High-weather-resistance titanium dioxide as well as preparation method and application thereof

Abstract

The invention discloses high-weather-resistance titanium dioxide as well as a preparation method and application thereof, and belongs to the technical field of titanium dioxide preparation. Silicon coating, aluminum coating and organic coating are carried out on the pretreated titanium dioxide, the silicon coating process and the aluminum coating process are carried out in a parallel flow mode, a formed compact silicon layer can effectively block the direct action of ultraviolet rays and titanium dioxide crystal lattices, the photocatalytic activity is greatly reduced, an aluminum layer and the silicon layer are complementary, and the photocatalytic activity is greatly improved. The surface charge of the titanium dioxide is adjusted to improve the weather resistance and the water dispersibility, finally organic coating is performed, and the high-weather-resistance titanium dioxide with relatively improved comprehensive performance is prepared through a specific coating process and conditions in the invention.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium dioxide preparation, and particularly relates to a high-weatherability titanium dioxide, a preparation method and application thereof. BACKGROUND

[0002] Titanium dioxide (TiO2) is the most widely used white inorganic pigment in the world, and occupies a core position in many industries such as coatings, plastics and papermaking due to its excellent color reduction and hiding power. Different application fields have different performance requirements for titanium dioxide, such as high weather resistance to resist outdoor environmental erosion for coatings, and good dispersibility to ensure product uniformity for plastics. Among them, weather resistance is a key indicator to measure the quality of titanium dioxide, which directly determines its stability under long-term light, rain erosion and oxidation. Therefore, improving the weather resistance of titanium dioxide has become the focus of industry technology competition. At present, the main way to improve the weather resistance of titanium dioxide is coating treatment, that is, coating one or more protective films on the surface of titanium dioxide particles, which is divided into inorganic coating, organic coating and composite coating. Inorganic coating often uses oxides such as aluminum oxide (Al2O3), silicon oxide (SiO2) and zirconium oxide (ZrO2) to form a dense film on the surface of particles through hydrolysis or precipitation reaction, block ultraviolet rays and neutralize surface active sites; organic coating uses silane coupling agent, titanium ester coupling agent and other organic matters to improve the compatibility with resin binder and reduce the photocatalytic activity; composite coating combines the advantages of the two, first inorganic and then organic, to realize function complementation.

[0003] For example, Chinese patent CN106947296A discloses a high-weatherability titanium dioxide and a preparation method thereof, which comprises the following steps: a, adding a dispersing agent to titanium dioxide slurry, then adding aluminum raw material, and aging to obtain aluminum oxide coated titanium dioxide slurry; b, adding acid to the titanium dioxide slurry obtained in step a to adjust the pH value to 0.1-3.0, then adding sodium silicate and acid, and aging; c, adding aluminum raw material to the titanium dioxide slurry obtained in step b, and aging, then filtering, washing, drying, ultrafine grinding and organic treatment to obtain high-weatherability titanium dioxide.

[0004] CN112538283A discloses a preparation method of high-weather-resistant and high-hiding titanium white powder, comprising the following steps: a, crushing titanium dioxide primary product to form a slurry, adding sodium silicate, and adjusting the pH value to 9.0-11.0; b, heating the slurry to 80-100 DEG C, adding sodium silicate solution, and adding an acidic aluminum-containing compound solution in a flow manner to keep the pH value of the slurry at 8.0-10.0, and aging; c, cooling the aged slurry to 40-50 DEG C, adding sodium silicate solution, and adding an acidic aluminum-containing compound in a flow manner to keep the pH value of the slurry at 8.0-10.0, and aging; d, adjusting the pH value of the slurry to 4.0-6.5 by using an acidic aluminum-containing compound, and aging; e, adjusting the pH value of the slurry to 7.0-8.0 by using an alkaline aluminum-containing compound, and filtering, washing with water, drying, and crushing to obtain the product.

