A continuous flow general coating method and device for titanium dioxide

Abstract

The present application relates to titanium dioxide coating technical field, especially to a kind of titanium dioxide continuous flow general coating method and device, four reaction units are installed and connected from left to right in series, and the control of the installation and connection position of first metering pump, second metering pump, third metering pump, fourth metering pump, fifth metering pump, sixth metering pump is combined, so that the accurate control of material feeding position and feeding amount, in turn, titanium dioxide silicon film layer and aluminum film layer process are effectively controlled, and the control of the quality of silicon film layer, aluminum film layer coating in continuous flow process can be realized, the control of temperature and other process parameters in continuous flow reaction system is combined, silicon coating rate is promoted to reach 94% or more under 90-95 ℃, compared with gap method silicon coating rate 80.37%, about 14 percentage points are improved;Aluminum coating rate reaches 97% or more, compared with gap method aluminum coating rate 91.26%, about 6 percentage points are improved, improve titanium dioxide coating effect.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide coating technology, and in particular to a general coating method and apparatus for continuous flow of titanium dioxide. Background Technology

[0002] Titanium dioxide, as a white pigment, is widely used in coatings, plastics, inks, and other fields. Currently, most titanium dioxide products require inorganic surface treatment before further utilization. This is because untreated titanium dioxide has many hydroxyl groups on its surface, resulting in high polarity and a tendency to agglomerate and settle in organic media, leading to poor dispersibility and post-dispersion stability. Furthermore, untreated titanium dioxide exhibits poor weather resistance and chemical stability. Therefore, coating titanium dioxide to achieve surface treatment has become a key technical means to improve its weather resistance and other application properties. The effectiveness of the surface coating directly affects the final application performance of the titanium dioxide product.

[0003] Currently, the surface coating treatment of titanium dioxide in China all adopts an intermittent coating process. This process has several drawbacks: First, it cannot guarantee the uniform mixing of the coating material and the titanium dioxide slurry, thus failing to ensure that the resulting coating layer has continuity, uniform thickness, regular shape, and good uniformity. Second, the intermittent coating process has a long cycle time, typically requiring 10-12 hours, which seriously affects equipment operating efficiency, resulting in low equipment capacity, high costs, and high energy consumption.

[0004] Based on this, existing technologies have developed continuous processing techniques for inorganic coating of titanium dioxide. For example, patent number 201110364773.4 discloses mixing titanium dioxide slurry with a first coating material and a first neutralizing material in a first mixing device, then ultrasonically dispersing it in a first ultrasonic device, followed by curing in a first curing device. After curing, the mixture is then mixed with a second coating material and a second neutralizing material in a second mixing device, ultrasonically dispersed in a second ultrasonic device, and then cured in a second curing device. Specifically, the patent discloses diluting the titanium dioxide coating slurry to 300 g / L, preheating the titanium dioxide coating slurry to 80°C, and adding the coating slurry, sodium silicate, and 20% sulfuric acid to the mixing device. The flow rate of the coating slurry is 50 mL / min. Sodium flow rate is 0.2 mL / min. The material then enters a pH monitoring system to control the flow rate of the neutralizing agent, maintaining the pH of the coating system at 9.0. Next, the material enters an ultrasonic device for ultrasonic dispersion, then enters a curing device, where it remains for 60 minutes at 80°C. Sodium aluminate and the neutralizing agent then enter a mixing device to mix with the above material at a flow rate of 4.3 mL / min. The material then enters a pH monitoring system to control the flow rate of the neutralizing agent, maintaining the pH of the coating system at 8.5. The material then enters an ultrasonic device for ultrasonic dispersion, then enters a curing device, where it remains for 60 minutes at 60°C. After coating, the material enters a coating curing storage tank, where it is washed, dried, and subjected to air jet milling to obtain the titanium dioxide product.

[0005] It is evident that existing continuous coating processes still suffer from several drawbacks: the coating cycle is relatively long, at least 2 hours, and the coating equipment is expensive and energy-intensive.

[0006] In view of this, in order to better reduce the cost and energy consumption of the continuous coating process of titanium dioxide, shorten the coating process cycle, and improve the coating rate of titanium dioxide for silicon and aluminum, our research team has made compatibility improvements to the continuous coating process of titanium dioxide and its process parameters, providing a new process for inorganic coating of titanium dioxide. Summary of the Invention

[0007] Based on the above-mentioned technical problems, the present invention provides a method and apparatus for continuous flow coating of titanium dioxide.

[0008] The specific technical solution is as follows: One objective of this invention is to provide a continuous flow coating device for titanium dioxide, comprising four reaction units connected in series from left to right. Each reaction unit is provided with a first inlet, a second inlet, and an outlet. The previous reaction unit is connected to the next reaction unit via the outlet and the first inlet. The outlet of the rightmost reaction unit is connected to a collection tank. From left to right, each reaction unit has a second metering pump for pumping sodium silicate, a third metering pump for pumping sulfuric acid, a fourth metering pump for pumping sodium aluminate, and a sixth metering pump for pumping sulfuric acid connected to its second inlet. The bottom of the third reaction unit has an inlet connected to a fifth metering pump for pumping sulfuric acid. Each reaction unit contains a stirrer, the top of which extends from the top of the reaction unit and is connected to a motor. The first inlet of the leftmost reaction unit is connected to a first metering pump for pumping titanium dioxide slurry.

[0009] This invention employs four reaction units connected in series from left to right, and combines this with the control of the installation and connection positions of the first, second, third, fourth, fifth, and sixth metering pumps. This allows for accurate control of the material feeding position and quantity, thereby effectively controlling the processes of coating silicon and aluminum layers onto titanium dioxide. Furthermore, it enables control over the coating quality of silicon and aluminum layers during continuous flow, helping to improve the coating rate and resulting in continuous, uniform, regular, and highly consistent films. The device is also simple in structure, requires no ultrasonic devices, and is low in cost and energy consumption.

