Titanium dioxide for high-performance green and environment-friendly coating and preparation method thereof

Abstract

The application discloses a kind of high-performance green environmental protection titanium dioxide for coating and preparation method, the titanium dioxide includes titanium dioxide substrate and the film layer on the surface of the titanium dioxide substrate, the film layer includes zirconium silicon aluminum multi-element hybrid film layer from inside to outside, dense silicon oxide film layer, bayer stone-boehmite-amorphous mixed crystal aluminum oxide doped loose silicon oxide film layer, the active hydroxyl in the film layer includes 0.4~0.7% of the total mass of titanium dioxide mass fraction, the titanium dioxide obtained in the application can avoid the agglomeration between particles without adding any organic auxiliary agent, realize the dispersion of water-oil double system, green environmental protection, and weather resistance is especially excellent, suitable for use in coating.

Description

Technical Field

[0001] This invention belongs to the field of titanium dioxide preparation technology, specifically relating to a high-performance, green, and environmentally friendly titanium dioxide for coatings and its preparation method. Background Technology

[0002] Titanium dioxide is considered one of the best-performing white pigments in the world, widely used in coatings, plastics, papermaking, inks, and many other fields. Titanium dioxide used in coatings accounts for over 60% of the total titanium dioxide content. While titanium dioxide with inorganic surface treatments achieves a certain degree of weather resistance, purely inorganically coated titanium dioxide exhibits very poor dispersion in coating matrices. Traditionally, titanium dioxide used in coatings often employs polyols for organic coating to improve its dispersibility in the matrix. Most titanium dioxide manufacturers use trimethylolpropane (TMP) as an organic surface treatment agent, but the EU classifies TMP as a Group 2 carcinogen, potentially restricting the use of TMP-coated titanium dioxide. Furthermore, TMP carries VOC risks, which may restrict its use in coatings with VOC requirements. Other polyol additives such as neopentyl glycol, 1,4-butanediol, diethylene glycol, and triethylene glycol have inferior temperature resistance and application performance compared to TMP. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a high-performance, green, and environmentally friendly titanium dioxide for coatings and its preparation method.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A high-performance, green, and environmentally friendly titanium dioxide for coatings includes a titanium dioxide substrate and a coating layer on the surface of the titanium dioxide substrate. The coating layer, from the inside out, includes a zirconium-silicon-aluminum hybrid film layer, a dense silicon oxide film layer, and a bayonet-boehmite-amorphous mixed crystal alumina-doped loose silicon oxide film layer.

[0006] The coating layer includes 0.4 to 0.7% active hydroxyl groups by mass fraction of the total mass of titanium dioxide.

[0007] Preferably, in the zirconium-silicon-aluminum hybrid film, the amount of zirconium coating, calculated as zirconium dioxide, is 0.3-0.8% of the mass of the titanium dioxide substrate; the amount of silicon coating, calculated as silicon dioxide, is 1.3-1.8% of the mass of the titanium dioxide substrate; and the amount of aluminum coating, calculated as alumina, is 0.1-1.5% of the mass of the titanium dioxide substrate.

[0008] Preferably, the coating amount of the dense silicon oxide film, measured in silicon dioxide, is 1.0 to 1.5% of the mass of the titanium dioxide substrate.

[0009] Preferably, in the Bayerite-boehmite-amorphous mixed alumina-doped loose silicon oxide film, the amount of aluminum coating, calculated as alumina, is 1.4 to 2.2% of the mass of the titanium dioxide substrate, and the amount of silicon coating, calculated as silicon dioxide, is 0.2 to 0.5% of the mass of the titanium dioxide substrate.

[0010] Preferably, the zirconium-silicon-aluminum multi-element hybrid film is prepared by the following steps:

[0011] Take a titanium dioxide-based material slurry and add an aluminum source, a zirconium source, and a pH adjuster in a co-current flow. Maintain the co-current flow pH at 1.2–1.8 and homogenize. Then add a silicon source and adjust the pH to 8.5–9.5. After homogenization, the zirconium-silicon-aluminum multi-element hybrid film layer is formed.

[0012] Preferably, the coating temperature of the zirconium-silicon-aluminum multi-element hybrid film is 40-55°C, the aluminum source is an acidic aluminum source, the zirconium source is an acidic zirconium source, the aluminum source, the zirconium source and the pH adjuster are added in parallel for 20-40 minutes, and the homogenization time after addition is 20-50 minutes.

[0013] The silicon source is added at a time of 60–80 min, and the homogenization time after addition is 20–30 min.

[0014] Preferably, the dense silicon oxide film is prepared by the following steps:

[0015] A silicon source is added to a titanium dioxide slurry coated with the zirconium-silicon-aluminum multi-element hybrid film at a temperature of 85-95°C, and the pH is adjusted to 9.8-10.2. The silicon source is added for 10-20 minutes, and the slurry is homogenized for 20-30 minutes to form the dense silicon oxide film.

[0016] Preferably, the bayonet-boehmite-amorphous mixed alumina-doped porous silica film is prepared by the following steps:

[0017] A first acidic aluminum source is added to a titanium dioxide slurry coated with the zirconium-silicon-aluminum multi-element hybrid film and the dense silica film at a pH of 9.8–10.2. The pH is adjusted to 6.0–8.0 and homogenized. Then, a second acidic aluminum source, a silicon source, and a pH adjuster are added in parallel, maintaining the pH at 8.5–9.5. The slurry is homogenized and the pH is adjusted to 8.0–8.5. After homogenization, the Bayerite-boehmite-amorphous mixed crystal alumina-doped loose silica film is formed.

[0018] Preferably, the first acidic aluminum source is added at a temperature of 85–95°C for 40–60 min, followed by a homogenization time of 20–30 min; the second acidic aluminum source, silicon source, and pH adjuster are added at a temperature of 65–75°C in parallel flow for 60–80 min, followed by a homogenization time of 20–30 min; then the temperature is raised to 90–95°C to perform the step of adjusting the pH to 8.0–8.5, with the pH adjustment time to 8.0–8.5 being 20–40 min, followed by a homogenization time of 60–80 min.

