Preparation method of high-brightness white high-weatherability titanium white powder

Abstract

The application discloses a preparation method of high-brightness white high-weather-resistant titanium white powder, and comprises the following steps: S1, taking metatitanic acid slurry, using antimony source, magnesium source, phosphorus source and zirconium source as a salt treatment agent, calcining to obtain titanium white powder; S2, the titanium white powder is ground multiple times to obtain qualified slurry; in the multiple grinding process, a dispersing agent, citric acid or a citric acid derivative, is added; S3, a silicon source is added to the slurry to coat a silicon oxide film layer; and S4, a zinc source, a titanium source and a surfactant are continuously added to the slurry to coat a zinc titanate film layer. Through optimization and improvement of the salt treatment agent, dispersion of the dispersing agent in the grinding process, and coating modification of the surface silicon oxide film layer and the zinc titanate film layer, the titanium white product with high blue phase and high weather resistance can be obtained, and the titanium white powder can meet the requirements of scenes with high requirements for whiteness and weather resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of titanium dioxide preparation, and particularly relates to a preparation method of high-brightness and high-weather-resistance titanium dioxide. BACKGROUND

[0002] Titanium dioxide, also known as TiO2, is a kind of white inorganic pigment, which is inert and does not react with most substances. It is non-toxic, has the best opacity, the best whiteness and brightness, and is considered to be the best white pigment in the world.

[0003] In the visible light wavelength range (400-700 nm), the most suitable particle size range of titanium dioxide particles is 200-350 nm, which is equivalent to half of the scattered visible light wavelength, so that the highest scattering rate and whiteness can be obtained. When the particle size is greater than 400 nm, the scattering ability is weakened, and the whiteness is reduced. When the particle size is less than 100 nm, light passes around the particles due to diffraction, and no reflection occurs, so the crystal particles are transparent, and people visually feel that the blue-white color is whiter than the pure white color. Therefore, the particle size is preferably controlled in the range of 0.2-0.35 μm.

[0004] Metatitanic acid prepared by hydrolysis of titanium sulfate is amorphous (except for using rutile type seeds), and although long-time calcination at high temperature (below 1050℃) can convert the product into rutile crystal form, the crystallization process will cause serious sintering, many crystal lattice defects, and large and hard crystal grains, and the product has poor pigment performance. In addition, high temperature often causes the crystal lattice to be deoxidized, so that the product is gray. Therefore, in production, some rutile-forming promoters and crystal type regulators must be added to metatitanic acid to make TiO2 grow at a reasonable speed, and pigment particles with complete crystal type conversion, moderate size and regular shape are produced at a lower calcination temperature. Therefore, salt treatment of metatitanic acid is required before calcination of pigment-grade titanium dioxide, otherwise the obtained base particles will be hard, the color phase and pigment performance will be poor, and the application performance will be reduced. Therefore, a small amount of chemicals needs to be added for modification during the production of titanium dioxide, and then the product obtained by calcination at a proper temperature has good color phase, excellent gloss, high color hiding power, low oil absorption, and excellent crystal size and dispersion in paint medium and weather resistance.

[0005] Zinc salt is the most widely used rutile promoting agent in the salt treatment process, which can accelerate the crystal transformation, improve the conversion rate, and reduce the transformation temperature, and has good grinding performance. However, it still has some problems such as poor weather resistance, poor oil dispersibility and yellow bottom phase. In addition, an adjusting agent (also known as a crystal type stabilizer) needs to be added to metatitanic acid to prevent the rutile titanium dioxide from converting too fast during calcination, and to form smooth and regular pigment particles with excellent performance, and to meet the special requirements of various grades of titanium dioxide. Potassium salt is a good crystal type adjusting agent. The presence of potassium salt can reduce the desulfurization temperature, improve the desulfurization speed, improve the hiding power, increase the pigment performance of the product, and make the product maintain softness while increasing brittleness, easy to crush, improve whiteness and hiding power. Because it can inhibit the transformation of anatase to rutile, it also plays a role in crystal type stabilization. In addition, at high calcination temperature, the titanium dioxide particles are relatively dense, which is beneficial to improve the weather resistance and reduce the oil absorption. Aluminum salt is used as a rutile inhibitor, which can make the titanium dioxide particles grow uniformly, thereby improving the hiding power. However, the calcination temperature is high and the energy consumption is high. Phosphorus salt is used as an iron ion masking agent, which can improve the whiteness and weather resistance of the product, and the particles are relatively soft and easy to crush. If the amount of phosphorus salt is too large, it will cause the product to have low hiding power, low pH, high oil absorption, small bulk density, and large viscosity of the system during use. In addition, it will also cause the product to have poor brittleness and high viscosity.

