Preparation method of nanoscale aluminum hydroxide micro powder

Abstract

The invention belongs to the technical field of preparation of metal hydroxides, and particularly relates to a preparation method of nanoscale aluminum hydroxide micro powder. Comprising the following steps: (1) dispersing aluminum salt, glucose and long-chain alkyl quaternary ammonium salt in deionized water to prepare an aluminum salt mixed solution; (2) dropwise adding alkali liquor into the aluminum salt mixed solution; (3) reacting for a period of time, and adding the long-chain alkyl quaternary ammonium salt again for reacting; and (4) filtering, washing and drying to obtain the nanoscale aluminum hydroxide micro powder. Glucose not only plays a role of a template agent in the early stage of precipitation, but also reduces the particle size of precipitated particles. By adding the long-chain alkyl quaternary ammonium salt step by step, dispersion of the precipitate can be better promoted, and secondary agglomeration of the separated precipitate is prevented. The method is simple in process, the aluminum hydroxide micro powder is small in particle size, controllable in particle size and low in industrialization cost, and the current efficient, economical and environment-friendly requirements are met.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal hydroxide preparation, and particularly relates to a method for preparing nano-sized aluminum hydroxide micropowder. Background Art

[0002] As an important inorganic flame retardant, aluminum hydroxide has three major functions: flame retardancy, smoke elimination, and filling. It is chemically inert, non-toxic, and does not cause secondary pollution. It not only has a high whiteness value but also excellent chromaticity indexes; it has good dispersibility in resins, and when a relatively large amount is added, it is not easy to occur bending and whitening phenomena; it can produce a synergistic flame retardant effect with a variety of substances, and has a good flame retardant effect; it is rich in sources and low in price. It has always been the flame retardant with the largest consumption of inorganic flame retardants (accounting for 70% of the total amount of inorganic flame retardants), and also the one with the largest usage amount of flame retardants, accounting for about 40% of the total usage amount of flame retardants. It is widely used in various plastics, coatings, polyurethanes, elastomers, and rubber products.

[0003] Among various hydrates of aluminum, aluminum hydroxide has the largest heat absorption, which is beneficial to the formation of a char layer, so the flame retardant effect is also the best. Limited by the flame retardant mechanism, its flame retardant efficiency is poor, and a particularly high addition amount is required to endow the flame-retarded material with ideal flame retardant properties, and the flame retardant effect increases with the increase of the addition amount. However, too large a filling amount will inevitably deteriorate the physical and mechanical properties and processing properties of the polymer matrix.

[0004] Based on the above advantages and disadvantages of aluminum hydroxide flame retardants, exploring new types of aluminum hydroxide flame retardants to give full play to their flame retardant advantages and improve deficiencies has attracted more and more attention. The main improvement method is to reduce the particle size and prepare ultrafine or nano-sized aluminum hydroxide, which is not only beneficial to the uniform dispersion in the flame-retarded polymer matrix but also helps to improve the negative impact on the physical and mechanical properties of the substrate. Due to the small particle size and large specific surface area of nano-sized aluminum hydroxide, it has unique surface effects, quantum size effects, small size effects, and macroscopic quantum tunneling effects, etc. These characteristics have correspondingly caused huge changes in the physical and chemical properties of nano-sized aluminum hydroxide. Compared with conventional aluminum hydroxide, when nano-sized aluminum hydroxide is filled, at a relatively high dosage, it will not only not reduce the mechanical properties of the material but also play a plasticizing and strengthening role of rigid particles; it can also increase the contact area between the inorganic flame retardant and the polymer, enhance the interaction ability between the two, and improve the compatibility between the two. Moreover, the specific surface area of nano-sized aluminum hydroxide is greatly increased, which reduces the water vapor partial pressure on the particle surface and can improve the flame retardant effect to a certain extent. In addition, the thermal decomposition temperature of nano-sized aluminum hydroxide is higher than that of ordinary aluminum hydroxide, and it has better heat resistance. It can be used for polymers with higher processing temperatures and has a better flame retardant effect.

