Aramid insulation paper with high initial partial discharge voltage and preparation method and application thereof

Abstract

The application discloses high-start partial discharge voltage aramid insulation paper and a preparation method and application thereof, and relates to the field of aramid insulation paper, and discloses the aramid insulation paper, which comprises the following components in parts by weight: 50 parts of aramid short-cut fibers, 50 parts of aramid fibrids, 3 parts of aramid nanofibers and 1 part of micron-sized filling additives. The aramid insulation paper can be used in a motor of a new energy automobile, and the preparation method comprises the following steps: (1) pretreating the aramid fibrids; uniformly mixing the filling additives and the aramid nanofibers to obtain a mixture; mixing the mixture, the pretreated aramid fibrids, the aramid short-cut fibers and the remaining aramid nanofibers to obtain a slurry; (2) forming the slurry into a web, and then performing post-treatment to obtain a raw paper; and (3) coiling and high-temperature rolling the raw paper. The aramid insulation paper preparation method is simple, raw materials are easy to obtain, production is environmentally friendly, and the cost is low. The aramid insulation paper has improved mechanical properties and electrical properties, and the starting partial discharge voltage of the aramid paper is improved.

Description

Technical Field

[0001] The present invention relates to the field of special insulating paper, and in particular to aramid insulating paper with high initial partial discharge voltage, a preparation method thereof, and applications thereof. Background Art

[0002] Aramid insulation paper used in new energy vehicle motors operates at high voltages and experiences large temperature fluctuations, placing high demands on the mechanical and electrical properties of the insulation material. Initial partial discharge in the insulation material is a major cause of insulation breakdown in high-voltage electrical equipment and a key indicator of insulation degradation. Mild partial discharge has little impact on the insulation of electrical equipment, causing the insulation strength to decrease more slowly; however, strong partial discharge causes the insulation strength to decrease rapidly. This is a key factor in damaging the insulation of high-voltage electrical equipment. Therefore, increasing the initial partial discharge voltage of the insulation material and effectively avoiding insulation breakdown caused by partial discharge are key challenges in this field. Technical solutions for improving the initial partial discharge voltage of insulation paper are rare in the prior art, and those that exist also present certain technical problems. For example, while Chinese Patent No. 202210542302.6 discloses a high partial discharge insulation material for oil-cooled motors in new energy vehicles and a method for its preparation, the insulation paper in this solution has a complex structure, a cumbersome preparation process, and insufficient mechanical strength, hindering its industrial promotion and practical use. Summary of the Invention

[0003] The present invention provides an aramid insulating paper with high initial partial discharge voltage, a preparation method thereof, and an application thereof, to solve the technical problems in the prior art that it is difficult to effectively improve the initial partial discharge voltage of insulating paper, the paper structure is complex, the production is difficult, and the mechanical strength does not meet the standards.

[0004] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0005] A high initial partial discharge voltage aramid insulating paper comprising the following components in parts by weight:

[0006] 50 parts of aramid short fibers, 50 parts of aramid fibrids, 3 parts of aramid nanofibers and 1 part of filler additive;

[0007] Wherein, the aramid short fibers are aramid short fibers; the aramid nanofibers are aramid nanofibers; and the filling additives are micron-sized filling additives.

[0008] The design idea of the technical scheme is that the aramid fiber with different sizes and the filling additive are selected as main components, the aramid nanofiber with nanometer size and the filling additive with micrometer size are dispersed and filled between the pores formed by the aramid short-cut fiber with millimeter size and the aramid fibrid, a macro-micron-nanometer multi-level structure is formed, the cavity density in the aramid insulation paper is reduced, and the initial partial discharge voltage of the material is improved; the filling additive dispersed in the aramid insulation paper enhances the thermal conductivity of the material, and the problem of the initial partial discharge voltage reduction caused by the temperature rise of the material is solved. At the same time, the aramid nanofiber with nanometer size not only fills the pores, but also is attached / embedded on the surface of the filling additive to form a micrometer-nanometer structure, and the adhesion of the filling additive is enhanced through the force between the aramid nanofiber and the aramid fibrid, so that the retention rate of the filling additive and the stability of the whole system are improved, and the initial partial discharge voltage of the material is improved.

