Preparation method of nano magnesium hydroxide
Through the homogeneous precipitation method of coordination reaction between ionic liquid and magnesium source, the problem of poor dispersion of nanomagnesium hydroxide under small size conditions was solved, and nanomagnesium hydroxide with uniform particle size was prepared, achieving good dispersion in polymer and mechanical properties simplify process flow and reduce costs.
Patent Information
- Application Number
- CN202411593924.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-08
- Publication Date
- 2025-01-07
AI Technical Summary
The existing nanomagnesium hydroxide has poor dispersion under small size conditions, resulting in a decrease in the mechanical properties of the polymer and making it difficult to disperse uniformly in the organic matrix.
Nanomagnesium hydroxide is prepared by homogeneous precipitation method by coordinating the acrylic anions and glycine anions in the ionic liquid to coordinate with magnesium ions, control particle size and particle size distribution, prevent particle aggregation, and realize nanometers Uniform dispersion of magnesium hydroxide.
The prepared nanomagnesium hydroxide has a uniform particle size, a diameter of 60~150nm, a thickness of 10~15nm, and a good dispersion. It can maintain good mechanical properties in the polymer, and the process is simple and does not require high-temperature hydrothermal synthesis.
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Figure CN119263317A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of magnesium compounds, and in particular to a method for preparing nano magnesium hydroxide. Background Art
[0002] As an important inorganic halogen-free smoke suppression flame retardant, magnesium hydroxide has better thermal stability, smoke suppression performance and flame retardancy than other inorganic flame retardants, even compared with aluminum trihydroxide, and magnesium hydroxide is an environmentally friendly additive. Therefore, magnesium hydroxide has been widely used in halogen-free flame retardant (HFFR) polymer materials. However, in order to achieve better flame retardancy, the addition level of magnesium hydroxide needs to reach 60 wt%, which will lead to a serious deterioration of the mechanical properties of the polymer. Using micro-nanostructured magnesium hydroxide as a flame retardant in polymer materials is a way to solve these problems.
[0003] Nano magnesium hydroxide produced under conventional conditions has a wide particle size distribution, strong surface polarity, and is easy to agglomerate into secondary particles. When used as a flame retardant, it is difficult to disperse in an organic matrix, which will still lead to a decrease in the mechanical properties of the polymer. Therefore, nano magnesium hydroxide used as a flame retardant requires uniform particle size and good dispersibility.
[0004] On September 20, 2010, Cao et al. disclosed in the article "Mg(OH)2 Composite Nanostructures with Superhydrophobicity and Flame Retardancy" a method for synthesizing flower-like nano-magnesium hydroxide by self-assembly through hydrothermal synthesis. After adding a mixed solution of glycine and sodium hydroxide solution to a MgCl2∙6H2O aqueous solution, the mixture was hydrothermally reacted at 240°C for 48 hours. After the reaction was completed, the product was collected, washed and dried to obtain flower-like nano-magnesium hydroxide. The synthesized Mg(OH)2 nanostructure was dispersed in acrylonitrile-butadiene-styrene (ABS) copolymer. Without destroying the mechanical properties of the ABS composite material, it has all the characteristics required for ABS flame-retardant fillers and shows excellent flame retardant properties.
[0005] However, the nano magnesium hydroxide prepared by the above hydrothermal synthesis method cannot maintain good dispersibility within a smaller size range. Summary of the invention
[0006] The invention provides a method for preparing nano magnesium hydroxide, which solves the problem that the existing nano magnesium hydroxide has poor dispersibility under the condition of small size.
[0007] In order to solve the above technical problems, the technical solution of the method for preparing nano magnesium hydroxide of the present invention is: A method for preparing nano magnesium hydroxide comprises the following steps: mixing an ionic liquid and a magnesium source to prepare a complex solution, adding a hydroxide to the complex solution for homogeneous precipitation reaction to obtain a suspension, filtering, washing and drying the suspension to obtain nano magnesium hydroxide, wherein the ionic liquid is selected from one of 1-butyl-3-methylimidazole acrylate, 1-butyl-3-methylimidazole glycine and N-methylimidazole acrylate.
