High-brightness and high-whiteness anatase titanium dioxide pigment and preparation method therefor

Abstract

The present application relates to the technical field of the preparation of titanium dioxide. Specifically disclosed are a high-brightness and high-whiteness anatase titanium dioxide pigment and a preparation method therefor. A high-brightness and high-whiteness anatase titanium dioxide pigment and a preparation method therefor. The preparation method comprises: adding titanyl sulfate to water at 60-65°C, heating the mixture to 95-97°C at a rate of 2.3-3.5°C / min for hydrolysis, adjusting the pH of the system to 2.2-2.4 during the hydrolysis process, then adding anatase seed crystals, and after the hydrolysis reaction is finished, filtering same to remove the filtrate, so as to obtain metatitanic acid; adding the metatitanic acid to water to undergo pulping dispersion, and adding a reducing agent during the pulping process; then performing acid pickling with sulfuric acid and drying to obtain a crude product; blending, grinding and screening the crude product and a modifier to obtain a modified crude product; and performing jet milling on the modified crude product and a metal salt to obtain the titanium dioxide pigment product. By means of the preparation method for a high-brightness and high-whiteness anatase titanium dioxide pigment of the present application, the product has higher whiteness, stability and tinting strength, and is more suitable for being used in a plastic system.

Description

High-brightness white anatase titanium dioxide pigment and its preparation method Technical Field

[0001] This application relates to the technical field of titanium dioxide preparation, and more specifically, to a high-brightness white anatase titanium dioxide pigment and its preparation method. Background Technology

[0002] Titanium dioxide is a high-performance white pigment and an important chemical raw material. Due to its excellent optical properties, stable chemical properties, high refractive index and good hiding power, it is widely used in coatings, plastics, papermaking, inks and other fields.

[0003] With the rapid development of the plastic resin and recycled plastics industries (recycled plastics are currently widely used in textiles, automobiles, packaging, and consumer electronics), if titanium dioxide exhibits poor performance in terms of hue, whiteness, system compatibility, and temperature resistance (such as yellowing), it will lead to yellowing of plastic products, increased dosage requirements, and increased production costs during the separation and reuse of recycled plastics. Titanium dioxide is mainly divided into two types: anatase and rutile. Rutile titanium dioxide has better weather resistance and is less prone to yellowing, while anatase titanium dioxide has higher whiteness and is more suitable for plastic products. Therefore, there is an increasing demand for high-purity, blue-hue, high-whiteness, and easily dispersible anatase titanium dioxide products.

[0004] In the current production process of anatase titanium dioxide, high-efficiency reducing agents are added to the water washing and crystallization processes, and the number of water washing layers is increased to reduce the total iron impurity content of the semi-finished product. However, this results in the product's whiteness stability and coloring power failing to meet the requirements. Summary of the Invention

[0005] To improve the whiteness stability and tinting strength of anatase titanium dioxide, this application provides a high-brightness white anatase titanium dioxide pigment and its preparation method.

[0006] In a first aspect, this application provides a method for preparing a high-brightness white anatase titanium dioxide pigment, which mainly includes the following steps:

[0007] S1. Add titanium oxysulfate to water at 60-65℃, and heat to 95-97℃ at a rate of 2.3-3.5℃ / min for hydrolysis. During the hydrolysis process, adjust the pH of the system to 2.2-2.4, and then add anatase seed crystals to make the mass concentration of the seed crystals in the system 0.55-0.65%. After the hydrolysis reaction is completed, filter to remove the filtrate to obtain meta-acid titanium.

[0008] S2. Add meta-acid titanium to water for pulping and dispersion. During the pulping process, add a reducing agent to make the mass concentration of the reducing agent in the pulp 0.18-0.20%. The reducing agent is one of aluminum powder, trivalent titanium, or organic reducing agent S-200.

[0009] After further washing with sulfuric acid and drying, the crude product is obtained;

[0010] S3. Mix the crude product and the modifier, grind and sieve to obtain the modified crude product;

[0011] S4. The modified crude product is mixed with a metal salt and then subjected to air jet milling to obtain the final product.

[0012] By adopting the above technical solutions: First, through research, experimentation, and improvement of the titanium liquid hydrolysis process and parameters affecting the characteristics of metatitanic acid particles, including hydrolysis temperature, heating rate, and seed crystals, the fundamental indicators of titanium dioxide's blue phase and bleaching power are considered. Second, through further optimization of the metatitanic acid washing and crystallization process, and optimization of the selection of reducing agents, the impurity content in metatitanic acid is reduced, purity is increased, and whiteness is improved, the Fe impurity content is reduced, and the purity of titanium dioxide is increased to 98.5-98.7%, resulting in a brightness of 98.85-98.91% for the titanium dioxide dry powder.

