Preparation method of spherical alumina powder with good dispersity

Abstract

The application discloses a preparation method of spherical alumina powder with good dispersity, and comprises the following steps: dissolving aluminum nitrate nonahydrate and ammonium sulfate in deionized water, adding sodium hydroxide, polysiloxane-polyester sulfonate dispersant and urea in sequence, stirring, and configuring into a reaction solution; then, the reaction solution is subjected to temperature increasing reaction under stirring at a certain temperature increasing rate; after the reaction is completed, the spherical alumina precursor is prepared through filtering, washing and drying treatment; finally, the prepared spherical alumina precursor is subjected to calcination according to a certain calcination process, and the spherical alumina is obtained after cooling. The spherical alumina prepared by the method has the advantages of smooth surface, good dispersity, controllable particle size (D50 is about 1-8 microns), easily obtained raw materials, simple process, low requirement on production equipment and easy industrialization.

Description

Technical Field

[0001] This invention belongs to the field of inorganic powder technology, specifically relating to a method for preparing alumina powder, and particularly to a method for preparing spherical alumina powder with good dispersibility. Background Technology

[0002] In recent years, with the rapid development of global industry, the role of powder materials has become increasingly prominent, among which alumina powder is one of the most important powder materials in industrial production. Alumina powder possesses high thermal conductivity and good chemical stability, such as high temperature resistance, high hardness, and good insulation properties, making it widely used in many fields such as electronics, machinery, ceramics, medicine, and aerospace, resulting in a large market demand. Compared to ordinary alumina powder, spherical alumina powder also has properties such as regular morphology, high bulk density, small specific surface area, good filling properties, and strong flowability, thus having a wider range of applications. Therefore, the preparation of spherical alumina powder has been one of the research hotspots in recent years.

[0003] Methods for preparing spherical alumina include high-temperature gas-phase methods, template methods, aerosol decomposition methods, sol-gel methods, hydrothermal methods, drop ball methods, homogeneous precipitation methods, and ball milling methods, but each of these methods has its shortcomings. For example, CN110697746A describes a method for preparing submicron-sized spherical alumina powder using thermal plasma. This method uses a carrier gas to transport aluminum powder and alumina into a thermal plasma reactor, causing the aluminum powder and alumina to vaporize and deposit, thus obtaining spherical alumina powder. However, this method requires stringent preparation conditions, expensive equipment, and regular maintenance, resulting in high production costs. CN114408953A describes a method for preparing spherical α-alumina by ball milling. This method involves horizontally ball milling α-alumina with milling beads at a speed of 350-500 r / min for 20-40 h to obtain spherical α-alumina. This method is simple to operate, has low production costs, and is easy to industrialize. However, the surface of the obtained spherical alumina powder is relatively rough, with an increased specific surface area and increased powder activity, making the powder particles prone to agglomeration, thus limiting its application range. CN109911923A describes a method for preparing high-purity spherical aluminum hydroxide and alumina nanoparticles. This method uses aluminum alkoxide as a raw material, mixing it with a mixed solution composed of surfactant, pH adjuster, alcohol, and high-purity water for hydrolysis. After stirring and reaction, solid-liquid separation and drying are performed to obtain aluminum hydroxide powder; calcination yields alumina powder. This method uses simple equipment, is convenient to operate, and uses readily available raw materials. However, aluminum alkoxide is expensive, resulting in high production costs. Furthermore, the organic solvents generated during the reaction process can cause environmental pollution.

[0004] Homogeneous precipitation is a common method for preparing spherical alumina, producing powders with high purity and smooth surfaces. However, the resulting powder products exhibit severe agglomeration, and the particle size is difficult to control through process parameters. To overcome these problems, this invention improves upon the traditional homogeneous precipitation method, producing spherical alumina with smooth surfaces, good dispersibility, and controllable particle size. Furthermore, the raw materials used are readily available, the process is simple, the production equipment requirements are low, and it is easily industrialized. Summary of the Invention

[0005] To overcome the problems of expensive equipment, high production costs, and high agglomeration in existing methods for preparing spherical alumina powder, this invention provides a method for preparing spherical alumina powder with good dispersibility.