[0006] In the current technology, there are many studies on salt treatment. Patent CN 107140685 A uses magnesium salt, ammonium salt and antimony salt for salt treatment, and the rutile conversion rate is generally as high as 99.7% or more, which significantly reduces the photocatalytic activity of titanium dioxide product. However, the application does not consider the application performance of the pigment, and the weather resistance is poor.

[0007] Patent CN 111573726 A adds calcination aids, calcination seeds, antimony salt and zirconium salt in any order and calcines, which can obtain a product with stable crystal lattice, good dispersibility, good heat resistance and anti-yellowing property, uniform and narrow particle size distribution, and blue bottom color, good whiteness, hiding power and weather resistance. However, the hardness of the product prepared by the salt treatment is large, which is not easy to grind, and the product is a special titanium dioxide base for powder coating, which limits its application in other fields.

[0008] Patent CN 101200306 A develops a salt treatment agent using potassium salt, phosphorus salt and zirconium salt to solve the problems of low whiteness and high hardness of the product. Potassium salt and phosphorus salt are used to adjust the particle morphology and particle hardness during calcination, antimony salt is used to improve the whiteness of the product, and potassium can make the titanium dioxide loose and reduce the sintering element, thereby obtaining a product with high brightness and blue index, which broadens the application field of the product. However, the patent has a sintering phenomenon.

[0009] Patent CN101851435A uses potassium salt, phosphorus salt, zinc salt, aluminum salt and antimony salt as salt treating agent to obtain base material with high brightness blue direction, but the initial salt treating agent has large addition amount, high conductivity and large beating viscosity.

[0010] Patent CN101880479B uses potassium salt, phosphorus salt, zinc salt and magnesium salt as salt treating agent to obtain crystal lattice stable, good dispersibility, heat resistance, yellowing resistance, oil white, color reduction and weather resistance, but the patent is a product specially used for powder coating, has narrow application field and the particles are easy to sinter due to lack of Al salt. Zuo Qiang in "Preparation and Performance of High Brightness Blue Base Phase Titanium Dioxide" uses zirconium salt and antimony salt to simultaneously treat hydrolyzed metatitanic acid to obtain high brightness blue base phase rutile titanium dioxide, but the salt treating formula has large particle hardness and is not easy to grind.

[0011] Therefore, it is of great significance to develop a general titanium dioxide with high brightness and high weather resistance. SUMMARY

[0012] The purpose of the present application is to provide a general titanium dioxide with high brightness and high weather resistance to solve the problems in the prior art.

[0013] The purpose of the present application is achieved by the following technical scheme:

[0014] A preparation method of high brightness and high weather resistance titanium dioxide, comprising the following steps:

[0015] S1. taking metatitanic acid slurry, using antimony source, magnesium source, phosphorus source and zirconium source as salt treating agent to calcine to obtain titanium dioxide initial product;

[0016] S2. grinding the titanium dioxide initial product to obtain slurry with qualified particle size; adding dispersant citric acid or citric acid derivative in the process of multiple grinding;

[0017] S3. adding silicon source to the slurry to coat silicon oxide film layer;

[0018] S4. continuously adding zinc source, titanium source and surfactant to the slurry to coat zinc titanate film layer.

[0019] Preferably, the antimony source is added in an amount of 0.1-0.3% of the mass of titanium dioxide in metatitanic acid; the magnesium source is added in an amount of 0.1-0.2% of the mass of titanium dioxide in metatitanic acid; the phosphorus source is added in an amount of 0.1-0.2% of the mass of titanium dioxide in metatitanic acid; and the zirconium source is added in an amount of 0.1-0.2% of the mass of titanium dioxide in metatitanic acid.

[0020] Preferably, the antimony source is one or a combination of antimony sulfate and antimony chloride; the magnesium source is one or a combination of magnesium sulfate, magnesium chloride and magnesium nitrate; the phosphorus source is phosphoric acid; and the zirconium source is one or a combination of zirconium oxychloride and zirconium sulfate.

