A highly weather-resistant titanium dioxide, its preparation method and application

Abstract

The present invention discloses a highly weather-resistant titanium dioxide and its preparation method and application, specifically belonging to the technical field of titanium dioxide preparation; the preparation method of the highly weather-resistant titanium dioxide includes the following steps: first, the surface of titanium dioxide is coated by the self-polymerization reaction of tannic acid to obtain tannic acid-titanium dioxide, and then 3-glycidoxypropyltriethoxysilane is used to couple and combine nano-barium sulfate on the surface of the modified highly weather-resistant titanium dioxide of tannic acid-titanium dioxide; the modified titanium dioxide provided by the present invention has good weather resistance and yellowing resistance, and has more excellent weather resistance compared with the highly weather-resistant titanium dioxide on the market.

Description

Technical Field

[0001] The present invention belongs to the technical field of titanium dioxide preparation, and particularly relates to a highly weather-resistant titanium dioxide and its preparation method and application. Background Art

[0002] In modern industry and daily life, the requirements for the weather resistance of materials in fields such as coatings, plastics, papers, cosmetics, and pharmaceuticals are getting higher and higher. Weather resistance refers to the ability of materials to resist adverse factors such as ultraviolet rays, oxidation, temperature changes, and microbial erosion in the natural environment.

[0003] Titanium dioxide (TiO 2 ) is widely used as a white pigment and photocatalyst, and is widely applied due to its high refractive index, chemical stability, and photocatalytic activity. However, titanium dioxide itself has photosensitivity and can undergo catalytic chemical reactions. When titanium dioxide is used in coatings and plastics, such reactions will cause the product color to turn yellow and the performance to decline, restricting its use in high-weather-resistance applications.

[0004] In order to improve the weather resistance of titanium dioxide, the existing method is to perform surface coating treatment on titanium dioxide, and coat metal oxide films such as silica, aluminum oxide, and zirconium dioxide on the surface of titanium dioxide particles to reduce the photoactivity of titanium dioxide and improve the weather resistance of the product. These methods have improved the performance of titanium dioxide to a certain extent, but there are still problems such as high cost, complex process, or limited effect.

[0005] The focus of the research of the present invention is to provide a simple preparation method to modify titanium dioxide. Through this innovative modification method, the stability and service life of titanium dioxide are significantly improved, while maintaining or enhancing its original optical and chemical properties. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a titanium dioxide with high weather resistance and its preparation method. By simply coating and modifying the surface of titanium dioxide through a process flow, the problem that the weather resistance of the final product is poor due to the photosensitivity of titanium dioxide is overcome.

[0007] To achieve the above purpose, the present invention discloses the following technical solutions:

[0008] In the first aspect, the present invention provides a preparation method of highly weather-resistant titanium dioxide, comprising the following steps:

[0009] S1. Take nano-titanium dioxide and mix it with water to obtain a suspension, add a dispersant, and stir and mix evenly to obtain a titanium dioxide dispersion;

[0010] S2. Dissolve tris(hydroxymethyl)aminomethane in the titanium dioxide dispersion, and at the same time, slowly add the hydrochloric acid solution and mix evenly until the pH of the titanium dioxide dispersion is adjusted to 8.5 - 9 to obtain a mixed titanium dioxide dispersion;

[0011] S3. Add tannic acid to the mixed titanium dioxide dispersion obtained in step S2, stir at a temperature of 25 - 30 °C, react for 12 - 24 h, perform centrifugal solid-liquid separation, wash the separated solid residue A with water multiple times, dry it under vacuum, and grind it into powder to obtain tannic acid - titanium dioxide;

[0012] Tannic acid exists in the bark of trees and various fruits, has a wide source and low price, and is rich in active groups on its surface. It is a good functional material. Tannic acid reacts with the hydroxyl groups on the surface of titanium dioxide to form chemical bonds, realizing the surface modification of titanium dioxide. This modification can improve the dispersibility of titanium dioxide and enhance its compatibility with the substrate; tannic acid contains multiple phenolic hydroxyl groups, and these groups can capture free radicals, thereby improving the weather resistance of the material and reducing the damage to the material caused by ultraviolet rays and oxidation; the modified titanium dioxide (tannic acid - titanium dioxide) has better thermal stability and chemical stability, which helps to improve the quality and service life of the final product.

