Superfine aluminum hydroxide seed crystal, superfine aluminum hydroxide product and preparation method of superfine aluminum hydroxide seed crystal

Abstract

The invention relates to the technical field of fine aluminum oxide preparation, in particular to a superfine aluminum hydroxide seed crystal, a superfine aluminum hydroxide product and a preparation method of the superfine aluminum hydroxide seed crystal. The preparation method comprises the following steps: carrying out carbonation decomposition reaction on carbon dioxide gas and a first sodium aluminate solution to obtain a superfine aluminum hydroxide seed crystal inducer; wherein the superfine aluminum hydroxide seed crystal inducer comprises a gelatinous material, and the mass of the gelatinous material is greater than or equal to 90% of that of the superfine aluminum hydroxide seed crystal inducer; performing seed crystal decomposition reaction on the superfine aluminum hydroxide seed crystal inducer and a second sodium aluminate solution to obtain superfine aluminum hydroxide seed crystals; wherein the temperature of the seed crystal decomposition reaction is less than or equal to 60 DEG C. According to the preparation method, through triple synergy of gel dissolution, low-temperature growth and defect fixation, the product simultaneously has the characteristics of nano-scale particle size distribution, high-activity specific surface area and low residual alkali content.

Description

Technical Field

[0001] The present application relates to the technical field of fine alumina preparation, and in particular to an ultrafine aluminum hydroxide seed, an ultrafine aluminum hydroxide product and a preparation method thereof. Background Art

[0002] Ultrafine aluminum hydroxide is a white solid powder with small particle size, large specific surface area and good thermal stability. It is mainly used in the fields of flame retardant for wires and cables, flame retardant for silicone rubber and coatings. It is also the raw material for preparing fine alumina. There are many methods for preparing ultrafine aluminum hydroxide. According to the principle of preparation, these methods are divided into mechanical grinding method and seed separation method. Among them, the mechanical grinding method has the advantages of simple method and low production cost, but the particle size distribution of aluminum hydroxide obtained by mechanical grinding is uneven, and it also contains large particles, which leads to poor performance of these aluminum hydroxides; however, the particle size and distribution of aluminum hydroxide prepared by the seed separation method can be controlled, and the performance of these aluminum hydroxides is better. It is the main preparation method of ultrafine aluminum hydroxide at present.

[0003] The current technologies for preparing ultrafine aluminum hydroxide based on the seed separation method include: (1) A method for preparing ultrafine aluminum hydroxide. This method uses a mixture of high-concentration sodium aluminate and water for crystallization to obtain ultrafine aluminum hydroxide seeds. This method takes 12 hours to 40 hours, and the average particle size of the final ultrafine aluminum hydroxide seed product is 1μm to 2μm. (2) Another method for preparing ultrafine aluminum hydroxide, in which a dispersant is introduced during the decomposition process of high-concentration sodium aluminate and the mass ratio of the dispersant to the mass of sodium aluminate is controlled to be 2:100. The average particle size of the final ultrafine aluminum hydroxide seed product is 0.8μm to 2μm. (3) Ultrafine aluminum hydroxide seeds and their preparation methods, submicron aluminum hydroxide and their preparation methods. The preparation method is to mix alumina hydrate with an aluminate solution, and then decompose the mixed solution to prepare ultrafine aluminum hydroxide seeds, and then mix the ultrafine aluminum hydroxide seeds with an aluminate refined solution at a seed coefficient of 10% to 80% to obtain mixed seeds; the mixed seeds are decomposed to obtain submicron aluminum hydroxide, and the average particle size of the final aluminum hydroxide product is 0.5μm to 0.8μm. (4) Method for preparing high-purity ultrafine aluminum hydroxide flame retardant by decomposition. The method is to carbonate and decompose the sodium aluminate refined solution obtained by the Bayer process or the sintering process in a carbon separation tank to form a gel-like aluminum hydroxide gel slurry; the obtained gel-like aluminum hydroxide gel slurry is used as a seed, so that the average particle size of the final ultrafine aluminum hydroxide product is 1μm to 2μm.

[0004] However, the average particle size of the ultrafine aluminum hydroxide seeds produced by the above seed separation method is greater than 0.5 μm, and some ultrafine aluminum hydroxide products also contain large particles, which makes ultrafine aluminum hydroxide products difficult to use in some specific fields. However, if ultrafine aluminum hydroxide seeds with smaller particle sizes are used, their activity is poor. Summary of the Invention

[0005] The present application provides an ultrafine aluminum hydroxide seed crystal, an ultrafine aluminum hydroxide product and a preparation method thereof to solve the following technical problem: how to balance the average particle size and activity of the ultrafine aluminum hydroxide seed crystal.

[0006] In a first aspect, the present invention provides a method for preparing ultrafine aluminum hydroxide seed crystals, the method comprising:

[0007] Carrying out a carbonation decomposition reaction between carbon dioxide gas and the first sodium aluminate solution to obtain an ultrafine aluminum hydroxide crystal seed inducer; wherein the ultrafine aluminum hydroxide crystal seed inducer comprises a gel-like material, and the mass of the gel-like material is greater than or equal to 90% of the ultrafine aluminum hydroxide crystal seed inducer;

[0008] The ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution are subjected to a seed decomposition reaction to obtain ultrafine aluminum hydroxide seed crystals; wherein the temperature of the seed decomposition reaction is ≤60°C.

[0009] Optionally, the temperature of the carbonation decomposition reaction is 15° C. to 30° C., the time of the carbonation decomposition reaction is 1 min to 20 min, and the endpoint pH of the carbonation decomposition reaction is 8.0 to 8.5; and / or

[0010] The temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.5 h to 3.5 h.

[0011] Optionally, the carbon dioxide gas flow rate is 1.5m 3 / h~5.0m 3 / h.

[0012] Optionally, the mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(25-50):100.