[0009] As a further preferred embodiment of the above technical scheme, the aramid nanofiber and the filling additive are filled in the pores of the aramid insulation paper, and the aramid nanofiber is adsorbed and / or embedded on the surface of the filling additive.

[0010] As a further preferred embodiment of the above technical scheme, the filling additive includes at least one of aluminum nitride, boron nitride and silicon carbide. The above additive has the ability to improve the initial partial discharge voltage of the material, and has good compatibility with the aramid paper.

[0011] As a further preferred embodiment of the above technical scheme, the filling additive is subjected to grinding treatment, and the specific surface area is 0.1-10 m2 / g. The grinding method of the filling additive is wet grinding or dry grinding.

[0012] As a further preferred embodiment of the above technical scheme, the size of the aramid short-cut fiber is 1-15 mm, the size of the aramid nanofiber is 50-300 nm, and the particle size of the filling additive is 1-20 μm. The filling additive and the aramid nanofiber are used as a composite additive combination, the size of the aramid nanofiber and the filling additive is limited to obtain the best adsorption effect.

[0013] As a further preferred embodiment of the above technical scheme, the shape of the aramid nanofiber and the filling additive is spherical or polygonal particle.

[0014] Based on the same technical concept, the application further provides a preparation method of the aramid insulation paper with high initial partial discharge voltage.

[0015] (1) pretreating the aramid fibrids; mixing the filling additive with 0.5 parts by mass of aramid nanofibers uniformly to obtain a mixture; and mixing the mixture, the pretreated aramid fibrids, aramid short fibers and the rest of the aramid nanofibers thoroughly to obtain a slurry;

[0016] (2) forming the slurry into aramid insulation paper base paper by long net paper machine through a dehydration curve and then through post-treatment;

[0017] (3) obtaining the aramid insulation paper with high initial partial discharge voltage by winding and high-temperature rolling of the aramid insulation paper base paper.

[0018] As a further preferred embodiment of the above technical solution, the pretreatment in step (1) comprises treating the aramid fibrids with a pulper and a defibrator in sequence. After the treatment, the aramid fibrids have the characteristics of large specific surface area (70-120 m 2 / g), moderate beating degree (60-85°SR) and no long fibers (fiber size not greater than 1.3 mm).

[0019] As a further preferred embodiment of the above technical solution, the slurry in step (2) is delivered to the wire section by a hydraulic headbox flow, and the hydraulic headbox flow refers to forming a turbulent flow of aramid long fibers in a turbulent flow generator in the hydraulic headbox, and then uniformly and stably distributing the slurry along the full width of the paper machine. The turbulent flow generated by the turbulent flow generator is micro-turbulent flow, and the turbulent flow intensity is 0.2-5%. The concentration of the slurry is 0.5±0.1%.

[0020] As a further preferred embodiment of the above technical solution, the dehydration curve in step (2) comprises three stages:

[0021] First stage: dehydrating the slurry by its own gravity to form a wet web with a high water content;

[0022] Second stage: providing a lower vacuum suction to the dehydration element to partially dehydrate under low vacuum conditions, and forming a structure of aramid short fibers and aramid fibrids wrapping aramid nanofibers and filling additives in the wet web;

[0023] Third stage: increasing the vacuum suction of the dehydration element to dehydrate under high vacuum conditions to remove most of the water in the wet web.

[0024] As a further preferred embodiment of the above technical solution, in the second stage, the vacuum degree for dehydration is -1~-10 kPa; and in the third stage, the vacuum degree for dehydration is -16~-25 kPa.

[0025] As a further preferred embodiment of the above technical solution, the post-treatment in step (2) comprises pressing and drying operations.

[0026] Based on the same technical concept, the present invention also provides an application of the above-mentioned high initial partial discharge voltage aramid insulation paper, which is used in motors of new energy vehicles.