[0005] However, the film formed by the traditional hydrolysis method in the inorganic coating technology is prone to uneven thickness and high porosity, resulting in insufficient ultraviolet shielding effect; although the organic coating can enhance the compatibility, some coupling agents have poor temperature resistance and are prone to decomposition and failure at high temperatures; the composite coating process is complex, the cost is high, and the bonding force between the multiple layers of the film is limited, which is prone to peeling after long-term use.

[0006] In summary, the titanium white powder coating treatment technology includes inorganic, organic and composite coating, but there are still problems such as film defects, poor material stability, high cost, environmental risk, poor weather resistance and other problems to be solved in the existing coating process. SUMMARY

[0007] In view of the above problems, the present application provides a high-weather-resistant titanium white powder and a preparation method and application thereof. First, sodium silicate and dilute sulfuric acid are added in a flow manner, then aluminum sulfate and sodium metaaluminate are added in a flow manner, inorganic coating is carried out, and then organic coating is carried out, to obtain titanium white powder with high whiteness and good weather resistance.

[0008] The present application provides a high-weather-resistant titanium white powder, the particle size (D50) of the high-weather-resistant titanium white powder is 0.35-0.4 μm, the hiding power (latex base) is 83-84%, the oil absorption is 18-18.5 g / 100 g, the water dispersibility is <25 μm, and the color reduction power is 2060-2080. The color difference change ΔE of the high-weather-resistant titanium white powder before and after aging for 168 h is 0.95-1.2, the gloss change ΔGU at 20° is -62 to -64, the gloss change ΔGU at 60° is -72 to -75, and the gloss change ΔGU at 85° is -15 to -17. The L value of the oil phase whiteness of the high-weather-resistant titanium white powder is 95.8-96, the a value is -1.10 to -1.30, and the b value is 1.30 to 1.80. The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.7-98.9, an a value of -0.40 to -0.55, and a b value of 1.10-1.60.

[0009] The present invention also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve rutile titanium dioxide and sodium silicate in demineralized water, grind them, dilute with demineralized water, and then sieve to obtain a premixed slurry; Step 2: After heating the premixed slurry, add sodium silicate aqueous solution and dilute sulfuric acid in a co-current flow, then let it stand for aging to obtain aged slurry one; Step 3: After cooling the first aged slurry, adjust the pH with NaOH solution, and add aluminum sulfate solution and sodium aluminate solution. Continue to let it stand for aging to obtain the second aged slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed and then dried to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane and then gasified to obtain the high weather-resistant titanium dioxide.

[0010] Furthermore, the mass of sodium silicate in step 1 is 0.3-0.45 wt. of the mass of rutile titanium dioxide.

[0011] Further, in step 1, the mass ratio of the rutile titanium dioxide to the desalinated water is (1:1.5) to (1:2).

[0012] Furthermore, in step 1, the grinding speed is 200-300 rpm, and the grinding time is 15-45 min.

[0013] Further, in step 1, the concentration of the rutile titanium dioxide is diluted to 250-400 g / L.

[0014] Furthermore, the sieving in step 1 uses a 300-350 mesh sieve.

[0015] Furthermore, the temperature for heating in step 2 is 80°C.

[0016] Furthermore, the concentration of the sodium silicate aqueous solution in step 2 is 100-150 g / L.

[0017] Furthermore, the sodium silicate content in the sodium silicate aqueous solution in step 2 is 3-5 wt.% of the rutile titanium dioxide in the system at this time.

[0018] Furthermore, the concentration of the dilute sulfuric acid in step 2 is 100-200 g / L.

[0019] Furthermore, the co-flow time in step 2 is 3-4 hours, and the pH during co-flow is 8-8.5.

[0020] Furthermore, in step 2, the pH of the aging process is 6-7.5, and the aging time is 2-3 hours.

[0021] Furthermore, in step 2, the pH is adjusted using 100-120 g / L dilute sulfuric acid during the aging process.

[0022] Furthermore, the cooling temperature in step 3 is 70-75℃.