[0019] The preparation method of the high-performance green and environmentally friendly titanium dioxide for coatings as described above includes the following steps:

[0020] S1. Preparation of titanium dioxide-based material slurry: Take titanium dioxide base material, add dispersant and hydrogen peroxide to prepare titanium dioxide-based material slurry;

[0021] S2. Coating: Take the titanium dioxide-based material slurry and coat it sequentially with a zirconium-silicon-aluminum multi-element hybrid film, a dense silicon oxide film, and a bayonet-boehmite-amorphous mixed crystal alumina-doped loose silicon oxide film.

[0022] S3. Gasification: Take the coated material, dry it, heat treat it at 280-350℃, and then gasify it to obtain titanium dioxide.

[0023] Preferably, the dispersant in step S1 is a combination of sodium hexametaphosphate and sodium citrate, wherein the mass ratio of sodium hexametaphosphate to sodium citrate in the dispersant is (0.5-1.0):1, and the total amount of the dispersant added is 0.15-0.70% of the mass of the titanium dioxide substrate;

[0024] Preferably, the amount of hydrogen peroxide added is 0.5% to 1.2% of the mass of the titanium dioxide substrate.

[0025] Preferably, after adding the dispersant and hydrogen peroxide, step S1 further includes adjusting the pH to 5.0-7.5 and grinding and sieving to ensure that the mass percentage of 0.28-0.34μm particles in the obtained slurry is ≥85%.

[0026] Preferably, the heat treatment time in step S3 is 10 to 15 minutes;

[0027] Preferably, the steam used for the steam powder has a temperature of 320–480°C and a pressure of 2.6–3.4 MPa.

[0028] Preferably, the preparation method of the high-performance green and environmentally friendly titanium dioxide for coatings as described above includes the following steps:

[0029] S1. Take the titanium dioxide substrate dry powder, dispersant and hydrogen peroxide from the chlorination oxidation section, add them to water to form a slurry with a concentration of 500-750 g / L;

[0030] S2. Adjust the pH to 5.0–7.5, then homogenize for 60–90 minutes;

[0031] S3. Grind and pass through a sieve of ≥800 mesh to ensure that the mass percentage of 0.28-0.34μm particles in the slurry is ≥85%, and then dilute to a concentration of 250-380g / L;

[0032] S4. Heat to 40-55℃, add acidic aluminum source, acidic zirconium source and acidic pH adjuster in parallel flow, maintain the pH of the parallel flow at 1.2-1.8, add in parallel flow for 20-40 min, and then homogenize for 20-50 min;

[0033] S5. Add a silicon source and adjust the pH to 8.5–9.5. The silicon source is added over a period of 60–80 minutes, and then homogenized for 20–30 minutes.

[0034] S6. Heat to 85-95℃, add silicon source, adjust pH to 9.8-10.2, the silicon source is added over 10-20 min, and then homogenize for 20-30 min;

[0035] S7. Add an acidic aluminum source and adjust the pH to 6.0–8.0. The acidic aluminum source is added over a period of 40–60 min, and then homogenized for 20–30 min.

[0036] S8. Cool to 65-75℃, add acidic aluminum source, silicon source and alkaline pH adjuster in parallel flow, maintain the pH of parallel flow at 8.5-9.5, add in parallel flow for 60-80 min, and then homogenize for 20-30 min;

[0037] S9. Heat to 90-95℃, adjust the pH to 8.0-8.5 using an acidic pH adjuster, add the acidic pH adjuster for 20-40 minutes, and then homogenize for 60-80 minutes;

[0038] S10. The slurry from step S9 is subjected to pressure filtration and washing to obtain filter cake;

[0039] S11. The filter cake is dried and then subjected to heat treatment at a temperature of 280-350°C for 10-15 minutes.

[0040] S12. The heat-treated material is subjected to steam pulverization, wherein the steam temperature is 320-480℃ and the pressure is 2.6-3.4MPa.

[0041] This invention employs a special dispersion technique to form a super-dispersed base material slurry. Through grinding and grading, a highly dispersed and uniformly sized base material slurry is obtained. Based on this, a multi-element hybrid film of zirconium, silicon, and aluminum is formed under specific conditions. Utilizing the strong surface affinity between zirconium and titanium (both in the same group), a uniform multi-element hybrid film is formed. The second layer is a continuous and dense silica film. This continuous and complete silica film tightly encapsulates the multi-element hybrid film, effectively shielding the photocatalytic reaction of titanium dioxide and providing the product with exceptional weather resistance. The third layer is a film of bayonet-boehmite-amorphous mixed-crystal alumina doped with loose silica. After heat treatment, a 0.3–0.7% active hydroxyl coating is formed. Without the need for any organic additives, particle agglomeration is avoided, achieving dispersion in a water-oil dual-system. The titanium dioxide product prepared by this invention exhibits excellent weather resistance, good dispersibility within the system, and is environmentally friendly. Detailed Implementation

[0042] This invention provides a high-performance, green, and environmentally friendly titanium dioxide for coatings, comprising a titanium dioxide substrate and a coating layer on the surface of the titanium dioxide substrate. The coating layer comprises, from the inside out, a zirconium-silicon-aluminum hybrid film layer, a dense silicon oxide film layer, and a bayonet-boehmite-amorphous mixed crystal alumina-doped loose silicon oxide film layer.

[0043] The coating layer contains 0.4 to 0.7% active hydroxyl groups by mass fraction of the total mass of titanium dioxide.

[0044] This application employs a multi-layer composite coating for titanium dioxide. The innermost layer is a zirconium-silicon-aluminum hybrid film. Since zirconium and titanium belong to the same group, they have strong surface affinity, thus forming a uniform zirconium-silicon-aluminum hybrid film. Zirconium oxide and titanium oxide, being in the same group, readily adsorb onto the titanium dioxide surface to form a film, providing a foundation for subsequent silicon-aluminum co-deposition. This zirconium-silicon-aluminum hybrid film is denser and more continuous, significantly shielding the lattice defects of titanium dioxide particles, forming the first barrier film for titanium dioxide and laying the foundation for improved weather resistance. The second layer is a continuous and dense silicon oxide film, tightly wrapped around the outside of the zirconium-silicon-aluminum hybrid film, effectively shielding the photocatalytic reaction of titanium dioxide and providing the product with exceptional weather resistance. The third layer is a film of bayonet-boehmite-amorphous mixed alumina doped with loose silicon oxide. Under specific temperature and pH conditions, a layer of outer film formed from Bayerite-boehmite-amorphous mixed alumina and loose silica is formed. Because it contains a large amount of both Si-OH and Al-OH, and undergoes a special treatment as described in this application (see below, heat treatment after flash powder), the amount of active hydroxyl groups coated is reduced to 0.4-0.7%. Experimental studies have shown that excessive residual active hydroxyl groups lead to poor weather resistance, while excessively low residual hydroxyl groups result in poor dispersibility, rendering the product unusable. A concentration within the range of 0.4-0.7% allows the product to possess both excellent weather resistance and dispersibility.

