Nanometer hexagonal flaky magnesium hydroxide flame retardant and preparation method thereof

Abstract

The invention belongs to the technical field of inorganic flame retardants, and discloses a nano hexagonal flaky magnesium hydroxide flame retardant and a preparation method thereof. Comprising the following steps: respectively preparing a soluble magnesium salt solution and a precipitant aqueous solution, respectively carrying out preheating treatment, respectively and continuously conveying and mixing to obtain a mixed solution, carrying out ultrasonic treatment and reaction to obtain magnesium hydroxide nano slurry, and carrying out ultrasonic dispersion, filtration and drying to obtain the nano hexagonal flaky magnesium hydroxide. Controllable preparation of the nanoscale hexagonal magnesium hydroxide flame retardant is achieved for the first time, compared with an ultrasonic intermittent method, the nanoscale hexagonal magnesium hydroxide flame retardant has the advantages of being short in reaction period, high in reaction efficiency and uniform in reactant mixing, the preparation period is remarkably shortened to 3 hours, particle size distribution is optimized to be narrow amplitude, PDI is 0.300-0.999, generated magnesium hydroxide particles are in a regular nanometer hexagonal sheet shape, the particle size distribution is optimized to be small, and the particle size distribution is uniform. The dispersity and compatibility of the polymer in a polymer matrix are greatly improved, and excellent cost benefits and market competitiveness are shown in industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic flame retardants, and in particular to a nano hexagonal flaky magnesium hydroxide flame retardant and a preparation method thereof. Background Art

[0002] Plastics, rubber and other daily necessities are flammable and need to be flame-retardant to reduce fire hazards and potential dangers. For a long time, magnesium hydroxide has been the preferred material for inorganic filler flame retardants due to its advantages such as halogen-free, non-toxic, low-cost and high abundance. When it burns, it undergoes an endothermic reaction, absorbs heat, and reduces the surface temperature of the material. At the same time, a magnesium oxide protective layer is formed on the surface of the polymer material, isolating the penetration and transfer of heat and combustible gases, and by releasing water vapor, diluting the concentration of combustible gases and hindering the combustion of the material.

[0003] The traditional method of preparing magnesium hydroxide has problems such as long time cycle and low purity, and the obtained particle size and particle size distribution are large, resulting in poor compatibility in the polymer matrix, affecting the use effect. It is well known that sonochemistry has unique advantages in the preparation and dispersion of nanopowders, and can be used to efficiently prepare nano magnesium hydroxide particles. The sonochemical effect mainly comes from acoustic cavitation - the formation, oscillation, growth, contraction and collapse of cavities in liquids, and the physical and chemical changes caused by them, and quickly releases high temperature and high pressure in a very short time, micro-jet waves and high-speed flow, effectively enhancing the mass transfer process, promoting the formation of a large number of crystal nuclei, and preventing the agglomeration of nanoparticles. However, the intermittent ultrasonic synthesis process for preparing nano magnesium hydroxide currently has the disadvantage of uneven mixing of raw materials, resulting in large fluctuations in product quality, and the small intermittent ultrasonic cavitation area limits the cavitation effect, resulting in reduced sonochemical effects, and cannot effectively improve the problem of strong polarity of magnesium hydroxide particles, affecting its dispersibility in organic materials.

[0004] Maosheng Zuo et al. (Zuo M, Yu H, Wang D, et al. Jet cavitation-enhanced hydration method for the preparation of magnesium hydroxide [J]. Chemical Engineering and Processing-Process Intensification) prepared magnesium hydroxide flame retardant by using jet cavitation technology to enhance hydration method, and obtained well-dispersed layered magnesium hydroxide with a median particle size of D50 = 4.511 μm. Currently, the micron-sized magnesium hydroxide prepared by hydrothermal method on the market has the disadvantages of large particle size, wide particle size distribution, and serious agglomeration phenomenon, and its flame retardant effect is not as good as that of nano-sized magnesium hydroxide. Therefore, it is of great significance to find a new method to efficiently prepare a nano-sized hexagonal sheet magnesium hydroxide flame retardant with controllable morphology, good crystal form, small particle size and narrow distribution. Summary of the invention

[0005] In order to overcome the shortcomings of micron-sized magnesium hydroxide, such as uneven particle size distribution, large specific surface area, and long production cycle, the primary purpose of the present invention is to provide a method for preparing a nano hexagonal flaky magnesium hydroxide flame retardant.