[0010] Preferably, the first metering pump is connected to a mixing tank, which is connected to a titanium dioxide tank; the second metering pump is connected to a sodium silicate tank; the third, fifth, and sixth metering pumps are all connected to a sulfuric acid tank; and the fourth metering pump is connected to a sodium aluminate tank.

[0011] To ensure the operability of the titanium dioxide silicon coating and aluminum coating processes and to guarantee accurate control of process parameters when the silicon and aluminum coating rates of the titanium dioxide reach optimal levels, preferably, the first metering pump is equipped with a controller capable of controlling its pumping rate to be 238.5-262.75 mL / min; the second metering pump is equipped with a controller capable of controlling its pumping rate to be 27-35 mL / min; the third metering pump is equipped with a controller capable of controlling its pumping rate to be 5.5-7.1 mL / min; the fourth metering pump is equipped with a controller capable of controlling its pumping rate to be 10-15 mL / min; the fifth metering pump is equipped with a controller capable of controlling its pumping rate to be 18.9-28.5 mL / min; and the sixth metering pump is equipped with a controller capable of controlling its pumping rate to be 12.32 mL / min. More preferably, a frequency converter is installed on the motor, and the frequency converter is equipped with a controller capable of controlling the motor frequency to 50Hz. More preferably, a heat exchanger is installed on the reaction unit, and a temperature sensor is installed inside the reaction unit. The heat exchanger and the temperature sensor are respectively connected to a controller capable of controlling the temperature inside the reaction unit to 90-95℃. In practical use, the controller of this invention is selected from PLC controllers; in addition, other controllers capable of achieving the above functions and objectives can also be selected.

[0012] To ensure the coating effect, preferably, the reaction unit allows the residence time of the titanium dioxide slurry from entering the leftmost reaction unit to exiting from the outlet of the rightmost reaction unit to be 59-60 minutes.

[0013] The second objective of this invention is to provide a general method for continuous flow coating of titanium dioxide, which utilizes the aforementioned apparatus to coat titanium dioxide with silicon and aluminum, specifically: A. Prepare a titanium dioxide slurry with a content of 300g / L; take sodium silicate with a content of 100g / L, sulfuric acid with a mass percentage of 15%, sodium aluminate with a content of 160g / L, and aluminum sulfate with a content of 100g / L for later use. B. Turn on the motor and control the temperature inside the reaction unit to 90-95℃. Simultaneously pump the titanium dioxide slurry and sodium silicate into the leftmost reaction unit. When the discharge port of the leftmost reaction unit begins to discharge, pump sulfuric acid into the second reaction unit. When the discharge port of the second reaction unit begins to discharge, pump sodium aluminate into the third reaction unit and pump sulfuric acid into the third reaction unit. When the discharge port of the third reaction unit begins to discharge, pump sulfuric acid into the fourth reaction unit. The residence time of the titanium dioxide slurry from entering the leftmost reaction unit to exiting the rightmost reaction unit should be 59-60 minutes.

[0014] This invention creates a process that enables continuous titanium dioxide coating with silicon and aluminum, requiring only about 60 minutes from feeding to product output. This is a significant reduction compared to the traditional intermittent method which takes 6-12 hours. Moreover, compared to the existing continuous titanium dioxide coating with silicon and aluminum process which requires at least 2 hours, this process saves at least 50% of the time, helping to accelerate equipment output, increase production capacity, and reduce costs.

[0015] To improve the coating rate of silicon-coated aluminum, the motor preferably has a frequency of 50Hz. More preferably, the pumping rate of the titanium dioxide slurry is 238.5-262.75 mL / min; the pumping rate of the sodium silicate is 27-35 mL / min; the pumping rate of the third metering pump for sulfuric acid is 5.5-7.1 mL / min; the pumping rate of the sodium aluminate is 10-15 mL / min; the pumping rate of the fifth metering pump for sulfuric acid is 18.9-28.5 mL / min; and the pumping rate of the sixth metering pump for sulfuric acid is 12.32 mL / min.

[0016] This invention creates a continuous flow reaction system that integrates four reaction units to achieve precise phased control of the pH value within the reaction system, thereby achieving the goal of layering silica and alumina layers within a single reaction system.

[0017] The device created by this invention has a simple structure, low cost, and is easy to industrialize and promote.

[0018] This invention, particularly the integration of a continuous flow reaction system with the control of process parameters such as temperature within the system, achieves a silicon coating rate of over 94% at 90-95℃, an increase of approximately 14 percentage points compared to the 80.37% silicon coating rate of the interstitial method; and an aluminum coating rate of over 97%, an increase of approximately 6 percentage points compared to the 91.26% aluminum coating rate of the interstitial method, thus improving the coating effect of titanium dioxide. Attached Figure Description

[0019] To facilitate a thorough understanding of the technical solution of this invention by those skilled in the art, the following description is provided in conjunction with the technical solution and the accompanying drawings. The directional terms used in this invention, such as "up," "down," "front," "back," "left," and "right," are merely illustrative descriptions in conjunction with the accompanying drawings and are not intended to limit the technical solution of this invention.

[0020] Figure 1 This is a schematic diagram of the device structure for this invention.

[0021] Figure 2 A schematic diagram of the device structure for another embodiment of the present invention.

[0022] 1-First feed inlet 2-Second feed inlet 3-Motor 4-Reaction unit 5-Discharge outlet 6-First metering pump 7-Second metering pump 8-Mixing tank 9-Sodium silicate tank 10-Titanium dioxide tank 11-Third metering pump 12-Fourth metering pump 13-Fifth metering pump 14-Sixth metering pump 15-Collection tank 16-Aluminum sulfate tank 17-Sodium aluminate tank 18-Sulfuric acid tank 19-Inlet.

[0023] Figure 3 This is a 200nm electron microscope image of a titanium dioxide product coated with silicon and aluminum using the interstitial method.

[0024] Figure 4 This is a 100nm electron microscope image of a titanium dioxide product coated with silicon and aluminum using the interstitial method.