[0006] The method for preparing a well-dispersible spherical alumina powder according to the present invention includes the following steps:

[0007] (1) Dissolve aluminum nitrate nonahydrate and ammonium sulfate in deionized water in proportion, and then add a certain amount of sodium hydroxide, a certain amount of polysiloxane-polyester sulfonate dispersant and a certain amount of urea in sequence under stirring to prepare a reaction solution.

[0008] (2) The reaction solution is heated to a certain temperature under stirring conditions at a certain heating rate. After the reaction is completed, the solution is filtered, washed and dried to obtain spherical alumina precursor.

[0009] (3) The prepared spherical alumina precursor is calcined according to a certain calcination process, and spherical alumina is obtained after cooling.

[0010] The structural formula of the polysiloxane-polyester sulfonate dispersant in step (1) is:

[0011]

[0012] x is 25-35, y is 30-40, and z is 4-8.

[0013] The polysiloxane-polyester sulfonate dispersant in step (1) can be prepared as follows: 12g of sodium isophthalic acid-5-sulfonate, 48g of isophthalic acid, 50g of diethylene glycol, and 0.12g of butyltin acid are added to a four-necked flask. Nitrogen gas is introduced, and the temperature is raised to 140°C at a stirring speed of 200r / min. After the solution in the flask becomes transparent, the temperature is raised to 200°C and the reaction continues for 1.5h. Then, 30g of hydroxyl silicone oil is added to the flask, the nitrogen gas is stopped, and a vacuum pump is connected to evacuate the flask. The temperature is then raised to 220°C and the reaction continues for 2.5h. The reaction is then stopped, and the product is discharged while hot to obtain the polysiloxane-polyester sulfonate dispersant.

[0014] In step (1), the mass ratio of aluminum nitrate nonahydrate to ammonium sulfate is 10-3:1, and the sum of the masses of aluminum nitrate nonahydrate and ammonium sulfate accounts for 1.88-18.76% of the mass of solution A.

[0015] In step (1), the mass of sodium hydroxide is 1.6%-6.4% of the mass of aluminum nitrate nonahydrate.

[0016] In step (1), the amount of polysiloxane-polyester sulfonate dispersant added is 1.0%-4.0% of the sum of the mass of aluminum nitrate nonahydrate and ammonium sulfate.

[0017] In step (1), the amount of urea added is 160%-320% of the mass of aluminum nitrate nonahydrate.

[0018] In step (1), the stirring speed is 300-500 r / min, the stirring time after adding sodium hydroxide is 20-40 min, the stirring time after adding polysiloxane-polyester sulfonate dispersant is 20-40 min, and the stirring time after adding urea is 20-40 min.

[0019] The stirring speed in step (2) is 200-600 r / min; the heating rate is 0.8-2.0℃ / min; the reaction temperature is 90-120℃; and the holding time is 300-900 min.

[0020] The calcination process in step (3) involves heating at a rate of 5-10℃ / min to reach a calcination temperature of 600-1200℃, holding at that temperature for 60-300 minutes, and then cooling down with the furnace.

[0021] The principle of the preparation method of the well-dispersible spherical alumina powder of the present invention is as follows: (1) First, after adding sodium hydroxide to the solution of aluminum nitrate nonahydrate and ammonium sulfate, sodium hydroxide combines with aluminum ions in the solution to generate active crystal nuclei of aluminum hydroxide. The number of active crystal nuclei is controlled by controlling the amount of sodium hydroxide added, preferably with a small number of active crystal nuclei in the solution; then, the added urea slowly decomposes during the heating process, causing the initially generated active crystal nuclei to grow slowly, thereby obtaining spherical alumina precursor. It is worth noting that the particle size of the powder can be controlled by controlling the amount of sodium hydroxide added and the decomposition rate of urea. By controlling the amount of sodium hydroxide added, the number of active crystal nuclei generated in the solution can be controlled. Then, when the urea slowly decomposes, the precipitated products cause the existing active crystal nuclei to grow, reducing the phenomenon of re-nucleation, thereby achieving the purpose of controlling the particle size of the product.

