Preparation method of micro-powder aluminum hydroxide with low oil absorption rate

Abstract

The invention provides a preparation method of micro-powder aluminum hydroxide with low oil absorption rate, and belongs to the field of aluminum hydroxide preparation. The method comprises the following steps: obtaining a sodium aluminate solution with set alpha k and set alumina concentration; aluminum hydroxide seed slurry with set granularity and set solid content is obtained; adding the aluminum hydroxide seed slurry into a sodium aluminate solution, and performing seed decomposition under set conditions to obtain mixed slurry; and carrying out solid-liquid separation on the mixed slurry to obtain the micro-powder aluminum hydroxide. By adjusting alpha k and aluminum oxide concentration of the sodium aluminate solution, finer aluminum hydroxide particles with more uniform particle size can be obtained, so that the oil absorption rate is reduced; the particle size and the solid content of the aluminum hydroxide seed slurry are optimized, the particle size distribution of the product can be controlled, meanwhile, the proper solid content can ensure that the decomposition process is carried out uniformly, aluminum hydroxide particles with uniform particle size can be obtained, and thus the oil absorption rate of the micro-powder aluminum hydroxide is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of aluminum hydroxide preparation, and in particular to a method for preparing micro-powdered aluminum hydroxide with low oil absorption rate. Background Art

[0002] At present, the technology of domestic flame retardant micro-powder aluminum hydroxide has been greatly improved, and the product particle size and oil absorption rate have reached a certain technical level. For example, in terms of particle size, large particles have been controlled to a certain extent. When d50 is 1.4μm, d90 can be controlled below 2.2μm, and the oil absorption rate is reduced from more than 40mL / 100g to 36mL / 100g. The downstream cable processing performance is further improved, the cable extrusion defects are further reduced, and the pay-off speed is significantly improved.

[0003] However, the oil absorption rate of micronized aluminum hydroxide is still far behind that of advanced foreign companies, and is basically around 36mL / 100g, which leads to high mixing viscosity and high melt index of cables, becoming the main problem in my country's wire and cable processing. Therefore, how to reduce the oil absorption rate of micronized aluminum hydroxide is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application provides a method for preparing micro-powder aluminum hydroxide with low oil absorption rate to solve the following technical problem: how to reduce the oil absorption rate of micro-powder aluminum hydroxide.

[0005] The present application provides a method for preparing micro-powder aluminum hydroxide with low oil absorption rate, the method comprising:

[0006] Obtaining a sodium aluminate solution having a set αk and a set alumina concentration;

[0007] Obtaining an aluminum hydroxide seed slurry having a set particle size and a set solid content;

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

[0009] The mixed slurry is subjected to solid-liquid separation to obtain fine powder aluminum hydroxide.

[0010] Optionally, the setting αk is 1.3 to 1.6.

[0011] Optionally, the sodium aluminate solution includes: aluminum hydroxide heavy solution or Bayer process semen; wherein,

[0012] When the sodium aluminate solution is a heavy aluminum hydroxide solution, the αk of the heavy aluminum hydroxide solution is 1.4 to 1.6; and / or,

[0013] When the sodium aluminate solution is Bayer process semen, the αk of the Bayer process semen is 1.35-1.45.

[0014] Optionally, the set alumina concentration is 80g / L to 160g / L.

[0015] Optionally, the set particle size is 2.5 μm to 3.5 μm.

[0016] Optionally, the solid content is set to 200g / L to 300g / L.

[0017] Optionally, the mass of the aluminum hydroxide seeds in the aluminum hydroxide seed slurry is 0.5% to 3.5% of the total mass of the sodium aluminate solution.

[0018] Optionally, the set conditions include at least one of the following: a seeding temperature of 55°C to 70°C, a seeding time of 8h to 24h, and a stirring speed of 200rpm / min to 300rpm / min.

[0019] Optionally, the method for preparing the aluminum hydroxide seed slurry comprises:

[0020] The raw materials and the solvent are pulped and ground to obtain an initial seed slurry; the raw materials include: one or more of α aluminum hydroxide trihydrate, Bayerite and diaspore, the particle size of the initial seed slurry is 1.5 μm to 4.5 μm, and the solid content of the initial seed slurry is 150 g / L to 550 g / L;

[0021] The initial seed slurry is added to the sodium aluminate solution to perform seed decomposition to obtain a seed slurry; the mass of the aluminum hydroxide seeds in the initial seed slurry is 0.5% to 5.5% of the total mass of the sodium aluminate solution, the temperature of the seed decomposition is 35° C. to 75° C., the time of the seed decomposition is 8 h to 24 h, and the stirring speed of the seed decomposition is 200 rpm / min to 400 rpm / min;

[0022] The seed slurry is subjected to solid-liquid separation to obtain aluminum hydroxide seeds;

[0023] The aluminum hydroxide seeds and the solvent are slurried and ground to obtain the aluminum hydroxide seed slurry.

[0024] Optionally, the micro-powder aluminum hydroxide satisfies at least one of the following properties: oil absorption rate ≤30mL / 100g, particle size of 1.2μm to 1.5μm, and loose bulk density ≥0.5g / mL.

