Aramid insulation paper and preparation method thereof

Abstract

The invention discloses aramid insulation paper and a preparation method thereof, and relates to the technical field of insulation materials, the aramid insulation paper comprises an aramid insulation paper sandwich layer, an aramid insulation paper upper layer and an aramid insulation paper lower layer, the aramid insulation paper sandwich layer is arranged between the aramid insulation paper upper layer and the aramid insulation paper lower layer, the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer are covered with boron nitride nanosheets, the aramid insulation paper upper layer and the aramid insulation paper lower layer are both made of aramid fibers, and the aramid insulation paper sandwich layer is made of freeze-dried aramid fibers. The technical problems that after existing aerogel and other low-thermal-conductivity-coefficient materials are used for electronic devices and power equipment, heat dissipation of a heat source is not facilitated when heat is isolated from being transmitted and diffused from a heating source to sensitive components, then the heating problem of the power equipment is aggravated, and the operation reliability of the power equipment is reduced are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of insulating materials, and in particular to aramid insulating paper and a preparation method thereof. Background Art

[0002] At present, the development trend of electronic devices and power equipment is integration, high power density and intelligence. The heat generation and heat density are increasing sharply. Intelligent core components such as sensors and processors are extremely sensitive to environmental factors such as temperature. If they work outside the allowable temperature, they are very likely to fail, shorten their lifespan or even be directly damaged. Therefore, there is an urgent need to develop an insulating paper material with excellent thermal insulation properties.

[0003] At present, the most mainstream method for preparing high-performance thermal insulation materials is to construct poor thermal conductors such as aerogels. However, when low thermal conductivity materials such as aerogels are used in electronic devices and power equipment, they are not conducive to heat dissipation when isolating heat from the heat source to sensitive components, which in turn aggravates the heating problem of power equipment and reduces the reliability of power equipment operation. Summary of the invention

[0004] The present invention provides an aramid insulation paper and a preparation method thereof, which solves the technical problem that when existing low thermal conductivity materials such as aerogel are used in electronic devices and power equipment, when heat is isolated from being transferred and diffused from a heat source to sensitive components, it is not conducive to the heat dissipation of the heat source, thereby aggravating the heating problem of the power equipment and reducing the reliability of the operation of the power equipment.

[0005] A first aspect of the present invention provides an aramid insulation paper, comprising an aramid insulation paper sandwich layer, an aramid insulation paper upper layer and an aramid insulation paper lower layer;

[0006] The aramid insulation paper sandwich layer is placed between the aramid insulation paper upper layer and the aramid insulation paper lower layer, and the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer are covered with a thermally conductive insulation network layer;

[0007] The material of the aramid insulation paper sandwich layer is freeze-dried aramid fiber.

[0008] Optionally, the materials of the upper layer of aramid insulation paper and the lower layer of aramid insulation paper are both aramid fibers;

[0009] The aramid fibers include para-aramid short-cut fibers and para-aramid pulp fibers;

[0010] The length of the para-aramid chopped fibers is 4 mm to 5 mm, and the diameter of the para-aramid chopped fibers is 8 mm. -12 ;

[0011] The dimensional length of the para-aramid pulp fiber is 0.6 mm-3 mm, and the aspect ratio of the para-aramid pulp fiber is 50-1000.

[0012] Optionally, the thermally conductive insulating network layer is a boron nitride nanosheet;

[0013] The thickness ratio of the aramid insulation paper upper layer, the aramid insulation paper sandwich layer and the aramid insulation paper lower layer is 1:(4-5):1; and / or,

[0014] The diameter of the boron nitride nanosheet is 0.5 -5 , and the thickness of the boron nitride nanosheet is 50nm-400nm.

[0015] Optionally, the boron nitride nanosheets covered on the upper surface of the upper layer of aramid insulation paper and the lower surface of the lower layer of aramid insulation paper have the same mass;

[0016] The boron nitride nanosheets covered on the upper surface of the upper layer of the aramid insulation paper are greater than or equal to a preset first mass threshold, wherein the first mass threshold is 20% of the mass of the upper layer of the aramid insulation paper;

[0017] The boron nitride nanosheets coated on the lower surface of the lower layer of the aramid insulation paper are greater than or equal to a preset second mass threshold, wherein the second mass threshold is 20% of the mass of the lower layer of the aramid insulation paper.