[0045] Therefore, the titanium dioxide obtained in this application does not require the addition of any organic additives, which can avoid particle agglomeration, achieve dispersion in a water-oil dual system, is green and environmentally friendly, and has excellent weather resistance, making it suitable for use in coatings.

[0046] Preferably, in the zirconium-silicon-aluminum hybrid film, the coating amount of zirconium, calculated as zirconium dioxide, is 0.3-0.8% of the mass of the titanium dioxide substrate; the coating amount of silicon, calculated as silicon dioxide, is 1.3-1.8% of the mass of the titanium dioxide substrate; and the coating amount of aluminum, calculated as alumina, is 0.1-1.5% of the mass of the titanium dioxide substrate.

[0047] Preferably, the coating amount of the dense silicon oxide film, measured in silicon dioxide, is 1.0 to 1.5% of the mass of the titanium dioxide substrate.

[0048] Preferably, in the Bayerite-boehmite-amorphous mixed alumina-doped loose silicon oxide film, the amount of aluminum coating, calculated as alumina, is 1.4 to 2.2% of the mass of the titanium dioxide substrate, and the amount of silicon coating, calculated as silicon dioxide, is 0.2 to 0.5% of the mass of the titanium dioxide substrate.

[0049] Preferably, the zirconium-silicon-aluminum multi-element hybrid film is prepared by the following steps:

[0050] A titanium dioxide-based material slurry is taken and an aluminum source, a zirconium source, and a pH adjuster are added concurrently, maintaining the concurrent pH at 1.2–1.8. After homogenization, a silicon source is added, and the pH is adjusted to 8.5–9.5. After homogenization, a multi-element hybrid film of zirconium, silicon, and aluminum is formed. Since commonly used soluble silicon sources in existing technologies are generally alkaline, such as sodium silicate and potassium silicate, and commonly used zirconium sources are acidic, such as zirconium oxysulfate and zirconium oxychloride, this application first adds the aluminum source, zirconium source, and pH adjuster, and homogenizes them to ensure full dispersion in the slurry. Then, the silicon source is added, and at pH 8.5–9.5, a multi-element hybrid film of zirconium silicate and aluminum silicate is co-precipitated. If the order of raw material addition is adjusted, the ideal substance cannot be formed.

[0051] Preferably, the coating temperature of the zirconium-silicon-aluminum hybrid film is 40-55℃, the aluminum source is an acidic aluminum source, the zirconium source is an acidic zirconium source, the aluminum source, the zirconium source and the pH adjuster are added in parallel for 20-40 min, and the homogenization time after addition is 20-50 min.

[0052] Further preferred, the silicon source is added at a time of 60–80 min, and the homogenization time after addition is 20–30 min.

[0053] Preferably, the dense silicon oxide film is prepared by the following steps:

[0054] A silicon source is added to a titanium dioxide slurry coated with a zirconium-silicon-aluminum hybrid film at a temperature of 85–95°C, and the pH is adjusted to 9.8–10.2. The silicon source is added over a period of 10–20 minutes, and after homogenization for 20–30 minutes, a dense silicon oxide film is formed. Conventional dense silicon films generally require a longer deposition time compared to loose silicon films. However, the zirconium-silicon-aluminum hybrid film first coated in this application is conducive to inducing the formation of a dense silicon oxide film. The subsequent addition of the aluminum source also helps to make the dense silicon in the intermediate layer even more compact. Moreover, the amount of silicon source used in the dense silicon film layer of this application is also relatively small. Therefore, the deposition of the intermediate dense silicon at a high temperature of 85–95°C does not require a very long time to achieve the desired density and form a dense silicon film layer.

[0055] Preferably, the bayonet-boehmite-amorphous mixed alumina-doped porous silica film is prepared by the following steps:

[0056] A first acidic aluminum source was added to a titanium dioxide slurry coated with a zirconium-silicon-aluminum multi-element hybrid film and a dense silica film at a pH of 9.8–10.2. The pH was adjusted to 6.0–8.0 and homogenized. Then, a second acidic aluminum source, a silicon source, and a pH adjuster were added in parallel to maintain the pH at 8.5–9.5. The slurry was homogenized and the pH was adjusted to 8.0–8.5. After homogenization, a Bayerite-boehmite-amorphous mixed crystal alumina-doped loose silica film was formed. In an alkaline titanium dioxide slurry, a first acidic aluminum source is first added to adjust the pH to 6.0–8.0. During the addition of the first acidic aluminum source, the slurry around the first acidic aluminum source is acidic, which can generate amorphous alumina. Then, a second acidic aluminum source and a silicon source are added, maintaining a co-current pH of 8.5–9.5. At this stage, bayerite-type alumina is formed. The pH is then adjusted to 8.0–8.5 to form boehmite alumina. During the precipitation of bayerite-type alumina and boehmite alumina, silica also co-precipitates. Due to the presence of alumina precipitation, the formed silica is relatively loose. Further preferably, the first acidic aluminum source is added at a temperature of 85–95°C for 40–60 min, followed by a homogenization time of 20–30 min; the second acidic aluminum source, silicon source, and pH adjuster are added at a temperature of 65–75°C in parallel flow for 60–80 min, followed by a homogenization time of 20–30 min; then the temperature is raised to 90–95°C to adjust the pH to 8.0–8.5 for 20–40 min, followed by a homogenization time of 60–80 min.