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

[0028] (1) The aramid insulating paper of the present invention forms a macro-micro-nano multi-level structure, which reduces the cavity density in the aramid paper, improves the retention rate of filling additives, and improves the mechanical and electrical properties of the aramid paper. At the same time, a heat conduction path is formed through the multi-level structure, which can dissipate the heat accumulated on the surface of the aramid paper more quickly, reduce the partial discharge phenomenon, and increase the starting partial discharge voltage of the aramid paper, which can meet the use requirements of high working voltage and high temperature change conditions such as new energy vehicles.

[0029] (2) The preparation method of the aramid insulation paper of the present invention is simple, the raw materials are easily available, the production cost is low, and it is suitable for large-scale industrial production. No chemical additives are used, which reduces pollution to the environment and promotes the green manufacturing of aramid insulation paper. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of the high initial partial discharge voltage aramid insulation paper of Example 1;

[0031] Figure 2 Schematic diagram of the positional relationship between the nanofibers and filling additives in Example 1.

[0032] The present invention will be described in further detail below with reference to the accompanying drawings. DETAILED DESCRIPTION

[0033] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. However, the present invention can be implemented in many different ways as defined and covered by the claims.

[0034] Example 1:

[0035] The high initial partial discharge voltage aramid insulation paper of this embodiment includes the following components in parts by weight:

[0036] 50 parts of aramid short fibers, 50 parts of aramid fibrids, 3 parts of aramid nanofibers and 1 part of filling additives; Figure 1 and Figure 2 As shown ( Figure 1 and Figure 2 In the figure, 1 is aramid chopped fibers, 2 is aramid fibrils, 3 is aramid nanofibers, and 4 is a filling additive). The aramid nanofibers and the filling additives are filled in the pores of the aramid insulating paper, and the aramid nanofibers are adsorbed and / or embedded on the surface of the filling additives.

[0037] wherein the aramid short-cut fiber has a size of 8 mm in length; the aramid nanofiber is selected from spherical particles with a particle size D90=150 nm; the aramid precipitated fiber has a size of 1.05 mm in length and a specific surface area of 98 m 2 / g, a beating degree of 71°SR, and a pulp concentration of 0.13%; the filling additive is selected from spherical aluminum nitride particles with a particle size D90=10 μm, which are wet ground.

[0038] The preparation method of the aramid insulating paper with high initial partial discharge voltage of the embodiment comprises the following steps:

[0039] (1) The aramid precipitated fiber (50 parts) is pretreated by using a pulper and a defibrator;

[0040] (2) The filling additive (1 part) is slightly ground and fully stirred with the aramid nanofiber (0.5 part) to obtain a mixture;

[0041] (3) The aramid short-cut fiber (50 parts), the remaining aramid nanofiber (2.5 parts) and the mixture are fully mixed in the treated aramid precipitated fiber to obtain a pulp;

[0042] (4) The pulp is delivered onto the wire by a hydraulic headbox. The hydraulic headbox delivers the pulp onto the wire by first forming a turbulent flow of the aramid long fiber in the turbulent flow generator of the hydraulic headbox, and then uniformly and stably distributing the pulp along the full width of the paper machine. The turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2-5%, and the concentration of the pulp is 0.5±0.1%;

[0043] (5) The wet forming is performed on the long net paper machine using a special dewatering curve, and the forming consistency is 0.12%. The dewatering curve comprises three stages:

[0044] The first stage: dewatering is performed by using the gravity of the pulp to form a wet web with a high water content;

[0045] The second stage: a lower vacuum suction force is provided to the dewatering element to partially dewater under low vacuum conditions (-8 kPa) to form a structure of the aramid short-cut fiber and the aramid precipitated fiber wrapping the aramid nanofiber and the filling additive in the wet web;

[0046] The third stage: the vacuum suction force of the dewatering element is increased to dewater under high vacuum conditions (-25 kPa) to remove most of the water in the wet web;

[0047] (6) The aramid insulating paper base paper is obtained after subsequent pressing and drying;

[0048] (7) The raw paper is wound and composite hot-pressed by an electromagnetic induction high-temperature roller press, the linear pressure is 275 N / m, and the hot-pressing temperature is 310℃, thereby obtaining the high initial partial discharge voltage aramid insulation paper of the embodiment.

