Preparation method of flaky aluminum hydroxide

Abstract

The invention provides a preparation method of flaky aluminum hydroxide, and belongs to the field of aluminum hydroxide preparation. The method comprises the following steps: pulping and grinding a precursor raw material to obtain precursor slurry; a sodium aluminate solution is obtained; the alpha k of the sodium aluminate solution is 2.6-4.0, the alumina NT concentration of the sodium aluminate solution is 30-90 g / L, and the temperature of the sodium aluminate solution is 60-100 DEG C; adding the aluminum hydroxide precursor slurry into the sodium aluminate solution for seed decomposition to obtain mixed slurry; and carrying out solid-liquid separation, washing and drying on the mixed slurry to obtain the flaky aluminum hydroxide. By finely regulating the alpha k value, NT concentration and temperature of the sodium aluminate solution and combining the particle size and solid content optimization of the precursor slurry, the dominant growth of the crystal in the X / Y axis direction is successfully realized, and the sheet structure with high radius-thickness ratio is formed, so that a novel method for preparing the aluminum hydroxide with the sheet crystal structure with specific sheet radius and thickness is provided.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum hydroxide preparation, and in particular to a method for preparing flaky aluminum hydroxide. Background Art

[0002] As a key inorganic material, flaky aluminum hydroxide, with its unique flaky morphology, demonstrates excellent performance in a wide range of fields, including flame retardants, fillers, and catalyst supports. It can significantly improve the material's mechanical properties, barrier properties, and dispersibility. As demand for high-performance materials continues to grow across various industries, research into the preparation technology of flaky aluminum hydroxide is gaining increasing attention.

[0003] At present, common preparation methods for flaky aluminum hydroxide include hydrothermal method, precipitation method, sol-gel method, template method, mechanical exfoliation method, ionic liquid method, etc. Some hydrothermal methods use specific raw materials to prepare flaky aluminum hydroxide under high temperature conditions, but there are problems such as the need for high-pressure reaction equipment and high energy consumption; some hydrothermal products will have residual harmful ions. In the precipitation method, some processes are prone to generate amorphous impurities that affect product quality. The template materials used in the template method, such as graphene oxide and block copolymers, have the disadvantages of high cost, complex removal process and easy destruction of product morphology. The products prepared by the mechanical exfoliation method have uneven thickness and easily damaged edges. The ionic liquid method is not only expensive in terms of ionic liquid, but also has an extremely complex post-processing process. The limitations of these existing preparation methods have restricted the efficient, low-cost and high-quality production of flaky aluminum hydroxide. There is an urgent need to develop a more economical, environmentally friendly preparation method that can guarantee product performance. Summary of the Invention

[0004] The present application provides a method for preparing flaky aluminum hydroxide, so as to provide a new method for preparing flaky crystal structure aluminum hydroxide with specific flake diameter and thickness.

[0005] The present application provides a method for preparing flaky aluminum hydroxide, the method comprising:

[0006] Beating and grinding the precursor raw materials to obtain aluminum hydroxide precursor slurry;

[0007] Obtaining a sodium aluminate solution; the sodium aluminate solution is a redissolved aluminum hydroxide solution or a sintered seed solution, the αk of the sodium aluminate solution is 2.6 to 4.0, the aluminum oxide NT concentration of the sodium aluminate solution is 30 g / L to 90 g / L, and the temperature of the sodium aluminate solution is 60° C. to 100° C.;

[0008] adding an aluminum hydroxide precursor slurry to the sodium aluminate solution to perform seed decomposition to obtain a mixed slurry; and

[0009] The mixed slurry is subjected to solid-liquid separation, washing and drying to obtain flaky aluminum hydroxide.

[0010] Optionally, the precursor raw materials include: one or more of α-aluminum hydroxide trihydrate, bayerite and gibbsite.

[0011] Optionally, the particle size of the precursor raw material is 3 μm to 20 μm.

[0012] Optionally, the solid content of the aluminum hydroxide precursor slurry is 450 g / L to 500 g / L, and the grinding particle size is 1.5 μm to 4.5 μm.

[0013] Optionally, the solid content of the aluminum hydroxide precursor slurry is 460 g / L to 490 g / L, and the grinding particle size is 2 μm to 4 μm.

