A method for preparing spherical boehmite

Abstract

The application discloses a preparation method of spherical boehmite and relates to the technical field of inorganic materials. The spherical boehmite prepared by the method has high sphericity and can be used as a reinforcing agent to fill materials such as potting adhesive, paint, rubber, plastic, electronic substrate and battery diaphragm. Compared with boehmite directly obtained by hydrothermal reaction of aluminum hydroxide, the spherical boehmite prepared by the method has a smaller specific surface area and a smaller influence on the viscosity of a polymer system, so that a higher filling amount can be realized, and the spherical boehmite can also be used as a flame retardant to effectively improve the flame retardant performance of the polymer system.

Description

Technical fields:

[0001] This invention relates to the field of inorganic materials technology, specifically to a method for preparing spherical boehmite. Background technology:

[0002] Boehmite (AlOOH), also known as boehmite monohydrate, is a white solid powder that is insoluble in water and sparingly soluble in acids and alkalis. It has a wide range of applications. Boehmite can be used as a flame retardant in industries such as electronic substrates, potting compounds, coatings, rubber, lithium battery separators, and plastic fillers, making it an important chemical raw material. Due to the unique properties of inorganic materials with specific morphologies, boehmite with specific forms has become a research hotspot in materials science, especially those in sheet-like, spherical, needle-like, flower-like, and cubic forms.

[0003] Patent CN202211037285.7 discloses a method for preparing thermally conductive boehmite. Using pure aluminum powder, alcohol-water mixture, template agents (one or more of ethylenediamine, n-ethylamine, triethylamine, P123, F127, and polystyrene emulsion), and pH adjusters (one or more of nitric acid, citric acid, glacial acetic acid, uric acid, ammonia, oxalic acid, lactic acid, and ammonium carbonate) as raw materials, the method yields spherical, near-spherical, and near-ellipsoidal boehmite through hydrolysis and two hydrothermal crystallization treatments. This preparation method suffers from drawbacks such as complex processes, high costs, and the generation of environmentally unfriendly organic byproducts. Furthermore, the provided drawings show that the sphericity of the boehmite is not high. Summary of the Invention:

[0004] The technical problem to be solved by the present invention is to provide a method for preparing spherical boehmite, specifically, aluminum salt is first precipitated to obtain nano-aluminum hydroxide, then spherical aluminum hydroxide is obtained by spray granulation, and finally spherical boehmite with a sphericity greater than 90% is obtained by hydrothermal treatment.

[0005] The technical problem to be solved by this invention is achieved by the following technical solution:

[0006] One objective of this invention is to provide a method for preparing spherical boehmite, comprising the following steps:

[0007] (1) Dissolve inorganic aluminum salts in water to obtain an aluminum salt solution;

[0008] (2) Adjust the pH of the aluminum salt solution to 8-12 by adding alkali to obtain nano-aluminum hydroxide slurry with a particle size of less than 300nm;

[0009] (3) Ion cleaning of nano-aluminum hydroxide slurry;

[0010] (4) Spray granulation of the cleaned nano aluminum hydroxide slurry to obtain spherical aluminum hydroxide;

[0011] (5) Disperse spherical aluminum hydroxide in water and then transfer it to a hydrothermal reactor for hydrothermal reaction to obtain spherical boehmite.

[0012] Preferably, the inorganic aluminum salt is selected from any one of water-soluble inorganic aluminum salts such as aluminum nitrate, aluminum sulfate, and aluminum chloride, and more preferably aluminum nitrate.

[0013] Preferably, the alkali is selected from any one of inorganic or organic alkalis such as sodium hydroxide, ammonia, and ethylenediamine, and more preferably ammonia. The amount of alkali used is determined to adjust the pH of the aluminum salt solution to 8-12.

[0014] Preferably, the ion cleaning is performed until the EC value is less than 50 μS / cm.

[0015] Preferably, the sphericity of the spherical aluminum hydroxide is greater than 85%.

[0016] Preferably, the hydrothermal reaction is carried out at a temperature of 150–200°C for 2–20 hours.

[0017] The second objective of this invention is to provide a spherical boehmite obtained by the above-described preparation method.

[0018] Preferably, the sphericity of the spherical boehmite is greater than 90%.