[0005] As a flame retardant and filler, nano-aluminum hydroxide can be widely used in rubber and plastics; as a main flame retardant additive in flame retardant coatings and decorative materials in homes and cars; forming organic / inorganic nano-composites with polymer materials, making it also have good applications in fields such as information, communication, microelectronics, biochemistry, environment, medicine, aviation, and aerospace. With the development of emerging materials science and the gradual improvement and increasing strictness of environmental protection and flame retardant regulations in various countries, the demand for nano-aluminum hydroxide will be increasing, and it has broad market prospects. Summary of the Invention

[0006] To solve the technical problems of the complex preparation process and high cost of nano-aluminum hydroxide in the prior art, the present invention provides a method for preparing nano-scale aluminum hydroxide micropowder. This method has a simple process, the particle size of the aluminum hydroxide micropowder is small, the particle size is controllable, and the industrial cost is low, meeting the requirements of high efficiency, economy, and environmental protection today.

[0007] To solve the above technical problems, the present invention adopts the following technical solutions: A method for preparing nano-scale aluminum hydroxide micropowder, comprising the following steps: (1) Disperse a certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt in deionized water to obtain an aluminum salt mixed solution, and the mass ratio of glucose to aluminum salt is (0.1 - 0.5):1; (2) While stirring, dropwise add an alkali solution to the aluminum salt mixed solution, and stop dropping after adjusting the solution pH to 5 - 6; (3) Then continue stirring and reacting for 0.5 - 1.2 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.5 - 2 h; (4) After filtration, washing, and drying, nano-scale aluminum hydroxide micropowder is obtained.

[0008] In previous work, the inventors used polyethylene glycol polymers with a specific molecular weight as surfactants to prepare aluminum hydroxide micropowders. However, this process was relatively complex, with harsh process conditions, requiring strict control of process parameters, poor product reproducibility, and low qualification rates. To reduce the particle size of aluminum hydroxide micropowders, glucose and long-chain alkyl quaternary ammonium salts were added to the aluminum salt solution in the present invention. Compared with the prior art of adding high-molecular surfactants to the aluminum salt solution to improve the dispersion of precipitation, low-molecular glucose was selected as an additive in the present invention. Glucose is a cyclic small molecule, and its structure contains multiple hydroxyl groups, which will generate strong interaction forces (such as hydrogen bonds, van der Waals forces, etc.) with the aluminum salt and the initial precipitate formed. The presence of glucose not only acts as a template agent in the initial stage of precipitation, but also produces a steric hindrance effect, hindering the growth of particles, controlling the precipitation rate, and reducing the particle size of the precipitated particles. Generally speaking, as the amount of the template agent increases, the particle size will decrease to some extent; however, too much template agent will lead to the generation of a large amount of precipitation in a short period, and moreover, due to the existence of many hydrogen bonds in the glucose structure, it will not have time to disperse, forming agglomerated particles, which is not conducive to the preparation of nano-aluminum hydroxide micropowders.

[0009] Meanwhile, to prevent the precipitated particles from aggregating into large particles with each other, a certain amount of long-chain alkyl quaternary ammonium salt dispersant was added at the initial stage of precipitation. The long-chain alkyl quaternary ammonium salt dispersant has both a hydrophilic ammonium salt end and a hydrophobic long straight carbon chain alkyl end. The addition of the long-chain alkyl quaternary ammonium salt dispersant can reduce the interfacial tension at the gas-liquid interface, change the surface properties of the initial aluminum hydroxide particles, increase the steric hindrance, and prevent the aggregation of aluminum hydroxide particles with each other during the precipitation process. After the precipitation reaction for a certain period of time, the aluminum hydroxide particles in the solution gradually increase. To prevent the secondary aggregation of aluminum hydroxide particles, a certain amount of long-chain alkyl quaternary ammonium salt was added again. The purpose is to reduce the interaction force between particles through adsorption, thereby controlling the aggregation degree of aluminum hydroxide particles during the generation and precipitation process.

[0010] In the above scheme, in step (1), the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is (0.001 - 0.006):1.