[0025] The above technical solution provided by the embodiment of the present application has the following advantages compared with the prior art:

[0026] The present application embodiment provides a method for preparing a micro-powder aluminum hydroxide with low oil absorption rate, which includes: obtaining a sodium aluminate solution with a set αk and a set aluminum oxide concentration; obtaining an aluminum hydroxide seed slurry with a set particle size and a set solid content; adding the aluminum hydroxide seed slurry to the sodium aluminate solution to perform seed decomposition under set conditions to obtain a mixed slurry; and performing solid-liquid separation on the mixed slurry to obtain micro-powder aluminum hydroxide. First, by adjusting the αk and aluminum oxide concentration of the sodium aluminate solution, the appropriate αk and aluminum oxide concentration can affect the rate of seed decomposition and the particle size distribution of the product, so that aluminum hydroxide particles with more uniform particle size and finer particles can be obtained, thereby reducing the oil absorption rate; secondly, the particle size and solid content of the aluminum hydroxide seed slurry are optimized, and by selecting seeds with appropriate particle size, the particle size distribution of the product can be controlled to avoid the formation of too large or too small particles. At the same time, the appropriate solid content can ensure that the decomposition process is carried out uniformly, which is conducive to obtaining aluminum hydroxide particles with uniform particle size; finally, by controlling the conditions of seed decomposition, finer and more uniform aluminum hydroxide particles can be obtained. Thereby reducing the oil absorption rate of micro-powder aluminum hydroxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings herein are incorporated in and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the description, are used to explain the principles of the present application.

[0028] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 A schematic flow chart of a method for preparing a micro-powdered aluminum hydroxide with low oil absorption rate provided in an embodiment of the present application;

[0030] Figure 2 This is a SEM image of the micro-powder aluminum hydroxide provided in Example 1 of the present application (magnification is 25000 times);

[0031] Figure 3 This is the SEM image of the micro-powder aluminum hydroxide provided in Example 1 of the present application (magnification is 15,000 times). DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] 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 herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0034] In addition, in the description of the specification of the present application, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second", etc. are only 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" means one or more, and "plurality" means two or more. "At least one", "the following at least one item (items)" or similar expressions refer to any combination of these items, including any combination of single items (items) or plural items (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 indicate 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, 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 with 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.

[0035] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0036] Figure 1 A schematic flow chart of a method for preparing micro-powdered aluminum hydroxide with low oil absorption provided in an embodiment of the present application.

[0037] like Figure 1 As shown, the present application embodiment provides a method for preparing micro-powder aluminum hydroxide with low oil absorption rate, the method comprising:

[0038] S1, obtaining a sodium aluminate solution having a set αk and a set alumina concentration;

[0039] The purpose of step S1 is to prepare a clean and uniform liquid reaction system, which is conducive to the uniform diffusion of aluminum hydroxide seeds therein, thereby ensuring that aluminum hydroxide is precipitated synchronously at various points in the system.

[0040] In some embodiments, the setting αk is 1.3-1.6.

[0041] In the process of preparing micro-powder aluminum hydroxide with low oil absorption rate, setting αk (the caustic ratio of sodium aluminate solution, that is, the molar ratio of sodium oxide to aluminum oxide in the solution) in the range of 1.3 to 1.6 plays a vital role. The setting of this range ensures the stability and controllability of the liquid system, and has a significant impact on achieving stable precipitation of aluminum hydroxide and optimizing its particle size distribution. When αk is lower than 1.3, the liquid system may become unstable, which will affect the precipitation process of aluminum hydroxide, resulting in difficulty in controlling the particle size of the precipitated aluminum hydroxide, and may result in uneven particle size distribution or the formation of oversized particles. This instability is not conducive to the preparation of micro-powder aluminum hydroxide with uniform particle size and low oil absorption rate. When αk is higher than 1.6, the precipitation process of aluminum hydroxide will be inhibited, and it may even cause aluminum hydroxide to fail to precipitate. This is because the excessively high caustic ratio increases the activation energy of aluminum hydroxide precipitation, making the precipitation process difficult. This will not only reduce production efficiency, but also fail to obtain the desired aluminum hydroxide product. However, when αk is set in the range of 1.3 to 1.6, the liquid system becomes relatively stable and easy to control. The caustic ratio within this range is conducive to the stable precipitation of aluminum hydroxide, and micro-powder aluminum hydroxide with uniform particle size and good dispersibility can be prepared. In addition, this stability also helps to optimize the particle size distribution of aluminum hydroxide, thereby further reducing its oil absorption rate. Exemplarily, the αk of the sodium aluminate solution can be 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, etc.

[0042] In some embodiments, the sodium aluminate solution comprises: a heavy aluminum hydroxide solution or a Bayer process semen; wherein,

[0043] When the sodium aluminate solution is a heavy aluminum hydroxide solution, the αk of the heavy aluminum hydroxide solution is 1.4 to 1.6; and / or,

[0044] When the sodium aluminate solution is Bayer process semen, the αk of the Bayer process semen is 1.35-1.45.