[0057] The preparation method of the high-performance green and environmentally friendly titanium dioxide for coatings as described above includes the following steps:

[0058] S1. Preparation of titanium dioxide-based material slurry: Take titanium dioxide base material, add dispersant and hydrogen peroxide to prepare titanium dioxide-based material slurry; the titanium dioxide base material is dry powder from the chloride oxidation process, and hydrogen peroxide is used to remove excess chloride ions from the titanium dioxide base material on the one hand, and to provide a suitable environment for the dispersant on the other hand.

[0059] S2. Coating: Take a titanium dioxide-based material slurry and sequentially coat it with a zirconium-silicon-aluminum multi-element hybrid film, a dense silicon oxide film, and a bayonet-boehmite-amorphous mixed crystal alumina-doped loose silicon oxide film.

[0060] S3. Gasification: Take the coated material, dry it, heat treat it at 280-350℃, and then gasify it to obtain titanium dioxide.

[0061] After being coated with an outer film of Bayerite-boehmite-amorphous mixed crystal alumina doped with loose silica, the outer film contains a large amount of Si-OH and Al-OH. Through flash vaporization and subsequent high-temperature heat treatment, the active hydroxyl groups undergo mutual condensation to form stable Al-O-Si bonds, which replace Si-OH and Al-OH in part of the OH. This reduces the active hydroxyl groups on the surface of the titanium dioxide film to a suitable range, thereby reducing the photocatalytic activity of the titanium dioxide and improving product stability. Preferably, the dispersant in step S1 is a combination of sodium hexametaphosphate and sodium citrate, with a mass ratio of sodium hexametaphosphate to sodium citrate of (0.5-1.0):1, and the total amount of dispersant added is 0.15-0.70% of the mass of the titanium dioxide substrate. This application uses sodium hexametaphosphate and sodium citrate as dispersants. Sodium hexametaphosphate subsequently enters the inorganic membrane layer, providing dispersion during the pre-coating milling process and dispersibility in the early stages of the coating process, co-precipitating with the membrane layer to increase its lightfastness. Sodium citrate does not enter the membrane layer and can be removed by washing, providing a good dispersion environment for the entire process of milling and coating. The combined use of both is more effective than using them alone, resulting in a more uniform and dense membrane layer and superior product performance.

[0062] Preferably, the amount of hydrogen peroxide added is 0.5% to 1.2% of the mass of the titanium dioxide substrate.

[0063] Preferably, after adding the dispersant and hydrogen peroxide, step S1 further includes adjusting the pH to 5.0-7.5 and grinding and sieving to ensure that the mass percentage of 0.28-0.34μm particles in the obtained slurry is ≥85%.

[0064] Preferably, the heat treatment time in step S3 is 10 to 15 minutes;

[0065] Preferably, the steam temperature used for the steam pulverizer is 320–480℃ and the pressure is 2.6–3.4 MPa.

[0066] This application provides a preferred method for preparing high-performance, environmentally friendly titanium dioxide for coatings, comprising the following steps:

[0067] S1. Take the titanium dioxide substrate dry powder, dispersant and hydrogen peroxide from the chlorination oxidation section, add them to water to form a slurry with a concentration of 500-750 g / L;

[0068] S2. Adjust the pH to 5.0–7.5, then homogenize for 60–90 minutes;

[0069] S3. Grind and pass through a sieve of ≥800 mesh to ensure that the mass percentage of 0.28-0.34μm particles in the slurry is ≥85%, and then dilute to a concentration of 250-380g / L;

[0070] S4. Heat to 40-55℃, add acidic aluminum source, acidic zirconium source and acidic pH adjuster in parallel flow, maintain the pH of the parallel flow at 1.2-1.8, add in parallel flow for 20-40 min, and then homogenize for 20-50 min;

[0071] S5. Add silicon source, adjust pH to 8.5-9.5, add silicon source for 60-80 min, and then homogenize for 20-30 min;

[0072] S6. Heat to 85-95℃, add silicon source, adjust pH to 9.8-10.2, silicon source addition time is 10-20 min, then homogenize for 20-30 min;

[0073] S7. Add acidic aluminum source, adjust pH to 6.0-8.0, add acidic aluminum source for 40-60 min, then homogenize for 20-30 min;

[0074] S8. Cool to 65-75℃, add acidic aluminum source, silicon source and alkaline pH adjuster in parallel flow, maintain the pH of parallel flow at 8.5-9.5, add in parallel flow for 60-80 min, and then homogenize for 20-30 min;

[0075] S9. Heat to 90-95℃, adjust the pH to 8.0-8.5 using an acidic pH adjuster, add the acidic pH adjuster for 20-40 minutes, and then homogenize for 60-80 minutes;

[0076] S10. The slurry from step S9 is subjected to pressure filtration and washing to remove the salt in the filter cake and obtain the filter cake.

[0077] S11. The filter cake is dried and then subjected to heat treatment at a temperature of 280-350°C for 10-15 minutes.

[0078] S12. The heat-treated material is subjected to steam pulverization. The steam temperature used for steam pulverization is 320-480℃ and the pressure is 2.6-3.4MPa.

[0079] The acidic pH adjuster in this application may be one or both of dilute sulfuric acid and dilute hydrochloric acid, with a concentration of 50–80 g / L. The alkaline pH adjuster may be one of sodium hydroxide solution or potassium hydroxide solution, with a concentration of 50–120 g / L.

[0080] Acidic aluminum sources can be solutions of aluminum sulfate, aluminum chloride, aluminum nitrate, etc., with a solution concentration of 85–125 g / L (calculated as alumina) and an acidity of 15–18% (calculated as H ion concentration). Acidic zirconium sources can be solutions of zirconium oxysulfate, zirconium oxychloride, etc., with a solution concentration of 95–140 g / L (calculated as zirconium oxide) and an acidity of 20–25%. The preferred silicon source is one or a combination of sodium silicate solution or potassium silicate solution, with a concentration of 80–150 g / L (calculated as silicon oxide) and a solution pH of 9.5–10.5.

[0081] Example 1

[0082] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.05% sodium hexametaphosphate and 0.10% sodium citrate, and 0.8% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 650 g / L. The pH was adjusted to 5.0, and after homogenization for 60 min, the mixture was ground three times and passed through an 800-mesh sieve. 99% of the slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 85%.