[0013] In summary, the anatase titanium dioxide products produced have higher brightness, whiteness stability, tinting strength, compatibility, dispersibility, and processing flow properties in resin systems compared to commercially available products.

[0014] Optionally, the titanium oxysulfate is titanium oxysulfate produced in the sulfuric acid process and after sedimentation separation and fine filtration, and its iron content is 40 ppm by mass of Fe2O3.

[0015] By adopting the above technical solution, this process can further and effectively reduce the high iron content in titanium oxysulfate, providing a better whiteness basis for subsequent hydrolysis.

[0016] Optionally, the heating rate is 3.5℃ / min and the hydrolysis temperature is 95℃.

[0017] By adopting the above technical solution, when the hydrolysis conditions are within the above range, the whiteness stability and coloring power of the product are better.

[0018] Optionally, the titanium metaacid has a TiO2 concentration of 41-43%.

[0019] By adopting the above technical solution, when subsequent steps are performed with acidic titanium with TiO2 concentration within the above range, the whiteness stability and coloring power of the product are better.

[0020] Optionally, the modifier is one of stearate, phosphate, polyol and amine salt.

[0021] By adopting the above technical solution: using the above substances to modify the surface of the crude product, the product dispersibility is improved, secondary particle agglomeration is prevented, and the compatibility, brightness, dispersibility and processing flow properties of this product in plastic systems are improved, ultimately obtaining anatase titanium dioxide products with high brightness and easy dispersibility that meet the requirements for application in plastic resins.

[0022] Optionally, the amount of the modifier added is 0.25-0.45% of the mass of TiO2 in the crude product.

[0023] By adopting the above technical solution, when the amount of modifier is within the above range, the product has the best compatibility, brightness, dispersibility and processing flow properties in the plastic system.

[0024] Optionally, the metal salt is one of zinc oxide, kaolin, silica powder, and barium sulfate.

[0025] By adopting the above technical solution, after metal salts and modified crude products are subjected to air jet milling, the brightness of the resulting products in plastic products is improved, while the vividness and hue of the coloring pigments are preserved. It can also improve the heat resistance, wear resistance, chemical resistance and water resistance of plastic products.

[0026] Optionally, the amount of metal salt added is 3.5-4.5% of the mass of TiO2 in the modified crude product.

[0027] By adopting the above technical solution, the product exhibits optimal performance when the amount of metal salt added is within the above range.

[0028] Secondly, this application provides an anatase titanium dioxide pigment, which is prepared by the above-described method for preparing high-brightness white anatase titanium dioxide pigment.

[0029] By adopting the above technical solution, the anatase titanium dioxide prepared by the above preparation method has a dry powder whiteness of over 98.48%, which is higher than that of commercially available products. Moreover, after being added to the plastic system, it exhibits less yellowing and can ensure that the whiteness of the plastic products is maintained at over 94.25%, which is much higher than the whiteness of 89.92% of plastic products containing commercially available products. This indicates that it is more suitable for plastic resin systems and has higher brightness, whiteness stability, tinting strength, compatibility, dispersibility, and processing flow properties in the resin system compared to commercially available products.

[0030] Optionally, its TiO2 content is 98.5-98.7wt%, the Fe impurity content is 13-20ppm, and the dry powder brightness is 98.85-98.91%.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. This application, by limiting the temperature, heating rate, and seed crystals in the hydrolysis process, takes into account both the blue phase and tinting strength that titanium dioxide should possess. By optimizing the acidic titanium washing and crystallization process and the reducing agent, the content of impurity iron is reduced and the purity is improved, so that titanium dioxide has higher whiteness stability and tinting strength than commercially available products, and can be better used in plastic products.

[0033] 2. In this application, the subsequent steps are performed using acidic titanium with TiO2 concentration within the above-mentioned range, resulting in products with better whiteness stability and coloring power.

[0034] 3. After obtaining the crude anatase titanium dioxide, this application involves grinding and surface modification with substances such as stearate, followed by performance enhancement with ultrafine precipitated barium sulfate, and further pulverization and particle size reduction in an air jet to improve product brightness and dispersibility, prevent secondary particle agglomeration, and enhance the compatibility, brightness, dispersibility, and processing flow properties of the product in plastic systems. As the product exhibits increased brightness in plastic products and retains the vividness and hue of coloring pigments, it also improves the heat resistance, wear resistance, corrosion resistance, and water resistance of plastic products. Detailed Implementation

[0035] The present application will be further described in detail below with reference to the embodiments.