[0014] Optionally, the seed decomposition includes the following parameters: stirring speed of 200 rpm to 400 rpm, temperature of 60° C. to 100° C., and time of 0.5 h to 3 h.

[0015] Optionally, the seed decomposition includes the following parameters: stirring speed of 200 rpm to 400 rpm, temperature of 75° C. to 95° C., and time of 1 h to 2.5 h.

[0016] Optionally, the αk of the sodium aluminate solution is 2.8 to 3.8, and the aluminum oxide NT concentration of the sodium aluminate solution is 35 g / L to 65 g / L.

[0017] Optionally, the αk of the sodium aluminate solution is 3.0 to 3.6, and the aluminum oxide NT concentration of the sodium aluminate solution is 40 g / L to 60 g / L.

[0018] Optionally, the flaky aluminum hydroxide meets the following performance parameters: diameter-to-thickness ratio>15, specific surface area of ​​4.4m 2 / g~4.6m 2 / g, and the oil absorption rate is 27mL / 100g~33mL / 100g.

[0019] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0020] The present application discloses a method for preparing flaky aluminum hydroxide, which comprises: beating and grinding a precursor raw material to obtain an aluminum hydroxide precursor slurry; obtaining a sodium aluminate solution; the sodium aluminate solution is an aluminum hydroxide re-dissolved solution or a sintering method seed solution, the αk of the sodium aluminate solution is 2.6 to 4.0, the aluminum oxide NT concentration of the sodium aluminate solution is 30 g / L to 90 g / L, and the temperature of the sodium aluminate solution is 60°C to 100°C; adding the aluminum hydroxide precursor slurry to the sodium aluminate solution to perform seed decomposition to obtain a mixed slurry; and performing solid-liquid separation, washing, and drying the mixed slurry to obtain flaky aluminum hydroxide. By selecting the sodium aluminate solution used to decompose the flaky aluminum hydroxide as the aluminum hydroxide re-dissolved solution, or using the sintering method seed solution to prepare it, the purpose is to obtain a clean and uniform liquid reaction system, avoid the influence of impurity elements on the crystal surface development, and facilitate the uniform diffusion of the seeds in the aluminum hydroxide during the development process, thereby ensuring the synchronous precipitation of aluminum hydroxide at various points in the system. At the same time, by finely controlling the αk value, NT concentration and temperature of the sodium aluminate solution, combined with the optimization of the particle size and solid content of the precursor slurry, the dominant growth of crystals in the X / Y axis direction was successfully achieved, forming a lamellar structure with a high aspect ratio, thereby providing a new method for preparing lamellar crystal structured aluminum hydroxide with a specific flake diameter and thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0023] Figure 1 A schematic flow chart of a method for preparing flaky aluminum hydroxide provided in an embodiment of the present application;

[0024] Figure 2 This is a scanning electron microscope image of the flaky aluminum hydroxide sample provided in Example 1 of the present application;

[0025] Figure 3 This is a scanning electron microscope image of the aluminum hydroxide sample provided in Comparative Example 1 of this application;

[0026] Figure 4 This is a scanning electron microscope image of the aluminum hydroxide sample provided in Comparative Example 2 of this application;

[0027] Figure 5This is a scanning electron microscope image of the aluminum hydroxide sample provided in Comparative Example 3 of this application;

[0028] Figure 6 A scanning electron microscope image of the aluminum hydroxide sample provided in Comparative Example 5 of this application;

[0029] Figure 7 This is a scanning electron microscope image of the aluminum hydroxide sample provided in Comparative Example 6 of this application. DETAILED DESCRIPTION

[0030] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] Various embodiments of the present application may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be understood as a hard limitation on the scope of the present application; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which applies regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0032] In addition, in the description of the specification of this application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple. "Parts" such as parts by weight and parts by mass represent the proportional relationship between the components. In the proportional relationship involved in this article, the parameters that need to be described by proportion should be understood as the first term of the proportional formula in the order of description, and the proportional numbers should be understood as the second term of the proportional formula. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substance A, substance B, and substance C should correspond one-to-one to the proportional numbers in the proportional formula in the order of description, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0033] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0034] Figure 1 A schematic flow chart of a method for preparing flaky aluminum hydroxide provided in an embodiment of the present application.