[0018] Optionally, the mass ratio between the para-aramid chopped fibers and the aramid fibers is 30-50%;

[0019] The mass ratio of the para-aramid pulp fiber to the aramid fiber is 50-70%.

[0020] Optionally, the aramid insulation paper has a basis weight of 60-90 g / m 2 .

[0021] A second aspect of the present invention provides a method for preparing aramid insulation paper, comprising:

[0022] Based on a preset given mass ratio, para-aramid short-cut fibers and para-aramid pulp fibers are used for fiber mixing treatment to obtain a target slurry;

[0023] The target slurry is sequentially subjected to freezing and temperature-raising drying treatments to obtain an aramid insulating paper sandwich layer;

[0024] Using the target slurry to perform vacuum filtration on the aramid insulation paper sandwich layer to obtain initial aramid insulation paper;

[0025] Spraying the previously obtained boron nitride nanosheet suspension on the upper surface and the lower surface of the initial aramid insulation paper to obtain aramid insulation rough paper;

[0026] The aramid insulation rough paper is dried and heat-pressed in sequence to obtain aramid insulation paper.

[0027] Optionally, the step of mixing para-aramid chopped fibers and para-aramid pulp fibers based on a preset given mass ratio to obtain a target slurry comprises:

[0028] Adding para-aramid chopped fibers and para-aramid pulp fibers to a first deionized water solution according to a preset given mass ratio to obtain a fiber mixed solution;

[0029] Mixing the polyethylene oxide dispersant with the fiber mixed solution to obtain a target mixed solution;

[0030] Using a fiber deflagrator to deflagrate the target mixed liquid to obtain an initial slurry;

[0031] The initial slurry is beaten by a beater to obtain the target slurry.

[0032] Optionally, the step of using the target slurry to perform vacuum filtration on the aramid insulation paper sandwich layer to obtain initial aramid insulation paper comprises:

[0033] Using the aramid insulation paper sandwich layer as a filter membrane of a Buchner funnel to obtain a first target funnel;

[0034] Using the first target funnel to perform vacuum filtration on the target slurry to obtain a second target funnel, and flipping the filter membrane of the second target funnel to obtain a third target funnel;

[0035] The target slurry is vacuum filtered using the third target funnel to obtain initial aramid insulation paper.

[0036] Optionally, the specific preparation process of the boron nitride nanosheet suspension is:

[0037] Mixing boron nitride micro-sheets, lithium citrate, isopropanol and a second deionized water solution to obtain a boron nitride dispersion, wherein the mass ratio of the boron nitride micro-sheets, the lithium citrate, the isopropanol and the second deionized water solution is 1:1:40:60;

[0038] The boron nitride dispersion is subjected to ultrasonic exfoliation treatment to obtain a first dispersion;

[0039] Performing hydrothermal treatment on the first dispersion by a hydrothermal reactor to obtain a second dispersion;

[0040] The second dispersion is filtered and washed to obtain a boron nitride nanosheet suspension.

[0041] It can be seen from the above technical solutions that the present invention has the following advantages:

[0042] 1. The present invention uses aramid fiber as the upper and lower materials of aramid insulation paper, and covers the upper and lower surfaces with a thermally conductive insulating network layer, so that the contact materials between the layers are exactly the same, thereby giving the aramid insulation paper the best interface compatibility between the layers, and improving the stability and reliability of the aramid insulation paper.

