Method for preparing hexagonal flaky magnesium hydroxide by hydration modification one-step method

Abstract

The invention relates to a method for preparing hexagonal flaky magnesium hydroxide through a hydration modification one-step method, and belongs to the technical field of inorganic material preparation. Hyperbranched sodium polyacrylate containing phosphonic acid and ammonium phosphonate salt is synthesized and serves as a crystal forming agent for magnesium hydroxide crystal growth, the hyperbranched sodium polyacrylate can coordinate with magnesium ions, uniform growth of all crystal faces of the magnesium hydroxide crystal is promoted, and the magnesium hydroxide crystal growth rate is increased. And the hyperbranched structure can better and moderately wrap the formed magnesium hydroxide crystal, so that the uniform growth property of the crystal face is improved. In addition, ammonium phosphate groups and carboxylate in the crystal forming agent have good wetting dispersity, agglomeration of magnesium hydroxide crystals is weakened, and the particle size distribution uniformity is improved. According to the method, the magnesium oxide powder and the crystal forming agent are ground and then subjected to the hydration reaction, the hexagonal flaky magnesium hydroxide is synthesized through a one-step method, and the prepared magnesium hydroxide is in a regular hexagonal flaky shape, has uniform particle size distribution, and has relatively high purity and relatively low impurity content.

Description

Technical Field

[0001] The invention relates to a method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification method, belonging to the technical field of inorganic material preparation. Background Art

[0002] Magnesium hydroxide is an important inorganic magnesium compound, and its main use is as a flame retardant for plastic products. As a flame retardant material, magnesium hydroxide has the following advantages: (1) The decomposition temperature of magnesium hydroxide is high, and its ignition point is higher than that of aluminum hydroxide, which can effectively increase the heating temperature of polymer materials; (2) MgO generated after the combustion and dehydration of magnesium hydroxide is a refractory material and an alkaline oxide that can absorb acidic gases; (3) Magnesium hydroxide has a strong heat absorption capacity and high flame retardant efficiency; (4) It is low in cost and easy to process in different polymer materials. However, the morphology of magnesium hydroxide synthesized by conventional methods is irregular and easy to agglomerate. When mixed with polymer materials, it has poor dispersibility and compatibility, resulting in its low flame retardant efficiency. Therefore, it is usually necessary to add a large amount of magnesium hydroxide to achieve the desired flame retardant effect, but high concentrations of magnesium hydroxide will damage the mechanical properties of the material. In order to obtain magnesium hydroxide with good dispersibility, regular morphology, and uniform particle size distribution, a hydrothermal treatment method is usually used.

[0003] Chinese patent document CN118084026A discloses a micron-sized hexagonal flaky magnesium hydroxide and its preparation method and application. The preparation method comprises the following steps: calcining brucite to obtain light-burned magnesium oxide; mixing light-burned magnesium oxide with water to obtain a magnesium oxide suspension; adjusting the pH of the magnesium oxide suspension to 6 to 8 with a pH regulator and filtering to obtain a magnesium chloride solution; the pH regulator is hydrochloric acid and ammonia water; mixing the magnesium chloride solution, sodium hydroxide solution and dispersant and performing a hydrothermal reaction at a temperature of 130°C to 190°C for 2h to 10h to obtain a reaction product; cooling, filtering, washing and drying the reaction product to obtain a high-quality micron-sized hexagonal flaky magnesium hydroxide with regular morphology, uniform particle size and high purity. The patent document needs to first obtain magnesium chloride by reacting light-burned magnesium oxide with a pH regulator, and then make magnesium chloride into hexagonal flaky magnesium hydroxide. The reaction process is cumbersome, the cost is high, and it is not conducive to industrial production.

[0004] Chinese patent document CN106673027A discloses a preparation and synthesis method of a hexagonal flaky magnesium hydroxide flame retardant, the steps of which are: adding a magnesium salt solution and a crystallization directing agent to a reaction vessel, stirring evenly at 30-50°C, dropping an inorganic alkali solution into the reaction vessel at a constant rate at the temperature, and after the reaction is complete, the reaction slurry is subjected to ultrasonic oscillation for 20-30 minutes and then transferred to a high-pressure reactor, anhydrous ethanol is added, and a hydrothermal reaction is carried out at a temperature of 180-200°C, and the reaction time is 24-48 hours. Finally, the magnesium hydroxide product is obtained by filter pressing, water washing, alcohol washing, and drying. Although the patent document obtains hexagonal flaky magnesium hydroxide by a one-step method, its particle size distribution is too wide, the purity is low, and the impurity content is high. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification method, so as to solve the problems of uneven particle size distribution, low purity and high impurity content of the prepared magnesium hydroxide in the current preparation of hexagonal flaky magnesium hydroxide.

