Acid-deficient aluminum sulfate coating process

Abstract

The invention discloses an acid-deficient aluminum sulfate coating process, belongs to the technical field of titanium dioxide production, and solves the problems that in the prior art, excessive 98% H2SO4 and Al2 (SO4) 3 are used for neutralization reaction, and a prepared aluminum sulfate reagent is relatively high in acid content; in order to solve the technical problems in the prior art that more alkali needs to be added to neutralize acid in an aluminum sulfate reagent, acid-deficient aluminum sulfate and sodium silicate are adopted for composite coating, the pH value and the temperature value of the whole reaction system are controlled, it is ensured that a uniform and compact aluminum sulfate film is formed on the surface of titanium dioxide, and a non-uniform coating may be caused by too little or too much sulfuric acid; by accurately controlling the use amount of sulfuric acid, the glossiness of titanium dioxide is improved as much as possible, and the raw material cost can be directly reduced by reducing the use amount of sulfuric acid; and the cost saving can be obviously accumulated in large-scale production, so that the economic benefits of enterprises are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium dioxide production, and in particular relates to an acid-deficient aluminum sulfate coating process. Background Art

[0002] Aluminum sulfate coating technology is used to improve the performance of pigments such as titanium dioxide, such as improving gloss, hiding power and weather resistance. By coating the surface of titanium dioxide with a dense aluminum oxide film, its surface properties are changed to meet the needs of different applications. Aluminum sulfate, as an inorganic treatment agent, can be used together with water glass to form a coating on the surface of pigments such as barium sulfate particles to improve dispersibility and reduce production costs. Aluminum sulfate coating technology helps reduce wastewater discharge and equipment investment, while simplifying the process flow to achieve environmentally friendly production.

[0003] In the titanium dioxide production process, the preparation of aluminum sulfate reagent uses an excess of 98% H2SO4 and Al2(SO4)3 for neutralization reaction. Although Al2(SO4)3 will react completely, the prepared aluminum sulfate reagent has a high acid content. During coating, the pH needs to be controlled within a certain range at all times, which results in the need to add more alkali to neutralize the acid in the aluminum sulfate reagent when controlling the pH value. If the previous method is followed, not only will the excess 98% H2SO4 be wasted, but also a large amount of 32% NaOH will be consumed, and some by-products and waste acid and waste water will be produced, increasing cost consumption. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides an under-acidified aluminum sulfate coating process, which can directly reduce the raw material cost by reducing the amount of sulfuric acid used; and this cost saving can be significantly accumulated in large-scale production, thereby improving the economic benefits of the enterprise; the present application adopts under-acidified aluminum sulfate and sodium aluminate for two parallel-flow composite coatings, controls the pH and temperature of the entire reaction system, ensures that a uniform and dense aluminum sulfate film is formed on the surface of titanium dioxide, and too little or too much sulfuric acid may lead to uneven coating; by precisely controlling the amount of sulfuric acid used, the glossiness of titanium dioxide is improved as much as possible.

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

[0006] A process for coating an acid-deficient aluminum sulfate film comprises the following steps:

[0007] Step 1: First, disperse the titanium dioxide particles in water, add a dispersant, and control the temperature to 55-65°C to achieve the best dispersion state;

[0008] Step 2: Grinding the slurry obtained in step 1 to disperse the agglomerated titanium dioxide particles to obtain a pretreated titanium dioxide slurry with a concentration of 240 to 300 g / L;

[0009] Step 3: adding sodium aluminate to the titanium dioxide slurry obtained in step 2 to obtain slurry a;

[0010] Step 4: adding under-acidified aluminum sulfate and sodium metaaluminate to slurry a in parallel, controlling the pH value of the slurry to be 3.2-3.5, the temperature to be 55-65° C., and stirring to obtain slurry b;

[0011] Step 5: Add underacidified aluminum sulfate and sodium aluminate to slurry b for the second time in parallel, control the pH value of the slurry to 9.5-9.8, maintain the temperature at 55-65° C., stir to obtain slurry c, and stir and mature.

[0012] Preferably, the acid content of the acid-deficient aluminum sulfate in step 3 or 4 is ≤2%.