[0025] Figure 5 This is a 1μm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 12.

[0026] Figure 6 This is a 100nm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 12.

[0027] Figure 7 The image shown is a 50nm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 12.

[0028] Figure 8 This is a 1μm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 28.

[0029] Figure 9 This is a 100nm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 28.

[0030] Figure 10 The image shown is a 50nm electron microscope image of the titanium dioxide product coated with silicon and aluminum obtained in Example 28. Detailed Implementation

[0031] To facilitate a correct understanding of the present invention by those skilled in the art, and to enable them to fully understand the technical content of the present invention, the technical solution of the present invention will be further described below in conjunction with specific embodiments. However, this description does not limit the scope of protection claimed by the present invention. Those skilled in the art should not limit the scope of protection of the present invention to the following description. Any equivalent substitutions or changes made by those skilled in the art or those familiar with the art based on the present invention, and based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0032] like Figure 1 As shown, in some embodiments, the titanium dioxide continuous flow recoating device includes four reaction units 4 connected in series from left to right. Each reaction unit 4 has a first inlet 1, a second inlet 2, and an outlet 5. The reaction units 4, the first inlet 1, the second inlet 2, and the outlet 5 form an integrated reactor. This reactor can refer to commercially available vertical hydrothermal synthesis reactors, for example, with dimensions of 780mm × 1100mm × 1700mm. By selecting four such reaction units 4, connecting the previous reaction unit 4 to the next through the outlet 5 and the first inlet 1, and connecting the outlet 5 of the rightmost reaction unit 4 to a collection tank 15, a complete continuous flow reaction system is constructed and integrated. This structure achieves continuous flow and contact reaction of materials from left to right. Furthermore, from left to right, the second inlet 2 of each reaction unit 4 is sequentially connected to a collection tank 15. A second metering pump 7 (e.g., a metering pump with a range of 0-200 mL / min) is used for pumping sodium silicate; a third metering pump 11 (e.g., a metering pump with a range of 0-100 L / min) is used for pumping sulfuric acid; a fourth metering pump 12 (e.g., a metering pump with a range of 0-100 L / min) is used for pumping sodium aluminate; and a sixth metering pump 14 (e.g., a metering pump with a range of 0-100 L / min) is used for pumping aluminum sulfate. An inlet 19 is provided at the bottom of the third reaction unit 4, and a fifth metering pump 13 (e.g., a metering pump with a range of 0-100 L / min) is connected to the inlet 19. A stirrer is provided inside the reaction unit 4, and a motor 3 is connected to the top of the stirrer extending from the top of the reaction unit 4. A first metering pump 6 (e.g., a metering pump with a range of 0-50 L / h) is connected to the first feed inlet 1 of the leftmost reaction unit 4.

[0033] During installation, install as follows Figure 1The connections and installation can be completed as shown and described above. When using, prepare the titanium dioxide into a slurry, and then store sodium silicate, sulfuric acid, sodium aluminate, and aluminum sulfate separately in their respective containers. Turn on motor 3 and control the temperature inside reaction unit 4 to 60-65℃. Simultaneously pump titanium dioxide slurry and sodium silicate into the leftmost reaction unit 4. When the discharge port 5 of the leftmost reaction unit 4 begins to discharge, pump sulfuric acid into the second reaction unit 4. When the discharge port 5 of the second reaction unit 4 begins to discharge, pump sodium aluminate into the third reaction unit 4 and aluminum sulfate into the third reaction unit 4. When the discharge port 5 of the third reaction unit 4 begins to discharge, pump aluminum sulfate into the fourth reaction unit 4, ensuring that the pH at the discharge port 5 of the fourth reaction unit 4 is 7. The residence time of the titanium dioxide slurry from entering the leftmost reaction unit 4 and exiting from the discharge port 5 of the rightmost reaction unit 4 is 62 minutes, thus completing the titanium dioxide coating with silica and aluminum.

[0034] The device has a simple structure and is easy to operate. It does not require ultrasonic treatment, resulting in lower costs and energy consumption. Furthermore, the short residence time from feed to discharge (approximately 62 minutes) leads to a shorter cycle time, higher equipment capacity, and reduced costs. The resulting titanium dioxide exhibits superior silicon and aluminum coating rates, with ideal coating quality.

[0035] like Figure 1 As shown, in some embodiments, the first metering pump 6 is connected to a mixing tank 8, which is connected to a titanium dioxide tank 10; the second metering pump 7 is connected to a sodium silicate tank 9; the third metering pump 11 is connected to a sulfuric acid tank 18; the fourth metering pump 12 is connected to a sodium aluminate tank 17; and the fifth metering pump 13 and the sixth metering pump 14 are both connected to aluminum sulfate tanks 16. This allows the corresponding materials to be prepared and loaded into the corresponding equipment of the device, facilitating the continuous processing of titanium dioxide coating with silicon and aluminum. Simultaneously, it allows for the connection of corresponding storage equipment according to the corresponding location, enabling the pumping of the appropriate materials at the correct process location, achieving precise phased control of the pH value within the reaction system, thereby achieving layer-by-layer coating of silicon dioxide and aluminum oxide within a single reaction system.

[0036] In some embodiments, the first metering pump 6 is equipped with a controller capable of controlling the pumping rate of the first metering pump 6 to be 173-175 mL / min; the second metering pump 7 is equipped with a controller capable of controlling the pumping rate of the second metering pump 7 to be 61-63 mL / min; the third metering pump 11 is equipped with a controller capable of controlling the pumping rate of the third metering pump 11 to be 9 mL / min; the fourth metering pump 12 is equipped with a controller capable of controlling the pumping rate of the fourth metering pump 12 to be 35.3 mL / min; the fifth metering pump 13 is equipped with a controller capable of controlling the pumping rate of the fifth metering pump 12 to be 35.8 mL / min; and the sixth metering pump 14 is equipped with a controller capable of controlling the rate at which the sixth metering pump 14 pumps aluminum sulfate so that the pH of the slurry discharged from the outlet of the rightmost reaction unit is 7. In this embodiment, the installation can also be a connection. Specifically, those skilled in the art can install the controller in the entire device according to common knowledge known to them to achieve the above functions. This can help to accurately control the technical parameters during the process of coating silicon and aluminum with titanium dioxide, improve the coating rate, and enhance the coating quality.

