Method for improving the coating rate of titanium dioxide produced by chlorination process

Abstract

The application relates to the technical field of titanium white production, and discloses a method for improving the coating rate of titanium white produced by the chlorination method, which comprises the following steps: preparing slurry by mixing titanium white produced by the chlorination method, a dispersing agent and deionized water, and performing dispersion treatment on the slurry, wherein the pH value of the slurry is controlled to be 2.0-5.0; adjusting the slurry after the dispersion treatment to a predetermined concentration and a predetermined temperature; performing inorganic coating treatment on the slurry after the adjustment under different pH conditions, wherein the inorganic coating treatment comprises acidic parallel-flow coating of a silicon-aluminum composite film, forward-flow coating of a silicon film, alkaline parallel-flow coating of a silicon-aluminum composite film, forward-flow coating of an aluminum film and neutral parallel-flow coating of a silicon-aluminum composite film; and performing organic treatment on the material after the multiple inorganic coating treatments to obtain titanium white products. The slurry of the titanium white produced by the chlorination method is directly dispersed under acidic conditions and inorganic coating treatment is performed under different pH conditions, so that the coating rate of the titanium white can be improved, and the pigment performance and application performance of the titanium white products can be improved.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide production technology, and specifically to a method for improving the coating rate of chloride-process titanium dioxide. Background Technology

[0002] Titanium dioxide is a white pigment with very stable physical and chemical properties. It is non-toxic and harmless, and has excellent optical properties such as high refractive index, optimal opacity, optimal whiteness and brightness. It is widely used in coatings, plastics, papermaking, inks, electronics and other fields.

[0003] The main production processes for titanium dioxide include the sulfuric acid process and the chloride process. The chloride process has seen rapid development in recent years due to its advantages such as high product quality, high added value, advanced technology, environmental friendliness, and continuous production. The chloride process mainly includes a chlorination refining step, an oxidation step, and a surface post-treatment step. The properties of the titanium dioxide raw material produced in the oxidation step directly affect the surface post-treatment effect, thus impacting the quality of the titanium dioxide product. Currently, the oxidation step involves oxidizing titanium tetrachloride to titanium dioxide, followed by cooling and gas-solid separation to obtain the raw titanium dioxide. Residual chlorine gas in the raw titanium dioxide increases the acidity of the system when it enters the titanium dioxide slurry. During subsequent alkaline milling and dispersion, this increases alkali consumption, forming salts and increasing the viscosity of the slurry. This causes some fine particles to re-aggregate into coarse particles, resulting in uneven particle surface coating, or even incomplete coating of some particles, making it difficult to improve the coating rate and ultimately affecting the pigment performance and application performance of the titanium dioxide product.

[0004] Therefore, how to improve the coating rate of titanium dioxide produced by the chloride process has become an urgent problem to be solved. Summary of the Invention

[0005] The main objective of this invention is to provide a method for improving the coating rate of titanium dioxide produced by the chloride process, thereby solving the technical problem of how to improve the coating rate of titanium dioxide produced by the chloride process.

[0006] According to one aspect of the present invention, a method for improving the coating rate of chloride-process titanium dioxide is provided, comprising the following steps: S10, preparing a slurry from chloride-process titanium dioxide raw material, a dispersant, and deionized water, and dispersing the slurry, wherein the pH value of the slurry is controlled to be 2.0-5.0; S20, adjusting the dispersed slurry to a predetermined concentration and a predetermined temperature; S30, subjecting the adjusted slurry to inorganic coating treatment under different pH conditions, wherein the inorganic coating treatment includes acidic co-current coating of silicon-aluminum composite film, co-current coating of silicon film, alkaline co-current coating of silicon-aluminum composite film, co-current coating of aluminum film, and neutral co-current coating of silicon-aluminum composite film; S40, subjecting the material after multiple inorganic coating treatments to organic treatment to obtain titanium dioxide product.