[0013] Preferably, the under-acid aluminum sulfate prepared in step 3 or 4 is prepared by the following preparation process:

[0014] Step a: Evenly mix aluminum hydroxide and 98% sulfuric acid;

[0015] Step b: After the reaction is complete, the generated aluminum sulfate solution is precipitated and then solid-liquid separation is performed to obtain an under-acid aluminum sulfate solution.

[0016] Preferably, the concentration of the under-acidified aluminum sulfate solution in step 4 is 90±5 g / L, and the addition ratio is 1:98-102 by mass ratio of titanium dioxide in the titanium dioxide slurry; the addition ratio of sodium aluminate is 1.2:100 by mass ratio of titanium dioxide in the titanium dioxide slurry.

[0017] Preferably, the concentration of the under-acidified aluminum sulfate solution in step 5 is 90±5 g / L, the addition ratio is 1:48-52 to the mass ratio of titanium dioxide in the titanium dioxide slurry, and the addition ratio of sodium aluminate is 2.5:100 to the mass ratio 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] 1. Sulfuric acid is one of the main raw materials in the coating process. Reducing the amount of sulfuric acid can directly reduce the cost of raw materials; and this cost saving can be significantly accumulated in large-scale production, improving the economic benefits of the enterprise;

[0020] 2. Excessive use of sulfuric acid may cause wastewater treatment problems. Using less sulfuric acid can reduce the treatment and discharge of sulfuric acid and its byproducts such as sulfates, thereby reducing the impact on the environment and the risk of water acidification;

[0021] 3. The present application adopts the method of introducing under-acid aluminum sulfate and sodium aluminate for parallel composite coating. Since under-acid aluminum sulfate is acidic, the pH and temperature of the entire reaction system are fine-tuned during the coating process to ensure that a uniform and dense aluminum sulfate film is formed on the surface of titanium dioxide.

[0022] 4. Too little or too much sulfuric acid may lead to uneven coating. The present application maintains two parallel coatings and accurately controls the amount of under-acidified aluminum chlorate and sodium metaaluminate added in multiple steps, thereby maximizing the brightness of titanium dioxide.

[0023] 5. The present application optimizes the amount of sulfuric acid used in the preparation of aluminum sulfate and reduces the time for neutralization with alkali, thereby improving the reaction efficiency. At the same time, it ensures that the reaction between aluminum sulfate and titanium dioxide is more complete, reduces the unreacted sulfuric acid residue, and thus improves the overall conversion rate and efficiency of the coating process; reducing the amount of sulfuric acid requires more precise process control, such as pH adjustment, reaction time, temperature and stirring speed; this fine control helps to develop more advanced coating technology and improve product consistency and reliability. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0025] A process for coating an acid-deficient aluminum sulfate film comprises the following steps:

[0026] Step 1: First, disperse the titanium dioxide particles in water, add a dispersant, and control the temperature to about 55-65°C to achieve the best dispersion state;

[0027] Step 2: Grinding the slurry obtained in step 1 to disperse the agglomerated titanium dioxide particles to obtain a pretreated titanium dioxide slurry with a concentration of 240 to 300 g / L;

[0028] Step 3: adding sodium aluminate to the titanium dioxide slurry obtained in step 2 to obtain slurry a;

[0029] Step 4: adding under-acidified aluminum sulfate and sodium metaaluminate to slurry a in parallel, controlling the pH value of the slurry to be 3.2-3.5, the temperature to be 55-65° C., and stirring to obtain slurry b;

[0030] Step 5: Add underacidified aluminum sulfate and sodium aluminate to slurry b for the second time in parallel, control the pH value of the slurry to 9.5-9.8, maintain the temperature at 55-65° C., stir to obtain slurry c, and stir and mature.

[0031] Wherein, in step 4, pre-acid aluminum sulfate is used to adjust the pH; in step 5, sodium aluminate is used to adjust the pH.

[0032] In this embodiment, the acid content of the under-acid aluminum sulfate in step 3 or 4 is ≤2%.

[0033] In this embodiment, the under-acid aluminum sulfate prepared in step 3 or 4 is prepared by the following preparation process:

[0034] Step a: Evenly mix aluminum hydroxide and 98% sulfuric acid;

[0035] Step b: After the reaction is complete, the generated aluminum sulfate solution is precipitated and then solid-liquid separation is performed to obtain an under-acid aluminum sulfate solution.

