Process for coating titanium dioxide with low-grade aluminum hydroxide

Abstract

The application discloses a process for coating titanium dioxide with low-grade aluminum hydroxide and belongs to the technical field of sponge titanium preparation. The application aims at solving the problem of high overall cost of coating titanium dioxide with aluminum hydroxide. The application applies the sodium metaaluminate solution prepared from low-grade aluminum hydroxide to coating titanium dioxide, adjusts the alkalinity of the sodium metaaluminate solution, and configures the sodium metaaluminate solution with high concentration and low alkalinity. In the case of maintaining normal levels of various detection indexes of titanium dioxide after coating, the problem that the sodium metaaluminate solution prepared from low-grade aluminum hydroxide is prone to decompose and has a short storage time is solved, and the cost is saved by about 9 yuan / ton.

Description

Technical Field

[0001] This invention belongs to the field of sponge titanium preparation technology, specifically relating to a process for using low-grade aluminum hydroxide for coating titanium dioxide. Background Technology

[0002] Our company uses the sulfuric acid process to produce titanium dioxide. In the post-processing section, also known as the coating section, titanium dioxide particles undergo inorganic treatment to improve their weather resistance, durability, and chemical stability. This compensates for the photochemical activity of titanium dioxide particles and enhances their wetting, dispersion, and rheological properties in various media, allowing titanium dioxide to be better and more uniformly dispersed in different media. Currently, most commercially available rutile titanium dioxide is coated with aluminum or silicon, with aluminum coating being the most common. In addition to forming a protective layer on the surface of titanium dioxide to prevent contact between titanium dioxide and organic media, aluminum coating can also reflect some ultraviolet light, preventing excessive absorption of ultraviolet light and photochemical reactions.

[0003] However, the overall cost of using aluminum hydroxide for titanium dioxide coating is currently high. Therefore, companies need to find an aluminum hydroxide coating process that can reduce costs compared to existing coating processes. Summary of the Invention

[0004] To address the problems in existing technologies, this invention provides a process for using low-grade aluminum hydroxide for titanium dioxide coating. This invention applies a sodium aluminate solution prepared from low-grade aluminum hydroxide to the titanium dioxide coating process, adjusting the alkalinity of the sodium aluminate solution to create a high-concentration, low-alkalinity sodium aluminate solution. This overcomes the problem of sodium aluminate easily decomposing and having a short shelf life due to the low-grade aluminum hydroxide solution, while ensuring that all testing indicators of the titanium dioxide remain at normal levels after coating. This saves approximately 9 yuan / ton in costs.

[0005] The technical solution adopted in this invention is as follows:

[0006] A process for using low-grade aluminum hydroxide for coating titanium dioxide includes the following steps:

[0007] Step 1: Pre-treat the titanium dioxide slurry to make the titanium dioxide concentration in the slurry 350-400 g / L, control the pH value to 9.0-10.0, and the temperature to 45-55℃;

[0008] Step 2: Add diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in Step 1, control the pH value to 9.0-10.0 and the temperature to 60-90℃, and stir to obtain the slurry;

[0009] Step 3: Add aluminum sulfate to the slurry obtained in Step 2, control the pH value to 6.0-8.0, and stir and mature at a temperature of 60-90℃ to obtain the coated titanium dioxide slurry.

[0010] Preferably, in step 2, the proportion of low-grade aluminum hydroxide added to the mixed aluminum hydroxide is 15% to 25% of the proportion of high-grade aluminum hydroxide added.

[0011] Preferably, the sodium aluminate solution is prepared using the following process:

[0012] Step 201: Prepare a sodium hydroxide solution with a mass concentration of 55-60%;

[0013] Step 202: Add mixed aluminum hydroxide raw materials to sodium hydroxide solution, heat to boiling, and wait for the resulting mixture to gradually become clear from turbid. Keep boiling for 40-60 minutes to obtain sodium aluminate solution.

[0014] Preferably, the concentration of the sodium aluminate solution prepared in step 202 is 370-400 g / L (calculated as aluminum oxide), and the sodium aluminate solution contains n 氧化钠 :n 三氧化二铝 The ratio is 1.1 to 1.2:1.

[0015] Preferably, the method for preparing the diluted sodium aluminate solution in step 2 is to dilute the sodium aluminate solution prepared in step 2 to a concentration of 120-130 g / L based on aluminum oxide.

[0016] Preferably, the concentration of aluminum sulfate solution in step 3 is 120-125 g / L, and the addition ratio accounts for 0.5-0.8% of the mass of titanium dioxide in the titanium dioxide slurry.

[0017] Preferably, the amount of diluted sodium aluminate solution added in step 2 is 1.3 to 2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

[0018] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0019] This invention applies a sodium aluminate solution prepared from low-grade aluminum hydroxide to the coating of titanium dioxide. By adjusting the alkalinity of the sodium aluminate solution, a high-concentration, low-alkalinity sodium aluminate solution is prepared. This overcomes the problem that sodium aluminate prepared from low-grade aluminum hydroxide solution is prone to decomposition and has a short shelf life, while ensuring that the various test indicators of titanium dioxide remain at normal levels after coating. This saves approximately 9 yuan / ton in costs. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Therefore, the following detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0021] Examples 1 to 5 and Comparative Examples 1 to 4

[0022] Data recorded as ranges are shown in Table 1 below.