[0007] According to one embodiment of the present invention, step S30 includes: S31, adding a silicate solution, an acidic aluminum salt solution, and a pH adjuster concurrently to the adjusted slurry to control the pH value of the slurry to 4.0-5.0 for a first maturation; S32, adding a silicate solution to the slurry after the first maturation and adjusting the pH value of the slurry to 9.0-10.0 for a second maturation; S33, adding a silicate solution, an acidic aluminum salt solution, and a pH adjuster concurrently to the slurry after the second maturation and controlling the pH value of the slurry to 9.0-10.0 for a third maturation; S34, adding an acidic aluminum salt solution to the slurry after the third maturation and adjusting the pH value of the slurry to 6.5-7.5 for a fourth maturation; S35, adding a silicate solution, an acidic aluminum salt solution, and a pH adjuster concurrently to the slurry after the fourth maturation and controlling the pH value of the slurry to 6.5-7.5 for a fifth maturation.

[0008] According to one embodiment of the present invention, in step S31, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the adjusted slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the adjusted slurry, calculated as aluminum oxide; the co-current addition time is 60-180 min; and the first curing time is 60-120 min.

[0009] According to one embodiment of the present invention, in step S32, the amount of silicate solution added is 0.5%-1.0% of the mass of titanium dioxide in the slurry after the first curing, calculated as silicon dioxide, and the addition time is 20-60 min, and the second curing time is 10-30 min.

[0010] According to one embodiment of the present invention, in step S33, the amount of silicate solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95°C; the co-current addition time is 60-120 min; and the third curing time is 30-90 min.

[0011] According to one embodiment of the present invention, in step S34, the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the third aging slurry, calculated as aluminum oxide, and the addition time is 20-60 min. The fourth aging time is 10-30 min.

[0012] According to one embodiment of the present invention, in step S35, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the fourth curing slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the fourth curing slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95°C; the co-current addition time is 60-180 min; and the fifth curing time is 60-120 min.

[0013] According to one embodiment of the present invention, the mass ratio of the amount of silicon coating in step S31, the amount of silicon coating in step S33, and the amount of silicon coating in step S35 is (1-6):1:(1-6).

[0014] According to one embodiment of the present invention, the mass concentration of the silicate solution in steps S31, S32, S33, and S35, calculated as silicon dioxide, is 100-300 g / L; the mass concentration of the acidic aluminum salt solution in steps S31, S33, S34, and S35 is 80-120 g / L; and the predetermined concentration of titanium dioxide in step S20 is 300-400 g / L, and the predetermined temperature is 60-70°C.

[0015] According to one embodiment of the present invention, the dispersant is at least one selected from sodium hexametaphosphate, sodium polycarboxylate, ammonium citrate, polyacrylamide and polyacrylic acid, and the amount of dispersant added is 0.2%-0.8% of the initial mass of the chloride-process titanium dioxide.

[0016] In the technical solution of this invention, the primary titanium dioxide product of the chloride process, the dispersant and deionized water are made into a slurry and dispersed under acidic conditions. This can reduce the formation of salts, lower the viscosity of the primary titanium dioxide slurry of the chloride process, improve the dispersion stability of titanium dioxide particles in the slurry, and improve the coating rate by performing multiple inorganic coating treatments, thereby improving the pigment performance and application performance of the titanium dioxide product. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A flowchart illustrating a method for improving the coating rate of chloride-process titanium dioxide according to an embodiment of the present invention is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0020] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0021] refer to Figure 1 This invention proposes a method for improving the coating rate of chloride-process titanium dioxide, comprising the following steps: S10 involves preparing a slurry from primary titanium dioxide produced by the chloride process, a dispersant, and deionized water, and then dispersing the slurry while controlling the pH value of the slurry to be 2.0-5.0. S20, adjust the dispersed slurry to a predetermined concentration and temperature; S30, inorganic coating treatment is performed on the adjusted slurry under different pH conditions, including acidic co-current coating of silicon-aluminum composite membrane, co-current coating of silicon membrane, alkaline co-current coating of silicon-aluminum composite membrane, co-current coating of aluminum membrane and neutral co-current coating of silicon-aluminum composite membrane. S40 involves organically treating materials that have undergone multiple inorganic coating processes to obtain titanium dioxide products.

