Preparation method of infrared reflection titanium dioxide

Abstract

The present invention discloses a preparation method of infrared reflective titanium dioxide, which comprises the following steps: S1. Using a titanium dioxide-based material slurry with a non-spherical particle morphology, first adding a soluble silicate source and a soluble barium source to react, generating a barium silicate hydrate precipitate and depositing it on the surface of the titanium dioxide substrate; S2. Adding a soluble zirconium source and a soluble phosphate source to react, generating a zirconium phosphate precipitate and depositing it on the surface of the barium silicate hydrate deposition layer; S3. Heating up to hydrolyze the barium silicate hydrate deposition layer on the surface of the titanium dioxide substrate; S4. Adding a soluble magnesium source and a soluble aluminum source for the deposition of magnesium hydroxide and aluminum hydroxide; S5. Calcining to make the deposited magnesium hydroxide and aluminum hydroxide calcine to form magnesium oxide and aluminum oxide. Under the combined action of various means in this application, the produced titanium dioxide has a high infrared reflectivity, can effectively shield the heat of sunlight, and reduce the temperature of the application occasions of titanium dioxide.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium dioxide preparation, and particularly relates to a preparation method of infrared reflective titanium dioxide. Background Art

[0002] The total energy of sunlight is mainly concentrated in the visible light region and the near-infrared region, accounting for about 95% of the total solar energy. Among them, the visible light region accounts for about 43%, and the infrared region accounts for about 52%. Most of the energy is concentrated in the range of 720 - 1100 nm, that is, the short-wave near-infrared region. While the irradiation of sunlight brings a large amount of energy to the earth, the negative effects of the urban heat island are gradually emerging, such as too high indoor temperature of buildings, accidents caused by the increase in the temperature of oil tank trucks, and the exposure of the thermal infrared characteristic signals of military equipment.

[0003] Early relevant research has shown that using near-infrared reflective pigments can keep the indoor temperature cool. The lighter the color, the higher the visible light reflectivity. White coatings have the highest visible light reflectivity. And TiO2 pigment is a white pigment with relatively high reflectivity and has basic pigment properties such as high hiding power, weather resistance, and washability. How to further improve the infrared reflectivity of TiO2 pigment is an important topic for current scholars to study. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of infrared reflective titanium dioxide to solve the deficiencies of the existing technology.

[0005] The purpose of the present invention is achieved by the following technical solutions:

[0006] A preparation method of infrared reflective titanium dioxide includes the following steps:

[0007] S1. Using a titanium dioxide-based material slurry with a non-spherical particle morphology, first adding a soluble silicate source and a soluble barium source for reaction to generate a barium silicate hydrate precipitate and deposit it on the surface of the titanium dioxide substrate;

[0008] S2. Adding a soluble zirconium source and a soluble phosphate source for reaction to generate a zirconium phosphate precipitate and deposit it on the surface of the barium silicate hydrate deposition layer;

[0009] S3. Heating to hydrolyze the barium silicate hydrate deposition layer on the surface of the titanium dioxide substrate;

[0010] S4. Adding a soluble magnesium source and a soluble aluminum source for the deposition of magnesium hydroxide and aluminum hydroxide;

[0011] S5. Calcining to make the deposited magnesium hydroxide and aluminum hydroxide calcine to form magnesium oxide and aluminum oxide.

[0012] Preferably, the titanium dioxide-based material slurry is a sulfuric acid process titanium white slurry;

[0013] In the salt treatment preparation process of the titanium dioxide substrate described in step S1, the salt treatment agent used includes aluminum salt, and the dosage of the aluminum salt is 0.25-0.35% of the mass of titanium dioxide in metatitanic acid before calcination.

[0014] Preferably, the addition amount of the soluble silicon source described in step S1, calculated as silicon dioxide, is 1.0-1.5% of the mass of the titanium dioxide substrate; the addition amount of the soluble barium source, calculated as barium oxide, is 1.7-2.6% of the mass of the titanium dioxide substrate.

[0015] Preferably, before adding the soluble silicon source and the soluble barium source in step S1, the pH of the titanium dioxide base material slurry is first adjusted to 9.0-9.5.