[0037] In some embodiments, the motor 3 is equipped with a frequency converter, and the frequency converter is equipped with a controller capable of controlling the frequency of the motor 3 to 50Hz. In this embodiment, the installation can also be a connection; specifically, those skilled in the art can install the controller within the entire device based on common knowledge known to them to achieve the above functions. This helps to accurately control the technical parameters during the titanium dioxide coating process (silicon and aluminum coating), improve the coating rate, and enhance the coating quality.

[0038] In some embodiments, a heat exchanger is installed on the reaction unit 4, and a temperature sensor is installed inside the reaction unit 4. The heat exchanger and the temperature sensor are respectively connected to a controller capable of controlling the temperature inside the reaction unit 4 to 60-65°C. In this embodiment, the installation can also be a connection; specifically, those skilled in the art can install the controller in the entire device according to common knowledge known to them to achieve the above functions. This helps to accurately control the technical parameters during the titanium dioxide coating process (silicon and aluminum coating), improve the coating rate, and enhance the coating quality.

[0039] In the above embodiments of this invention, the controller selected is a PLC controller. However, those skilled in the art can choose other controllers as long as they can achieve the above functions and objectives. The use of a PLC controller in this invention facilitates autonomous programming, thereby enabling autonomous control and adjustment of process parameters during the titanium dioxide coating process (silicon and aluminum coating), achieving a compatible continuous flow device and continuous flow reaction parameters.

[0040] In some embodiments, the reaction unit 4 allows the residence time of the titanium dioxide slurry from entering the leftmost reaction unit 4 to exiting from the outlet 5 of the rightmost reaction unit 4 to be 62 minutes. By accurately defining the process parameters and controlling the residence time, the size and specifications of the reaction unit 4 can be effectively defined. Therefore, in this invention, using a reactor with specific dimensions, such as 780mm × 1100mm × 1700mm and a liquid holding capacity of 20L (total for 4 reaction units), the production time of the titanium dioxide coated with silicon and aluminum can be effectively shortened, the overall capacity of the device can be increased, energy consumption can be reduced, and the silicon and aluminum coating rates of the obtained products can be ensured to be superior.

[0041] In order to better verify the technical effects that the present invention can bring, the present invention utilizes the above-mentioned device and conducts a study on the compatibility of process parameters during the application of the device, and then conducts the following implementation study, and obtains a low-temperature continuous flow coating method for titanium dioxide.

[0042] I. Study on the matching process parameters of the continuous flow recoating device for titanium dioxide (I) Raw Material Information

[0043] (II) Test Apparatus The reaction unit 4, first metering pump 6, second metering pump 7, mixing tank 8, sodium silicate tank 9, titanium dioxide tank 10, third metering pump 11, fourth metering pump 12, fifth metering pump 13, sixth metering pump 14, collection tank 15, aluminum sulfate tank 16, sodium aluminate tank 17, and sulfuric acid tank 18 are arranged as follows: Figure 1 The schematic diagram of the device structure shown illustrates the installation and integration of a continuous flow reaction device system.

[0044] The above-mentioned integrated continuous flow reaction device system was used to carry out the silicon-coating and aluminum-coating test of titanium dioxide to verify the effect of silicon-coating and aluminum-coating rate under low temperature (60-65℃) conditions.

[0045] (III) Continuous Flow Recoating Method for Titanium Dioxide

[0046] like Figure 1Turn on motor 3 and control the temperature inside reaction unit 4 to 60-65℃. Simultaneously pump titanium dioxide slurry and sodium silicate into the leftmost reaction unit 4. When the discharge port 5 of the leftmost reaction unit 4 starts to discharge, pump sulfuric acid into the second reaction unit 4. When the discharge port 5 of the second reaction unit 4 starts to discharge, pump sodium aluminate into the third reaction unit 4 and aluminum sulfate into the third reaction unit 4. When the discharge port 5 of the third reaction unit 4 starts to discharge, pump aluminum sulfate into the fourth reaction unit 4, ensuring that the pH at the discharge port 5 of the fourth reaction unit 4 is 7. The residence time of the titanium dioxide slurry from entering the leftmost reaction unit 4 and exiting from the discharge port 5 of the rightmost reaction unit 4 is 62 minutes. When stopping the machine, when no material flows out of the discharge port 5, simultaneously stop pumping sulfuric acid, sodium aluminate, aluminum sulfate, etc., and then stop motor 3.

[0047] (iv) Experiment on process parameters

[0048] The above-mentioned apparatus and titanium dioxide coating process were used to conduct experimental research on the process parameters for continuous flow recoating of titanium dioxide, as detailed below: The method for calculating the silicon coating rate is as follows: After washing the obtained product with water, the amount of silicon dioxide is measured using XRF to obtain the actual amount of silicon dioxide. Then, based on: Silicon coating rate = (actual amount of silicon dioxide ÷ theoretical amount of silicon dioxide) × 100%.

[0049] The method for calculating the coating rate is as follows: After washing the obtained product with water, the amount of aluminum oxide is measured using XRF to obtain the actual amount of aluminum oxide. Then, based on: Aluminum coating rate = (actual aluminum oxide amount ÷ theoretical aluminum oxide amount) × 100%.