[0008] The invention is an improvement on the prior art, and provides a method for preparing nano magnesium hydroxide. The method comprises the following steps: introducing an ionic liquid to react with a magnesium source for coordination, and then reacting with a hydroxide for homogeneous precipitation to obtain a suspension. Acrylic acid anions and glycine anions in the ionic liquid are more easily coordinated with metals, thereby playing a role in controlling the release of magnesium ions and spatial barrier, and effectively dispersing nano magnesium hydroxide particles. The ionic liquid is used as a multi-effect regulating agent, and the nano magnesium hydroxide is prepared by in-situ modification using a homogeneous reaction method by using the ionic liquid. The reaction crystallization is regulated by the coordination reaction of the ionic liquid, the hydrogen bonding effect, and the electrostatic effect, so that the particle size and particle size distribution of the magnesium hydroxide can be controlled. The obtained flaky nano magnesium hydroxide has uniform particle size, the diameter of the flaky nano magnesium hydroxide is 60-150nm, the thickness of the flaky nano magnesium hydroxide is 10-15nm, and the cationic groups in the ionic liquid can further prevent the aggregation between nano magnesium hydroxide particles. The preparation method provided by the invention has a simple process, and can obtain flaky nano magnesium hydroxide with uniform particle size distribution and small size without the need for hydrothermal synthesis at a high temperature. In addition, N-methylimidazole-type and 1-butyl-3-methylimidazole-type ionic liquids are easy to synthesize, and the synthesis cost and price are relatively low.
[0009] In order to further complete the homogeneous reaction, preferably, the molar ratio of the ionic liquid, the magnesium ions in the magnesium source and the hydroxide ions in the hydroxide is (0.1-2): (2-2.5): (2-6.5).
[0010] In order to further improve the precipitation efficiency of the homogeneous reaction, preferably, the temperature of the homogeneous precipitation reaction is 25-60° C., and the time of the homogeneous precipitation reaction is 1-2 h.
[0011] In order to further improve the coordination reaction efficiency and thus improve the particle size uniformity of magnesium hydroxide synthesis, preferably, the complex solution is obtained by dropping the ionic liquid aqueous solution into the magnesium source aqueous solution and then stirring, the dropping speed of the ionic liquid aqueous solution is 3~4ml / min, the concentration of the ionic liquid aqueous solution is 0.02~0.4mol / L, and the concentration of magnesium ions in the magnesium source aqueous solution is 0.4~0.5mol / L.
[0012] In order to further improve the uniformity of magnesium hydroxide precipitation in the homogeneous precipitation reaction, preferably, the suspension is obtained by dropwise adding a hydroxide aqueous solution into a complex solution for a homogeneous precipitation reaction, the dropping speed of the hydroxide aqueous solution is 6-7 ml / min, and the concentration of hydroxide ions in the hydroxide aqueous solution is 0.2-0.65 mol / L.
[0013] In order not to destroy the micro-nano structure of nano-magnesium hydroxide, preferably, the drying temperature is 50-60°C.
[0014] In order to further improve the reaction efficiency, preferably, the magnesium source is selected from one of magnesium sulfate, magnesium chloride and magnesium nitrate, and the hydroxide is selected from one of sodium hydroxide and potassium hydroxide.
[0015] Preferably, the nano magnesium hydroxide is flaky nano magnesium hydroxide.
[0016] Preferably, the diameter of the flaky nano magnesium hydroxide is 60-150 nm and the thickness is 10-15 nm. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Figure 1 This is a flow chart of the method for preparing nano magnesium hydroxide according to Example 1 of the present invention; Figure 2 The XRD spectrum of nano magnesium hydroxide prepared in Example 1 of the present invention; Figure 3 This is a SEM morphology image of nano magnesium hydroxide prepared in Example 1 of the present invention; Figure 4 The XRD spectrum of nano magnesium hydroxide prepared in Example 2 of the present invention; Figure 5 This is a SEM morphology image of nano magnesium hydroxide prepared in Example 2 of the present invention; Figure 6 The XRD spectrum of nano magnesium hydroxide prepared in Example 3 of the present invention; Figure 7 This is a SEM morphology image of nano magnesium hydroxide prepared in Example 3 of the present invention; Figure 8 The XRD spectrum of nano magnesium hydroxide prepared in Comparative Example 1 of the present invention; Fig. 9 This is a SEM morphology image of nano magnesium hydroxide prepared in Comparative Example 1 of the present invention.
