Titanium dioxide with multi-component composite coating, and preparation method therefor

Abstract

The present application relates to the field of chemical engineering. Particularly disclosed are titanium dioxide with a multi-component composite coating, and a preparation method therefor. The preparation method for the titanium dioxide comprises: S1, mixing a titanium dioxide slurry with a silicate solution, and then controlling the pH value by adding an inorganic acid solution twice; S2, adding a zirconate solution within a certain period of time, and controlling the pH value by using an alkali solution; S3, adding a meta aluminate solution within a certain period of time, and simultaneously adding an inorganic acid solution in a countercurrent manner to control the pH value; S4, continuously adding the meta aluminate solution within a certain period of time, and simultaneously adding an aluminum sulfate solution in a cocurrent manner to control the pH value; and S5, adjusting the pH value at the end point, continuing to conduct aging under agitation, and then conducting homogenizing, filtering, washing, dehydrating, drying, crushing and an organic treatment. The titanium dioxide prepared by the present application has relatively good optical properties and weather resistance, and can meet the development requirements of high-weather-resistance coatings for ships, bridges, solar energy, wind power and other emerging environmental protection applications.

Description

Multi-component composite coated titanium dioxide and its preparation method Technical Field

[0001] This application relates to the field of chemical engineering, specifically to the technical field of titanium dioxide, and more specifically, to a multi-component composite coated titanium dioxide and its preparation method. Background Technology

[0002] Titanium dioxide is the best-performing white pigment and an important chemical raw material. Due to its excellent and stable chemical properties, high refractive index, and good hiding power, it is widely used in coatings, plastics, papermaking, and inks. However, titanium dioxide, especially rutile titanium dioxide, is a photoactive semiconductor material. Under light irradiation, Ti... 4+ Easily reduced to Ti 3+ It releases highly reactive oxygen species, which degrade organic components in contact with it, leading to discoloration, chalking, and loss of gloss in related products such as coatings, resulting in decreased weather resistance and severely affecting the performance and service life of the coating. To address this issue, in the industrial production of titanium dioxide, nascent titanium dioxide is typically post-treated by coating its surface with a thin film of inert inorganic oxide to reduce its photocatalytic activity and thus improve its weather resistance.

[0003] However, due to technological limitations in coating processes, most existing outdoor weather-resistant titanium dioxide products are binary composite coatings with medium to low coating amounts, making them general-purpose titanium dioxide products. These general-purpose titanium dioxide products cannot meet the high weather resistance and other performance requirements of high-performance coatings, resulting in coatings with poor performance in outdoor applications. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a multi-component composite coated titanium dioxide and its preparation method.

[0005] Firstly, this application provides a method for preparing multi-component composite coated titanium dioxide, which adopts the following technical solution:

[0006] A method for preparing multi-component composite coated titanium dioxide includes the following steps:

[0007] S1. Titanium dioxide slurry and silicate solution are stirred and dispersed to obtain a mixed slurry. The temperature of the titanium dioxide slurry is 65-75℃, the mass concentration is 22-25%, and the pH value is 9.0-11.0. The amount of silicate solution added is 3.5-3.8% of the mass of TiO2 based on SiO2. Then, the temperature of the mixed slurry is controlled at 74-78℃. While stirring, the pH value of the mixed slurry is first adjusted and controlled to 8.8-9.0 with an inorganic acid solution within 180-200 min to complete the deposition of the first dense silicon film. Then, the pH value of the mixed slurry is adjusted and controlled to 7.5-7.8 with an inorganic acid solution within 90-100 min to complete the deposition of the second dense silicon film. After that, the mixture is stirred and matured for 100-110 min.

[0008] S2. Control the temperature of the mixed slurry to 58-62℃, and continuously add zirconate solution over 200-220 min while stirring. At the same time, control the pH of the mixed slurry to 9.3-9.5 with alkaline solution to complete the deposition of dense zirconium film. The amount of zirconate solution added is 0.6-0.7% of the mass of TiO2 based on ZrO2. Then stir and mature for 60 min.

[0009] S3. Continue to adjust and control the temperature of the mixed slurry to 60-67℃, and continuously add aluminate solution over 90-110 minutes while stirring. The amount of aluminate solution added is 2.0-2.5% of the mass of TiO2 based on Al2O3. At the same time, control the pH value of the mixed slurry to 8.9-9.5 with inorganic acid solution, which is added countercurrently. Then stir and mature for 50 minutes.

[0010] S4. Continue to adjust and control the temperature of the mixed slurry to 48-55℃, and continuously add aluminate solution while stirring for 45-60 minutes. The amount of aluminate solution added is 1.2-1.5% of the mass of TiO2 based on Al2O3. At the same time, control the pH value of the mixed slurry to 7.2-7.8 with aluminum sulfate solution. The aluminum sulfate solution is added in a co-current manner, and then stirred and matured for 50 minutes.

[0011] S5. Adjust the final pH value of the mixed slurry to 7.0-7.2, and continue stirring and maturing for 90-100 minutes. Then, after homogenization, filtration, washing, dehydration, drying, pulverization and organic treatment, multi-component composite coated titanium dioxide is obtained.

[0012] By adopting the above technical solution, this application optimizes various parameters of the coating process according to the slurry state, pH adjustment rate, temperature, and stirring and dispersion conditions of different coating processes, realizing the composite superposition of multi-element silicon film, zirconium film, and aluminum film. A dense silicon oxide film layer, a dense zirconium oxide film layer, and a dense and loose aluminum oxide film layer are formed on the surface of the primary titanium dioxide. While maintaining the excellent optical performance indicators of the primary titanium dioxide, the weather resistance of titanium dioxide is greatly improved, meeting the development needs of coatings in high weather resistance and emerging environmentally friendly fields such as shipbuilding, bridges, solar energy, and wind power.