[0036] Titanium oxysulfate: Titanium oxysulfate produced in the sulfuric acid process and after sedimentation separation and fine filtration. Performance parameters: total titanium concentration, calculated as TiO2, is 200 g / L; impurity Fe content (calculated as Fe2O3) is 40 ppm.

[0037] Anatase seed crystals: Add 95 kg of titanium oxysulfate to 75 kg of water at 65 °C, and heat to 95 °C at a heating rate of 3.5 °C / min for 3.5 h for hydrolysis. During the hydrolysis process, add 20 wt% ammonia water to adjust the pH of the system to 2.4, and then keep the reaction at this temperature for 5 min to obtain anatase seed crystals. Example 1

[0038] An anatase titanium dioxide is prepared by the following steps:

[0039] S1. Add 95 kg of titanium oxysulfate to 75 kg of water at 65 °C, and heat to 95 °C at a heating rate of 3.5 °C / min for 3.5 h for hydrolysis. Perform vacuum crystallization under a vacuum of 0.0098 MPa, and continue to add anatase seed crystals to make the mass concentration of seed crystals in the system 0.65%. After the hydrolysis reaction is completed, filter and remove the filtrate to obtain a meta-acid titanium with a TiO2 concentration of 42%.

[0040] S2. Add meta-acid titanium to 95 kg of water and perform three pulping and washing processes. During each pulping and washing process, control the pulp temperature at 35℃ and the washing time at 95 min. Add reducing agent Ti2(SO4)3 during the pulping and washing process to make the mass concentration of reducing agent in the pulp system 0.18%. Then, rinse into a sodium hydroxide aqueous solution with a concentration of 90 g / L. Maintain the temperature during neutralization at 25-45℃ and control the acidity coefficient at the endpoint to 0.45. Then, raise the temperature to 90℃ at a rate of 2℃ / min and stir.

[0041] After pulping, add sulfuric acid (concentration of 175 g / L) three times the volume of the pulp for acid leaching, filter to remove the filtrate, and dry at 120℃ for 1.5 h to obtain a crude product with TiO2 content of 98.6% and impurity iron content (calculated as Fe2O3) of 14 ppm.

[0042] S3. Add the crude product and 0.35% by mass of calcium stearate of TiO2 in the crude product to the Raymond mill, grind and sieve to obtain a modified crude product with a particle size range of 0.21-0.45μm;

[0043] S4. Add the modified crude product and 3.5% by mass of TiO2 in the modified crude product of ultrafine precipitated barium sulfate (particle size 6000 mesh) to the air jet mill, and perform air jet milling to produce anatase titanium dioxide with a particle size range of 0.15-0.35μm. Example 2

[0044] An anatase titanium dioxide is prepared by the following steps:

[0045] S1. Add 105 kg of titanium oxysulfate to 85 kg of water at 60 °C, and heat to 96 °C at a heating rate of 2.4 °C / min for 3.5 h for hydrolysis. During the hydrolysis process, adjust the pH of the system to 2.3 with 19 wt% ammonia water. Then add anatase seed crystals to make the mass concentration of the seed crystals in the system 0.55%. After the hydrolysis reaction is completed, filter and remove the filtrate to obtain a metaacid titanium with a TiO2 concentration of 43%.

[0046] S2. Add meta-acid titanium to 105 kg of water and perform three pulping and washing processes. During each pulping and washing process, control the pulp temperature at 36℃ and the washing time at 100 min. Add reducing agent alumina during the pulping and washing process to make the mass concentration of reducing agent in the pulp system 0.20%. Then, rinse into a sodium hydroxide aqueous solution with a concentration of 90 g / L. Maintain the temperature at 25-45℃ during neutralization and control the acidity coefficient at the endpoint to be 0.45. Then, raise the temperature to 90℃ at a rate of 2℃ / min and stir.

[0047] After pulping, add sulfuric acid (concentration of 175 g / L) three times the volume of pulp for acid leaching, filter to remove the filtrate, and dry at 120℃ for 1.5 h to obtain a crude product with TiO2 content of 98.5% and impurity iron content (calculated as Fe2O3) of 15 ppm.