[0049] The high initial partial discharge voltage aramid insulation paper of the embodiment is used in the motor of a new energy vehicle.

[0050] Embodiment 2

[0051] The high initial partial discharge voltage aramid insulation paper of the embodiment comprises the following components by mass fraction:

[0052] 50 parts of aramid short-cut fibers, 50 parts of aramid fibrids, 3 parts of aramid nanofibers, and 1 part of a filling additive; the aramid nanofibers and the filling additive are filled in the pores of the aramid insulation paper, and the aramid nanofibers are adsorbed and / or inlaid on the surface of the filling additive.

[0053] The size of the aramid short-cut fibers is: length 9 mm; the aramid nanofibers are aramid nanofibers, and polygonal particles are selected, with a particle size D90=100 nm; the size of the aramid fibrids is: length 1.05 mm, specific surface area 94 m 2 / g, beating degree 70°SR, and pulp concentration 0.12%; the filling additive is selected to be polygonal aluminum nitride particles ground by a dry method, with a particle size D90=15 μm.

[0054] The preparation method of the high initial partial discharge voltage aramid insulation paper of the embodiment comprises the following steps:

[0055] (1) The aramid fibrids (50 parts) are pretreated by a pulper and a defibrator;

[0056] (2) The filling additive (1 part) is lightly ground and fully stirred with the aramid nanofibers (0.5 parts) to obtain a mixture;

[0057] (3) The aramid short-cut fibers (50 parts), the remaining aramid nanofibers (2.5 parts), and the mixture are added to the treated aramid fibrids and fully mixed to obtain a slurry;

[0058] (4) The slurry is delivered onto the wire by a hydraulic flow box; the hydraulic flow box delivers the slurry onto the wire by first forming a turbulent flow of aramid long fibers in the turbulent flow generator of the hydraulic flow box, and then uniformly and stably distributing the slurry along the full width of the paper machine; the turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2~5%, and the concentration of the slurry is 0.5±0.1%;

[0059] (5) The long net paper machine is used for wet forming by using a special dewatering curve, and the forming consistency is 0.12%; the dewatering curve comprises three stages:

[0060] First stage: dewatering by gravity of the slurry, to form a wet web with a high water content;

[0061] Second stage: providing a lower vacuum suction to the dewatering element, to partially dewater under low vacuum (-9 kPa), to form a structure of aramid short fibers and aramid fibrils encapsulating aramid nanofibers and filler additives in the wet web;

[0062] Third stage: increasing the vacuum suction of the dewatering element, to dewater under high vacuum (-24 kPa), to remove most of the water in the wet web;

[0063] (6) After subsequent pressing and drying, an aramid insulation paper base paper is obtained;

[0064] (7) The base paper is wound and subjected to composite hot pressing using an electromagnetic induction high-temperature roller press, with a linear pressure of 285 N / m and a hot pressing temperature of 305°C, to obtain the high initial partial discharge voltage aramid insulation paper of the present embodiment.

[0065] The high initial partial discharge voltage aramid insulation paper of the present embodiment is used in the motor of a new energy vehicle.

[0066] Example 3:

[0067] The high initial partial discharge voltage aramid insulation paper of the present embodiment comprises the following components by mass:

[0068] 50 parts of aramid short fibers, 50 parts of aramid fibrils, 3 parts of aramid nanofibers, and 1 part of filler additives; the aramid nanofibers and filler additives are filled in the pores of the aramid insulation paper, and the aramid nanofibers are adsorbed and / or embedded on the surface of the filler additives.