[0013] The high density of the silicon film obtained by depositing it in two stages with different pH ranges significantly increases the weather resistance of titanium dioxide. Coating its surface with a dense zirconium oxide film further enhances its gloss and lightfastness, and further strengthens its weather resistance. Coating with two layers of alumina film of different morphologies further improves the gloss, system dispersion stability, and promotes the overall stability of the titanium dioxide's weather resistance, facilitating subsequent filtration and washing. Based on common knowledge and existing technology, those skilled in the art can conventionally reverse the order of the silicon and zirconium films, i.e., first coating with a dense zirconium film, then with two dense silicon films, and finally with two aluminum films. This application, by employing the above three coating materials and designing an optimized combination of film layers, effectively blocks titanium dioxide lattice defects, achieving a shielding effect through multi-layer material superposition. This not only improves its optical performance but also gives the final titanium dioxide product high weather resistance and anti-chalking properties.

[0014] Specifically, before coating, the stirring speed is adjusted to 60-70 r / min, and the titanium dioxide slurry is well dispersed in the pH range of 9.0-11.0 with alkaline solution. Deionized water is added to reduce the mass concentration of the titanium dioxide slurry to 22-25%, which is beneficial to reduce the coating rate. After stirring and dispersing for 30-40 min, the titanium dioxide slurry is heated to 65-75℃.

[0015] Furthermore, this application adjusts the stirrer speed to 65-70 r / min, adjusts the pH value of the titanium dioxide slurry to 10.5-11.0, and heats the titanium dioxide slurry to 68-72℃ to fully disperse the titanium dioxide particles. At the same time, the titanium dioxide mass concentration is controlled to be 22-23%, as a lower concentration is beneficial to improving the density of the subsequent silicon film coating.

[0016] In the silicon film coating step of this application, the silicate solution used is a sodium silicate solution with a concentration of 150-180 g / L (based on SiO2). Further, the concentration of the sodium silicate solution is 170 g / L (based on SiO2). In this application, the sodium silicate solution is added to the titanium dioxide slurry in a single, rapid step and dispersed thoroughly for 30-40 minutes to facilitate the subsequent coating of a dense silicon oxide film. Further, in this application, the sodium silicate solution is added to the titanium dioxide slurry at an amount equal to 3.6% of the mass of TiO2 (based on SiO2).

[0017] Higher temperatures are more conducive to the formation of a dense film. However, considering overall energy consumption and coating effect, this application further controls the temperature of the mixed slurry to 74°C, and performs dense silicon film deposition by adjusting the pH value in two stages using an inorganic acid solution at a rotation speed of 50-55 r / min. The inorganic acid solution used is hydrochloric acid with a mass concentration of 9-11%. Furthermore, this application adjusts the rotation speed to 55 r / min.

[0018] In the zirconium coating step of this application, the zirconate solution used is zirconium sulfate solution with a concentration of 165-175 g / L (based on ZrO2). In this application, the zirconate solution is slowly and uniformly added to the mixed slurry over a certain period of time at a rotation speed of 60-65 r / min; a longer deposition time is more conducive to the formation of a dense zirconium film. Further, this application adjusts the rotation speed to 65 r / min, controls the temperature of the mixed slurry at 60℃, sets the deposition time to 210 min, and the amount of zirconate solution added is 0.62% of the mass of TiO2 (based on ZrO2).

[0019] In the aluminum coating step of this application, because the zirconium oxide film is deposited first and then the alumina film is deposited, a false thickening phenomenon occurs in the slurry during the alumina film deposition, leading to particle agglomeration. Therefore, this application adjusts the stirrer speed to 55-65 r / min, preferably 60-65 r / min, to enhance the stirring ability and improve particle dispersibility. Under the above stirring conditions, this application slowly and uniformly adds an aluminate solution to the mixed slurry over a certain period of time. The aluminate solution used is sodium aluminate solution with a concentration of 145-170 g / L based on Al2O3. Further, a sodium aluminate solution with a concentration of 150-170 g / L based on Al2O3 is selected. In this step, the inorganic acid solution is a sulfuric acid solution with a mass concentration of 10%. This application adds the sulfuric acid solution to the mixed slurry in a countercurrent manner (i.e., in the opposite direction to the stirring direction of the mixed slurry), which can form a denser alumina film. Furthermore, this application controls the temperature of the mixed slurry to be 63-67℃, the deposition time to be 105-110 min, and the amount of sodium aluminate solution added to account for 2.2-2.3% of the mass of TiO2 based on Al2O3.

[0020] To further improve the overall structural stability of the product and facilitate subsequent processing and applications of titanium dioxide, such as graft modification, this application also deposits a relatively loose alumina film on the dense alumina film. The rotation speed is adjusted to 50-58 r / min, and a sodium aluminate solution with a concentration of 175-200 g / L (Al₂O₃) is rapidly and uniformly added within a short time. Specifically, a sodium aluminate solution with a concentration of 180-185 g / L (Al₂O₃) is selected. In this step, aluminum sulfate solution is added co-currently to adjust the pH value in order to complete the deposition of the loose alumina film. Furthermore, in this application, the rotation speed is adjusted to 52-58 r / min, the temperature of the mixed slurry is controlled to 48-54℃, the deposition time is 45-55 min, the amount of sodium aluminate solution added is 1.35-1.5% of the mass of TiO2 based on Al2O3, and the pH value is adjusted to 7.2-7.3 using aluminum sulfate solution.