[0013] S4. Add tannic acid - titanium dioxide to an ethanol aqueous solution with a concentration ≥ 95 v / v%, add 3 - glycidoxypropyltriethoxysilane and dissolve it evenly. At a temperature of 60 - 70 °C, slowly add nano - barium sulfate, stir for 30 - 60 min, and after completion, perform centrifugal solid - liquid separation. Wash the separated solid residue B with water multiple times, dry it under vacuum, and grind it into powder to obtain modified high - weather - resistant titanium dioxide;

[0014] The mass ratio of the tannic acid - titanium dioxide, 3 - glycidoxypropyltriethoxysilane, and nano - barium sulfate is 1:(0.2 - 0.5):(1.6 - 1.8);

[0015] Barium sulfate is a white pigment with high whiteness, low abrasion index, low viscosity, and high stability, and it has excellent ultraviolet - blocking performance, good sun resistance and weather resistance. It is an ideal raw material to partially replace titanium dioxide. It can absorb harmful rays such as X - rays and gamma rays. Grafting barium sulfate onto the surface of titanium dioxide in a coupled form can improve the weather resistance of the final product. In addition, the addition of barium sulfate can change the rheological properties of the mixture.

[0016] Preferably, the nano - titanium dioxide is rutile - type titanium dioxide with a particle size of 200 - 300 nm.

[0017] Preferably, in step S1, nano-titanium dioxide is mixed with water to obtain a suspension with a material-to-water ratio of 1.2 - 2.0 g / L. The dispersant is added in an amount of 0.6 - 1.0 g / L, and the mixture is stirred and mixed evenly at room temperature and 200 - 300 r / min to obtain a titanium dioxide dispersion.

[0018] Preferably, in step S2, tris(hydroxymethyl)aminomethane is dissolved in the titanium dioxide dispersion in an amount of 1.0 - 1.2 g / L. Meanwhile, a hydrochloric acid solution with a concentration of 2.5 - 3.65 g / L is slowly added and mixed evenly until the pH of the titanium dioxide dispersion is adjusted to 8.5 - 9.

[0019] Preferably, in step S3, tannic acid is added to the mixed titanium dioxide dispersion in step S2 in an amount of 2 - 3 g / L, and the mixture is stirred at a rotation speed of 500 - 800 r / min and a temperature of 25 - 30 °C for 12 - 24 h for reaction.

[0020] Preferably, in step S4, tannic acid - titanium dioxide is added to an ethanol aqueous solution with a concentration ≥ 95 v / v%. At this time, the material-to-liquid ratio is 1.0 - 1.5 g / L, and 3 - glycidoxypropyltriethoxysilane is added. The mixture is stirred and dissolved evenly at room temperature and a rotation speed of 200 r / min for 30 - 60 min. Then the rotation speed is increased to 500 r / min, and the temperature is increased to 60 - 70 °C. Nano-barium sulfate is slowly added while stirring. After the addition is completed, the rotation speed is increased to 1000 r / min, and stirring is continued for 30 - 60 min.

[0021] Preferably, in steps S3 and S4, the water used for multiple washings is deionized water, and the washing is carried out until the conductivity of the aqueous solution of solid residue A ≤ 100 μS / cm and the conductivity of the aqueous solution of solid residue B ≤ 50 μS / cm.

[0022] More preferably, the dispersant is at least one of sodium hexametaphosphate, sodium dihydrogen phosphate, calcium silicate, and sodium silicate.

[0023] In a second aspect, the present invention provides a highly weather-resistant titanium dioxide prepared by the method described in the first aspect.

[0024] In a third aspect, the present invention provides the application of the highly weather-resistant titanium dioxide described in the second aspect in the preparation of coatings, paints, and / or plastics with high weather resistance.

[0025] The beneficial effects of the present invention:

[0026] 1. The modified titanium dioxide provided by the present invention has good weather resistance and yellowing resistance, and has more excellent weather resistance compared with the highly weather-resistant titanium dioxide on the market;

[0027] 2. The preparation method of the modified titanium dioxide provided by the present invention has a simple process flow, stable process, high production efficiency, low cost, and no pollution, which is conducive to the production and promotion of environmentally friendly and energy-saving materials. Detailed implementation manners

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0029] All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The following specific implementation manners further describe the present invention.

[0031] In the present invention:

[0032] Nano-titanium dioxide ① : It is rutile-type titanium dioxide with a particle size of 200 - 300 nm, purchased from Beijing Deke Island Gold Technology Co., Ltd.