[0019] This invention uses aluminum salt as the aluminum source and alkali as the precipitant to prepare highly active nano-aluminum hydroxide. The highly active nano-aluminum hydroxide can be granulated into spherical aluminum hydroxide by spray granulation technology. Then, the spherical aluminum hydroxide can be subjected to hydrothermal reaction at a certain temperature to obtain boehmite, and the obtained boehmite inherits the morphology of the spherical aluminum hydroxide.

[0020] The beneficial effects of this invention are: the spherical boehmite obtained by the preparation method provided by this invention has high sphericity and can be used as a reinforcing agent to fill materials such as potting compounds, coatings, rubber, plastics, electronic substrates, and battery separators; compared with boehmite obtained directly by hydrothermal reaction of aluminum hydroxide, at the same addition amount, the spherical boehmite prepared by this invention has a smaller specific surface area and has less impact on the viscosity of the polymer system, thus achieving a higher filling amount. It can also be used as a flame retardant to effectively improve the flame retardant properties of the polymer system. Attached image description:

[0021] Figure 1 SEM image of the spherical aluminum hydroxide prepared in Example 1;

[0022] Figure 2 SEM image of the spherical boehmite prepared in Example 1;

[0023] Figure 3XRD pattern of spherical boehmite prepared in Example 1;

[0024] Figure 4 SEM image of the spherical boehmite prepared in Example 2;

[0025] Figure 5 SEM image of the spherical boehmite prepared in Example 3;

[0026] Figure 6 SEM image of the spherical boehmite prepared in Example 4;

[0027] Figure 7 SEM image of the spherical boehmite prepared in Example 5;

[0028] Figure 8 SEM image of boehmite prepared in Comparative Example 1;

[0029] Figure 9 Here is a SEM image of the aluminum hydroxide obtained by spray granulation in Comparative Example 2;

[0030] Figure 10 For comparison, here is the SEM image of the aluminum hydroxide raw material in Example 3;

[0031] Figure 11 SEM image of boehmite prepared in Comparative Example 3;

[0032] Figure 12 For comparison, see the SEM image of the aluminum hydroxide raw material in Example 4;

[0033] Figure 13 SEM image of boehmite prepared in Comparative Example 4. Detailed implementation method:

[0034] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0035] Example 1

[0036] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After addition, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The aluminum hydroxide slurry was ion-cleaned until the EC was less than 50µs / cm, followed by spray granulation (feed frequency 10Hz, atomizer frequency 150Hz) to obtain spherical aluminum hydroxide. 40g of the spherical aluminum hydroxide and 360g of water were placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 20 hours. After filtration and drying, spherical boehmite (e.g., ...) was obtained. Figure 3 As shown in the figure, the sphericity is 92%.

[0037] from Figure 1 and Figure 2 It can be seen that boehmite, the product obtained from the hydrothermal reaction, inherits the spherical morphology of spherical aluminum hydroxide.

[0038] from Figure 3 It can be seen that spherical aluminum hydroxide is completely converted into boehmite through hydrothermal reaction.

[0039] Example 2

[0040] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After addition, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The slurry was ion-cleaned until the EC was less than 50µs / cm, followed by spray granulation (feed frequency 10Hz, atomizer frequency 150Hz) to obtain spherical aluminum hydroxide. 40g of the spherical aluminum hydroxide and 360g of water were placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 2 hours. After filtration and drying, spherical boehmite (e.g., ...) was obtained. Figure 4 As shown in the figure, the sphericity is 91%.

[0041] Example 3

[0042] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After addition, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The aluminum hydroxide slurry was ion-cleaned until the EC was less than 50us / cm, followed by spray granulation (feed frequency 10Hz, atomizer frequency 150Hz) to obtain spherical aluminum hydroxide. 40g of the spherical aluminum hydroxide and 360g of water were placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 5 hours. After filtration and drying, spherical boehmite (e.g., ...) was obtained. Figure 5 As shown in the figure, the sphericity is 91%.

[0043] Example 4

[0044] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After addition, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The slurry was ion-cleaned until the EC was less than 50µs / cm, followed by spray granulation (feed frequency 10Hz, atomizer frequency 150Hz) to obtain spherical aluminum hydroxide. 40g of the spherical aluminum hydroxide and 360g of water were placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 10 hours. After filtration and drying, spherical boehmite (e.g., ...) was obtained. Figure 6 As shown in the figure, the sphericity is 93%.