[0006] Another object of the present invention is to provide a nano hexagonal flaky magnesium hydroxide flame retardant, which has regular morphology, complete crystal form, small particle size, narrow particle size distribution and short reaction time.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] A method for preparing nano hexagonal flaky magnesium hydroxide comprises the following steps:

[0009] (1) preparing a soluble magnesium salt solution and a precipitant aqueous solution respectively, preheating them respectively, continuously conveying the soluble magnesium salt solution and the precipitant aqueous solution respectively, mixing them, and obtaining a magnesium hydroxide nano-slurry after ultrasonication and reaction;

[0010] (2) The magnesium hydroxide nano-slurry is ultrasonically dispersed, filtered, and dried to obtain nano hexagonal flaky magnesium hydroxide.

[0011] Preferably, the concentration of the precipitant aqueous solution is 2.0-3.0 mol / L, and the concentration ratio of the soluble magnesium salt solution to the precipitant aqueous solution is 1:2-3.

[0012] Preferably, the temperature of the preheating treatment in step (1) is 60-80°C.

[0013] Preferably, the delivery flow rates of the soluble magnesium salt solution and the precipitant aqueous solution in step (1) are equal, i.e., 150-180 mL / min, and the delivery pressure is 0.2-0.3 MPa.

[0014] Preferably, the ultrasonic power in step (1) is 100-200w.

[0015] Preferably, the continuous delivery in step (1) is achieved by a peristaltic pump.

[0016] Preferably, the power of the ultrasonic dispersion in step (2) is 25w-75w, and the ultrasonic time is 2-6h.

[0017] Preferably, the drying in step (2) is vacuum drying, the drying temperature is 60-100° C., the pressure is -0.5 MPa to -1.0 MPa, and the time is 6-12 h.

[0018] Preferably, the soluble magnesium salt in step (1) is magnesium chloride, magnesium sulfate or magnesium nitrate, and the precipitant is sodium hydroxide or potassium hydroxide.

[0019] A nano hexagonal flaky magnesium hydroxide is prepared by the method.

[0020] Preferably, the nano hexagonal flaky magnesium hydroxide has a particle size of 300-500 nm, a particle size distribution PDI of 0.300-0.999, a controllable morphology, and a good crystal form.

[0021] An ultrasonic enhanced continuous flow device comprises a first liquid inlet, a second liquid inlet, a first liquid inlet channel, a second liquid inlet channel, a first delivery pump, a second delivery pump, a first air pressure gauge, a second air pressure gauge, a core reactor, a dispersed processor, and a collecting device;

[0022] The first liquid inlet is connected to a first delivery pump, the first delivery pump is connected to a first liquid inlet channel, and a first air pressure gauge is installed on the first liquid inlet channel;

[0023] The second liquid inlet is connected to a second delivery pump, the second delivery pump is connected to a second liquid inlet channel, and a second air pressure gauge is installed on the second liquid inlet channel;

[0024] The ends of the first liquid inlet channel and the second liquid inlet channel are both connected to the inlet of the core reactor, the outlet of the core reactor is connected to the inlet of the dispersion processor through a pipeline, and the dispersion processor is connected to the collection device through a pipeline;

[0025] An ultrasonic device is arranged inside the core reactor, and an ultrasonic dispersion device is arranged inside the dispersion processor.