[0013] Optionally, the caustic ratio of the first sodium aluminate solution is 1.30 to 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 15 g / L to 45 g / L; and / or

[0014] The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

[0015] In a second aspect, an embodiment of the present application provides an ultrafine aluminum hydroxide seed crystal, which is prepared by the preparation method described in the first aspect.

[0016] In a third aspect, the present invention provides a method for preparing an ultrafine aluminum hydroxide product, the method comprising:

[0017] The ultrafine aluminum hydroxide seed crystals prepared by the preparation method described in the first aspect and the sodium aluminate solution raw material are subjected to an induced decomposition reaction to obtain an ultrafine aluminum hydroxide product; wherein the caustic ratio of the sodium aluminate solution raw material is 1.40 to 1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L to 150 g / L.

[0018] Optionally, the temperature of the induced decomposition reaction is 55° C. to 65° C., and the time of the induced decomposition reaction is 6 h to 7 h.

[0019] Optionally, the mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(2-5):100.

[0020] In a fourth aspect, an embodiment of the present application provides an ultrafine aluminum hydroxide product, which is prepared by the preparation method described in the third aspect.

[0021] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0022] The present application provides a method for preparing ultrafine aluminum hydroxide seed crystals. The method uses a carbonation decomposition reaction to prepare an ultrafine aluminum hydroxide seed crystal inducer containing a large amount of gelatinous material. Since the gelatinous material is easily soluble in the sodium aluminate solution and produces a large amount of hydroxyl groups, there is a strong interaction between these hydroxyl groups and aluminate ions, which can inhibit the directional growth of aluminum hydroxide crystals and promote homogeneous nucleation rather than heterogeneous growth of the second sodium aluminate solution. This rapidly reduces the caustic ratio of the sodium aluminate solution, increases the seed decomposition reaction rate of the second sodium aluminate solution, and produces a large number of crystal nuclei. In addition, the gelatinous material has a high specific surface area and abundant active sites, which can significantly increase the nucleation density of the second sodium aluminate solution during the seed decomposition stage. In addition, the gel-like material can serve as a template to limit the diffusion space of newly formed aluminum hydroxide. Under the action of the seed decomposition reaction temperature of 60°C and below, the faster crystal nucleus growth rate and the higher nucleation density, the gel-like material can make the aluminum hydroxide crystals slowly grow in the nanoscale range, and form aluminum hydroxide seeds with finer particle size and incomplete development, thereby ultimately obtaining aluminum hydroxide seeds with higher activity and finer particle size. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following is a brief introduction to 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.

[0025] Figure 1 A schematic flow chart of a method for preparing ultrafine aluminum hydroxide seed crystals provided in an embodiment of the present application;

[0026] Figure 2 A schematic flow chart of a method for preparing an ultrafine aluminum hydroxide product provided in an embodiment of the present application. DETAILED DESCRIPTION

[0027] 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.

[0028] 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 rigid 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 numerical values ​​within the range; for example, the range description 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 apply regardless of the range; in addition, whenever a numerical range is indicated in this document, it is meant to include any cited number (fractional or integer) within the indicated range.

[0029] As used herein, the terms "including," "comprising," and the like mean "including but not limited to." Relational terms such as "first" and "second" are used solely to distinguish one entity or operation from another, and do not necessarily require or imply any actual relationship or order between these entities or operations. "And / or" describes the association relationship between associated objects, indicating that three relationships can exist. For example, "A and / or B" can mean: A exists alone, A and B exist at the same time, and B exists alone; where A and B can be singular or plural. "At least one" means one or more, "plurality" means two or more; "at least one," "at least one of the following," or similar expressions, refers 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 mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can each be single or plural. "Parts" notation, such as parts by weight and parts by mass, indicates the proportional relationship between components. In this article, the parameters described by ratio should be understood as the first term of the proportional formula, in the order in which they are described, and the proportional figures should be understood as the second term. For example, if the mass ratio of substances A, B, and C is 1:2:3, then substances A, B, and C should correspond to the proportional figures in the proportional formula in the order in which they are described, that is, the mass of substance A: the mass of substance B: the mass of substance C = 1:2:3.

[0030] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this article can be purchased from the market or prepared by existing methods.

[0031] Figure 1 The following is a schematic flow chart of a method for preparing ultrafine aluminum hydroxide seed crystals provided in an embodiment of the present application;

[0032] like Figure 1 As shown, the present embodiment provides a method for preparing ultrafine aluminum hydroxide seed crystals, the preparation method comprising:

[0033] S1. The carbon dioxide gas and the first sodium aluminate solution are subjected to a carbonation decomposition reaction to obtain an ultrafine aluminum hydroxide seed crystal inducer; wherein the ultrafine aluminum hydroxide seed crystal inducer comprises a gel-like material, the mass of the gel-like material being greater than or equal to 90% of the ultrafine aluminum hydroxide seed crystal inducer;

[0034] S2. The ultrafine aluminum hydroxide seed crystal inducer is subjected to a seed decomposition reaction with a second sodium aluminate solution to obtain ultrafine aluminum hydroxide seed crystals; wherein the temperature of the seed decomposition reaction is ≤60°C.

[0035] It should be noted that during the carbonation decomposition reaction stage, the carbon dioxide gas and the first sodium aluminate solution can control the amount of carbon dioxide gas introduced, the caustic ratio of the first sodium aluminate solution, and the carbonation decomposition reaction parameters, so that the mass proportion of the gel-like material of the ultrafine aluminum hydroxide seed inducer is above 90%.

[0036] It should be noted that the carbonation decomposition reaction can be carried out in a carbon fractionation tower, and the seed crystal decomposition reaction can be carried out in a decomposition tank.

[0037] It should be noted that the embodiment of the present application provides a method for preparing ultrafine aluminum hydroxide seed crystals, which prepares ultrafine aluminum hydroxide seed crystals with fine particle size and high activity through the following multi-stage action mechanism.