[0022] In the technical solution of this invention, the primary titanium dioxide product of the chloride process, the dispersant and deionized water are made into a slurry and dispersed under acidic conditions. This can reduce the formation of salts, lower the viscosity of the primary titanium dioxide slurry of the chloride process, improve the dispersion stability of titanium dioxide particles in the slurry, and improve the coating rate by performing multiple inorganic coating treatments, thereby improving the pigment performance and application performance of the titanium dioxide product.

[0023] In step S10, the dispersion treatment may include sand milling. Deionized water for pulping can be added to a pulping tank, the agitator and pH meter are started, and the primary titanium dioxide product collected via a bag filter and a certain amount of dispersant are added. After stirring evenly, the mixture is sand-milled and sieved. The dispersant can be at least one of sodium hexametaphosphate, sodium polycarboxylate, ammonium citrate, polyacrylamide, and polyacrylic acid. The amount of dispersant added can be 0.2%-0.8% of the primary titanium dioxide product weight.

[0024] In step S20, the predetermined concentration of titanium dioxide can be 300-400 g / L, and the predetermined temperature can be 60-70℃. The slurry after sand milling and sieving can be fed into the coating device, diluted with deionized water, the stirring device can be started, the temperature of the diluted slurry can be heated and maintained at 60-70℃, and the concentration of titanium dioxide in the diluted slurry can be controlled to be 300-400 g / L.

[0025] The inorganic coating process in step S30 may include: co-current coating of silicon-aluminum composite film under acidic conditions, co-current coating of silicon film, co-current coating of silicon-aluminum composite film under alkaline conditions, co-current coating of aluminum film, and co-current coating of silicon-aluminum composite film under neutral conditions.

[0026] In some embodiments, step S30 includes the following sub-steps: S31, add silicate solution, acidic aluminum salt solution and pH adjuster (alkaline or acidic solution, such as sodium hydroxide solution or dilute hydrochloric acid) to the adjusted slurry in parallel to control the pH value of the slurry to 4.0-5.0 for the first maturation; S32, Add silicate solution to the slurry after the first maturation and adjust the pH of the slurry to 9.0-10.0, and carry out the second maturation; S33, silicate solution, acidic aluminum salt solution and pH adjuster are added in parallel to the slurry after the second maturation to control the pH value of the slurry to 9.0-10.0, and then the third maturation is carried out; S34, add acidic aluminum salt solution to the slurry after the third maturation and adjust the pH of the slurry to 6.5-7.5, and carry out the fourth maturation; S35, silicate solution, acidic aluminum salt solution and pH adjuster are added concurrently to the slurry after the fourth maturation to control the pH value of the slurry to 6.5-7.5, and then the fifth maturation is carried out.

[0027] This invention utilizes a gradient pH of acidic → alkaline → neutral, alternating co-current and parallel-current, and multi-layer progressive coating to form a highly adherent bottom layer, a continuously growing intermediate layer, and a stable surface layer. This reduces exposed sites, eliminates coating dead zones, and improves the uniformity, integrity, and density of the film, thereby increasing the coating rate of chloride-process titanium dioxide.

[0028] In some embodiments, in step S31, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the adjusted slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the adjusted slurry, calculated as aluminum oxide; the co-current addition time is 60-180 min; and the first curing time is 60-120 min.

[0029] In some embodiments, in step S32, the amount of silicate solution added is 0.5%-1.0% of the mass of titanium dioxide in the slurry after the first curing, calculated as silicon dioxide, and the addition time is 20-60 min, while the second curing time is 10-30 min.

[0030] In some embodiments, in step S33, the amount of silicate solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95°C; the co-current addition time is 60-120 min; and the third curing time is 30-90 min.

[0031] In some embodiments, in step S34, the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the third aging slurry, calculated as aluminum oxide, and the addition time is 20-60 min, while the fourth aging time is 10-30 min.

[0032] In some embodiments, in step S35, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the fourth curing slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the fourth curing slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95°C; the co-current addition time is 60-180 min; and the fifth curing time is 60-120 min.