[0021] Preferably, in step S1, the method for preparing the titanium dioxide slurry includes the following steps:

[0022] The primary titanium dioxide is pulped with demineralized water to obtain a slurry with a titanium dioxide mass concentration of 33-35%. The pH of the slurry is then adjusted to 9.5, followed by the addition of a dispersant and stirring. After that, the slurry is first screened to remove hard particles larger than 45μm, then ground, and finally subjected to hydrocyclone classification to remove large particles larger than 5μm, thus obtaining the titanium dioxide slurry.

[0023] By adopting the above technical solution, this application prepares the primary titanium dioxide by desalination and dispersing it with a dispersant. Then, it is sequentially subjected to a combination of sieving by a vibrating screen, grinding by a sand mill, and diversion by a hydrocyclone classifier. This process maximizes the grinding and breaks up the agglomerates, removes large particles, and gives the primary titanium dioxide a good foundation for optical performance indicators.

[0024] Preferably, the CBU index of the primary titanium dioxide is 11-13.

[0025] Through the above technical solution, this application controls the CBU index (CBU is carbon black base color, which represents a comprehensive index of titanium dioxide particle characteristics) of the primary titanium dioxide, enabling the final titanium dioxide to possess the neutral hue index basis required for high hiding power. The primary titanium dioxide in this application is prepared by the chloride process, and because the rutile titanium dioxide produced by the chloride process has better optical properties, it is used as the base raw material.

[0026] Optionally, the dispersant is one of sodium silicate, sodium hexametaphosphate, citric acid, and sorbic acid.

[0027] Citric acid is selected as the dispersant in this application. The amount added is 0.3-0.35% of the TiO2 mass fraction in the slurry. The mixture is stirred thoroughly for 30-35 minutes.

[0028] Preferably, the screening process is as follows: passing through a 100-mesh sieve, a 200-mesh sieve, and a 325-mesh sieve in sequence.

[0029] Through the above technical solution, this application uses a combination vibrating screen of 100 mesh / 200 mesh / 325 mesh to first separate larger hard particles larger than 45μm, effectively removing relatively large hard particles generated by the sintering of a small amount of titanium dioxide material due to the high temperature during the oxidation reaction in the chlorination process. Furthermore, this application uses a combination of screens of different specifications, which can adapt to the characteristics of the titanium dioxide slurry and reduce the possibility of screen clogging in actual production.

[0030] Preferably, in step S5, a green organic treatment agent is added during pulverization for organic treatment, and the amount of the green organic treatment agent added is 0.25-0.6% of the carbon content in the dried product.

[0031] Optionally, the green organic treatment agent is an amphiphilic polyol and / or an organosilicon dispersant.

[0032] Optionally, the green organic treatment agent is one or more of trimethylolethane, ethylene glycol, dimethyl silicone oil, titanate coupling agent, and dimethylolpropionic acid.

[0033] Preferably, the green organic treatment agent is a mixture of trimethylolpropane and dimethylolpropionic acid.

[0034] Through the above technical solution, this application adds an amphiphilic green organic treatment agent to the high-temperature and high-pressure steam pulverization process to form a green organic composite coating, which can enhance the compatibility and dispersibility of titanium dioxide in water-based and oil-based coatings, thereby enabling titanium dioxide to fully exert its pigment function and improve the weather resistance and anti-chalking performance of coating products.

[0035] The amphiphilic green organic treatment agent of this application is added at the outlet of the gas-jet mill by continuous quantitative gas atomization and simultaneously with the ground material, which can ensure that the green organic treatment agent is evenly and stably distributed on the surface of titanium dioxide.

[0036] This application further selects a mixture of trimethylolethane and dimethylolpropionic acid, which can further improve the dispersibility of titanium dioxide and enhance its gloss.

[0037] Secondly, this application provides a multi-component composite coated titanium dioxide prepared by the above preparation method.

[0038] In summary, this application has the following beneficial technical effects:

[0039] This application employs three coating materials—silicon, zirconium, and aluminum—and designs a coating layer combination. Based on the slurry state, pH adjustment rate, temperature, and stirring / dispersion conditions of different coating processes, various parameters of the coating process are optimized. This results in titanium dioxide produced with a surface coating of a dense silicon oxide film, a dense zirconium oxide film, and a combination of dense and porous alumina film. Compared to existing binary composite coatings and general-purpose titanium dioxide products with medium to low coating amounts, the titanium dioxide produced in this application exhibits significant improvements in optical performance and weather resistance, meeting the development needs of coatings in high-weather-resistant and emerging environmentally friendly fields such as shipbuilding, bridges, solar energy, and wind power.

[0040] This application controls the CBU index of primary titanium dioxide, and after primary titanium dioxide that meets the CBU index requirements is slurried with demineralized water and dispersed with a dispersant, it is then sequentially sieved by a combination of vibrating screen, ground by a sand mill, and divided by a hydrocyclone classifier to maximize grinding and open up agglomerates, remove large particles, and improve the basic optical performance index of primary titanium dioxide.

[0041] This application involves adding an amphiphilic green organic treatment agent during high-temperature and high-pressure steam pulverization to create a green organic composite coating, which enhances the compatibility and dispersibility of titanium dioxide in water-based and oil-based coatings. This allows titanium dioxide to fully exert its pigment function and improves the weather resistance and anti-chalking properties of coating products. Detailed Implementation

[0042] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0043] Except for primary titanium dioxide, all raw materials used in this application are commercially available products.

[0044] The primary titanium dioxide in this application is a semi-finished rutile titanium dioxide produced by the chloride process. Its preparation method is a conventional process in the field. Since the purpose of this application is to perform coating modification post-treatment on the primary titanium dioxide, the preparation method of the primary titanium dioxide will not be described in detail in this application.