[0045] In the process of preparing low oil absorption micronized aluminum hydroxide, the preparation of sodium aluminate solution is one of the key steps. According to the description, the sodium aluminate solution can be prepared by re-dissolving aluminum hydroxide or using Bayer process semen. The preparation of sodium aluminate solution by re-dissolving aluminum hydroxide is to dissolve aluminum hydroxide in sodium hydroxide solution to form a sodium aluminate solution. The Bayer process is a method for producing aluminum oxide, and its semen contains a high concentration of sodium aluminate. By adjusting the process conditions, a sodium aluminate solution suitable for preparing low oil absorption micronized aluminum hydroxide can be directly obtained from the Bayer process semen.

[0046] The αk of the heavy aluminum hydroxide solution is 1.4 to 1.6. When the αk value is lower than 1.4, the liquid system tends to become unstable and hydrolyze. In the production process, this instability may cause the solution to hydrolyze during storage and buffering, thereby affecting the subsequent production organization. In addition, it will also cause the aluminum hydroxide to precipitate too quickly, and it is not easy to control its particle size and morphology. At the same time, too fast crystallization will also lead to excessive intercrystalline alkali entrainment, which increases the sodium oxide content in the product. When the αk value is higher than 1.6, the sodium aluminate solution becomes too stable, and the rate of precipitation of aluminum hydroxide will decrease, which will not only affect production efficiency, but also increase production costs. In order to balance the stability of the liquid system and the precipitation rate of aluminum hydroxide, the αk value is usually set in the range of 1.4 to 1.6, which is conducive to the preparation of micro-powder aluminum hydroxide with uniform particle size and good dispersibility, and reduce its oil absorption rate. Exemplarily, the αk of the heavy aluminum hydroxide solution can be 1.4, 1.45, 1.5, 1.55, 1.6, etc.

[0047] The αk value of the Bayer process solution is usually set in the range of 1.35 to 1.45. Since the Bayer process solution itself has a high stability, the αk value can be slightly lower, which is conducive to the precipitation of aluminum hydroxide, while reducing the entrainment of intercrystalline alkali and reducing the sodium oxide content in the product. For example, the αk of the Bayer process semen is 1.35, 1.40, 1.42, 1.45, etc.

[0048] In summary, when preparing low oil absorption micro-powder aluminum hydroxide, the preparation method of sodium aluminate solution and the setting of αk value are both crucial. By selecting a suitable preparation method and setting a reasonable αk value range, micro-powder aluminum hydroxide products with uniform particle size, good dispersibility and low oil absorption can be prepared.

[0049] In some embodiments, the set aluminum oxide concentration is 80 g / L to 160 g / L.

[0050] Limiting the concentration of aluminum oxide in the sodium aluminate solution to 80g / L to 160g / L is not only conducive to the stable precipitation of aluminum hydroxide, improving production efficiency and yield, but also reasonably controlling costs while ensuring product quality. When the concentration of aluminum oxide is lower than 80g / L, the liquid system may be too diluted, resulting in difficulty in the precipitation of aluminum hydroxide. Similarly, a concentration higher than 160g / L may also cause the system to be too stable, which is not conducive to the precipitation of aluminum hydroxide. Within this concentration range, the liquid system will neither be too diluted nor too stable, which is conducive to the stable precipitation of aluminum hydroxide. Exemplarily, the concentration of aluminum oxide in the sodium aluminate solution can be 80g / L, 90g / L, 100g / L, 110g / L, 120g / L, 130g / L, 140g / L, 150g / L, 160g / L, etc.

[0051] S2, obtaining an aluminum hydroxide seed slurry having a set particle size and a set solid content;

[0052] In the process of preparing low oil absorption micro-powder aluminum hydroxide, obtaining aluminum hydroxide seed slurry with a set particle size and a set solid content is a crucial step. The purpose of this step is to ensure that the aluminum hydroxide seeds can be evenly distributed and can be quickly and evenly diffused after being added to the liquid reaction system, thereby achieving effective control of the precipitation rate and particle size of aluminum hydroxide.

[0053] In some embodiments, the set particle size is 2.5 μm to 3.5 μm.

[0054] When the particle size of the aluminum hydroxide seed crystal is set in the range of 2.5 μm to 3.5 μm, the surface energy of the seed crystal is moderate, neither too large to cause the precipitation rate to be too fast and difficult to control, nor too small to cause the precipitation rate to be too slow or uneven. This moderate surface energy is conducive to the stable precipitation of aluminum hydroxide in the liquid system, making the precipitation rate controllable and uniform. At the same time, the appropriate seed crystal particle size also helps to control the particle size of the final product. The seed crystal with moderate particle size can serve as a "template" during the precipitation process to guide the aluminum hydroxide particles to grow in a more uniform manner, thereby reducing the fluctuation of the product particle size and improving the uniformity and quality of the product. The particle size of the aluminum hydroxide seed in the aluminum hydroxide seed slurry can be 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 3.0 μm, 3.2 μm, 3.4 μm, 3.5 μm, etc.