[0050] Experiment 1: Study on the Influence of Motor Frequency on Silicon and Aluminum Coating Ratio

[0051] The initial experimental process control reaction parameters are shown in Table 1 below: Table 1

[0052] The products obtained from the titanium dioxide coating with silicon and aluminum processes in Examples 1 to 4 were tested for silicon coating rate and aluminum coating rate. The results are shown in Table 2 below: Table 2

[0053] As shown in Tables 1 and 2, under the same process conditions, the rotation frequency of the motor driving the stirrer in the reaction unit affects the silicon and aluminum coating rates on the titanium dioxide surface. With increasing motor frequency, both silicon and aluminum coating rates improve. This phenomenon is likely due to the tendency of titanium dioxide particles in the titanium dioxide to settle, resulting in solid-liquid stratification, which affects mass transfer during the reaction process and leads to poor coating. However, considering energy consumption caused by motor frequency, under the same process parameters, the aluminum coating rate reaches over 90% at a motor frequency of 50Hz. Therefore, a motor frequency of 50Hz was chosen for subsequent experimental research.

[0054] Experiment 2: Study on the effect of reaction temperature on silicon and aluminum coating rate

[0055] Based on Experiment 1, after considering the overall energy consumption of the motor frequency and the effect of aluminum coating rate, the temperature of the titanium dioxide coating process with silicon and aluminum was investigated under the condition of 50Hz. The specific process parameter changes are shown in Table 3 below: Based on Experiment 1, after considering the overall energy consumption of the motor frequency and the effect of aluminum coating rate, the temperature of the titanium dioxide coating process with silicon and aluminum was investigated under the condition of 50Hz. The specific process parameter changes are shown in Table 3 below: Table 3

[0056] The products obtained from the titanium dioxide coating with silicon and aluminum processes in Examples 4 to 7 were tested for silicon coating rate and aluminum coating rate. The results are shown in Table 4 below: Table 4

[0057] As shown in Tables 3 and 4, temperature has a significant impact on the coating rate of titanium dioxide during the silicon and aluminum coating processes. Both silicon and aluminum coating rates increase with increasing temperature; however, this increase is accompanied by increased energy consumption. Furthermore, the rate of increase in both silicon and aluminum coating rates gradually decreases with increasing temperature. Therefore, considering both energy consumption and the improvement in silicon and aluminum coating rates, it is advisable to control the temperature of subsequent experiments at 60-65℃.

[0058] Experiment 3: Study on the effect of sulfuric acid pumping rate on silicon and aluminum coating rate Based on Experiments 1 and 2, and considering the combined energy consumption of motor frequency, reaction temperature, and coating efficiency, the temperature of the titanium dioxide coating process (coating with silicon and aluminum) was investigated under the conditions of 50Hz and 60-65℃. The specific process parameter variations are shown in Table 5 below. Table 5

[0059] The products obtained from the titanium dioxide coating with silicon and aluminum processes in Examples 6 and 8 to 10 were tested for silicon coating rate and aluminum coating rate. Simultaneously, the pH values ​​of the materials entering and exiting the third reaction unit were measured, and the residence time was recorded. The results are shown in Table 6 below. Table 6

[0060] As shown in Tables 5 and 6, changes in the sulfuric acid pumping rate will affect the residence time in the entire reaction system to a certain extent, and will also significantly affect the pH physicochemical factors in the entire process of silicon-coating and aluminum-coating, thereby affecting the silicon coating rate and aluminum coating rate. In other words, pH is a crucial technical parameter in the silicon-coating and aluminum-coating process of titanium dioxide, directly determining the hydrolysis path and product morphology of the silicon and aluminum sources, and further affecting the deposition mode of the film on the titanium dioxide surface, ultimately affecting the film quality and product performance. The study on the effect of pH on the silicon and aluminum coating stages revealed that: in the silicon coating stage, a pH value that is too low will result in small silica particles with poor dispersibility, making it difficult to form a continuous film structure. Impurities may also be introduced due to the dissolution of titanium ions, thus affecting the quality and resulting in a low silicon coating rate. Conversely, if the pH value is too high, the silica particles generated by sodium silicate under strongly alkaline conditions will have a negative surface charge, weakening the repulsive force between particles and making them prone to agglomeration into large particles. This leads to a rough coating, uneven thickness, localized excessive thickness, or clumping, which damages the uniformity of the film and results in a low silicon coating rate. During the aluminum coating stage, if the pH is too low, the high concentration of H⁺ will inhibit the hydrolysis of Al³⁺ (shifting the equilibrium to the left), resulting in insufficient aluminum hydroxide production. This prevents the deposition of the aluminum hydroxide film, leading to inadequate coating of the titanium dioxide surface and exposed areas, resulting in a low aluminum coating rate. Conversely, if the pH is too high, aluminum hydroxide will further react to form soluble aluminates (such as AlO⁻), preventing the aluminum source from depositing on the titanium dioxide surface or causing it to dissolve after deposition, further reducing the aluminum coating rate. Therefore, properly controlling the sulfuric acid pumping rate will help accurately control the pH value during the silicon and aluminum coating stages, thereby improving both silicon and aluminum coating rates. Based on this, and considering the overall improvement in silicon and aluminum coating rates, the sulfuric acid pumping rate in the titanium dioxide silicon and aluminum coating process, conducted at a motor frequency of 50Hz and a reaction temperature of 60-65℃, should ideally be controlled at 9 mL / min.

[0061] Experiment 4: Study on the effect of the pumping rate of titanium dioxide slurry and sodium silicate on the coating rate of silicon and aluminum Based on experiments 1, 2, and 3, the motor frequency was set to 50Hz, the reaction temperature to be between 60-65℃, and the sulfuric acid pumping rate was controlled at 9mL / min. The pumping rates of titanium dioxide slurry and sodium silicate were then controlled to investigate the effects of the mass ratio of titanium dioxide slurry to sodium silicate on silicon coating rate, aluminum coating rate, and residence time. The specific process parameters are shown in Table 7 below.