[0048] S3. Add the crude product and 0.25% ammonium chloride (by mass of TiO2) to the Raymond mill, grind and sieve to obtain a modified crude product with a particle size range of 0.21-0.45 μm;

[0049] S4. Add the modified crude product and 4% by mass of zinc oxide (3000 mesh) of TiO2 in the modified crude product to the air jet mill, and perform air jet milling to produce anatase titanium dioxide with a particle size range of 0.15-0.35μm. Example 3

[0050] An anatase titanium dioxide is prepared by the following steps:

[0051] S1. Add 100 kg of titanium oxysulfate to 80 kg of water at 65 °C, and heat to 97 °C at a heating rate of 2.3 °C / min for 3.4 h for hydrolysis. During the hydrolysis process, adjust the pH of the system to 2.2 with 19 wt% ammonia water. Then add anatase seed crystals to make the mass concentration of the seed crystals in the system 0.60%. After the hydrolysis reaction is completed, filter and remove the filtrate to obtain a metaacid titanium with a TiO2 concentration of 43%.

[0052] S2. Add meta-acid titanium to 100kg of water and perform three pulping and washing processes. During each pulping and washing process, control the pulp temperature at 36℃ and the washing time at 100min. Add organic reducing agent S-200 during the pulping and washing process to make the mass concentration of the reducing agent in the pulp system 0.19%. Then, rinse into a sodium hydroxide aqueous solution with a concentration of 90g / L. Maintain the temperature at 25-45℃ during the neutralization process and control the acidity coefficient at the endpoint to be 0.45. Then, raise the temperature to 90℃ at a rate of 2℃ / min and stir.

[0053] After pulping, add sulfuric acid (concentration of 175 g / L) three times the volume of the pulp for acid leaching, filter to remove the filtrate, and dry at 120℃ for 1.5 h to obtain a crude product with TiO2 content of 98.7% and impurity iron content (calculated as Fe2O3) of 20 ppm.

[0054] S3. Add the crude product and 0.45% (by mass) of calcium stearate (TiO2) to the Raymond mill. After grinding, modification, and sieving, a modified crude product with a particle size range of 0.21-0.40 μm is obtained.

[0055] S4. Add the modified crude product and 4.5% by mass of TiO2 in the modified crude product, ultrafine precipitated barium sulfate (particle size 6000 mesh), to the air jet mill, and perform air jet milling to obtain anatase titanium dioxide with a particle size range of 0.15-0.35μm.

[0056] Comparative Example 1: An anatase titanium dioxide, model number JMA110, manufactured by Guangxi Jinmao Titanium Industry Co., Ltd.

[0057] Comparative Example 2: An anatase titanium dioxide, model SFA101, manufactured by Guangxi Shunfeng Titanium Industry Co., Ltd.

[0058] Comparative Example 3: An anatase titanium dioxide, differing from Example 1 in that steps S1 and S2 are different, as detailed below:

[0059] S1. Add 95 kg of titanium oxysulfate to 75 kg of water at 65 °C, and heat to 110 °C at a heating rate of 10 °C / min for 3.5 h for hydrolysis. During the hydrolysis process, adjust the pH of the system to 2.4 with 20 wt% ammonia water. Then add anatase seed crystals to make the mass concentration of the seed crystals in the system 0.5%. After the hydrolysis reaction is completed, filter and remove the filtrate to obtain meta-acid titanium.

[0060] S2. Add meta-acid titanium to 95 kg of water and perform three pulping and washing processes. During each pulping and washing process, control the pulp temperature at 35℃ and the washing time at 95 min. Add trivalent titanium as a reducing agent during the pulping and washing process to make the mass concentration of the reducing agent in the pulp system 0.18%. Then, rinse into a sodium hydroxide aqueous solution with a concentration of 90 g / L. Maintain the temperature at 25-45℃ during the neutralization period and control the acidity coefficient at the endpoint to be 0.45. Then, raise the temperature to 90℃ at a rate of 2℃ / min and stir.

[0061] After pulping, the filtrate is removed by filtration, and the product is dried at 120℃ for 1.5 hours to obtain the crude product.

[0062] Comparative Example 4: An anatase titanium dioxide pigment, which differs from Example 1 in that steps S3 and S4 are not performed.

[0063] The titanium dioxide pigments prepared in the examples and comparative examples were subjected to the following performance tests, and the test results are recorded in Table 1.

[0064] 1. After pressing the titanium dioxide powder into cakes using a manual cake press, the L value, b value, and whiteness were obtained by testing with a CM-23d spectrophotometer.

[0065] 2. Add the mixture obtained by blending 4g of titanium dioxide and 196g of PP to an HTW-500x2 horizontal injection molding machine to make a sample with a thickness of 2mm. The sample is tested using a CM-23d spectrophotometer to obtain the L value, b value and whiteness.

[0066] 3. Filtration pressure value (FPV): The filtration pressure value (FPV) is measured by using a twin-screw extruder to mix the sample with linear low-density polyethylene (LLDPE) to form a 70% concentration masterbatch, adding the original color resin to dilute it into a carrier mixture containing 14% titanium dioxide, and then using a single-screw extruder. The FPV is used to characterize the dispersibility of titanium dioxide. A smaller value indicates better dispersibility in the system.