[0016] Preferably, before adding the soluble zirconium source and the soluble phosphoric acid source in step S2, the pH of the slurry is first adjusted to 6.8-7.2 to prevent premature hydrolysis of barium silicate hydrate;

[0017] The addition amount of the soluble zirconium source described in step S2, calculated as zirconium dioxide, is 0.3-0.5% of the mass of the titanium dioxide substrate; the addition amount of the soluble phosphoric acid source, calculated as phosphorus pentoxide, is 0.25%-0.4% of the mass of the titanium dioxide substrate.

[0018] Preferably, in step S3, the temperature is raised to 75-80 °C and kept warm for 1.5-2 h.

[0019] Preferably, the addition amount of the soluble magnesium source described in step S4, calculated as magnesium oxide, is 1.0-2.0% of the mass of the titanium dioxide substrate; the addition amount of the soluble aluminum source, calculated as aluminum oxide, is 1.5-2.0% of the mass of the titanium dioxide substrate.

[0020] Preferably, before adding the soluble magnesium source and the soluble aluminum source in step S4, the pH of the slurry is first adjusted to 9.5-10;

[0021] When adding the soluble magnesium source, a certain amount of pH regulator is also added in parallel, and the addition amount of the pH regulator is based on maintaining the parallel flow pH at 9.5-10;

[0022] When adding the soluble aluminum source, a certain amount of pH regulator is also added in parallel, and the addition amount of the pH regulator is based on maintaining the parallel flow pH at 9.5-10.

[0023] Preferably, in step S5, before calcination, the pH of the slurry is first adjusted to 6.3-6.5, and after calcination, air pulverization is carried out to obtain the titanium dioxide finished product.

[0024] Preferably, the calcination temperature in step S5 is 400-500 °C and the time is 2-3 h.

[0025] Under the combined action of various means, the titanium dioxide produced in this application has a high infrared reflectivity, which can effectively shield the heat of sunlight and reduce the temperature of the application occasions of titanium dioxide. Specific embodiments

[0026] The present invention provides a method for preparing infrared-reflective titanium dioxide, comprising the following steps:

[0027] S1. Using a titanium dioxide-based material slurry with a non-spherical particle morphology, first add a soluble silicate source and a soluble barium source to react, generating a hydrated barium silicate precipitate and depositing it on the surface of the titanium dioxide substrate;

[0028] S2. Add a soluble zirconium source and a soluble phosphate source to react, generating a zirconium phosphate precipitate and depositing it on the surface of the hydrated barium silicate deposition layer;

[0029] S3. Raise the temperature to hydrolyze the hydrated barium silicate deposition layer on the surface of the titanium dioxide substrate;

[0030] S4. Add a soluble magnesium source and a soluble aluminum source for the deposition of magnesium hydroxide and aluminum hydroxide;

[0031] S5. Calcinate to calcinate the deposited magnesium hydroxide and aluminum hydroxide to form magnesium oxide and aluminum oxide.

[0032] There are various forms of titanium dioxide particles, including spherical, rod-shaped, disc-shaped, etc. The higher the sphericity, the smaller the specific surface area. This application uses non-spherical titanium dioxide particles, increasing the specific surface area of the particles, thereby improving the light scattering degree and further improving the infrared reflectivity.

[0033] Generally, the titanium dioxide prepared by the conventional chloride process is spherical, and the titanium dioxide prepared by the sulfuric acid process can be spherical, rod-shaped, etc. depending on different production process parameters.

[0034] Therefore, this application preferably uses sulfuric acid process titanium white slurry. The sulfuric acid process titanium dioxide needs to be subjected to salt treatment after the second washing, bleaching and before calcination. Conventional salt treatment agents include phosphate salts, potassium salts, aluminum salts, etc. to improve product properties such as the hue, gloss, crystal grain morphology and size of titanium white particles. Experiments have proved that the particle morphology of titanium white is mainly affected by aluminum salts. During the salt treatment process, using a higher dosage of aluminum salts for salt treatment can, while improving other properties of titanium white, also obtain rod-shaped titanium white particles, increasing the specific surface area of the particles. The dosage of aluminum salt is 0.25-0.35% of the mass of titanium dioxide in metatitanic acid before calcination.