[0021] Preferably, the multiple grinding in step S2 comprises, in sequence, roll grinding, wet grinding and sand grinding, the sand grinding is to a D50 of 0.30-0.35 μm and a PSD≤1.50 of a qualified particle size; and the dispersant is added in the wet grinding process.

[0022] Preferably, the dispersant is used in an amount of 1-10 ‰ of the mass of the titanium dioxide primary product.

[0023] Preferably, the coating of the silicon oxide film layer in step S3 further comprises:

[0024] The slurry concentration is first adjusted to 280-320 g / L of titanium dioxide, the temperature is adjusted to 75-95 °C, then the slurry pH is adjusted to 10.2-10.4, the silicon source is added, the silicon source is added in an amount of 1-3% of the mass of the titanium dioxide in the slurry in terms of SiO2, and then homogenized, the slurry pH is adjusted to 6.8-7.2, and then homogenized again to form the silicon oxide film layer.

[0025] Preferably, the coating of the zinc titanate film layer in step S4 further comprises:

[0026] The zinc source, the titanium source and the surfactant are simultaneously added to the slurry, and a pH adjuster is also simultaneously added to maintain the slurry pH at 7-9, and then homogenized to form the zinc titanate film layer; the zinc source is used in an amount of 1-2% of the mass of the titanium dioxide in the slurry in terms of ZnO; and the titanium source is used in an amount of 0.5-1.0% of the mass of the titanium dioxide in the slurry in terms of TiO2.

[0027] Preferably, the surfactant in step S4 is polyethylene glycol, and is added in an amount of 0.1-1% of the mass of the titanium dioxide in the slurry.

[0028] Preferably, after step S4, there is further a step of coating with aluminum oxide; the coating with aluminum oxide comprises the following steps:

[0029] The slurry temperature is adjusted to 40-60 °C, then the aluminum source is added, and the slurry pH is simultaneously controlled to 7.5-9.5, and then homogenized to form the aluminum oxide film layer.

[0030] Preferably, after the coating with aluminum oxide, there is further a step of adjusting the slurry pH to 5.0-7.0 and homogenizing for 1-3 h.

[0031] Therefore, through the optimization of the salt treatment agent, the dispersion of the dispersant in the grinding process, and the coating modification of the surface silicon oxide film and the zinc titanate film, a high blue phase and high weather-resistant titanium white product can be obtained to meet the requirements of high whiteness and weather resistance of titanium white powder in some scenes. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 is the result graph of the 60° gloss retention of the titanium white powder provided in examples 1-3 and comparative examples 1-5 in the xeon lamp rapid aging experiment of alkyd amino resin system. DETAILED DESCRIPTION

[0033] The application provides a preparation method of high-brightness and high-weather-resistant titanium white powder, which comprises the following steps:

[0034] S1. Taking metatitanic acid slurry, using antimony source, magnesium source, phosphorus source and zirconium source as salt treatment agent, calcining to obtain titanium white powder; preferably, the antimony source is one or a combination of antimony sulfate and antimony chloride, the addition amount is 0.1-0.3% of the mass of titanium dioxide in metatitanic acid, and the antimony sulfate and antimony chloride are added in the form of solution, and the concentration is preferably 80-120 g / L of antimony oxide; the magnesium source is one or a combination of magnesium sulfate, magnesium chloride and magnesium nitrate, the addition amount is 0.1-0.2% of the mass of titanium dioxide in metatitanic acid, and the magnesium sulfate, magnesium chloride and magnesium nitrate are added in the form of solution, and the concentration is preferably 80-120 g / L of magnesium oxide; the phosphorus source is phosphoric acid, the addition amount is 0.1-0.2% of the mass of titanium dioxide in metatitanic acid, and the phosphoric acid is added in the form of solution, and the concentration is preferably 40-60 g / L of diphosphorus pentoxide; the zirconium source is one or a combination of zirconium oxychloride and zirconium sulfate, the addition amount is 0.1-0.2% of the mass of titanium dioxide in metatitanic acid, and the zirconium oxychloride and zirconium sulfate are added in the form of solution, and the concentration is preferably 80-120 g / L of zirconium dioxide; the calcination temperature is preferably 500-1000 DEG C, which can fully promote the conversion of titanium dioxide crystal form.

