A thermally conductive aramid insulating paper-based material, its preparation method and application

Abstract

This invention discloses a thermally conductive aramid insulating paper-based material, its preparation method, and its application. The preparation method of the thermally conductive aramid insulating paper-based material includes the following steps: (1) introducing amino groups onto the surface of boron nitride nanosheets to obtain aminated boron nitride nanosheets; (2) dissolving m-phenylenediamine in N,N-dimethylacetamide, then adding isophthaloyl chloride, and then adding aminated boron nitride nanosheets, and reacting to obtain a thermally conductive aramid polymer solution; (3) wet spinning the thermally conductive aramid polymer solution to obtain thermally conductive aramid fibers; (4) mixing the thermally conductive aramid fibers with precipitated fibers to form a thermally conductive aramid insulating paper-based material. This invention utilizes the amide group connection between aminated boron nitride nanosheets and aramid macromolecules to improve the interfacial compatibility between fillers and substrates in paper materials, thereby improving the strength and thermal conductivity of paper materials.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of papermaking industry and polymer materials, and specifically relates to a thermally conductive aramid insulating paper-based material, its preparation method and application. Background Technology

[0002] In recent years, with the increasing power density of electronic devices and motors, the demand for heat dissipation performance of insulation materials has also risen. Aramid insulating paper is a high-performance insulating material with excellent thermal stability, mechanical strength, and electrical insulation properties, and can be used as insulation material between turns, phases, windings, and wire ends of electrical equipment such as motors, generators, and transformers. However, aramid insulating paper has a very low thermal conductivity. The thermal conductivity of mature aramid insulating paper products is typically between 0.1 and 0.2 W / (m·K). In high-frequency and high-power environments, the heat that rapidly accumulates in electrical equipment using aramid paper as insulation material cannot be dissipated in time, seriously reducing the performance and lifespan of the equipment, and potentially leading to equipment failure, fire, and threatening social and personal safety.

[0003] Boron nitride nanosheets are two-dimensional sheet-like nanomaterials with a graphene-like structure, which can be obtained through methods such as chemical vapor deposition, mechanical exfoliation, and liquid-phase exfoliation. Boron nitride nanosheets exhibit high thermal conductivity (400-2000 W / m²). -1 K -1 Excellent electrical insulation properties (10) 14 -10 16 Boron nitride nanosheets possess excellent thermal conductivity (Ωcm), chemical stability, and biocompatibility. They are an ideal thermally conductive filler in the field of thermal management and can be composited with polymers to prepare thermally conductive polymer materials. Furthermore, boron nitride nanosheets have important applications in various fields such as lubricants, high-temperature antioxidant coatings, catalyst supports, and drug delivery media.

[0004] Improving the thermal conductivity of aramid insulating paper by adding boron nitride nanosheets is an effective method. Aramid paper material is usually made by wet papermaking of aramid precipitated fibers and aramid chopped fibers in a certain ratio. The precipitated fibers have a thin film wrinkled appearance with microfibers growing on the surface, and are usually used as fillers and binders in paper. The chopped fibers have a smooth and stiff surface and are generally dispersed evenly in the paper as a skeleton. The specific preparation process of aramid paper base material includes: (1) washing and pulping of precipitated fibers; (2) dispersing of chopped fibers in water; (3) mixing of precipitated fibers and chopped fibers; (4) filtration; (5) hot pressing. Boron nitride nanosheets can be added directly to the pulp before filtration and remain directly in the paper after filtration. However, due to the smooth and chemically inert surfaces of both aramid fibers and boron nitride nanosheets, filler retention is low, leading to powdering and flaking in the paper. Furthermore, severe phonon scattering occurs at the filler-substrate interface, increasing interfacial thermal resistance and hindering thermal conductivity improvement. In addition, the poor dispersibility of boron nitride nanosheets results in chaotic, disordered, and inefficient thermal conductivity pathways within the paper, necessitating increased filler loading to achieve optimal thermal conductivity. To address these issues, surface modification of boron nitride nanosheets and the use of aramid nanofibers (ANF) to replace aramid fibers are two effective strategies (e.g., Chinese patents CN202310317355.2 and CN201810838115.6). While these strategies improve the interfacial compatibility between the substrate and filler, they do not effectively solve the problems of chaotic thermal conductivity pathways and high filler loading. Improving the compatibility of boron nitride nanosheets and aramid fibers through appropriate methods and constructing orderly and efficient thermal conductivity pathways are key to obtaining aramid-based insulating paper materials with good thermal conductivity. Summary of the Invention

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary objective of this invention is to provide a method for preparing a thermally conductive aramid insulating paper-based material.

[0006] Another object of the present invention is to provide a thermally conductive aramid insulating paper-based material prepared by the above method.

[0007] Another object of the present invention is to provide the application of the above-mentioned thermally conductive aramid insulating paper-based material.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] A method for preparing a thermally conductive aramid insulating paper-based material includes the following steps:

[0010] (1) Preparation of amino boron nitride nanosheets: Hexagonal boron nitride, urea and water were mixed and put into a ball mill for ball milling. After ball milling, excess urea was washed away with water and then ultrasonically dispersed in water. Large-sized unpeeled boron nitride was removed by centrifugation, and the lower solid layer was collected by centrifugation again and freeze-dried to obtain amino boron nitride nanosheets.

[0011] (2) Preparation of thermally conductive aramid polymer solution: The amino boron nitride nanosheets obtained in step (1) and N,N-dimethylacetamide are ultrasonically mixed evenly to obtain an amino boron nitride nanosheet suspension; under a protective gas atmosphere, m-phenylenediamine is dissolved in N,N-dimethylacetamide to obtain a m-phenylenediamine solution; then, under stirring conditions of -20℃ to 0℃, isophthaloyl chloride is slowly added to the m-phenylenediamine solution multiple times, followed by the amino boron nitride nanosheet suspension, and the stirring speed is increased to carry out the polycondensation reaction. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues until the reaction ends. Finally, the acid-binding agent Ca(OH)2 is added to adjust the pH to 4 to 9 to obtain a thermally conductive aramid polymer solution.