[0023] Furthermore, the concentration of the NaOH solution in step 3 is 100-120 g / L.

[0024] Furthermore, in step 3, the pH is adjusted to 9-9.5.

[0025] Furthermore, in step 3, the concentration of the aluminum sulfate solution is 100-120 g / L, and the concentration of the sodium aluminate solution is 100-120 g / L.

[0026] Furthermore, in step 3, the amount of aluminum sulfate added to the aluminum sulfate solution is 1-1.5 wt. of the mass of the rutile titanium dioxide in the system at this time.

[0027] Furthermore, in step 3, the amount of sodium aluminate added to the sodium aluminate solution is 1-1.5 wt. of the mass of the rutile titanium dioxide in the system at this time.

[0028] Furthermore, the pH during co-current flow in step 3 is 9-9.5.

[0029] Furthermore, the concurrent flow time in step 3 is 2-3 hours.

[0030] Furthermore, in step 3, the pH of the aging process is 6-7, and the aging time is 1-1.5 hours.

[0031] Furthermore, in step 3, the pH is adjusted using 100-120 g / L dilute sulfuric acid during the aging process.

[0032] Furthermore, the washing desalinated water used in step 4.

[0033] Furthermore, in step 4, the conductivity of the filtrate after washing is ≤100 μs / cm.

[0034] Furthermore, the drying temperature in step 4 is 100-120℃, and the drying time is 10-12h.

[0035] Furthermore, the amount of trimethylolethane added in step 4 is 0.3-0.5 wt. of the mass of rutile titanium dioxide in the system at this time.

[0036] Furthermore, in step 4, the stirring speed is 300-500 rpm, and the stirring time is 30-60 min.

[0037] Furthermore, the pressure of the gas powder in step 4 is 0.3-0.5 MPa.

[0038] The present invention also provides a water-based coating, which is prepared from the high weather-resistant titanium dioxide as a raw material.

[0039] The beneficial effects of this invention are: 1. In this invention, sodium silicate is first added as a dispersant. The silicate ions in sodium silicate form a stable double electric layer on the surface of titanium dioxide. The electrostatic repulsion effectively inhibits particle agglomeration and avoids interference from excessive dispersant residue in subsequent coating. After sand milling, the titanium dioxide particles are fully deagglomerated while the particle size distribution is precisely controlled to obtain an optimal particle size close to visible light scattering with a D50 of about 0.4 μm. After dilution, the uniformity of particle dispersion is ensured, and a suitable environment is provided for the mass transfer of reactants in the subsequent coating process. Finally, large particles of titanium dioxide in the system are removed by sieving. 2. The pretreated titanium dioxide is first coated with silicon. Sodium silicate is added under coating conditions of 70-80℃ to provide energy conditions for the orderly arrangement of silicon-oxygen tetrahedra. At this temperature, silicon can form a dense silicon layer of moderate thickness, which can effectively block the direct interaction between ultraviolet rays and the titanium dioxide lattice, greatly reducing photocatalytic activity. The addition of sodium silicate and dilute sulfuric acid can avoid the agglomeration of silica gel caused by local excessive alkali, ensuring uniform coating of silicon layer. Then, aging at pH 6-7.5 can promote the dehydration and condensation of silicon layer and enhance its bonding force with the surface of titanium dioxide. 3. After silicon coating, the titanium dioxide is further coated with an inorganic aluminum film. At 70-75℃, aluminum sulfate and sodium aluminate are mixed with the titanium dioxide in a co-current manner. With a coating environment of pH 9-9.5, aluminum ions are uniformly deposited in the boehmite phase. The aluminum layer and the silicon layer complement each other, which adjusts the surface charge of the titanium dioxide and improves its weather resistance and water dispersibility. After the coating is completed, aging is carried out at pH 6-7.5 to form a dense aluminum layer, reduce porosity, and enhance the protection of the titanium dioxide core. 4. Finally, the inorganic-coated titanium dioxide is mixed with organic compounds for organic coating. Before organic coating, the residual salt in the titanium dioxide is washed to avoid ion migration during aging, which can cause color difference. After organic coating, the powder is aerated, which can break up soft agglomerates while avoiding damage to the inorganic coating layer, and finally obtains high weather-resistant titanium dioxide with relatively improved comprehensive performance. Attached Figure Description