[0045] Example 1.1

[0046] A method for preparing multi-component composite coated titanium dioxide includes the following steps:

[0047] S11. Add demineralized water to 500 kg of primary titanium dioxide with a CBU index of 12 and stir and disperse for 30 min to obtain a slurry with a titanium dioxide mass concentration of 33%. Then, adjust the pH of the slurry to 9.5 with a sodium hydroxide solution with a mass concentration of 20%. Add citric acid with a TiO2 mass fraction of 0.35% and stir and disperse for 30 min. Then, pass the slurry through a combination of 100 mesh / 200 mesh / 325 mesh vibrating screen, a sand mill, and a hydrocyclone classifier to obtain the primary titanium dioxide slurry.

[0048] S12. Add the initial titanium dioxide slurry to the coating tank, adjust the stirrer speed to 60 r / min, adjust the pH value to 9.0 with a 20% sodium hydroxide solution, and add demineralized water to make the titanium dioxide slurry concentration 25%. After fully dispersing for 30 min, heat the titanium dioxide slurry to 65℃.

[0049] S13. Add a sodium silicate solution with a concentration of 150 g / L (SiO2) and a mass of 3.5% (SiO2) of TiO2 to the titanium dioxide slurry. After stirring and dispersing for 30 min, a mixed slurry is obtained. Then, control the temperature of the mixed slurry at 76℃ and adjust the rotation speed to 50 r / min. First, adjust and control the pH value of the mixed slurry to 8.8 with a 9% (mass concentration) hydrochloric acid solution over 180 min to complete the deposition of the first dense silicon film. Then, adjust and control the pH value of the mixed slurry to 7.8 with a 9% (mass concentration) hydrochloric acid solution over 90 min to complete the deposition of the second dense silicon film. Finally, stir and mature for 100 min.

[0050] S2. Continue to control the temperature of the mixed slurry at 58℃, adjust the rotation speed to 60r / min, and continuously and uniformly add zirconium sulfate solution with a concentration of 165g / L (based on ZrO2) and a mass of 0.6% (based on the mass of TiO2) of ZrO2 within 200min. At the same time, use a 20% sodium hydroxide solution to control the pH value of the mixed slurry to 9.3 to complete the coating of dense zirconium film. Then stir and mature for 60min.

[0051] S3. Continue to control the temperature of the mixed slurry at 65℃ and adjust the rotation speed to 55r / min. Continuously and uniformly add sodium aluminate solution with a concentration of 145g / L (calculated as Al2O3) and a mass of 2.0% (calculated as Al2O3) of TiO2 within 90min. When the pH value of the mixed slurry reaches 9.2, simultaneously add sulfuric acid solution with a mass concentration of 10% in a countercurrent manner to control the pH value of the mixed slurry at 9.3, thus completing the coating of the dense aluminum film. Then stir and mature for 50min.

[0052] S4. Continue to control the temperature of the mixed slurry at 50℃, adjust the rotation speed to 55r / min, and continuously and uniformly add sodium aluminate solution with a concentration of 175g / L based on Al2O3 and a mass of 1.3% based on the mass of TiO2 based on Al2O3 within 50min. At the same time, add aluminum sulfate solution with a concentration of 100g / L based on Al2O3 in a co-current manner, control the pH value of the mixed slurry to 7.5, complete the coating of loose aluminum film, and then stir and mature for 50min.

[0053] S5. Adjust the final pH value of the mixed slurry to 7.0, and continue stirring and maturing for 90 minutes. Then, after homogenization, filtration, washing, dehydration, drying, and pulverization, at the discharge port of the gas pulverizer, trimethylolethane and dimethylolpropionic acid in a volume ratio of 1:1 are continuously and quantitatively added to the ground material through gas atomization to form a green organic composite coating. The total amount of trimethylolethane and dimethylolpropionic acid added is 0.6% of the carbon content in the dried product, thus obtaining multi-component composite coated titanium dioxide.

[0054] Example 1.2

[0055] A method for preparing multi-component composite coated titanium dioxide includes the following steps:

[0056] S11. Add demineralized water to 500 kg of primary titanium dioxide with a CBU index of 11.5 and stir and disperse for 30 min to obtain a slurry with a titanium dioxide mass concentration of 35%. Then adjust the pH of the slurry to 9.5 with a sodium hydroxide solution with a mass concentration of 20%. Add citric acid with a TiO2 mass fraction of 0.3% and stir and disperse for 35 min. Then pass it through a 100 mesh / 200 mesh / 325 mesh combined vibrating screen for sieving, a sand mill for grinding, and a hydrocyclone classifier for separation to obtain the primary titanium dioxide slurry.

[0057] S12. Add the initial titanium dioxide slurry to the coating tank, adjust the stirrer speed to 65 r / min, adjust the pH value to 10.5 with a 20% sodium hydroxide solution, and add demineralized water to make the titanium dioxide slurry concentration 23%. After fully dispersing for 40 min, heat the titanium dioxide slurry to 75℃.

[0058] S13. Add a sodium silicate solution with a concentration of 180 g / L (SiO2) and a mass of 3.8% (SiO2) of TiO2 to the titanium dioxide slurry. After stirring and dispersing for 40 min, a mixed slurry is obtained. Then, control the temperature of the mixed slurry at 78℃ and adjust the rotation speed to 55 r / min. Within 200 min, slowly and uniformly adjust and control the pH value of the mixed slurry to 9.0 with a 10% (mass concentration) hydrochloric acid solution to complete the deposition of the first dense silicon film. Then, within 100 min, slowly and uniformly adjust and control the pH value of the mixed slurry to 7.5 with a 10% (mass concentration) hydrochloric acid solution to complete the deposition of the second dense silicon film. After that, stir and mature for 110 min.