[0083] Dilute the slurry to 250 g / L, heat to 40℃, add 1.1% aluminum sulfate solution (alumina concentration 85 g / L, acidity 15%), 0.8% zirconium oxychloride solution (zirconia concentration 95 g / L, acidity 20%), and dilute sulfuric acid solution (concentration 50 g / L) to maintain pH at 1.2, add in parallel for 40 min, and then homogenize for 20 min; add 1.8% sodium silicate solution (concentration 120 g / L, sodium silicate pH 9.5), adjust pH to 8.5, adjust for 60 min, and then homogenize for 20 min.

[0084] The slurry was heated to 85°C, and a 1.5% potassium silicate solution (concentration 150g / L, pH of potassium silicate is 10.5) was added. The pH was adjusted to 10.2, and the potassium silicate was added over a period of 10 minutes. Then the mixture was homogenized for 20 minutes.

[0085] Add 0.8% aluminum chloride solution (concentration 150 g / L, acidity 25%) to adjust the pH to 8.0 over 40 min, then homogenize for 20 min; cool to 65℃, and simultaneously add 0.6% aluminum nitrate solution (concentration 100 g / L, acidity 18%), 0.5% sodium silicate solution, and sodium hydroxide solution (concentration 50 g / L) to maintain the pH at 8.5 over 60 min, then homogenize for 20 min; heat to 95℃, and adjust the pH to 8.0 using 8% dilute hydrochloric acid solution over 20 min, then homogenize for 60 min.

[0086] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 280℃ for 10 min; subsequently, it was subjected to steam pulverization at 320℃ and 2.6 MPa to obtain sample 1. In sample 1, the mass percentage of 0.25–0.35 μm particles was 95%, and the mass percentage of active hydroxyl groups was 0.7%.

[0087] Example 2

[0088] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.35% sodium hexametaphosphate and 0.35% sodium citrate, and 0.5% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 750 g / L. The pH was adjusted to 7.5, and after homogenization for 90 min, the mixture was ground three times and passed through a 900-mesh sieve. 99% of the slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 99% of the total.

[0089] Dilute the slurry to 380 g / L, heat to 55°C, add 0.1% aluminum sulfate solution (alumina concentration 125 g / L, acidity 18%), 0.3% zirconium oxychloride solution (zirconia concentration 140 g / L, acidity 25%), and dilute hydrochloric acid solution (concentration 80 g / L), maintain the co-current pH at 1.8, add for 20 min, and then homogenize for 50 min; add 1.3% sodium silicate solution (concentration 120 g / L, sodium silicate pH 10.5), adjust the pH to 9.5, adjust for 80 min, and then homogenize for 30 min.

[0090] Heat the slurry to 95°C, add 1.0% sodium silicate solution (concentration 150g / L, sodium silicate pH is 10.5), adjust the pH to 9.8, add for 20 minutes, and then homogenize for 30 minutes.

[0091] Add 1.0% aluminum chloride solution (concentration 100 g / L, acidity 17%) to adjust the pH to 6.5 over 60 min, then homogenize for 30 min; cool to 75℃, and simultaneously add 0.8% aluminum trichloride solution (concentration 125 g / L, acidity 15%), 0.2% sodium silicate solution (concentration 125 g / L, sodium silicate pH 9.8), and sodium hydroxide solution (concentration 80 g / L) to maintain the pH at 9.5 over 80 min, then homogenize for 30 min; heat to 90℃, adjust the pH to 8.5 using 12% dilute hydrochloric acid solution over 40 min, then homogenize for 80 min.

[0092] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 350℃ for 15 minutes; subsequently, it was subjected to steam pulverization at 480℃ and 3.4 MPa to obtain sample 2. In sample 2, the mass percentage of 0.25–0.35 μm particles was 95%, and the mass percentage of active hydroxyl groups was 0.3%.

[0093] Example 3

[0094] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.25% sodium hexametaphosphate and 0.35% sodium citrate, and 1.2% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 500 g / L. The pH was adjusted to 5.5, and after homogenization for 80 minutes, the mixture was ground three times and passed through an 800-mesh sieve. The slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 92%.

[0095] Dilute the slurry to 300 g / L, heat to 50℃, and simultaneously add 1.4% aluminum sulfate solution (alumina concentration 115 g / L, acidity 17%), 0.5% zirconium oxychloride solution (zirconia concentration 115 g / L, acidity 21%), and dilute sulfuric acid solution (concentration 60 g / L), maintaining the pH at 1.3 for 30 min, then homogenize for 40 min; add 1.5% sodium silicate solution (concentration 100 g / L, sodium silicate pH 10.1), adjust the pH to 8.7 for 70 min, then homogenize for 25 min.

[0096] Heat the slurry to 90℃, add 1.3% sodium silicate solution (concentration 120g / L, sodium silicate pH is 10.5), adjust the pH to 10, add for 15min, and then homogenize for 25min.

[0097] Add 1.4% aluminum chloride solution (concentration 110 g / L, acidity 17%) to adjust the pH to 6.0 over 30 min, then homogenize for 25 min; cool to 70℃, and simultaneously add 0.7% aluminum sulfate solution (concentration 125 g / L, acidity 18%), 0.4% sodium silicate solution (concentration 125 g / L, sodium silicate pH 9.8), and sodium hydroxide solution (concentration 120 g / L) to maintain the pH at 9.0 over 70 min, then homogenize for 25 min; heat to 93℃, and adjust the pH to 8.3 using 5% dilute hydrochloric acid solution over 30 min, then homogenize for 70 min.

[0098] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 300℃ for 14 minutes; subsequently, it was subjected to steam pulverization at 450℃ and 3.2 MPa to obtain sample 3. Sample 3 contained 99% particles of 0.25–0.35 μm and 0.35% active hydroxyl groups.

[0099] Example 4

[0100] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.25% sodium hexametaphosphate and 0.25% sodium citrate, and 1.0% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 650 g / L. The pH was adjusted to 7.0, and after homogenization for 70 min, the mixture was ground three times and passed through a 900-mesh sieve. The slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 96%.