[0038] 1. Hydroxyl-mediated regulation of nucleation dynamics:

[0039] The gel-like material of ultrafine aluminum hydroxide inducer dissolves to produce free hydroxyl groups, which react with [Al(OH)4] - Formation of [Al(OH)5] 2- A transition state complex can reduce the activation energy of nucleation.

[0040] The dissolution of the gel-like material of the ultrafine aluminum hydroxide inducer will produce a hydroxyl network. These hydroxyl networks form a solvation layer around the aluminate through hydrogen bonding, which can increase the local supersaturation of the aluminate, greatly increase the nucleation rate of the ultrafine aluminum hydroxide seeds, and at the same time induce the ultrafine aluminum hydroxide seeds to undergo incomplete development, thereby improving the activity of the ultrafine aluminum hydroxide seeds.

[0041] 2. Limited growth mechanism under low temperature conditions:

[0042] The seed decomposition reaction temperature of 60°C will reduce the growth rate constant of ultrafine aluminum hydroxide crystals, inhibit the normal growth of ultrafine aluminum hydroxide crystals, and promote the incomplete development of ultrafine aluminum hydroxide crystals.

[0043] The gel network of the gel-like material will have a large number of nano-scale mesoporous structures. These mesoporous structures will have a steric effect, forcing the ultrafine aluminum hydroxide crystals to grow preferentially along the crystal plane, forming a sheet structure with a thickness at the nanometer level, hindering the normal growth of the ultrafine aluminum hydroxide crystals.

[0044] 3. High activity induced by defect engineering:

[0045] The rapid nucleation reaction rate will lead to incomplete development of ultrafine aluminum hydroxide crystals, resulting in edge dislocations and surface dangling bonds, which will affect the normal development of ultrafine aluminum hydroxide crystals.

[0046] Residual Na in the aluminum hydroxide lattice + Cationic vacancies will be formed, and these cation vacancies will increase the surface energy of aluminum hydroxide crystals.

[0047] In summary, the embodiments of the present application provide a method for preparing ultrafine aluminum hydroxide seeds. Through the triple synergy of gel dissolution-low temperature growth-defect fixation, the product has the following characteristics: nano-scale particle size distribution, high active specific surface area and low residual alkali content.

[0048] In some optional embodiments, the temperature of the carbonation decomposition reaction is 15° C. to 30° C., the time of the carbonation decomposition reaction is 1 min to 20 min, and the endpoint pH of the carbonation decomposition reaction is 8.0 to 8.5; and / or

[0049] The temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.5 h to 3.5 h.

[0050] In these embodiments, the carbonation decomposition reaction temperature of 15°C to 30°C, the carbonation decomposition reaction time of 1min to 20min, and the endpoint pH of the carbonation decomposition reaction of 8.0 to 8.5, controlling the specific reaction temperature, time, and endpoint pH of the carbonation decomposition reaction can allow carbon dioxide and the first sodium aluminate solution to fully decompose, prompting the first sodium aluminate solution to be converted into a gel-like material with fine and uniform particles, and these gel-like materials are not easy to agglomerate, which is conducive to the seed decomposition reaction in which the ultrafine aluminum hydroxide seed inducer participates. In addition, the seed decomposition reaction temperature of 40°C to 60°C and the seed decomposition reaction time of 2.5h to 3.5h allow the supersaturation of the second sodium aluminate solution to increase rapidly in a very short time, accelerate the decomposition of the second sodium aluminate solution, and increase the number of ultrafine aluminum hydroxide crystal nuclei, prompting the second sodium aluminate solution to form ultrafine aluminum hydroxide seed crystals with fine and uniform particle size.

[0051] It should be noted that, when the temperature of the seed decomposition reaction is less than 40°C, the excessively low temperature of the seed decomposition reaction will increase the viscosity of the second sodium aluminate solution, and the second sodium aluminate solution with a larger viscosity will prevent the ultrafine aluminum hydroxide seed inducer from being quickly and completely dissolved in the second sodium aluminate solution, and the second sodium aluminate solution will not be able to explosively produce a large number of aluminum hydroxide nuclei; when the temperature of the seed decomposition reaction is greater than 60°C, the ultrafine aluminum hydroxide seed inducer will dissolve rapidly, but at this time the saturation degree of the second sodium aluminate solution is too low, which makes the decomposition rate of the second sodium aluminate solution slower, resulting in a smaller number of aluminum hydroxide nuclei generated by the second sodium aluminate solution, and ultimately leads to a larger particle size of the ultrafine aluminum hydroxide crystals.

[0052] The temperature of the carbonation decomposition reaction can be 15°C, 16°C, 17°C, 18°C, 19°C, 20°C, 25°C or 30°C.

[0053] The carbonation decomposition reaction time can be 1 min, 2 min, 3 min, 4 min, 5 min, 10 min, 15 min or 20 min.

[0054] The endpoint pH of the carbonation decomposition reaction may be 8.0, 8.1, 8.2, 8.3, 8.4 or 8.5.

[0055] The temperature of the seed decomposition reaction can be 40°C, 41°C, 42°C, 43°C, 44°C, 45°C, 50°C, 55°C or 60°C.

[0056] The time for decomposing the seed crystals can be 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h, 3.0 h, 3.1 h, 3.2 h, 3.3 h, 3.4 h or 3.5 h.

[0057] In some optional embodiments, the flow rate of the carbon dioxide gas is 1.5m 3 / h~5.0m 3 / h.

[0058] In these embodiments, 1.5m 3 / h~5.0m 3 The carbon dioxide gas introduction flow rate of 1000 / h can allow the carbon dioxide to quickly enter the first sodium aluminate solution to undergo carbonation decomposition reaction, thereby prompting the first sodium aluminate solution to quickly generate a large amount of ultrafine aluminum hydroxide seed crystals of gel-like material.