[0033] In some embodiments, the mass ratio of the amount of silicon encapsulation in step S31, the amount of silicon encapsulation in step S33, and the amount of silicon encapsulation in step S35 is (1-6):1:(1-6).

[0034] In some embodiments, the silicate solution in steps S31, S32, S33, and S35 has a mass concentration of 100-300 g / L, calculated as silicon dioxide. In some embodiments, the acidic aluminum salt solution in steps S31, S33, S34, and S35 has a mass concentration of 80-120 g / L. The acidic aluminum salt solution can be at least one of aluminum chloride solution, aluminum sulfate solution, and aluminum nitrate solution.

[0035] In step S40, the slurry after multiple inorganic coating treatments (the slurry after the fifth maturation) can be filtered and washed to obtain a filter cake. Then, the filter cake is subjected to organic treatment, dried and pulverized to obtain titanium dioxide products.

[0036] The following description is based on specific embodiments and comparative examples.

[0037] Example 1 Add 1700g of deionized water to the pulping tank, start the agitator and pH meter, add 1000g of primary titanium dioxide collected through a bag filter and 2.0g of polyacrylic acid, stir evenly and then perform sand milling and sieving to control the pH value of the pulp to 2.0-5.0.

[0038] The slurry after sand milling and sieving is fed into the coating device, and deionized water is added to dilute it to a titanium dioxide concentration of 300 g / L. The stirring device is started, and the temperature of the diluted slurry is heated and maintained at 60-70℃.

[0039] Within 60 minutes, 100 g / L sodium silicate solution, 80 g / L aluminum chloride solution, and 10 wt% sodium hydroxide solution were added concurrently to the diluted slurry to control the pH of the slurry to 4.0-5.0. The amount of sodium silicate solution added was 0.5% of the mass of titanium dioxide in the diluted slurry based on silicon dioxide, and the amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the diluted slurry based on aluminum oxide. The first maturation was carried out for 60 minutes.

[0040] Within 20 minutes, add 100 g / L sodium silicate solution to the slurry after the first maturation and adjust the pH of the slurry to 9.0-10.0. The amount of sodium silicate solution added is 0.5% of the mass of titanium dioxide in the slurry after the first maturation, based on silicon dioxide. Then carry out the second maturation for 10 minutes.

[0041] Within 60 minutes, 100 g / L sodium silicate solution, 80 g / L aluminum chloride solution, and 10 wt% sodium hydroxide solution were added concurrently to the slurry after the second maturation. The pH of the slurry was controlled at 9.0-10.0, and the temperature at 85-95℃. The amount of sodium silicate solution added was 0.5% of the mass of titanium dioxide in the slurry after the second maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the slurry after the second maturation, calculated as aluminum oxide. A third maturation was then carried out for 30 minutes.

[0042] Within 20 minutes, add 80 g / L aluminum chloride solution to the slurry after the third maturation and adjust the pH of the slurry to 6.5-7.5. The amount of aluminum chloride solution added is 0.5% of the mass of titanium dioxide in the slurry after the third maturation, calculated as aluminum oxide. Then carry out the fourth maturation for 10 minutes.

[0043] Within 60 minutes, 100 g / L sodium silicate solution, 80 g / L aluminum chloride solution, and 10 wt% sodium hydroxide solution were added concurrently to the slurry after the fourth maturation. The pH of the slurry was controlled at 6.5-7.5, and the temperature at 85-95℃. The amount of sodium silicate solution added was 0.5% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as aluminum oxide. The fifth maturation was then carried out for 60 minutes.

[0044] The slurry after the fifth maturation was filtered and washed to obtain a filter cake. The filter cake was then subjected to organic treatment, dried and pulverized to obtain titanium dioxide products.

[0045] Example 2 Add 1700g of deionized water to the pulping tank, start the agitator and pH meter, add 1000g of primary titanium dioxide collected by the chloride process through a bag filter, 1.0g of sodium hexametaphosphate and 2.0g of polyacrylamide, stir evenly and then perform sand milling and sieving to control the pH value of the pulp to 2.0-5.0.