[0006] The invention provides a method for preparing hexagonal flaky magnesium hydroxide by a hydration modification one-step method. The method comprises the following steps: grinding magnesium oxide powder and a crystal forming agent and then carrying out a hydration reaction with water to obtain hexagonal flaky magnesium hydroxide; the preparation method of the crystal forming agent is as follows: carrying out a polymerization reaction on sodium acrylate, allylphosphonic acid monoammonium salt and propane trimethylol triacrylate in a mass ratio of 100:2-2.5:1.2-1.5 to obtain hyperbranched sodium polyacrylate with a molecular weight of 3000-4500, which is the crystal forming agent.

[0007] Preferably, isopropanol as a molecular weight regulator is added during the polymerization reaction.

[0008] Preferably, the mass of the isopropyl alcohol is 2-3% of the mass of the sodium acrylate.

[0009] Preferably, the initiator used in the polymerization reaction is azobisisobutyronitrile.

[0010] Preferably, the mass of azobisisobutyronitrile is 1-2% of the mass of sodium acrylate.

[0011] Preferably, the polymerization reaction temperature is 50-65° C. and the time is 2-3 hours.

[0012] Preferably, the mass ratio of the magnesium oxide powder, the crystal forming agent and water is 6-8:6-7.5:75-90.

[0013] Preferably, the average particle size of the magnesium oxide powder is 10-30 μm.

[0014] Preferably, the temperature of the hydration reaction is 70-100°C.

[0015] Preferably, the hydration reaction time is 5 to 8 hours.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) In the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step of the present invention, a hyperbranched sodium polyacrylate containing phosphonic acid and ammonium phosphonate is synthesized and used as a crystal forming agent for the growth of magnesium hydroxide crystals. The hyperbranched sodium polyacrylate can coordinate with magnesium ions to promote the uniform growth of each crystal face of the magnesium hydroxide crystal, and its hyperbranched structure can better and appropriately wrap the formed magnesium hydroxide crystals, thereby improving the uniform growth of its crystal face. In addition, the ammonium phosphonate group and carboxylate in the crystal forming agent have good wetting and dispersibility, weaken the agglomeration of magnesium hydroxide crystals, and improve the uniformity of particle size distribution. The crystal forming agent can reduce the precipitation and adhesion speed of magnesium hydroxide crystals by wrapping the formed magnesium hydroxide crystals through its hyperbranched large steric hindrance structure and the magnesium hydroxide crystals formed by wetting and dispersing the ammonium phosphonate group and carboxylate, thereby improving the uniformity of the particle size distribution and compactness of the magnesium hydroxide crystals, thereby reducing the oil absorption value of the magnesium hydroxide crystals, and preventing impurity ions in the liquid phase from entering the formed magnesium hydroxide crystals, thereby improving the purity of the hexagonal flaky magnesium hydroxide and reducing the impurity content.

[0017] (2) The ammonium phosphonate group, carboxylate and hyperbranched structure in the crystal forming agent of the present invention can cooperate with each other to play a synergistic role, and jointly improve the hexagonal plate regularity, purity and uniformity of particle size distribution of magnesium hydroxide, and reduce its oil absorption value and impurity content. When the molecular weight of the crystal forming agent is too large, its physical entanglement effect is enhanced, the disorder degree is increased, and the magnesium hydroxide crystals will be unevenly wrapped, interfering with their uniform growth, resulting in poor uniformity of particle size dispersion; when the molecular weight of the crystal forming agent is too small, its branched chain is short and cannot wrap the magnesium hydroxide crystals well, and its steric hindrance is reduced, resulting in uneven crystal growth, unable to form a regular hexagonal plate structure, and high impurity content.

[0018] (3) The present invention introduces a polymer segment containing both an ammonium phosphonate group and a carboxylic acid structure, which can utilize the surface activity of the ammonium phosphonate group on the one hand, and the affinity between the carboxylic acid group and magnesium hydroxide on the other hand, and the two work together to improve the shape regularity, particle size distribution uniformity and purity of magnesium hydroxide. Compared with diethyl allylphosphonate, due to its increased hydrophobicity, the affinity of the crystal forming agent with the hydrophilic magnesium hydroxide crystals becomes poorer, and it cannot better interact with the magnesium hydroxide crystals, which leads to a decrease in its purity, a decrease in the uniformity of the particle size distribution, and an increase in the oil absorption value and impurity content. Compared with allylphosphonic acid, due to the lack of ammonium phosphonate groups in its molecular structure, its surface activity is reduced, and it cannot better interact with the magnesium hydroxide crystals, which leads to a decrease in its purity, a decrease in the uniformity of the particle size distribution, and an increase in the oil absorption value and impurity content.