[0059] It should be noted that when the flow rate of carbon dioxide gas is less than 1.5m 3 / h, the carbonation decomposition reaction at a lower temperature will cause the first sodium aluminate solution to form a small amount of gel-like material, and the particle size of these gel-like materials is relatively coarse; when the amount of carbon dioxide gas introduced is greater than 5.0m 3 / h, the carbonation decomposition reaction at a relatively low temperature will cause the tiny grains in the first sodium aluminate solution to grow rapidly, thereby causing the gel-like material formed by the first sodium aluminate solution to fully develop and form, thereby obtaining a gel-like material with low activity, which is not conducive to the subsequent seed crystal decomposition reaction.

[0060] The carbon dioxide gas flow rate can be 1.5m 3 / h, 2.0m 3 / h、2.5m 3 / h、3.0m 3 / h、3.5m 3 / h、4.0m 3 / h、4.5m 3 / h or 5.0m 3 / h.

[0061] In some optional embodiments, the mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(25-50):100.

[0062] In these embodiments, the mass ratio of the ultrafine aluminum hydroxide seed crystal inducer to the aluminum oxide of the second sodium aluminate solution is (25-50):100, so that the ultrafine aluminum hydroxide seed crystal inducer can be quickly dissolved in the second sodium aluminate solution, so that the second sodium aluminate solution instantly bursts out a large number of ultrafine aluminum hydroxide crystal nuclei, which facilitates the subsequent acquisition of ultrafine aluminum hydroxide crystals with fine particle size.

[0063] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer can be 25, 30, 35, 40, 45 or 50.

[0064] In some optional embodiments, the caustic ratio of the first sodium aluminate solution is 1.30 to 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 15 g / L to 45 g / L; and / or

[0065] The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

[0066] In these embodiments, a first sodium aluminate solution with a caustic ratio of 1.30 to 1.60 exhibits excellent decomposition kinetics and stability. In the presence of carbon dioxide gas, the crystal nuclei of the first sodium aluminate solution can rapidly grow to produce an ultrafine aluminum hydroxide seed inducer with a relatively fine particle size and high activity. Alumina in the first sodium aluminate solution with a mass concentration of 15 g / L to 45 g / L can impart good fluidity to the first sodium aluminate solution, prompting the first sodium aluminate solution to undergo a carbonation decomposition reaction at an appropriate reaction rate, ultimately yielding an ultrafine aluminum hydroxide inducer with an appropriate pH and uniform dispersion. Furthermore, the crystal nuclei of the second sodium aluminate solution with a caustic ratio of 1.40 to 1.60 can rapidly grow to produce an ultrafine aluminum hydroxide seed product with a relatively fine particle size and high activity. The aluminum oxide in the second sodium aluminate solution with a mass concentration of 100 g / L to 150 g / L can make the second sodium aluminate solution have good fluidity, promote the second sodium aluminate solution to perform a seed decomposition reaction at an appropriate reaction rate, and ultimately obtain an ultrafine aluminum hydroxide seed product with suitable pH and uniform dispersion.

[0067] The caustic ratio of the first sodium aluminate solution may be 1.30, 1.35, 1.40, 1.45, 1.50, 1.55, or 1.60.

[0068] The mass concentration of aluminum oxide in the first sodium aluminate solution can be 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L or 45 g / L.

[0069] The caustic ratio of the second sodium aluminate solution may be 1.40, 1.45, 1.50, 1.55 or 1.60.

[0070] The mass concentration of aluminum oxide in the second sodium aluminate solution can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0071] It should be noted that, when the caustic ratio of the first sodium aluminate solution is less than 1.30, the viscosity of the first sodium aluminate solution is poor, which makes the stability of the first sodium aluminate solution poor and the carbonation decomposition reaction process difficult to control; when the caustic ratio of the first sodium aluminate solution is greater than 1.60, the decomposition motive force of the first sodium aluminate solution is small, which makes the decomposition rate of the first sodium aluminate solution too slow and the crystal nucleus growth rate too fast, which results in the produced ultrafine aluminum hydroxide inducer having a coarse particle size and poor activity, which is not conducive to the subsequent seed crystal decomposition reaction.

[0072] It should be noted that, when the mass concentration of aluminum oxide in the first sodium aluminate solution is less than 15 g / L, the first sodium aluminate solution will cause the carbonation decomposition reaction to be too fast, making it difficult to ultimately control the pH of the ultrafine aluminum hydroxide seed crystal inducer, and at the same time reduce the viscosity of the ultrafine aluminum hydroxide seed crystal inducer, greatly affecting the production capacity of the ultrafine aluminum hydroxide seed crystal inducer; when the mass concentration of aluminum oxide in the first sodium aluminate solution is greater than 45 g / L, the first sodium aluminate solution will be too viscous, reducing the fluidity of the first sodium aluminate solution; in addition, the viscous first sodium aluminate solution will cause serious agglomeration between the particles, which is not conducive to the preparation of ultrafine aluminum hydroxide seeds.

[0073] It should be noted that, when the caustic ratio of the second sodium aluminate solution is less than 1.40, the viscosity of the second sodium aluminate solution is poor, which makes the stability of the second sodium aluminate solution poor and the seed decomposition reaction difficult to control; in addition, the second sodium aluminate solution with poor viscosity is difficult to completely dissolve the ultrafine aluminum hydroxide seed inducer, so that the second sodium aluminate solution cannot explosively produce a large number of aluminum hydroxide nuclei, and ultimately the number of ultrafine aluminum hydroxide seeds is small and the particle size is large; when the caustic ratio of the second sodium aluminate solution is greater than 1.60, the decomposition power of the second sodium aluminate solution is small, which makes the decomposition rate of the second sodium aluminate solution too slow, and the nucleus growth rate is too fast, which results in the ultrafine aluminum hydroxide seeds having a coarse particle size and poor activity, which is not conducive to the subsequent preparation of ultrafine aluminum hydroxide.