[0062] Table 7

[0063] The products obtained from the titanium dioxide silicon-coating and aluminum-coating treatments in Examples 9 and 11 to 15 were tested for silicon coating rate and aluminum coating rate, and the residence time was recorded. The results are shown in Table 8 below: Table 8

[0064] As shown in Tables 7 and 8, the ratio of the rate at which titanium dioxide slurry is fed into the reaction unit to that of sodium silicate will have a certain impact on the residence time, especially on the silicon and aluminum coating rates. Appropriate control of the sodium silicate and titanium dioxide slurry pumping rates, combined with a motor frequency of 50Hz, a reaction temperature of 60-65℃, a sulfuric acid pumping rate of 9 mL / min, a sodium aluminate pumping rate of 35.3 mL / min, and an aluminum sulfate pumping rate of 35.8 mL / min, can achieve a silicon coating rate of over 94% and an aluminum coating rate of over 97% by controlling the sodium silicate pumping rate to 173-175 mL / min and the titanium dioxide slurry pumping rate to 61-63 mL / min. The electron microscope image of the product obtained in Example 12 is shown below. Figure 4 , Figure 5 and Figure 6 As shown.

[0065] (V) Laboratory Study on Traditional Interval Method Titanium Dioxide Coating Process A method for interstitial coating of titanium dioxide includes the following steps: Step 1: Place 1.8L of titanium dioxide slurry (300g / L) into a 5L beaker. Add sodium silicate dropwise to the beaker containing the titanium dioxide slurry at a rate of 31mL / min over a period of 20 minutes (620mL of sodium silicate is used). After adding sodium silicate, adjust the pH to 7.5-8.5 by adding 15% sulfuric acid dropwise at a rate of 1.1mL / min, with the addition time reaching 100 minutes (110mL of sulfuric acid is used). During the reaction, maintain the temperature in a water bath at 60-65℃, and stir at 400rpm for 30 minutes until the silicate coating is complete.

[0066] Step 2: Sodium aluminate and aluminum sulfate were added dropwise in parallel to the silica-coated slurry at rates of 6.05 mL / min and 6.08 mL / min, respectively, over a period of 60 min (363 mL of sodium aluminate and 365 mL of aluminum sulfate were used). After the addition was complete, the pH was 9. Then, aluminum sulfate was added dropwise at a rate of 2.7 mL / min to adjust the pH to around 6.0, over a period of 30 min (81 mL of aluminum sulfate was used). During the reaction, a water bath was used to maintain the temperature at 50-60℃, and the stirring was maintained at 400 rpm for 2 hours to obtain silica-coated and aluminum-coated titanium dioxide. The silica coating rate was measured to be 80.37%, and the aluminum coating rate was 91.26%. The electron micrograph of the obtained product is shown below. Figure 2 and Figure 3 As shown.

[0067] II. Research on the improvement of the process phase adaptation device for using sulfuric acid to replace aluminum sulfate.

[0068] Coating with aluminum sulfate is a type of heavy coating, for example... Figure 1 As shown; the process after replacing aluminum sulfate with sulfuric acid is a general coating process, for example, as... Figure 2 As shown.

[0069] (I) Research on Improvement of Device Connection Structure Based on the apparatus described in the above embodiment, the aluminum sulfate tank 16 is replaced with a sulfuric acid tank 18, so that the material pumped into the third reaction unit 4 by the fifth metering pump 13 is sulfuric acid, and the material pumped into the fourth reaction unit 4 by the sixth metering pump 14 is sulfuric acid, forming a new continuous flow coating device for titanium dioxide (e.g. Figure 2(As shown). The specific structure of the obtained device is as follows: it includes four reaction units 4 arranged side by side from left to right. Each reaction unit 4 is provided with a first inlet 1, a second inlet 2, and an outlet 5. The previous reaction unit 4 and the next reaction unit 4 are connected to the first inlet 1 through the outlet 5. The outlet 5 of the rightmost reaction unit 4 is connected to a collection tank 15. From left to right, the second inlet 2 of each reaction unit 4 is connected to a second metering pump 7 for pumping sodium silicate, a third metering pump 11 for pumping sulfuric acid, a fourth metering pump 12 for pumping sodium aluminate, and a sixth metering pump 14 for pumping sulfuric acid. An inlet 19 is provided at the bottom of the third reaction unit 4, and a fifth metering pump 13 for pumping sulfuric acid is connected to the inlet 19. A stirrer is provided inside each reaction unit 4, and a motor 3 is connected to the top of the stirrer extending from the top of the reaction unit 4. The first inlet 1 of the leftmost reaction unit 4 is connected to a first metering pump 6 for pumping titanium dioxide slurry. The first metering pump 6 is connected to a mixing tank 8, which is connected to a titanium dioxide tank 10; the second metering pump 7 is connected to a sodium silicate tank 9; the third metering pump 11, the fifth metering pump 13 and the sixth metering pump 14 are all connected to a sulfuric acid tank 18; and the fourth metering pump 12 is connected to a sodium aluminate tank 17.

[0070] In another embodiment, the first metering pump 6 is equipped with a controller capable of controlling the pumping rate of the first metering pump 6 to be 238.5-262.75 mL / min; the second metering pump 7 is equipped with a controller capable of controlling the pumping rate of the second metering pump 7 to be 27-35 mL / min; the third metering pump 11 is equipped with a controller capable of controlling the pumping rate of the third metering pump 11 to be 5.5-7.1 mL / min; the fourth metering pump 12 is equipped with a controller capable of controlling the pumping rate of the fourth metering pump 12 to be 10-15 mL / min; the fifth metering pump 13 is equipped with a controller capable of controlling the pumping rate of the fifth metering pump 13 to be 18.9-28.5 mL / min; and the sixth metering pump 14 is equipped with a controller capable of controlling the pumping rate of the sixth metering pump 14 to be 12.32 mL / min.

[0071] In another embodiment, the motor 3 is equipped with a frequency converter, and the frequency converter is equipped with a controller capable of controlling the frequency of the motor 3 to 50Hz.

[0072] In another embodiment, a heat exchanger is installed on the reaction unit 4, and a temperature sensor is installed inside the reaction unit 4. The heat exchanger and the temperature sensor are respectively connected to a controller that can control the temperature inside the reaction unit 4 to 90-95°C.