[0040] Figure 1 This is a scanning electron microscope image of the high weather-resistant titanium dioxide described in Example 1. Detailed Implementation

[0041] The invention will be described in detail below with reference to the embodiments: This invention provides a high weather-resistant titanium dioxide, which is inorganically and organically coated in a specific manner, greatly improving the weather resistance and whiteness of the titanium dioxide.

[0042] Example 1 This embodiment provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.40 μm, a hiding power (latex base) of 83.5%, an oil absorption of 18 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2060. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 0.98. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -62.1, at 60° is -74.3, and at 85° is -15.8. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.98, an a value of -1.30, and a b value of 1.36; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.82, an a value of -0.53, and a b value of 1.12.

[0043] This embodiment also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 300rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 300g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 3h. During the co-flow, maintain the pH at 8.5. Then adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 2h to obtain aged slurry one. Step 3: After cooling the first aging slurry to 75℃, adjust the pH to 9.2 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. Maintain the pH at 9 during the parallel flow process for 2 hours. Then, continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 1 hour to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) at 300rpm for 30min, and then aerated at 0.3MPa to obtain the high weather-resistant titanium dioxide.

[0044] Example 2 This embodiment provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.39 μm, a hiding power (latex base) of 83.2%, an oil absorption of 18.2 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2080. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 1.2. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -63.1, at 60° is -72.3, and at 85° is -15.4. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.97, an a value of -1.28, and a b value of 1.45; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.88, an a value of -0.50, and a b value of 1.29.

[0045] This embodiment also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (added at 0.45wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 200rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 250g / L. After sieving with a 300-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 3.5wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 4 hours. During the co-flow process, maintain the pH at 8. Then adjust the pH to 7 with 100g / L dilute sulfuric acid and let it stand for 2 hours to obtain aged slurry one. Step 3: After cooling the first aging slurry to 75℃, adjust the pH to 9 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. Maintain the pH at 9 during the parallel flow process for 2 hours. Then, continue to adjust the pH to 6.5 with 100g / L dilute sulfuric acid and let it stand for aging for 1.5 hours to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 115℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is mixed with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and stirred at 500rpm for 30min. Then, it is aerated at 0.5MPa to obtain the high weather-resistant titanium dioxide.

[0046] Example 3 This embodiment provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.39 μm, a hiding power (latex base) of 83.1%, an oil absorption of 18.4 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2060. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 1.2. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -62.7, at 60° is -73.5, and at 85° is -16.8. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.80, an a value of -1.13, and a b value of 1.76; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.75, an a value of -0.43, and a b value of 1.59.

[0047] This embodiment also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 200rpm for 45min, dilute with demineralized water to a titanium dioxide concentration of 350g / L. After sieving with a 350-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 4wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 3 hours, maintaining the pH at 8.5 during the co-flow process. Then, adjust the pH to 7 with 100g / L dilute sulfuric acid and let it stand for aging for 2 hours to obtain aged slurry one. Step 3: After cooling the first aging slurry to 70℃, adjust the pH to 9.5 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. During the parallel flow, maintain the pH at 9 and the parallel flow time is 2h. Then continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 1h to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 12h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is mixed with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and stirred at 300rpm for 60min. Then, it is aerated at 0.4MPa to obtain the high weather-resistant titanium dioxide.

[0048] Example 4 This embodiment provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.37 μm, a hiding power (latex base) of 83.2%, an oil absorption of 18.5 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2080. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 1.1. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -62.3, at 60° is -72.8, and at 85° is -15.3. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.94, an a value of -1.22, and a b value of 1.63; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.83, an a value of -0.50, and a b value of 1.50.