[0018] Fig.10 This is a comparison chart of the free sedimentation experiment of nano-magnesium hydroxide dispersion. DETAILED DESCRIPTION
[0019] The technical conception of the method for preparing nano magnesium hydroxide of the present invention is as follows: A method for preparing nano magnesium hydroxide comprises the following steps: mixing an ionic liquid and a magnesium source to prepare a complex solution, adding a hydroxide to the complex solution for homogeneous precipitation reaction to obtain a suspension, filtering, washing and drying the suspension to obtain nano magnesium hydroxide, wherein the ionic liquid is selected from one of 1-butyl-3-methylimidazole acrylate, 1-butyl-3-methylimidazole glycine and N-methylimidazole acrylate.
[0020] The preparation methods of nano magnesium hydroxide mainly include direct precipitation method and homogeneous precipitation method. The nano magnesium hydroxide prepared by direct precipitation method has the following problems: ① wide particle size distribution; ② poor dispersibility, while the homogeneous precipitation method can produce uniform nano magnesium hydroxide. The homogeneous precipitation method uses additional chemical substances and chemical reactions to slowly release the crystallizing ions from the solution, and by controlling the concentration of the generated crystallizing ions, the precipitation reaction is kept in a state of equilibrium, so that the precipitate is uniformly precipitated in the solution, and finally nanoparticles with uniform particle size are obtained.
[0021] In the prior art, different contents of glutamic acid are introduced into the homogeneous precipitation reaction mainly to adjust the morphology of the precipitated precipitate. As the content of glutamic acid increases, the nano magnesium hydroxide changes from a plate shape to a flower shape. However, in the present invention, an ionic liquid is introduced, and acrylic acid anions and glycine anions in the ionic liquid first react with magnesium ions to obtain a uniform and stable complex solution, and then react with magnesium hydroxide to undergo a homogeneous precipitation reaction. Through the ionic liquid coordination reaction, hydrogen bonding action, and electrostatic action to regulate the reaction crystallization, the particle size and particle size distribution of the magnesium hydroxide can be controlled, and the formation of nano magnesium hydroxide of smaller size can be induced, and aggregation between nano magnesium hydroxide particles can be prevented, thereby improving the dispersibility.
[0022] The structural formulas of the three ionic liquids are as follows: Among them, a is 1-butyl-3-methylimidazolium acrylate; b is 1-butyl-3-methylimidazolium glycine; and c is N-methylimidazolium acrylate.
[0023] In a specific embodiment, the ionic liquid aqueous solution, the magnesium source aqueous solution and the hydroxide aqueous solution are obtained by dissolving the ionic liquid, the magnesium source and the hydroxide in water, respectively.
[0024] In a specific embodiment, the ionic liquid aqueous solution is added dropwise to the magnesium source aqueous solution and then stirred to obtain a complex solution at a stirring speed of 400-600 r / min.
[0025] In a specific embodiment, the hydroxide aqueous solution is added dropwise to the complex solution under stirring conditions, and after the addition is completed, the homogeneous precipitation reaction is continued for 1 to 1.6 hours to obtain a suspension, and the stirring speed is 400 to 600 r / min. It can be understood that the homogeneous precipitation reaction time refers to the sum of the time when the hydroxide aqueous solution is added dropwise to the complex solution and the time when the homogeneous precipitation reaction is continued.
[0026] In a specific embodiment, the magnesium source is magnesium sulfate heptahydrate.
[0027] The implementation manner of the present invention is further described below in conjunction with specific examples.
