Low-causticity-ratio sodium metaaluminate coating process

Abstract

The invention discloses a low-causticity-ratio sodium metaaluminate coating process, belongs to the technical field of sponge titanium preparation, and aims to solve the problems that sodium metaaluminate with the aluminum oxide content of 99.5 g / l and the causticity ratio of 2.2 is currently prepared by a process for preparing sodium metaaluminate by using a reagent in a company at present; the problems that excessive alkali is used, a large amount of acid is consumed in the coating process to neutralize the alkali, the consumption of the alkali is increased, the acid is also consumed invisibly, and the cost is increased are solved, sodium metaaluminate with low caustic ratio is subjected to composite coating with silicic acid and aluminum sulfate, sodium metaaluminate is prepared by adopting less alkali, the prepared sodium metaaluminate is low in alkali content, and the sodium metaaluminate is easy to dissolve. In the coating process, the low-alkalinity sodium metaaluminate can reduce the neutralization consumption of alkali and acid and reduce the coating cost, and as the neutralization consumption of alkali and acid is reduced, the discharge of finally generated salinity is reduced, the influence on the environment is reduced, and the requirement of sustainable development is met.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium sponge preparation, and in particular relates to a low-causticity sodium aluminate coating process. Background Art

[0002] Through vigorous research and development in the industry, the production of titanium dioxide has made rapid progress in terms of production scale, production capacity, production methods, production technology, product quality, expansion of application areas and control of environmental pollution.

[0003] The company's reagent preparation process for sodium aluminate currently produces sodium aluminate with an alumina content of 99.5g / l and a causticity ratio of 2.2. Excessive alkali is used, and a large amount of acid will be consumed in the coating process to neutralize this part of the alkali, which not only increases the consumption of alkali, but also consumes acid invisibly, increasing costs. Summary of the invention

[0004] In view of the problems in the prior art, the present invention provides a low causticity sodium aluminate coating process. The present application adopts a composite coating of causticity sodium aluminate with silicic acid and aluminum sulfate, and uses less alkali to prepare sodium aluminate. The prepared sodium aluminate has a low alkali content. During the coating process, low-alkalinity sodium aluminate will reduce the neutralization consumption of alkali and acid, reduce the coating cost, and since the neutralization consumption of alkali and acid is reduced, the final salinity emission is reduced, the impact on the environment is reduced, and the requirements of sustainable development are met.

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

[0006] A low causticity sodium aluminate coating process 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 silicic acid to the titanium dioxide slurry, controlling the pH value of the slurry to 2.0-3.5, the temperature to 50-70° C., and stirring to obtain slurry a;

[0009] Step 3: adding a sodium aluminate solution with a caustic ratio of 1.65 to 1.75 to slurry a, controlling the pH value to 9.0 to 10.0, the temperature to 60 to 90° C., and stirring to obtain slurry b;

[0010] Step 4: Add aluminum sulfate to slurry b, control the pH value to 6.0-8.0, and stir and mature at 60-90° C. to obtain coated titanium dioxide slurry.

[0011] Preferably, the low causticity sodium aluminate solution prepared in step 3 is prepared by the following preparation process:

[0012] Step 301: heating and stirring the liquid sodium hydroxide, maintaining the temperature at 60-70° C. during the stirring process;

[0013] Step 302: adding the pre-calculated aluminum hydroxide powder and solid sodium hydroxide to the heated liquid sodium hydroxide under constant temperature stirring;

[0014] Step 303: maintaining a constant temperature and stirring to allow the aluminum hydroxide powder and the liquid alkali to fully react; during the reaction process, the temperature is raised to boiling again and maintained at a constant temperature for 1 to 2 hours;

[0015] Step 304: After the reaction is completed, adjust the caustic ratio to the target value;

[0016] Step 305: Cool the reacted material and mix it with neutral water and liquid alkali according to the requirements of the final product until the required caustic ratio and concentration are reached.

[0017] Preferably, the concentration of the silicic acid solution in step 2 is 120-125 g / L, and the added proportion accounts for 2-2.8% of the mass of titanium dioxide in the titanium dioxide slurry.

[0018] Preferably, the concentration of the sodium aluminate 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.