[0049] This embodiment also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (added at 0.4wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 200rpm for 30min, dilute with demineralized water to a titanium dioxide concentration of 400g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 5wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 3 hours, maintaining the pH at 8.5 during the co-flow process. Then, adjust the pH to 7 with 100g / L dilute sulfuric acid and let it stand for 2 hours to obtain aged slurry one. Step 3: After cooling the first aging slurry to 70℃, adjust the pH to 9.2 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. During the parallel flow, maintain the pH at 9.5 for 3 hours. Then, continue to adjust the pH to 7 with 100g / L dilute sulfuric acid and let it stand for aging for 1 hour to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is mixed with trimethylolethane (the amount added is 0.5wt.% of the mass of the rutile titanium dioxide in the system at this time) and stirred at 300rpm for 30min. Then, it is aerated at 0.4MPa to obtain the high weather-resistant titanium dioxide.

[0050] Comparative Example 1 This comparative example provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.40 μm, a hiding power (latex base) of 80.1%, an oil absorption of 17.9 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2020. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 3.0. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -81.4, at 60° is -89.4, and at 85° is -48.2. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.52, an a value of -1.14, and a b value of 1.61; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.38, an a value of -0.47, and a b value of 1.50.

[0051] This comparative example also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 300rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 300g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After cooling the premixed slurry to 80℃, adjust the pH to 9.2 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. Maintain the pH at 9 during the parallel flow process for 2 hours. Then, continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 1 hour to obtain aged slurry II. Step 3: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) at 300rpm for 30min, and then aerated at 0.3MPa to obtain the high weather-resistant titanium dioxide.

[0052] Comparative Example 2 This comparative example provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.45 μm, a hiding power (latex base) of 79.8%, an oil absorption of 19.2 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2060. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 2. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -80.8, at 60° is -88.8, and at 85° is -42.8. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.61, an a value of -1.21, and a b value of 1.58; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.46, an a value of -0.52, and a b value of 1.46.

[0053] This comparative example also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 300rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 300g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid and run for 3h. Then adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for 2h to obtain aged slurry one. Step 3: After cooling the first aging slurry to 75℃, adjust the pH to 9.2 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. Maintain the pH at 9 during the parallel flow process for 2 hours. Then, continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 1 hour to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) at 300rpm for 30min, and then aerated at 0.3MPa to obtain the high weather-resistant titanium dioxide.

[0054] Comparative Example 3 This comparative example provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.43 μm, a hiding power (latex base) of 79.6%, an oil absorption of 19.1 g / 100 g, a water dispersibility of <25 μm, and a tinting strength of 2040. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 1.98. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -82.7, at 60° is -88.2, and at 85° is -37.1. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.65, an a value of -1.21, and a b value of 1.56; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.52, an a value of -0.53, and a b value of 1.45.

[0055] This comparative example also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 300rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 300g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 80°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 2 hours. During the co-flow process, maintain the pH at 8.5. Then adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 2 hours to obtain aged slurry one. Step 3: After cooling the first aging slurry to 75℃, adjust the pH to 9.2 with 100g / L NaOH solution, and add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in parallel flow. Maintain the pH at 9 during the parallel flow process for 2 hours. Then, continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 1 hour to obtain the second aging slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) at 300rpm for 30min, and then aerated at 0.3MPa to obtain the high weather-resistant titanium dioxide.

[0056] Comparative Example 4 This comparative example provides a high weather-resistant titanium dioxide with a particle size (D50) of 0.42 μm, a hiding power (latex base) of 80.2%, an oil absorption of 19.1 g / 100 g, a water dispersibility of <40 μm, and a tinting strength of 2060. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 1.9. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -80.2, at 60° is -88.9, and at 85° is -40.2. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.63, an a value of -1.23, and a b value of 1.63; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.50, an a value of -0.54, and a b value of 1.52.