[0019] (4) The present invention grinds magnesium oxide powder and a crystal forming agent and then conducts a hydration reaction to synthesize hexagonal flaky magnesium hydroxide in one step. The prepared magnesium hydroxide is in the form of regular hexagonal flaky ... BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the H NMR spectrum of the crystal forming agent prepared in Example 1. DETAILED DESCRIPTION

[0021] The following examples are intended to further illustrate the present invention rather than to limit the scope of protection of the present invention.

[0022] The main component of the light-burned magnesium oxide used in the examples and comparative examples of the present invention is magnesium oxide (MgO), and it also contains a small amount of impurities such as aluminum oxide, calcium oxide, iron oxide, silicon dioxide, caustic soda, etc. The purity of sodium acrylate, allylphosphonic acid monoammonium salt, propane trimethanol triacrylate, allylphosphonic acid diethyl ester, allylphosphonic acid, isopropanol and dioxane are all analytically pure, and their purity does not affect the purity of the final magnesium hydroxide product.

[0023] Example 1

[0024] The method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification method of this embodiment comprises the following steps: 6 g of light-burned magnesium oxide powder (average particle size of 10 μm) and 6 g of a crystal forming agent are ground evenly and placed in a polytetrafluoroethylene reactor, then 75 g of water is added, stirred evenly, heated to 70° C., stirred for 5 h, cooled to room temperature, filtered, washed, and dried to obtain hexagonal flaky magnesium hydroxide.

[0025] The preparation method of the crystal forming agent is as follows: sodium acrylate, allylphosphonic acid monoammonium salt, propane trimethylol triacrylate and dioxane in a mass ratio of 100:2:1.2:150 are added to a stirring tank, and then isopropanol as a molecular weight regulator (the mass of isopropanol is 2% of the mass of sodium acrylate) is added, stirred evenly, heated to 50°C, and then azobisisobutyronitrile (the mass of azobisisobutyronitrile is 1% of the mass of sodium acrylate) is added, stirred for 2 hours, and the solvent is removed by reduced pressure distillation to obtain hyperbranched sodium polyacrylate (after gel permeation chromatography detection, the molecular weight of hyperbranched sodium polyacrylate is 4500), which is the crystal forming agent, and its nuclear magnetic hydrogen spectrum is as shown in Figure 1 shown.

[0026] Among them, the structure of sodium acrylate is as follows: ; The structure of allylphosphonic acid monoammonium salt is as follows: ; The structure of propane trimethylol triacrylate is as follows: .

[0027] Example 2

[0028] The method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification method of this embodiment comprises the following steps: 7 g of light-burned magnesium oxide powder (average particle size of 20 μm) and 7 g of a crystal forming agent are ground evenly and placed in a polytetrafluoroethylene reactor, then 80 g of water is added, stirred evenly, heated to 85° C., stirred for 6 hours, cooled to room temperature, filtered, washed, and dried to obtain hexagonal flaky magnesium hydroxide.

[0029] The preparation method of the crystal forming agent is as follows: sodium acrylate, allylphosphonic acid monoammonium salt, propane trimethylol triacrylate and dioxane in a mass ratio of 100:2.2:1.4:180 are added to a stirring tank, and then isopropanol as a molecular weight regulator is added (the mass of isopropanol is 2.5% of the mass of sodium acrylate), stirred evenly, heated to 60°C, and then azobisisobutyronitrile is added (the mass of azobisisobutyronitrile is 1.5% of the mass of sodium acrylate), stirred for reaction for 2.5 hours, and the solvent is removed by reduced pressure distillation to obtain hyperbranched sodium polyacrylate (after gel permeation chromatography detection, the molecular weight of hyperbranched sodium polyacrylate is 3800), which is the crystal forming agent.

[0030] Example 3

[0031] The method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification method of this embodiment comprises the following steps: 8 g of light-burned magnesium oxide powder (average particle size of 30 μm) and 7.5 g of a crystal forming agent are ground evenly and placed in a polytetrafluoroethylene reactor, then 90 g of water is added, stirred evenly, heated to 100° C., stirred for 8 h, cooled to room temperature, filtered, washed, and dried to obtain hexagonal flaky magnesium hydroxide.