[0035] The application first uses the combination of antimony source, magnesium source, phosphorus source and zirconium source as salt treatment agent, wherein the phosphorus source can be used as iron ion masking agent to mask the residual Fe 3+ At the same time, phosphorus will not invade the inside of the TiO2 crystal lattice with the increase of temperature, but will be adsorbed on the surface, and in the process of TiO2 particle growth and crystal formation, these adsorbed phosphate on the surface will prevent the sintering and growth of titanium dioxide particles, so that the particle size and distribution can be guaranteed; on this basis, the antimony source added in the salt treatment process further masks Fe 3+impurities into the titanium dioxide crystal, which helps to improve the whiteness of the product, reduce the occurrence of light color mutual transformation phenomenon, and obtain a blue phase titanium dioxide product. Meanwhile, the introduction of the doping ion antimony will produce local lattice distortion, thereby inhibiting the growth of TiO2 crystal grains. On the other hand, the zirconium added in the salt treatment process replaces the titanium atoms together with the Sb atoms, and the local lattice distortion produced by the two atoms cancels out each other, that is, it ensures the role of the antimony source and the zirconium source in the titanium dioxide product. On the other hand, the Zr atoms and Sb atoms are replaced alternately, and the dispersant added in the grinding process reduces the surface energy of the titanium dioxide product, thereby achieving good dispersion effect. Therefore, the use of the above combined salt treatment agent can effectively shield Fe 3+ impurities, improve the whiteness of the titanium dioxide product, inhibit the growth of TiO2 crystal grains, ensure the particle size distribution of the titanium dioxide product, and also reduce the surface energy of the titanium dioxide product and improve the dispersibility of the titanium dioxide product. After high-temperature calcination, the crystal type conversion rate can reach 97.5-99.5%.

[0036] S2. The titanium dioxide product is ground multiple times to prepare a slurry with qualified particle size. During the multiple grinding process, a dispersant such as citric acid or a citric acid derivative is added, and the amount is preferably 1-10‰ of the mass of the titanium dioxide product. Preferably, the multiple grinding includes roll grinding, wet grinding and sand grinding in sequence. The roll grinding can initially crush the titanium dioxide product, then a certain volume of water is added for wet grinding to preliminarily disperse and refine the titanium dioxide product. The dispersant is preferably added during the wet grinding process, which has good dispersion effect and prevents the agglomeration of the slurry after adding water. On the other hand, during the subsequent silicon oxide film coating process, the dispersion induction effect of the dispersant can improve the density and uniformity of the silicon film, thereby obtaining a high-weather-resistant product. The concentration of the slurry after wet grinding is generally 500-1000 g / L. Finally, the slurry is fully ground by high-strength sand grinding until the D50 is 0.30-0.35 μm and the PSD is ≤1.50, which is qualified in terms of particle size.

[0037] S3. A silicon source is added to the slurry for silicon oxide film coating. The silicon oxide film can effectively isolate light from contacting with titanium dioxide, thereby improving the weather resistance of the titanium dioxide product. The dispersant such as citric acid or a citric acid derivative added during the grinding process can induce the density and uniformity of the silicon oxide film, thereby further improving the weather resistance of the titanium dioxide product.

[0038] S4. A zinc source, a titanium source and a surfactant are continuously added to the slurry for coating of zinc titanate (ZnTiO3) precursor precipitate. Through the reaction of the zinc source and the titanium source, a zinc titanate film can be formed on the surface of the silicon oxide film.

[0039] ZnTiO3 is composed of ZnO-TiO2 from the chemical formula, the film layer precursor can not only increase the adhesion of the film layer, but also the white precipitate prepared will not affect the hue of the product. In the process of forming the zinc titanate film layer, the surfactant added at the same time can change the surface state of the titanium dioxide nanoparticles, reduce its specific surface energy, prevent the aggregation, combination and growth of the particles, and prevent the transformation of the particles into hard agglomerates during heat treatment; at the same time, the wetting angle θ is small, thereby increasing the wettability and permeability, changing the properties of the film layer, causing the Gibbs free energy of the zinc titanate to be negatively shifted, and accordingly increasing the reaction active center, so that the zinc titanate film layer is more easily formed, and the formation of the zinc titanate film is effectively promoted.