[0035] like Figure 1 As shown, the present application provides a method for preparing flaky aluminum hydroxide, the method comprising:

[0036] S1. Beating and grinding the precursor raw materials to obtain aluminum hydroxide precursor slurry;

[0037] In some embodiments, the precursor raw material includes one or more of α-aluminum hydroxide trihydrate, bayerite, and gibbsite.

[0038] The precursor raw materials (α aluminum hydroxide trihydrate, bayerite, and diaspore) have a specific crystal structure, which can provide a template effect for subsequent decomposition and promote the inheritance of flake morphology.

[0039] In some embodiments, the particle size of the precursor raw material is 3 μm to 20 μm.

[0040] In some embodiments, the aluminum hydroxide precursor slurry has a solid content of 450 g / L to 500 g / L, and a grinding particle size of 1.5 μm to 4.5 μm.

[0041] In some embodiments, the aluminum hydroxide precursor slurry has a solid content of 460 g / L to 490 g / L, and a grinding particle size of 2 μm to 4 μm.

[0042] In some embodiments, the aluminum hydroxide precursor slurry has a solid content of 470 g / L to 480 g / L, and a grinding particle size of 2.5 μm to 3.5 μm.

[0043] The initial particle size of the precursor is 3-20 μm, which needs to be reduced to 1.5-4.5 μm through grinding to increase the specific surface area and provide more nucleation sites. Smaller particles (such as 2-4 μm) are beneficial for acting as seeds to uniformly induce flake growth during the decomposition process. Limiting the slurry solid content to 450-500 g / L can enhance the interaction between particles and promote the formation of a layered stacking structure. Low solid content can easily lead to excessive particle dispersion, forming irregular granular products. Illustratively, the particle size of the precursor raw material can be 3 μm, 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, etc., the solid content of the aluminum hydroxide precursor slurry can be 450 g / L, 460 g / L, 470 g / L, 480 g / L, 490 g / L, 500 g / L, etc., and the ground particle size of the precursor can be 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, etc.

[0044] S2. Obtain a sodium aluminate solution; the sodium aluminate solution is a redissolved aluminum hydroxide solution or a sintered seed solution, the αk of the sodium aluminate solution is 2.6 to 4.0, the aluminum oxide NT concentration of the sodium aluminate solution is 30 g / L to 90 g / L, and the temperature of the sodium aluminate solution is 60° C. to 100° C.;

[0045] It should be noted that the sodium aluminate solution used to decompose flaky aluminum hydroxide is a redissolved aluminum hydroxide solution, or is obtained by mixing the seed and denominator solution using the sintering method. The purpose is to obtain a clean and uniform liquid reaction system, avoid the influence of impurity elements on the development of crystal surfaces, and help reduce the uniform diffusion of crystal seeds in the development process of aluminum hydroxide, thereby ensuring the synchronous precipitation of aluminum hydroxide at various points in the system.

[0046] Choosing a sodium aluminate solution from a non-Bayer process system (such as aluminum hydroxide redissolved solution or sintering process seed liquor) may interfere with the directional growth of the flake structure due to the high organic matter content of the Bayer process solution.

[0047] In some embodiments, the αk of the sodium aluminate solution is 2.8 to 3.8, and the alumina NT concentration of the sodium aluminate solution is 35 g / L to 65 g / L.

[0048] In some embodiments, the αk of the sodium aluminate solution is 3.0 to 3.6, and the alumina NT concentration of the sodium aluminate solution is 40 g / L to 60 g / L.

[0049] It should be noted that the αk value is the caustic ratio, the Al2O3 / Na2O molar ratio, and the αk control range is 2.6 to 4.0 (optimal 3.0 to 3.6), which is a key parameter affecting the crystal morphology. When αk>2.6, the supersaturation of the solution is reduced, which inhibits the growth of aluminum hydroxide crystals in the Z axis (thickness direction), thereby promoting the formation of a two-dimensional lamellar structure. If αk is too low (such as 1.45 to 2.6), the crystals tend to grow isotropically to form a granular structure. For example, the αk of the sodium aluminate solution can be 2.6, 2.7, 2.8, 2.9, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, etc.