[0019] Preferably, the amount of aluminum sulfate solution added in step 4 is 1.3-2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] 1. The present application adopts a composite coating of sodium aluminate with low causticity ratio and silicic acid and aluminum sulfate, and uses less alkali to prepare sodium aluminate. The prepared sodium aluminate has a low alkali content. During the coating process, sodium aluminate with low alkalinity will reduce the neutralization consumption of alkali and acid, reduce the coating cost, and because the neutralization consumption of alkali and acid is reduced, the final salinity emission is reduced, the impact on the environment is reduced, and the requirements of sustainable development are met;

[0022] 2. The present application adopts aluminum sulfate to adjust the pH of the slurry after sodium aluminate coating, so that the addition of aluminum sulfate can achieve a double balance with respect to the addition of sodium aluminate in terms of aluminum content and pH value, that is, the composite addition ratio of aluminum sulfate and sodium aluminate and the pH can reach the value most conducive to coating; the specific principle is that aluminum sulfate is acidic and can be adjusted to lower the pH value of titanium dioxide slurry. At the same time, aluminum sulfate treatment can be conducive to the growth of titanium dioxide primary particles in the tetragonal crystal system, thereby enhancing the stability and performance of titanium dioxide, and improving the light scattering efficiency of titanium dioxide, thereby improving the covering power of the coating. Finally, while achieving the pH adjustment ability, the amount of titanium dioxide in the coating formula can be reduced, and the same or even better covering effect can be achieved at a lower cost. DETAILED DESCRIPTION

[0023] 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 in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown here can be arranged and designed in various configurations. 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.

[0024] Examples 1 to 7

[0025] A low caustic ratio sodium aluminate coating process comprises the following steps (see Table 1 for some material addition data):

[0026] 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.;

[0027] Step 2: adding silicic acid to the titanium dioxide slurry, controlling the pH value of the slurry to 2.7, the temperature to 60° C., and stirring to obtain slurry a;

[0028] Step 3: adding a sodium aluminate solution with a caustic ratio of 1.65 to 1.75 to slurry a, controlling the pH value to 9.5 and the temperature to 75° C., and stirring to obtain slurry b;

[0029] Step 4: Add aluminum sulfate to slurry b, control the pH value to 7, and stir and mature at 75°C to obtain coated titanium dioxide slurry.

[0030] In this embodiment, the sodium aluminate solution prepared in step 3 is prepared by the following preparation process:

[0031] Step 301: heating and stirring liquid sodium hydroxide, maintaining the temperature at 65° C. during stirring;

[0032] Step 302: adding the pre-calculated aluminum hydroxide powder and solid sodium hydroxide to the heated liquid sodium hydroxide under constant temperature stirring;

[0033] Step 303: maintaining constant temperature and stirring to allow the aluminum hydroxide powder and the liquid alkali to fully react; during the reaction process, the temperature is raised to boiling again and maintained at a constant temperature for 1.5 hours;

[0034] Step 304: After the reaction is completed, adjust the caustic ratio to the target value;

[0035] Step 305: Cool the reacted material and mix it with neutral water and liquid alkali according to the requirements of the final product until the required caustic ratio and concentration are reached.

[0036] In this embodiment, the concentration of the silicic acid solution in step 2 is 122 g / L, and the added ratio accounts for 2.4% of the mass of titanium dioxide in the titanium dioxide slurry.

[0037] In this embodiment, the concentration of the sodium aluminate solution in step 3 is 122 g / L, and the addition ratio accounts for 0.5-0.8% of the mass of titanium dioxide in the titanium dioxide slurry.

[0038] In this embodiment, the amount of aluminum sulfate solution added in step 4 is 1.3-2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

[0039] Table 1: Data table of some material additions in Examples 1 to 7

[0040]

[0041] Comparative Example 1

[0042] Titanium dioxide particles, water and dispersant are mixed, dispersed by beating and sand grinding, and then sieved to obtain a pre-coating slurry with a concentration of 370g / l; the temperature of the slurry is maintained at 50°C; the pH of the slurry is adjusted to 9.5, and sodium aluminate and dilute acid with a caustic ratio of 2.2 are added to the slurry, and the pH of the slurry is maintained at 9.5 and the temperature is maintained at 75°C during the addition process; after the addition is completed, dilute acid is added to adjust the pH of the slurry to 9, and the first aging is carried out at 75°C; then dilute acid is added to adjust the pH of the slurry to 7, and the second aging is carried out at 75°C. After the fully matured slurry is sieved, filtered, and washed, an organic silane coupling agent is added for organic treatment, and after being stirred evenly, it is dried and crushed.

[0043] Comparative Example 2

[0044] Titanium dioxide particles, water and dispersant are mixed, dispersed by beating and sand grinding, and then sieved to obtain a pre-coating slurry with a concentration of 370g / l; the temperature of the slurry is maintained at 50°C; the pH of the slurry is adjusted to 9.5, and sodium aluminate and dilute acid with a caustic ratio of 1.25 are added to the slurry, and the pH of the slurry is maintained at 9.5 and the temperature is maintained at 75°C during the addition process; after the addition is completed, dilute acid is added to adjust the pH of the slurry to 9, and the first aging is carried out at 75°C; then dilute acid is added to adjust the pH of the slurry to 7, and the second aging is carried out at 75°C. After the fully matured slurry is sieved, filtered, and washed, an organic silane coupling agent is added for organic treatment, and after being stirred evenly, it is dried and crushed.

