阅读说明：本技术 一种晶面取向生长氢氧化镁的制备方法 (Preparation method of crystal face oriented growth magnesium hydroxide ) 是由 林彦军 张婧 李凯涛 于 2021-07-13 设计创作，主要内容包括：本发明公开了一种晶面取向生长氢氧化镁的制备方法。该方法首先将可溶性镁盐和取向生长剂加入去离子水中配成盐溶液；然后将盐溶液和氨水溶液同时加入成核反应器中,形成的沉淀浆液转移到晶化釜中加热晶化,最后经洗涤、过滤、干燥得到晶面取向生长的高长厚比微米级六方片状氢氧化镁。本发明基于晶体生长原理与成核晶化隔离法,使盐溶液和碱溶液在高速旋转下形成二维液膜,并在取向生长剂的作用下,形成了具有(001)晶面取向生长的晶核,然后在均一稳定环境下同步取向生长。该方法制得的氢氧化镁晶面取向生长,a,b轴方向粒径尺寸为1-4μm,长厚比为10-100微米,表面极性较小且粒径分布均匀,具有极高的产业化应用前景和价值。(The invention discloses a preparation method of crystal face oriented growth magnesium hydroxide. Firstly, adding soluble magnesium salt and an oriented growth agent into deionized water to prepare a salt solution; and then simultaneously adding the salt solution and the ammonia water solution into a nuclear reactor, transferring the formed precipitate slurry into a crystallization kettle for heating crystallization, and finally washing, filtering and drying to obtain the micron-sized hexagonal flaky magnesium hydroxide with crystal face oriented growth and high length-thickness ratio. Based on the crystal growth principle and the nucleation crystallization isolation method, the salt solution and the alkali solution form a two-dimensional liquid film under high-speed rotation, a crystal nucleus with (001) crystal face oriented growth is formed under the action of an oriented growth agent, and then synchronous oriented growth is carried out under a uniform and stable environment. The crystal face of the magnesium hydroxide prepared by the method grows in an oriented mode, the grain size in the a-axis direction and the b-axis direction is 1-4 mu m, the length-thickness ratio is 10-100 mu m, the surface polarity is small, the grain size distribution is uniform, and the method has extremely high industrial application prospect and value.)

1. A preparation method of crystal face oriented growth magnesium hydroxide is characterized by comprising the following specific operations: adding soluble magnesium salt and an oriented growth agent into deionized water to prepare a salt solution; and simultaneously adding the salt solution and the ammonia water solution into a nuclear reactor, transferring the formed precipitate slurry into a crystallization kettle for heating crystallization, and finally washing, filtering and drying to obtain the micron-sized hexagonal flaky magnesium hydroxide with crystal face oriented growth and high length-thickness ratio.

2. The preparation method according to claim 1, wherein the soluble magnesium salt is selected from one or more of magnesium chloride, magnesium nitrate and magnesium sulfate.

3. The method according to claim 1, wherein the concentration of magnesium ions in the salt solution is 0.01 to 6mol/L, and the concentration of magnesium ions and NH in the aqueous ammonia solution₃·H₂The molar ratio of O is 1: 1-6.

4. The method according to claim 1, wherein the orientation growth agent is one or more selected from ethanol, ethylene glycol, propanol, propylene glycol, glycerol, butanol, and polyethylene glycol.

5. The preparation method of claim 1, wherein the volume ratio of the orientation growth agent to the deionized water in the salt solution is 1: 0.2-4.

6. The method as claimed in claim 1, wherein the flow rate of the salt solution and the ammonia solution into the nuclear reactor is 0.1-500mL/min, and the rotation speed of the nuclear reactor is 1000-8000 rpm.

7. The method according to claim 1, wherein the temperature for thermal crystallization is 40-300 ℃ and the crystallization time is 0.5-24 hours.

Technical Field

The invention belongs to the technical field of preparation of inorganic functional materials, and particularly relates to a preparation method of flaky magnesium hydroxide with crystal face oriented growth.

Background

Magnesium hydroxide is a typical compound of a layered structure, in each unit cell, Mg²⁺At the nodal position of the hexagonal lattice origin, OH^-In three Mg²⁺The upper and lower sides of the formed triangular plane are distributed in a crossed way, and Mg²⁺Has a coordination number of 6 and two OH groups on the upper and lower sides^-. Thus, Mg (OH)₂Corresponding to two OH layers^-And a layer of Mg²⁺The three ions form a unit layer. The (101) crystal plane of magnesium hydroxide reflects an increase in the number of unit layers, and the unit layers are formed by van der waals forces and hydrogen bonds, and are crystal planes having polarity. And the (001) plane is a transverse extension of the unit layers, and the inside of each unit layer is bonded by ionic bonds, and is a non-polar plane.