[0050] The NT concentration directly affects the supersaturation of the solution. A concentration that is too low (e.g., <30 g / L) results in insufficient nucleation rates and coarse particles; a concentration that is too high (>90 g / L) can trigger non-uniform nucleation, leading to agglomeration or the formation of heterogeneous crystals. The optimal range is 40 g / L to 60 g / L, which balances nucleation and growth rates and optimizes the lamellar structure. The alumina NT concentration of the sodium aluminate solution can be 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, etc.

[0051] S3, adding aluminum hydroxide precursor slurry to the sodium aluminate solution to perform seed decomposition to obtain a mixed slurry;

[0052] In some embodiments, the seed decomposition includes the following parameters: a stirring speed of 200 rpm to 400 rpm, a temperature of 60° C. to 100° C., and a time of 0.5 h to 3 h.

[0053] In some embodiments, the seed decomposition includes the following parameters: stirring speed of 200 rpm to 400 rpm, temperature of 75° C. to 95° C., and time of 1 hour to 2.5 hours.

[0054] In some embodiments, the seed decomposition includes the following parameters: stirring speed of 200 rpm to 400 rpm, temperature of 80° C. to 90° C., and time of 1.5 h to 2.0 h.

[0055] It should be noted that the temperature of the sodium aluminate solution is also the temperature of the seed decomposition. The solution temperature is 60-100°C. Increasing the temperature can increase the decomposition rate of the sodium aluminate solution, but too high a temperature (such as >100°C) may accelerate the disordered growth of the crystals and reduce the diameter-to-thickness ratio. The optimized temperature of 80-90°C can not only ensure the reaction efficiency, but also maintain the stability of the crystal lamellae morphology. The stirring speed is limited to 200rpm-400rpm to ensure uniform mixing of the solution, prevent particle sedimentation or excessive local supersaturation, and thus avoid the formation of impurity crystals. Excessive stirring speed may destroy the formed lamellae crystals. The seed decomposition time is limited to 0.5-3h. Too short a time will lead to incomplete crystal growth and smaller flake diameter; too long a time will induce secondary nucleation or crystal thickening. The optimal time (1.5-2h) can balance the flake diameter and thickness to achieve a diameter-to-thickness ratio of >15. Exemplarily, the stirring speed of the seed decomposition can be 200rpm, 220rpm, 250rpm, 300rpm, 350rpm, 380rpm, 400rpm, etc., the temperature can be 60℃, 70℃, 75℃, 80℃, 90℃, 100℃, etc., and the time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, etc.

[0056] In some embodiments, the volume ratio of the sodium aluminate solution to the aluminum hydroxide precursor slurry is (2-4):1.

[0057] S4. The mixed slurry is subjected to solid-liquid separation, washing and drying to obtain flaky aluminum hydroxide.

[0058] In some embodiments, after the seed decomposition is completed, the washing water temperature is above 70° C. during separation and washing, and the washing is completed after the pH value of the washing water reaches 7. The filter cake is dried at 80° C. for 10 hours.

[0059] Washing with a Buchner funnel can effectively remove residual sodium ions and prevent impurities from affecting the sheet structure during the subsequent drying process.

[0060] In some embodiments, the flaky aluminum hydroxide meets the following performance parameters: diameter-to-thickness ratio>15, specific surface area of ​​4.4m 2 / g~4.6m 2 / g, and the oil absorption rate is 27mL / 100g~33mL / 100g.

[0061] The embodiment of the present application achieves advantageous growth of crystals in the X / Y axis direction by precisely controlling the αk, NT concentration and temperature of the sodium aluminate solution, combined with the optimization of the particle size and solid content of the precursor slurry, to form a sheet structure with a high aspect ratio. This method does not require complex equipment or additives and is directly integrated into the existing alumina production process, significantly reducing energy consumption and costs. It is suitable for large-scale production in the fields of flame retardant materials, electronic packaging, etc. For example, the aspect ratio of the flaky aluminum hydroxide can be 16, 17, 18, 19, 20, etc., and the specific surface area can be 4.4m 2 / g, 4.45m 2 / g, 4.5m 2 / g, 4.55m 2 / g, 4.6m 2 / g, etc., the oil absorption rate can be 30mL / 100g, 30.5mL / 100g, 31mL / 100g, 31.5mL / 100g, 32mL / 100g, etc.

