss. In this paper, while the traditional silicon envelope technology is being studied, the phosphate coating is analyzed and studied in combination with practical application.(See all pictures online of China Paint News) 2.1 Silicon coating 2.1.1 Experimental raw materials and instruments (1) Raw materialsunsophageed chloride R type titanium white slurry, sodium silicate, aluminum sulfate, hydrochloric acid, sulfuric acid, sodium alumina: Jinzhou Titanium Co., Ltd.(2) instruments and equipment H. S11-Ni2 type electric thermostat water bath pot: Beijing Chang'e Yong Creative Scientific Instrument Co., Ltd.; FN101-1A type blow drying box: Changsha instrument factory manufacturing; YZ1515 LanGe-Pump: Baoding Langer Heng current pump Co., Ltd.; YQ50 laboratory small gas powder machine: Shanghai Sai San Company; SHB-III.A circulating water multi-use vacuum pump: Zhengzhou Great Wall Science, Industry and Trade Co., Ltd.; dial viscosity meter: Brookfield Corporation of the United States.
2.1.2 Experimental methodsTake a certain amount of R-type titanium white slurry, fully dispersed after heating to a certain temperature, add sodium silicate solution, use pH regulator to maintain a certain pH for coating treatment, cooked for a certain period of time after cooling, feeding, washing to water-soluble salt qualified, solid liquid separation, drying, crushing, that is, to obtain a silicon coating sample.2.1.3 detection method (1) acid solubility determination: the lower the value, the more uniform and complete the dense silicon coating.(2) envelope morphology: high-resolution transmission mirror (TEM) scanning samples.2.1.4 Results Discuss the dispersion conditions before the (1) coating take a certain amount of R-type titanium white slurry, pH adjusted to 8.0 to 10.0, stirring dispersion, viscosity
measurement
;As can be seen from Table 2, with the improvement of the pH of the R-type titanium white slurry, the dispersion viscosity decreases, i.e. the dispersion effect becomes better, and with the increase of the dispersant addition, the viscosity changes in the curve, and the addition of the dispersant at the peak of the curve is 0.2%.Table 2 Effect of dispersant addition on the viscosity of titanium white slurry and its change rate (See all picture news on China Paints Online) (2) pH regulator using aluminum sulfate, hydrochloric acid, sulfuric acid 3 different acidic solutions as pH regulator, silicon coating treatment, different pH regulator experimental sample test results see Table 3.tableTable 3 different pH regulator silicon coating sample acid solubility test results(see all pictures of China Paint Online News)From Table 3, it can be seen that the use of hydrochloric acid and sulfuric acid as pH regulator silicon envelope sample acid solubility is low, indicating that a single silicon coating film than silicon aluminum coating sample acid solubility is lower, that is, aluminum sulfate is not conducive to dense silicon coating.(3) Silicon coating agent dosagein SiO2 silicon coating volume, test the relationship between silicon coating volume and sample acid solubility, the test results are shown in Figure 1.from Figure 1, it can be seen that the amount of silicon coating film is inversely related to acid solubility, usually, the general weather-resistant varieties require acid solubility <1.0, high weather-resistant varieties require <0.5. The suitable silicon coating amount is 2.5% to 3.0%.(4) Best Scheme VerificationUsing the key conditions identified above for program verification, sample acid solubility of 0.2% to 0.4%, TEM micromorphological observation (see Figure 2), sample silicon coating film continuously, completely and uniformly wrapped on the surface of titanium dioxide particles, clearly visible.(see all pictures on China Paint Online News)
2.1.5 Experimental Conclusions (1) Coating Dispersion Conditions: Alkaline Environment pH -9 to 10, Dispersant addition 0.2% best;(2) acid regulator: hydrochloric acid and sulfuric acid effect is better than aluminum sulfate;
(3) silicon coating agent dosage: 2.5% to 3% best;(4) from scanning electro-mirror photos, the film layer is more uniform and dense, the coating effect is better.2.2 phosphorus, aluminum phosphorus double-layer coating 2.2.1 experimental raw materials unsophageed chlorinated R-type titanium white slurry, inoromic tantalum solution, inoromic phosphate solution, inoromic aluminum salt solution and pH regulator.2.2.2 Experimental MethodTake a certain amount of unstreated chlorinated R-type titanium white slurry, heat it to a certain temperature after full dispersion, add at least 1 inoromic salt solution, control pH with pH regulator within a certain range For coating treatment, ripe a certain time, add pH agent, control pH value in a certain range, carry out 2 wrap film treatment, ripe a certain time, material, washing to water-soluble salt qualified, drying, air flow crushing, that is, get a double coating sample.
2.2.3 Performance Determination of light resistance (E): Titanium white powder in the glycera medium, mixed with redox reactant, placed in ultraviolet light exposure, in the same time, to irradiate before and after
chromic difference
changes to assess the stability of titanium dioxide UV light. The lower the detection value, the better the light resistance of titanium dioxide.
2.2.4 Results Discussion (1) Aluminum phosphorus coating changes the amount of aluminum salt and phosphate, the aluminum phosphorus coating sample for light resistance testing, the results are shown in Figure 3.
As can be seen from Figure 3, the amount of aluminum and phosphorus coating is 4.5% to 4.8%, 0.8% to 0.9%, and the amount of aluminum and phosphorus coating is >5%, 0.6% to 0.7%, respectively, the amount of titanium white powder is the smallest, that is, the best resistance to light. (2) the phosphorus coating changes the amount of zirconium salt and phosphate, the phosphorus coating sample for light resistance testing. as can be seen from Figure 4, the amount of zirconium and phosphorus cling film was controlled at >0.3% and 0.02% to 0.10% respectively, the e-E of titanium dioxide was minimal, i.e. good light resistance. (View all pictures online picture news of China Paints) 2.2.5 Experimental Conclusions (1) Titanium white powder single aluminum, single molyx and single phosphorus coating film can not achieve better light resistance, double-layer coating aluminum phosphorus or zirconium phosphorus coating film volume control in a certain range, can get better light resistance performance is best. (2) compared with aluminum phosphorus coating, the phosphorus coating has better light resistance and meets the requirements of the application industry. 3 product performance and foreign famous titanium dioxide brand weather-resistant products compared to the test situation in Table 4. As you can see, the performance of the two is basically the same. (See all pictures online of Chinese coatings news) 4 Conclusion (1) Titanium white powder coating premise is that the TiO2 particles in titanium white slurry are fully dispersed conditions; (2) silicon coating film can improve the product's weather resistance, but different coating conditions affect the degree of tightness of the silicon film, Thus affecting the weather resistance of titanium dioxide, (3) phosphorus coating technology can effectively improve the light resistance of titanium white powder (one of the main weather resistance performance), the addition control of zirconium phosphorus is the key point of technology; (4) silicon coating and phosphorus envelope can play a role in improving the weather resistance of titanium white powder, silicon coating and phosphorus coating experimental products to achieve similar levels abroad.
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