[0011] In the above scheme, in step (1), the aluminum salt is one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.

[0012] In the above scheme, in step (1), the long-chain alkyl quaternary ammonium salt is one or more of dodecyl trimethyl ammonium bromide, cetyl trimethyl ammonium bromide, or octadecyl trimethyl ammonium bromide. As a kind of cationic surfactant, the long-chain alkyl quaternary ammonium salt will ionize when dissolved in water, promoting the dispersion of particles. In particular, cetyl trimethyl ammonium bromide was selected as the dispersant, which has good chemical stability and good penetration effect, further promoting the dispersion of precipitation.

[0013] In the above solution, in step (1), the dispersion adopts an ultrasonic process with an ultrasonic power of 100 - 200 W; the concentration of aluminum salt in the aluminum salt mixed solution is 0.4 - 0.8 mol / L.

[0014] In the above solution, in step (2), the stirring rate is 250 - 550 rpm, and the temperature during stirring is 45 - 60 °C. The intense vibration and shearing action generated by stirring can better promote the dispersion of particles and prevent agglomeration between particles.

[0015] In the above solution, in step (2), the dropping rate of the alkali solution is 20 - 35 mL / min, and the concentration of the alkali solution is 4 - 10 wt%.

[0016] In the above solution, the alkali solution in step (2) is one or more of an ammonia water solution and a urea solution. Using an ammonia water solution or a urea solution as a precipitating agent, the precipitating agent can be uniformly released through its uniform decomposition in the solution, contact uniformly with aluminum ions, and promote the formation of aluminum hydroxide micropowder with a small particle size.

[0017] In the above solution, the mass ratio of the long-chain alkyl quaternary ammonium salt and the aluminum salt added again in step (3) is (0.006 - 0.02):1. Adding the long-chain alkyl quaternary ammonium salt step by step can better promote the dispersion of the precipitate and prevent secondary agglomeration of the precipitated precipitate. Since there is a large amount of precipitate in step (3), the dosage of the long-chain alkyl quaternary ammonium salt in step (3) is greater than that in step (1). In particular, the mass ratio of the long-chain alkyl quaternary ammonium salt and the aluminum salt added again in step (3) is 0.009 - 0.015. An appropriate amount of the long-chain alkyl quaternary ammonium salt can not only avoid the negative effects brought by the hydrophobicity or entanglement of long-chain alkyls, but also promote the dispersion of particles and prevent secondary agglomeration of particles.

[0018] In the above solution, the reaction temperature in step (3) is 55 - 70 °C. By adjusting the timing of adding the long-chain alkyl quaternary ammonium salt, as well as the reaction temperature and time, it is possible to promote the dispersion of the precipitate and prevent the particle size from growing too large. Further, by stirring and reacting for 0.6 - 1 h and then adding the long-chain alkyl quaternary ammonium salt again for reaction for 1.5 - 2 h, aluminum hydroxide micropowder with a uniform particle size can be prepared. There are no special requirements for the washing and drying processes in the above solution, and usually ethanol or deionized water can be used for washing.

[0019] Beneficial effects: In the present invention, a precipitate is obtained by adding an appropriate precipitant to an aluminum salt solution, and then the precipitate is filtered, washed, and dried to obtain nano-sized aluminum hydroxide micropowder. The presence of glucose not only acts as a template agent in the initial stage of precipitation, but also has a steric hindrance effect, hindering the growth of particles, controlling the precipitation rate, and reducing the particle size of the precipitated particles. At the same time, a certain amount of long-chain alkyl quaternary ammonium salt dispersant is added at the initial stage of precipitation. The long-chain alkyl quaternary ammonium salt dispersant has both a hydrophilic ammonium salt end and a hydrophobic long-chain alkyl end. The addition of the long-chain alkyl quaternary ammonium salt dispersant can reduce the interfacial tension at the gas-liquid interface, change the surface properties of the initial particles, increase the steric hindrance, and prevent the agglomeration of particles during the precipitation process. After the precipitation reaction for a certain period of time, a certain amount of long-chain alkyl quaternary ammonium salt is added again, aiming to reduce the interaction force between particles through adsorption, thereby controlling the degree of agglomeration of particles during the generation and precipitation process. This method has a simple process, the aluminum hydroxide micropowder has a small particle size, the particle size is controllable, the industrial cost is low, meets the requirements of high efficiency, economy, and environmental protection today, and can be used as an efficient flame retardant material in the fields of aviation, aerospace, etc. Specific embodiments

