Aramid insulation paper and a method for producing the same

Abstract

The application discloses aramid insulation paper and a preparation method thereof, relates to the technical field of insulating materials, and comprises an aramid insulation paper sandwich layer, an upper aramid insulation paper layer and a lower aramid insulation paper layer; the aramid insulation paper sandwich layer is arranged between the upper aramid insulation paper layer and the lower aramid insulation paper layer; the upper surface of the upper aramid insulation paper layer and the lower surface of the lower aramid insulation paper layer are covered with boron nitride nanosheets; the material of the upper aramid insulation paper layer and the lower aramid insulation paper layer is aramid fiber; and the material of the aramid insulation paper sandwich layer is aramid fiber lyophilized. The application solves the technical problem that, after existing aerogel and other low-thermal-conductivity materials are used in electronic devices and power equipment, the heat source is not conducive to heat dissipation when heat is transferred and diffused from the heat source to sensitive components, thereby exacerbating the heating problem of the power equipment and reducing the reliability of the operation of the power equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of insulating materials, and particularly relates to an aramid insulating paper and a preparation method thereof. BACKGROUND

[0002] Current electronic devices and power equipment are integrated, high power density, intelligent and other development trend, the heat and heat density increases sharply, and the sensor, processor and other intelligent core components are extremely sensitive to temperature and other environmental factors, and work outside the allowable temperature, which may cause failure, shortened life or even direct damage, and thus, it is urgent to develop an insulating paper material with excellent heat insulation performance.

[0003] At present, constructing thermal bad conductors such as aerogels is the most mainstream method for preparing high-performance thermal insulation materials. However, when the low thermal conductivity materials such as aerogels are used in electronic devices and power equipment, it is not conducive to heat dissipation of the heat source when the heat is isolated from the heat source to the sensitive components, and thus, the heat problem of the power equipment is aggravated, and the reliability of the power equipment operation is reduced. SUMMARY

[0004] The present application provides an aramid insulating paper and a preparation method thereof, which solves the technical problem that the low thermal conductivity materials such as aerogels are used in electronic devices and power equipment, and when the heat is isolated from the heat source to the sensitive components, it is not conducive to heat dissipation of the heat source, and thus, the heat problem of the power equipment is aggravated, and the reliability of the power equipment operation is reduced.

[0005] The present application provides an aramid insulating paper and a preparation method thereof, which solves the technical problem that the low thermal conductivity materials such as aerogels are used in electronic devices and power equipment, and when the heat is isolated from the heat source to the sensitive components, it is not conducive to heat dissipation of the heat source, and thus, the heat problem of the power equipment is aggravated, and the reliability of the power equipment operation is reduced.

[0006] The aramid insulating paper sandwich layer is arranged between the aramid insulating paper upper layer and the aramid insulating paper lower layer, and the upper surface of the aramid insulating paper upper layer and the lower surface of the aramid insulating paper lower layer are covered with a heat-conducting insulating network layer.

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

[0008] Optionally, the materials of the aramid insulating paper upper layer and the aramid insulating paper lower layer are aramid fibers.

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

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

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

[0012] Optionally, the heat-conducting and insulating network layer is boron nitride nanosheet;

[0013] 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; and / or,

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

[0015] Optionally, the mass of the boron nitride nanosheet coated 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;

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

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

[0018] Optionally, the mass ratio between the para-aramid short-cut fiber and the aramid fiber is 30-50%;

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

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

[0021] The second aspect of the present application provides a preparation method of aramid insulation paper, comprising:

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

[0023] The target slurry is sequentially subjected to freezing and temperature rising drying treatment to obtain an aramid insulation paper sandwich layer;

[0024] The target slurry is used for vacuum filtration operation on the aramid insulation paper sandwich layer to obtain an initial aramid insulation paper;

[0025] Spray the pre-acquired 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] Subsequently, the aramid insulation rough paper is subjected to drying and hot pressing to obtain aramid insulation paper.

[0027] Optionally, the step of mixing the para-aramid short-cut fiber and the para-aramid pulp fiber according to the preset given mass ratio to obtain the target slurry comprises:

[0028] The para-aramid short-cut fiber and the para-aramid pulp fiber are added to the first deionized water solution according to the preset given mass ratio to obtain a fiber mixture;

[0029] The polyethylene oxide dispersant is mixed with the fiber mixture to obtain a target mixture;

[0030] The target mixture is subjected to a defibrillation operation using a fiber defibrillator to obtain an initial slurry;

[0031] The initial slurry is subjected to a beating operation using a beater to obtain a target slurry.