[0046] The slurry after sand milling and sieving is fed into the coating device, and deionized water is added to dilute it to a titanium dioxide concentration of 350 g / L. The stirring device is started, and the temperature of the diluted slurry is heated and maintained at 60-70℃.

[0047] Within 90 minutes, 200 g / L sodium silicate solution, 100 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the diluted slurry to control the pH of the slurry to 4.0-5.0. The amount of sodium silicate solution added was 2% of the mass of titanium dioxide in the diluted slurry based on silicon dioxide, and the amount of aluminum chloride solution added was 1.0% of the mass of titanium dioxide in the diluted slurry based on aluminum oxide. The first maturation was carried out for 90 minutes.

[0048] Within 40 minutes, add 200 g / L sodium silicate solution to the slurry after the first maturation and adjust the pH of the slurry to 9.0-10.0. The amount of sodium silicate solution added is 0.8% of the mass of titanium dioxide in the slurry after the first maturation, based on silicon dioxide. Then carry out the second maturation for 20 minutes.

[0049] Within 90 minutes, 200 g / L sodium silicate solution, 100 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the slurry after the second maturation. The pH of the slurry was controlled at 9.0-10.0, and the temperature at 85-95℃. The amount of sodium silicate solution added was 1.0% of the mass of titanium dioxide in the slurry after the second maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the slurry after the second maturation, calculated as aluminum oxide. A third maturation was then carried out for 60 minutes. Within 20 minutes, 100 g / L aluminum chloride solution was added to the slurry after the third maturation, and the pH of the slurry was adjusted to 6.5-7.5. The amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the slurry after the third maturation, calculated as aluminum oxide. A fourth maturation was then carried out for 10 minutes.

[0050] Within 120 minutes, 200 g / L sodium silicate solution, 100 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the slurry after the fourth maturation. The pH of the slurry was controlled at 6.5-7.5, and the temperature at 85-95℃. The amount of sodium silicate solution added was 3.0% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 1.0% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as aluminum oxide. The fifth maturation was then carried out for 120 minutes.

[0051] The slurry after the fifth maturation was filtered and washed to obtain a filter cake. The filter cake was then subjected to organic treatment, dried and pulverized to obtain titanium dioxide products.

[0052] Example 3 Add 1700g of deionized water to the pulping tank, start the agitator and pH meter, add 1000g of primary titanium dioxide collected by the chloride process through a bag filter, 1.5g of ammonium citrate and 1.5g of sodium polycarboxylate, stir evenly and then perform sand milling and sieving to control the pH value of the pulp to 2.0-5.0.

[0053] The slurry after sand milling and sieving is fed into the coating device, and deionized water is added to dilute it to a titanium dioxide concentration of 400 g / L. The stirring device is started, and the temperature of the diluted slurry is heated and maintained at 60-70℃.

[0054] Within 180 minutes, 300 g / L sodium silicate solution, 120 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the diluted slurry to control the pH of the slurry to 4.0-5.0. The amount of sodium silicate solution added was 3.0% of the mass of titanium dioxide in the diluted slurry based on silicon dioxide, and the amount of aluminum chloride solution added was 2.0% of the mass of titanium dioxide in the diluted slurry based on aluminum oxide. The first curing was carried out for 120 minutes.

[0055] Within 60 minutes, add 300 g / L sodium silicate solution to the slurry after the first maturation and adjust the pH of the slurry to 9.0-10.0. The amount of sodium silicate solution added is 1.0% of the mass of titanium dioxide in the slurry after the first maturation, based on silicon dioxide. Then carry out the second maturation for 30 minutes.

[0056] Within 120 minutes, 300 g / L sodium silicate solution, 120 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the slurry after the second maturation. The pH of the slurry was controlled at 9.0-10.0 and the temperature at 85-95℃. The amount of sodium silicate solution added was 2.0% of the mass of titanium dioxide in the slurry after the second maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 0.5% of the mass of titanium dioxide in the slurry after the second maturation, calculated as aluminum oxide. A third maturation was then carried out for 60 minutes.