[0032] The preparation method of the crystal forming agent is as follows: sodium acrylate, allylphosphonic acid monoammonium salt, propane trimethylol triacrylate and dioxane in a mass ratio of 100:2.5:1.5:200 are added to a stirring kettle, and then isopropanol as a molecular weight regulator (the mass of isopropanol is 3% of the mass of sodium acrylate) is added, stirred evenly, heated to 65°C, and then azobisisobutyronitrile (the mass of azobisisobutyronitrile is 2% of the mass of sodium acrylate) is added, stirred for 3 hours, and the solvent is removed by reduced pressure distillation to obtain hyperbranched sodium polyacrylate (after gel permeation chromatography detection, the molecular weight of hyperbranched sodium polyacrylate is 3000), which is the crystal forming agent.

[0033] Comparative Example 1 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, the amount of allylphosphonic acid monoammonium salt used in preparing the crystal forming agent is 0.

[0034] Comparative Example 2 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, the amount of propane trimethylol triacrylate used in preparing the crystal forming agent is 0.

[0035] Comparative Example 3 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, the mass of isopropyl alcohol, a molecular weight regulator, is 0.5% of the mass of sodium acrylate when preparing the crystal forming agent.

[0036] Comparative Example 4 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, the mass of the molecular weight regulator isopropanol is 8% of the mass of sodium acrylate when preparing the crystal forming agent.

[0037] Comparative Example 5 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, allylphosphonic acid monoammonium salt is replaced by allylphosphonic acid.

[0038] Comparative Example 6 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step in this comparative example, allylphosphonic acid monoammonium salt is replaced by allylphosphonic acid diethyl ester.

[0039] Comparative Example 7 The difference between the method for preparing hexagonal flaky magnesium hydroxide by hydration modification one-step method in this comparative example and the method for preparing hexagonal flaky magnesium hydroxide by hydration modification one-step method in Example 1 is that in the method for preparing hexagonal flaky magnesium hydroxide by hydration modification one-step method in this comparative example, the grinding step is omitted, and the light-burned magnesium oxide powder, the crystal forming agent and water are directly added to the polytetrafluoroethylene reactor at one time, stirred evenly, heated to 125° C., stirred for 5 hours, cooled to room temperature, filtered, washed, and dried to obtain hexagonal flaky magnesium hydroxide.

[0040] Experimental example In order to evaluate the comprehensive performance of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example, and to preliminarily judge its prospect in the field of flame retardants, the particle size distribution of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example was tested by a laser particle size analyzer to obtain the D10, D50, and D90 particle sizes of the hexagonal flaky magnesium hydroxide; the hexagonal flaky regularity of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example was tested by a scanning electron microscope; the oil absorption value of the hexagonal flaky magnesium hydroxide was tested by dioctyl phthalate, and the oil absorption value is equal to the ratio of the oil absorption of the hexagonal flaky magnesium hydroxide to the mass of the hexagonal flaky magnesium hydroxide. Finally, the purity and impurity ion content of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example were tested.

[0041] The particle size distribution, oil absorption value and appearance test results of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example are shown in Table 1. The purity and impurity ion content of the hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example are shown in Table 2.

[0042] Table 1 Hexagonal sheets prepared in various embodiments and comparative examples Particle size distribution, oil absorption value and appearance test results of magnesium hydroxide

[0043] Table 2 Purity and impurity ion content of hexagonal flaky magnesium hydroxide prepared in each embodiment and comparative example

[0044] It can be seen from Table 1-2 that the magnesium hydroxide prepared by the present invention is in the shape of regular hexagonal flakes, has a uniform particle size distribution, a low oil absorption value, and has a high purity and a low impurity content.

[0045] In the method for preparing hexagonal flaky magnesium hydroxide by hydration modification one-step method of the present invention, hyperbranched sodium polyacrylate containing phosphonic acid and ammonium phosphonate is synthesized and used as a crystal forming agent for the growth of magnesium hydroxide crystals. Hyperbranched sodium polyacrylate can coordinate with magnesium ions to promote the uniform growth of each crystal face of magnesium hydroxide crystals, and its hyperbranched structure can better and appropriately wrap the formed magnesium hydroxide crystals, thereby improving the uniform growth of its crystal face. Moreover, the ammonium phosphonate group and carboxylate in the crystal forming agent have good wetting and dispersibility, weaken the agglomeration of magnesium hydroxide crystals, and improve the uniformity of particle size distribution. The crystal forming agent wraps the formed magnesium hydroxide crystals through its hyperbranched large steric hindrance structure and the magnesium hydroxide crystals formed by the wetting and dispersion of the ammonium phosphonate group and carboxylate, which can reduce the precipitation and adhesion speed of the magnesium hydroxide crystals, improve the uniformity and compactness of the magnesium hydroxide crystal size distribution, thereby reducing the oil absorption value of the magnesium hydroxide crystals, and can prevent the impurity ions in the liquid phase from entering the formed magnesium hydroxide crystals, thereby improving the purity of the hexagonal flaky magnesium hydroxide and reducing the impurity content.