[0035] The soluble silicon source and the soluble barium source can form a water-insoluble barium silicate hydrate precipitate under certain conditions and deposit on the surface of titanium dioxide particles to form a barium silicate hydrate coating layer. Barium silicate hydrate is insoluble in cold water, but it is prone to hydrolysis in hot water to generate silicon dioxide and water. The reaction formula is as follows:

[0036] BaSiO3·6H2O + H2O=H2SiO3 + Ba(OH)2 + 5H2O

[0037] This application utilizes this property to coat a layer of zirconium phosphate on the surface of the barium silicate hydrate coating layer, and then raises the temperature of the slurry to cause the internal barium silicate hydrate coating layer to hydrolyze, generating silicic acid, barium hydroxide and water. The silicic acid precipitates in the form of silicon dioxide, and barium hydroxide and water are dissolved out, creating cavities during the dissolution process, having a relatively high thermal resistance and a relatively low thermal conductivity, effectively becoming a thermal barrier; at the same time, the precipitated SiO2 film layer after hydrolysis has a relatively high hemispherical emissivity, which can further improve the infrared reflectivity.

[0038] The precipitation reaction of barium silicate hydrate can be achieved by conventional techniques. Barium silicate hydrate is easily soluble under acidic conditions. This application provides a preferred method. First, adjust the pH of the titanium dioxide-based material slurry to 9.0 - 9.5, and then add the soluble silicon source and the soluble barium source. After the reaction, barium silicate hydrate precipitate is formed under alkaline conditions. As those skilled in the art can understand, steps such as adjusting the pH and adding materials need to be aged for a period of time to fully disperse the titanium dioxide slurry and make the materials fully contact and react with titanium dioxide.

[0039] Preferably, the soluble silicon source can be sodium silicate, potassium silicate, etc., and the soluble barium source can be barium chloride, barium nitrate, etc. The addition amount of the soluble silicon source, calculated as silicon dioxide, is 1.0 - 1.5% of the mass of the titanium dioxide base material; the addition amount of the soluble barium source, calculated as barium oxide, is 1.7 - 2.6% of the mass of the titanium dioxide base material. The soluble silicon source and the soluble barium source are added in the form of solutions, and the solution concentrations, calculated as silicon and barium oxides respectively, are 80 - 100 g / L.

[0040] The pH of the commonly used soluble silicon source is about 10, which is close to the pH of the titanium dioxide-based material slurry after pH adjustment. Therefore, it is preferred to add the soluble silicon source first and then the soluble barium source, which is conducive to the formation of barium silicate hydrate.

[0041] The zirconium phosphate precipitate is formed by the reaction of the soluble zirconium source and the soluble phosphate source under certain conditions, and it coats on the surface of the barium silicate hydrate coating layer, and cavities can be formed during the dissolution process of barium hydroxide and water. At the same time, the zirconium phosphate coating layer has a relatively low thermal conductivity and a high infrared reflectivity of up to 85%, which can effectively improve the infrared reflectivity.

[0042] The optimal pH for zirconium phosphate precipitation is below 9.0 - 9.5. Moreover, to prevent the premature hydrolysis of barium silicate hydrate, before adding the soluble zirconium source and soluble phosphate source, the pH of the slurry is first adjusted to 6.8 - 7.2. Commonly used soluble zirconium sources are ZrOCl2, ZrOSO4, etc., which all have relatively high acidity. To avoid the dissolution of barium silicate hydrate under acidic conditions, in this application, the pH of the slurry is first adjusted to neutral, and then preferably an alkaline or neutral phosphate source and zirconium source are added in a co-current manner. The phosphate source can be sodium phosphate, potassium phosphate, sodium hexametaphosphate, etc. The addition amount of the soluble zirconium source, calculated as zirconium dioxide, is 0.3 - 0.5% of the mass of the titanium dioxide substrate; the addition amount of the soluble phosphate source, calculated as phosphorus pentoxide, is 0.25 - 0.4% of the mass of the titanium dioxide substrate. The soluble zirconium source and soluble phosphate source are added in the form of a solution, and the solution concentrations, calculated as oxides of zirconium and phosphorus respectively, are 80 - 100 g / L.