[0074] It should be noted that when the mass concentration of aluminum oxide in the second sodium aluminate solution is less than 100 g / L, although the second sodium aluminate solution with a relatively dilute concentration will accelerate the rate of the seed decomposition reaction, the seed inducer is difficult to dissolve quickly in the second sodium aluminate solution with a relatively dilute concentration, so that the second sodium aluminate solution cannot explosively produce a large number of aluminum hydroxide nuclei, and ultimately the number of ultrafine aluminum hydroxide seeds is small and the particle size is large. At the same time, the sodium aluminate solution with a relatively dilute mass concentration will also reduce the viscosity of the ultrafine aluminum hydroxide seeds, greatly affecting the production capacity of the ultrafine aluminum hydroxide seeds; when the mass concentration of aluminum oxide in the second sodium aluminate solution is greater than 150 g / L, the second sodium aluminate solution will be too viscous, reducing the fluidity of the second sodium aluminate solution; in addition, the viscous second sodium aluminate solution will cause serious agglomeration between the particles, which is not conducive to the preparation of ultrafine aluminum hydroxide seeds.

[0075] Based on a general inventive concept, an embodiment of the present application provides an ultrafine aluminum hydroxide seed crystal, which is prepared by the preparation method.

[0076] The ultrafine aluminum hydroxide seed crystals are realized based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiments. Since the ultrafine aluminum hydroxide seed crystals adopt part or all of the technical solutions of the above-mentioned embodiments, they at least have all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.

[0077] Figure 2 The following is a schematic diagram showing a process flow of a method for preparing an ultrafine aluminum hydroxide product provided in an embodiment of the present application;

[0078] Based on a general inventive concept, the present invention provides a method for preparing an ultrafine aluminum hydroxide product, the method comprising:

[0079] S1. Inducing a decomposition reaction between the ultrafine aluminum hydroxide seed crystals prepared by the preparation method and a sodium aluminate solution raw material to obtain an ultrafine aluminum hydroxide product; wherein the caustic ratio of the sodium aluminate solution raw material is 1.40 to 1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L to 150 g / L.

[0080] The preparation method is implemented for the above-mentioned ultrafine aluminum hydroxide seeds. The specific characteristics of the ultrafine aluminum hydroxide seeds can be referred to the above-mentioned embodiments. Since the preparation method adopts part or all of the technical solutions of the above-mentioned embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above-mentioned embodiments, which will not be repeated here one by one.

[0081] It should be noted that the sodium aluminate solution raw material with a caustic ratio of 1.40 to 1.60 and the sodium aluminate solution raw material containing alumina at a mass concentration of 100 g / L to 150 g / L can fully induce decomposition reaction between the ultrafine aluminum hydroxide seeds and the sodium aluminate solution raw material, thereby promoting the conversion of the sodium aluminate solution raw material into an ultrafine aluminum hydroxide product under the action of the ultrafine aluminum hydroxide seeds.

[0082] The caustic ratio of the sodium aluminate solution feedstock may be 1.40, 1.45, 1.50, 1.55, or 1.60.

[0083] The mass concentration of aluminum oxide in the sodium aluminate solution raw material can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L.

[0084] It should be noted that, when the caustic ratio of the sodium aluminate solution raw material is less than 1.40, the composition of the sodium aluminate solution raw material is unstable, affecting the progress of the induced decomposition reaction; when the caustic ratio of the sodium aluminate solution raw material is greater than 1.60, the more stable the composition of the sodium aluminate solution raw material, the slower its decomposition rate; in addition, an excessively high caustic ratio will cause the pH of the sodium aluminate solution raw material to be too high, and the impurity content of the prepared ultrafine aluminum hydroxide product will be too high, requiring a large amount of washing water for cleaning.

[0085] It should be noted that when the mass concentration of alumina in the sodium aluminate solution raw material is less than 100 g / L, the viscosity of the slurry during the induced decomposition reaction will be low, making it difficult to obtain a sufficient amount of ultrafine aluminum hydroxide product. At the same time, the material used for the sodium aluminate solution raw material will increase, increasing the production cost. When the mass concentration of alumina in the sodium aluminate solution raw material is greater than 150 g / L, the viscosity of the slurry during the induced decomposition reaction will be greater, resulting in greater difficulty in decomposing the sodium aluminate solution raw material and a lower decomposition rate of the sodium aluminate solution raw material.

[0086] It should be noted that the raw material of the sodium aluminate solution is aluminum hydroxide, which is obtained by dissolving aluminum hydroxide and liquid alkali at a temperature of 102°C to 120°C, and then diluting and adjusting to a set caustic ratio and mass concentration of aluminum oxide.

[0087] It should be noted that the ultrafine aluminum hydroxide product obtained by the induced decomposition reaction is generally an ultrafine aluminum hydroxide product slurry. The following steps can be performed on the obtained ultrafine aluminum hydroxide product slurry:

[0088] The ultrafine aluminum hydroxide product slurry is subjected to solid-liquid separation, the obtained solid phase is ultrafine aluminum hydroxide, and the obtained liquid phase is ultrafine aluminum hydroxide mother liquor; the obtained ultrafine aluminum hydroxide mother liquor can be used to dissolve aluminum hydroxide again to prepare sodium aluminate solution;

[0089] The ultrafine aluminum hydroxide is washed with distilled water above 85° C., and then the washed solid phase is dried at 90° C. to obtain an ultrafine aluminum hydroxide product.

[0090] In some optional embodiments, the temperature of the induced decomposition reaction is 55° C. to 65° C., and the time of the induced decomposition reaction is 6 h to 7 h.