[0020] The present invention is further illustrated by the following examples: According to the following examples, the present invention can be better understood. However, those skilled in the art can easily understand that the specific material ratios, process conditions, and their results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0021] Example 1 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt are dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is 0.1:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is 0.006:1; the aluminum salt is aluminum sulfate; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the dispersion adopts an ultrasonic process, and the ultrasonic power is 100 W; the concentration of the aluminum salt in the aluminum salt mixed solution is 0.5 mol / L; (2) While stirring, an alkali solution is added dropwise to the aluminum salt mixed solution, and the addition of the alkali solution is stopped after adjusting the pH of the solution to 5; the stirring rate is 300 rpm, and the temperature during stirring is 47 °C; the dropping rate of the alkali solution is 20 mL / min, and the concentration of the alkali solution is 5 wt%; the alkali solution is an ammonia water solution; (3) Then, continue to stir and react for 0.5 h, and then add long-chain alkyl quaternary ammonium salt again and react for 2 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.009:1; the reaction temperature is 55 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder is obtained.

[0022] Example 2 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) Dispersing a certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt in deionized water to obtain an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is 0.003:1; the aluminum salt is aluminum sulfate; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the dispersion adopts an ultrasonic process with an ultrasonic power of 160 W; the concentration of the aluminum salt in the aluminum salt mixed solution is 0.6 mol / L; (2) While stirring, dropwise add an alkali solution to the aluminum salt mixed solution, and stop adding after adjusting the solution pH to 5.4; the stirring rate is 420 rpm, the temperature during stirring is 54 °C; the dropping rate of the alkali solution is 24 mL / min, and the concentration of the alkali solution is 6 wt%; the alkali solution is an ammonia water solution; (3) Then continue stirring and reacting for 1.2 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.012:1; the reaction temperature is 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder is obtained.

[0023] Example 3 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) Dispersing a certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt in deionized water to obtain an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is 0.5:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is 0.001:1; the aluminum salt is aluminum sulfate; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the dispersion adopts an ultrasonic process with an ultrasonic power of 200 W; the concentration of the aluminum salt in the aluminum salt mixed solution is 0.8 mol / L; (2) While stirring, dropwise add an alkali solution to the aluminum salt mixed solution, and stop adding after adjusting the solution pH to 6; the stirring rate is 500 rpm, the temperature during stirring is 60 °C; the dropping rate of the alkali solution is 30 mL / min, and the concentration of the alkali solution is 8 wt%; the alkali solution is an ammonia water solution; (3) Then continue stirring and reacting for 1 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.5 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.015:1; the reaction temperature is 65 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder is obtained.

[0024] Example 4 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt are dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is 0.003:1; the aluminum salt is aluminum sulfate; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the dispersion adopts an ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution is 0.6 mol / L; (2) While stirring, an alkali solution is added dropwise to the aluminum salt mixed solution, and the addition is stopped after adjusting the pH of the solution to 5.4; the stirring rate is 420 rpm, and the temperature during stirring is 54 °C; the dropping rate of the alkali solution is 24 mL / min, and the concentration of the alkali solution is 6 wt%; the alkali solution is an ammonia water solution; (3) Then, continue stirring and reacting for 0.8 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.006:1; the reaction temperature is 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder is obtained.