[0073] In another embodiment, the reaction unit 4 allows the titanium dioxide slurry to remain in the leftmost reaction unit 4 for 59-60 minutes until it is discharged from the outlet 5 of the rightmost reaction unit 4.

[0074] Using the process parameters (Example 12*) of Example 12 in the above-mentioned "I. Study on the Adaptation Process Parameters of Titanium Dioxide Continuous Flow Re-coating Device", titanium dioxide was coated with silicon and aluminum. The silicon coating rate and aluminum coating rate of the obtained product were tested, and the results were: silicon coating rate of 91.1% and aluminum coating rate of 89.7%. It can be seen that when the device structure is changed, such that the material pumped into the fifth metering pump 13 and the sixth metering pump 14 is replaced with sulfuric acid with a mass percentage of 15%, the coating effect will decrease.

[0075] In view of this technical problem, our research team, based on the improved device structure, pumped sulfuric acid into the third and fourth reaction units by the fifth metering pump 13 and the sixth metering pump 14, respectively, to form a new coating method for titanium dioxide with silicon and aluminum. We also studied the process parameters that are compatible with the device structure for this coating method.

[0076] (II) Experimental study on process parameters adapted to the improved equipment 1. Raw material information The raw materials used were from "I. Study on the process parameters of the continuous flow heavy coating device for titanium dioxide".

[0077] 2. Research apparatus According to the above-mentioned improved device (such as Figure 2 As shown: A test was conducted using a general coating device for continuous flow of titanium dioxide.

[0078] 3. General Coating Methods for Continuous Flow Titanium Dioxide like Figure 2 As shown, start motor 3 and control the motor frequency to simultaneously pump titanium dioxide slurry and sodium silicate into the leftmost reaction unit 4; when the discharge port 5 of the leftmost reaction unit 4 begins to discharge, pump sulfuric acid into the second reaction unit 4; when the discharge port 5 of the second reaction unit 4 begins to discharge, pump sodium aluminate into the third reaction unit 4 and pump sulfuric acid into the third reaction unit 4; when the discharge port 5 of the third reaction unit 4 begins to discharge, pump sulfuric acid into the fourth reaction unit 4; record the residence time of the titanium dioxide slurry from entering the leftmost reaction unit 4 and exiting from the discharge port 5 of the rightmost reaction unit 4; when stopping the machine, when no material flows out of the discharge port 5, stop pumping sulfuric acid, sodium aluminate, etc., and then stop motor 3.

[0079] 4. Investigation of process parameters 4.1 Study on the effect of reaction temperature on silicon-coated and aluminum-coated coating rates After fixing the motor frequency at 50Hz, the titanium dioxide slurry, sodium silicate, sulfuric acid, sodium aluminate, and reaction temperature were adjusted according to the parameters shown in Table 9 below to prepare titanium dioxide-coated silicon-coated aluminum products.

[0080] Table 9

[0081] The silicon and aluminum coating rates of the products obtained in Table 9 were measured, and the residence time of the entire reaction process was recorded. The results are shown in Table 10 below.

[0082] Table 10

[0083] Based on the data in Tables 9 and 10, combined with Tables 7 and 8, when the improved apparatus follows the process parameters in Example 12* (Example 12), pumping sulfuric acid into the third reaction unit for titanium dioxide coating will lead to a decrease in the quality of the titanium dioxide coated product. Furthermore, under the same process parameters, a reaction temperature of 90-95℃ is superior to a reaction temperature of 85-90℃ for silicon and aluminum coating, while maintaining the same residence time. Therefore, in subsequent investigations into the appropriate process parameters for the improved apparatus, a reaction temperature of 90-95℃ is preferable. In Example 12*, "*" indicates a reference to "Example 12".

[0084] 4.2 Study on the Influence of Motor Frequency on Silicon-Clad and Aluminum-Clad Coating Ratio When the reaction temperature is controlled at 90-95℃, the process parameters for coating titanium dioxide with silicon and aluminum are adjusted according to the parameters shown in Table 11 below to prepare titanium dioxide products coated with silicon and aluminum.

[0085] Table 11

[0086] The aluminum coating rate and silicon coating rate of the products obtained in Examples 17 to 19 were tested, and the residence time was recorded in Table 12 below.

[0087] Table 12

[0088] As shown in Tables 11 and 12, excessively low motor frequencies will lead to a decrease in both silicon and aluminum coating rates, while excessively high motor frequencies result in higher energy consumption. Therefore, considering all factors, the motor frequency is set at 50Hz.

[0089] 4.3 Study on the Influence of Material Pumping Rate on Silicon-Coated and Aluminum-Coated Coating Rates When the reaction temperature is controlled at 90-95℃ and the motor frequency is controlled at 50Hz, the improved device is used for the coating of titanium dioxide with silicon and aluminum. The material pumping rate is adjusted according to the parameters shown in Table 13 below to prepare titanium dioxide products coated with silicon and aluminum.

[0090] Table 13

[0091] The products obtained in Examples 17 and 20 to 29 were tested for silicon coating rate, aluminum coating rate, residence time, pH value at the first inlet of the third reaction unit (three-inlet pH), pH value at the outlet of the third reaction unit (three-outlet pH), and pH value at the outlet of the fourth reaction unit (four-outlet pH). The results are shown in Table 14 below.

[0092] Table 14

[0093] As shown in Tables 13 and 14, when the pumping rates of titanium dioxide slurry are 238.5-262.75 mL / min, sodium silicate is 27-35 mL / min, sulfuric acid is pumped in by the third metering pump at 5.5-7.1 mL / min, sodium aluminate at 10-15 mL / min, sulfuric acid is pumped in by the fifth metering pump at 18.9-28.5 mL / min, and sulfuric acid is pumped in by the sixth metering pump at 12.32 mL / min, and the reaction temperature is controlled at 90-95℃ with a motor frequency of 50 Hz, the reaction residence time of the entire reaction system can be 59.4 min, with a silicon coating rate of over 94% and an aluminum coating rate of over 97%. Figure 8 , Figure 9 and Figure 10 As shown, the film layer of the coated product is continuous, with uniform thickness and good uniformity.