[0045] Example 5

[0046] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After addition, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The aluminum hydroxide slurry was ion-cleaned until the EC was less than 50µs / cm, followed by spray granulation (feed frequency 10Hz, atomizer frequency 150Hz) to obtain spherical aluminum hydroxide. 40g of the spherical aluminum hydroxide and 360g of water were placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 15 hours. After filtration and drying, spherical boehmite (e.g., ...) was obtained. Figure 7 As shown in the figure, the sphericity is 90%.

[0047] Compare with Example 1

[0048] 3750g of aluminum nitrate nonahydrate was dissolved in 10kg of water to obtain an aluminum nitrate solution. This solution was then added dropwise to 2700g of 25wt% ammonia water at a rate of 100mL / min. After the addition was complete, the mixture was stirred for 1 hour to obtain a nano-aluminum hydroxide slurry with a particle size D50 = 294nm. The aluminum hydroxide slurry was ion-cleaned until the EC was less than 50µs / cm. 400g of the cleaned aluminum hydroxide slurry was placed in a 500mL high-temperature, high-pressure reactor and hydrothermally reacted at 200℃ for 20 hours. After filtration and drying, amorphous boehmite (e.g., ...) was obtained. Figure 8 (As shown).

[0049] Compare with Example 2

[0050] 1000g of aluminum hydroxide with a particle size D50 = 0.5µm was mixed with 9kg of water to prepare an aluminum hydroxide slurry with a solid content of 10%. The slurry was then subjected to spray granulation (feed frequency 10Hz, atomizer frequency 150Hz), but spherical aluminum hydroxide (e.g.) was not obtained. Figure 9 (As shown).

[0051] Compare with Example 3

[0052] Take 40g of aluminum hydroxide with a particle size D50 = 1µm (e.g. Figure 10 As shown), add 360g of water to prepare an aluminum hydroxide slurry with a solid content of 10%. Then, the aluminum hydroxide slurry is loaded into a 500mL high-temperature and high-pressure reactor and hydrothermally reacted at 200℃ for 20 hours. After filtration and drying, irregular boehmite (as shown) is obtained. Figure 11 (As shown).

[0053] Compare with Example 4

[0054] Take 40g of aluminum hydroxide microspheres prepared by patent CN115490253A (e.g.) Figure 12 As shown), add 360g of water to prepare an aluminum hydroxide slurry with a solid content of 10%. Then, the aluminum hydroxide slurry is loaded into a 500mL high-temperature and high-pressure reactor and hydrothermally reacted at 200℃ for 20 hours. After filtration and drying, irregular boehmite (as shown) is obtained. Figure 13 (As shown).

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing spherical boehmite, characterized in that, Includes the following steps: (1) Dissolve the inorganic aluminum salt in water to obtain an aluminum salt solution; (2) Adjust the pH of the aluminum salt solution to 8-12 by adding alkali to obtain nano-aluminum hydroxide slurry with a particle size of less than 300nm; (3) Ion cleaning of nano-aluminum hydroxide slurry; (4) Spray granulation is performed on the cleaned nano aluminum hydroxide slurry to obtain spherical aluminum hydroxide; (5) Disperse spherical aluminum hydroxide in water, and then transfer it to a hydrothermal reactor for hydrothermal reaction to obtain spherical boehmite; The hydrothermal reaction is carried out at a temperature of 150~200℃ for a time of 2~20 h.

2. The preparation method according to claim 1, characterized in that: The inorganic aluminum salt is selected from any one of aluminum nitrate, aluminum sulfate, and aluminum chloride.

3. The preparation method according to claim 2, characterized in that: The inorganic aluminum salt is aluminum nitrate.

4. The preparation method according to claim 1, characterized in that: The alkali is selected from any one of sodium hydroxide, ammonia, and ethylenediamine.

5. The preparation method according to claim 4, characterized in that: The alkali is ammonia.

6. The preparation method according to claim 1, characterized in that: The ion cleaning is performed until the EC value is less than 50 us / cm.

7. The preparation method according to claim 1, characterized in that: The sphericity of the spherical aluminum hydroxide is greater than 85%.

8. Spherical boehmite obtained by the preparation method according to any one of claims 1-7.

9. The spherical boehmite according to claim 8, characterized in that: The sphericity of the spherical boehmite is greater than 90%.

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