[0043] 2. By covering the upper and lower surfaces with a thermally conductive insulating network layer, a dense high thermal conductivity network is formed on the upper and lower surfaces of the aramid insulation paper, thereby improving the thermal conductivity of the aramid insulation paper along the surface direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0045] Figure 1 This is a schematic diagram of the structure of aramid insulation paper according to an embodiment of the present invention;

[0046] Figure 2 It is a schematic diagram of the test results of the surface thermal conductivity of aramid insulation paper in the embodiment of the present invention and the comparative example;

[0047] Figure 3 It is a schematic diagram of the test results of the in-plane thermal conductivity of aramid insulation paper in the embodiment of the present invention and the comparative example;

[0048] The meanings of the reference numerals are as follows:

[0049] 1. Aramid fiber; 2. Aramid fiber freeze-drying 3. Boron nitride nanosheets. DETAILED DESCRIPTION

[0050] The embodiment of the present invention provides an aramid insulation paper and a preparation method thereof, which are used to solve the technical problem that when existing low thermal conductivity materials such as aerogel are used in electronic devices and power equipment, when isolating heat from the heat source to the sensitive components, it is not conducive to the heat dissipation of the heat source, thereby aggravating the heating problem of the power equipment and reducing the reliability of the operation of the power equipment.

[0051] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] Also, see Figure 1 , the present invention provides an aramid insulation paper, comprising an aramid insulation paper sandwich layer, an aramid insulation paper upper layer and an aramid insulation paper lower layer;

[0053] The aramid insulation paper sandwich layer is placed between the aramid insulation paper upper layer and the aramid insulation paper lower layer, and the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer are covered with boron nitride nanosheets 3;

[0054] The materials of the upper layer of aramid insulation paper and the lower layer of aramid insulation paper are both aramid fiber 1;

[0055] The material of the aramid insulation paper sandwich layer is freeze-dried aramid fiber 2.

[0056] In the embodiment of the present invention, the aramid insulation paper is a sandwich structure, and the aramid insulation paper uses aramid fiber 1 as the material of the upper layer and the lower layer of aramid insulation paper, and sprays a layer of boron nitride nanosheets 3 on the upper surface of the upper layer and the lower surface of the lower layer of aramid insulation paper, and freeze-dried aramid fiber 2 is used as the sandwich layer material of the aramid insulation paper. The sandwich structure is adopted, and unlike the loose aramid fiber freeze-dried 2 of the sandwich layer material, the aramid fiber 1 in the upper and lower layers of material is densely stacked under the mechanical force of vacuum filtration, which can give the insulation paper a dense surface with high electrical strength, making up for the defect of low electrical strength caused by the loose and porous internal structure of traditional single aerogel thermal insulation paper, and meeting the application needs in advanced power electronic devices and electrical equipment.

[0057] It is worth mentioning that the preparation process of aramid insulation paper is as follows: 1. Using para-aramid chopped fiber and para-aramid pulp fiber as raw materials, mix them in a given mass ratio, freeze-dry, and prepare an aramid insulation paper sandwich layer. 2. Using para-aramid chopped fiber and para-aramid pulp fiber as raw materials, mix them in a given mass ratio to obtain upper and lower slurries. 3. Load the aramid insulation paper sandwich layer into a Buchner funnel as a vacuum filtration membrane, vacuum filter the upper and lower slurries on its surface, and then spray the boron nitride nanosheet 3 suspension on it to obtain aramid insulation paper rough paper. 4. Dry the aramid insulation paper rough paper and hot-press it into shape to obtain aramid insulation paper.

[0058] It should be noted that the aramid fiber 1 includes para-aramid short fibers and para-aramid pulp fibers; the dimension length of the para-aramid short fibers is 4-5 mm, and the wire diameter of the para-aramid short fibers is 8-12; the dimension length of the para-aramid pulp fibers is 0.6-3 mm, and the aspect ratio of the para-aramid pulp fibers is 50-1000.

[0059] In the embodiment of the present invention, the aramid fiber 1 includes para-aramid short fibers and para-aramid pulp fibers. The dimension length of the para-aramid short fibers is 4-5 mm, and the wire diameter of the para-aramid short fibers is 8-12. When the aramid insulation paper is prepared, it can be distributed more evenly in the matrix material, and will not cause entanglement or agglomeration due to excessive length, thereby ensuring the dimensional stability of the aramid insulation paper prepared under different environments. The dimension length of the para-aramid pulp fibers is 0.6-3 mm, and the aspect ratio of the para-aramid pulp fibers is 50-1000, which can make the para-aramid pulp fibers better combined with other materials and enhance the overall performance of the paper.