[0012] (3) Preparation of thermally conductive aramid fiber: The thermally conductive aramid polymer solution obtained in step (2) is wet-spun. After being extruded by the spinning nozzle, it is solidified, stretched, wound and heat-set to obtain thermally conductive aramid fiber.

[0013] (4) Wet papermaking: The thermally conductive aramid fibers obtained in step (3) are cut into short fibers, and then a dispersant and water are added to prepare a short fiber suspension; the precipitated fibers are prepared into a precipitated fiber suspension after disintegration treatment; the short fiber suspension and the precipitated fiber suspension are stirred and mixed evenly, and then wet papermaking is carried out, followed by pressing and dewatering (filtration), and hot pressing (forming) to obtain thermally conductive aramid insulating paper base material.

[0014] The mass ratio of hexagonal boron nitride, urea and water in step (1) is (1-10):(10-100):(1-100); preferably 1:30:12.

[0015] The water mentioned in step (1) is preferably deionized water.

[0016] The ball mill mentioned in step (1) is preferably a planetary ball mill.

[0017] The conditions for ball milling in step (1) are: rotation speed 10-1000 rpm, ball milling time 2-96 h; preferably: rotation speed 400-500 rpm, ball milling time 20-48 h.

[0018] The grinding balls used in the ball mill are 8mm agate balls and 4mm agate balls, with a mass ratio of 1:3 and a ball-to-material ratio of 3:2.

[0019] The water washing described in step (1) can be performed by vacuum filtration, repeated multiple times until the urea is cleaned.

[0020] The ultrasonic dispersion time in step (1) is 20 to 40 minutes; preferably 30 minutes.

[0021] In step (1), the conditions for removing large-sized unpeeled boron nitride by centrifugation (low-speed centrifugation) are: rotation speed 1000-4000 rpm, centrifugation time 20-40 min (preferably 30 min).

[0022] In step (1), the conditions for collecting the lower layer solid by centrifugation (high-speed centrifugation) are: rotation speed 4000-8000 rpm, centrifugation time 30-60 min (preferably 50 min).

[0023] The concentration of the aminoboron nitride nanosheet suspension in step (2) is 10–30 mg / mL; preferably 20 mg / mL.

[0024] The conditions for ultrasound in step (2) are: ultrasound power 300-500W, ultrasound time 20-40 min; preferably: ultrasound power 400W, ultrasound time 30 min.

[0025] In step (2), the purity of the two monomers, m-phenylenediamine and isophthaloyl chloride, is greater than 99.9%; the purity of N,N-dimethylacetamide is greater than 99.99%, and the water content is less than 500 ppm.

[0026] The molar ratio of m-phenylenediamine and isophthaloyl chloride in step (2) is (1-10):(1-10); preferably 1:(1.005-1.01); more preferably 1:1.005.

[0027] The protective gas mentioned in step (2) is nitrogen.

[0028] The concentration of the m-phenylenediamine solution in step (2) is 0.5–2 mol / L; preferably 0.8–1.2 mol / L; more preferably 1.1 mol / L.

[0029] In step (2), the rotation speed when adding isophthaloyl chloride is 100-600 rpm; preferably 500-600 rpm.

[0030] The amount of aminated boron nitride nanosheets added in step (2) is 1 to 200% of the mass of m-phenylenediamine; preferably 5 to 20% of the mass of m-phenylenediamine.

[0031] In step (2), increasing the stirring speed means increasing the stirring speed to 1000-2000 rpm; preferably, it means increasing the stirring speed to 1000 rpm.

[0032] The conditions for the polycondensation reaction described in step (2) are: initial temperature -20℃ to 0℃ (preferably -2℃ to -6℃; more preferably -5℃), and total reaction time of 0.1 to 48h.

[0033] The reaction time described in step (2) is 1 to 10 hours; preferably 4 hours.

[0034] The pH adjustment mentioned in step (2) is to adjust the pH to 7.0 to 7.4.

[0035] The solid content of the thermally conductive aramid polymer solution in step (3) is 1% to 50%; preferably 10% to 20%; more preferably 15%.

[0036] The wet spinning conditions described in step (3) are as follows: the nozzle extrusion speed is 10-100 cm / min; the volume ratio of water to N,N-dimethylacetamide in the coagulation bath is (1-100):(1-100); the residence time in the coagulation bath is 1-500 s; the coagulation bath temperature is 20-60℃; the stretching ratio is 1.1-50 times; and the heat setting temperature is 50-600℃. Preferably, the nozzle extrusion speed is 500 cm / min; the volume ratio of water to N,N-dimethylacetamide in the coagulation bath is 50:50; the residence time in the coagulation bath is 30-80 s; the coagulation bath temperature is 25-45℃; the stretching ratio is 2.4-3.7 times; and the heat setting temperature is 320℃.

[0037] The length of the chopped fiber in step (4) is 1 to 100 mm; preferably 3 to 6 mm.

[0038] The dispersant mentioned in step (4) is preferably polyethylene oxide with a viscosity-average molecular weight of about 100,000.

[0039] The amount of dispersant added in step (4) is 0.1 to 0.5% of the mass of the chopped fiber; preferably 0.3% of the mass of the chopped fiber.

[0040] The concentration of the short-cut fiber suspension in step (4) is 0.01 to 10% by mass; preferably 0.1% by mass.

[0041] In step (4), the short-cut fiber suspension can be obtained by processing with a wall-breaking machine. The processing conditions are: 10,000 rpm for 3 to 5 minutes (preferably 3 minutes).