[0043] As mentioned above, after the zirconium phosphate coating, the temperature is raised to hydrolyze barium silicate hydrate. The temperature for raising is preferably 75 - 80 °C, and it is kept warm for 1.5 - 2 h to fully hydrolyze barium silicate hydrate.

[0044] To improve the dispersibility of titanium dioxide, generally an aluminum hydroxide film layer is coated on the outermost layer of titanium dioxide. In this application, on the outer layer, aluminum hydroxide is first coated by a conventional method, and magnesium hydroxide is coated simultaneously, and then through calcination, the Mg(OH)2 and Al(OH)3 coating layers are calcined into metal oxides MgO and Al2O3. When light irradiates, due to the photoelectric effect, a large number of electron transitions occur, and heat is radiated into the air in the form of infrared rays, thereby increasing the hemispherical emissivity of the reflective and heat-insulating coating film. In the art, the film layers obtained without calcination after adding aluminum salts and magnesium salts are also simply referred to as alumina film layers and magnesia film layers in many literatures, but actually they are Mg(OH)2 and Al(OH)3 film layers. Only through calcination can the water be removed to become the true magnesia film layer and alumina film layer. The film layer without calcination has a high water of crystallization content, poor weather resistance, and poor anti-powdering performance of the coating, thus affecting the infrared reflection efficiency.

[0045] The soluble magnesium source is preferably added before the soluble aluminum source, which can make the alumina film layer located on the outermost side of the titanium dioxide. Magnesium hydroxide precipitates under alkaline conditions. Therefore, first adjust the pH of the slurry to 9.5 - 10, then add the soluble magnesium source, and at the same time add a certain amount of pH regulator in a co-current manner. The addition amount of the pH regulator is based on maintaining the co-current pH at 9.5 - 10. The addition amount of the soluble magnesium source, calculated as magnesium oxide, is 1.0 - 2.0% of the mass of the titanium dioxide substrate. The magnesium source can be magnesium chloride or magnesium sulfate, etc., and it is added in the form of a solution, and the solution concentration, calculated as magnesium oxide, is 80 - 100 g / L.

[0046] When adding the soluble aluminum source, a certain amount of pH regulator is added in parallel flow at the same time. The addition amount of the pH regulator is based on maintaining the parallel flow pH at 9.5 - 10. After aging, an aluminum hydroxide coating layer is formed. Precipitating aluminum hydroxide under the condition of pH 9.5 - 10, compared with lower pH conditions, the crystal form of the obtained aluminum hydroxide precipitate is more perfect and has better compatibility with the system.

[0047] The addition amount of the soluble aluminum source, calculated as aluminum oxide, is 1.5 - 2.0% of the mass of the titanium dioxide substrate. Aluminum sulfate or sodium metaaluminate can be used as the aluminum source, and it is added in the form of a solution during addition. The solution concentration is 100 - 160 g / L calculated as aluminum oxide. Preferably, the pH of the slurry is first adjusted to 6.3 - 6.5 before calcination to facilitate water washing and meet the requirements of the downstream product system. After calcination, flash evaporation is not required and it can be directly subjected to air pulverization to obtain the titanium dioxide finished product.

[0048] Preferably, the calcination temperature is 400 - 500 °C and the calcination time is 2 - 3 h to fully convert magnesium hydroxide and aluminum hydroxide. After calcination, through air pulverization, the titanium dioxide finished product is obtained.

[0049] For the processes not defined in the present invention, such as water washing, air pulverization, etc., conventional methods in the art are selected for implementation.

[0050] Therefore, under the combined action of the above-mentioned various means in this application, the produced titanium dioxide has a high infrared reflectivity, can effectively shield the heat of sunlight, and reduce the temperature of the application occasion of titanium dioxide.