[0101] Dilute the slurry to 300 g / L, heat to 50°C, add 1.0% aluminum sulfate solution (alumina concentration 105 g / L, acidity 15%), 0.5% zirconium oxychloride solution (zirconia concentration 115 g / L, acidity 20%), and dilute sulfuric acid solution (concentration 55 g / L), maintain pH at 1.3, add for 30 min, then homogenize for 40 min; add 1.3% sodium silicate solution (concentration 95 g / L, sodium silicate pH 9.5), adjust pH to 8.5, adjust for 70 min, then homogenize for 25 min.

[0102] Heat the slurry to 90℃, add 1.5% sodium silicate solution (concentration 120g / L, pH of sodium silicate is 10.5), adjust the pH to 10, add for 15min, and then homogenize for 25min.

[0103] Add 0.8% aluminum chloride solution (concentration 110 g / L, acidity 18%) to adjust the pH to 6.0 over 40 min, then homogenize for 20 min. Cool to 70℃ and simultaneously add 0.7% aluminum sulfate solution (concentration 125 g / L, acidity 20%), 0.4% sodium silicate solution (concentration 125 g / L, sodium silicate pH 9.8), and sodium hydroxide solution (concentration 80 g / L) to maintain the pH at 9.0 over 70 min, then homogenize for 25 min. Heat to 90℃ and adjust the pH to 8.3 using 10% dilute hydrochloric acid solution over 30 min, then homogenize for 70 min.

[0104] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 300℃ for 10 minutes; subsequently, it was subjected to steam pulverization at 420℃ and 3.2 MPa to obtain sample 4. Sample 4 contained 98% particles of 0.25–0.35 μm by mass and 0.55% active hydroxyl groups by mass.

[0105] Example 5

[0106] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.25% sodium hexametaphosphate and 0.25% sodium citrate, and 0.6% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 650 g / L. The pH was adjusted to 7.0, and after homogenization for 70 min, the mixture was ground three times and passed through an 800-mesh sieve. The slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 91%.

[0107] Dilute the slurry to 300 g / L, heat to 50°C, add 1.0% aluminum sulfate solution (alumina concentration 85 g / L, acidity 16%), 0.5% zirconium oxychloride solution (zirconia concentration 95 g / L, acidity 25%), and dilute sulfuric acid solution (concentration 50 g / L), maintain pH at 1.5, add for 30 min, then homogenize for 40 min; add 1.3% sodium silicate solution (concentration 150 g / L, sodium silicate pH 10.5), adjust pH to 9.0, adjust for 70 min, then homogenize for 25 min.

[0108] Heat the slurry to 95°C, add 1.5% sodium silicate solution (concentration 100g / L, sodium silicate pH is 10.5), adjust the pH to 10.2, add for 15 minutes, and then homogenize for 25 minutes.

[0109] Add 0.8% aluminum chloride solution (concentration 125 g / L, acidity 18%) to adjust the pH to 6.0 over 40 min, then homogenize for 20 min; cool to 70℃, and simultaneously add 0.7% aluminum sulfate solution (concentration 115 g / L, acidity 17%), 0.4% sodium silicate solution (concentration 125 g / L, sodium silicate pH 9.8), and sodium oxide solution (concentration 80 g / L) to maintain the pH at 9.0 over 70 min, then homogenize for 25 min; heat to 90℃, adjust the pH to 8.0 using 5% dilute hydrochloric acid solution over 30 min, then homogenize for 70 min.

[0110] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 280℃ for 10 min; subsequently, it was subjected to steam pulverization at 450℃ and 3.2 MPa to obtain sample 5, in which 0.25–0.35 μm particles accounted for 98% by mass and active hydroxyl groups accounted for 0.45% by mass.

[0111] Example 6

[0112] The dry powder from the chlorination oxidation section, a two-component dispersant solution of 0.15% sodium hexametaphosphate and 0.25% sodium citrate, and 0.6% hydrogen peroxide were sequentially added to the demineralized water to form a slurry with a concentration of 650 g / L. The pH was adjusted to 7.0, and after homogenization for 70 min, the mixture was ground three times and passed through an 800-mesh sieve. The slurry passed through smoothly, and the particle size was concentrated in the range of 0.28–0.340 μm, accounting for 91%.

[0113] Dilute the slurry to 300 g / L, heat to 50℃, add 0.8% aluminum sulfate solution (alumina concentration 85 g / L, acidity 16%), 0.4% zirconium oxychloride solution (zirconia concentration 95 g / L, acidity 25%), and dilute sulfuric acid solution (concentration 50 g / L), maintain pH at 1.5, add for 30 min, then homogenize for 40 min; add 1.0% sodium silicate solution (concentration 150 g / L, sodium silicate pH 10.5), adjust pH to 8.5, adjust for 70 min, then homogenize for 25 min.

[0114] Heat the slurry to 90℃, add 1.5% sodium silicate solution (concentration 100g / L, sodium silicate pH is 10.5), adjust the pH to 10.2, add for 15min, and then homogenize for 25min.

[0115] Add 1.0% aluminum sulfate solution (concentration 125 g / L, acidity 18%) to adjust the pH to 6.0 over 40 min, then homogenize for 20 min; cool to 70℃, and simultaneously add 0.6% aluminum sulfate solution (concentration 115 g / L, acidity 17%), 0.3% sodium silicate solution (concentration 125 g / L, sodium silicate pH 9.8), and sodium hydroxide solution (concentration 80 g / L) to maintain the pH at 9.0 over 70 min, then homogenize for 25 min; heat to 90℃, adjust the pH to 8.0 using 7% dilute hydrochloric acid solution over 30 min, then homogenize for 70 min.

[0116] The slurry was pressure-filtered and washed to remove salt from the filter cake; the filter cake was then flash-dried and heat-treated at 290℃ for 10 min; subsequently, it was subjected to steam pulverization at 430℃ and 3.3 MPa to obtain sample 6, in which 0.25–0.35 μm particles accounted for 97% by mass and active hydroxyl groups accounted for 0.65% by mass.

[0117] Comparative Example 1

[0118] The dry powder from the chlorination oxidation section and 0.45% sodium hexametaphosphate dispersant were added sequentially to the demineralized water to form a slurry with a concentration of 650 g / L. The slurry was ground three times and passed through an 800-mesh sieve, but the slurry could not pass through smoothly.