[0026] The present invention provides a method for preparing a nano hexagonal flaky magnesium hydroxide flame retardant, and the magnesium hydroxide synthesis process is controlled by adjusting the concentration of the precipitant, the ultrasonic intensity, the ultrasonic time and other factors. The whole process realizes continuous reaction, and the mixing and pulping step time is short. The polarity of the magnesium hydroxide obtained after filtration is low. The magnesium hydroxide flame retardant finally prepared has a regular morphology and a narrow particle size distribution, which can improve its compatibility in a high molecular polymer matrix. If the precipitant concentration is not within the above-mentioned limited range, the excessively high alkalinity will destroy the hexagonal flaky structure; if the ultrasonic power is not within the above-mentioned limited range, the obtained hexagonal flaky morphology is irregular; if the ultrasonic time is too short, the obtained product morphology is irregular, and if the ultrasonic time is too long, the production cost is increased. If the pressure is too high, the flow rate cannot be accurately controlled, and the morphology and particle size of the obtained product are uncontrollable.

[0027] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0028] (1) The process of the present invention is simple to operate, the preparation time is short, the raw materials are cheap and readily available, and the production cost is low.

[0029] (2) The present invention realizes the controllable preparation of nano-scale hexagonal magnesium hydroxide flame retardant for the first time. The process has a short reaction cycle, is green and efficient, has high reaction efficiency, and the reactants are mixed evenly. The preparation cycle is shortened to 3 hours.

[0030] (3) The magnesium hydroxide flame retardant prepared by the present invention has a small particle size (300-500nm), a narrow particle size distribution (PDI is 0.300-0.999), a controllable morphology, a regular nano hexagonal flake shape, better dispersibility, and is easily compatible with high molecular polymers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a specific process flow chart of the present invention;

[0032] Figure 2 A diagram of an ultrasonic enhanced continuous flow device used in the present invention;

[0033] Figure 3 This is a scanning electron microscope image of the product of Example 1 of the present invention;

[0034] Figure 4 This is a particle size distribution diagram of the product of Example 1 of the present invention;

[0035] Figure 5 This is a scanning electron microscope image of the product of Example 2 of the present invention;

[0036] Figure 6 This is a particle size distribution diagram of the product of Example 2 of the present invention;

[0037] Figure 7 This is a scanning electron microscope image of the product of Example 3 of the present invention;

[0038] Figure 8 This is a particle size distribution diagram of the product of Example 3 of the present invention;

[0039] Fig. 9 This is a scanning electron microscope image of the product of Example 4 of the present invention;

[0040] Fig.10 This is a particle size distribution diagram of the product of Example 4 of the present invention;

[0041] Fig.11 This is a scanning electron microscope image of the product of Example 5 of the present invention;

[0042] Fig.12 This is a particle size distribution diagram of the product of Example 5 of the present invention;

[0043] Fig.13 This is a scanning electron microscope image of the product of Comparative Example 1 of the present invention;

[0044] Fig.14 This is a scanning electron microscope image of the product of Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto. For process parameters not particularly noted, conventional techniques may be used.

[0046] The schematic diagram of the equipment used for ultrasonic enhanced continuous flow of the present invention is as follows Figure 2 As shown, it includes a first liquid inlet, a second liquid inlet, a first liquid inlet channel, a second liquid inlet channel, a first delivery pump, a second delivery pump, a first air pressure gauge, a second air pressure gauge, a core reactor, a distributed processor, and a collecting device;

[0047] The first liquid inlet is connected to a first delivery pump, the first delivery pump is connected to a first liquid inlet channel, and a first air pressure gauge is installed on the first liquid inlet channel;

[0048] The second liquid inlet is connected to a second delivery pump, the second delivery pump is connected to a second liquid inlet channel, and a second air pressure gauge is installed on the second liquid inlet channel;

[0049] The ends of the first liquid inlet channel and the second liquid inlet channel are both connected to the inlet of the core reactor, the outlet of the core reactor is connected to the inlet of the dispersion processor through a pipeline, and the dispersion processor is connected to the collection device through a pipeline;

[0050] The core reactor is provided with an ultrasonic device inside, and the dispersion processor is provided with an ultrasonic dispersion device inside;

[0051] The first delivery pump and the second delivery pump control the flow rates of the soluble magnesium salt solution and the precipitant aqueous solution to make the flow rates of the two reaction solutions equal.