[0042] The mass ratio of chopped fibers to precipitated fibers in step (4) is (1-10):(1-10); preferably (3-5):(5-7).

[0043] The concentration of the precipitated fiber suspension in step (4) is 0.01 to 10% by mass; preferably 0.1% by mass.

[0044] The rotation speed of the scavenging process in step (4) is 800 to 1200 rpm; preferably 1000 rpm.

[0045] The pressing and dehydration conditions described in step (4) are: pressing and dehydration at 25℃ and 0.2MPa pressure for 5 min.

[0046] The hot pressing conditions described in step (4) are: hot pressing temperature 50-600℃, hot pressing pressure 0.01-20Mpa, and hot pressing time 0.1-48h; preferably: hot pressing temperature 200℃, hot pressing pressure 0.5Mpa, and hot pressing time 30min.

[0047] The basis weight of the thermally conductive aramid insulating paper-based material mentioned in step (4) is 1-100 g / m³. 2 Preferably 50-70 g / m 2 .

[0048] A thermally conductive aramid insulating paper-based material is prepared by any of the methods described above.

[0049] The application of the thermally conductive aramid insulating paper-based material in insulating materials.

[0050] The aforementioned thermally conductive aramid insulating paper-based material has applications in multiple fields such as electrical equipment, electronic information, aerospace, and automotive industries.

[0051] The present invention has the following advantages and effects compared with the prior art:

[0052] 1. The thermally conductive aramid insulating paper-based material of this invention starts from the monomer condensation reaction, connecting amino boron nitride nanosheets with aramid macromolecules through amide bonds, which greatly improves the interfacial compatibility between the filler and the substrate and reduces the interfacial thermal resistance. Furthermore, thermally conductive aramid insulating fibers are prepared from the polymer solution using wet spinning technology, enriching and fixing boron nitride nanosheets onto individual fibers, solving the problems of poor dispersion, low retention, and paper dusting / flaking of boron nitride nanosheets. Finally, the cut thermally conductive aramid insulating fibers are mixed with commercially available aramid precipitated fibers to prepare thermally conductive aramid insulating paper. The thermally conductive aramid insulating fibers construct the thermally conductive framework in the paper, forming an ordered and efficient thermally conductive pathway, reducing the amount of boron nitride nanosheets added.

[0053] 2. In this invention, hexagonal boron nitride and urea are used as basic raw materials. Amino groups are introduced on the surface of boron nitride nanosheets to increase the roughness and surface activity of the boron nitride nanosheets.

[0054] 3. This invention utilizes the amide group connection between amino boron nitride nanosheets and aramid macromolecules to improve the interfacial compatibility between fillers and substrates in paper materials; thermally conductive aramid fibers enriched with boron nitride nanosheets are prepared using wet spinning technology, and finally, thermally conductive aramid insulating paper is produced by combining it with precipitated fibers.

[0055] 4. The thermally conductive aramid insulating paper-based material prepared in this invention can be widely used in many fields such as electrical equipment, electronic information, aerospace and automotive industries. Attached Figure Description

[0056] Figure 1 This is a schematic diagram illustrating the preparation process of the thermally conductive aramid insulating paper-based material in this invention.

[0057] Figure 2 This is an atomic force microscope image of the aminoboron nitride nanosheets used in this invention.

[0058] Figure 3 The image shows a comparison of hexagonal boron nitride and amino boron nitride nanosheets in Example 4 of this invention; where A is hexagonal boron nitride and B is amino boron nitride nanosheets.

[0059] Figure 4 The image shows the thermally conductive aramid fiber and the chopped short fibers cut from it in Embodiment 4 of the present invention; wherein, A is the thermally conductive aramid fiber; and B is the chopped short fibers cut from the thermally conductive aramid fiber.

[0060] Figure 5 This is a physical image of the thermally conductive aramid insulating paper prepared in Example 4 of the present invention. Detailed Implementation

[0061] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field. Test methods in the following embodiments that do not specify specific experimental conditions are generally performed according to conventional experimental conditions or the experimental conditions recommended by the manufacturer. Unless otherwise specified, the starting materials in the preparation methods of the present invention can be purchased from the market or prepared according to existing technical methods.

[0062] The preparation process of the thermally conductive aramid insulating paper-based material of this invention is as follows: Figure 1 As shown.

[0063] The precipitated fibers involved in the embodiments and comparative examples of this invention were purchased from Ganzhou Longbang Materials Technology Co., Ltd., and had a fineness of 2 denier.

[0064] The polyethylene oxide used in the embodiments and comparative examples of this invention was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., with a viscosity-average molecular weight of approximately 100,000.

[0065] In the embodiments and comparative examples of this invention, the tensile strength index was tested in accordance with GB / T12914-2008; the thermal conductivity of the composite paper was tested using a thermal constant analyzer (Hot Disk TPS2200), with each sample tested 5 times and the average value taken as the thermal conductivity.

[0066] Example 1

[0067] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0068] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:30:12 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2 (mass ratio)). The planetary ball mill was operated at a speed of 500 rpm for 20 h. After ball milling, the nanosheets were washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was completely removed. The paste obtained by vacuum filtration was then processed. The boron nitride nanosheets were dispersed in deionized water by sonication for 30 min, centrifuged at 1000 rpm for 30 min to remove large pieces of boron nitride, and the supernatant was collected and centrifuged at 4000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Finally, the aminoboron nitride nanosheets were uniformly mixed with N,N-dimethylacetamide and sonicated at 400W power for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0069] (2) Preparation of thermally conductive aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of ≥99.9% and N,N-dimethylacetamide solution with a purity of ≥99.99% and a water content of ≤500ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.01; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.1mol / L solution, and then placed at -6℃. At low temperature, isophthaloyl chloride was slowly added multiple times with a stirring rate of 500 rpm. After the isophthaloyl chloride was completely added, an aminoboron nitride nanosheet suspension was added, with the amount of aminoboron nitride nanosheets being equivalent to 10% of the mass of m-phenylenediamine. The stirring speed was increased to 1000 rpm, and the reaction temperature was controlled between 30℃ and 60℃. After the rod-climbing phenomenon occurred, the reaction was continued for 4 hours. Then, an acid-binding agent Ca(OH)2 was added to adjust the pH to 7.0, and a polymer solution was obtained.