[0051] Example 1

[0052] Take the sulfuric acid process titanium dioxide slurry with a rod-shaped particle morphology treated with high-aluminum salts (the specific dosage of the salt treatment agent is: 0.35% Al2O3, 0.21% K2O, 0.25% P2O5, calculated based on the mass fraction of titanium dioxide in the metatitanic acid before calcination), with a concentration of 350 g / L, and start stirring; adjust the pH of the slurry to 9.5 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; add 1% Na2SiO3, add it for 10 min, and then homogenize for 5 min; add 1.7% BaCl2, add it for 20 min, and then homogenize for 10 min; adjust the pH of the slurry to 7.2 with dilute H2SO4 solution, add H2SO4 for 10 min, and then homogenize for 10 min; add 0.3% ZrOCl2 and 0.25% (NaPO3)6 in parallel flow, add them in parallel flow for 10 min, and then homogenize for 10 min; heat up to 80 °C and keep warm for 1.5 h; adjust the pH of the slurry to 10 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; add 2% MgSO4 and NaOH solution in parallel flow, maintain the parallel flow pH at 10, add them in parallel flow for 30 min, and then homogenize for 10 min; then use 2% NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 10, add them in parallel flow for 30 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.3 with dilute H2SO4 solution; after the above slurry is washed with water, it is calcined at 500 °C for 3 h, and then air pulverized to obtain the finished titanium dioxide product.

[0053] Example 2

[0054] Take the sulfuric acid process titanium dioxide slurry with rod-shaped particle morphology treated with high-aluminum salts (the specific dosage of the salt treatment agent is: 0.29% Al2O3, 0.21% K2O, 0.25% P2O5, calculated based on the mass fraction of titanium dioxide in the metatitanic acid before calcination), with a concentration of 300 g / L, and start stirring; adjust the pH of the slurry to 9 with dilute NaOH solution, the addition time of NaOH is 10 min, and homogenize for 10 min; add 1.5% of Na2SiO3, the addition time is 10 min, and then homogenize for 5 min; add 2.6% of BaCl2, the addition time is 30 min, and then homogenize for 10 min; adjust the pH of the slurry to 7 with dilute H2SO4 solution, the addition time of H2SO4 is 10 min, and then homogenize for 10 min; add 0.5% of ZrOCl2 and 0.4% of (NaPO3)6 in parallel flow, the parallel flow addition time is 10 min, and then homogenize for 10 min; raise the temperature to 75 °C and keep warm for 2 h; adjust the pH of the slurry to 9.5 with dilute NaOH solution, the addition time of dilute NaOH is 10 min, and then homogenize for 10 min; add 1.5% of MgSO4 and NaOH solution in parallel flow, maintain the parallel flow pH at 9.5, the parallel flow addition time is 20 min, and then homogenize for 10 min; use 1.5% of NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 9.5, the parallel flow addition time is 20 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.5 with dilute H2SO4 solution; after the above slurry is washed with water, it is calcined at 500 °C for 2 h, and then air pulverized to obtain the finished titanium dioxide product.

[0055] Example 3

[0056] Take the sulfuric acid process titanium dioxide slurry with rod-shaped particle morphology after high-aluminum salt treatment (the specific dosage of the salt treatment agent is: 0.25% Al2O3, 0.21% K2O, 0.25% P2O5, calculated based on the mass fraction of titanium dioxide in metatitanic acid before calcination), with a concentration of 300 g / L, and start stirring; adjust the pH of the slurry to 9.5 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; add 1.5% Na2SiO3, add it for 10 min, and then homogenize for 5 min; add 2.6% BaCl2, add it for 30 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.8 with dilute H2SO4 solution, add H2SO4 for 10 min, and then homogenize for 10 min; add 0.4% ZrOCl2 and 0.3% (NaPO3)6 in parallel flow, add them in parallel flow for 10 min, and then homogenize for 10 min; heat up to 75 °C and keep warm for 2 h; adjust the pH of the slurry to 10 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; add 1.0% MgSO4 and NaOH solution in parallel flow, maintain the parallel flow pH at 10, add them in parallel flow for 20 min, and then homogenize for 10 min; add 1.5% NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 10, add them in parallel flow for 20 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.3 with dilute H2SO4 solution; after the above slurry is washed with water, it is calcined at 400 °C for 2.5 h and then air pulverized to obtain the finished titanium dioxide product.