[0022] (2) Secondly, a self-designed polysiloxane-polyester sulfonate was added to the solution as a dispersant. The sulfonic acid group in the dispersant can form strong hydrogen bonds with the surface of the alumina precursor and is easily adsorbed onto the powder surface. At the same time, the sulfonic acid group utilizes the electrostatic stabilization effect to further increase the repulsive force between powders, which inhibits agglomeration to a certain extent. The polyester segment in the dispersant is polar and can induce and pull the newly precipitated alumina precursor to deposit on the active crystal nucleus. The polysiloxane segment in the dispersant further lengthens the molecular chain, increases the steric hindrance and generates repulsive force, thereby inhibiting agglomeration and strengthening dispersion.

[0023] The key technical points and beneficial effects of this invention are as follows:

[0024] 1. This invention introduces a self-designed polysiloxane-polyester sulfonate as a dispersant, which results in the preparation of spherical alumina precursors and spherical alumina with good dispersibility, no agglomeration, smooth surface, and better filling properties.

[0025] 2. This invention achieves controllable spherical alumina particle size D50 of 1-8 micrometers by adding sodium hydroxide as a crystal nucleation inducer and intelligently controlling the temperature rise to slow decomposition of urea.

[0026] 3. The preparation process of the spherical alumina of the present invention is simple, has low equipment requirements, low energy consumption in the production process, meets environmental protection requirements, and is easy to industrialize. Attached Figure Description

[0027] Figure 1 Scanning electron microscope (SEM) image of spherical alumina prepared in Example 1 of this method.

[0028] Figure 2 Scanning electron microscope (SEM) image of spherical alumina prepared in Example 2 of this method.

[0029] Figure 3 Scanning electron microscope (SEM) image of spherical alumina prepared in Example 3 of this method.

[0030] Figure 4 Scanning electron microscope (SEM) image of spherical alumina prepared in Example 4 of this method.

[0031] Figure 5 This is a scanning electron microscope (SEM) image of the alumina prepared by Comparative Example 1 using this method.

[0032] Figure 6 This is a scanning electron microscope (SEM) image of the alumina prepared by Comparative Example 2 using this method.

[0033] Figure 7 This is a scanning electron microscope (SEM) image of the alumina prepared by Comparative Example 3 using this method. Detailed Implementation

[0034] The present invention will be further described below with reference to the embodiments. It is worth noting that the following description is only a preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications and substitutions based on the technical solutions and inventive concepts provided by the present invention should be covered within the protection scope of the present invention.

[0035] The specific implementation steps of this invention are as follows:

[0036] (1) Preparation of polysiloxane-polyester sulfonate dispersant: 12g sodium isophthalic acid-5-sulfonate, 48g isophthalic acid, 50g diethylene glycol, and 0.12g butylstannic acid were added to a four-necked flask. Nitrogen gas was introduced, and the mixture was stirred at 200r / min. The temperature was raised to 140℃ and reacted until the solution in the flask became transparent. The temperature was then raised to 200℃ and the reaction was continued for 1.5h. 30g hydroxyl silicone oil was then added to the flask. The nitrogen gas was stopped and a vacuum pump was connected to evacuate the system. The temperature was then raised to 220℃ and the reaction was continued for 2.5h. The mixture was discharged while hot.

[0037] (2) Preparation of spherical alumina: Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 10⁻³:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 1.88-18.76% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 300-500 r / min, with the mass of sodium hydroxide being 1.6%-6.4% of the mass of aluminum nitrate nonahydrate, and stirring was continued for 20-40 min. Then, a polysiloxane-polyester sulfonate dispersant was added, with the amount of polysiloxane-polyester sulfonate dispersant being 1.0%-4.0% of the total mass of aluminum nitrate nonahydrate and ammonium sulfate, and stirring was continued for 20-40 min. Finally... Add urea, the amount of which is 160%-320% of the mass of aluminum nitrate nonahydrate, and continue stirring for 20-40 minutes to prepare a reaction solution. Under stirring at 200-600 rpm, raise the temperature to 90-120℃ at a rate of 0.8-2.0℃ / min and react for 300-900 minutes. After the reaction is complete, filter, wash 3-5 times with deionized water, then wash 3-5 times with ethanol, and dry at 85-110℃ for 20-24 hours to obtain a spherical precursor. Raise the temperature to 600-1200℃ at a rate of 5-10℃ / min, hold for 60-300 minutes, and then cool with the furnace to obtain spherical alumina.