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

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

[0034] The target slurry is subjected to vacuum filtration using the first target funnel to obtain a second target funnel, and the filter membrane of the second target funnel is turned over to obtain a third target funnel;

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

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

[0037] The boron nitride microparticles, lithium citrate, isopropyl alcohol, and a second deionized water solution are mixed to obtain a boron nitride dispersion, wherein the mass ratio between the boron nitride microparticles, the lithium citrate, the isopropyl alcohol, and the second deionized water solution is 1:1:40:60;

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

[0039] The first dispersion is subjected to hydrothermal treatment in a hydrothermal kettle to obtain a second dispersion;

[0040] The second dispersion liquid is subjected to a filtration cleaning operation to obtain a boron nitride nanosheet suspension.

[0041] From the above technical solutions, the present application has the following advantages:

[0042] 1、The aramid fiber is used as the upper layer material and the lower layer material of the aramid insulation paper, and a heat-conducting insulation network layer is arranged on the upper surface and the lower surface, so that the contact materials between the layers are completely the same, thereby the best interface compatibility between the layers of the aramid insulation paper is given, and the stability and reliability of the aramid insulation paper are improved.

[0043] 2、The heat-conducting insulation network layer arranged on the upper surface and the lower surface forms a dense high-thermal-conductivity network on the upper and lower surfaces of the aramid insulation paper, thereby the thermal conductivity performance of the aramid insulation paper in the surface direction is improved. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below, and obviously, the drawings in the following description can be used to obtain other drawings without creative labor by those skilled in the art.

[0045] Figure 1 It is a structural schematic diagram of the aramid insulation paper of the embodiment of the present application.

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

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

[0048] In the drawings, the meanings of the reference signs are as follows:

[0049] 1、Aramid fiber; 2、Aramid fiber freeze-dried 3、Boron nitride nanosheet. DETAILED DESCRIPTION

[0050] The embodiment of the present application provides an aramid insulation paper and a preparation method thereof, and is used to solve the technical problem that after the existing aerogel and other low-thermal-conductivity materials are used in electronic devices and power equipment, the heat source is not conducive to heat dissipation when heat is transmitted and diffused from the heat source to sensitive components, thereby exacerbating the heating problem of the power equipment and reducing the reliability of the operation of the power equipment.

[0051] In order to make the application purposes, features and advantages of the present application more obvious and easy to understand, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the following described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0052] In addition, referring to Figure 1 The present application provides an aramid insulation paper, which comprises 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 arranged 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 aramid insulation paper upper layer and the aramid insulation paper lower layer are aramid fibers 1.

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

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

[0057] It is worth mentioning that the preparation process of the aramid insulation paper is as follows: 1. Using para-aramid short-cut fibers and para-aramid pulp fibers as raw materials, mixing according to a given mass ratio, freeze-drying, and obtaining an aramid insulation paper sandwich layer. 2. Using para-aramid short-cut fibers and para-aramid pulp fibers as raw materials, mixing according to a given mass ratio, obtaining upper and lower slurries. 3. The aramid insulation paper sandwich layer is used as a vacuum filtration membrane and is loaded into a Buchner funnel, and after vacuum filtration of the upper and lower slurries on the surface, boron nitride nanosheet 3 suspension is sprayed, and aramid insulation paper rough paper is obtained. 4. The aramid insulation paper rough paper is dried and hot-pressed to obtain aramid insulation paper.

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

[0059] In the embodiment of the present application, the aramid fiber 1 includes para-aramid short-cut fiber and para-aramid pulp fiber, the length of the para-aramid short-cut fiber is 4-5 mm, and the diameter of the para-aramid short-cut fiber is 8-12, which can be more evenly distributed in the base material during the preparation of aramid insulation paper, and will not cause winding or agglomeration due to excessive length, thereby ensuring the dimensional stability of the aramid insulation paper prepared in different environments. The length of the para-aramid pulp fiber is 0.6-3 mm, and the length-width ratio of the para-aramid pulp fiber is 50-1000, which can make the para-aramid pulp fiber better combined with other materials and enhance the overall performance of the paper.