[0060] It should be noted that the thickness ratio between the aramid insulation paper upper layer, the aramid insulation paper sandwich layer and the aramid insulation paper lower layer is 1:(4-5):1; the diameter of the boron nitride nanosheet 3 is 0.5-5, and the thickness of the boron nitride nanosheet 3 is 50-400 nm.

[0061] In the embodiment of the present invention, the thickness ratio between the aramid insulation paper upper layer, the aramid insulation paper sandwich layer and the aramid insulation paper lower layer is 1: (4-5): 1, the boron nitride nanosheet 3 has a sheet diameter of 0.5-5, and the thickness of the boron nitride nanosheet 3 is 50-400nm, which is conducive to forming a good interface with the aramid fiber 1. Its relatively thin thickness (50-400nm) enables it to fit tightly on the surface of the aramid fiber 1. When the sheet diameter is 0.5-5 microns, it can achieve good coverage on the surface of the aramid fiber 1.

[0062] It should be noted that the boron nitride nanosheets 3 covered on the upper surface of the upper layer of aramid insulation paper and the lower surface of the lower layer of aramid insulation paper have the same mass; the boron nitride nanosheets covered on the upper surface of the upper layer of aramid insulation paper are greater than or equal to a preset first mass threshold, wherein the first mass threshold is 20% of the mass of the upper layer of aramid insulation paper; the boron nitride nanosheets covered on the lower surface of the lower layer of aramid insulation paper are greater than or equal to a preset second mass threshold, wherein the second mass threshold is 20% of the mass of the lower layer of aramid insulation paper.

[0063] In the embodiment of the present invention, the mass of the boron nitride nanosheets 3 covered on the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer is the same, and the mass of the boron nitride nanosheets 3 covered on the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer is greater than or equal to 20% of the mass of the aramid insulation paper upper layer and the aramid insulation paper lower layer. The thermal conductivity and insulation of the aramid insulation paper are improved.

[0064] It should be noted that the mass ratio of the para-aramid short fibers to the aramid fibers 1 is 30-50%; the mass ratio of the para-aramid pulp fibers to the aramid fibers 1 is 50-70%.

[0065] In the embodiment of the present invention, the mass ratio of the para-aramid short fibers to the aramid fibers 1 is 30-50%, and the mass ratio of the para-aramid pulp fibers to the aramid fibers 1 is 50-70%. This helps to build a stable fiber network.

[0066] The raw materials and reagents involved in the embodiments of the present invention are all commercially available.

[0067] Embodiment 1:

[0068] Embodiment 1 of the present invention is a method for preparing directional heat-conducting and heat-insulating aramid insulation paper, comprising the following steps:

[0069] S101. Using para-aramid chopped fibers and para-aramid pulp fibers as raw materials, mixing them in a given mass ratio, and freeze-drying them to prepare an aramid insulation paper sandwich layer.

[0070] Furthermore, S101 includes the following sub-steps:

[0071] S11, adding finished para-aramid short fibers with a length of 4-5 mm and a wire diameter of 8-12 and finished para-aramid pulp fibers with a length of 0.6-3 mm and an aspect ratio of about 600 into an appropriate amount of deionized water at a mass ratio of 4:6, and adding a certain amount of polyethylene oxide (PEO) dispersant;

[0072] S12, after being deflated by a standard fiber deflagrator at 18000 r, a high-speed pulping machine is used to beat the pulp at a speed of 18000 rpm for 20 min until it becomes a uniform pulp.

[0073] S13, then spread the slurry on a horizontal substrate, and control the amount of slurry according to the content of aramid fiber in the slurry so that the final paper quantity meets the requirements.

[0074] S102, using para-aramid short-cut fibers and para-aramid pulp fibers as raw materials, mixing them in a given mass ratio to obtain upper and lower slurries.

[0075] It is worth mentioning that the aramid insulation paper provided by the present invention uses freeze-dried aramid fibers as the sandwich layer of the aramid insulation paper. Since the freeze-dried aramid fibers are subjected to freeze-drying treatment, the aramid insulation paper has high thermal insulation performance along the thickness direction.