[0028] 1. Specific embodiment of the method for preparing nano magnesium hydroxide of the present invention Example 1 The process flow chart of the preparation method of nano magnesium hydroxide in this embodiment is as follows Figure 1 As shown, the specific preparation method is as follows: At room temperature, magnesium sulfate heptahydrate, sodium hydroxide and 1-butyl-3-methylimidazole acrylate were weighed respectively, and the three were dissolved in water to obtain magnesium sulfate heptahydrate aqueous solution, sodium hydroxide aqueous solution and 1-butyl-3-methylimidazole acrylate aqueous solution, and the volumes were fixed to 50 ml, 100 ml and 50 ml respectively, and the concentrations of the three aqueous solutions were controlled to be 0.4 mol / L, 0.5 mol / L and 0.02 mol / L respectively.
[0029] The 1-butyl-3-methylimidazole acrylate aqueous solution was slowly and uniformly added to the magnesium sulfate heptahydrate aqueous solution, the dropping time was controlled to be 15 minutes, and the solution was stirred evenly after the addition to form a uniform complex solution at a stirring speed of 400 r / min; the complex solution was transferred to a three-necked flask preheated in a 50°C constant temperature water bath, heated and stirred to make the solution temperature uniform, and the sodium hydroxide aqueous solution was also placed in a 50°C water bath for preheating. After preheating, the sodium hydroxide aqueous solution was dropped into the three-necked flask, and the stirring was continued. The dropping time was controlled to be 15 minutes, and the stirring speed was 400 r / min. After the dropping was completed, the homogeneous precipitation reaction was continued at the same temperature for 1.6 hours to obtain a suspension, and the suspension was filtered, washed, and dried to obtain nano magnesium hydroxide, which was recorded as product 1.
[0030] The XRD pattern of product 1 is as follows Figure 2 As shown, compared with the standard spectrum of magnesium hydroxide (PDF#44-1482), it can be seen that the diffraction peak of the product obtained in this example is consistent with magnesium hydroxide, proving that product 1 is a magnesium hydroxide crystal form, and the peak width of product 1 is larger and the particle size is smaller. The SEM morphology of product 1 is shown in Figure 3 As shown, from Figure 3It can be seen that product 1 is irregular flake-shaped with uniform particle size distribution, a diameter of 60-120 nm, and a thickness of about 15 nm.
[0031] Example 2 The nano magnesium hydroxide preparation method of the present embodiment is as follows: At room temperature, magnesium sulfate heptahydrate, sodium hydroxide and 1-butyl-3-methylimidazolyl glycinate were weighed respectively, and the three were dissolved in water to obtain magnesium sulfate heptahydrate aqueous solution, sodium hydroxide aqueous solution and 1-butyl-3-methylimidazolyl glycinate aqueous solution, and the volumes were fixed to 50 ml, 100 ml and 50 ml respectively, and the concentrations of the three aqueous solutions were controlled to be 0.5 mol / L, 0.625 mol / L and 0.04 mol / L, respectively.
[0032] The 1-butyl-3-methylimidazolium glycine salt aqueous solution is slowly and uniformly added to the magnesium sulfate heptahydrate aqueous solution, the dropping time is controlled to be 15 minutes, and the solution is stirred evenly after the addition to form a uniform complex solution at a stirring speed of 400 r / min; the complex solution is transferred to a three-necked flask preheated in a 60°C constant temperature water bath, heated and stirred to make the solution temperature uniform, and the sodium hydroxide aqueous solution is also placed in a 60°C water bath for preheating. After preheating, the sodium hydroxide aqueous solution is dropped into the three-necked flask, and the stirring is continued. The dropping time is controlled to be 15 minutes, and the stirring speed is 400 r / min. After the dropwise addition is completed, the homogeneous precipitation reaction is continued at the same temperature for 1.0 hours to obtain a suspension, and the suspension is filtered, washed, and dried to obtain nano magnesium hydroxide, which is recorded as product 2.