Magnesium hydroxide is used as an environment-friendly material with unique physical and chemical properties, and is widely applied to the fields of wastewater, waste gas and acidic water pollutant treatment, antibiosis, new-generation inorganic flame retardants and the like. As a new generation of inorganic flame retardant material, compared with other inorganic flame retardants, magnesium hydroxide is safe and nontoxic, has stable performance, low production cost and better filling performance, can neutralize acidic and corrosive gases generated by polymer combustion, has good flame retardant effect, simultaneously has smoke abatement effect, excellent performance and wide development prospect.

Different crystal faces of magnesium hydroxide have different polarities and have great influence on the performance of the magnesium hydroxide. If the organic silicon/aluminum composite material is added into an organic polymer as an auxiliary agent such as a flame retardant, the material is easy to agglomerate due to the large surface polarity and poor surface compatibility with the polymer, so that the mechanical property of the material is reduced. Therefore, the surface polarity of the magnesium hydroxide can be controlled by regulating the oriented growth of the crystal face of the magnesium hydroxide, so that the non-polar (001) crystal face of the magnesium hydroxide can be oriented to grow, the growth of the polar (101) crystal face is inhibited, the length-diameter ratio is increased, the compatibility of the magnesium hydroxide and a polymer substrate can be improved, and the performances of flame retardance, smoke suppression and the like of the magnesium hydroxide are further improved.

Disclosure of Invention

The invention provides a preparation method of crystal face oriented growth magnesium hydroxide, which aims to improve the compatibility of the magnesium hydroxide and an organic polymer and strengthen the flame retardant and smoke suppression performance of a material. The crystal face of the magnesium hydroxide prepared by the method grows in an oriented mode, the grain size in the a-axis direction and the b-axis direction is 1-4 mu m, the length-thickness ratio is 10-100 mu m, the surface polarity is small, the grain size distribution is uniform, and the method has extremely high industrial application prospect and value.

The preparation method of crystal face oriented growth magnesium hydroxide comprises the following steps: adding soluble magnesium salt and an oriented growth agent into deionized water to prepare a salt solution; and simultaneously adding the salt solution and the ammonia water solution into a nuclear reactor, transferring the formed precipitate slurry into a crystallization kettle for heating crystallization, and finally washing, filtering and drying to obtain the micron-sized hexagonal flaky magnesium hydroxide with crystal face oriented growth and high length-thickness ratio.

The soluble magnesium salt is selected from one or more of magnesium chloride, magnesium nitrate and magnesium sulfate.

The concentration of magnesium ions in the salt solution is 0.01-6mol/L, and the concentration of the magnesium ions and NH in the ammonia water solution₃·H₂The molar ratio of O is 1: 1-6.

The orientation growth agent is selected from one or more of ethanol, ethylene glycol, propanol, propylene glycol, glycerol, butanol and polyethylene glycol.

The volume ratio of the oriented growth agent to the deionized water in the salt solution is 1: 0.2-4.

The flow rate of the salt solution and the ammonia solution added into the nuclear reactor is 0.1-500mL/min, and the rotating speed of the nuclear reactor is 1000-8000 rpm.

The temperature for heating crystallization is 40-300 ℃, and the crystallization time is 0.5-24 hours.

The beneficial results are that: based on a crystal growth principle and a nucleation crystallization isolation method, the invention utilizes a two-dimensional limited-area ultrathin nucleation reaction space between a stator and a conical rotor of a nucleation reactor to enable a salt solution and an alkali solution to form a two-dimensional liquid film under high-speed rotation, forcefully promotes the formation of crystal nuclei with (001) crystal face oriented growth and uniform particle size distribution under the action of an oriented growth agent, and then the crystal nuclei are crystallized under the same system environment to ensure synchronous oriented growth of the magnesium hydroxide crystal nuclei under a uniform and stable environment, so as to obtain the micron-sized hexagonal flaky magnesium hydroxide with high length-thickness ratio. The method takes ammonia water as a precipitator, so that the pH value of the nucleating slurry is in a medium alkaline range, the dynamic reaction balance damage caused by the magnesium hydroxide crystal nucleus in a high alkaline environment is avoided, the lattice disorder caused by the aggravation of the surface precipitation reaction is reduced, and the stability of the growth process of the magnesium hydroxide crystal nucleus is ensured. Meanwhile, under the action of an oriented growth agent, the oriented growth of the magnesium hydroxide laminate along the directions of the a axis and the b axis is effectively promoted, and a magnesium hydroxide product with micron-sized particle size, regular sheet-shaped appearance and high length-thickness ratio is obtained. The method has the advantages of convenient operation, simple process flow, low production cost, pure product, high crystallinity, regular appearance and large length-thickness ratio, and meanwhile, the method can be used for continuous production and is very suitable for large-scale production.