[0076] Further, S102 includes the following sub-steps:

[0077] S21, adding finished para-aramid short fibers with a length of 4-5 mm and a wire diameter of 8-12 and finished para-aramid pulp fibers with a length of 0.6-3 mm and an aspect ratio of about 600 into an appropriate amount of deionized water at a mass ratio of 4:6, and adding a certain amount of polyethylene oxide (PEO) dispersant;

[0078] S22. After being defibrated by a standard fiber defibrator at 18,000 r, a high-speed pulping machine is used to beat the fiber at a speed of 18,000 rpm for 20 min until it becomes a uniform pulp, thereby obtaining the upper and lower layer material pulps.

[0079] S103, use the aramid insulation paper sandwich layer prepared in step S101 as a vacuum filtration membrane to load it into a Büchner funnel, vacuum filter the upper material slurry prepared in step S102 until it is slightly moist, turn over the aramid insulation paper sandwich layer material, and use the same method to vacuum filter the lower material slurry prepared in step S102 until it is slightly moist.

[0080] Furthermore, S103 includes the following sub-steps:

[0081] S31. Load the aramid insulation paper sandwich layer as a vacuum filtration membrane into the Büchner funnel, turn on the vacuum pump, slowly introduce the upper material slurry prepared in step S102 into the Büchner funnel, and stir it slightly with a glass rod. Wait until the upper material slurry is filtered until it is slightly moist, then carefully remove the filter membrane and then turn the filter membrane over.

[0082] S32. Use the same method to filter the lower material slurry on the other side of the sandwich layer until it is slightly moist, and carefully remove the filter membrane.

[0083] S104, preparing a boron nitride nanosheet suspension, spraying the boron nitride nanosheet suspension onto the surface of the aramid insulation paper with aramid slurry filtered on both the upper and lower surfaces obtained in step S103, to obtain aramid insulation paper rough paper.

[0084] Furthermore, S104 includes the following sub-steps:

[0085] S41, adding boron nitride micro-flakes, lithium citrate, and isopropanol into deionized water and fully mechanically stirring to obtain a boron nitride dispersion, wherein the mass ratio of boron nitride micro-flakes, lithium citrate, isopropanol, and deionized water is 1:1:40:60;

[0086] S42. Ultrasonic stripping of the boron nitride dispersion in a water bath for 6 h, wherein the ultrasonic power is 600 W.

[0087] S43, the dispersion after ultrasonic stripping was placed in a hydrothermal reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180°C for 24 h.

[0088] S44. After the hydrothermal reaction is completed, the dispersion is repeatedly filtered and washed with deionized water until the pH value of the dispersion is 7, thereby obtaining a boron nitride nanosheet suspension.

[0089] S45, spraying the boron nitride nanosheet suspension onto the surface of the material prepared in step S103 to obtain aramid insulation paper.

[0090] It should be noted that the relevant process parameters are adjusted during the spraying process so that the suspension sprayed on the surface of the material neither gathers into water droplets nor flows down in strands, and the mass of the boron nitride nanosheets in the boron nitride nanosheet suspension sprayed on each side is 30% of the mass of the aramid fibers in the surface material.

[0091] It is worth mentioning that the aramid fibers in the upper layer and the lower layer of aramid insulation paper are densely stacked through vacuum filtration, which improves the electrical strength of the aramid insulation paper. Compared with the traditional single aerogel thermal insulation paper, the present invention uses the mechanical force of vacuum filtration to densely stack the materials between the layers of aramid insulation paper, thereby overcoming the technical problem of low electrical strength caused by the loose and porous internal structure.

[0092] S105, drying the rough aramid insulation paper, and then hot-pressing it at a given temperature and pressure to obtain aramid insulation paper.

[0093] Further, S105 specifically includes: placing the aramid insulation paper rough paper prepared in step S104 in a hot plate of a hot press, hot pressing for 10 min under a hot pressing temperature of 180°C and a pressure of 14 MPa, and obtaining the aramid insulation paper after cooling.