[0040] The surfactant is preferably polyethylene glycol (PEG), and the addition amount is 0.1-1% of the mass of the titanium dioxide in the slurry. The molecular formula of the polyethylene glycol is HO-(CH2CH2O)n-H, which has only two hydrophilic groups of ether and hydroxyl groups and no hydrophobic group. The molecular chain is in a snake shape in the aqueous solution, easily establishes a strong hydrogen bond with the surface of the hydroxide colloid particles, and thus forms a macromolecular hydrophilic film on the surface of the colloid particles, resulting in a space steric hindrance effect, changing the surface state of the nanoparticles, reducing its specific surface energy, and preventing the aggregation, combination and growth of the particles. The addition of the surfactant here prevents the growth of the particles by the space steric hindrance effect, and improves the surface state of the film layer and reduces the surface energy.

[0041] The polyethylene glycol is further preferably polyethylene glycol 400.

[0042] Therefore, by optimizing the salt treatment agent, the dispersion effect of the dispersant citric acid or citric acid derivative in the grinding process, and the coating modification of the surface silicon oxide film layer and the zinc titanate film layer, a high blue phase and high weather-resistant titanium white product can be obtained, which meets the requirements of high whiteness and weather resistance of the titanium white powder in some scenes.

[0043] Preferably, the coating of the silicon oxide film layer in step S3 further comprises:

[0044] First, the slurry concentration is adjusted to 280-320 g / L of titanium dioxide, and the temperature is adjusted to 75-95℃. Then the slurry pH is adjusted to 10.2-10.4, the silicon source is added, the addition amount of the silicon source is 1-3% of the mass of the titanium dioxide in the slurry in terms of SiO2, and the slurry is homogenized. Then the slurry pH is adjusted to 6.8-7.2, and the slurry is homogenized again to form a silicon oxide film layer. The silicon source is preferably sodium silicate and / or potassium silicate, and is further preferably sodium silicate. The silicon source is added in the form of a solution, and the solution concentration is 80-120 g / L in terms of SiO2.

[0045] Preferably, the coating of the zinc titanate film layer in step S4 further comprises:

[0046] The zinc source, the titanium source and the surfactant are added into the slurry simultaneously, and a pH regulator (such as sodium hydroxide) is also added simultaneously to maintain the pH of the slurry at 7-9, to generate white flocculent Zn(OH)2 / TiO(OH)2precipitate, which is homogenized to form a zinc titanate precursor film layer; the basic equation of the precipitation reaction is as follows:

[0047] TiOCl2+ ZnSO4+ NaOH → Zn(OH)2 / TiO(OH)2↓

[0048] The amount of the zinc source, calculated as ZnO, is 1-2% of the mass of titanium dioxide in the slurry; the amount of the titanium source, calculated as TiO2, is 0.5-1.0% of the mass of titanium dioxide in the slurry. The zinc source is preferably one or a combination of zinc chloride, zinc sulfate and zinc nitrate, which is added in the form of a solution, and the concentration of the solution, calculated as zinc oxide, is 80-120 g / L. The titanium source is preferably one or a combination of titanium oxychloride and titanium oxysulfate, which is added in the form of a solution, and the concentration of the solution, calculated as titanium dioxide, is 80-120 g / L. The pH regulator is one or a combination of NaOH, ammonia and Na2CO3.

[0049] Preferably, after step S4, there is also a step of alumina coating, and further preferably, a step of loose boehmite alumina coating, through the reticular or banded structure of the alumina, the dispersion performance and the water washing and filtering performance of the titanium dioxide pigment can be improved, and thus a high-brightness and high-weather-resistance titanium white powder can be prepared. The loose boehmite alumina coating can be prepared by a conventional coating method, and the present application provides a preferred coating method, which specifically comprises the following steps:

[0050] The temperature of the slurry is adjusted to 40-60°C, then an aluminum source is added, and the pH of the slurry is controlled to 7.5-9.5 at the same time, and after homogenization, an alumina film layer is formed. The aluminum source is preferably sodium aluminate and / or aluminum sulfate, and the amount of the aluminum source, calculated as Al2O3, is 2-4% of the mass of titanium dioxide in the slurry.