[0036] In this embodiment, the concentration of the under-acidified aluminum sulfate solution in step 4 is 90±5 g / L, and the addition ratio is 1:98-102 by mass ratio of titanium dioxide in the titanium dioxide slurry; the addition ratio of sodium aluminate is 1.2:100 by mass ratio of titanium dioxide in the titanium dioxide slurry.

[0037] In this embodiment, the concentration of the under-acidified aluminum sulfate solution in step 5 is 90±5 g / L, the addition ratio is 1:48-52 to the mass ratio of titanium dioxide in the titanium dioxide slurry, and the addition ratio of sodium aluminate is 2.5:100 to the mass ratio of titanium dioxide in the titanium dioxide slurry.

[0038] Some data in Examples 1 to 8 are shown in Table 1 below

[0039] Table 1 Partial data record table in Examples 1 to 8

[0040]

[0041] Table 2 Glossiness experimental data and coating cost saving per ton of titanium dioxide in Examples 1 to 8 Among them, the cost saving basis of this application is the cost consumed per ton of titanium dioxide in Example 8.

[0042]

[0043] The present application optimizes the amount of sulfuric acid used in the preparation of aluminum sulfate and reduces the time for neutralization with alkali, thereby improving the reaction efficiency, while ensuring a more complete reaction between aluminum sulfate and titanium dioxide and reducing unreacted sulfuric acid residue, thereby improving the overall conversion rate and efficiency of the coating process; reducing the amount of sulfuric acid requires more precise process control, such as pH adjustment, reaction time, temperature and stirring speed; such fine control helps to develop more advanced coating technology and improve product consistency and reliability.

[0044] It should be noted that:

[0045] 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 coating an acid-deficient aluminum sulfate film, characterized in that: The following steps are involved: Step 1: First, disperse the titanium dioxide particles in water, add a dispersant, and control the temperature to 55-65°C to achieve the best dispersion state; Step 2: Grinding the slurry obtained in step 1 to disperse the agglomerated titanium dioxide particles to obtain a pretreated titanium dioxide slurry with a concentration of 240 to 300 g / L; Step 3: adding sodium aluminate to the titanium dioxide slurry obtained in step 2 to obtain slurry a; Step 4: adding under-acidified aluminum sulfate to slurry a, controlling the pH value of the slurry to be 3.2-3.5, the temperature to be 55-65° C., and stirring to obtain slurry b; Step 5: Add sodium aluminate to slurry b, control the pH value of the slurry to 9.5-9.8, maintain the temperature at 55-65° C., stir to obtain slurry c, and stir and mature.

2. A kind of under-acid aluminum sulfate coating process according to claim 1, it is characterized in that: The acid content of the under-acidified aluminum sulfate in step 3 or 4 is ≤2%.

3. A kind of under-acid aluminum sulfate coating process according to claim 1, it is characterized in that: The under-acid aluminum sulfate prepared in step 3 or 4 is prepared by the following preparation process: Step a: Evenly mix aluminum hydroxide and 98% sulfuric acid; Step b: After the reaction is complete, the generated aluminum sulfate solution is precipitated and then solid-liquid separation is performed to obtain an under-acid aluminum sulfate solution.

4. A kind of under-acid aluminum sulfate coating process according to claim 1, it is characterized in that: The concentration of the under-acidified aluminum sulfate solution in step 4 is 90±5 g / L, and the addition ratio is 1:98-102 by mass ratio of titanium dioxide in the titanium dioxide slurry; the addition ratio of sodium aluminate is 1.2:100 by mass ratio of titanium dioxide in the titanium dioxide slurry.

5. A kind of under-acid aluminum sulfate coating process according to claim 1, it is characterized in that: The concentration of the under-acidified aluminum sulfate solution in step 5 is 90±5 g / L, the addition ratio is 1:48-52 by mass ratio of titanium dioxide in the titanium dioxide slurry, and the addition ratio of sodium aluminate is 2.5:100 by mass ratio of titanium dioxide in the titanium dioxide slurry.

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