[0045] Comparative Example 3

[0046] The difference between this comparative example and Example 1 is that in step 3, a low caustic ratio sodium aluminate solution with a caustic ratio of 1.25 is added to slurry a.

[0047] The coated titanium dioxide obtained in Examples 1 to 7 and Comparative Examples 1 to 3 was subjected to a QUVA aging performance test. A UVA (340) lamp was used as the light source. The sample was placed in a UV aging machine. The test conditions met the blackboard temperature of (60±2)°C and the irradiance of 0.68W / m 2 , condensation temperature (45±2)℃, test cycle period 8 hours, 4 hours of illumination / 4 hours of condensation, continuous ultraviolet accelerated light aging for 1000 hours, and the data in Table 1 below are obtained.

[0048] Table 2 Data table of light aging performance indexes of titanium dioxide obtained in Examples 1 to 7 and Comparative Examples 1 to 3 (after aging for 1000 hours in an ultraviolet accelerated aging tester)

[0049]

[0050] The refractive index of the titanium dioxide in Examples 1 to 7 and Comparative Examples 1 to 3 was tested according to the standard of GB / T 1706-2006 to detect the light scattering ability of the titanium dioxide. The specific refractive index of the titanium dioxide obtained is shown in Table 3 below.

[0051] Table 3 Refractive index test data of titanium dioxide obtained in Examples 1 to 7 and Comparative Examples 1 to 3

[0052]

[0053] It can be seen from the experimental data in Tables 2 and 3 that the present application achieves a dual balance in terms of aluminum content and pH value by adding aluminum sulfate, thereby optimizing the coating effect; the acidic properties of aluminum sulfate enable it to effectively reduce the pH value of the titanium dioxide slurry, and the composite coating of aluminum sulfate and sodium aluminate simultaneously promotes the growth of titanium dioxide primary particles according to the tetragonal crystal system, which not only enhances the stability, light resistance and other weather resistance of titanium dioxide, but also improves the light scattering efficiency, the whiteness and glossiness of titanium dioxide and the covering power of the coating; and while maintaining the covering effect of the coating formula, it reduces the amount of titanium dioxide used, reduces the production cost, and achieves more economical and efficient coating production.

[0054] 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 low causticity sodium aluminate coating process, 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 silicic acid to the titanium dioxide slurry, controlling the pH value of the slurry to 2.0-3.5, the temperature to 50-70° C., and stirring to obtain slurry a; Step 3: adding a sodium aluminate solution with a caustic ratio of 1.65 to 1.75 to slurry a, controlling the pH value to 9.0 to 10.0, the temperature to 60 to 90° C., and stirring to obtain slurry b; Step 4: Add aluminum sulfate to slurry b, control the pH value to 6.0-8.0, and stir and mature at 60-90° C. to obtain coated titanium dioxide slurry.

2. A low causticity sodium aluminate coating process according to claim 1, characterized in that: The sodium aluminate solution prepared in step 3 is prepared by the following preparation process: Step 301: heating and stirring liquid sodium hydroxide, maintaining the temperature at 60-70° C. during stirring; Step 302: adding the pre-calculated aluminum hydroxide powder and solid sodium hydroxide to the heated liquid sodium hydroxide under constant temperature stirring; Step 303: maintaining a constant temperature and stirring to allow the aluminum hydroxide powder and the liquid alkali to fully react; during the reaction process, the temperature is raised to boiling again and maintained at a constant temperature for 1 to 2 hours; Step 304: After the reaction is completed, adjust the caustic ratio to the target value; Step 305: Cool the reacted material and mix it with neutral water and liquid alkali according to the requirements of the final product until the required caustic ratio and concentration are reached.

3. A low causticity sodium aluminate coating process according to claim 1, characterized in that: The concentration of the silicic acid solution in step 2 is 120-125 g / L, and the added proportion accounts for 2-2.8% of the mass of titanium dioxide in the titanium dioxide slurry.

4. A low caustic ratio sodium aluminate coating process according to claim 1, characterized in that: The concentration of the sodium aluminate 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.

5. A low causticity sodium aluminate coating process according to claim 1, characterized in that: In step 4, the amount of aluminum sulfate solution added is 1.3-2.6% of the mass of titanium dioxide in the titanium dioxide slurry.

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