[0070] (3) Preparation of thermally conductive aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 15%, set the spinning nozzle speed to 50 cm / min, carry out wet spinning, the volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50, stay in the coagulation bath for 30s, the coagulation bath temperature is 45℃, the stretching ratio is 3.7 times, and after winding, heat set at 320℃ to obtain thermally conductive aramid fiber.

[0071] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into 3mm short fibers. With the help of a dispersant (polyethylene oxide, amounted to 0.3% of the mass of the short fibers) and water, a 0.1wt% suspension is prepared by blending at 10000rpm for 3min (based on the mass of the short fibers). The precipitated fibers are weighed according to a mass ratio of 40:60 between the short fibers and the precipitated fibers. After the precipitated fibers are disintegrated by a fiber disintegrator at 1000rpm, a 0.1wt% suspension is prepared. The short fibers and the precipitated fiber suspension are mixed and stirred evenly. After wet papermaking, the wet paper web is pressed and dehydrated at 25℃ and 0.2MPa for 5min. Then it is directly thermoformed (i.e., aramid wet paper is obtained by wet papermaking and then dried and formed). The temperature is 200℃, the pressure is 0.5MPa, the time is 30min, and the paper basis weight is 54.3g / m 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0072] The thermally conductive aramid insulating paper-based material was tested for performance. The tensile strength index and thermal conductivity were 124.5 N*m / g and 0.372 W / (m*K), respectively.

[0073] Example 2

[0074] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0075] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:30:12 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2). The planetary ball mill was rotated at 400 rpm and the ball milling time was 48 h. After the ball milling was completed, the mixture was washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was clean. The paste obtained by vacuum filtration was ultrasonically dispersed in deionized water for 30 min and centrifuged at 3000 rpm for 30 min to remove large pieces of boron nitride. The supernatant was collected and centrifuged at 7000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Finally, the aminoboron nitride nanosheets and N,N-dimethylacetamide were mixed uniformly and ultrasonically sonicated at 400W power for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0076] (2) Preparation of thermally conductive aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of ≥99.9% and N,N-dimethylacetamide solution with a purity of ≥99.99% and a water content of ≤500ppm were used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction was 1:1.008; the specific steps were as follows: under nitrogen atmosphere, m-phenylenediamine was first dissolved in N,N-dimethylacetamide to prepare a 1.2mol / L solution, and then placed at -5℃. At low temperature, isophthaloyl chloride was slowly added multiple times with a stirring rate of 600 rpm. After the isophthaloyl chloride was completely added, an aminoboron nitride nanosheet suspension was added, with the amount of aminoboron nitride nanosheets being equivalent to 15% of the mass of m-phenylenediamine. The stirring speed was increased to 1000 rpm, and the reaction temperature was controlled between 30℃ and 60℃. After the rod-climbing phenomenon occurred, the reaction was continued for 4 hours. Then, an acid-binding agent Ca(OH)2 was added to adjust the pH to 7.0, and a polymer solution was obtained.

[0077] (3) Preparation of thermally conductive aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 15%, set the spinning nozzle speed to 50 cm / min, perform wet spinning, the volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50, stay in the coagulation bath for 30s, the coagulation bath temperature is 25℃, the stretching ratio is 3.3 times, and after winding, heat set at 320℃ to obtain thermally conductive aramid fiber.

[0078] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into 6mm short fibers. With the help of a dispersant (polyethylene oxide, amounted to 0.3% of the mass of the short fibers) and water, a 0.1 wt% suspension is prepared by blending at 10000 rpm for 3 minutes (based on the mass of the short fibers). The precipitated fibers are weighed according to a mass ratio of 30:70 between the short fibers and the precipitated fibers. The precipitated fibers are then dispersed by a fiber disintegrator at 1000 rpm and prepared into a 0.1 wt% suspension. The short fibers and the precipitated fiber suspension are mixed and stirred evenly. After wet papermaking, the wet paper web is pressed and dehydrated at 25°C and 0.2 MPa for 5 minutes. Then it is directly thermoformed (i.e., aramid wet paper is obtained by wet papermaking and then dried and formed). The temperature is 200°C, the pressure is 0.5 MPa, the time is 30 minutes, and the paper basis weight is 60.6 g / m². 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0079] The thermally conductive aramid insulating paper-based material was tested for performance, and its tensile strength index and thermal conductivity were 97.3 N*m / g and 0.396 W / (m*K), respectively.