[0059] S2. Continue to control the temperature of the mixed slurry at 62℃, adjust the rotation speed to 65r / min, and continuously and uniformly add zirconium sulfate solution with a concentration of 175g / L (based on ZrO2) and a mass of 0.7% (based on the mass of TiO2) of ZrO2 within 220min. At the same time, use a 20% sodium hydroxide solution to control the pH value of the mixed slurry to 9.5 to complete the coating of dense zirconium film. Then stir and mature for 60min.

[0060] S3. Continue to control the temperature of the mixed slurry at 60℃ and adjust the rotation speed to 65r / min. Continuously and uniformly add sodium aluminate solution with a concentration of 160g / L (calculated as Al2O3) and a mass of 2.5% (calculated as Al2O3) of TiO2 within 110min. When the pH value of the mixed slurry reaches 9.4, simultaneously add sulfuric acid solution with a mass concentration of 10% by countercurrent to control the pH value of the mixed slurry to 9.5, thus completing the coating of the dense aluminum film. Then stir and mature for 50min.

[0061] S4. Continue to control the temperature of the mixed slurry at 55℃, adjust the rotation speed to 50r / min, and continuously and uniformly add sodium aluminate solution with a concentration of 200g / L based on Al2O3 and a mass of 1.2% based on the mass of TiO2 based on Al2O3 within 60min. At the same time, add aluminum sulfate solution with a concentration of 100g / L based on Al2O3 in a co-current manner, control the pH value of the mixed slurry to 7.8, complete the coating of loose aluminum film, and then stir and mature for 50min.

[0062] S5. Adjust the final pH value of the mixed slurry to 7.2, and continue stirring and maturing for 100 minutes. Then, after homogenization, filtration, washing, dehydration, drying, and pulverization, at the discharge port of the gas pulverizer, trimethylolethane and dimethylolpropionic acid in a volume ratio of 1:1 are continuously and quantitatively added to the ground material through gas atomization to form a green organic composite coating. The total amount of trimethylolethane and dimethylolpropionic acid added is 0.25% of the carbon content in the dried product, thus obtaining multi-component composite coated titanium dioxide.

[0063] Example 2.1

[0064] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S12, the stirrer speed is adjusted to 70 r / min, the pH value is adjusted to 10.5 with a 20% sodium hydroxide solution, and demineralized water is added to make the titanium dioxide slurry concentration 22%. After being fully dispersed for 40 min, the titanium dioxide slurry is heated to 68°C. The rest is the same as in Example 1.1.

[0065] Example 2.2

[0066] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S12, the stirrer speed is adjusted to 65 r / min, the pH value is adjusted to 11.0 with a 20% sodium hydroxide solution, and demineralized water is added to make the titanium dioxide slurry concentration 23%. After being fully dispersed for 35 min, the titanium dioxide slurry is heated to 72°C. The rest is the same as in Example 1.1.

[0067] Example 3.1

[0068] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S13, a sodium silicate solution with a concentration of 170 g / L (based on SiO2) and a mass of 3.6% (based on the mass of TiO2) is added to the titanium dioxide slurry. After stirring and dispersing for 40 min, a mixed slurry is obtained. Then, the temperature of the mixed slurry is controlled at 74 °C, and the rotation speed is adjusted to 55 r / min. The pH value of the mixed slurry is adjusted and controlled to 8.8 by slowly and uniformly using an 11% hydrochloric acid solution within 190 min to complete the deposition of the first dense silicon film. The rest is the same as in Example 1.1.

[0069] Example 4.1

[0070] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S2, the temperature of the mixed slurry is controlled at 60°C, the rotation speed is adjusted to 65 r / min, and a zirconium sulfate solution with a concentration of 175 g / L (calculated as ZrO2) and a mass of 0.62% (calculated as ZrO2) of TiO2 is continuously and uniformly added within 210 min. The rest is the same as in Example 1.1.

[0071] Example 5.1

[0072] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S3, the temperature of the mixed slurry is controlled at 63°C, the rotation speed is adjusted to 65 r / min, and a sodium aluminate solution with a concentration of 150 g / L (calculated as Al2O3) and a mass of 2.2% (calculated as Al2O3) of TiO2 is continuously and uniformly added within 110 min. When the pH value of the mixed slurry reaches 9.3, a sulfuric acid solution with a mass concentration of 10% is slowly added in a countercurrent manner to control the pH value of the mixed slurry to 9.1. The rest is the same as in Example 1.1.

[0073] Example 5.2

[0074] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S3, the temperature of the mixed slurry is controlled at 67°C, the rotation speed is adjusted to 60 r / min, and a sodium aluminate solution with a concentration of 170 g / L (calculated as Al2O3) and a mass of 2.3% (calculated as Al2O3) of TiO2 is continuously and uniformly added within 105 min. When the pH value of the mixed slurry reaches 8.9, a sulfuric acid solution with a mass concentration of 10% is slowly added in a countercurrent manner to control the pH value of the mixed slurry to 9.5. The rest is the same as in Example 1.1.

[0075] Example 6.1

[0076] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S4, the temperature of the mixed slurry is controlled at 48°C, the rotation speed is adjusted to 58 r / min, and a sodium aluminate solution with a concentration of 180 g / L (calculated as Al2O3) and a mass of 1.5% (calculated as Al2O3) of TiO2 is continuously and uniformly added within 55 min. At the same time, an aluminum sulfate solution with a concentration of 100 g / L (calculated as Al2O3) is added in a co-current manner. The pH value of the mixed slurry is controlled at 7.3. All other aspects are the same as in Example 1.1.