[0069] The size of the aramid short fibers is: length 7 mm; the aramid nanofibers are spherical particles with a particle size D90 = 100 nm; the size of the aramid fibrils is: length 0.40 mm, specific surface area 94 m 2 / g, beating degree 70°SR, slurry concentration 0.12%; the filler additives are spherical aluminum nitride particles ground by a wet method, with a particle size D90 = 12.5 μm.

[0070] The preparation method of the high initial partial discharge voltage aramid insulation paper of the present embodiment comprises the following steps:

[0071] (1) The aramid fibrils (50 parts) are pretreated using a pulper and a defibrator;

[0072] (2) The filler additives (1 part) are lightly ground and fully stirred with the aramid nanofibers (0.5 parts) to obtain a mixture;

[0073] (3) adding aramid short fibers (50 parts), the rest of aramid nanofibers (2.5 parts) and the mixture into the treated aramid fibrids, and mixing thoroughly to obtain a slurry;

[0074] (4) delivering the slurry onto the wire from a hydraulic headbox; the hydraulic headbox delivers the slurry uniformly and stably along the full width of the paper machine, the turbulence generated by the turbulence generator in the hydraulic headbox is micro turbulence, the turbulence intensity is 0.2-5%, and the concentration of the slurry is 0.5±0.1%;

[0075] (5) using a special dewatering curve for wet forming on a Fourdrinier paper machine, and the forming consistency is 0.12%; the dewatering curve includes three stages:

[0076] The first stage: dewatering by using the gravity of the slurry to form a wet web with a high water content;

[0077] The second stage: providing a low vacuum suction to the dewatering element for partial dewatering under low vacuum conditions (-9 kPa) to form a structure of aramid short fibers and aramid fibrids wrapping aramid nanofibers and filling additives in the wet web;

[0078] The third stage: increasing the vacuum suction of the dewatering element for dewatering under high vacuum conditions (-24 kPa) to remove most of the water in the wet web;

[0079] (6) obtaining aramid insulation paper base paper through subsequent pressing and drying;

[0080] (7) coiling the base paper and using an electromagnetic induction high-temperature roll press to perform composite hot pressing, the linear pressure is 285 N / m, and the hot pressing temperature is 305°C, thereby obtaining the high initial partial discharge voltage aramid insulation paper of the embodiment.

[0081] The high initial partial discharge voltage aramid insulation paper of the embodiment is used in the motor of a new energy vehicle.

[0082] Comparative Example 1

[0083] The aramid insulation paper of the comparative example includes the following components by mass:

[0084] 50 parts of aramid short fibers and 50 parts of aramid fibrids.

[0085] The size of the aramid short fibers is: length 6 mm; the size of the aramid fibrids is: length 0.6 mm, specific surface area 98 m 2 / g, beating degree 71°SR, and slurry concentration 0.13%; the filling additive is spherical aluminum nitride particles ground by a wet method, and the particle size D90=10 μm.

[0086] The preparation method of the aramid insulation paper of the present comparative example comprises the following steps:

[0087] (1) The aramid fibrids (50 parts) are pretreated by using a pulper and a defibrator;

[0088] (2) Aramid short-cut fibers (50 parts) are added to the treated aramid fibrids, and mixed thoroughly to obtain a slurry;

[0089] (3) The slurry is fed onto the wire by a hydraulic headbox. The hydraulic headbox feeding onto the wire means that the aramid long fibers are first formed into turbulent flow by a turbulent flow generator in the hydraulic headbox, and then the slurry is uniformly and stably distributed along the full width of the paper machine. The turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2-5%, and the concentration of the slurry is 0.5±0.1%;

[0090] (4) The wet-forming is performed on a Fourdrinier paper machine using a special dewatering curve, and the forming consistency is 0.12%. The dewatering curve comprises three stages:

[0091] The first stage: dewatering is performed by using the gravity of the slurry to form a wet web with a high water content;

[0092] The second stage: a lower vacuum suction is provided to the dewatering element, and partial dewatering is performed under low vacuum (-8 kPa);

[0093] The third stage: the vacuum suction of the dewatering element is increased, and dewatering is performed under high vacuum (-25 kPa) to remove most of the water in the wet web;

[0094] (5) The aramid insulation paper base paper is obtained after subsequent pressing and drying;

[0095] (6) The base paper is wound and subjected to composite hot pressing by using an electromagnetic induction high-temperature roller press, the linear pressure is 275 N / m, and the hot pressing temperature is 310°C, thereby obtaining the aramid insulation paper of the present comparative example.