[0057] Within 60 minutes, add 120 g / L aluminum chloride solution to the slurry after the third maturation and adjust the pH of the slurry to 6.5-7.5. The amount of aluminum chloride solution added is 0.5% of the mass of titanium dioxide in the slurry after the third maturation, calculated as aluminum oxide. Then carry out the fourth maturation for 30 minutes.

[0058] Within 90 minutes, 300 g / L sodium silicate solution, 120 g / L aluminum chloride solution, and 10 wt% hydrochloric acid solution were added concurrently to the slurry after the fourth maturation. The pH of the slurry was controlled at 6.5-7.5, and the temperature at 85-95℃. The amount of sodium silicate solution added was 2.0% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as silicon dioxide, and the amount of aluminum chloride solution added was 1.0% of the mass of titanium dioxide in the slurry after the fourth maturation, calculated as aluminum oxide. The fifth maturation was then carried out for 90 minutes.

[0059] The slurry after the fifth maturation was filtered and washed to obtain a filter cake. The filter cake was then subjected to organic treatment, dried and pulverized to obtain titanium dioxide products.

[0060] Comparative Example 1 Add 1700g of deionized water to the pulping tank, start the agitator and pH meter, add 1000g of primary titanium dioxide collected by the chloride process through a bag filter, add 10wt% sodium hydroxide solution to adjust the pH of the slurry to 9.0-10.0, add 3.0g of sodium silicate dispersant, stir evenly, and then perform sand milling and sieving.

[0061] The slurry after sand milling and sieving is fed into the coating device, and deionized water is added to dilute it to a titanium dioxide concentration of 300 g / L. The stirring device is started, and the temperature of the diluted slurry is heated and maintained at 80-85℃.

[0062] Add 100 g / L sodium silicate solution to the diluted slurry within 30 minutes. The amount of sodium silicate solution added is 2.0% of the mass of titanium dioxide in the diluted slurry, calculated as silicon dioxide. Perform the first curing for 30 minutes.

[0063] Add 10wt% hydrochloric acid solution to the slurry after the first maturation within 60 minutes and adjust the pH of the slurry to 4.0-5.0, and carry out the second maturation for 60 minutes.

[0064] Within 60 minutes, add 80 g / L sodium aluminate solution and 10 wt% hydrochloric acid solution concurrently to the slurry after the second maturation. Control the pH of the slurry to be 4.0-5.0 and the temperature to be 60-65℃. The amount of sodium aluminate solution added is 2.0% of the mass of titanium dioxide in the slurry after the second maturation, calculated as aluminum oxide. Then carry out the third maturation for 60 minutes.

[0065] Within 30 minutes, add 10 wt% sodium hydroxide solution to the slurry after the third maturation and adjust the pH of the slurry to 6.5-7.5. Then carry out the fourth maturation, which takes 60 minutes.

[0066] The slurry after the fourth maturation is filtered and washed to obtain a filter cake. The filter cake is then subjected to organic treatment, dried and pulverized to obtain titanium dioxide products.

[0067] The silicon and aluminum content of the primary titanium dioxide obtained by the chloride process, the titanium dioxide prepared in Examples 1-3 and Comparative Example 1 above, was determined using X-ray fluorescence spectrometry. The results are shown in Table 1. Table 1. Silicon and aluminum coating rates of titanium dioxide

[0068] As shown in Table 1, the titanium dioxide prepared by the method for improving the coating rate of chloride-process titanium dioxide provided by the present invention has a coating rate of ≥90%, which is better than that of Comparative Example 1.

[0069] In summary, the method of the present invention for improving the coating rate of titanium dioxide produced by the chloride process involves directly introducing a dispersant into the primary titanium dioxide slurry system for acidic sand milling dispersion. This reduces the formation of salts during alkaline sand milling dispersion, lowers the viscosity of the primary titanium dioxide slurry, and improves the dispersion stability of titanium dioxide particles in the slurry. Furthermore, the use of a silicon-aluminum co-precipitation process to coat silicon and aluminum films under different pH conditions helps to improve the coating rate, thereby enhancing the pigment performance and application performance of the titanium dioxide product.