[0051] Preferably, after the alumina coating, there is also a step of adjusting the pH of the slurry to 5.0-7.0, homogenizing for 1-3 hours, and then preparing a titanium white powder through water washing, flash evaporation and steam powdering. Finally, adjusting the slurry to weakly acidic to neutral is conducive to water washing.

[0052] Example 1

[0053] To the metatitanic acid slurry, 0.1% antimony chloride (calculated as Sb2O3) was added and stirred for 15 minutes; 0.1% magnesium chloride (calculated as MgO) was added and stirred for 20 minutes; 0.1% phosphoric acid (calculated as P2O5) was added and stirred for 30 minutes; finally, 0.1% zirconium sulfate (calculated as ZrO2) was added and stirred for 90 minutes, then the slurry was pressed and calcined at 930°C to obtain the primary product of titanium dioxide; the primary product was ground by a pair of rollers, then 3.0‰ sodium citrate dispersant was added and the slurry was pumped into a coating tank after wet grinding and sand grinding to obtain a particle size that met the requirements; the slurry concentration was adjusted to 300 g / L of titanium dioxide, the temperature was raised to 80°C, and the pH was adjusted to 10.2 by adding alkali, and the slurry was homogenized for 20 minutes; 1% sodium silicate solution was added, and the sodium silicate was added for 30 minutes, then the slurry was homogenized for 30 minutes; the pH of the slurry was adjusted to 7.0 by adding acid, and the slurry was homogenized for 30 minutes; 1% ZnSO4 solution, 0.5% TiOCl2 solution, 0.3% polyethylene glycol 400, and NaOH were added to the slurry at the same time, the pH was controlled at 7.0, and the addition was completed in 60 minutes, then the slurry was homogenized for 30 minutes; the slurry was cooled to 50°C, and sodium aluminate and aluminum sulfate were added to the slurry in a total amount of 2% of aluminum, the mass ratio of sodium aluminate to aluminum sulfate (both calculated as Al2O3) was 1.2, the pH of the concurrent flow was 8.0, the concurrent flow addition time was 120 minutes, and then the slurry was homogenized for 30 minutes; the final pH of the slurry was adjusted to 6.5 by adding acid, and the slurry was homogenized for 2 hours; the slurry was washed with water until the conductivity reached 80 μs / cm to obtain a three-washing filter cake; the filter cake was subjected to flash evaporation and steam powdering to obtain the finished product of titanium dioxide.

[0054] Example 2

[0055] To the metatitanic acid slurry, 0.15% antimony chloride (calculated as Sb2O3) was added and stirred for 15 minutes; 0.15% magnesium chloride (calculated as MgO) was added and stirred for 20 minutes; 0.15% phosphoric acid (calculated as P2O5) was added and stirred for 30 minutes; finally, 0.15% zirconium sulfate (calculated as ZrO2) was added and stirred for 90 minutes, then the slurry was pressed and calcined at 950°C to obtain the primary product of titanium dioxide; the primary product was ground by a pair of rollers, then pumped into a coating tank after wet grinding and sanding with 5.0‰ sodium citrate dispersant; the slurry concentration was adjusted to 300 g / L of titanium dioxide, the temperature was raised to 85°C, the pH was adjusted to 10.3 by adding alkali, and the slurry was homogenized for 20 minutes; 2% sodium silicate solution was added over a period of 30 minutes, and the slurry was homogenized for 30 minutes; the pH of the slurry was adjusted to 7.0 by adding acid, and the slurry was homogenized for 30 minutes; 1.5% ZnSO4 solution, 0.75% TiOCl2 solution, 0.5% polyethylene glycol 400, and NaOH were added to the slurry simultaneously, the pH was controlled at 8.0, the addition was completed over a period of 60 minutes, and the slurry was homogenized for 30 minutes; the slurry was cooled to 50°C, and 3% sodium aluminate and aluminum sulfate were added to the slurry in parallel flow, the mass ratio of sodium aluminate to aluminum sulfate (both calculated as Al2O3) was 1.3, the parallel flow pH was 8.0, the parallel flow addition time was 120 minutes, and the slurry was homogenized for 30 minutes; the final pH of the slurry was adjusted to 6.6 by adding acid, and the slurry was homogenized for 2 hours; the slurry was washed with water until the conductivity reached 80 μs / cm, and a three-wash filter cake was obtained; the filter cake was then subjected to flash evaporation and steam powdering to obtain the finished product of titanium dioxide.