[0057] Comparative Example 1 (the base material is spherical)

[0058] Take the sulfuric acid process titanium dioxide slurry with spherical particle morphology (the specific dosage of salt treatment agent is: Al2O3 0.05%, K2O 0.21%, P2O5 0.25%, calculated based on the mass fraction of titanium dioxide in metatitanic acid before calcination), with a concentration of 350 g / L, and start stirring; adjust the pH of the slurry to 9.5 with dilute NaOH solution, add it over 10 min, and then homogenize for 10 min; add 1% of Na2SiO3 over 10 min, and then homogenize for 5 min; add 1.7% of BaCl2 over 20 min, and then homogenize for 10 min; adjust the pH of the slurry to 7.2 with dilute H2SO4 solution, add H2SO4 over 10 min, and homogenize for 10 min; add 0.3% of ZrOCl2 and 0.25% of (NaPO3)6 in parallel flow, add them in parallel flow over 10 min, and then homogenize for 10 min; heat up to 80 °C and keep warm for 1.5 h; adjust the pH of the slurry to 10 with dilute NaOH solution, add it over 10 min, and then homogenize for 10 min; add 2% of MgSO4 and NaOH solution in parallel flow, maintain the parallel flow pH at 10, add it over 30 min, and homogenize for 10 min; then add 2% of NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 10, add it in parallel flow over 30 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.3 with dilute H2SO4 solution; after the above slurry is washed with water, it is calcined at 500 °C for 3 h and then air pulverized to obtain the finished titanium dioxide product.

[0059] Comparative Example 2 (conventional SiO2 coating, without calcination)

[0060] Take the sulfuric acid process titanium white slurry with rod-shaped particle morphology treated with high-aluminum salt (the specific dosage of the salt treatment agent is: 0.25% Al2O3, 0.21% K2O, 0.25% P2O5, calculated as the mass fraction of titanium dioxide in metatitanic acid before calcination), with a concentration of 300 g / L, and start stirring; adjust the pH of the slurry to 9.5 with dilute NaOH solution, add it for 10 min, and then homogenize for 10 min; add 1.5% Na2SiO3, add it for 10 min, and then homogenize for 5 min; adjust the pH of the slurry to 6.8 with dilute H2SO4 solution, add H2SO4 for 10 min, and then homogenize for 10 min; add 0.4% ZrOCl2 and 0.3% (NaPO3)6 in parallel flow, add it in parallel flow for 10 min, and then homogenize for 10 min; heat up to 75 °C and keep warm for 2 h; adjust the pH of the slurry to 10 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; add 1.0% MgSO4 and NaOH solution in parallel flow, maintain the parallel flow pH at 10, add it in parallel flow for 20 min, and then homogenize for 10 min; 1.5% NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 10, add it for 20 min, and homogenize for 10 min; adjust the pH of the slurry to 6.3 with dilute H2SO4 solution; after the above slurry is washed with water, flash evaporation and steam powdering are carried out to obtain the titanium dioxide finished product.

[0061] Comparative Example 3

[0062] Conventional silicon-zirconium-aluminum coating.

[0063] Take the sulfuric acid process titanium white slurry with rod-shaped particle morphology treated with high-aluminum salt (the specific dosage of the salt treatment agent is: 0.25% Al2O3, 0.21% K2O, 0.25% P2O5, calculated as the mass fraction of titanium dioxide in metatitanic acid before calcination), with a concentration of 300 g / L, and start stirring; adjust the pH of the slurry to 9.5 with dilute NaOH solution, add it for 10 min, and then homogenize for 10 min; add 1.5% Na2SiO3, add it for 10 min, and then homogenize for 5 min; adjust the pH of the slurry to 6.8 with dilute H2SO4 solution, add it for 10 min, and homogenize for 10 min; add 0.4% ZrOCl2 and 0.3% (NaPO3)6 in parallel flow, add it in parallel flow for 10 min, and then homogenize for 10 min; heat up to 75 °C and keep warm for 2 h; adjust the pH of the slurry to 8 with dilute NaOH solution, add NaOH for 10 min, and then homogenize for 10 min; use 1.5% NaAlO2 and H2SO4 solution in parallel flow, maintain the parallel flow pH at 10, add it in parallel flow for 20 min, and then homogenize for 10 min; adjust the pH of the slurry to 6.3 with dilute H2SO4 solution; after the above slurry is washed with water, flash evaporation and steam powdering are carried out to obtain the titanium dioxide finished product.