[0119] The slurry after sand milling was passed through a 400-mesh sieve with a passing rate of 95%. The particle size was concentrated in the range of 0.28–0.34 μm, with a proportion of 55%. The sieved slurry was diluted to 300 g / L and heated to 65°C. A 0.5% zirconium oxychloride solution with a concentration of 120 g / L was added. The pH was then adjusted to 10.0 with a 100 g / L sodium hydroxide solution. A 3.2% sodium silicate solution was added, and the pH was adjusted to 7.0 with sulfuric acid. A 2.5% aluminum sulfate solution was added and mixed with the sodium hydroxide solution to bring the pH to 6.5–7.5. The final pH was adjusted to 6.3 with sulfuric acid. After routine washing, drying, and pulverizing steps, control sample 1 (a three-layer coating of conventional zirconium oxide, silicon dioxide, and amorphous alumina) was obtained.

[0120] Comparative Example 2

[0121] The slurry from Comparative Example 1, after sand milling, was passed through a 400-mesh sieve with a passing rate of 95%. The sieved slurry was diluted to 300 g / L, heated to 95°C, and 0.8% of a 120 g / L zirconium oxychloride solution was added. Then, the pH was adjusted to 10.0 with 100 g / L sodium hydroxide solution, 3.5% sodium silicate solution was added, and the pH was adjusted to 7.0 with sulfuric acid. 2.5% aluminum sulfate solution was added and mixed with sodium hydroxide solution to bring the pH to 8.0–8.5. The final pH was adjusted to 6.0 with sulfuric acid. After routine washing, drying, and pulverizing steps, Comparative Sample 2 (a three-layer coating of conventional zirconium oxide, silica, and boehmite alumina) was obtained.

[0122] Comparative Example 3

[0123] The dry powder from the chlorination oxidation section and 0.45% sodium citrate dispersant were added to the demineralized water in sequence to form a slurry with a concentration of 650 g / L. The slurry was ground three times and passed through an 800-mesh sieve, but the slurry could not pass through smoothly.

[0124] The slurry after sand milling was passed through a 400-mesh sieve with a passing rate of 95%. The sieved slurry was diluted to 300 g / L, heated to 95℃, and 0.8% zirconium oxychloride solution with a concentration of 120 g / L was added. Then, the pH was adjusted to 10.0 with 100 g / L sodium hydroxide solution, 3.0% sodium silicate solution was added, and the pH was adjusted to 7.0 with sulfuric acid. 3.0% aluminum sulfate solution was added and mixed with sodium hydroxide solution to bring the pH to 7.0-7.5. The final pH was adjusted to 6.0 with sulfuric acid. After routine washing, drying, and pulverization, control sample 3 was obtained.

[0125] Comparative Example 4

[0126] The dry powder from the chlorination oxidation section and 0.45% sodium citrate dispersant were added to the demineralized water in sequence to form a slurry with a concentration of 650 g / L. The slurry was ground three times and passed through an 800-mesh sieve, but the slurry could not pass through smoothly.

[0127] The slurry after sand milling was passed through a 400-mesh sieve with a passing rate of 95%. The sieved slurry was diluted to 300 g / L, heated to 95℃, and 0.8% zirconium oxychloride solution with a concentration of 120 g / L was added. Then, the pH was adjusted to 10.0 with 100 g / L sodium hydroxide solution, 3.0% sodium silicate solution was added, and the pH was adjusted to 7.0 with sulfuric acid. 3.0% aluminum sulfate solution was added and mixed with sodium hydroxide solution to adjust the pH to 7.0-7.5. The final pH was adjusted to 6.0 with sulfuric acid. After routine washing, drying, and pulverizing, 0.75% TMP was added to obtain control sample 4.

[0128] Performance evaluation of the proportions and examples

[0129] The performance of titanium dioxide samples obtained from the embodiments and comparative examples of this application, as well as commercially available domestic and foreign similar samples, was tested using conventional methods. The results are shown in Tables 1 and 2.

[0130] Table 1 Sample production data and physicochemical performance tests

[0131]

[0132] Table 2 Weather resistance test data of samples in alkyd system

[0133]

[0134] As shown in Tables 1 and 2, the titanium dioxide prepared by this invention has high whiteness, high dispersibility, and weather resistance compared with the comparative samples and domestic and foreign samples. At the same time, its dispersibility is much better than that of the sample without organic additives, and it is also better than that of the sample coated with organic treatment agent (Comparative Example 4). This shows that the titanium dioxide prepared by this invention can be produced without adding organic additives and has VOC-free, high whiteness, high dispersibility, and weather resistance.

[0135] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for preparing titanium dioxide for high-performance green and environmentally friendly coatings, characterized by, The method comprises the following steps: S1. Preparing a titanium dioxide-based material slurry: taking a titanium white-based material, adding a dispersing agent and hydrogen peroxide to prepare a titanium dioxide-based material slurry; The dispersing agent is a sodium hexametaphosphate and sodium citrate composition, the mass ratio of sodium hexametaphosphate to sodium citrate in the dispersing agent is (0.5-1.0):1, and the total amount of the dispersing agent added is 0.15-0.70% of the mass of the titanium dioxide-based material; the amount of hydrogen peroxide added is 0.5-1.2% of the mass of the titanium dioxide-based material; S2. Coating: taking the titanium dioxide-based material slurry, sequentially performing coating of a zirconium-silicon-aluminum multi-element hybrid film layer, a dense silicon oxide film layer, and a Bayer stone-boehmite-amorphous mixed crystal aluminum oxide doped loose silicon oxide film layer; The coating of the zirconium-silicon-aluminum multi-element hybrid film layer comprises: The temperature is raised to 40-55℃, and the aluminum source, zirconium source and pH adjuster are added in parallel flow, the parallel flow pH is maintained at 1.2-1.8, and homogenization is performed; then the silicon source is added, the pH is adjusted to 8.5-9.5, and homogenization is performed; The coating of the dense silicon oxide film layer comprises: The temperature is raised to 85-95℃, the silicon source is added, the pH is adjusted to 9.8-10.2, the silicon source is added for 10-20 min, and homogenization is performed for 20-30 min; The coating of the Bayer stone-boehmite-amorphous mixed crystal aluminum oxide doped loose silicon oxide film layer comprises: The first acidic aluminum source is added, the pH is adjusted to 6.0-8.0, and homogenization is performed; the temperature is lowered to 65-75℃, then the second acidic aluminum source, silicon source and pH adjuster are added in parallel flow, the parallel flow pH is maintained at 8.5-9.5, and then homogenization is performed; the temperature is raised to 90-95℃, the pH is adjusted to 8.0-8.5, and homogenization is performed; S3. Steam powdering: taking the coated material, drying, then performing heat treatment at 280-350℃, and then performing steam powdering to obtain titanium white powder.