[0023] A process for using low-grade aluminum hydroxide for coating titanium dioxide includes the following steps:

[0024] Step 1: Pre-treat the titanium dioxide slurry to achieve a titanium dioxide concentration of 370 g / L, control the pH value to 9.5, and the temperature to 50℃;

[0025] Step 2: Add diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in Step 1, control the pH value to 9.5 and the temperature to 75℃, and stir to obtain the slurry;

[0026] Step 3: Add aluminum sulfate to the slurry obtained in Step 2, control the pH value to 7.0, and stir and mature at 75℃ to obtain the coated titanium dioxide slurry.

[0027] Preferably, in step 2, the proportion of low-grade aluminum hydroxide added to the mixed aluminum hydroxide is 15% to 25% of the proportion of high-grade aluminum hydroxide added.

[0028] Preferably, the sodium aluminate solution is prepared using the following process:

[0029] Step 201: Prepare a sodium hydroxide solution with a mass concentration of 57%;

[0030] Step 202: Add mixed aluminum hydroxide raw materials to sodium hydroxide solution, heat to boiling, and wait for the resulting mixture to gradually become clear from turbid. Keep boiling for 50 minutes to obtain sodium aluminate solution.

[0031] Preferably, the concentration of the sodium aluminate solution prepared in step 202 is 385 g / L (calculated as aluminum oxide), and the sodium aluminate solution contains n... 氧化钠 :n 三氧化二铝 The ratio is 1.1 to 1.2:1.

[0032] Preferably, the method for preparing the diluted sodium aluminate solution in step 2 is to dilute the sodium aluminate solution prepared in step 2 to a concentration of 125 g / L based on aluminum oxide.

[0033] Preferably, the concentration of aluminum sulfate solution in step 3 is 122 g / L, and the addition ratio accounts for 0.5 to 0.8% of the mass of titanium dioxide in the titanium dioxide slurry.

[0034] Preferably, the amount of diluted sodium aluminate solution added in step 2 is 1.3 to 2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

[0035] Table 1: Data from Examples 1-5 and Comparative Examples 1-4, and quality data of coated titanium dioxide.

[0036]

[0037]

[0038] In this application, the high-grade aluminum hydroxide content is ≥99.5%, the low-grade aluminum hydroxide content is 95%, the high-grade iron content is ≤0.006%, and the low-grade iron content is 0.015%.

[0039] The above examples and comparative examples demonstrate that this invention applies a sodium aluminate solution prepared by mixing low-grade and high-grade aluminum hydroxide to the coating of titanium dioxide. By adjusting the alkalinity of the sodium aluminate solution to prepare a high-concentration, low-alkalinity sodium aluminate solution, the various test indicators of titanium dioxide after coating are maintained at normal levels. This overcomes the problem that sodium aluminate solutions prepared with low-grade aluminum hydroxide are prone to decomposition and have short shelf lives. Furthermore, using low-alkalinity sodium aluminate for titanium dioxide coating reduces the amount of acidic substances used from the source, further reducing costs, environmental pollution, and equipment corrosion, saving approximately 9 yuan / ton. This application, based on the application of the sodium aluminate solution prepared by mixing low-grade and high-grade aluminum hydroxide to titanium dioxide coating, adds aluminum sulfate solution for co-coating. The composite coating of sodium aluminate and aluminum sulfate can form a core-dense film-network film coating structure. This structure can improve the weather resistance and dispersibility of titanium dioxide, further improving the quality of the coating.

[0040] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.

Claims

1. A process for using low-grade aluminum hydroxide for coating titanium dioxide, characterized in that, Includes the following steps: Step 1: Pre-treat the titanium dioxide slurry to make the titanium dioxide concentration in the slurry 350-400 g / L, control the pH value to 9.0-10.0, and the temperature to 45-55℃; Step 2: Add diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in Step 1, control the pH value to 9.0-10.0 and the temperature to 60-90℃, and stir to obtain the slurry; Step 3: Add aluminum sulfate to the slurry obtained in Step 2, control the pH value to 6.0-8.0, and stir and mature at a temperature of 60-90℃ to obtain the coated titanium dioxide slurry; In step 2, the proportion of low-grade aluminum hydroxide added in the mixed aluminum hydroxide is 15% to 25% of the proportion of high-grade aluminum hydroxide added. The sodium aluminate solution was prepared using the following process: Step 201: Prepare a sodium hydroxide solution with a mass concentration of 55-60%; Step 202: Add mixed aluminum hydroxide raw materials to sodium hydroxide solution, heat to boiling, and wait for the resulting mixture to gradually become clear from turbid. Keep boiling for 40-60 minutes to obtain sodium aluminate solution. The concentration of the sodium aluminate solution prepared in step 202, calculated as aluminum oxide, is 370-400 g / L, and the ratio of n sodium oxide to n aluminum oxide in the sodium aluminate solution is 1.1-1.2:

1. The method for preparing the diluted sodium aluminate solution in step 2 is to dilute the sodium aluminate solution prepared in step 2 to a concentration of 120-130 g / L based on aluminum oxide.

2. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 1, characterized in that: The aluminum sulfate solution in step 3 has a concentration of 120–125 g / L and is added at a ratio of 0.5–0.8% of the mass of titanium dioxide in the titanium dioxide slurry.

3. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 1, characterized in that: In step 2, the amount of diluted sodium aluminate solution added is 1.3 to 2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

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