[0094] Comparative Example 1

[0095] Compared with Example 1, the difference between this comparative example and Example 1 is that in step S101, freeze-drying technology is not used to prepare the aramid insulation paper sandwich layer. Only para-aramid chopped fibers and para-aramid pulp fibers are used as raw materials, mixed in a given mass ratio, and vacuum filtered on a PVDF filter membrane to obtain the sandwich layer material, and the other steps remain unchanged.

[0096] Comparative Example 2

[0097] Compared with Example 1, this comparative example is different in that step S104 is not included (ie, the boron nitride nanosheet suspension is not sprayed on the surface of the aramid insulation paper), and the other steps remain unchanged.

[0098] Comparative Example 3

[0099] Comparative Example 3 only includes the following steps: using para-aramid chopped fibers and para-aramid pulp fibers as raw materials, mixing them in a given mass ratio, vacuum filtering them on a PVDF filter membrane to obtain a single homogeneous aramid insulation paper, and then drying and hot pressing them using the method described in step S105.

[0100] Performance Testing

[0101] See also Figure 2 As shown, by comparing the surface thermal conductivity of the aramid insulation paper in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be known that in Example 1 and Comparative Example 1, a boron nitride nanosheet suspension is sprayed on the surface of the aramid insulation paper. Compared with the aramid insulation paper in Comparative Example 2 and Comparative Example 3, this treatment method significantly improves the surface thermal conductivity of the insulation paper material. The increase in surface thermal conductivity means that the material can conduct heat more effectively in the surface direction, so that the aramid insulation paper in Example 1 and Comparative Example 1 obtains very good surface thermal conductivity. This result shows that spraying a boron nitride nanosheet suspension on the surface of aramid insulation paper can improve the surface thermal conductivity of aramid insulation paper.

[0102] See also Figure 3 As shown, by comparing the in-plane thermal conductivity of the aramid insulation paper in Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3, it can be seen that in Example 1 and Comparative Example 2, a high-porosity sandwich layer material is constructed using freeze-drying technology. Compared with the aramid insulation paper in Comparative Example 1 and Comparative Example 3, this treatment method greatly reduces the thermal conductivity of the insulation paper material along the thickness direction, so that the aramid insulation paper has excellent thermal insulation performance along the thickness direction. This result shows that the high-porosity sandwich layer material constructed using freeze-drying technology can improve the thermal insulation performance of the aramid insulation paper along the thickness direction.

[0103] See also Figure 2 and Figure 3 As shown, from the thermal conductivity performance parameters in Example 1 and Comparative Example 3, it can be seen that the single homogeneous aramid insulation paper in Comparative Example 3 exhibits basically consistent thermal conductivity along the surface direction and along the thickness direction, while the thermal conductivity of the aramid insulation paper along the surface direction in Example 1 of the present invention is about 37.3 times that along the thickness direction. Compared with the traditional single homogeneous aramid insulation paper in Comparative Example 3, it exhibits extremely outstanding directional thermal conduction and insulation characteristics, and can better meet the thermal management requirements of power equipment.

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. Aramid insulation paper, characterized in that: It includes an aramid insulation paper sandwich layer, an aramid insulation paper upper layer and an aramid insulation paper lower layer; The aramid insulation paper sandwich layer is placed between the aramid insulation paper upper layer and the aramid insulation paper lower layer, and the upper surface of the aramid insulation paper upper layer and the lower surface of the aramid insulation paper lower layer are covered with a thermally conductive insulation network layer; The material of the aramid insulation paper sandwich layer is freeze-dried aramid fiber.

2. The aramid insulation paper according to claim 1, characterized in that: The materials of the upper layer of aramid insulation paper and the lower layer of aramid insulation paper are both aramid fibers; The aramid fibers include para-aramid short-cut fibers and para-aramid pulp fibers; The length of the para-aramid chopped fibers is 4 mm to 5 mm, and the diameter of the para-aramid chopped fibers is 8 mm. -12 ; The dimensional length of the para-aramid pulp fiber is 0.6 mm-3 mm, and the aspect ratio of the para-aramid pulp fiber is 50-1000.