[0091] In these embodiments, the induced decomposition reaction at 55°C to 65°C for 6 to 7 hours can achieve a high degree of supersaturation in the sodium aluminate solution raw material, which is beneficial for the decomposition of the sodium aluminate solution raw material. Furthermore, the growth rate of the ultrafine aluminum hydroxide seed crystals can be controlled to be relatively slow. Therefore, under the action of the ultrafine aluminum hydroxide seed crystals, the sodium aluminate solution raw material can be decomposed into an ultrafine aluminum hydroxide product with a smaller particle size and higher purity.

[0092] The temperature for inducing the decomposition reaction may be 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, 61°C, 62°C, 63°C, 64°C or 65°C.

[0093] The time for inducing the decomposition reaction may be 6 h, 6.1 h, 6.2 h, 6.3 h, 6.4 h, 6.5 h, 6.6 h, 6.7 h, 6.8 h, 6.9 h or 7.0 h.

[0094] It should be noted that, when the temperature of the induced decomposition reaction is less than 55°C, the cohesiveness of the sodium aluminate solution raw material is too high, so that the content of alkaline substances between the crystals of the ultrafine aluminum hydroxide product is too high, which makes it easy for the ultrafine aluminum hydroxide products to agglomerate and form ultrafine aluminum hydroxide products with coarse particles; when the temperature of the induced decomposition reaction is greater than 65°C, the supersaturation of the sodium aluminate solution raw material is reduced, so that the decomposition rate of the sodium aluminate solution raw material is low, and a higher mass concentration of the sodium aluminate solution raw material is required, which increases the production cost.

[0095] In some optional embodiments, the mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(2-5):100.

[0096] In these embodiments, the mass ratio of the ultrafine aluminum hydroxide seeds to the aluminum oxide of the sodium aluminate solution raw material is (2-5):100, so that the sodium aluminate solution raw material can be fully decomposed under the action of the ultrafine aluminum hydroxide seeds to form a sufficient amount of ultrafine aluminum hydroxide product with fine particle size.

[0097] The mass m3 of the ultrafine aluminum hydroxide seed crystals can be 2, 3, 4 or 5.

[0098] It should be noted that, when the value of the mass m3 of the ultrafine aluminum hydroxide seeds is less than 2, the amount of ultrafine aluminum hydroxide seeds added is small, which makes the number of ultrafine aluminum hydroxide products obtained by decomposing the sodium aluminate solution raw material small, and the particle size of the ultrafine aluminum hydroxide is too large; when the value of the mass m3 of the ultrafine aluminum hydroxide seeds is greater than 5, the amount of fine aluminum hydroxide seeds added is too large, although it is conducive to the formation of ultrafine aluminum hydroxide products with fine particle size, the aluminum content of the sodium aluminate solution raw material is limited, and it is difficult to promote the complete development of ultrafine aluminum hydroxide crystals. The performance of the ultrafine aluminum hydroxide product finally obtained is poor.

[0099] Based on a general inventive concept, an embodiment of the present application provides an ultrafine aluminum hydroxide product, which is prepared by the preparation method.

[0100] The ultrafine aluminum hydroxide product is obtained based on the above-mentioned preparation method. The specific steps of the preparation method can refer to the above-mentioned embodiment. Since the ultrafine aluminum hydroxide product adopts part or all of the technical solutions of the above-mentioned embodiment, it has at least all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0101] The present application is further described below with reference to specific examples. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with national / industry standards. If there are no corresponding national / industry standards, the methods are carried out in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0102] Example 1

[0103] like Figure 1 As shown, a method for preparing ultrafine aluminum hydroxide seed crystals comprises:

[0104] S1. The carbon dioxide gas and the first sodium aluminate solution are subjected to a carbonation decomposition reaction to obtain ultrafine aluminum hydroxide seed crystals as an inducer; wherein the ultrafine aluminum hydroxide seed crystals inducer comprises a gel-like material, the mass of the gel-like material being greater than or equal to 90% of the ultrafine aluminum hydroxide seed crystals as an inducer;

[0105] S2. subjecting the ultrafine aluminum hydroxide seed crystal inducer to a seed decomposition reaction with the second sodium aluminate solution to obtain ultrafine aluminum hydroxide seed crystals.

[0106] The temperature of the carbonation decomposition reaction is 30°C, the time of the carbonation decomposition reaction is 20 minutes, and the end point pH of the carbonation decomposition reaction is 8.0;

[0107] The temperature of the seed crystal decomposition reaction is 60° C., and the time of the seed crystal decomposition reaction is 2.5 h.

[0108] The flow rate of carbon dioxide gas is 1.5m 3 / h.

[0109] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=25:100.

[0110] The caustic ratio of the first sodium aluminate solution is 1.33, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 15 g / L;

[0111] The caustic ratio of the second sodium aluminate solution is 1.40, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L.

[0112] The invention discloses an ultrafine aluminum hydroxide crystal seed, which is prepared by a preparation method.

[0113] Example 2

[0114] Compared with Example 1, this embodiment has the following differences, and the rest are the same:

[0115] The temperature of the carbonation decomposition reaction is 15°C, the time of the carbonation decomposition reaction is 8 minutes, and the end point pH of the carbonation decomposition reaction is 8.3;

[0116] The temperature of the seed crystal decomposition reaction is 50° C., and the time of the seed crystal decomposition reaction is 3.5 h.

[0117] The flow rate of carbon dioxide gas is 5.0m 3 / h.

[0118] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=50:100.

[0119] The caustic ratio of the first sodium aluminate solution is 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 45 g / L;

[0120] The caustic ratio of the second sodium aluminate solution is 1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 150 g / L.

[0121] Example 3

[0122] Compared with Example 1, this embodiment has the following differences, and the rest are the same:

[0123] The temperature of the carbonation decomposition reaction is 25°C, the time of the carbonation decomposition reaction is 3 minutes, and the end point pH of the carbonation decomposition reaction is 8.5;

[0124] The temperature of the seed crystal decomposition reaction is 40° C., and the time of the seed crystal decomposition reaction is 3.5 h.