[0094] For any other matters not covered in this invention, they can be implemented by referring to existing technology or common knowledge known to those skilled in the art, and by conventional technical means. For example, the selection of temperature sensors, controllers, heat exchangers, and the fastening and sealing operations during the connection and installation of the device can all be selected, matched, and applied by referring to common knowledge known to those skilled in the art and conventional technical means.

Claims

1. A general coating device for continuous flow of titanium dioxide, characterized in that, The system includes four reaction units (4) connected in series from left to right. Each reaction unit (4) has a first inlet (1), a second inlet (2), and an outlet (5). The previous reaction unit (4) and the next reaction unit (4) are connected to the first inlet (1) via the outlet (5). The outlet (5) of the rightmost reaction unit (4) is connected to a collection tank (15). From left to right, each reaction unit (4) has a second metering pump (7) connected to the second inlet (2) for pumping sodium silicate, and a second metering pump (7) for pumping sodium silicate into the system. A third metering pump (11) for sulfuric acid, a fourth metering pump (12) for pumping sodium aluminate, a sixth metering pump (14) for pumping sulfuric acid, and an inlet (19) at the bottom of the third reaction unit (4), to which a fifth metering pump (13) for pumping sulfuric acid is connected; a stirrer is provided inside the reaction unit (4), and a motor (3) is connected to the top of the stirrer extending from the top of the reaction unit (4); the first feed port (1) of the leftmost reaction unit (4) is connected to a first metering pump (6) for pumping titanium dioxide slurry.

2. The titanium dioxide continuous flow general coating device as described in claim 1, characterized in that, The first metering pump (6) is connected to a mixing tank (8), and the mixing tank (8) is connected to a titanium dioxide tank (10); the second metering pump (7) is connected to a sodium silicate tank (9); the third metering pump (11), the fifth metering pump (13) and the sixth metering pump (14) are all connected to a sulfuric acid tank (18); the fourth metering pump (12) is connected to a sodium aluminate tank (17).

3. The titanium dioxide continuous flow general coating device as described in claim 1, characterized in that, The first metering pump (6) is equipped with a controller capable of controlling the pumping rate of the first metering pump (6) to be 238.5-262.75 mL / min; the second metering pump (7) is equipped with a controller capable of controlling the pumping rate of the second metering pump (7) to be 27-35 mL / min; the third metering pump (11) is equipped with a controller capable of controlling the pumping rate of the third metering pump (11) to be 5.5-7.1 mL / min; the fourth metering pump (12) is equipped with a controller capable of controlling the pumping rate of the fourth metering pump (12) to be 10-15 mL / min; the fifth metering pump (13) is equipped with a controller capable of controlling the pumping rate of the fifth metering pump (13) to be 18.9-28.5 mL / min; and the sixth metering pump (14) is equipped with a controller capable of controlling the pumping rate of the sixth metering pump (14) to be 12.32 mL / min.

4. The titanium dioxide continuous flow general coating device as described in claim 1, characterized in that, The motor (3) is equipped with a frequency converter, and the frequency converter is equipped with a controller that can control the frequency of the motor (3) to be 0-50Hz.

5. The titanium dioxide continuous flow general coating device as described in claim 1, characterized in that, A heat exchanger is installed on the reaction unit (4), and a temperature sensor is installed inside the reaction unit (4). The heat exchanger and the temperature sensor are respectively connected to a controller that can control the temperature inside the reaction unit (4) to 90-95°C.

6. The titanium dioxide continuous flow general coating device as described in claim 3, 4, or 5, characterized in that, The controller is a PLC controller.

7. The titanium dioxide continuous flow general coating device as described in claim 1 or 5, characterized in that, The reaction unit (4) allows the titanium dioxide slurry to remain in the leftmost reaction unit (4) for 59-60 minutes until it is discharged from the outlet (5) of the rightmost reaction unit (4).

8. A general coating method for continuous flow of titanium dioxide, characterized in that, The process of coating titanium dioxide with silicon and aluminum using the apparatus described in any one of claims 1-6 is specifically as follows: A. Prepare a titanium dioxide slurry with a content of 300g / L; take sodium silicate with a content of 100g / L, sulfuric acid with a mass percentage of 15%, sodium aluminate with a content of 160g / L, and aluminum sulfate with a content of 100g / L for later use. B. Turn on the motor (3) and control the temperature inside the reaction unit (4) to 90-95℃. Simultaneously pump the titanium dioxide slurry and sodium silicate into the leftmost reaction unit (4). When the outlet (5) of the leftmost reaction unit (4) starts to discharge, pump sulfuric acid into the second reaction unit (4). When the outlet (5) of the second reaction unit (4) starts to discharge, pump sodium aluminate into the third reaction unit (4) and pump sulfuric acid into the third reaction unit (4). When the outlet (5) of the third reaction unit (4) starts to discharge, pump sulfuric acid into the fourth reaction unit (4). The residence time of the titanium dioxide slurry from entering the leftmost reaction unit (4) and being discharged from the outlet (5) of the rightmost reaction unit (4) is 59-60 minutes.

9. The general coating method for continuous flow of titanium dioxide as described in claim 8, characterized in that, The motor (3) has a frequency of 50Hz.

10. The general coating method for continuous flow of titanium dioxide as described in claim 8, characterized in that, The rate at which the titanium dioxide slurry is pumped in is 238.5-262.75 mL / min; the rate at which the sodium silicate is pumped in is 27-35 mL / min; the rate at which the third metering pump pumps in sulfuric acid is 5.5-7.1 mL / min; the rate at which the sodium aluminate is pumped in is 10-15 mL / min; the rate at which the fifth metering pump pumps in sulfuric acid is 18.9-28.5 mL / min; and the rate at which the sixth metering pump pumps in sulfuric acid is 12.32 mL / min.

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