[0060] It should be noted that 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; the flake 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 application, 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, the flake diameter of the boron nitride nanosheet 3 is 0.5-5, and the thickness of the boron nitride nanosheet 3 is 50-400 nm, which is conducive to forming a good interface combination with the aramid fiber 1. Its relatively thin thickness (50-400 nm) makes it closely fit on the surface of the aramid fiber 1. When the flake diameter is 0.5-5 microns, better coverage on the surface of the aramid fiber 1 can be achieved.

[0062] It should be noted that the mass of the boron nitride nanosheet 3 coated on the upper surface of the upper layer of aramid insulation paper and the lower surface of the lower layer of aramid insulation paper is the same; the mass of the boron nitride nanosheet coated on the upper surface of the upper layer of aramid insulation paper is 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 mass of the boron nitride nanosheet coated on the lower surface of the lower layer of aramid insulation paper is 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 application, the mass of the boron nitride nanosheet 3 coated on the upper surface of the upper layer of aramid insulation paper and the lower surface of the lower layer of aramid insulation paper is the same, and the mass of the boron nitride nanosheet 3 coated on the upper surface of the upper layer of aramid insulation paper and the lower surface of the lower layer of aramid insulation paper is greater than or equal to 20% of the mass of the upper layer of aramid insulation paper and the lower layer of aramid insulation paper. The thermal conductivity and insulation of the aramid insulation paper are improved.

[0064] It should be noted that the mass ratio between the para-aramid short-cut fiber and the aramid fiber 1 is 30-50%; the mass ratio between the para-aramid pulp fiber and the aramid fiber 1 is 50-70%.

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

[0066] The raw materials and reagents involved in the embodiment of the present application are commercially available.

[0067] Example 1:

[0068] The embodiment one of the present application is a preparation method of a directional heat-conducting and heat-insulating aramid insulation paper, comprising the following steps:

[0069] S101, using para-aramid short-cut fiber and para-aramid pulp fiber as raw materials, mixing according to a given mass ratio, freeze-drying, to prepare a aramid insulation paper sandwich layer.

[0070] Further, S101 comprises the following sub-steps:

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

[0072] S12, after 18000 r of defibration by a standard fiber defibrator, using a high-speed beater to beat for 20 min at a speed of 18000 rpm to present a uniform pulp.

[0073] S13, then laying the pulp on a horizontal base plate, controlling the amount of pulp solution according to the content of aramid fiber in the pulp, so that the basis weight of the final paper meets the requirements.

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

[0075] It is worth mentioning that the aramid insulation paper provided by the application uses aramid fiber freeze-dried as the aramid insulation paper sandwich layer, and the aramid fiber freeze-dried is subjected to freeze-drying treatment, so that the aramid insulation paper has high heat insulation performance in the thickness direction.

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

[0077] S21, the finished para-aramid short-cut fiber with a length of 4-5 mm and a filament diameter of 8-12 and the finished para-aramid pulp fiber with a length of 0.6-3 mm and an aspect ratio of about 600 are added into a proper amount of deionized water in a mass ratio of 4:6, and a certain amount of polyethylene oxide (PEO) dispersant is added;

[0078] S22, after being defibrated by a standard fiber defibrator at 18000 r, the pulp is beaten by a high-speed beater at a speed of 18000 rpm for 20 min to present a uniform pulp, that is, the upper layer and lower layer material slurries are obtained.

[0079] S103, the aramid insulation paper sandwich layer prepared in step S101 is used as a vacuum filtration filter membrane and is loaded into a Buchner funnel, the upper layer material slurry prepared in step S102 is vacuum filtered to be slightly wet, the aramid insulation paper sandwich layer material is turned over, and the lower layer material slurry prepared in step S102 is vacuum filtered to be slightly wet by using the same method.

[0080] Further, S103 comprises the following sub-steps:

[0081] S31, the aramid insulation paper sandwich layer is used as a vacuum filtration filter membrane and is loaded into a Buchner funnel, a vacuum pump is opened, the upper layer material slurry prepared in step S102 is slowly introduced into the Buchner funnel, and a glass rod is slightly stirred, the filter membrane is carefully taken out when the upper layer material slurry is filtered to be slightly wet, and then the filter membrane is turned over.

[0082] S32, the lower layer material slurry is filtered on the other side of the sandwich layer to be slightly wet by using the same method, and the filter membrane is carefully taken out.

[0083] S104, a boron nitride nanosheet suspension is prepared, the aramid insulation paper with aramid pulp on the upper and lower surfaces filtered in step S103 is sprayed with the boron nitride nanosheet suspension, and aramid insulation paper rough paper is obtained.