[0062] In summary, the method for preparing flaky aluminum hydroxide provided in the examples of this application has multiple advantages, including precise control of crystal morphology, simple process and low cost, excellent product performance, flexible raw material selection, environmental friendliness, ease of industrial production, and broad application prospects. It has opened up a new path for the preparation and application of aluminum hydroxide. Specifically, it has the following advantages:

[0063] (1) Precise control of crystal morphology: By finely controlling the αk value (caustic ratio), NT concentration (alumina concentration) and temperature of the sodium aluminate solution, combined with the optimization of the particle size and solid content of the precursor slurry, the dominant growth of crystals in the X / Y axis direction was successfully achieved, forming a lamellar structure with a high aspect ratio.

[0064] (2) Simple process and low cost: This method does not require complex equipment or additional additives and can be directly integrated into the existing alumina production process, significantly reducing energy consumption and costs.

[0065] (3) Excellent product performance: the obtained flaky aluminum hydroxide has a diameter-to-thickness ratio of >15 and a specific surface area of ​​4.4 m 2 / g~4.6m 2 / g, oil absorption rate of 27mL / 100g ~ 33mL / 100g and other excellent performance parameters, suitable for flame retardant materials, electronic packaging and other fields.

[0066] (4) Flexible raw material selection: The precursor raw materials can be selected from one or more of α-aluminum hydroxide trihydrate, Bayerite, and diaspore. These raw materials have a specific crystal structure and can provide a template effect for subsequent decomposition, promoting the inheritance of the flake morphology.

[0067] (5) Environmentally friendly: Using aluminum hydroxide re-dissolved solution or sintering method denominator solution as the source of sodium aluminate solution avoids the influence of impurity elements on crystal surface development, while reducing the emission of harmful substances and meeting environmental protection requirements.

[0068] (6) Easy to industrialize: This method is simple to operate, easy to control, and can be produced on a large scale, meeting the market's strong demand for flaky aluminum hydroxide.

[0069] (7) Broad application prospects: Since flaky aluminum hydroxide has unique physical and chemical properties, such as high thermal stability, high specific surface area and good dispersibility, it has broad application prospects in many fields such as flame retardant materials, ceramic coatings, catalyst carriers, electronic packaging materials, etc.

[0070] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are generally measured according to industry standards. If there are no corresponding industry standards, then the methods are carried out according to general international standards, conventional conditions, or the conditions recommended by the manufacturer.

[0071] Example 1

[0072] The seed solution (NT concentration of 103.95 g / L, AO of 35.33 g / L, NC of 16.1 g / L, αk of 4.09 g / L) in the process of preparing alumina by sintering was measured, and the sodium aluminate solution (NT concentration of 102.37 g / L, AO of 93.51 g / L, NC of 15.37 g / L, αk of 1.53 g / L) used to prepare alumina by sintering was used to adjust the concentration with distilled water. After adjustment, the NT concentration of the sodium aluminate solution used for seed decomposition was 52 g / L, and αk The NT concentration is 3.4, 500 mL of the adjusted solution is measured and transferred to a water bath. The temperature is controlled at 90 ° C. The stirring speed is turned on at 300 rpm. 164 ml of aluminum hydroxide precursor slurry (solid content is 485 g / l, grinding particle size is 2.5-3.5 μm) is measured and added to the adjusted liquid. Due to the addition of the slurry, the NT concentration is reduced to 50 g / l at this time, and the seed decomposition is carried out. The decomposition time is 1.5 hours. The decomposed slurry is subjected to solid-liquid separation and washing. After washing, the filter cake is dried to obtain flaky aluminum hydroxide. The scanning electron microscope image of the flaky aluminum hydroxide sample is as follows: Figure 2 shown.

[0073] Example 2

[0074] 1000 ml of ion-exchange membrane base (sodium oxide concentration is 323 g / L) was measured and transferred into an autoclave. 238 g of aluminum hydroxide was added and dissolved at 140°C for 1 hour. The solution was removed after cooling. After analysis, the solution αk was 3.4 and the NT concentration was 298 g / L.