[0057] This comparative example also provides a method for preparing the high weather-resistant titanium dioxide, comprising the following steps: Step 1: Dissolve 755g of rutile titanium dioxide and sodium silicate (0.3wt.% of the mass of the rutile titanium dioxide) in 1250g of demineralized water. After milling at 300rpm for 15min, dilute with demineralized water to a titanium dioxide concentration of 300g / L. After sieving with a 325-mesh sieve, a premixed slurry is obtained. Step 2: After heating the premixed slurry to 75°C, add 100g / L sodium silicate aqueous solution (the amount of sodium silicate added is 3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L dilute sulfuric acid in a co-flow for 3h. During the co-flow, maintain the pH at 8.5. Then adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for aging for 2h to obtain aged slurry one. Step 3: After cooling the first aged slurry to 75°C, adjust the pH to 9.2 with 100g / L NaOH solution. Then, add 100g / L aluminum sulfate solution (the amount of aluminum sulfate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) and 100g / L sodium aluminate solution (the amount of sodium aluminate added is 1.3wt.% of the mass of the rutile titanium dioxide in the system at this time) in a continuous flow. Maintain the pH at 9 during the continuous flow for 2 hours. Then, continue to adjust the pH to 6 with 100g / L dilute sulfuric acid and let it stand for 1 hour to obtain the second aged slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed with demineralized water until the conductivity of the filtrate is ≤100μs / cm. Then, it is dried at 105℃ for 10h to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane (the amount added is 0.3wt.% of the mass of the rutile titanium dioxide in the system at this time) at 300rpm for 30min, and then aerated at 0.3MPa to obtain the high weather-resistant titanium dioxide.

[0058] Table 1. Performance of titanium dioxide in the embodiments and comparative examples of the present invention.

[0059] Table 2 Comparison of gloss changes in the embodiments and comparative examples of the present invention.

[0060] Table 3 Comparison of oil phase whiteness between embodiments and comparative examples of the present invention.

[0061] Table 4 Comparison of whiteness of dry powder in embodiments and comparative examples of the present invention.

[0062] As shown in Table 1, the titanium dioxide of this invention has better hiding power, moderate oil absorption, better water dispersibility, moderate tinting strength, and smaller color difference changes after aging. Compared with the comparative examples, the titanium dioxide of this application shows less change in gloss after aging, and the difference between the whiteness of the oil phase and the whiteness of the dry powder of the titanium dioxide prepared in this invention is small. Comparative Example 1 did not undergo silicon coating, Comparative Example 2 used a serial flow method for silicon coating, Comparative Example 3 had a shortened parallel flow time for silicon coating, Comparative Example 4 had a lower temperature for silicon coating, and the aluminum coating process was serial flow. It can be seen that the performance of the titanium dioxide in the comparative examples in the table is reduced to varying degrees, which also illustrates the advantage of the synergistic effect of each step in this invention. Figure 1 Electron micrograph of titanium dioxide, showing clear material boundaries.

[0063] The standard for testing the hiding power described in this invention is ISO 2814. The sample is prepared in a latex state (the sample is prepared with dispersant, defoamer, cellulose, styrene-acrylic emulsion, ammonia, and distilled water; the preparation method is not limited, and any existing titanium dioxide preparation process can be used), coated onto a black-and-white contrast card, and after drying, the reflectance of the latex is measured using a spectrophotometer. The hiding power is calculated as: (Reflectance of black substrate / Reflectance of white substrate) × 100%. The test standard for oil absorption is ISO 787-5. The method involves gradually adding refined linseed oil to titanium dioxide and continuously grinding and mixing it until a uniform, plastic paste-like mixture is formed that is neither broken nor sticky to the container wall. The mass of oil consumed is then recorded. The test method for water dispersibility is as follows: disperse the sample in 1000 ml of deionized water, mix evenly, and then sieve. Where <25 μm refers to the particle size that has not passed through the sieve. The test conditions for the whiteness of the oil phase and the whiteness of the dry powder were compared using the Lab color space; The test standard for tinting strength is GB / T 1706-2006; The aging test conditions in this invention are as follows: the sample is placed under a UVB-313EL ultraviolet lamp in sequence, irradiated with an intensity of 0.76kW for 8 hours, sprayed with water for 15 minutes, and then cooled at 25°C for 3 hours and 45 minutes. The above process is repeated for 168 hours, and the color difference and gloss of the sample are observed. The test standard for the color difference change is to compare the color difference before and after aging using the Lab color space. The calculation method for ΔE is = [(ΔL)² + (Δa)² + (Δb)²]^(1 / 2), where ΔL, Δa, and Δb are the differences in L, a, and b values ​​between the two samples, respectively. The gloss test standard is GB / T 9754, and the gloss change ΔGU is the difference in gloss between the sample after aging and before aging.