[0052] Solution A and solution B are placed in corresponding beakers respectively, and after being preheated at the same time, the equipment is started, solution A flows through the first liquid inlet channel, solution B flows through the second liquid inlet channel, and solution A and solution B are mixed at the ends of the first and second liquid inlet channels and then enter the core reactor to react to obtain magnesium hydroxide slurry, which is then subjected to ultrasonic dispersion treatment by a dispersion processor, the product solution is collected, and then filtered and dried to obtain a nano hexagonal flaky magnesium hydroxide flame retardant.

[0053] The peristaltic pump is adjusted to control the liquid flow rate of solution A and solution B (equal), the ultrasonic intensity and time are adjusted, and the reaction conditions are precisely controlled to achieve the preparation of nano-scale hexagonal flaky magnesium hydroxide flame retardant.

[0054] Solution A can be a soluble magnesium salt solution (such as magnesium chloride aqueous solution) or a precipitant aqueous solution (such as sodium hydroxide aqueous solution);

[0055] Solution B can be a soluble magnesium salt solution (such as magnesium chloride aqueous solution) or a precipitant aqueous solution (such as sodium hydroxide aqueous solution).

[0056] The particle size and distribution of magnesium hydroxide were determined using a dynamic light scattering (DLS) particle size analyzer.

[0057] Example 1

[0058] This embodiment provides a method for preparing a nano-scale hexagonal flaky magnesium hydroxide flame retardant. The specific process is as follows: Figure 1 As shown, the following steps are included:

[0059] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.0 mol / L sodium hydroxide aqueous solution and preheating the two reaction solutions to 60° C. at the same time, continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 150 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and the peristaltic pump is started at the same time to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0060] (2) subjecting the slurry in step (1) to ultrasonic dispersion treatment, with an ultrasonic power of 25 W and an ultrasonic time of 3 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0061] (3) The magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (2) was filtered and dried under vacuum pressure at a temperature of 80° C. and a pressure of −1.0 MPa for 6 h to obtain a dry powder, which is a flame retardant magnesium hydroxide with a regular morphology and good dispersibility. The particle size is 300-500 nm, the particle size distribution is narrow, and the PDI is 0.933 (e.g. Figure 4 ).

[0062] Example 2

[0063] This embodiment provides a method for preparing a nano-scale hexagonal flaky magnesium hydroxide flame retardant, comprising the following steps:

[0064] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.0 mol / L sodium hydroxide aqueous solution and preheating the two reaction solutions to 70° C. at the same time, continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 160 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and the peristaltic pump is started at the same time to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0065] (2) subjecting the slurry in step (1) to ultrasonic dispersion treatment, with an ultrasonic power of 50 W and an ultrasonic time of 3 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0066] (3) The magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (2) was filtered and dried under vacuum pressure at a temperature of 80° C. and a pressure of −1.0 MPa for 8 h to obtain a dry powder, which is a flame retardant magnesium hydroxide with a regular morphology and good dispersibility. The particle size is 300 to 500 nm, the particle size distribution is narrow, and the PDI is 0.839 (e.g. Figure 6 ).

[0067] Example 3

[0068] This embodiment provides a method for preparing a nano-scale hexagonal flaky magnesium hydroxide flame retardant, comprising the following steps:

[0069] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.0 mol / L sodium hydroxide aqueous solution and preheating the two reaction solutions to 70° C. at the same time, continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 170 mL / min), the pressure to 0.2 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and the peristaltic pump is started at the same time to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0070] (2) subjecting the slurry in step (1) to ultrasonic dispersion treatment, with an ultrasonic power of 75 W and an ultrasonic time of 3 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0071] (3) The magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (2) is filtered and dried under vacuum pressure at a temperature of 100° C. and a pressure of −1.0 MPa for 6 h to obtain a dry powder, which is a flame retardant magnesium hydroxide having a regular morphology and good dispersibility, a particle size of 300 to 500 nm, a narrow particle size distribution, and a PDI of 0.591 (e.g. Figure 8 ).