[0038] Example 1

[0039] The preparation method of polysiloxane-polyester sulfonate dispersant is as follows: 12g of sodium isophthalic acid-5-sulfonate, 48g of isophthalic acid, 50g of diethylene glycol, and 0.12g of butylstannic acid are added to a four-necked flask. Nitrogen gas is introduced, and the mixture is stirred at 200r / min. The temperature is raised to 140℃ and reacted until the solution in the flask becomes transparent. Then, the temperature is raised to 200℃ and the reaction continues for 1.5h. Next, 30g of hydroxyl silicone oil is added to the flask, the nitrogen gas is stopped, and a vacuum pump is connected to evacuate the system. The temperature is then raised to 220℃, and the reaction is stopped after 2.5h. The product is discharged while hot.

[0040] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 10:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 1.88% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 300 r / min, with a mass of sodium hydroxide equal to 6.4% of the mass of aluminum nitrate nonahydrate, and stirring was continued for 20 min. Then, a polysiloxane-polyester sulfonate dispersant was added, with an addition amount equal to 4.0% of the total mass of aluminum nitrate nonahydrate and ammonium sulfate, and stirring was continued for another 20 min. n; Finally, add urea, the amount of which is 160% of the mass of aluminum nitrate nonahydrate, and continue stirring for 20 minutes to prepare a reaction solution; the reaction solution is stirred at 600 r / min and heated to 120℃ at a rate of 2.0℃ / min for 300 minutes. After the reaction is completed, filter, wash 5 times with deionized water, then wash 5 times with ethanol, and dry at 85℃ for 24 hours to obtain spherical precursor. The temperature is then increased to 600℃ at a rate of 5℃ / min and held for 300 minutes, and then cooled with the furnace to obtain spherical alumina.

[0041] Example 2

[0042] The preparation method of polysiloxane-polyester sulfonate dispersant is as follows: 12g of sodium isophthalic acid-5-sulfonate, 48g of isophthalic acid, 50g of diethylene glycol, and 0.12g of butylstannic acid are added to a four-necked flask. Nitrogen gas is introduced, and the mixture is stirred at 200r / min. The temperature is raised to 140℃ and reacted until the solution in the flask becomes transparent. Then, the temperature is raised to 200℃ and the reaction continues for 1.5h. Next, 30g of hydroxyl groups are added to the flask, the nitrogen gas is stopped, and a vacuum pump is connected to evacuate the system. The temperature is then raised to 220℃, and the reaction is stopped after 2.5h. The product is discharged while hot.

[0043] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 7:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 7.76% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 400 r / min, with a mass of sodium hydroxide equal to 4.8% of the mass of aluminum nitrate nonahydrate, and stirring was continued for 30 min. Then, a polysiloxane-polyester sulfonate dispersant was added, with an addition amount equal to 3.0% of the total mass of aluminum nitrate nonahydrate and ammonium sulfate, and stirring was continued for another 3 minutes. 0 min; finally, add urea, the amount of urea added is 224% of the mass of aluminum nitrate nonahydrate, and continue stirring for 30 min to prepare a reaction solution; the reaction solution is stirred at 400 r / min and heated to 110℃ at a heating rate of 1.6℃ / min for 540 min. After the reaction is completed, filter, wash 5 times with deionized water, then wash 4 times with ethanol, and dry at 90℃ for 24 h to obtain spherical precursor. Use a heating rate of 7℃ / min to reach 800℃ and hold for 180 min to obtain spherical alumina.

[0044] Example 3

[0045] The preparation method of polysiloxane-polyester sulfonate dispersant is as follows: 12g of sodium isophthalic acid-5-sulfonate, 48g of isophthalic acid, 50g of diethylene glycol, and 0.12g of butylstannic acid are added to a four-necked flask. Nitrogen gas is introduced, and the mixture is stirred at 200r / min. The temperature is raised to 140℃ and reacted until the solution in the flask becomes transparent. Then, the temperature is raised to 200℃ and the reaction continues for 1.5h. Next, 30g of hydroxyl silicone oil is added to the flask, the nitrogen gas is stopped, and a vacuum pump is connected to evacuate the system. The temperature is then raised to 220℃, and the reaction is stopped after 2.5h. The product is discharged while hot.