3. The aramid insulation paper according to claim 1, characterized in that: The thermally conductive insulating network layer is a boron nitride nanosheet; The thickness ratio between the upper layer of aramid insulation paper, the sandwich layer of aramid insulation paper and the lower layer of aramid insulation paper is 1:(4-5):1; and / or, The diameter of the boron nitride nanosheet is 0.5 -5 , and the thickness of the boron nitride nanosheet is 50nm-400nm.

4. The aramid insulation paper according to claim 3, characterized in that: The boron nitride nanosheets covered on the upper surface of the upper layer of the aramid insulation paper and the lower surface of the lower layer of the aramid insulation paper have the same mass; The boron nitride nanosheets covered on the upper surface of the upper layer of the aramid insulation paper are greater than or equal to a preset first mass threshold, wherein the first mass threshold is 20% of the mass of the upper layer of the aramid insulation paper; The boron nitride nanosheets coated on the lower surface of the lower layer of the aramid insulation paper are greater than or equal to a preset second mass threshold, wherein the second mass threshold is 20% of the mass of the lower layer of the aramid insulation paper.

5. The aramid insulation paper according to claim 2, characterized in that: The mass ratio between the para-aramid chopped fibers and the aramid fibers is 30-50%; The mass ratio of the para-aramid pulp fiber to the aramid fiber is 50-70%.

6. The aramid insulation paper according to claim 1, characterized in that: The aramid insulation paper has a basis weight of 60-90 g / m 2 .

7. A method for preparing aramid insulation paper according to any one of claims 1 to 6, characterized in that: include: Based on a preset given mass ratio, para-aramid short-cut fibers and para-aramid pulp fibers are used for fiber mixing treatment to obtain a target slurry; The target slurry is sequentially subjected to freezing and temperature-raising drying treatments to obtain an aramid insulating paper sandwich layer; Using the target slurry to perform vacuum filtration on the aramid insulation paper sandwich layer to obtain initial aramid insulation paper; Spraying the previously obtained boron nitride nanosheet suspension on the upper surface and the lower surface of the initial aramid insulation paper to obtain aramid insulation rough paper; The aramid insulation rough paper is dried and heat-pressed in sequence to obtain aramid insulation paper.

8. The method for preparing aramid insulation paper according to claim 7, characterized in that: The step of mixing the para-aramid chopped fibers and the para-aramid pulp fibers based on a preset given mass ratio to obtain the target slurry comprises: Adding para-aramid chopped fibers and para-aramid pulp fibers to a first deionized water solution according to a preset given mass ratio to obtain a fiber mixed solution; Mixing the polyethylene oxide dispersant with the fiber mixed solution to obtain a target mixed solution; Using a fiber deflagrator to deflagrate the target mixed liquid to obtain an initial slurry; The initial slurry is beaten by a beater to obtain the target slurry.

9. The method for preparing aramid insulation paper according to claim 7, characterized in that: The step of using the target slurry to perform vacuum filtration on the aramid insulation paper sandwich layer to obtain initial aramid insulation paper comprises: Using the aramid insulation paper sandwich layer as a filter membrane of a Buchner funnel to obtain a first target funnel; Using the first target funnel to perform vacuum filtration on the target slurry to obtain a second target funnel, and flipping the filter membrane of the second target funnel to obtain a third target funnel; The target slurry is vacuum filtered using the third target funnel to obtain initial aramid insulation paper.

10. The method for preparing aramid insulation paper according to claim 7, characterized in that: The specific preparation process of the boron nitride nanosheet suspension is as follows: Mixing boron nitride micro-sheets, lithium citrate, isopropanol and a second deionized water solution to obtain a boron nitride dispersion, wherein the mass ratio of the boron nitride micro-sheets, the lithium citrate, the isopropanol and the second deionized water solution is 1:1:40:60; The boron nitride dispersion is subjected to ultrasonic exfoliation treatment to obtain a first dispersion; Performing hydrothermal treatment on the first dispersion by a hydrothermal reactor to obtain a second dispersion; The second dispersion is filtered and washed to obtain a boron nitride nanosheet suspension.

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