[0055] In some embodiments, the solid content is set to be 200 g / L to 300 g / L.

[0056] By setting the solid content in the range of 200g / L to 300g / L, the diffusion rate of aluminum hydroxide seeds in the liquid system and the dilution degree of the liquid system can be balanced. When the solid content is too low, the seed slurry is easy to bring in more water, resulting in the dilution of the liquid system, which is not conducive to the stable precipitation of aluminum hydroxide; when the solid content is too high, the diffusion rate of the seeds in the liquid system will slow down, and may even form agglomerates, which is also not conducive to the uniform precipitation of aluminum hydroxide. At the same time, an appropriate solid content range can also improve production efficiency. When the solid content is moderate, the seeds can quickly diffuse to various parts of the liquid system, making the precipitation process of aluminum hydroxide more uniform and efficient. This can not only shorten the production cycle, but also reduce energy consumption and waste of raw materials. Exemplary, the solid content of the aluminum hydroxide seed slurry can be 200g / L, 220g / L, 240g / L, 260g / L, 280g / L, 300g / L, etc.

[0057] In some embodiments, the method for preparing the aluminum hydroxide seed slurry comprises:

[0058] S201, beating and grinding the raw materials and the solvent to obtain an initial seed slurry; the raw materials include: one or more of α aluminum hydroxide trihydrate, bayerite and diaspore, the particle size of the initial seed slurry is 1.5 μm to 4.5 μm, and the solid content of the initial seed slurry is 150 g / L to 550 g / L;

[0059] The solid content of the initial seed slurry is limited to 150g / L to 550g / L. When the solid content is lower than 150g / L, the seed slurry is easy to bring in more water, diluting the seed solution. When the solid content is higher than 550g / L, the slurry is viscous in the later stage of grinding, the particle dispersion is poor, and it is not easy to grind. The particle size of the initial seed slurry is controlled to be 1.5μm to 4.5μm. If the particle size is too small, the decomposed aluminum hydroxide is fine, and if the particle size is too large, the prepared aluminum hydroxide particle size is coarse. Exemplarily, the particle size of the initial seed slurry can be 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, etc., and the solid content of the initial seed slurry can be 150g / L, 200g / L, 250g / L, 300g / L, 400g / L, 500g / L, 550g / L, etc.

[0060] S202, adding the initial seed slurry to the sodium aluminate solution to perform seed decomposition to obtain a seed slurry; the mass of the aluminum hydroxide seeds in the initial seed slurry is 0.5% to 5.5% of the total mass of the sodium aluminate solution, the temperature of the seed decomposition is 35° C. to 75° C., the time of the seed decomposition is 8 h to 24 h, and the stirring speed of the seed decomposition is 200 rpm / min to 400 rpm / min;

[0061] The mass of the aluminum hydroxide seeds in the initial seed slurry is set to 0.5% to 5.5% of the total mass of the sodium aluminate solution. The setting of this ratio range is intended to ensure that the aluminum hydroxide seeds can fully play their role as crystal nuclei and promote the orderly precipitation of aluminum hydroxide in the liquid system. At the same time, an appropriate amount of seed crystals can provide sufficient activation energy so that aluminum hydroxide can be precipitated stably and orderly in the liquid system. When the amount of seed crystals added is too small, the activation energy is insufficient and the precipitation of aluminum hydroxide is difficult; when the amount added is too high, the activation energy is excessive, which may cause aluminum hydroxide to precipitate rapidly and disorderly, which is not conducive to controlling the product particle size. Exemplarily, the mass of the aluminum hydroxide seeds in the initial seed slurry is 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, 5.5%, etc. of the total mass of the sodium aluminate solution.

[0062] The temperature of the seed decomposition is set at 35°C to 75°C. This temperature range is set to balance the viscosity of the system and the precipitation rate of aluminum hydroxide. When the temperature is too low, the system becomes viscous, which is not conducive to the diffusion of substances and the precipitation of aluminum hydroxide; when the temperature is too high, the generated aluminum hydroxide may dissolve again under alkaline conditions, reducing the precipitation efficiency. In the range of 35°C to 75°C, the system is neither too viscous nor causes the dissolution of aluminum hydroxide, which is conducive to the stable precipitation of aluminum hydroxide.

[0063] The time for seed decomposition is set to 8 hours to 24 hours. This time range is set to ensure the full precipitation of aluminum hydroxide and the effective use of raw materials. When the time is too short, the decomposition rate is too low, resulting in reduced yield and raw material loss; when the time is too long, although the yield can be further improved, the αk value will increase as the reaction proceeds. When the αk value reaches a certain level, the precipitation and dissolution of aluminum hydroxide will reach a balance. At this time, continuing to extend the reaction time will have limited effect on improving the yield. Therefore, seed decomposition within the range of 8 hours to 24 hours can ensure the full precipitation of aluminum hydroxide and the effective use of raw materials.