[0033] The XRD pattern of product 2 is as follows Figure 4 As shown, compared with the standard spectrum of magnesium hydroxide (PDF#44-1482), it can be seen that the diffraction peak of the product obtained in this example is consistent with magnesium hydroxide, proving that product 2 is a magnesium hydroxide crystal form, and the peak width of product 2 is larger and the particle size is smaller. The SEM morphology of product 2 is shown in Figure 5 As shown, from Figure 5 It can be seen that product 2 is irregular flake-shaped with uniform particle size distribution, a diameter of 60-100 nm, and a thickness of about 10 nm.
[0034] Example 3 The nano magnesium hydroxide preparation method of the present embodiment is as follows: At room temperature, magnesium sulfate heptahydrate, sodium hydroxide and N-methylimidazole acrylate were weighed respectively, and dissolved in water to obtain magnesium sulfate heptahydrate aqueous solution, sodium hydroxide aqueous solution and N-methylimidazole acrylate aqueous solution, and the volumes were fixed to 50 ml, 100 ml and 50 ml respectively, and the concentrations of the three aqueous solutions were controlled to be 0.4 mol / L, 0.6 mol / L and 0.4 mol / L respectively.
[0035] The N-methylimidazole acrylate aqueous solution was slowly and uniformly added to the magnesium sulfate heptahydrate aqueous solution, the dropping time was controlled to be 15 minutes, and the solution was stirred evenly after the addition to form a uniform complex solution at a stirring speed of 400 r / min; the complex solution was transferred to a three-necked flask preheated in a 25°C constant temperature water bath, heated and stirred to make the solution temperature uniform, and the sodium hydroxide aqueous solution was also placed in a 25°C water bath for preheating. After preheating, the sodium hydroxide aqueous solution was dropped into the three-necked flask, and the stirring was continued. The dropping time was controlled to be 15 minutes, and the stirring speed was 400 r / min. After the dropping was completed, the homogeneous precipitation reaction was continued at the same temperature for 1.0 hours to obtain a suspension, and the suspension was filtered, washed, and dried to obtain nano magnesium hydroxide, which was recorded as product 3.
[0036] The XRD pattern of product 3 is as follows Figure 6 As shown, compared with the standard spectrum of magnesium hydroxide (PDF#44-1482), it can be seen that the diffraction peak of the product obtained in this example is consistent with magnesium hydroxide, proving that product 3 is a magnesium hydroxide crystal form, and the peak width of product 3 is larger and the particle size is slightly smaller. The SEM morphology of product 3 is shown in Figure 7 As shown, from Figure 7 It can be seen that product 3 is in the shape of a clustered rosette with uniform particle size distribution, a diameter of 90-150 nm, and a thickness of about 10 nm.
[0037] 2. Comparison Comparative Example 1 The preparation method of nano magnesium hydroxide in this comparative example does not involve ionic liquid, and the specific method is as follows: At room temperature, magnesium sulfate heptahydrate and sodium hydroxide were weighed separately, and the two were dissolved in water to obtain magnesium sulfate heptahydrate aqueous solution and sodium hydroxide aqueous solution, and the volumes were fixed to 50 ml and 100 ml respectively, and the concentrations of the two aqueous solutions were controlled to be 0.4 mol / L and 0.5 mol / L respectively.
[0038] The magnesium sulfate heptahydrate aqueous solution was placed in a three-necked flask preheated in a constant temperature water bath at 25°C, and heated and stirred to make the solution temperature uniform at a stirring speed of 400r / min. At the same time, the sodium hydroxide aqueous solution was also placed in a 25°C water bath for preheating. After preheating, the sodium hydroxide aqueous solution was dropwise added to the three-necked flask with continuous stirring. The dropping time was controlled to be 15min and the stirring speed was 400r / min. After the dropwise addition was completed, the homogeneous precipitation reaction was continued at the same temperature for 1.0h to obtain a suspension. The suspension was filtered, washed, and dried to obtain nano-magnesium hydroxide, which was recorded as product 4.