[0125] The flow rate of carbon dioxide gas is 3.0m 3 / h.

[0126] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=40:100.

[0127] The caustic ratio of the first sodium aluminate solution is 1.50, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 25 g / L;

[0128] The caustic ratio of the second sodium aluminate solution is 1.50, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 130 g / L.

[0129] Comparative Example 1

[0130] Compared with Example 1, the differences of this comparative example are as follows, and the rest are the same:

[0131] The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=60:100.

[0132] The temperature of the seed crystal decomposition reaction is 60°C.

[0133] The caustic ratio of the second sodium aluminate solution was 1.30.

[0134] Comparative Example 2

[0135] Compared with Example 1, the differences of this comparative example are as follows, and the rest are the same:

[0136] The temperature of the carbonation decomposition reaction is 40°C.

[0137] The flow rate of carbon dioxide gas is 0.5m 3 / h.

[0138] The caustic ratio of the first sodium aluminate solution is 1.65, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 50 g / L.

[0139] Example 4

[0140] Based on the content disclosed in Example 1, the preparation of ultrafine aluminum hydroxide product is further carried out, and the specific process is as follows:

[0141] like Figure 2 As shown, a method for preparing an ultrafine aluminum hydroxide product comprises:

[0142] S1. The ultrafine aluminum hydroxide seed crystals prepared by the preparation method and the sodium aluminate solution raw material were subjected to an induced decomposition reaction to obtain an ultrafine aluminum hydroxide product slurry; wherein the caustic ratio of the sodium aluminate solution raw material is 1.45, and the mass concentration of alumina in the sodium aluminate solution raw material is 150g / L;

[0143] The ultrafine aluminum hydroxide product slurry is subjected to solid-liquid separation, the obtained solid phase is ultrafine aluminum hydroxide, and the obtained liquid phase is ultrafine aluminum hydroxide mother liquor; the obtained ultrafine aluminum hydroxide mother liquor can be used to dissolve aluminum hydroxide again to prepare sodium aluminate solution;

[0144] The ultrafine aluminum hydroxide is washed with distilled water above 85° C., and then the washed solid phase is dried at 90° C. to obtain an ultrafine aluminum hydroxide product.

[0145] The temperature for inducing the decomposition reaction is 55° C., and the time for inducing the decomposition reaction is 6 h.

[0146] The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=5:100.

[0147] A superfine aluminum hydroxide product is prepared by a preparation method.

[0148] Example 5

[0149] Compared with Example 4, this embodiment has the following differences, and the rest are the same:

[0150] The ultrafine aluminum hydroxide seeds obtained in Example 2 were used.

[0151] The caustic ratio of the sodium aluminate solution raw material is 1.50, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L.

[0152] The temperature for inducing the decomposition reaction is 65°C, and the time for inducing the decomposition reaction is 7 hours.

[0153] The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=5:100.

[0154] Example 6

[0155] Compared with Example 4, this embodiment has the following differences, and the rest are the same:

[0156] The ultrafine aluminum hydroxide seeds obtained in Example 3 were used.

[0157] The caustic ratio of the sodium aluminate solution raw material is 1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 120 g / L.

[0158] The temperature for inducing the decomposition reaction is 60° C., and the time for inducing the decomposition reaction is 7 h.

[0159] The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=4:100.

[0160] Comparative Example 3

[0161] Compared with Example 4, the differences of this comparative example are as follows, and the rest are the same:

[0162] The ultrafine aluminum hydroxide seeds obtained in Comparative Example 1 were used.

[0163] Comparative Example 4

[0164] Compared with Example 4, the differences of this comparative example are as follows, and the rest are the same:

[0165] The ultrafine aluminum hydroxide seeds obtained in Comparative Example 2 were used.

[0166] Comparative Example 5

[0167] Compared with Example 4, the differences of this comparative example are as follows, and the rest are the same:

[0168] The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=1:100

[0169] The temperature for inducing the decomposition reaction is 70°C.

[0170] Related experiments and effect data:

[0171] The ultrafine aluminum hydroxide seed crystals prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were tested for particle size, and the results are shown in Table 1. In addition, the ultrafine aluminum hydroxide products prepared in Examples 4 to 6 and Comparative Examples 3 to 5 were tested for particle size, alkali content, and oil absorption, and the results are shown in Table 2.

[0172] Table 1 Particle size test data of ultrafine aluminum hydroxide seeds obtained in Examples and Comparative Examples

[0173]

[0174] Table 2 Performance data of ultrafine aluminum hydroxide products obtained in Examples and Comparative Examples

[0175]

[0176] As can be seen from Table 1, the ultrafine aluminum hydroxide seeds prepared in Examples 1 to 3 have a median particle size (D50) of 0.241 μm to 0.312 μm and a coarse end particle size (D90) of 0.398 μm to 0.494 μm. The particle size of these ultrafine aluminum hydroxide seeds is smaller than the average particle size of the seeds of aluminum hydroxide micropowder produced by conventional mechanical grinding (D50 < 2 μm), and the particle size distribution of these ultrafine aluminum hydroxide seeds is more concentrated, and they have higher reaction activity.

[0177] Compared with Example 1, the preparation processes of the ultrafine aluminum hydroxide seeds used in Comparative Examples 1 and 2 are different. When the amount of ultrafine aluminum hydroxide seed inducer added is too much, the temperature of the carbonation decomposition reaction and the seed decomposition reaction is too high, the caustic ratio of the first sodium aluminate solution is too small, or the flow rate of the carbon dioxide gas is too small, the median particle size of the prepared ultrafine aluminum hydroxide seeds is above 3.0 μm, which is obviously larger than the ultrafine aluminum hydroxide seeds prepared by the preparation method of the embodiment of the present application, and the actual reaction activity is poor. The particle size of the ultrafine aluminum hydroxide product finally prepared is large and the particle size distribution is uneven.