[0033] Nano-titanium dioxide ② : It is rutile-type titanium dioxide with a particle size of 15 - 50 nm, purchased from Ningbo Jiweina New Materials Technology Co., Ltd.

[0034] Tannic acid: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0035] L-DOPA: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0036] Catechol: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0037] 3-Glycidoxypropyltriethoxysilane: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0038] Aminopropyltrimethoxysilane: Purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0039] Nano-barium sulfate: The particle size is 40 - 50 nm, and the specific surface area is 20 - 40 m 2 / g, purchased from Beijing Deke Island Gold Technology Co., Ltd.

[0040] Sodium hexametaphosphate: Purchased from Sichuan Lan Jian Chemical Industry (Group) Co., Ltd.

[0041] Sodium dihydrogen phosphate: Purchased from Sichuan Lan Jian Chemical Industry (Group) Co., Ltd.

[0042] Calcium silicate: Purchased from Shandong Linke Technology Co., Ltd.

[0043] Sodium silicate: purchased from Shandong Linke Technology Co., Ltd.;

[0044] The remaining raw materials and reagents are all commercially available.

[0045] Preparation of Examples 1-4:

[0046] Step (1): Take nano-titanium dioxide ① and mix it with water to obtain a suspension with a solid-liquid ratio of 1.2 - 2.0 g / L. Add a dispersant (sodium hexametaphosphate, sodium dihydrogen phosphate, calcium silicate, sodium silicate) at an addition amount of 0.6 - 1.0 g / L, and stir and mix evenly at normal temperature and 200 - 300 r / min to obtain a titanium dioxide dispersion;

[0047] Step (2): Dissolve tris(hydroxymethyl)aminomethane in the titanium dioxide dispersion at an addition amount of 1.0 - 1.2 g / L. At the same time, slowly add a hydrochloric acid solution with a concentration of 2.5 - 3.65 g / L and mix evenly until the pH of the solution is adjusted to 8.5 - 9. Add tannic acid at an addition amount of 2 - 3 g / L, stir at a rotation speed of 500 - 800 r / min and a temperature of 25 - 30 °C, and react for 12 - 24 h. Centrifuge for solid-liquid separation. The separated solid residue A is washed with deionized water multiple times until the conductivity of the aqueous solution of solid residue A ≤ 100 μS / cm, then vacuum dried and ground into powder to obtain titanium dioxide modified with tannic acid (tannic acid-titanium dioxide);

[0048] Step (3): Add tannic acid-titanium dioxide to an ethanol aqueous solution with a concentration ≥ 95 v / v%. At this time, the solid-liquid ratio is 1.0 - 1.5 g / L, and add 3-glycidoxypropyltriethoxysilane. Stir and dissolve evenly at normal temperature and a rotation speed of 200 r / min for 30 - 60 min. Then increase the rotation speed to 500 r / min and the temperature to 60 - 70 °C, and slowly add nano-barium sulfate while stirring. After the addition is completed, increase the rotation speed to 1000 r / min and continue stirring for 30 - 60 min. The mass ratio of tannic acid-titanium dioxide, 3-glycidoxypropyltriethoxysilane and nano-barium sulfate is 1:(0.2 - 0.5):(1.6 - 1.8). After completion, centrifuge for solid-liquid separation. The separated solid residue B is washed with deionized water multiple times until the conductivity of the aqueous solution of solid residue B ≤ 50 μS / cm, then vacuum dried and ground into powder to obtain modified titanium dioxide (barium sulfate-tannic acid-titanium dioxide).

[0049] Specific parameters are shown in Table 1.

[0050] Table 1 Preparation parameters of Examples 1-4

[0051]

[0052] Preparation of Comparative Examples 1-5

[0053] Comparative Example 1: Replace tannic acid with levodopa and catechol, with a mass ratio of 2:1 and an addition concentration of 2.5 g / L. The remaining steps are the same as in Example 2;

[0054] Comparative Example 2: Replace 3-glycidoxypropyltriethoxysilane in step (3) with aminopropyltrimethoxysilane. The remaining steps are the same as in Example 2;

[0055] Comparative Example 3: Replace the nano-titanium dioxide in step (1) ① with nano-titanium dioxide ② , and the remaining steps are the same as in Example 2;

[0056] Comparative Example 4: Adjust the mass ratio of tannic acid-titanium dioxide, 3-glycidoxypropyltriethoxysilane, and nano-barium sulfate in step (3) to 1:1:1. The remaining steps are the same as in Example 2;

[0057] Comparative Example 5: Replace the nano-barium sulfate in step (3) with nano-barium sulfate with an average particle size of 100 nm (commercially available). The remaining steps are the same as in Example 2.