[0080] Example 3

[0081] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0082] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:20:10 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2). The planetary ball mill was rotated at 500 rpm and the ball milling time was 20 h. After the ball milling was completed, the mixture was washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was clean. The paste obtained by vacuum filtration was ultrasonically dispersed in deionized water for 30 min and centrifuged at 1000 rpm for 30 min to remove large pieces of boron nitride. The supernatant was collected and centrifuged at 4000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Finally, the aminoboron nitride nanosheets and N,N-dimethylacetamide were mixed uniformly and ultrasonically sonicated at 400W power for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0083] (2) Preparation of thermally conductive aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of ≥99.9% and N,N-dimethylacetamide solution with a purity of ≥99.99% and a water content of ≤500ppm were used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction was 1:1.01; the specific steps were as follows: under nitrogen atmosphere, m-phenylenediamine was first dissolved in N,N-dimethylacetamide to prepare a 0.8mol / L solution, and then placed at -2℃ At low temperature, isophthaloyl chloride was slowly added multiple times with a stirring rate of 500 rpm. After the isophthaloyl chloride was completely added, an aminoboron nitride nanosheet suspension was added, with the amount of aminoboron nitride nanosheets being equivalent to 5% of the mass of m-phenylenediamine. The stirring speed was increased to 1000 rpm, and the reaction temperature was controlled between 30℃ and 60℃. After the rod-climbing phenomenon occurred, the reaction was continued for 4 hours. Then, an acid-binding agent Ca(OH)2 was added to adjust the pH to 7.4, and a polymer solution was obtained.

[0084] (3) Preparation of thermally conductive aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 15%, set the spinning nozzle speed to 50 cm / min, perform wet spinning, the volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50, stay in the coagulation bath for 30s, the coagulation bath temperature is 25℃, the stretching ratio is 2.4 times, and after winding, heat set at 320℃ to obtain thermally conductive aramid fiber.

[0085] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into 3mm short fibers. With the help of a dispersant (polyethylene oxide, amounted to 0.3% of the mass of the short fibers) and water, a 0.1 wt% suspension is prepared by blending at 10000 rpm for 3 minutes (based on the mass of the short fibers). The precipitated fibers are weighed according to a mass ratio of 50:50 between the short fibers and the precipitated fibers. After the precipitated fibers are disintegrated by a fiber disintegrator at 1000 rpm, a 0.1 wt% suspension is prepared. The short fibers and the precipitated fiber suspension are mixed and stirred evenly. After wet papermaking, the wet paper web is pressed and dehydrated at 25°C and 0.2 MPa for 5 minutes. Then it is directly thermoformed (i.e., aramid wet paper is obtained by wet papermaking and then dried and formed). The temperature is 200°C, the pressure is 0.5 MPa, the time is 30 minutes, and the paper basis weight is 54.8 g / m². 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0086] The thermally conductive aramid insulating paper-based material was tested for performance. The tensile strength index and thermal conductivity were 101.6 N*m / g and 0.237 W / (m*K), respectively.

[0087] Example 4

[0088] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0089] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:30:12 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2). The planetary ball mill was operated at 500 rpm for 32 h. After ball milling, the mixture was washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was completely removed. The paste obtained by vacuum filtration was ultrasonically dispersed in deionized water for 30 min and centrifuged at 4000 rpm for 30 min to remove large pieces of boron nitride. The supernatant was collected and centrifuged at 8000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Figure 2 , Figure 3 Finally, the aminoboron nitride nanosheets and N,N-dimethylacetamide were uniformly mixed and ultrasonically sonicated at 400W for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0090] (2) Preparation of thermally conductive aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of ≥99.9% and N,N-dimethylacetamide solution with a purity of ≥99.99% and a water content of ≤500ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.005; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.0mol / L solution, and then placed at -5℃. At low temperature, isophthaloyl chloride was slowly added multiple times with a stirring rate of 500 rpm. After the isophthaloyl chloride was completely added, an aminoboron nitride nanosheet suspension was added, with the amount of aminoboron nitride nanosheets being equivalent to 20% of the mass of m-phenylenediamine. The stirring speed was increased to 1000 rpm, and the reaction temperature was controlled between 30℃ and 60℃. After the rod-climbing phenomenon occurred, the reaction was continued for 4 hours. Then, an acid-binding agent Ca(OH)2 was added to adjust the pH to 7.0, and a polymer solution was obtained.

[0091] (3) Preparation of thermally conductive aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 19%, set the spinning nozzle speed to 50 cm / min, perform wet spinning, the volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50, stay in the coagulation bath for 80s, the coagulation bath temperature is 25℃, the stretching ratio is 3.3 times, and after winding, heat set at 320℃ to obtain thermally conductive aramid fiber.

[0092] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into short fibers of 6 mm. Figure 4 With the aid of a dispersant (polyethylene oxide, 0.3% of the chopped fiber mass) and water, a 0.1 wt% suspension (based on the mass of chopped fibers) was prepared in a blender at 10,000 rpm for 3 minutes. Precipitated fibers were weighed at a mass ratio of 40:60 and then dispersed in a fiber disintegrator at 1000 rpm to prepare a 0.1 wt% suspension. The chopped fiber and precipitated fiber suspensions were mixed and stirred evenly. The mixture was then wet-processed into paper, followed by pressing and dewatering at 25°C and 0.2 MPa for 5 minutes. The paper was then directly thermoformed (i.e., aramid wet paper was obtained through wet processing and then dried and formed) at 200°C, 0.5 MPa, and 30 minutes, resulting in a paper basis weight of 64.3 g / m². 2 Finally, a thermally conductive aramid insulating paper-based material was prepared. Figure 5 ).

[0093] The thermally conductive aramid insulating paper-based material was tested for performance, and its tensile strength index and thermal conductivity were 88.4 N*m / g and 0.541 W / (m*K), respectively.

[0094] Compare with Example 1

[0095] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0096] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:30:12 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2). The planetary ball mill was rotated at 500 rpm and the ball milling time was 32 h. After the ball milling was completed, the mixture was washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was clean. The paste obtained by vacuum filtration was ultrasonically dispersed in deionized water for 30 min and centrifuged at 4000 rpm for 30 min to remove large pieces of boron nitride. The supernatant was collected and centrifuged at 8000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Finally, the aminoboron nitride nanosheets and N,N-dimethylacetamide were mixed uniformly and ultrasonically sonicated at 400W power for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0097] (2) Preparation of aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of 99.9% or higher, and N,N-dimethylacetamide solution with a purity of 99.99% or higher and a water content of less than 500 ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.005; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.0 mol / L solution, and placed at a low temperature of -5℃. Isophthaloyl chloride is slowly added multiple times at a stirring rate of 500 rpm. After the isophthaloyl chloride is completely added, the stirring speed is increased to 1000 rpm. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues for 4 hours. Then, the acid-binding agent Ca(OH)2 is added to adjust the pH to 7.0 to obtain the polymer solution.