[0064] The stirring speed is set to 200 rpm to 400 rpm. The setting of this speed range is intended to balance the diffusion of the substance and the particle size control of aluminum hydroxide. When the stirring speed is slow, it is not conducive to the diffusion of the substance and the uniform precipitation of aluminum hydroxide; when the stirring speed is fast, although the diffusion speed of the substance can be accelerated, it may also cause the precipitated aluminum hydroxide particles to break due to the intensified collision, which is not conducive to controlling the product particle size. Stirring in the range of 200 rpm to 400 rpm can ensure the uniform diffusion of the substance and the stable precipitation of aluminum hydroxide. Exemplarily, the temperature of the seed decomposition can be 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, etc., the time of the seed decomposition can be 8h, 10h, 15h, 20h, 22h, 24h, etc., and the stirring speed of the seed decomposition can be 200rpm / min, 250rpm / min, 300rpm / min, 350rpm / min, 400rpm / min, etc.

[0065] The solution temperature is 35-75°C (if the temperature is too low, the system becomes viscous and is not conducive to material diffusion. If the temperature is too high, the generated aluminum hydroxide will dissolve again under alkaline conditions. Therefore, the temperature in this experiment is selected to be within the above range), the amount of sand mill seeds added is 0.5-3.5% (based on alumina) (the amount of seed crystals added should take into account the activation energy they provide. If the amount is too small, the activation energy is not enough to precipitate aluminum hydroxide. If the amount is too high, the activation energy will cause aluminum hydroxide to precipitate quickly and disorderly, which is not conducive to controlling the product particle size and increasing raw material consumption), the stirring speed is controlled to be 200-400 rpm (slow stirring speed is not conducive to material diffusion, and fast stirring speed will cause the precipitated aluminum hydroxide to collide more violently, which is not conducive to controlling the particle size and increasing energy consumption. Therefore, the stirring speed in this experiment is selected to be within the above range), and the seeding time is 8-24h (short time will result in incomplete reaction, resulting in reduced yield and raw material consumption. As the reaction proceeds, αk increases. To a certain extent, the precipitation and dissolution of aluminum hydroxide reach equilibrium. Therefore, the reaction time in this experiment is selected to be within the above range

[0066] S203, performing solid-liquid separation on the seed slurry to obtain aluminum hydroxide seeds;

[0067] S204, slurrying and grinding the aluminum hydroxide seeds and the solvent to obtain the aluminum hydroxide seed slurry.

[0068] S3, adding the aluminum hydroxide seed slurry to the sodium aluminate solution to perform seed decomposition under set conditions to obtain a mixed slurry; and

[0069] The purpose of step S3 is to control the reaction conditions to precipitate aluminum hydroxide.

[0070] In some embodiments, the mass of the aluminum hydroxide seeds in the aluminum hydroxide seed slurry is 0.5% to 3.5% of the total mass of the sodium aluminate solution.

[0071] In some embodiments, the set conditions include at least one of the following: a seeding temperature of 55°C to 70°C, a seeding time of 8h to 24h, and a stirring speed of 200rpm / min to 300rpm / min.

[0072] S4, separating the mixed slurry into solid and liquid to obtain fine powder aluminum hydroxide.

[0073] In some embodiments, the micro-powder aluminum hydroxide satisfies at least one of the following properties: oil absorption rate ≤ 30 mL / 100 g, particle size of 1.2 μm to 1.5 μm, and loose bulk ratio ≥ 0.5 g / mL.

[0074] The embodiment of the present application provides a method for preparing micro-powder aluminum hydroxide with low oil absorption rate. The preparation method can not only effectively control the particle size and dispersion of micro-powder aluminum hydroxide, but also reduce the oil absorption rate of micro-powder aluminum hydroxide, which is beneficial for downstream customers to improve the quality of processed cables.

[0075] In some embodiments, after step S4, the method further comprises:

[0076] The micro powder aluminum hydroxide is washed and dried; the washing water temperature is above 70°C, the washing is completed after the pH value of the washing water reaches 7, the drying temperature is 80°C, and the drying time is 10 hours.

[0077] The liquid system of the decomposition is strongly alkaline, and the precipitated aluminum hydroxide has alkali attached to its surface, which needs to be washed with water to neutrality for use by downstream customers. The higher the temperature of the washing water, the more conducive it is to quickly wash away the attached alkali. For the safety of the operator, the washing water is controlled at 70°C. Too high a drying temperature can easily cause the hydrogen and oxygen atoms in aluminum hydroxide to be lost in the form of water molecules, resulting in product deformation. Too low a temperature will prolong the drying time. The drying temperature is limited to 80°C and the drying time is 10 hours, which can ensure the safe and effective drying of aluminum hydroxide.