[0046] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 5:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 13.26% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 400 r / min, with a mass of sodium hydroxide equal to 3.2% of the mass of aluminum nitrate nonahydrate. Stirring was continued for 30 min. Then, a polysiloxane-polyester sulfonate dispersant was added, with an addition amount equal to 2.0% of the total mass of aluminum nitrate nonahydrate and ammonium sulfate. Stirring was continued for 3 minutes. 0 min; finally, add urea, the amount of urea added is 272% of the mass of aluminum nitrate nonahydrate, and continue stirring for 30 min to prepare a reaction solution; the reaction solution is stirred at 400 r / min and heated to 100℃ at a heating rate of 1.2℃ / min for 720 min. After the reaction is completed, filter, wash 5 times with deionized water, and then wash 4 times with ethanol. Dry at 100℃ for 20 h to obtain spherical precursor. Use a heating rate of 8℃ / min to reach 1000℃ and hold for 240 min to obtain spherical alumina.

[0047] Example 4

[0048] The preparation method of polysiloxane-polyester sulfonate dispersant is as follows: 12g of sodium isophthalic acid-5-sulfonate, 48g of isophthalic acid, 50g of diethylene glycol, and 0.12g of butylstannic acid are added to a four-necked flask. Nitrogen gas is introduced, and the mixture is stirred at 200r / min. The temperature is raised to 140℃ and reacted until the solution in the flask becomes transparent. Then, the temperature is raised to 200℃ and the reaction continues for 1.5h. Next, 30g of hydroxyl silicone oil is added to the flask, the nitrogen gas is stopped, and a vacuum pump is connected to evacuate the system. The temperature is then raised to 220℃, and the reaction is stopped after 2.5h. The product is discharged while hot.

[0049] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 3:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 18.76% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 500 r / min, with a mass of sodium hydroxide equal to 1.6% of the mass of aluminum nitrate nonahydrate, and stirring continued for 40 min. Then, a polysiloxane-polyester sulfonate dispersant was added, with the amount of polysiloxane-polyester sulfonate dispersant being 1.0% of the total mass of aluminum nitrate nonahydrate and ammonium sulfate, and stirring continued for another 4 min. 0 min; finally, add urea, the amount of urea added is 320% of the mass of aluminum nitrate nonahydrate, and continue stirring for 40 min to prepare a reaction solution; the reaction solution is stirred at 200 r / min and heated to 90℃ at a heating rate of 0.8℃ / min for 900 min. After the reaction is completed, filter, wash 3 times with deionized water, then wash 3 times with ethanol, and dry at 110℃ for 20 h to obtain spherical precursor. Use a heating rate of 10℃ / min to reach 1200℃ and hold for 300 min to obtain spherical alumina.

[0050] Comparative Example 1

[0051] The preparation method of Comparative Example 1 is similar to that of Step (2) in Example 1, except that no polysiloxane-polyester sulfonate dispersant is added. Other specific steps and dosages are the same as those in Step (4) of Example 1.

[0052] Comparative Example 2

[0053] The preparation method of Comparative Example 2 is similar to that of step (2) in Example 1, except that no polysiloxane-polyester sulfonate dispersant is added and no intelligent temperature control is used. The specific steps are as follows:

[0054] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 10:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 1.88% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 300 r / min, with the mass of sodium hydroxide being 6.4% of the mass of aluminum nitrate nonahydrate, and stirring was continued for 20 min. Urea was then added, with the amount of urea added being 160% of the mass of aluminum nitrate nonahydrate, and stirring was continued for 20 min to prepare a reaction solution. The reaction solution was placed in a constant temperature oil bath and heated to 120℃ with stirring at 600 r / min for 300 min. After the reaction was completed, the solution was filtered, washed 5 times with deionized water, and then washed 5 times with ethanol. The solution was dried at 85℃ for 24 h to obtain a spherical precursor. The temperature was then increased to 600℃ at a rate of 5℃ / min and held for 300 min to obtain spherical alumina.