[0072] Example 4

[0073] This embodiment provides a method for preparing a nano-scale hexagonal flaky magnesium hydroxide flame retardant, comprising the following steps:

[0074] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.5 mol / L sodium hydroxide aqueous solution and preheating the two reaction solutions to 80° C. at the same time, continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 170 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and the peristaltic pump is started at the same time to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0075] (2) subjecting the magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (1) to ultrasonic dispersion treatment, with an ultrasonic power of 25 W and an ultrasonic time of 3 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0076] (3) The magnesium hydroxide subjected to ultrasonic dispersion treatment in step (2) is filtered and dried under vacuum at a temperature of 80° C. and a pressure of −1.0 MPa for 6 h to obtain a dry powder, which is a flame retardant magnesium hydroxide having a regular morphology and good dispersibility, a particle size of 300 to 500 nm, a narrow particle size distribution, and a PDI of 0.438 (e.g. Fig.10 ).

[0077] Example 5

[0078] This embodiment provides a method for preparing a nano-scale hexagonal flaky magnesium hydroxide flame retardant, comprising the following steps:

[0079] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.5 mol / L sodium hydroxide aqueous solution and preheating the two reaction solutions to 80° C. at the same time, continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 180 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 W, the ultrasonic intensity of the core reactor is set to 100%, and the peristaltic pump is started at the same time to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0080] (2) subjecting the magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (1) to ultrasonic dispersion treatment, with an ultrasonic power of 50 W and an ultrasonic time of 3 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0081] (3) The magnesium hydroxide subjected to ultrasonic dispersion treatment in step (2) is filtered and dried under vacuum pressure at a temperature of 100° C. and a pressure of −1.0 MPa for 6 hours to obtain a dry powder, which is a flame retardant magnesium hydroxide with a regular morphology and good dispersibility, a particle size of 300 to 500 nm, a narrow particle size distribution, and a PDI of 0.316.

[0082] Comparative Example 1

[0083] This comparative example provides a method for preparing a magnesium hydroxide flame retardant, comprising the following steps:

[0084] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.0 mol / L sodium hydroxide aqueous solution and preheating them to 60° C., and simultaneously continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 150 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and simultaneously starting the peristaltic pump to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0085] (2) The magnesium hydroxide slurry in step (1) is not subjected to ultrasonic dispersion treatment and is allowed to stand for 3 hours;

[0086] (3) The slurry in step (2) was filtered and dried under vacuum at 80° C., at a pressure of −1.0 MPa, for 6 h to obtain a dry powder, which had poor morphology regularity and could not present a regular hexagonal flake morphology.

[0087] Comparative Example 2

[0088] This comparative example provides a method for preparing a magnesium hydroxide flame retardant, comprising the following steps:

[0089] (1) preparing a 1.0 mol / L magnesium chloride hexahydrate aqueous solution and a 2.0 mol / L sodium hydroxide aqueous solution and preheating them to 60° C., and simultaneously continuously conveying the magnesium chloride aqueous solution and the sodium hydroxide aqueous solution respectively through an ultrasonic enhanced continuous flow device, adjusting the conveying liquid flow rate to be equal (both to 150 mL / min), the pressure to 0.3 MPa, mixing at the end of the liquid inlet pipeline and entering the core reactor, the ultrasonic power of the core reactor is 100 w, the ultrasonic intensity of the core reactor is set to 100%, and simultaneously starting the peristaltic pump to achieve equal volume of materials entering the core reactor to generate nano slurry, which is the magnesium hydroxide slurry obtained by the liquid conveying method of ultrasonic enhanced continuous flow;

[0090] (2) subjecting the slurry in step (1) to ultrasonic dispersion treatment, with an ultrasonic intensity of 50 W and an ultrasonic time of 0.5 h to obtain an ultrasonically dispersed magnesium hydroxide slurry;

[0091] (3) The magnesium hydroxide slurry subjected to ultrasonic dispersion treatment in step (2) was filtered and dried under vacuum pressure at a temperature of 80° C. and a pressure of −1.0 MPa for 6 h. The obtained dry powder had poor morphology regularity and could not present a regular hexagonal flake morphology.