[0025] Example 5 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt are dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is 0.2:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt is 0.005:1; the aluminum salt is aluminum sulfate; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; the dispersion adopts an ultrasonic process with an ultrasonic power of 120 W; the concentration of aluminum salt in the aluminum salt mixed solution is 0.6 mol / L; (2) While stirring, an alkali solution is added dropwise to the aluminum salt mixed solution, and the addition is stopped after adjusting the pH of the solution to 5.2; the stirring rate is 350 rpm, and the temperature during stirring is 50 °C; the dropping rate of the alkali solution is 22 mL / min, and the concentration of the alkali solution is 6 wt%; the alkali solution is an ammonia water solution; (3) Then, continue stirring and reacting for 0.6 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.9 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.014:1; the reaction temperature is 57 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder is obtained.

[0026] Example 6 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.003:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the solution pH to 5.4; the stirring rate was 420 rpm, and the temperature during stirring was 54 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.8 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.02:1; the reaction temperature was 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder was obtained.

[0027] Example 7 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.4:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.002:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 180 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.7 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the solution pH to 5.8; the stirring rate was 450 rpm, and the temperature during stirring was 57 °C; the dropping rate of the alkali solution was 28 mL / min, and the concentration of the alkali solution was 7 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.8 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.014:1; the reaction temperature was 63 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder was obtained.

[0028] Example 8 A method for preparing nano-sized aluminum hydroxide micropowder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.012:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the pH of the solution to 5.4; the stirring rate was 420 rpm, and the temperature during stirring was 54 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.8 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.003:1; the reaction temperature was 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0029] Example 9 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.003:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 170 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the pH of the solution to 5.8; the stirring rate was 410 rpm, and the temperature during stirring was 53 °C; the dropping rate of the alkali solution was 23 mL / min, and the concentration of the alkali solution was 7 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.6 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.6 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.011:1; the reaction temperature was 59 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0030] Example 10 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.4:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.004:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 140 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.8 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution. After adjusting the pH of the solution to 5.4, the addition was stopped; the stirring rate was 460 rpm, and the temperature during stirring was 57 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.8 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.6 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.01:1; the reaction temperature was 63 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0031] Example 11 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.003:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution. After adjusting the pH of the solution to 5.4, the addition was stopped; the stirring rate was 420 rpm, and the temperature during stirring was 54 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, after continuing to stir and react for 0.8 h, long-chain alkyl quaternary ammonium salt was added again and reacted for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.012:1; the reaction temperature was 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0032] Comparative Example 1 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.8:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.003:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the solution pH to 5.4; the stirring rate was 420 rpm, and the temperature during stirring was 54 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, stirring and reacting continued for 0.8 h, and then the long-chain alkyl quaternary ammonium salt was added again and reacted for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt was 0.012:1; the reaction temperature was 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0033] Comparative Example 2 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the mass ratio of long-chain alkyl quaternary ammonium salt to aluminum salt was 0.015:1; the aluminum salt was aluminum sulfate; the long-chain alkyl quaternary ammonium salt was cetyltrimethylammonium bromide; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, an alkali solution was added dropwise to the aluminum salt mixed solution, and the addition was stopped after adjusting the solution pH to 5.4; the stirring rate was 420 rpm, and the temperature during stirring was 54 °C; the dropping rate of the alkali solution was 24 mL / min, and the concentration of the alkali solution was 6 wt%; the alkali solution was ammonia water; (3) Then, stirring and reacting continued for 2.6 h; the reaction temperature was 60 °C; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide fine powder was obtained.

[0034] Comparative Example 3 A method for preparing nano-sized aluminum hydroxide fine powder, comprising the following steps: (1) A certain amount of aluminum salt and glucose were dispersed in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt was 0.3:1; the aluminum salt was aluminum sulfate; the dispersion was carried out by ultrasonic process with an ultrasonic power of 160 W; the concentration of aluminum salt in the aluminum salt mixed solution was 0.6 mol / L; (2) While stirring, add the alkali solution dropwise to the aluminum salt mixed solution, and stop adding after adjusting the solution pH to 5.4; the stirring rate is 420 rpm, and the temperature during stirring is 54 °C; the dropping rate of the alkali solution is 24 mL / min, and the concentration of the alkali solution is 6 wt%; the alkali solution is ammonia water solution; (3) Then continue stirring and reacting for 0.8 h, and then add the long-chain alkyl quaternary ammonium salt and react for 1.8 h; the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is 0.015:1; the reaction temperature is 60 °C; the long-chain alkyl quaternary ammonium salt is cetyltrimethylammonium bromide; (4) After filtration, washing, and drying, nano-sized aluminum hydroxide micropowder is obtained.