[0078] The present application provides a method for preparing micro-powdered aluminum hydroxide with low oil absorption rate, the advantages of which are mainly reflected in the following aspects:

[0079] 1. Precise control of process parameters

[0080] (1) Caustic ratio (αk) and alumina concentration of sodium aluminate solution: By setting αk in the range of 1.3 to 1.6, the stability and controllability of the liquid system are ensured, which is conducive to the stable precipitation of aluminum hydroxide and the optimization of particle size distribution. The alumina concentration is controlled between 80g / L and 160g / L, which not only avoids the system being too diluted to cause precipitation difficulties, but also prevents the system from being too stable to be conducive to precipitation, thereby improving production efficiency and product quality.

[0081] (2) Particle size and solid content of aluminum hydroxide seed slurry: The particle size of the seed slurry is controlled between 2.5 μm and 3.5 μm, and the solid content is between 200 g / L and 300 g / L. This setting enables the seed crystals to be evenly distributed and quickly diffuse into the liquid system, thereby achieving effective control of the precipitation rate and particle size of aluminum hydroxide.

[0082] (3) Seed decomposition conditions: The precise setting of parameters such as seed decomposition temperature, time, and stirring speed ensures the orderly precipitation of aluminum hydroxide in the liquid system and avoids uneven particle size or a decrease in product quality caused by too fast or too slow precipitation speed.

[0083] 2. High quality of product

[0084] (1) Uniform particle size and good dispersibility: Through strict process parameter control and seed slurry preparation, the obtained micro-powder aluminum hydroxide has uniform particle size and good dispersibility, which can meet the high requirements of downstream customers for cable processing quality.

[0085] (2) Low oil absorption rate: The oil absorption rate of the micro-powder aluminum hydroxide prepared by this method is ≤30mL / 100g, which is much lower than the oil absorption rate of the product obtained by the traditional preparation method, which is beneficial to reducing the production cost of downstream customers and improving product quality.

[0086] (3) High loose bulk ratio: The loose bulk ratio is ≥0.5g / mL, indicating that the obtained micro-powder aluminum hydroxide has good stacking performance and fluidity, which is convenient for downstream customers to process and use.

[0087] 3. Production efficiency and cost control

[0088] (1) High production efficiency: By optimizing process parameters and preparation steps, the production cycle is shortened, the production efficiency is improved, and the production cost is reduced.

[0089] (2) Low raw material consumption: Accurate process parameter settings and efficient preparation steps reduce raw material consumption and improve raw material utilization.

[0090] (3) Low energy consumption: Reasonable setting of parameters such as stirring speed and temperature avoids unnecessary energy waste and reduces production costs.

[0091] IV. Environmental protection and sustainability

[0092] (1) Washing and drying process: The washing process uses water above 70°C and is completed after the pH value reaches 7, ensuring the purity and environmental friendliness of the product.

[0093] (2) The drying process uses a temperature of 80°C and a time of 10 hours, which not only ensures the dryness of the product but also avoids excessive energy consumption and environmental pollution.

[0094] (3) Recycling of raw materials: The raw materials used in this method, such as aluminum hydroxide and sodium hydroxide, can be recycled or recovered, reducing pollution to the environment and waste of resources.

[0095] In summary, the method for preparing low oil absorption micronized aluminum hydroxide has multiple advantages such as precise control of process parameters, high product quality, high production efficiency and low cost control, as well as environmental protection and sustainability. These advantages make this method have broad application prospects and market competitiveness in industrial production.

[0096] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are intended only to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are usually measured according to industry standards. If there is no corresponding industry standard, then the conditions recommended by the manufacturer are followed.

[0097] Example 1

[0098] Measure 1000mL of distilled water, weigh 420g of sodium hydroxide flakes, add small amounts several times to distilled water to dissolve into sodium hydroxide solution, add 585g of Bayer aluminum hydroxide, stir and dissolve on an electric furnace, and the solution αk is 1.41. Measure the dissolution solution and add distilled water to adjust the aluminum oxide concentration to 125g / L, adjust the temperature to 50°C, sand grind the seed particle size to 2.93μm, add 1%, stir and decompose for 16h, the seed solution is prepared, filter and wash to obtain the filter cake, and beat the filter cake to control the solid content to 200g / L. Measure the re-dissolved solution, adjust it to an aluminum oxide concentration of 125g / L, the solution volume is 1000mL, the temperature is 65°C, start stirring, add seeds, the addition amount is 0.8%, stir and decompose for 20 hours, wash after decomposition, wash to pH 7, move into an oven and bake at 80°C for 10 hours to obtain micro-powder aluminum hydroxide, and send samples for analysis.

[0099] Figure 2 This is a SEM image of the micro-powder aluminum hydroxide provided in Example 1 of the present application (magnification is 25000 times); Figure 3 This is a SEM image of the micro-powder aluminum hydroxide provided in Example 1 of the present application (magnification is 15000 times). Figure 2 and Figure 3 It can be seen that the micro-powder aluminum hydroxide particles prepared by this patented technology have complete crystal morphology, few agglomerated particles, and good dispersibility. The reduction of agglomerated particles is an important reason for the low oil absorption rate of micro-powder aluminum hydroxide.