[0098] (3) Preparation of aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 19%. Set the spinning nozzle speed to 50 cm / min and perform wet spinning. The volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50. The fiber stays in the coagulation bath for 80 seconds. The coagulation bath temperature is 25℃. The stretching ratio is 3.3 times. After winding, the fiber is heat-set at 320℃ to obtain aramid fiber.

[0099] (4) Wet papermaking: The aramid fibers prepared in step (3) are cut into 6mm short fibers. With the help of dispersant (polyethylene oxide, the amount is 0.3% of the mass of the short fibers) and water, a 0.1wt% suspension is prepared in a blender at 10000rpm for 3min (based on the mass of the short fibers). The precipitated fibers were weighed according to a mass ratio of 40:60 between chopped fibers and precipitated fibers. After being disintegrated by a fiber disintegrator at 1000 rpm, the precipitated fibers were prepared into a 0.1 wt% suspension. The chopped fibers, precipitated fibers, and the aminoboron nitride nanosheet suspension prepared in step (1) were mixed. The amount of aminoboron nitride nanosheets added was equivalent to 20% of the mass of intermediate phenylenediamine in step (2). After stirring evenly, the paper was wet-processed. Then, the wet paper web was pressed and dehydrated at 25°C and 0.2 MPa for 5 min, and then directly thermoformed (i.e., aramid wet paper was obtained by wet-processing and then dried and formed). The temperature was 200°C, the pressure was 0.5 MPa, the time was 30 min, and the paper basis weight was 64.3 g / m². 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0100] The thermally conductive aramid insulating paper-based material was tested for performance, and its tensile strength index and thermal conductivity were 70.3 N*m / g and 0.271 W / (m*K), respectively.

[0101] Compare with Example 2

[0102] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0103] (1) Preparation of boron nitride nanosheet dispersion: Boron nitride nanosheets and N,N-dimethylacetamide were mixed evenly and ultrasonically for one hour at 400W using an ultrasonic cell disruptor to obtain a boron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0104] (2) Preparation of aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of 99.9% or higher, and N,N-dimethylacetamide solution with a purity of 99.99% or higher and a water content of less than 500 ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.005; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.0 mol / L solution, and placed at a low temperature of -5℃. Isophthaloyl chloride is slowly added multiple times at a stirring rate of 500 rpm. After the isophthaloyl chloride is completely added, the stirring speed is increased to 1000 rpm. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues for 4 hours. Then, the acid-binding agent Ca(OH)2 is added to adjust the pH to 7.0 to obtain the polymer solution.

[0105] (3) Preparation of aramid fiber: Adjust the solid content of the polymer solution prepared in step (2) to 19%. Set the spinning nozzle speed to 50 cm / min and perform wet spinning. The volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50. The fiber stays in the coagulation bath for 80 seconds. The coagulation bath temperature is 25℃. The stretching ratio is 3.3 times. After winding, the fiber is heat-set at 320℃ to obtain aramid fiber.

[0106] (4) Wet papermaking: The aramid fibers prepared in step (3) are cut into 6mm short fibers. With the help of dispersant (polyethylene oxide, the amount is 0.3% of the mass of the short fibers) and water, a 0.1wt% suspension is prepared in a blender at 10000rpm for 3min (based on the mass of the short fibers). The precipitated fibers were weighed according to a mass ratio of 40:60 between chopped fibers and precipitated fibers. After being disintegrated by a fiber disintegrator at 1000 rpm, the precipitated fibers were prepared into a 0.1 wt% suspension. The chopped fibers, precipitated fibers, and the boron nitride nanosheet suspension prepared in step (1) were mixed together. The amount of boron nitride nanosheets added was equivalent to 20% of the mass of intermediate phenylenediamine in step (2). After stirring evenly, the paper was wet-processed. Then, the wet paper web was pressed and dehydrated at 25°C and 0.2 MPa for 5 min, and then directly thermoformed (i.e., aramid wet paper was obtained by wet-processing and then dried and formed). The temperature was 200°C, the pressure was 0.5 MPa, the time was 30 min, and the paper basis weight was 64.3 g / m². 2Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0107] The thermally conductive aramid insulating paper-based material was tested for performance, and its tensile strength index and thermal conductivity were 66.1 N*m / g and 0.142 W / (m*K), respectively.

[0108] Compare with Example 3

[0109] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0110] (1) Preparation of aminoboron nitride nanosheets: Hexagonal boron nitride, urea and deionized water were mixed uniformly in a mass ratio of 1:30:10 and placed in an agate ball mill jar (the mass ratio of 8mm agate balls to 4mm agate balls was 1:3, and the ball-to-material ratio was 3:2). The planetary ball mill was rotated at 500 rpm and the ball milling time was 20 h. After the ball milling was completed, the mixture was washed with a large amount of deionized water and filtered under vacuum. This process was repeated several times until the urea was clean. The paste obtained by vacuum filtration was ultrasonically dispersed in deionized water for 30 min and centrifuged at 1000 rpm for 30 min to remove large pieces of boron nitride. The supernatant was collected and centrifuged at 4000 rpm for 50 min. The lower solid was collected and freeze-dried to obtain the desired aminoboron nitride nanosheets. Finally, the aminoboron nitride nanosheets and N,N-dimethylacetamide were mixed uniformly and ultrasonically sonicated at 400W power for half an hour using an ultrasonic cell disruptor to obtain an aminoboron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0111] (2) Preparation of aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of 99.9% or higher, and N,N-dimethylacetamide solution with a purity of 99.99% or higher and a water content of less than 500 ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.01; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.1 mol / L solution, and placed at a low temperature of -6℃. Isophthaloyl chloride is slowly added multiple times at a stirring rate of 500 rpm. After the isophthaloyl chloride is completely added, the stirring speed is increased to 1000 rpm. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues for 4 hours. Then, the acid-binding agent Ca(OH)2 is added to adjust the pH to 7.0 to obtain the polymer solution.