[0056] Example 3

[0057] To the metatitanic acid slurry, 0.20% antimony chloride (calculated as Sb2O2) was added and stirred for 15 minutes; 0.20% magnesium chloride (calculated as MgO) was added and stirred for 20 minutes; 0.20% phosphoric acid (calculated as P2O5) was added and stirred for 30 minutes; finally, 0.20% zirconium sulfate (calculated as ZrO2) was added and stirred for 90 minutes. The slurry was then pressed and calcined at 980°C to obtain the crude titanium dioxide product. The crude product was ground by a pair of rollers and then pumped into a coating tank after wet milling and sand milling to obtain a particle size that met the specifications. The slurry concentration was adjusted to 300 g / L (calculated as TiO2), and the temperature was raised to 90°C. The pH was adjusted to 10.4 by adding alkali, and the slurry was homogenized for 20 minutes. 3% sodium silicate solution was added over a period of 30 minutes, and the slurry was homogenized for 30 minutes. The pH of the slurry was adjusted to 6.8 by adding acid, and the slurry was homogenized for 30 minutes. 2.0% ZnSO4 solution, 1.0% TiOCl2 solution, 0.8% polyethylene glycol 400, and NaOH were simultaneously added to the slurry while controlling the pH at 8.5. The addition was completed over a period of 60 minutes, and the slurry was homogenized for 30 minutes. The slurry was cooled to 55°C, and 3% sodium aluminate and aluminum sulfate were added to the slurry, with the mass ratio of sodium aluminate to aluminum sulfate (both calculated as Al2O3) being 1.4. The pH of the concurrent stream was 8.0, and the concurrent addition was performed over a period of 120 minutes. The slurry was homogenized for 30 minutes. The final pH of the slurry was adjusted to 6.8 by adding acid, and the slurry was homogenized for 2 hours. The slurry was washed with water until the conductivity reached 80 μs / cm, and a three-wash filter cake was obtained. The filter cake was then subjected to flash evaporation and steam powdering to obtain the final titanium dioxide product.

[0058] Comparative Example 1

[0059] The salt treatment agent was replaced with aluminum sulfate (added amount 0.3%), phosphoric acid (added amount 0.2%), and zirconium sulfate (added amount 0.2%), and the remaining steps were the same as in Example 3.

[0060] Comparative Example 2

[0061] The salt treatment agent was replaced with magnesium chloride (added amount 0.2%), phosphoric acid (added amount 0.2%), and zirconium sulfate (added amount 0.2), i.e., the antimony salt was omitted, and the remaining steps were the same as in Example 3.

[0062] Comparative Example 3

[0063] The salt treatment agent was replaced with antimony chloride (added amount 0.2%), phosphoric acid (added amount 0.2%), and zirconium sulfate (added amount 0.2%), i.e., the magnesium salt was omitted, and the remaining steps were the same as in Example 3.

[0064] Comparative Example 4

[0065] Except that the dispersant sodium citrate was added before the pH adjustment in the coating step (sodium citrate was added in the coating tank, not in the wet milling process), the remaining steps were as described in Example 3.

[0066] Comparative Example 5

[0067] The same process as example 3 was used, except that the zinc titanate coating was replaced by a conventional zinc oxide coating step, and the remaining steps were the same as example 3.

[0068] Application test comparison

[0069] The slurries prepared in examples 1-3 and comparative examples 1-5 were tested for application performance using conventional methods in the art, and the results were as follows:

[0070] 1. Physico-chemical test comparison

[0071] Table 1

[0072] Sample Wg L b Fe Example 1 91.45 98.13 1.20 25 Example 2 91.66 98.17 1.15 23 Example 3 91.96 98.24 1.05 19 Comparative Example 1 91.26 98.09 1.35 33 Comparative Example 2 91.37 98.12 1.32 30 Comparative Example 3 91.41 98.15 1.25 27 Comparative Example 4 91.44 98.12 1.21 25 Comparative Example 5 91.42 98.10 1.20 26

[0073] 2. Evaluation of the weather resistance of titanium dioxide in alkyd resin

[0074] In the xenon lamp rapid aging experiment of the alkyd amino resin system, the change in the 60° gloss retention with time was as shown in Table 2 and Figure 1

[0075] Table 2

[0076]

[0077] From the above data, it can be seen that the titanium dioxide prepared in the present application has high brightness and high weather resistance.