[0092] Figure 3 , Figure 5 , Figure 7 , Fig. 9 , Fig.11 They are scanning electron microscope images of the products of Examples 1 to 5, respectively. It can be seen from the scanning electron microscope image at a magnification of 50,000 times that the product morphology is regular hexagonal flakes, and the products prepared by the process of the present invention have consistent morphology and good dispersibility.

[0093] Fig.13 This is a scanning electron microscope image of the product of Comparative Example 1. It can be seen from the scanning electron microscope image at a magnification of 50,000 times that due to the lack of ultrasonic dispersion, the magnesium hydroxide has a strong polarity, exhibits adhesion, and the product morphology is poor.

[0094] Fig.14 This is a scanning electron microscope image of the product of Comparative Example 2. It can be seen from the scanning electron microscope image at a magnification of 50,000 times that due to the short ultrasonic time, the magnesium hydroxide grain size is small, the morphology is irregular, and the product morphology is poor.

[0095] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A method for preparing a nano hexagonal flaky magnesium hydroxide flame retardant, characterized in that: The following steps are involved: (1) preparing a soluble magnesium salt solution and a precipitant aqueous solution respectively, preheating them respectively, continuously conveying the soluble magnesium salt solution and the precipitant aqueous solution respectively, mixing them, and obtaining a magnesium hydroxide nano-slurry after ultrasonication and reaction; (2) Ultrasonic dispersion of the magnesium hydroxide nano-slurry is performed, filtration is performed, and drying is performed to obtain a nano hexagonal flaky magnesium hydroxide flame retardant.

2. The method for preparing the nano hexagonal flaky magnesium hydroxide flame retardant according to claim 1, characterized in that: The concentration of the precipitant aqueous solution in step (1) is 2.0-3.0 mol / L, and the concentration ratio of the soluble magnesium salt solution to the precipitant aqueous solution is 1:2-3.

3. The method for preparing the nano hexagonal flaky magnesium hydroxide flame retardant according to claim 1, characterized in that: The temperature of the preheating treatment in step (1) is 60-80°C; The delivery flow rates of the soluble magnesium salt solution and the precipitant aqueous solution in step (1) are equal, namely, 150-180 mL / min, and the delivery pressure is 0.2-0.3 MPa.

4. The method for preparing the nano hexagonal flaky magnesium hydroxide flame retardant according to claim 1, characterized in that: The power of the ultrasound in step (1) is 100-200w.

5. The method for preparing the nano-scale hexagonal flaky magnesium hydroxide flame retardant according to any one of claims 1 to 4, characterized in that: The power of the ultrasonic dispersion in step (2) is 25w-75w, and the ultrasonic time is 2-6h.

6. The method for preparing the nano hexagonal flaky magnesium hydroxide flame retardant according to claim 5, characterized in that: The drying in step (2) is vacuum drying, the drying temperature is 60-100° C., the pressure is -0.5 MPa to -1.0 MPa, and the time is 6-12 h.

7. The method for preparing the nano hexagonal flaky magnesium hydroxide flame retardant according to claim 6, characterized in that: In step (1), the soluble magnesium salt is magnesium chloride, magnesium sulfate or magnesium nitrate, and the precipitant is sodium hydroxide or potassium hydroxide.

8. A nano hexagonal flaky magnesium hydroxide flame retardant, characterized in that: The method is prepared by any one of claims 1 to 7.

9. The nano hexagonal flaky magnesium hydroxide flame retardant according to claim 8, characterized in that: The particle size of the flame retardant is 300-500 nm, and the particle size distribution PDI is 0.300-0.999.

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