[0084] Further, S104 comprises the following sub-steps:

[0085] S41, boron nitride microparticles, lithium citrate, isopropyl alcohol and deionized water are added and fully mechanically stirred to obtain a boron nitride dispersion, wherein the mass ratio of the boron nitride microparticles, lithium citrate, isopropyl alcohol and deionized water is 1:1:40:60;

[0086] S42. The boron nitride dispersion was ultrasonically exfoliated in a water bath for 6 h, wherein the ultrasonic power was 600 W.

[0087] S43. The ultrasonically exfoliated dispersion was placed in a hydrothermal reactor lined with polytetrafluoroethylene and hydrothermally reacted 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 of the dispersion is 7, and then the boron nitride nanosheet suspension is obtained.

[0089] S45. Spray boron nitride nanosheet suspension onto the surface of the material prepared in step S103 to obtain aramid insulating paper rough paper.

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

[0091] It is worth mentioning that by using vacuum filtration to densely stack the aramid fibers in the upper and lower layers of the aramid insulating paper, the electrical strength of the aramid insulating paper is improved. Compared with traditional single aerogel thermal insulation paper, this invention uses the mechanical force of vacuum filtration to densely stack the materials between the various layers of the aramid insulating paper, overcoming the technical problem of low electrical strength caused by the loose and porous internal structure.

[0092] S105. Dry the aramid insulating paper rough paper, and then hot press it at a given temperature and pressure to obtain aramid insulating paper.

[0093] Further, S105 specifically involves placing the aramid insulating paper rough paper prepared in step S104 into the hot electrode of a hot press, hot pressing it for 10 minutes at a hot pressing temperature of 180°C and a pressure of 14 MPa, and then cooling it to obtain the aramid insulating paper.

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that the freeze-drying technology is not used to prepare the aramid insulating paper sandwich layer in step S101. Instead, para-aramid short-cut 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. The remaining steps remain unchanged.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that step S104 (i.e., boron nitride nanosheet suspension is not sprayed onto the surface of the aramid insulating paper) is not included, while the other steps remain the same.

[0098] Comparative Example 3

[0099] Comparative Example 3 only includes the following steps: using para-aramid short-cut 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 insulating paper rough paper, and then drying and hot pressing it using the method described in step S105.

[0100] Performance testing

[0101] See Figure 2 As shown, by comparing the surface thermal conductivity of aramid insulating 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 1, the surface of the aramid insulating paper was coated with a boron nitride nanosheet suspension. This treatment significantly improves the surface thermal conductivity of the insulating paper material compared to the aramid insulating paper in Comparative Example 2 and Comparative Example 3. The increased surface thermal conductivity means that the material can conduct heat more effectively in the surface direction, thus giving the aramid insulating paper in Example 1 and Comparative Example 1 excellent surface thermal conductivity. This result indicates that coating the surface of aramid insulating paper with a boron nitride nanosheet suspension can improve the surface thermal conductivity of aramid insulating paper.

[0102] See Figure 3 As shown, by comparing the in-plane thermal conductivity of aramid insulating 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, the high-porosity sandwich layer material constructed using freeze-drying technology significantly reduces the thermal conductivity of the insulating paper material along the thickness direction compared to the aramid insulating paper in Comparative Example 1 and Comparative Example 3, giving the aramid insulating paper excellent thermal insulation performance along the thickness direction. This result demonstrates that the high-porosity sandwich layer material constructed using freeze-drying technology can improve the thermal insulation performance of aramid insulating paper along the thickness direction.