[0039] The XRD pattern of product 4 is as follows Figure 8As shown, compared with the standard spectrum of magnesium hydroxide (PDF#44-1482), it can be seen that the diffraction peak of the product obtained in this example is consistent with magnesium hydroxide, proving that product 4 is a magnesium hydroxide crystal form. The SEM morphology of product 4 is shown in Fig. 9 As shown, from Fig. 9 It can be seen that the product 4 nano magnesium hydroxide MH is agglomerated to a greater extent, forming irregular flakes with a diameter of 200-300 nm and a thickness of about 20 nm. The size is significantly increased, and the size uniformity becomes worse.
[0040] 3. Experimental Examples This experimental example uses a free sedimentation test to evaluate the dispersibility of nano magnesium hydroxide in water. The specific method is: disperse the nano magnesium hydroxide (white powder) prepared in the embodiment and the comparative example in water to obtain a dispersion, and compare the sedimentation performance. The sedimentation performance test results of the four nano magnesium hydroxide water dispersions are shown in the figure. Fig.10 As shown (background is black). Fig.10 It can be seen that the product 4 nano-magnesium hydroxide MH which has not been regulated by ionic liquid and has been subjected to ultrasound will quickly settle in water within 1 minute, and the dispersion is extremely unstable. The aqueous dispersion formed by the nano-magnesium hydroxide (product 1-3) prepared by the present invention is in a suspension state and has no obvious change within 1 minute, indicating that the introduction of ionic liquid in the preparation process of nano-magnesium hydroxide has a significant effect on improving the stability of the nano-magnesium hydroxide dispersion.
[0041] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.
Claims
1. A method for preparing nano magnesium hydroxide, characterized in that: The following steps are involved: An ionic liquid and a magnesium source are mixed to prepare a complex solution, a hydroxide is added to the complex solution for a homogeneous precipitation reaction to obtain a suspension, and the suspension is filtered, washed and dried to obtain nano magnesium hydroxide, wherein the ionic liquid is selected from one of 1-butyl-3-methylimidazole acrylate, 1-butyl-3-methylimidazole glycine and N-methylimidazole acrylate.
2. The method for preparing nano magnesium hydroxide according to claim 1, wherein The molar ratio of the ionic liquid, the magnesium ions in the magnesium source and the hydroxide ions in the hydroxide is (0.1-2): (2-2.5): (2-6.5).
3. The method for preparing nano magnesium hydroxide according to claim 1, wherein The temperature of the homogeneous precipitation reaction is 25-60° C., and the time of the homogeneous precipitation reaction is 1-2 hours.
4. The method for preparing nano magnesium hydroxide according to claim 1, wherein The complex solution is obtained by dropping an ionic liquid aqueous solution into a magnesium source aqueous solution and then stirring, the dropping speed of the ionic liquid aqueous solution is 3-4 ml / min, the concentration of the ionic liquid aqueous solution is 0.02-0.4 mol / L, and the concentration of magnesium ions in the magnesium source aqueous solution is 0.4-0.5 mol / L.
5. The method for preparing nano magnesium hydroxide according to claim 4, wherein: The suspension is obtained by dropping a hydroxide aqueous solution into a complex solution for homogeneous precipitation reaction. The dropping speed of the hydroxide aqueous solution is 6-7 ml / min, and the concentration of hydroxide ions in the hydroxide aqueous solution is 0.2-0.65 mol / L.
6. The method for preparing nano magnesium hydroxide according to claim 5, wherein: The drying temperature is 50-60°C.
7. The method for preparing nano magnesium hydroxide according to any one of claims 1 to 6, wherein: The magnesium source is selected from one of magnesium sulfate, magnesium chloride and magnesium nitrate, and the hydroxide is selected from one of sodium hydroxide and potassium hydroxide.
8. The method for preparing nano magnesium hydroxide according to claim 1, wherein The nano magnesium hydroxide is flaky nano magnesium hydroxide.
9. The method for preparing nano magnesium hydroxide according to claim 8, wherein: The diameter of the flaky nano magnesium hydroxide is 60-150 nm, and the thickness is 10-15 nm.