[0075] Measure 104mL of the above solution, add 396ml of distilled water to adjust the concentration. After adjustment, the NT concentration is 52g / L, αk is 3.4, the volume is 500mL, move into a water bath to control the temperature to 90°C, open the stirring speed at 300rpm, measure 164mL of aluminum hydroxide precursor slurry (solid content is 485g / l, grinding particle size is 2.5-3.5μm) and add it to the adjusted liquid. Due to the addition of the slurry, the NT concentration is reduced to 50g / L at this time. Decompose for 1.5h, and the decomposed slurry is subjected to solid-liquid separation and washing. The washed filter cake is dried to obtain flaky aluminum hydroxide.

[0076] Comparative Example 1

[0077] This comparative example is modified as follows based on Example 1:

[0078] The steps are the same as those in Example 1. Comparative Example 1 uses a sodium aluminate concentrate or a solution obtained by re-dissolving aluminum hydroxide with liquid alkali to prepare aluminum oxide using a sintering method. The αk of the sodium aluminate solution used for seed decomposition after adjustment is 1.53, but the αk is low. The NT concentration and the ratio of precursor slurry addition, decomposition temperature, and time are the same as those in Example 1. After decomposition is completed, solid-liquid separation and washing are performed, and the filter cake is dried and sent for sample analysis. The morphology of aluminum hydroxide is granular, and no flaky aluminum hydroxide is obtained. The scanning electron microscope image of the granular aluminum hydroxide sample is as follows: Figure 3 shown.

[0079] Comparative Example 2

[0080] This comparative example is modified as follows based on Example 1:

[0081] The steps are the same as in Example 1. The NT concentration of the sodium aluminate solution used for seed decomposition is adjusted to 20 g / L. The decomposition slurry is separated and the mother liquor is washed and dried and sent for sample analysis. The flakes are not obvious. Figure 4 shown.

[0082] Comparative Example 3

[0083] This comparative example is modified as follows based on Example 1:

[0084] The steps were the same as in Example 1. The NT concentration of the sodium aluminate solution used for seed decomposition was adjusted to 100 g / L, the seed decomposition temperature was 80°C, the decomposition slurry was separated, the mother liquor was washed, dried and sent for sample analysis. No flaky aluminum hydroxide was obtained. The scanning electron microscope image of the aluminum hydroxide sample is as follows: Figure 5 shown.

[0085] Comparative Example 4

[0086] This comparative example is modified as follows based on Example 1:

[0087] The steps were the same as those in Example 1. The adjusted αk of the sodium aluminate solution used for seed decomposition was 4.2. The decomposition slurry was separated, the mother liquor was washed, dried and sent for sample analysis. No flaky aluminum hydroxide was obtained. At the same time, compared with Example 1, the output was reduced by 6%, which may be due to low supersaturation of the solution and reverse dissolution of the precursor.

[0088] Comparative Example 5

[0089] This comparative example is modified as follows based on Example 1:

[0090] The steps are the same as those in Example 1. The seed decomposition time is 20 min. The decomposition slurry is separated from the mother liquor and washed and then dried and sent for sample analysis. The flakes are not obvious. Figure 6 shown.

[0091] Comparative Example 6

[0092] This comparative example is modified as follows based on Example 1:

[0093] The steps were the same as in Example 1, with a seed decomposition time of 5 h. The decomposition slurry was separated, the mother liquor was washed, dried, and sent for sample analysis to obtain flaky aluminum hydroxide. Compared with Example 1, the flaky morphology was poor. The scanning electron microscope image of the aluminum hydroxide sample is shown in FIG. Figure 7 shown.

[0094] Comparative Example 7

[0095] This comparative example is modified as follows based on Example 1:

[0096] The steps were the same as in Example 1. The solid content of the aluminum hydroxide precursor slurry was 200 g / L, and the added volume ratio was the same. The slurry was decomposed, the mother liquor was separated, washed, dried, and sent for sample analysis. No aluminum hydroxide flake morphology was obtained.

[0097] Comparative Example 8

[0098] This comparative example is modified as follows based on Example 1:

[0099] It was planned to grind the aluminum hydroxide precursor with a solid content of 600g / l slurry. During the grinding process, it was found that the slurry was too viscous and not easy to carry out industrially, so no high solid content precursor test comparison was carried out.

[0100] The parameters of the preparation methods of flaky aluminum hydroxide in Example 1, Example 2 and Comparative Examples 1 to 8 are summarized, and the results are shown in Table 1.