[0112] (3) Preparation of thermally conductive aramid fiber: First, add the amino boron nitride nanosheet suspension from step (1) to the polymer solution prepared in step (2). The amount of amino boron nitride nanosheet added is controlled to be 10% of the mass of m-phenylenediamine. Then, adjust the solid content of the polymer solution to 15%, set the spinning nozzle speed to 50 cm / min, and carry out wet spinning. The volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50. The fiber stays in the coagulation bath for 30 seconds. The coagulation bath temperature is 45℃, the stretching ratio is 3.7 times, and after winding, it is heat-set at 320℃ to obtain thermally conductive aramid fiber.

[0113] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into 3mm short fibers. With the help of a dispersant (polyethylene oxide, amounted to 0.3% of the mass of the short fibers) and water, a 0.1 wt% suspension is prepared by blending at 10000 rpm for 3 minutes (based on the mass of the short fibers). The precipitated fibers are weighed according to a mass ratio of 60:40 between the short fibers and the precipitated fibers. After the precipitated fibers are disintegrated by a fiber disintegrator at 1000 rpm, a 0.1 wt% suspension is prepared. The short fibers and the precipitated fiber suspension are mixed and stirred evenly. After wet papermaking, the wet paper web is pressed and dehydrated at 25°C and 0.2 MPa for 5 minutes. Then it is directly thermoformed (i.e., aramid wet paper is obtained by wet papermaking and then dried and formed). The temperature is 200°C, the pressure is 0.5 MPa, the time is 30 minutes, and the paper basis weight is 54.3 g / m². 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0114] The thermally conductive aramid insulating paper-based material was tested for performance. The tensile strength index and thermal conductivity were 73.3 N*m / g and 0.293 W / (m*K), respectively.

[0115] Compare with Example 4

[0116] A thermally conductive aramid insulating paper-based material, the preparation method of which is as follows:

[0117] (1) Preparation of boron nitride nanosheet dispersion: Boron nitride nanosheets and N,N-dimethylacetamide were mixed evenly and ultrasonically for one hour at 400W using an ultrasonic cell disruptor to obtain a boron nitride nanosheet suspension with a mass concentration of 20 mg / mL.

[0118] (2) Preparation of aramid polymer solution: m-phenylenediamine and isophthaloyl chloride with a purity of 99.9% or higher, and N,N-dimethylacetamide solution with a purity of 99.99% or higher and a water content of less than 500 ppm are used; the molar ratio of m-phenylenediamine and isophthaloyl chloride participating in the reaction is 1:1.01; the specific steps are as follows: under nitrogen atmosphere, m-phenylenediamine is first dissolved in N,N-dimethylacetamide to prepare a 1.1 mol / L solution, and placed at a low temperature of -6℃. Isophthaloyl chloride is slowly added multiple times at a stirring rate of 500 rpm. After the isophthaloyl chloride is completely added, the stirring speed is increased to 1000 rpm. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues for 4 hours. Then, the acid-binding agent Ca(OH)2 is added to adjust the pH to 7.0 to obtain the polymer solution.

[0119] (3) Preparation of thermally conductive aramid fiber: First, add the boron nitride nanosheet suspension from step (1) to the polymer solution prepared in step (2). The amount of boron nitride nanosheets added is controlled to be 10% of the mass of m-phenylenediamine. Then, adjust the solid content of the polymer solution to 15%. Set the spinning nozzle speed to 50 cm / min and perform wet spinning. The volume ratio of water and N,N-dimethylacetamide in the coagulation bath is 50:50. The fiber stays in the coagulation bath for 30 seconds. The coagulation bath temperature is 45℃. The stretching ratio is 3.7 times. After winding, heat set at 320℃ to obtain thermally conductive aramid fiber.

[0120] (4) Wet papermaking: The thermally conductive aramid fibers prepared in step (3) are cut into 3mm short fibers. With the help of a dispersant (polyethylene oxide, amounted to 0.3% of the mass of the short fibers) and water, a 0.1 wt% suspension is prepared by blending at 10000 rpm for 3 minutes (based on the mass of the short fibers). The precipitated fibers are weighed according to a mass ratio of 60:40 between the short fibers and the precipitated fibers. After the precipitated fibers are disintegrated by a fiber disintegrator at 1000 rpm, a 0.1 wt% suspension is prepared. The short fibers and the precipitated fiber suspension are mixed and stirred evenly. After wet papermaking, the wet paper web is pressed and dehydrated at 25°C and 0.2 MPa for 5 minutes. Then it is directly thermoformed (i.e., aramid wet paper is obtained by wet papermaking and then dried and formed). The temperature is 200°C, the pressure is 0.5 MPa, the time is 30 minutes, and the paper basis weight is 54.3 g / m². 2 Ultimately, a thermally conductive aramid insulating paper-based material was prepared.

[0121] The thermally conductive aramid insulating paper-based material was tested for performance. The tensile strength index and thermal conductivity were 61.4 N*m / g and 0.197 W / (m*K), respectively.

