Process for coating titanium dioxide with low-grade aluminum hydroxide

Abstract

The invention discloses a process for coating titanium dioxide by using low-grade aluminum hydroxide, belongs to the technical field of sponge titanium preparation, and aims to solve the problem that the overall cost of coating titanium dioxide by using aluminum hydroxide at present is relatively high. According to the method, the alkalinity of the sodium metaaluminate solution is lowered, the high-concentration and low-alkalinity sodium metaaluminate solution is prepared, under the condition that all detection indexes of the coated titanium dioxide are kept at normal levels, the problems that the sodium metaaluminate solution prepared from low-grade aluminum hydroxide easily causes easy decomposition of sodium metaaluminate and is short in preservation time are solved, and the cost is saved by about 9 yuan / ton.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium sponge preparation, and specifically relates to a process for using low-grade aluminum hydroxide for titanium dioxide coating. Background Art

[0002] Our company uses the sulfuric acid method to produce titanium dioxide. In the post-processing section, also known as the coating section, the titanium dioxide particles are subjected to inorganic treatment to improve the weather resistance, durability and chemical stability of titanium dioxide, make up for the defects of the photochemical activity of titanium dioxide particles, and improve its wetting, dispersion and rheological properties in various media, so that titanium dioxide can be better and more evenly dispersed in various media; most of the rutile titanium dioxide currently available on the market is coated with aluminum or silicon, among which aluminum coating is the most common; in addition to forming a protective layer on the surface of titanium dioxide to isolate titanium dioxide from contact with organic media, aluminum coating can also reflect part of the ultraviolet rays to prevent titanium dioxide from absorbing too much ultraviolet rays and causing photochemical reactions.

[0003] However, the overall cost of using aluminum hydroxide to coat titanium dioxide is relatively high, so companies need to find a lower-cost aluminum hydroxide coating process based on the existing coating process. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a process for using low-grade aluminum hydroxide for titanium dioxide coating. The present invention applies a sodium aluminate solution prepared from low-grade aluminum hydroxide to titanium dioxide coating, lowers the alkalinity of the sodium aluminate solution, and configures it into a high-concentration, low-alkalinity sodium aluminate solution. While ensuring that various detection indicators of titanium dioxide after coating are maintained at normal levels, the problem that the sodium aluminate solution prepared from low-grade aluminum hydroxide is easy to cause sodium aluminate to decompose easily and has a short storage time is overcome, thereby saving costs of about 9 yuan / ton.

[0005] The technical solution adopted by the present invention is as follows:

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

[0007] Step 1: pretreating titanium dioxide slurry to make the titanium dioxide concentration in the titanium dioxide slurry be 350-400 g / L, controlling the pH value to be 9.0-10.0, and the temperature to be 45-55° C.;

[0008] Step 2: adding a diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in step 1, controlling the pH value to 9.0-10.0, the temperature to 60-90° C., and stirring to obtain a 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 60-90° C. to obtain coated titanium dioxide slurry.

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

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

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

[0013] Step 202: Add the mixed aluminum hydroxide raw material to the sodium hydroxide solution, heat to boiling, wait for the obtained mixed solution to gradually become clear from turbid, keep boiling for 40 to 60 minutes, and obtain a sodium aluminate solution.

[0014] Preferably, the concentration of the sodium aluminate solution prepared in step 202 is 370-400 g / L in terms of aluminum oxide, and n 氧化钠 :n 三氧化二铝 It is 1.1~1.2:1.

[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 to 130 g / L in terms of aluminum oxide.

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

[0017] Preferably, the amount of the diluted sodium aluminate solution added in step 2 is 1.3-2.6% 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] The present invention applies a sodium aluminate solution prepared from low-grade aluminum hydroxide to titanium dioxide coating, lowers the alkalinity of the sodium aluminate solution, and configures it into a sodium aluminate solution with high concentration and low alkalinity. While ensuring that various detection indicators of titanium dioxide after coating are maintained at normal levels, the problem that the sodium aluminate solution configured from low-grade aluminum hydroxide is easy to cause sodium aluminate to decompose easily and has a short storage time is overcome, thereby saving costs by about 9 yuan / ton. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Therefore, the following detailed description of the embodiments of the present application is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work belong to the scope of protection of the present application.