[0067] 4. Melt Flow Rate (MFR) is determined by mixing titanium dioxide with linear low-density polyethylene (LLDPE) with an MFR of 25 g / 10 min using a twin-screw extruder to produce a 60% concentration masterbatch. The melt flow rate (MFR) is then tested according to ISO 1133-1:2011 standard, with test parameters set at 190℃ and a load of 2.16 kg. This test is used to characterize the compatibility and flow properties of titanium dioxide in the resin system. A higher value indicates better compatibility and flow properties in the system.

[0068] Table 1 Performance Test Results

[0069]

[0070] Referring to Table 1, the whiteness of the titanium dioxide dry powder prepared in Examples 1-3 is above 98.48%, and the whiteness after blending with PP resin and testing remains above 94.41%. In contrast, the whiteness of commercially available dry powder is significantly lower than that of the product in this application, especially after being added to the resin system, where the whiteness is even lower, around 90%, indicating greater yellowing. This demonstrates that the titanium dioxide prepared in this application has higher whiteness, less yellowing, better stability, and better coloring power in the resin system. At the same time, comparative testing shows a lower filtration pressure value and a higher melt flow index, indicating that the patented product has better dispersibility and compatibility in the plastic system, better meeting the characteristic requirements of plastic resins for anatase titanium dioxide pigments.

[0071] The difference between Comparative Example 3 and Example 1 is that the processing parameters in steps S1 and S2 are different, resulting in a decrease in the whiteness of titanium dioxide.

[0072] The difference between Comparative Example 4 and Example 1 is that without steps S3 and S4, the performance indicators of titanium dioxide decrease.

[0073] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-brightness white anatase titanium dioxide pigment and its preparation method, characterized in that, Includes the following steps: S1. Add titanium oxysulfate to water at 60-65℃, and heat to 95-97℃ at a rate of 2.3-3.5℃ / min for hydrolysis. During the hydrolysis process, adjust the pH of the system to 2.2-2.4, and then add anatase seed crystals to make the mass concentration of the seed crystals in the system 0.55-0.65%. After the hydrolysis reaction is completed, filter to remove the filtrate to obtain meta-acid titanium. S2. Add meta-acid titanium to water for pulping and dispersion. During the pulping process, add a reducing agent to make the mass concentration of the reducing agent in the pulp 0.18-0.20%. The reducing agent is one of aluminum powder, trivalent titanium, or organic reducing agent S-200. After further washing with sulfuric acid and drying, the crude product is obtained; S3. Mix the crude product and the modifier, grind and sieve to obtain the modified crude product; S4. The modified crude product and the metal salt are subjected to air jet milling to obtain the final product.

2. The method for preparing high-brightness white anatase titanium dioxide according to claim 1, characterized in that: The heating rate is 3.5℃ / min, and the hydrolysis temperature is 95℃.

3. The method for preparing a high-brightness white anatase titanium dioxide pigment according to claim 1, characterized in that: The meta-acid titanium has a TiO2 concentration of 41-43%.

4. The method for preparing a high-brightness white anatase titanium dioxide pigment according to claim 1, characterized in that: The titanium oxysulfate mentioned is titanium oxysulfate produced by the sulfuric acid process and after sedimentation separation and fine filtration. Its iron impurity content is 40 ppm based on Fe2O3 mass.

5. The method for preparing high-brightness white anatase titanium dioxide according to claim 1, characterized in that: The modifier is one of stearate, phosphate, polyol and amine salt.

6. The method for preparing high-brightness white anatase titanium dioxide according to claim 5, characterized in that: The amount of the modifier added is 0.25-0.45% of the mass of TiO2 in the crude product.

7. The method for preparing a high-brightness white anatase titanium dioxide pigment according to claim 1, characterized in that: The metal salt is one of zinc oxide, kaolin, silica powder, and barium sulfate.

8. The method for preparing a high-brightness white anatase titanium dioxide pigment according to claim 7, characterized in that: The amount of metal salt added is 3.5-4.5% of the mass of TiO2 in the modified crude product.

9. An anatase titanium dioxide, characterized in that: It is prepared by the method for preparing high-brightness white anatase titanium dioxide pigment according to any one of claims 1-8.

10. The anatase titanium dioxide according to claim 9, characterized in that: Its TiO2 content is 98.5-98.7wt%, the Fe impurity content is 13-20ppm based on Fe2O3 mass, and the dry powder brightness is 98.85-98.91%.

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