[0100] Example 2

[0101] Take Bayer process semen and adjust the aluminum oxide concentration to 125 g / L, αk to 1.41, temperature to 50°C, add sand-milled seeds with a particle size of 2.93 μm in an amount of 1%, stir and decompose for 16 hours, filter and wash to obtain a filter cake, slurry the filter cake, control the solid content to 300 g / L, measure Bayer process semen, adjust to an aluminum oxide concentration of 125 g / L, temperature to 65°C, start stirring, add seeds in an amount of 0.8%, stir and decompose for 20 hours, wash after decomposition is completed, wash to a pH value of 7, move into an oven and bake at 80°C for 10 hours to obtain micro-powder aluminum hydroxide, and send samples for analysis.

[0102] According to the above two embodiments, the oil absorption rates of the samples are not much different, but there is a difference in the sodium oxide content. The sodium oxide content of the sample made from Bayer process semen is slightly higher, but it can meet the cable requirements.

[0103] Comparative Example 1

[0104] The steps are the same as those in Example 1, except that the initial seed particle size (d50) is 7.5 μm. When the initial seed grinding particle size is 7.5 μm, the decomposed seed raw material is coarse, and after fine grinding, the seed particle size is wide, the d99 particle size is coarse, and the seed decomposed micropowder has large particles (see Table 1, the same below).

[0105] Comparative Example 2

[0106] The steps are the same as those in Example 1, except that the initial seed particle size is adjusted to 1 μm. After the seed separation is completed, the samples are processed and sent for analysis according to Example 1.

[0107] Compared with Example 1, the initial seed particle size is 1 μm, the prepared seed raw material is fine, and no grinding is performed. After pulping, it is directly added to decompose. The prepared sample has a fine particle size and a high oil absorption rate.

[0108] Comparative Example 3

[0109] The decomposition steps are the same as those in Example 1, except that the concentration of the semen for seed separation is 170 g / L. After the seed separation is completed, the semen is washed, dried and analyzed according to the method of Example 1.

[0110] Compared with the embodiment, when the semen concentration is 170g / L, the sodium oxide content of the sample is too high.

[0111] Comparative Example 4

[0112] The preparation steps are the same as those in Example 1, except that the seed material preparation temperature is controlled at 75° C. After seed separation, washing, drying and sample analysis are completed according to the method of Example 1.

[0113] Compared with the embodiment, when the seed raw material preparation temperature is increased to 75°C, the prepared seed raw material is coarse, the seed particle size distribution is wide after fine grinding, and the decomposed sample has large particles.

[0114] Comparative Example 5

[0115] The preparation steps are the same as those in Example 1, except that the seed material preparation temperature is controlled at 30° C. After the seeding is completed, the processing and analysis are completed according to the method of Example 1.

[0116] Compared with the embodiment, when the seed raw material preparation temperature is controlled at 30°C, the prepared seed raw material has a high β trihydrate content of 45%, and the β content of the seed sample is 17%, which is not pure α trihydrate.

[0117] Comparative Example 6

[0118] The preparation steps are the same as those in Example 1, except that the seeding temperature is controlled at 75°C. After the seeding is completed, the processing and analysis are carried out according to the method of Example 1.

[0119] Compared with the example, the seed temperature was raised to 75°C for decomposition, the particles agglomerated, and the particle size of the sample was coarse. This is because high temperature is conducive to agglomeration and the growth rate is fast.

[0120] Comparative Example 7

[0121] The preparation steps are the same as those in Example 1, except that the seeding temperature is controlled at 50°C. After the seeding is completed, the processing and analysis are carried out according to the method of Example 1.

[0122] Compared with the embodiment, the seed temperature is controlled at 50°C for decomposition, the sample has high sodium oxide content, finer particle size, and high oil absorption rate.

[0123] Comparative Example 8

[0124] The preparation steps are the same as those in Example 1, except that the seed rate is adjusted to 0.3% during seeding. After seeding, the processing and analysis are completed according to the method of Example 1.

[0125] Compared with the embodiment, when the seeding rate is adjusted to 0.3%, the particle size of the decomposed sample is coarse and is not suitable for making cable materials.

[0126] Comparative Example 9

[0127] The preparation steps are the same as those in Example 1, except that the seed rate is adjusted to 4% during seeding. After seeding, the processing and analysis are completed according to the method of Example 1.

[0128] Compared with the embodiment, when the seed rate is adjusted to 4% during seed separation, the seed rate is too high, the decomposition speed is too fast, the secondary nucleation ratio increases, and the particle size of the sample obtained by seed separation is fine.

[0129] The parameters of the preparation methods of the micro-powder aluminum hydroxide of the examples and comparative examples are summarized, and the results are shown in Table 1.

[0130] Table 1 Parameters of the preparation method of micro powder aluminum hydroxide of the embodiment and comparative example

[0131]

[0132] The properties of the micro powder aluminum hydroxide of the embodiment and the comparative example were measured, and the results are shown in Table 2.