[0178] As shown in Table 2, the D50 of the ultrafine aluminum hydroxide products prepared in Examples 4 to 6 is 0.395 μm to 0.487 μm, and the D90 is 0.562 μm to 0.608 μm. The D50 of these ultrafine aluminum hydroxide products is less than 0.5 μm and the D90 is less than or equal to 0.61 μm, indicating that the particle size of these ultrafine aluminum hydroxide products is small and the particle size distribution is concentrated. In addition, the sodium oxide content of these ultrafine aluminum hydroxide products is 0.194% to 0.233%, and the oil absorption is 26 mL / 100 g to 28 mL / 100 g, with low impurity content and low oil absorption.

[0179] Compared with Example 4, the preparation process of the ultrafine aluminum hydroxide products used in Comparative Examples 3 to 5 is different. The use of coarser ultrafine aluminum hydroxide seeds and the higher induced decomposition reaction temperature are not conducive to the induction of decomposition reaction to generate ultrafine aluminum hydroxide products with small and uniform particle size. It can be seen from the data in Table 2 that the ultrafine aluminum hydroxide products prepared in Comparative Examples 3 to 5 have a larger particle size and an uneven particle size distribution; in addition, the ultrafine aluminum hydroxide products of Comparative Examples 3 to 5 have a higher sodium oxide impurity content.

[0180] In summary, the present invention provides a method for preparing ultrafine aluminum hydroxide seed crystals. This method, through the triple synergy of gel dissolution, low-temperature growth, and defect fixation, enables the product to simultaneously possess the following characteristics: nanoscale particle size distribution, high active specific surface area, and low residual alkali content. The final ultrafine aluminum hydroxide seed crystals have a median particle size of 0.241 μm to 0.312 μm, and a coarse end particle size of 0.398 μm to 0.494 μm.

[0181] In addition, an embodiment of the present application provides a method for preparing an ultrafine aluminum hydroxide product, which uses the above-mentioned ultrafine aluminum hydroxide seeds with fine particle size and good activity to induce a decomposition reaction of the sodium aluminate solution raw material, thereby obtaining an ultrafine aluminum hydroxide product with a median particle size of 0.395μm to 0.487μm, a coarse end particle size of 0.562μm to 0.608μm and a sodium oxide content of less than 0.25%.

[0182] In addition, the embodiment of the present application provides an ultrafine aluminum hydroxide product, which can be used as a raw material for making plastics and rubber products, as a brightener and whitening agent in the papermaking industry, as a raw material for aluminum salt production, and as a raw material for preparing ultrafine alumina.

[0183] The foregoing is merely a detailed description of the present invention, intended to enable those skilled in the art to understand or implement the present invention. 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 invention. Therefore, the present invention is not limited to the embodiments shown herein, but rather is intended to conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing ultrafine aluminum hydroxide seed crystals, the preparation method comprising: Carrying out a carbonation decomposition reaction between carbon dioxide gas and the first sodium aluminate solution to obtain an ultrafine aluminum hydroxide crystal seed inducer; wherein the ultrafine aluminum hydroxide crystal seed inducer comprises a gel-like material, and the mass of the gel-like material is greater than or equal to 90% of the ultrafine aluminum hydroxide crystal seed inducer; The ultrafine aluminum hydroxide seed crystal inducer and the second sodium aluminate solution are subjected to a seed decomposition reaction to obtain ultrafine aluminum hydroxide seed crystals; wherein the temperature of the seed decomposition reaction is ≤60°C.

2. The preparation method according to claim 1, characterized in that The temperature of the carbonation decomposition reaction is 15° C. to 30° C., the time of the carbonation decomposition reaction is 1 min to 20 min, and the endpoint pH of the carbonation decomposition reaction is 8.0 to 8.5; and / or The temperature of the seed crystal decomposition reaction is 40° C. to 60° C., and the time of the seed crystal decomposition reaction is 2.5 h to 3.5 h.

3. The preparation method according to claim 1, characterized in that The flow rate of the carbon dioxide gas is 1.5m 3 / h~5.0m 3 / h.

4. The preparation method according to claim 1, characterized in that The mass m1 of the ultrafine aluminum hydroxide crystal seed inducer and the mass m2 of the aluminum oxide in the second sodium aluminate solution satisfy the relationship: m1:m2=(25-50):

100.

5. The preparation method according to claim 1, characterized in that The caustic ratio of the first sodium aluminate solution is 1.30 to 1.60, and the mass concentration of aluminum oxide in the first sodium aluminate solution is 15 g / L to 45 g / L; and / or The caustic ratio of the second sodium aluminate solution is 1.40-1.60, and the mass concentration of aluminum oxide in the second sodium aluminate solution is 100 g / L-150 g / L.

6. An ultrafine aluminum hydroxide seed crystal, which is prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing an ultrafine aluminum hydroxide product, the preparation method comprising: The ultrafine aluminum hydroxide seed crystals prepared by the preparation method according to any one of claims 1 to 5 and the sodium aluminate solution raw material are subjected to an induced decomposition reaction to obtain an ultrafine aluminum hydroxide product; wherein the caustic ratio of the sodium aluminate solution raw material is 1.40 to 1.60, and the mass concentration of aluminum oxide in the sodium aluminate solution raw material is 100 g / L to 150 g / L.

8. The preparation method according to claim 7, characterized in that The temperature of the induced decomposition reaction is 55° C. to 65° C., and the time of the induced decomposition reaction is 6 h to 7 h.

9. The preparation method according to claim 7, characterized in that The mass m3 of the ultrafine aluminum hydroxide seed crystals and the mass m4 of the aluminum oxide of the sodium aluminate solution raw material satisfy the relationship: m3:m4=(2-5):

100.

10. An ultrafine aluminum hydroxide product, prepared by the preparation method according to any one of claims 7 to 9.

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