[0058] Performance Test

[0059] Acid Solubility Rate Test:

[0060] Perform acid solubility rate tests on the modified titanium dioxide samples prepared in the examples and comparative examples. The acid solubility rate results are shown in Table 1.

[0061] The acid solubility rate test method is as follows: Add 0.2 g of titanium dioxide to 10 mL of 98% sulfuric acid, ultrasonically disperse for 1 minute, and then dissolve at 175 - 180 °C for 1 hour. After taking out the sample and cooling it to room temperature, add water to make the volume up to 100 mL, filter, pipette 10 mL of the filtrate, add 10 mL of 30% hydrogen peroxide solution, and dilute it to 100 mL with 10% sulfuric acid solution. Let it stand for 1 hour, measure the absorbance of the solution at 410 nm, and calculate the corresponding dissolved amount of titanium dioxide by referring to the standard curve.

[0062] Table 2 Acid Solubility Rates of Examples and Comparative Examples

[0063] Test sample Acid dissolution rate / % Example 1 5.16 Example 2 4.77 Example 3 5.03 Example 4 5.11 Comparative example 1 7.29 Comparative example 2 13.72 Comparative example 3 14.31 Comparative example 4 7.83 Comparative example 5 10.64

[0064] Artificial Accelerated Aging Test:

[0065] The coatings (resin: acrylic acid) of Examples 1-4 and Comparative Examples 1-5 were prepared, and aged in an artificial weathering chamber (ATLAS Ci3000 + xenon lamp weathering tester / fadeometer) for 2 months (1500 h). The aging results were expressed in terms of gloss loss rate and yellowness change, to evaluate the weather resistance of the modified titanium dioxide and compare it with high weather resistance titanium dioxide products on the market. The results are shown in Tables 3 and 4.

[0066] Table 3 Gloss loss rate of the coating film after artificial aging

[0067]

[0068] Note: Gloss loss rate / % = (L1 - L2) / L1 × 100%.

[0069] Table 4 Yellowness change of the coating film after artificial aging

[0070]

[0071] Note: Yellowness change = b1 - b2.

[0072] Result analysis:

[0073] According to the results in Tables 3 and 4, it can be seen that the coating films of Examples 1, 2, 3, and 4 showed lower gloss loss rate and yellowness change after artificial aging, indicating that the modified titanium dioxide provided by the present invention has good weather resistance and yellowing resistance, and has more excellent weather resistance compared with high weather resistance titanium dioxide on the market.

[0074] The coating films of Comparative Examples 1-5 had higher gloss loss rate and yellowness change after artificial aging, showing poorer weather resistance and yellowing resistance compared with Examples 1-4;

[0075] Comparing Example 2 with Comparative Example 1, it can be seen that when levodopa and catechol were used to replace tannic acid, the weather resistance of the modified titanium dioxide decreased. This may be because the coupling system formed by the polydopamine film formed by levodopa and catechol and the silane coupling agent "3-glycidoxypropyltriethoxysilane" is less stable than the coupling system formed by polytannic acid and 3-glycidoxypropyltriethoxysilane, resulting in a decrease in the weather resistance of the final product;

[0076] Comparing Example 2 with Comparative Example 2, it can be seen that when 3-glycidoxypropyltriethoxysilane was replaced with aminopropyltrimethoxysilane, the weather resistance of the final modified titanium dioxide was affected. This is because 3-glycidoxypropyltriethoxysilane has an epoxy group more than aminopropyltrimethoxysilane, and the coupling system formed with polytannic acid during the coupling process is more stable;

[0077] It can be seen from the comparison between Example 2 and Comparative Examples 3-5 that in the technical solution provided by the present invention, the configuration of nano-titanium dioxide, the microscopic size of titanium dioxide, the addition amount ranges of tannic acid-titanium dioxide, 3-glycidoxypropyltriethoxysilane and nano-barium sulfate, and the microscopic size of nano-barium sulfate are all key factors affecting the weather resistance of the modified titanium dioxide.