[0064] As can be seen from the above, the high weather-resistant titanium dioxide of the present invention has a wide range of applications, low cost, and a very high market prospect.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. A high weather-resistant titanium dioxide, characterized in that, The high weather-resistant titanium dioxide has a particle size of 0.35-0.4μm, a hiding power of 83-84%, an oil absorption of 18-18.5g / 100g, a water dispersibility of <25μm, and a tinting strength of 2060-2080. The color difference change ΔE of the high weather-resistant titanium dioxide before and after aging for 168 hours is 0.95-1.

2. The gloss change ΔGU of the high weather-resistant titanium dioxide at 20° is -62 to -64, at 60° it is -72 to -75, and at 85° it is -15 to -17. The high weather-resistant titanium dioxide oil phase whiteness has an L value of 95.8-96, an a value of -1.10 to -1.30, and a b value of 1.30 to 1.80; The whiteness of the high weather-resistant titanium dioxide dry powder has an L value of 98.7-98.9, an a value of -0.40 to -0.55, and a b value of 1.10-1.

60.

2. A method for preparing the high weather-resistant titanium dioxide according to claim 1, characterized in that, Includes the following steps: Step 1: Dissolve rutile titanium dioxide and sodium silicate in demineralized water, grind them, dilute with demineralized water, and then sieve to obtain a premixed slurry; Step 2: After heating the premixed slurry, add sodium silicate aqueous solution and dilute sulfuric acid in a co-current flow, then let it stand for aging to obtain aged slurry one; Step 3: After cooling the first aged slurry, adjust the pH with NaOH solution, and add aluminum sulfate solution and sodium aluminate solution. Continue to let it stand for aging to obtain the second aged slurry. Step 4: After the aged slurry is filtered twice, the filter cake is washed and then dried to obtain inorganic coated titanium dioxide. The inorganic coated titanium dioxide is stirred with trimethylolethane and then gasified to obtain the high weather-resistant titanium dioxide.

3. The preparation method according to claim 2, characterized in that, The mass of sodium silicate in step 1 is 0.3-0.45 wt. of the mass of rutile titanium dioxide.

4. The preparation method according to claim 2, characterized in that, The grinding speed in step 1 is 200-300 rpm, and the grinding time is 15-45 min.

5. The preparation method according to claim 2, characterized in that, The temperature for heating in step 2 is 80°C.

6. The preparation method according to claim 2, characterized in that, In step 2, the sodium silicate content in the sodium silicate aqueous solution is 3-5 wt.% of the rutile titanium dioxide in the system at this time.

7. The preparation method according to claim 2, characterized in that, The cooling temperature in step 3 is 70-75℃.

8. The preparation method according to claim 2, characterized in that, In step 3, the pH is adjusted to 9-9.

5.

9. The preparation method according to claim 2, characterized in that, In step 4, the washing process continues until the conductivity of the filtrate is ≤100 μs / cm.

10. A water-based coating, characterized in that, The water-based coating is prepared using the high weather-resistant titanium dioxide described in claim 1 as a raw material.

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