Drawings

FIG. 1 is an XRD spectrum of crystal plane-oriented magnesium hydroxide prepared in example 1;

FIG. 2 is an SEM photograph of a crystal-plane-oriented magnesium hydroxide prepared in example 1;

FIG. 3 is a laser particle size distribution diagram of crystal-plane-oriented magnesium hydroxide obtained in example 3.

Detailed Description

Example 1:

weighing 30.50g of magnesium chloride hexahydrate and 2.5mL of absolute ethyl alcohol serving as oriented growth agents, and adding deionized water to prepare 75mL of salt solution; 30.65g of ammonia water with the mass concentration of 25% is added into deionized water to be diluted to obtain 75mL of ammonia water solution. The two solutions enter a nuclear reactor simultaneously at the same flow of 100mL/min through a peristaltic pump, the rotating speed of the nuclear reactor is 3000 r/min, and formed precipitation slurry flows out of the reactor from a discharge hole at the bottom of the nuclear reactor. And crystallizing the slurry obtained by the reaction in a crystallization kettle at 120 ℃ for 6 hours, and filtering, washing and drying to obtain the micron-sized magnesium hydroxide. Ratio I of diffraction peak intensities of (001) crystal face and (101) crystal face of product₀₀₁/I₁₀₁1.527, the nonpolar (001) crystal plane preferentially grows, and the particle size distribution D₅₀1.391 μm, D₉₀2.747 μm.

The product is characterized by the crystal structure by adopting an XRD-6000X-ray powder diffractometer of Shimadzu corporation in Japan, an XRD pattern is shown as figure 1, the comparison with a standard spectrogram of magnesium hydroxide proves that the product is magnesium hydroxide, and the ratio I of the diffraction peak intensities of the crystal face (001) and the crystal face (101) of the product₀₀₁/I₁₀₁Growth of a nonpolar (001) crystal plane was promoted as 1.527. The crystal grain size and morphology were observed by scanning electron microscope of model supra55 from ZEISS, Germany. FIG. 2 is an SEM photograph, and it can be seen from the figure that the prepared magnesium hydroxide product is in a hexagonal plate structure, the particle size is between 0.81 and 2.1 μm, and the distribution is uniform.

Example 2:

121.98g of magnesium chloride hexahydrate and 60mL of absolute ethyl alcohol are weighed as oriented growth agents and added into deionized water to prepare 300mL of salt solution; 81.74g of ammonia water with a mass concentration of 25% was added to deionized water to dilute the solution to obtain 300mL of ammonia water solution. The two solutions were passed through a nuclear reactor at the same flow rate and reactor rotation speed as in example 1. And adding the slurry obtained by nucleation into a crystallization kettle, crystallizing for 6 hours at 160 ℃, and filtering, washing and drying to obtain the micron-sized hexagonal flaky magnesium hydroxide. The product has the ratio I of the diffraction peak intensities of the (001) crystal face and the (101) crystal face₀₀₁/I₁₀₁1.608, the nonpolar (001) crystal plane preferentially grows, and the particle size distribution D₅₀1.134 μm, D₉₀It was 2.123. mu.m.

Example 3:

weighing 20.33g of magnesium chloride hexahydrate and 10mL of oriented growth agent glycerol, and adding deionized water to prepare 50mL of salt solution; 27.25g of ammonia water with a mass concentration of 25% was diluted with deionized water to obtain 50mL of an ammonia water solution. The flow rate of the two solutions through the nuclear reactor and the rotational speed of the reactor were the same as in example 1. Crystallizing the obtained slurry in a crystallization kettle at 80 ℃ for 6 hours, filtering, washing and drying to obtain the micron-sized hexagonal flaky magnesium hydroxide.

The product particle size distribution is tested by adopting a British Malvern 2000 laser particle size analyzer, the nonpolar (001) crystal face of the product preferentially grows, and the particle size distribution D₅₀3.726 μm, D₉₀6.902 μm.

Example 4:

weighing 20.33g of magnesium chloride hexahydrate and 10mL of polyethylene glycol serving as oriented growth agents, and adding deionized water to prepare 50mL of salt solution; 27.25g of ammonia water with a mass concentration of 25% was diluted with deionized water to obtain 50mL of an ammonia water solution. The flow rate of the two solutions through the nuclear reactor and the rotational speed of the reactor were the same as in example 1. Crystallizing the obtained slurry in a crystallization kettle at 200 deg.C for 6 hr, filtering, washing, and drying to obtainMicron-sized hexagonal flaky magnesium hydroxide. The nonpolar (001) crystal face of the product preferentially grows, I₀₀₁/I₁₀₁1.220, particle size distribution D₅₀1.840 μm, D₉₀It was 3.178. mu.m.

The present invention has been described in detail, and it should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.