[0055] Comparative Example 3

[0056] The preparation method of Comparative Example 3 is similar to that of step (2) in Example 1, except that the polysiloxane-polyester sulfonate dispersant is replaced with an equal amount of self-made dispersant raw material. The specific steps are as follows:

[0057] Aluminum nitrate nonahydrate and ammonium sulfate were dissolved in deionized water in a ratio of 10:1, with the total mass of aluminum nitrate nonahydrate and ammonium sulfate accounting for 1.88% of the mass of solution A. Sodium hydroxide was added at a stirring speed of 300 r / min, with a mass of sodium hydroxide equal to 6.4% of the mass of aluminum nitrate nonahydrate. Stirring was continued for 20 min. Then, sodium isophthalic acid-5-sulfonate, isophthalic acid, diethylene glycol, and hydroxyl silicone oil were added, with a mass ratio of sodium isophthalic acid-5-sulfonate:isophthalic acid:diethylene glycol:hydroxyl silicone oil of 6:12:25:15. The total amount added was 1.88% of the mass of aluminum nitrate nonahydrate. Add 4.0% of the total mass of aluminum nitrate and ammonium sulfate, and continue stirring for 20 minutes. Finally, add urea, the amount of which is 160% of the mass of aluminum nitrate nonahydrate, and continue stirring for 20 minutes to prepare a reaction solution. The reaction solution is stirred at 600 r / min and heated to 120℃ at a rate of 2.0℃ / min for 300 minutes. After the reaction is completed, filter the solution, wash it 5 times with deionized water, and then wash it 5 times with ethanol. Dry it at 85℃ for 24 hours to obtain a spherical precursor. Then, heat it at a rate of 5℃ / min to reach 600℃ and hold it for 300 minutes to obtain spherical alumina.

[0058] Blank example 1

[0059] The blank example is commercially available 1-2 micron non-spherical alumina.

[0060] Blank example 2

[0061] The blank example is commercially available spherical alumina with a diameter of 1-2 micrometers.

[0062] The products obtained from Examples 1-4, Comparative Examples 1-3, and the blank example were subjected to performance tests and characterization (Table 1 and figures). The performance test and characterization methods are as follows:

[0063] The maximum filling capacity test method is as follows: aluminum hydroxide powder is continuously added to 100 parts of 350cp vinyl silicone oil. After initial dispersion, the mixture is placed in a vacuum stirrer and degasser. The speed is set to 600r / min and the stirring time is 2min until the colloid forms a hard lump that is difficult to fill. The maximum filling capacity can be obtained from this.

[0064] Powder oil absorption value test method: Weigh 2g of powder sample and 4g of dioctyl phthalate (DOP) into a centrifuge tube, sonicate for 15 minutes to fully impregnate the powder, then place the centrifuge tube in a centrifuge, set the speed to 3000r / min, and centrifuge for 1 hour. After centrifugation, remove the centrifuge tube and invert it to allow excess DOP to flow out. Wipe away any residual DOP in the centrifuge tube, weigh the centrifuge tube, and calculate the powder oil absorption value (g / 100g).

[0065] Morphology testing method: The micromorphology of the samples was observed using a COXEM desktop scanning electron microscope.

[0066] Particle size testing method: The particle size of the samples was tested using an LS-609 laser particle size analyzer, focusing primarily on D. 50 and D 100 The changes.

[0067] Specific surface area testing method: The specific surface area of ​​the sample was tested by nitrogen adsorption method using a JW-TB200 specific surface area and pore size simultaneous analyzer.

[0068] Viscosity testing method: Fill the same amount of aluminum hydroxide powder into the same type of silicone oil, disperse it using the same process, and test the viscosity using an NDJ-8S rotational viscometer.