[0077] Example 6.2

[0078] A method for preparing multi-component composite coated titanium dioxide differs from Example 1.1 in that: in step S4, the temperature of the mixed slurry is controlled at 54°C, the rotation speed is adjusted to 52 r / min, and an aluminate solution with a concentration of 185 g / L (calculated as Al2O3) and a mass of 1.35% (calculated as Al2O3) of TiO2 is continuously and uniformly added within 45 min. At the same time, an aluminum sulfate solution with a concentration of 100 g / L (calculated as Al2O3) is added in a co-current manner. The pH value of the mixed slurry is controlled at 7.2. All other aspects are the same as in Example 1.1.

[0079] Comparative Example 1

[0080] The preparation method of zirconium-aluminum composite coated titanium dioxide includes the following steps:

[0081] a. Add demineralized water to 500 kg of primary titanium dioxide and stir and disperse for 30 min to obtain a slurry with a titanium dioxide mass concentration of 28%. Then adjust the pH of the slurry to 9.5 with a sodium hydroxide solution with a mass concentration of 20%. Add sodium hexametaphosphate with a TiO2 mass fraction of 0.3% and stir and disperse for 30 min. Then grind the slurry in a sand mill to obtain titanium dioxide slurry.

[0082] b. Add the titanium dioxide slurry to the coating tank, adjust the stirrer speed to 60 r / min, adjust the pH value to 9.0 with a 20% sodium hydroxide solution, and add demineralized water to make the titanium dioxide slurry concentration 26%. After dispersing for 30 min, heat the titanium dioxide slurry to 60℃.

[0083] c. A zirconium sulfate solution with a concentration of 165 g / L (based on ZrO2) and a mass of 0.45% (based on ZrO2) of TiO2 mass is continuously and uniformly added over 120 min. At the same time, a 20% sodium hydroxide solution is used to control the pH of the mixed slurry to 8.6 ± 0.4. The mixture is then stirred and matured for 60 min.

[0084] d. Continue to control the temperature of the mixed slurry at 55℃, adjust the rotation speed to 55r / min, and continuously and uniformly add sodium aluminate solution with a concentration of 145g / L based on Al2O3 and a mass of 1.8% based on the mass of TiO2 based on Al2O3 within 70min. At the same time, slowly add aluminum sulfate solution with a mass concentration of 105g / L based on the mass of Al2O3 in a co-current manner. Control the pH value of the mixed slurry to 7±0.2, and then stir and mature for 30min.

[0085] e. Adjust the final pH value of the mixed slurry to 7.0, and continue stirring and maturing for 100 minutes. Then, after homogenization, filtration, washing, dehydration, drying, and pulverization, trimethylolpropane is continuously and quantitatively added to the material at the feed inlet of the gas pulverizer using a pump. The amount of trimethylolpropane added is 0.35% of the carbon content in the dried product, thus obtaining zirconium aluminum composite coated titanium dioxide.

[0086] Comparative Example 2

[0087] The preparation method of silicon-aluminum composite coated titanium dioxide includes the following steps:

[0088] I. Add demineralized water to 500 kg of nascent titanium dioxide and stir and disperse for 30 min to obtain a slurry with a titanium dioxide mass concentration of 30%. Then, adjust the pH of the slurry to 9.8 with a sodium hydroxide solution with a mass concentration of 20%. Add sodium silicate with a TiO2 mass fraction of 0.4% and stir and disperse for 30 min. Then, grind the slurry in a sand mill to obtain titanium dioxide slurry.

[0089] II. Add the titanium dioxide slurry to the coating tank, adjust the stirrer speed to 60 r / min, adjust the pH value to 10.5 with a 20% sodium hydroxide solution, and add demineralized water to make the titanium dioxide slurry concentration 25%. After fully dispersing for 30 min, add a sodium silicate solution with a concentration of 180 g / L (based on SiO2) and a mass of 2.5% (based on the mass of TiO2) to the titanium dioxide slurry in one go. Stir and disperse for 50 min to obtain a mixed slurry. Then control the temperature of the mixed slurry at 65℃, adjust the stirring speed to 40 r / min, and slowly and uniformly adjust and control the pH value of the mixed slurry to 8.8±0.2 with a 15% sulfuric acid solution over 150 min. Stir and mature for 40 min.

[0090] III. Continue to control the temperature of the mixed slurry at 55℃ and adjust the rotation speed to 55r / min. Within 50min, continuously and uniformly add sodium aluminate solution with a concentration of 165g / L based on Al2O3 and a mass of 1.5% based on the mass of TiO2 based on Al2O3. At the same time, slowly add aluminum sulfate solution with a mass concentration of 100g / L based on the mass of Al2O3 in a co-current manner. Adjust and control the pH value of the mixed slurry to 7±0.1, and then stir and mature for 40min.

[0091] IV. Adjust the final pH value of the mixed slurry to 7.0, and continue stirring and maturing for 120 minutes. Then, it is homogenized, filtered, washed, dehydrated, dried, and pulverized. During pulverization, trimethylolpropane is continuously and quantitatively added to the material at the feed inlet of the gas pulverizer using a pump. The amount of trimethylolpropane added is 0.3% of the carbon content in the dried product, thus obtaining silicon-aluminum composite coated titanium dioxide.

[0092] Comparative Example 3

[0093] The preparation method of silicon-aluminum composite coated titanium dioxide includes the following steps:

[0094] I. Add demineralized water to 500 kg of nascent titanium dioxide and stir and disperse for 30 min to obtain a slurry with a titanium dioxide mass concentration of 31%. Then, adjust the pH of the slurry to 9.8 with a sodium hydroxide solution with a mass concentration of 20%. Add sodium silicate with a TiO2 mass fraction of 0.4% and stir and disperse for 30 min. Then, grind the slurry in a sand mill to obtain titanium dioxide slurry.