[0070] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for improving the coating rate of chloride-process titanium dioxide, characterized in that, Includes the following steps: S10, the primary product of titanium dioxide produced by the chloride process, a dispersant and deionized water are prepared into a slurry and the slurry is dispersed, wherein the pH value of the slurry is controlled to be 2.0-5.0; S20, adjust the dispersed slurry to a predetermined concentration and temperature; S30, inorganic coating treatment is performed on the adjusted slurry under different pH conditions, including acidic co-current coating of silicon-aluminum composite membrane, co-current coating of silicon membrane, alkaline co-current coating of silicon-aluminum composite membrane, co-current coating of aluminum membrane and neutral co-current coating of silicon-aluminum composite membrane. S40 involves organically treating materials that have undergone multiple inorganic coating processes to obtain titanium dioxide products.

2. The method according to claim 1, characterized in that, Step S30 includes: S31, silicate solution, acidic aluminum salt solution and pH adjuster are added concurrently to the adjusted slurry to control the pH value of the slurry to 4.0-5.0 for the first maturation; S32, Add silicate solution to the slurry after the first maturation and adjust the pH of the slurry to 9.0-10.0, and carry out the second maturation; S33, silicate solution, acidic aluminum salt solution and pH adjuster are added in parallel to the slurry after the second maturation to control the pH value of the slurry to 9.0-10.0, and then the third maturation is carried out; S34, add acidic aluminum salt solution to the slurry after the third maturation and adjust the pH of the slurry to 6.5-7.5, and carry out the fourth maturation; S35, silicate solution, acidic aluminum salt solution and pH adjuster are added concurrently to the slurry after the fourth maturation to control the pH value of the slurry to 6.5-7.5, and then the fifth maturation is carried out.

3. The method according to claim 2, characterized in that, In step S31, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the adjusted slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the adjusted slurry, calculated as aluminum oxide; the co-current addition time is 60-180 min; and the first curing time is 60-120 min.

4. The method according to claim 2, characterized in that, In step S32, the amount of silicate solution added is 0.5%-1.0% of the mass of titanium dioxide in the slurry after the first curing, calculated as silicon dioxide, and the addition time is 20-60 min. The second curing time is 10-30 min.

5. The method according to claim 2, characterized in that, In step S33, the amount of silicate solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-2.0% of the mass of titanium dioxide in the second curing slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95℃; the co-current addition time is 60-120 min; and the third curing time is 30-90 min.

6. The method according to claim 2, characterized in that, In step S34, the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the third aging slurry, calculated as aluminum oxide, and the addition time is 20-60 min. The fourth aging time is 10-30 min.

7. The method according to claim 2, characterized in that, In step S35, the amount of silicate solution added is 0.5%-3.0% of the mass of titanium dioxide in the fourth aging slurry, calculated as silicon dioxide; the amount of acidic aluminum salt solution added is 0.5%-1.0% of the mass of titanium dioxide in the fourth aging slurry, calculated as aluminum oxide; the temperature of the slurry is controlled at 85-95℃; the co-current addition time is 60-180 min; and the fifth aging time is 60-120 min.

8. The method according to claim 2, characterized in that, The mass ratio of the silicon coating amount in step S31, step S33, and step S35 is (1-6):1:(1-6).

9. The method according to claim 2, characterized in that, The silicate solution in steps S31, S32, S33, and S35 has a mass concentration of 100-300 g / L based on silicon dioxide; the acidic aluminum salt solution in steps S31, S33, S34, and S35 has a mass concentration of 80-120 g / L; and the titanium dioxide in step S20 has a predetermined concentration of 300-400 g / L and a predetermined temperature of 60-70°C.

10. The method according to claim 1, characterized in that, The dispersant is at least one of sodium hexametaphosphate, sodium polycarboxylate, ammonium citrate, polyacrylamide, and polyacrylic acid, and the amount of dispersant added is 0.2%-0.8% of the initial mass of the chloride-process titanium dioxide.

Images