[0078] While the preferred embodiments of the application have been described, additional variations and modifications can be made to the preferred embodiments by those skilled in the art once they learn of the basic inventive concepts. Therefore, the appended claims are intended to encompass within their scope all such variations and modifications as are included within the scope of the application. It should be apparent that the application is susceptible to various changes and modifications without departing from the spirit and scope of the application. Accordingly, it is intended that all such changes and modifications be included within the scope of the application as defined by the following claims and their equivalents.​

Claims

1. A preparation method of a high-brightness white high-weather-resistant titanium white powder, characterized by, The method comprises the following steps: S1. Taking metatitanic acid slurry, using antimony source, magnesium source, phosphorus source and zirconium source as salt treatment agent, calcining to obtain titanium dioxide primary product; S2. The titanium dioxide primary product is subjected to multiple grinding to prepare slurry with qualified particle size; During the multiple grinding, dispersant citric acid or citric acid derivative is added; S3. Silicon source is added to the slurry to coat silicon oxide film layer; S4. Zinc source, titanium source and surfactant are continuously added to the slurry, and pH regulator is also added to maintain the pH of the slurry at 7-9, and then homogenization is performed to form zinc titanate film layer.

2. The method according to claim 1, wherein the amount of the antimony source added in step S1 is 0.1-0.3% of the mass of titanium dioxide in the metatitanic acid, the amount of the magnesium source added is 0.1-0.2% of the mass of titanium dioxide in the metatitanic acid, the amount of the phosphorus source added is 0.1-0.2% of the mass of titanium dioxide in the metatitanic acid, and the amount of the zirconium source added is 0.1-0.2% of the mass of titanium dioxide in the metatitanic acid.

3. The method according to claim 1, wherein the antimony source is one or a combination of antimony sulfate and antimony chloride, the magnesium source is one or a combination of magnesium sulfate, magnesium chloride and magnesium nitrate, the phosphorus source is phosphoric acid, and the zirconium source is one or a combination of zirconium oxychloride and zirconium sulfate.

4. The method according to claim 1, wherein the multiple grinding in step S2 comprises, in sequence, roll grinding, wet grinding and sand grinding, and the sand grinding is performed to a D50 of 0.30-0.35 μm and a PSD≤1.50, and the dispersant is added during the wet grinding.

5. The method according to claim 4, wherein the amount of the dispersant is 1-10‰ of the mass of the titanium dioxide primary product.

6. The method according to claim 1, wherein the coating of the silicon oxide film layer in step S3 further comprises the following steps: firstly, adjusting the slurry concentration to 280-320 g / L of titanium dioxide, adjusting the temperature to 75-95 ℃, then adjusting the slurry pH to 10.2-10.4, adding the silicon source, the amount of the silicon source added being 1-3% of the mass of titanium dioxide in the slurry, homogenizing, then adjusting the slurry pH to 6.8-7.2, and homogenizing again to form the silicon oxide film layer.

7. The method according to claim 1, wherein the amount of the zinc source added in step S4 is 1-2% of the mass of titanium dioxide in the slurry, and the amount of the titanium source added is 0.5-1.0% of the mass of titanium dioxide in the slurry.

8. The method according to claim 1, wherein the surfactant added in step S4 is polyethylene glycol, and the amount of the polyethylene glycol added is 0.1-1% of the mass of titanium dioxide in the slurry. ​ ​ ​ ​ ​ ​ ​ 9. The preparation method of the high-brightness white high-weatherability titanium white powder according to claim 1, characterized in that, the step S4 is followed by an alumina coating, which comprises the following steps: the slurry temperature is adjusted to 40-60 DEG C, then the aluminum source is added, and the slurry pH is controlled to 7.5-9.5 at the same time, and the alumina film layer is formed after homogenization.

10. The preparation method of the high-brightness white high-weatherability titanium white powder according to claim 9, characterized in that, the alumina coating is followed by the step of adjusting the slurry pH to 5.0-7.0 and homogenizing for 1-3 h.

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