[0078] Finally, it should be noted that the above examples and comparative examples are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing highly weather-resistant titanium dioxide, characterized in that: The following steps are involved: S1. Mix nano-titanium dioxide and water to obtain a suspension, add a dispersant, and stir to mix evenly to obtain a titanium dioxide dispersion; S2. Tris(hydroxymethyl)aminomethane is dissolved in the titanium dioxide dispersion, and hydrochloric acid solution is slowly added and mixed until the pH of the titanium dioxide dispersion is adjusted to 8.5-9 to obtain a mixed titanium dioxide dispersion; S3. Take tannic acid and add it to the mixed titanium dioxide dispersion of step S2, stir at a temperature of 25-30 ° C, react for 12-24h, centrifuge solid-liquid separation, separate the solid residue A with water several times, vacuum dry, grind into powder to obtain tannic acid - titanium dioxide; S4. Take tannic acid-titanium dioxide and add it to an ethanol aqueous solution with a concentration of ≥95 v / v%, and add 3-glycidyloxypropyltriethoxysilane to dissolve evenly. At a temperature of 60-70 ° C, slowly add nano-barium sulfate and stir for 30-60 minutes. After completion, centrifuge for solid-liquid separation, and the separated solid slag B is washed with water several times, vacuum dried, and ground into powder to obtain modified high weather-resistant titanium dioxide; The mass ratio of tannic acid-titanium dioxide, 3-glycidyloxypropyltriethoxysilane and nano-barium sulfate is 1: (0.2-0.5): (1.6-1.8); The nano titanium dioxide is rutile titanium dioxide with a particle size of 200-300nm; The particle size of the nano barium sulfate is 40-50nm, and the specific surface area is 20-40m 2 / g.

2. The method for preparing highly weather-resistant titanium dioxide according to claim 1, characterized in that: In step S1, nano titanium dioxide is mixed with water to obtain a suspension having a material-water ratio of 1.2-2.0 g / L, a dispersant is added in an amount of 0.6-1.0 g / L, and the mixture is stirred and mixed uniformly at room temperature and 200-300 r / min to obtain a titanium dioxide dispersion.

3. The method for preparing highly weather-resistant titanium dioxide according to claim 1, characterized in that: In the step S2, tris(hydroxymethyl)aminomethane is dissolved in the titanium dioxide dispersion at an addition amount of 1.0-1.2 g / L, and a hydrochloric acid solution with a concentration of 2.5-3.65 g / L is slowly added and mixed until the pH of the titanium dioxide dispersion is adjusted to 8.5-9.

4. The method for preparing highly weather-resistant titanium dioxide according to claim 1, characterized in that: In step S3, tannic acid is added to the mixed titanium dioxide dispersion in step S2 in an amount of 2-3 g / L, and stirred at a speed of 500-800 r / min and a temperature of 25-30° C. to react for 12-24 hours.

5. The method for preparing highly weather-resistant titanium dioxide according to claim 1, characterized in that: In the step S4, tannic acid-titanium dioxide is added to an ethanol aqueous solution with a concentration of ≥95 v / v%, at which the material-liquid ratio is 1.0-1.5 g / L, and 3-glycidyloxypropyltriethoxysilane is added. The mixture is stirred for 30-60 min at room temperature and a speed of 200 r / min to dissolve evenly. The speed is increased to 500 r / min, the temperature is increased to 60-70°C, and nano-barium sulfate is slowly added while stirring. After the addition is completed, the speed is increased to 1000 r / min, and stirring is continued for 30-60 min.

6. The method for preparing highly weather-resistant titanium dioxide according to claim 1, characterized in that: In steps S3 and S4, the water used in the multiple washings is deionized water, and the solid slag A is washed until the conductivity of the aqueous solution is ≤100 μS / cm, and the solid slag B is washed until the conductivity of the aqueous solution is ≤50 μS / cm.

7. The method for preparing highly weather-resistant titanium dioxide according to claim 2, characterized in that: The dispersant is at least one of sodium hexametaphosphate, sodium dihydrogen phosphate, calcium silicate and sodium silicate.

8. A highly weather-resistant titanium dioxide, characterized in that: Prepared according to the method according to any one of claims 1 to 7.

9. Use of the highly weather-resistant titanium dioxide according to claim 8 in the preparation of coatings, paints and / or plastics with high weather resistance.

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