[0133] Table 2 Performance of micro powder aluminum hydroxide of the embodiment and comparative example

[0134] Group Oil absorption, mL / 100g Particle size, μm Bulk ratio, g / mL Example 1 28 1.253 0.54 Example 2 29 1.24 0.55 Comparative Example 1 32 1.45 0.51 Comparative Example 2 42 0.89 0.34 Comparative Example 3 32 1.25 0.49 Comparative Example 4 36 1.945 0.51 Comparative Example 5 32 1.045 0.48 Comparative Example 6 33 2.143 0.54 Comparative Example 7 34 0.935 0.35 Comparative Example 8 39 5.43 0.54 Comparative Example 9 42 0.875 0.36

[0135] It should be noted that the sodium oxide content in Comparative Example 3 is 0.24%; that in the embodiment is 0.15-0.17%; that in Comparative Example 5 is 17% in β-trihydrate; and that in Comparative Example 7 is high in sodium oxide content.

[0136] In addition, one or more technical solutions in the embodiments of the present application have at least the following technical effects or advantages:

[0137] In the embodiments of the present application, the particle size of the micro-powdered aluminum hydroxide for wires and cables is controllable, the crystal surface is fully developed, the fluidity is good, the viscosity is low, the particle size is 1.2 to 1.5 μm, and the oil absorption rate is 27 to 30 mL / 100 g. It is an excellent green flame retardant for wires and cables.

[0138] In the examples of the present application, after long-term research, production and application evaluation practice, the relationship between the viscosity, oil absorption rate and particle size of micro-powder aluminum hydroxide and the quality of cable processing by downstream customers is revealed. Through continuous research, practice and further research, the oil absorption rate is reduced to below 30mL / 100g, the particle size is 1.2μm~1.5μm, and the loose bulk ratio reaches more than 0.5g / ml, which well completes the present invention.

[0139] In an embodiment of the present application, a method for preparing micro-powder aluminum hydroxide with low oil absorption rate is provided. The preparation method can not only effectively control the particle size and dispersion of micro-powder aluminum hydroxide, but also reduce the oil absorption rate of micro-powder aluminum hydroxide, which is beneficial for downstream customers to improve the quality of processed cables.

[0140] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A method for preparing micro-powder aluminum hydroxide with low oil absorption, the method comprising: Obtaining a sodium aluminate solution having a set αk and a set alumina concentration; Obtaining an aluminum hydroxide seed slurry having a set particle size and a set solid content; The aluminum hydroxide seed slurry is added to the sodium aluminate solution to perform seed decomposition under set conditions to obtain a mixed slurry; as well as The mixed slurry is subjected to solid-liquid separation to obtain fine powder aluminum hydroxide.

2. The method according to claim 1, characterized in that The setting αk is 1.3 to 1.

6.

3. The method according to claim 1, characterized in that The sodium aluminate solution includes: aluminum hydroxide heavy solution or Bayer process semen; wherein, When the sodium aluminate solution is a heavy aluminum hydroxide solution, the αk of the heavy aluminum hydroxide solution is 1.4 to 1.6; and / or, When the sodium aluminate solution is Bayer process semen, the αk of the Bayer process semen is 1.35-1.

45.

4. The method according to claim 1, characterized in that: The set aluminum oxide concentration is 80 g / L to 160 g / L.

5. The method according to claim 1, characterized in that The set particle size is 2.5 μm to 3.5 μm.

6. The method according to claim 1, characterized in that The solid content is set to 200 g / L to 300 g / L.

7. The method according to claim 1, characterized in that The mass of the aluminum hydroxide seeds in the aluminum hydroxide seed slurry is 0.5% to 3.5% of the total mass of the sodium aluminate solution.

8. The method according to claim 1, characterized in that The setting conditions include at least one of the following: a seeding temperature of 55° C. to 70° C., a seeding time of 8 h to 24 h, and a stirring speed of 200 rpm / min to 300 rpm / min.

9. The method according to claim 1, characterized in that: The preparation method of the aluminum hydroxide seed slurry comprises: The raw materials and the solvent are pulped and ground to obtain an initial seed slurry; the raw materials include: one or more of α aluminum hydroxide trihydrate, Bayerite and diaspore, the particle size of the initial seed slurry is 1.5 μm to 4.5 μm, and the solid content of the initial seed slurry is 150 g / L to 550 g / L; The initial seed slurry is added to the sodium aluminate solution to perform seed decomposition to obtain a seed slurry; the mass of the aluminum hydroxide seeds in the initial seed slurry is 0.5% to 5.5% of the total mass of the sodium aluminate solution, the temperature of the seed decomposition is 35° C. to 75° C., the time of the seed decomposition is 8 h to 24 h, and the stirring speed of the seed decomposition is 200 rpm / min to 400 rpm / min; The seed slurry is subjected to solid-liquid separation to obtain aluminum hydroxide seeds; The aluminum hydroxide seeds and the solvent are slurried and ground to obtain the aluminum hydroxide seed slurry.

10. The method according to claim 1, characterized in that The micro-powder aluminum hydroxide meets at least one of the following properties: oil absorption rate ≤30mL / 100g, particle size of 1.2μm to 1.5μm, and loose bulk ratio ≥0.5g / mL.

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