[0046] As can be seen from Example 1 and Comparative Examples 1-2, the ammonium phosphonate group, carboxylate and hyperbranched structure in the crystal forming agent can cooperate with each other to play a synergistic role, and jointly improve the hexagonal sheet regularity, purity and particle size distribution uniformity of magnesium hydroxide, and reduce its oil absorption value and impurity content. As can be seen from Example 1 and Comparative Examples 3-4, when the amount of molecular weight regulator is changed, the molecular weight of the hyperbranched sodium polyacrylate is too large or too small. When the molecular weight of the hyperbranched sodium polyacrylate is too large, the physical entanglement of the crystal forming agent is enhanced, the disorder degree is increased, and the magnesium hydroxide crystals are unevenly wrapped, interfering with their uniform growth, resulting in poor particle size dispersion uniformity; when the molecular weight of the hyperbranched sodium polyacrylate is too small, the branched chain of the crystal forming agent is short, and the magnesium hydroxide crystals cannot be well wrapped, and its steric hindrance is reduced, resulting in uneven crystal growth, and a regular hexagonal sheet structure cannot be formed, and the impurity content is high. As shown in Example 1 and Comparative Example 5, when allylphosphonic acid monoammonium salt is replaced by allylphosphonic acid, due to lack of ammonium phosphonate group in molecular structure, surface activity is reduced, and it is impossible to better react with magnesium hydroxide crystals, thereby causing its purity to decrease, particle size distribution uniformity to deteriorate, and oil absorption value and impurity content to increase. As shown in Example 1 and Comparative Example 6, when allylphosphonic acid monoammonium salt is replaced by allylphosphonic acid diethyl ester, due to its hydrophobicity increase, the affinity of crystal forming agent and hydrophilic magnesium hydroxide crystals is deteriorated, and it is impossible to better react with magnesium hydroxide crystals, thereby causing its purity to decrease, particle size distribution uniformity to deteriorate, and oil absorption value and impurity content to increase. As shown in Example 1 and Comparative Example 7, after omitting the grinding step, due to lack of close combination between crystal forming agent and raw material, it is impossible to better coordinate with magnesium ion, thereby causing the uniformity growth of each crystal face of magnesium hydroxide crystal to deteriorate, affecting its purity and impurity content.

Claims

1. A method for preparing hexagonal flaky magnesium hydroxide by a one-step hydration modification process, characterized in that: The method comprises the following steps: grinding magnesium oxide powder and a crystal forming agent and then carrying out hydration reaction with water to obtain hexagonal flaky magnesium hydroxide; the preparation method of the crystal forming agent is as follows: carrying out polymerization reaction on sodium acrylate, allylphosphonic acid monoammonium salt and propane trimethylol triacrylate in a mass ratio of 100:2-2.5:1.2-1.5 to obtain hyperbranched sodium polyacrylate with a molecular weight of 3000-4500, which is the crystal forming agent.

2. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: Isopropanol is added as a molecular weight regulator during the polymerization reaction.

3. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step as claimed in claim 2, characterized in that: The mass of the isopropyl alcohol is 2-3% of the mass of the sodium acrylate.

4. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: The initiator used in the polymerization reaction is azobisisobutyronitrile.

5. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step as claimed in claim 4, characterized in that: The mass of azobisisobutyronitrile is 1~2% of the mass of sodium acrylate.

6. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step as claimed in claim 4, characterized in that: The polymerization reaction temperature is 50-65° C. and the reaction time is 2-3 hours.

7. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: The mass ratio of the magnesium oxide powder, the crystal forming agent and water is 6-8:6-7.5:75-90.

8. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: The average particle size of magnesium oxide powder is 10~30μm.

9. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: The temperature of the hydration reaction is 70-100°C.

10. The method for preparing hexagonal flaky magnesium hydroxide by hydration modification in one step according to claim 1, characterized in that: The hydration reaction time is 5 to 8 hours.

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