[0035] The median particle size D50 of the nano-sized aluminum hydroxide micropowder prepared in the above examples and comparative examples was tested, and the results are shown in Tables 1 and 2.

[0036] Table 1 Table 2 It can be seen from Tables 1 and 2 that in the present invention, precipitation is obtained by adding an appropriate precipitant to the aluminum salt solution, and then nano-sized aluminum hydroxide micropowder is obtained through filtration, washing, and drying. This method has a simple process, the aluminum hydroxide micropowder has a small particle size, the particle size is controllable, and the industrial cost is low, meeting the requirements of high efficiency, economy, and environmental protection today.

[0037] Compared with Example 11, in Comparative Example 1, the dosage of glucose is too much, which is extremely likely to cause the agglomeration of the precipitate and the increase in particle size. This is because too much glucose dosage will lead to the generation of a large amount of precipitate in a short period of time. Due to the existence of many hydrogen bonds in the glucose structure, it will not have time to disperse, forming agglomerated particles, which is not conducive to the preparation of nano-sized aluminum hydroxide micropowder. At the same time, compared with Example 11, in Comparative Examples 2-3, the long-chain alkyl quaternary ammonium salt dispersant is not added step by step, and it cannot effectively promote the dispersion of primary particles and secondary particles. As a result, not only does agglomeration occur between particles during the precipitation process, but it also causes difficulties in the dispersion of particles during the generation and precipitation process.

[0038] Finally, it should be noted that the above examples of the present invention are only examples for explaining the present invention, and are not intended to limit the embodiments of the present invention. For those of ordinary skill in the art, other different forms of changes and modifications can be made on the basis of the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A method for preparing nano-sized aluminum hydroxide micropowder, characterized in that, It includes the following steps: (1) Disperse a certain amount of aluminum salt, glucose, and long-chain alkyl quaternary ammonium salt in deionized water to prepare an aluminum salt mixed solution. The mass ratio of glucose to aluminum salt is (0.1 - 0.5):1; (2) While stirring, dropwise add an alkali solution to the aluminum salt mixed solution, and stop adding after adjusting the pH of the solution to 5 - 6; (3) Then continue stirring and reacting for 0.5 - 1.2 h, and then add the long-chain alkyl quaternary ammonium salt again and react for 1.5 - 2 h; (4) After filtration, washing, and drying, nano-scale aluminum hydroxide fine powder is obtained.

2. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, In step (1), the mass ratio of the long-chain alkyl quaternary ammonium salt to the aluminum salt is (0.001 - 0.006):

1.

3. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The aluminum salt in step (1) is one or more of aluminum nitrate, aluminum sulfate, and aluminum chloride.

4. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The long-chain alkyl quaternary ammonium salt in step (1) is one or more of dodecyl trimethyl ammonium bromide, cetyl trimethyl ammonium bromide, and octadecyl trimethyl ammonium bromide.

5. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The dispersion in step (1) adopts an ultrasonic process, and the ultrasonic power is 100 - 200 W; the concentration of the aluminum salt in the aluminum salt mixed solution is 0.4 - 0.8 mol / L.

6. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The stirring rate in step (2) is 250 - 550 rpm, and the temperature during stirring is 45 - 60 °C.

7. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The dropping rate of the alkali solution in step (2) is 20 - 35 mL / min, and the concentration of the alkali solution is 4 - 10 wt%.

8. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The alkali solution in step (2) is one or more of ammonia water solution and urea solution.

9. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, In step (3), the mass ratio of the long-chain alkyl quaternary ammonium salt added again to the aluminum salt is (0.006 - 0.02):

1.

10. The method for preparing nano-sized aluminum hydroxide micropowder according to claim 1, characterized in that, The reaction temperature in step (3) is 55 - 70 °C.

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