[0122] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a thermally conductive aramid insulating paper-based material, characterized in that, Includes the following steps: (1) Preparation of amino boron nitride nanosheets: Hexagonal boron nitride, urea and water were mixed and put into a ball mill for ball milling. After ball milling, excess urea was washed away with water and then ultrasonically dispersed in water. Large-sized unpeeled boron nitride was removed by centrifugation, and the lower solid layer was collected by centrifugation again and freeze-dried to obtain amino boron nitride nanosheets. (2) Preparation of thermally conductive aramid polymer solution: The amino boron nitride nanosheets obtained in step (1) and N,N-dimethylacetamide are ultrasonically mixed evenly to obtain an amino boron nitride nanosheet suspension; under a protective gas atmosphere, m-phenylenediamine is dissolved in N,N-dimethylacetamide to obtain a m-phenylenediamine solution; then, under stirring conditions of -20℃ to 0℃, isophthaloyl chloride is slowly added to the m-phenylenediamine solution multiple times, followed by the amino boron nitride nanosheet suspension, and the stirring speed is increased to carry out the polycondensation reaction. The reaction temperature is controlled between 30℃ and 60℃. After the rod climbing phenomenon occurs, the reaction continues until the reaction ends. Finally, the acid-binding agent Ca(OH)2 is added to adjust the pH to 4 to 9 to obtain a thermally conductive aramid polymer solution. (3) Preparation of thermally conductive aramid fiber: The thermally conductive aramid polymer solution obtained in step (2) is wet-spun. After being extruded by the spinning nozzle, it is solidified, stretched, wound and heat-set to obtain thermally conductive aramid fiber. (4) Wet papermaking: The thermally conductive aramid fibers obtained in step (3) are cut into short fibers, and then a dispersant and water are added to prepare a short fiber suspension; The precipitated fibers are prepared into a precipitated fiber suspension after being decomposed. The chopped fiber suspension and the precipitated fiber suspension are then stirred and mixed evenly, and then wet papermaking, pressing and dewatering, and hot pressing are performed to obtain thermally conductive aramid insulating paper-based material.

2. The method according to claim 1, characterized in that: The mass ratio of hexagonal boron nitride, urea and water in step (1) is 1-10:10-100:1-100; The molar ratio of m-phenylenediamine and isophthaloyl chloride in step (2) is 1-10:1-10; The amount of aminated boron nitride nanosheets added in step (2) is 1-200% of the mass of m-phenylenediamine; The solid content of the thermally conductive aramid polymer solution mentioned in step (3) is 1% to 50%; The mass ratio of chopped fibers to precipitated fibers in step (4) is 1-10:1-10.

3. The method according to claim 2, characterized in that: The mass ratio of hexagonal boron nitride, urea and water in step (1) is 1:30:12; The molar ratio of m-phenylenediamine and isophthaloyl chloride mentioned in step (2) is 1:1.005 to 1.01; The amount of aminated boron nitride nanosheets added in step (2) is 5-20% of the mass of m-phenylenediamine; The solid content of the thermally conductive aramid polymer solution mentioned in step (3) is 10% to 20%; The mass ratio of chopped fibers to precipitated fibers in step (4) is 3-5:5-7.

4. The method according to claim 1, characterized in that: The concentration of the aminoboron nitride nanosheet suspension mentioned in step (2) is 10-30 mg / mL; The concentration of the m-phenylenediamine solution mentioned in step (2) is 0.5–2 mol / L; The dispersant mentioned in step (4) is polyethylene oxide; The amount of dispersant added in step (4) is 0.1% to 0.5% of the mass of the chopped fibers; The concentration of the short-cut fiber suspension mentioned in step (4) is 0.01% to 10% by mass. The concentration of the precipitated fiber suspension mentioned in step (4) is 0.01 to 10% by mass.

5. The method according to claim 1, characterized in that: The wet spinning conditions described in step (3) are as follows: the nozzle extrusion speed is 10-100 cm / min; the volume ratio of water to N,N-dimethylacetamide in the coagulation bath is 1-100:1-100; the residence time in the coagulation bath is 1-500 s; the coagulation bath temperature is 20-60℃; the stretching ratio is 1.1-50 times; and the heat setting temperature is 50-600℃.

6. The method according to claim 1, characterized in that: The conditions for ball milling described in step (1) are: rotation speed 10 to 1000 rpm, ball milling time 2 to 96 h; In step (1), the conditions for centrifugation to remove large-sized unpeeled boron nitride are: rotation speed 1000-4000 rpm, centrifugation time 20-40 min; In step (1), the conditions for collecting the lower layer solid by centrifugation again are: rotation speed 4000-8000 rpm, centrifugation time 30-60 min; In step (2), the rotation speed when adding isophthaloyl chloride is 100-600 rpm; In step (2), increasing the stirring speed means increasing the stirring speed to 1000-2000 rpm.

7. The method according to claim 1, characterized in that: The ultrasonic dispersion time mentioned in step (1) is 20–40 min; The conditions for ultrasound in step (2) are: ultrasound power 300-500W, ultrasound time 20-40 min; The reaction time described in step (2) is 1 to 10 hours; The pH adjustment mentioned in step (2) is to adjust the pH to 7.0 to 7.4; The length of the chopped fibers mentioned in step (4) is 1 to 100 mm; The pressing and dehydration conditions described in step (4) are: pressing and dehydration at 25℃ and 0.2MPa pressure for 5 min; The hot pressing conditions described in step (4) are: hot pressing temperature 50-600℃, hot pressing pressure 0.01-20Mpa, and hot pressing time 0.1-48h.

8. A thermally conductive aramid insulating paper-based material, characterized in that: It is prepared by the method described in any one of claims 1 to 7.

9. The application of the thermally conductive aramid insulating paper-based material according to claim 8 in insulating materials.

10. The application of the thermally conductive aramid insulating paper-based material according to claim 8 in the fields of electrical equipment, electronic information, aerospace or automotive industries.

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