[0095] II. Add the titanium dioxide slurry to the coating tank, adjust the stirrer speed to 60 r / min, adjust the pH value to 10.5 with a 20% sodium hydroxide solution, and add demineralized water to make the titanium dioxide slurry concentration 25%. After fully dispersing for 30 min, add a sodium silicate solution with a concentration of 180 g / L (based on SiO2) and a mass of 2.6% (based on the mass of TiO2) to the titanium dioxide slurry in one go. Stir and disperse for 50 min to obtain a mixed slurry. Then control the temperature of the mixed slurry at 65℃, adjust the stirring speed to 50 r / min, and slowly and uniformly adjust and control the pH value of the mixed slurry to 8.8±0.2 with a 15% sulfuric acid solution over 150 min. Stir and mature for 40 min.

[0096] III. Continue to control the temperature of the mixed slurry at 55℃, adjust the rotation speed to 50r / min, and continuously and uniformly add sodium aluminate solution with a concentration of 175g / L (calculated as Al2O3) and a mass of 3.2% (calculated as Al2O3) of TiO2 within 55min. At the same time, slowly add sulfuric acid solution with a mass concentration of 15% in a co-current manner, adjust and control the pH value of the mixed slurry to 7±0.1, and then stir and mature for 50min.

[0097] IV. Adjust the final pH value of the mixed slurry to 7.0, and continue stirring and maturing for 120 minutes. Then, it is homogenized, filtered, washed, dehydrated, dried, and pulverized. During pulverization, trimethylolpropane is continuously and quantitatively added to the material at the feed inlet of the gas pulverizer using a pump. The amount of trimethylolpropane added is 0.4% of the carbon content in the dried product, thus obtaining silicon-aluminum composite coated titanium dioxide.

[0098] Performance testing

[0099] 1. The titanium dioxide prepared in the above examples and comparative examples was directly tested for weather resistance using the acid dissolution method. The principle is to directly dissolve the titanium dioxide with concentrated sulfuric acid using a chemical method, and then calculate the coating rate and density of the product based on the amount of dissolved titanium dioxide. A smaller value indicates higher weather resistance.

[0100] 2. Add 22% of the total weight of all components in the waterborne two-component polyurethane formulation to the titanium dioxide prepared in the above examples and comparative examples. Stir and disperse the mixture at a speed of 1500 r / min to form a slurry. Except for the source of titanium dioxide, the conditions are the same for each experimental group. Then, the mixture is coated on a black and white plate and dried. The optical properties are then measured by a spectrophotometer.

[0101] 3. Add 22% of the total weight of all components in the waterborne two-component polyurethane formulation to the titanium dioxide prepared in the above examples and comparative examples. Stir and disperse the mixture at a speed of 1500 r / min to form a slurry. Except for the source of titanium dioxide, all other conditions are the same for each experimental group. Then, spray the film onto the tinplate and dry it. After irradiating it with a UV lamp for 1200 h, test the gloss change value of the sample before and after irradiation at 60° and calculate the gloss loss rate. The smaller the gloss loss rate, the higher the weather resistance performance.

[0102] The waterborne two-component polyurethane formulation system is as follows: 10% deionized water, 1.85% dispersant 490, 0.15% curing agent BYK-024, 22% titanium dioxide, 60% hydroxyacrylic acid emulsion AH233, and 6% other additives;

[0103] The performance test results are shown in Table 1.

[0104] Table 1 Performance Test Results

[0105] Item Brightness (%) Hue (b) Whiteness (WI) Dispersion (μm) Relative Opacity (%) Gloss Loss (%) Acid Solubility Example 1. 196.56 0.77 95.50 1595.77 6.5 0.35 Example 1. 296.59 0.78 95.52 1495.75 6.4 0.34 Example 2. 196.58 0.78 95.51 1695.79 6.3 0.32 Example 2. 296.57 0.78 95.51 1395.85 6.3 0.33 Example 3. 196.61 0.79 95.55 1495.82 6.3 0.31 Example 4. 196.62 0.80 95.57 1595. 796.10.32 Example 5.196.610.7995.561595.866.20.33 Example 5.296.620.7995.551695.876.10.32 Example 6.196.590.7895.531495.906.30.33 Example 6.296.580.7795.541595.926.20.32 Comparative Example 196.350.7695.362294.38381.52 Comparative Example 296.320.7595.332194.29311.47 Comparative Example 396.360.7695.382394.33351.62

[0106] Data Analysis:

[0107] As shown in Table 1, the titanium dioxide prepared in Examples 1.1-6.2 of this application exhibits superior performance in key pigment optical properties such as brightness, hue, whiteness, dispersibility, and hiding power compared to Comparative Examples 1-3 in water-based two-component polyurethane formulations. Furthermore, the differences between Examples 1.1-6.2 are relatively small, indicating relative stability. The titanium dioxide also shows lower gloss loss and acid solubility values ​​compared to Comparative Examples 1-3. This demonstrates that the titanium dioxide prepared in this application exhibits significant improvements in weather resistance and anti-chalking properties, and the process is mature and stable, meeting the development needs of coatings in high-weather-resistant and emerging environmentally friendly fields such as shipbuilding, bridges, solar energy, and wind power.