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

[0104] The above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some technical features can be replaced by equivalent features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An aramid insulating paper, characterized in that, It includes an aramid insulating paper core layer, an aramid insulating paper upper layer, and an aramid insulating paper lower layer; The aramid insulating paper sandwich layer is placed between the upper aramid insulating paper layer and the lower aramid insulating paper layer, and the upper surface of the upper aramid insulating paper layer and the lower surface of the lower aramid insulating paper layer are covered with a thermally conductive insulating network layer; The material of the aramid insulating paper sandwich layer is freeze-dried aramid fiber. Both the upper and lower layers of the aramid insulating paper are made of aramid fiber. The aramid fibers include para-aramid chopped fibers and para-aramid pulp fibers; The thermally conductive and insulating network layer is boron nitride nanosheets; The specific method for preparing the aramid insulating paper is as follows: Based on a preset given mass ratio, para-aramid short-cut fibers and para-aramid pulp fibers are mixed to obtain the target pulp. The target slurry is subjected to freezing and heating drying processes in sequence to obtain an aramid insulating paper sandwich layer; The target slurry was used to perform a vacuum filtration operation on the aramid insulating paper sandwich layer to obtain the initial aramid insulating paper. The pre-obtained boron nitride nanosheet suspension was sprayed onto the upper and lower surfaces of the initial aramid insulating paper to obtain rough aramid insulating paper. The aramid insulating rough paper is sequentially dried and hot-pressed to obtain aramid insulating paper. The step of performing vacuum filtration on the aramid insulating paper sandwich layer using the target slurry to obtain the initial aramid insulating paper includes: Using the aramid insulating paper sandwich layer as the filter membrane of the Buchner funnel, a first target funnel is obtained; The target slurry is vacuum filtered using the first target funnel to obtain a second target funnel, and the filter membrane of the second target funnel is flipped to obtain a third target funnel. The target slurry is vacuum filtered using the third target funnel to obtain initial aramid insulating paper.

2. The aramid insulating paper according to claim 1, characterized in that, The length of the para-aramid chopped fibers is 4mm-5mm, and the diameter of the para-aramid chopped fibers is 8mm. -12 ; The 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 insulating paper according to claim 1, characterized in that, The thickness ratio between the upper aramid insulating paper layer, the sandwich aramid insulating paper layer, and the lower aramid insulating paper layer is 1:(4-5):1; and / or, The boron nitride nanosheets have a diameter of 0.5 mm. -5 Furthermore, the thickness of the boron nitride nanosheets is 50nm-400nm.

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

5. The aramid insulating paper according to claim 2, characterized in that, The mass ratio of the para-aramid chopped fibers to 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 insulating paper according to claim 1, characterized in that, The basis weight of the aramid insulating paper is 60-90 g / m². 2 .

7. A method for preparing aramid insulating paper as described in any one of claims 1-6, characterized in that, include: Based on a preset given mass ratio, para-aramid short-cut fibers and para-aramid pulp fibers are mixed to obtain the target pulp. The target slurry is subjected to freezing and heating drying processes in sequence to obtain an aramid insulating paper sandwich layer; The target slurry was used to perform a vacuum filtration operation on the aramid insulating paper sandwich layer to obtain the initial aramid insulating paper. The pre-obtained boron nitride nanosheet suspension was sprayed onto the upper and lower surfaces of the initial aramid insulating paper to obtain rough aramid insulating paper. The aramid insulating rough paper is sequentially dried and hot-pressed to obtain aramid insulating paper. The step of performing vacuum filtration on the aramid insulating paper sandwich layer using the target slurry to obtain the initial aramid insulating paper includes: Using the aramid insulating paper sandwich layer as the filter membrane of the Buchner funnel, a first target funnel is obtained; The target slurry is vacuum filtered using the first target funnel to obtain a second target funnel, and the filter membrane of the second target funnel is flipped to obtain a third target funnel. The target slurry is vacuum filtered using the third target funnel to obtain initial aramid insulating paper.

8. The method for preparing aramid insulating paper according to claim 7, characterized in that, The step of mixing para-aramid short fibers and para-aramid pulp fibers based on a preset given mass ratio to obtain the target pulp includes: According to a preset given mass ratio, para-aramid short-cut fibers and para-aramid pulp fibers are added to a first deionized aqueous solution to obtain a fiber mixture. The polyethylene oxide dispersant is mixed with the fiber mixture to obtain the target mixture; The target mixture is decomposed using a fiber decomposer to obtain an initial slurry; The initial slurry is pulped using a pulping machine to obtain the target slurry.

9. The method for preparing aramid insulating paper according to claim 7, characterized in that, The specific preparation process of the boron nitride nanosheet suspension is as follows: Boron nitride microsheets, lithium citrate, isopropanol, and a second deionized aqueous solution are mixed to obtain a boron nitride dispersion, wherein the mass ratio of the boron nitride microsheets, the lithium citrate, the isopropanol, and the second deionized aqueous solution is 1:1:40:

60. The boron nitride dispersion was subjected to ultrasonic exfoliation to obtain a first dispersion; The first dispersion was subjected to hydrothermal treatment in a hydrothermal reactor to obtain a second dispersion; The second dispersion was filtered and washed to obtain a boron nitride nanosheet suspension.

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