2. The method for preparing the high-performance green and environmentally friendly titanium white powder for paint according to claim 1, wherein After the dispersing agent and hydrogen peroxide are added in step S1, a step of adjusting the pH to 5.0-7.5 and grinding and sieving is further included to ensure that the mass ratio of 0.28-0.34µm particles in the obtained slurry is ≥85%.

3. The method for preparing the high-performance green and environmentally friendly titanium white powder for paint according to claim 1, wherein In step S3, the heat treatment time is 10-15 min; The steam powdering uses steam at a temperature of 320-480℃ and a pressure of 2.6-3.4MPa.

4. The method for preparing the high-performance green and environmentally friendly titanium white powder for paint according to claim 1, wherein In the coating of the zirconium-silicon-aluminum multi-element hybrid film layer: The aluminum source is an acidic aluminum source, the zirconium source is an acidic zirconium source, the aluminum source, zirconium source and pH adjuster are added in parallel flow for 20-40 min, and homogenization is performed for 20-50 min after addition; The silicon source is added for 60-80 min, and homogenization is performed for 20-30 min after addition.

5. The method for preparing the high-performance green and environmentally friendly titanium white powder for paint according to claim 1, wherein The bayerite-boehmite-amorphous mixed crystal alumina doped loose silica membrane layer is doped in the coating of the coating layer. The first acidic aluminum source is added for 40-60 min, and the homogenization time after addition is 20-30 min; the second acidic aluminum source, the silicon source and the pH regulator are added for 60-80 min, and the homogenization time after addition is 20-30 min; the adjustment time of the pH regulator for adjusting the pH to 8.0-8.5 is 20-40 min, and the homogenization time after adjustment is 60-80 min.

6. The method for preparing titanium dioxide for high-performance green and environment-friendly paint according to claim 1, characterized in that, The method comprises the following steps: S1. Take the titanium dioxide base material dry powder of the chlorination method oxidation section, a dispersing agent and hydrogen peroxide, and add them to water to form a slurry with a concentration of 500-750 g / L; S2. Adjust the pH to 5.0-7.5, and then homogenize for 60-90 min; S3. Grind and pass through a sieve with a mesh size of ≥800 to ensure that the mass fraction of particles with a size of 0.28-0.34 µm in the slurry is ≥85%, and then dilute to a concentration of 250-380 g / L; S4. Increase the temperature to 40-55 ℃, and add the acidic aluminum source, the acidic zirconium source and the acidic pH regulator in parallel flow, maintain the parallel flow pH at 1.2-1.8, and add for 20-40 min, and then homogenize for 20-50 min; S5. Add the silicon source, adjust the pH to 8.5-9.5, the silicon source addition time is 60-80 min, and then homogenize for 20-30 min; S6. Increase the temperature to 85-95 ℃, add the silicon source, adjust the pH to 9.8-10.2, the silicon source addition time is 10-20 min, and then homogenize for 20-30 min; S7. Add the first acidic aluminum source, adjust the pH to 6.0-8.0, the first acidic aluminum source addition time is 40-60 min, and then homogenize for 20-30 min; S8. Decrease the temperature to 65-75 ℃, add the second acidic aluminum source, the silicon source and the basic pH regulator in parallel flow, maintain the parallel flow pH at 8.5-9.5, and add for 60-80 min, and then homogenize for 20-30 min; S9. Increase the temperature to 90-95 ℃, adjust the pH to 8.0-8.5 using the acidic pH regulator, the acidic pH regulator addition time is 20-40 min, and then homogenize for 60-80 min; S10. Perform pressure filtration washing on the slurry of step S9 to obtain a filter cake; S11. Dry the filter cake, and then perform heat treatment, the heat treatment temperature is 280-350 ℃, and the time is 10-15 min; S12. Steam powder the material after heat treatment, the steam powdering uses steam with a temperature of 320-480 ℃ and a pressure of 2.6-3.4 MPa.

7. The titanium dioxide for high performance green environmental protection coating prepared by the method according to any one of claims 1 to 6, characterized in that, The coating layer comprises a zirconium-silicon-aluminum multi-element hybrid membrane layer, a dense silica membrane layer and a bayerite-boehmite-amorphous mixed crystal alumina doped loose silica membrane layer from inside to outside. The coating layer comprises active hydroxyl groups with a mass fraction of 0.4-0.7% of the total mass of the titanium white powder. 8.The titanium dioxide for high-performance green and environment-friendly coating according to claim 7, characterized in that the amount of the zirconium element in the zirconium-silicon-aluminum multi-element hybrid film layer is 0.3-0.8% of the mass of the titanium dioxide substrate in terms of zirconium dioxide, the amount of the silicon element is 1.3-1.8% of the mass of the titanium dioxide substrate in terms of silicon dioxide, and the amount of the aluminum element is 0.1-1.5% of the mass of the titanium dioxide substrate in terms of aluminum oxide. 9.The titanium dioxide for high-performance green and environment-friendly coating according to claim 7, characterized in that the amount of the compact silicon dioxide film layer is 1.0-1.5% of the mass of the titanium dioxide substrate in terms of silicon dioxide. 10.The titanium dioxide for high-performance green and environment-friendly coating according to claim 7, characterized in that in the bayerite-boehmite-amorphous mixed crystal aluminum oxide doped loose silicon dioxide film layer, the amount of the aluminum element is 1.4-2.2% of the mass of the titanium dioxide substrate in terms of aluminum oxide, and the amount of the silicon element is 0.2-0.5% of the mass of the titanium dioxide substrate in terms of silicon dioxide. ​ ​ ​

Images