[0101] Table 1 Parameters of the preparation method of flaky aluminum hydroxide of Examples and Comparative Examples

[0102]

[0103] The performance of the flaky aluminum hydroxide of Example 1, Example 2 and Comparative Examples 1 to 8 was measured, and the results are shown in Table 2.

[0104] Table 2 Properties of flaky aluminum hydroxide in Examples and Comparative Examples

[0105]

[0106] Note: Comparative Example 8 is a precursor solid content 600g / L slurry grinding. During the grinding process, it was found that the slurry was too viscous and not easy to carry out industrially, so the precursor high solid content test comparison was not carried out.

[0107] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0108] In the embodiments of the present application, the defects of the existing technology for preparing flaky aluminum hydroxide, which is difficult for large-scale industrialization due to complex processes or high costs, are overcome, and a method for preparing flaky aluminum hydroxide is provided. This preparation method can effectively control the thickness and diameter of aluminum hydroxide. Its flaky structure enables it to have better flame retardancy and density when added to polymers, and can optimize the heat conduction path by stacking when used in electronic packaging materials, etc., which is beneficial for alumina companies to upgrade their products.

[0109] In the embodiments of the present application, energy consumption is low, pollution is small, and industrialization is easy to achieve. The prepared aluminum hydroxide has a thin-sheet crystal structure and can be used in multiple industries such as flame retardant materials, ceramic coatings, and catalyst carriers.

[0110] In the embodiments of the present application, the diameter and thickness of the flaky aluminum hydroxide prepared by this method are controllable, the crystal plane is fully developed, the stacking property is good, the diameter-to-thickness ratio is greater than 15, the particle size is 1.5μm to 2.5μm, and the oil absorption rate is 27mL / 100g to 33mL / 100g. It can be applied in different fields and has excellent flame retardancy or thermal conductivity.

[0111] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A method for preparing flaky aluminum hydroxide, comprising: Beating and grinding the precursor raw materials to obtain aluminum hydroxide precursor slurry; Obtaining a sodium aluminate solution; The sodium aluminate solution is a redissolved aluminum hydroxide solution or a sintered seed solution, the αk of the sodium aluminate solution is 2.6 to 4.0, the aluminum oxide NT concentration of the sodium aluminate solution is 30 g / L to 90 g / L, and the temperature of the sodium aluminate solution is 60° C. to 100° C.; adding an aluminum hydroxide precursor slurry to the sodium aluminate solution to perform seed decomposition to obtain a mixed slurry; as well as The mixed slurry is subjected to solid-liquid separation, washing and drying to obtain flaky aluminum hydroxide.

2. The method according to claim 1, characterized in that The precursor raw materials include: one or more of α aluminum hydroxide trihydrate, bayerite and gibbsite.

3. The method according to claim 2, characterized in that The particle size of the precursor raw material is 3 μm to 20 μm.

4. The method according to claim 1, wherein The solid content of the aluminum hydroxide precursor slurry is 450 g / L to 500 g / L, and the grinding particle size is 1.5 μm to 4.5 μm.

5. The method according to claim 4, characterized in that The solid content of the aluminum hydroxide precursor slurry is 460 g / L to 490 g / L, and the grinding particle size is 2 μm to 4 μm.

6. The method according to claim 1, wherein The seed decomposition includes the following parameters: a stirring speed of 200 rpm to 400 rpm, a temperature of 60° C. to 100° C., and a time of 0.5 h to 3 h.

7. The method according to claim 6, characterized in that The seed decomposition includes the following parameters: a stirring speed of 200 rpm to 400 rpm, a temperature of 75° C. to 95° C., and a time of 1 hour to 2.5 hours.

8. The method according to claim 1, characterized in that The αk of the sodium aluminate solution is 2.8 to 3.8, and the aluminum oxide NT concentration of the sodium aluminate solution is 35 g / L to 65 g / L.

9. The method according to claim 8, characterized in that The αk of the sodium aluminate solution is 3.0 to 3.6, and the aluminum oxide NT concentration of the sodium aluminate solution is 40 g / L to 60 g / L.

10. The method according to claim 1, characterized in that The flaky aluminum hydroxide meets the following performance parameters: diameter-to-thickness ratio>15, specific surface area of ​​4.4m 2 / g~4.6m 2 / g, particle size is 1.5μm~2.5μm, and oil absorption rate is 27mL / 100g~33mL / 100g.

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