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

[0022] Some of the data recorded as ranges are shown in Table 1 below

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

[0024] Step 1: pretreating the titanium dioxide slurry to make the titanium dioxide concentration in the titanium dioxide slurry 370 g / L, controlling the pH value to 9.5 and the temperature to 50° C.;

[0025] Step 2: adding a diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in step 1, controlling the pH value to 9.5 and the temperature to 75° C., and stirring to obtain a 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°C to obtain the coated titanium dioxide slurry.

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

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

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

[0030] Step 202: Add the mixed aluminum hydroxide raw material to the sodium hydroxide solution, heat to boiling, wait until the resulting mixed solution gradually changes from turbid to clear, keep boiling for 50 minutes, and obtain a sodium aluminate solution.

[0031] Preferably, the concentration of the sodium aluminate solution prepared in step 202 is 385 g / L in terms of aluminum oxide, and n 氧化钠 :n 三氧化二铝 It is 1.1~1.2:1.

[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 in terms of aluminum oxide.

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

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

[0035] Table 1: Data of Examples 1 to 5 and Comparative Examples 1 to 4 and quality data record of titanium dioxide after coating

[0036]

[0037]

[0038] In the present 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 embodiments and comparative examples show that the present invention applies a sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to titanium dioxide coating, lowers the alkalinity of the sodium aluminate solution, and configures it into a high-concentration, low-alkalinity sodium aluminate solution. While ensuring that various detection indicators of titanium dioxide after coating are maintained at normal levels, the problem that the sodium aluminate solution configured with low-grade aluminum hydroxide is easy to cause sodium aluminate to decompose easily and has a short shelf life is overcome, and the use of low-alkalinity sodium aluminate for titanium dioxide coating reduces the amount of acid substances from the source, further reduces costs, reduces environmental pollution, reduces equipment corrosion, and saves costs of about 9 yuan / ton. The present application adds an aluminum sulfate solution to cooperate with the coating on the basis of applying a sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to titanium dioxide coating. The composite coating of sodium aluminate and aluminum sulfate can form a coating structure of inner core-dense film-net film, which can improve the weather resistance and dispersibility of titanium dioxide and further improve the quality of the coating.

[0040] The above-mentioned embodiments only express the specific implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the protection scope of the present application. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the technical solution concept of the present application, and these all belong to the protection scope of the present application.

Claims

1. A process for using low-grade aluminum hydroxide for titanium dioxide coating, characterized in that: The following steps are involved: Step 1: pretreating titanium dioxide slurry to make the titanium dioxide concentration in the titanium dioxide slurry be 350-400 g / L, controlling the pH value to be 9.0-10.0, and the temperature to be 45-55° C.; Step 2: adding a diluted sodium aluminate solution prepared by mixing low-grade aluminum hydroxide and high-grade aluminum hydroxide to the slurry obtained in step 1, controlling the pH value to 9.0-10.0, the temperature to 60-90° C., and stirring to obtain a 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 60-90° C. to obtain coated titanium dioxide slurry.

2. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 1, characterized in that: In step 2, the addition ratio of low-grade aluminum hydroxide in the mixed aluminum hydroxide is 15% to 25% of the addition ratio of high-grade aluminum hydroxide.

3. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 1, characterized in that: The sodium aluminate solution is prepared by the following preparation process: Step 201: preparing a sodium hydroxide solution with a mass concentration of 55-60%; Step 202: Add the mixed aluminum hydroxide raw material to the sodium hydroxide solution, heat to boiling, wait for the obtained mixed solution to gradually become clear from turbid, keep boiling for 40 to 60 minutes, and obtain a sodium aluminate solution.

4. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 3, characterized in that: The concentration of the sodium aluminate solution prepared in step 202 is 370-400 g / L in terms of aluminum oxide. 氧化钠 :n 三氧化二铝 It is 1.1~1.2:

1.

5. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 3, characterized in that: The preparation method of the diluted sodium aluminate solution in step 2 is to dilute the sodium aluminate solution prepared in step 2 to a concentration of 120 to 130 g / L in terms of aluminum oxide.

6. The process for using low-grade aluminum hydroxide for titanium dioxide coating according to claim 1, characterized in that: The concentration of the 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.

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

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