[0108] The difference between Examples 3.1-6.2 and Example 1.1 lies in the further variation of the process parameters of each step in the coating process. As can be seen from Table 1, the weather resistance and anti-chalking properties of the titanium dioxide prepared in Examples 3.1-6.2 are slightly higher than those in Example 1.1, and the indicators are stable. This shows that even with the further variation of the process parameters of each step in the coating process, Examples 3.1-6.2 can still guarantee the weather resistance and anti-chalking properties of the titanium dioxide.

[0109] The existing processes of Comparative Examples 1-3 differ from those of Example 1.1 in the following ways: First, the particle size range of the initial titanium dioxide product was not selected, affecting the product's hiding power index; second, conventional zirconium and aluminum films were used, affecting the weather resistance index; third, conventional silicon and aluminum films were used, affecting the gloss loss rate and weather resistance index; and fourth, conventional trimethylolpropane was used for organic treatment, affecting the dispersibility index. As shown in Table 1, the hiding power, dispersibility, gloss loss rate, and acid solubility values ​​of Comparative Examples 1-3 are significantly lower than those of Example 1.1, indicating that the innovative composite multi-element coating formulation obtained in this application can form a dense silicon film, a zirconium film, and a combination of dense and porous aluminum film on the surface of titanium dioxide, achieving the goal of significantly improving the weather resistance and anti-chalking performance of titanium dioxide.

[0110] The embodiments described in this specific implementation are preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a multi-element composite coated titanium dioxide, characterized in that, Includes the following steps: S1. Titanium dioxide slurry and silicate solution are stirred and dispersed to obtain a mixed slurry. The temperature of the titanium dioxide slurry is 65-75℃, the mass concentration is 22-25%, and the pH value is 9.0-11.

0. The amount of silicate solution added is 3.5-3.8% of the mass of TiO2 based on SiO2. Then, the temperature of the mixed slurry is controlled at 74-78℃. While stirring, the pH value of the mixed slurry is first adjusted and controlled to 8.8-9.0 with an inorganic acid solution within 180-200 min to complete the deposition of the first dense silicon film. Then, the pH value of the mixed slurry is adjusted and controlled to 7.5-7.8 with an inorganic acid solution within 90-100 min to complete the deposition of the second dense silicon film. After that, the mixture is stirred and matured for 100-110 min. S2. Control the temperature of the mixed slurry to 58-62℃, and continuously add zirconate solution over 200-220 min while stirring. At the same time, control the pH of the mixed slurry to 9.3-9.5 with alkaline solution to complete the deposition of dense zirconium film. The amount of zirconate solution added is 0.6-0.7% of the mass of TiO2 based on ZrO2. Then stir and mature for 60 min. S3. Continue to adjust and control the temperature of the mixed slurry to 60-67℃, and continuously add aluminate solution over 90-110 minutes while stirring. The amount of aluminate solution added is 2.0-2.5% of the mass of TiO2 based on Al2O3. At the same time, control the pH value of the mixed slurry to 8.9-9.5 with inorganic acid solution, which is added countercurrently. Then stir and mature for 50 minutes. S4. Continue to adjust and control the temperature of the mixed slurry to 48-55℃, and continuously add aluminate solution while stirring for 45-60 minutes. The amount of aluminate solution added is 1.2-1.5% of the mass of TiO2 based on Al2O3. At the same time, control the pH value of the mixed slurry to 7.2-7.8 with aluminum sulfate solution. The aluminum sulfate solution is added in a co-current manner, and then stirred and matured for 50 minutes. S5. Adjust the final pH value of the mixed slurry to 7.0-7.2, and continue stirring and maturing for 90-100 minutes. Then, after homogenization, filtration, washing, dehydration, drying, pulverization and organic treatment, multi-component composite coated titanium dioxide is obtained.

2. The method for preparing a multi-component composite coated titanium dioxide according to claim 1, characterized in that, In step S1, the preparation method of titanium dioxide slurry includes the following steps: The primary titanium dioxide is pulped with demineralized water to obtain a slurry with a titanium dioxide mass concentration of 33-35%. The pH of the slurry is then adjusted to 9.5, followed by the addition of a dispersant and stirring. After that, the slurry is first screened to remove hard particles larger than 45μm, then ground, and finally subjected to hydrocyclone classification to remove large particles larger than 5μm, thus obtaining the titanium dioxide slurry.

3. The method for preparing a multi-component composite coated titanium dioxide according to claim 2, characterized in that, The CBU index of the primary titanium dioxide is 11-13.

4. The method for preparing a multi-component composite coated titanium dioxide according to claim 2, characterized in that, The dispersant is one of sodium silicate, sodium hexametaphosphate, citric acid, and sorbic acid.

5. The method for preparing a multi-component composite coated titanium dioxide according to claim 2, characterized in that, The screening process is as follows: the material passes through a 100-mesh sieve, a 200-mesh sieve, and a 325-mesh sieve in sequence.

6. The method for preparing a multi-component composite coated titanium dioxide according to claim 1, characterized in that, In step S5, a green organic treatment agent is added during pulverization for organic treatment. The amount of the green organic treatment agent added is 0.25-0.6% of the carbon content in the dried product.

7. The method for preparing a multi-component composite coated titanium dioxide according to claim 6, characterized in that, The green organic treatment agent is an amphiphilic polyol and / or an organosilicon dispersant.

8. The method for preparing a multi-component composite coated titanium dioxide according to claim 7, characterized in that, The green organic treatment agent is one or more of the following: trimethylolethane, ethylene glycol, dimethyl silicone oil, titanate coupling agent, and dimethylolpropionic acid.

9. The method for preparing a multi-component composite coated titanium dioxide according to claim 8, characterized in that, The green organic treatment agent is a mixture of trimethylolethane and dimethylolpropionic acid.

10. A multi-component composite coated titanium dioxide prepared by the method of any one of claims 1-9.