[0069] Table 1

[0070]

[0071] Based on particle size characterization and electron microscopy results, as the process parameters of Examples 1-4 changed, the particle size of the products in the examples increased accordingly, but there was basically no agglomeration. Comparative Example 1 controlled the decomposition of urea by intelligent temperature control, which reduced the decomposition rate of urea, but no polysiloxane-polyester sulfonate dispersant was added, so the product still had a large degree of agglomeration. Therefore, compared with Example 1, the particle size of Comparative Example 1 reached about 17 micrometers. Comparative Example 2 did not use intelligent temperature control to control the decomposition of urea, nor did it add a polysiloxane-polyester sulfonate dispersant. Therefore, the product of Comparative Example 2 had a very large degree of agglomeration, and the product particle size reached more than 30 micrometers. Comparative Example 3 did not add a polysiloxane-polyester sulfonate dispersant, but added the monomer used to prepare the polysiloxane-polyester sulfonate dispersant. The degree of agglomeration of the obtained product was reduced, but there was still a relatively large degree of agglomeration. Therefore, the product particle size reached 15 micrometers.

[0072] Characterization results of oil absorption rate, specific surface area, viscosity, and maximum filling amount show that the oil absorption rate, specific surface area, and viscosity of the products in Examples 1-4 gradually decrease, while the maximum filling amount gradually increases. Compared to Example 1, Comparative Example 1 did not add a polysiloxane-polyester sulfonate dispersant, resulting in severe agglomeration of the product. Its oil absorption rate, specific surface area, and viscosity all increased significantly, and the maximum filling amount decreased from 750 parts to 150 parts. Comparative Example 2 did not use intelligent temperature control to control urea decomposition, nor did it add a polysiloxane-polyester sulfonate dispersant. Therefore, the degree of agglomeration of the product was much greater than that of Example 1, and also slightly greater than that of Comparative Example 1. Its oil absorption rate, specific surface area, and viscosity all increased significantly, and the maximum filling amount decreased from 750 parts to 100 parts. Comparative Example 3 added monomers of a synthetic dispersant. Compared to Comparative Example 1, its degree of agglomeration was reduced, but significantly higher than that of Example 1. Its oil absorption rate, specific surface area, and viscosity all increased significantly, and the maximum filling amount decreased from 750 parts to 200 parts.

Claims

1. A method for preparing spherical alumina powder with good dispersibility, characterized in that, Includes the following steps: (1) Dissolve aluminum nitrate nonahydrate and ammonium sulfate in deionized water in proportion, and then add a certain amount of sodium hydroxide, a certain amount of polysiloxane-polyester sulfonate dispersant and a certain amount of urea in sequence under stirring to prepare a reaction solution; (2) The reaction solution is stirred at a stirring speed of 200-600 r / min and heated at a heating rate of 0.8-2.0℃ / min to a temperature of 90-120℃. The temperature is held for 300-900 min. After the reaction is completed, the solution is filtered, washed and dried to obtain spherical alumina precursor. (3) The prepared spherical alumina precursor is calcined according to a certain calcination process, and spherical alumina is obtained after cooling; The structural formula of the polysiloxane-polyester sulfonate dispersant is as follows: ； x is 25-35, y is 30-40, and z is 4-8.

2. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The mass ratio of aluminum nitrate nonahydrate to ammonium sulfate in step (1) is 10-3:

1.

3. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The mass of sodium hydroxide mentioned in step (1) is 1.6%-6.4% of the mass of aluminum nitrate nonahydrate.

4. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The amount of polysiloxane-polyester sulfonate dispersant added in step (1) is 1.0%-4.0% of the sum of the mass of aluminum nitrate nonahydrate and ammonium sulfate.

5. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The amount of urea added in step (1) is 160%-320% of the mass of aluminum nitrate nonahydrate.

6. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The stirring speed in step (1) is 300-500 r / min, the stirring time after adding sodium hydroxide is 20-40 min, the stirring time after adding polysiloxane-polyester sulfonate dispersant is 20-40 min, and the stirring time after adding urea is 20-40 min.

7. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The washing method described in step (2) is to wash with deionized water 3-5 times, and then wash with ethanol 3-5 times; the drying temperature is 85-110℃, and the drying time is 20-24h.

8. The method for preparing a well-dispersible spherical alumina powder according to claim 1, characterized in that, The calcination process described in step (3) involves heating at a rate of 5-10℃ / min to reach a calcination temperature of 600-1200℃, holding the temperature for 60-300 minutes, and then cooling down with the furnace.

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