[0064] Comparative Example 4

[0065] Foreign competitor T. Prepare the coating according to the commonly used aqueous infrared coating formula in the market, coat it on the surface of a special jar, and place it under sunlight for 4 h, where the outdoor temperature is 42.3 - 44.8 °C. The internal temperature of the jar is shown in Table 1.

[0066] Table 1

[0067]

[0068] As can be seen from the above table, the reflection performance of the titanium dioxide obtained in the examples of the present application is significantly better than that of the comparative examples. Moreover, after measurement, other properties of the titanium dioxide provided in the examples of the present application, such as weather resistance, hiding power, and hue, can also meet the requirements for use in coatings.

[0069] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they learn the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments as well as all changes and modifications that fall within the scope of the present invention. Obviously, those skilled in the art can make various changes and variations to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A preparation method of infrared reflective titanium dioxide, characterized in that, It includes the following steps: S1. Using a titanium dioxide-based material slurry with non-spherical particle morphology, first add a soluble silicate source and a soluble barium source for reaction to generate a barium silicate hydrate precipitate, which deposits on the surface of the titanium dioxide substrate; S2. Add a soluble zirconium source and a soluble phosphate source for reaction to generate a zirconium phosphate precipitate, which deposits on the surface of the barium silicate hydrate deposition layer; S3. Raise the temperature to hydrolyze the barium silicate hydrate deposition layer on the surface of the titanium dioxide substrate; S4. Add a soluble magnesium source and a soluble aluminum source for the deposition of magnesium hydroxide and aluminum hydroxide; S5. Calcinate to make the deposited magnesium hydroxide and aluminum hydroxide calcine to form magnesium oxide and aluminum oxide.

2. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that the titanium dioxide-based material slurry is a sulfuric acid process titanium white slurry; the salt treatment agent used for the titanium dioxide substrate in the salt treatment preparation process in step S1 includes an aluminum salt, and the dosage of the aluminum salt is 0.25-0.35% of the mass of titanium dioxide in metatitanic acid before calcination.

3. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that the addition amount of the soluble silicate source in step S1, calculated as silicon dioxide, is 1.0-1.5% of the mass of the titanium dioxide substrate; the addition amount of the soluble barium source, calculated as barium oxide, is 1.7-2.6% of the mass of the titanium dioxide substrate.

4. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that before adding the soluble silicate source and the soluble barium source in step S1, first adjust the pH of the titanium dioxide-based material slurry to 9.0-9.

5.

5. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that before adding the soluble zirconium source and the soluble phosphate source in step S2, first adjust the pH of the slurry to 6.8-7.2 to prevent the premature hydrolysis of barium silicate hydrate; the addition amount of the soluble zirconium source in step S2, calculated as zirconium dioxide, is 0.3-0.5% of the mass of the titanium dioxide substrate; the addition amount of the soluble phosphate source, calculated as phosphorus pentoxide, is 0.25%-0.4% of the mass of the titanium dioxide substrate.

6. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that in step S3, raise the temperature to 75-80°C and keep it warm for 1.5-2 h.

7. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that the addition amount of the soluble magnesium source in step S4, calculated as magnesium oxide, is 1.0-2.0% of the mass of the titanium dioxide substrate; the addition amount of the soluble aluminum source, calculated as aluminum oxide, is 1.5-2.0% of the mass of the titanium dioxide substrate.

8. The method for preparing an infrared-reflective titanium dioxide according to claim 1, characterized in that before adding the soluble magnesium source and the soluble aluminum source in step S4, first adjust the pH of the slurry to 9.5-10; when adding the soluble magnesium source, a certain amount of pH regulator is also added in parallel, and the addition amount of the pH regulator is based on maintaining the parallel-flow pH at 9.5-10; When adding the soluble aluminum source, a certain amount of pH regulator is added in parallel flow at the same time, and the addition amount of the pH regulator is based on maintaining the parallel flow pH at 9.5 to 10.

9. The method for preparing infrared reflective titanium dioxide according to claim 1, characterized in that In step S5, before calcination, the pH of the slurry is first adjusted to 6.3 to 6.5, and after calcination, air pulverization is carried out to obtain the finished titanium dioxide product.

10. The method for preparing infrared reflective titanium dioxide according to claim 1, characterized in that The calcination temperature in step S5 is 400 to 500 °C, and the time is 2 to 3 h.

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