[0096] Comparative Example 2

[0097] The aramid insulation paper of the present comparative example comprises the following components by mass:

[0098] 50 parts of aramid short-cut fibers, 50 parts of aramid fibrids, and 1 part of a filling additive.

[0099] The size of the aramid short-cut fibers is: length 4 mm; the size of the aramid fibrids is: length 0.55 mm, specific surface area 98 m 2 / g, beating degree 71°SR, and slurry concentration 0.13%; the filling additive is spherical aluminum nitride particles obtained by wet grinding, and the particle size D90=10 μm.

[0100] The preparation method of the aramid insulation paper of the present comparative example comprises the following steps:

[0101] (1) pretreat aramid fibrid (50 parts) by using a pulper and a defibrator;

[0102] (2) slightly grind the filling additive (1 part);

[0103] (3) add aramid short-cut fiber (50 parts) and the filling additive (1 part) to the treated aramid fibrid, and mix thoroughly to obtain a slurry;

[0104] (4) deliver the slurry onto a wire by a hydraulic headbox; the hydraulic headbox delivery onto a wire refers to that the aramid long fiber is first formed into turbulent flow by a turbulent flow generator in the hydraulic headbox, and then the slurry is uniformly and stably distributed along the full width of the paper machine, the turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2-5%, and the concentration of the slurry is 0.5±0.1%;

[0105] (5) use a special dewatering curve for wet forming on a Fourdrinier paper machine, and the forming consistency is 0.12%; the dewatering curve comprises three stages:

[0106] First stage: dewater the slurry by using its own gravity to form a wet web with a high water content;

[0107] Second stage: provide a lower vacuum suction to the dewatering element, and partially dewater under low vacuum condition (-8 kPa);

[0108] Third stage: increase the vacuum suction of the dewatering element, and dewater under high vacuum condition (-25 kPa) to remove most of the water in the wet web;

[0109] (6) obtain aramid insulation paper base paper through subsequent pressing and drying;

[0110] (7) roll up the base paper, and perform composite hot pressing by using an electromagnetic induction high-temperature roll press, the linear pressure is 275 N / m, and the hot pressing temperature is 310°C, thereby obtaining the aramid insulation paper of the present comparative example.

[0111] Comparative Example 3

[0112] The aramid insulation paper of the present comparative example comprises the following components by mass:

[0113] 50 parts of aramid short-cut fiber, 50 parts of aramid fibrid, and 3 parts of aramid nanofiber.

[0114] The size of the aramid short-cut fiber is 5 mm in length; the aramid nano-fiber is selected as a spherical particle with a particle size D90 = 150 nm; the size of the aramid fibrid is 0.70 mm in length, and the specific surface area is 98 m 2 / g, the beating degree is 71°SR, and the pulp concentration is 0.13%.

[0115] The preparation method of the aramid insulation paper of the present comparative example comprises the following steps:

[0116] (1) The aramid fibrid (50 parts) is pretreated by using a pulper and a defibrator;

[0117] (2) The aramid short-cut fiber (50 parts) and the aramid nano-fiber (3 parts) are added to the treated aramid fibrid, and are fully mixed to obtain a pulp;

[0118] (3) The pulp is delivered onto the wire by a hydraulic headbox. The hydraulic headbox delivers the pulp uniformly and stably along the full width of the paper machine, and the turbulence generated by the turbulence generator in the hydraulic headbox is micro-turbulence, and the turbulence intensity is 0.2-5%, and the concentration of the pulp is 0.5±0.1%;

[0119] (4) The wet forming is performed on a Fourdrinier paper machine using a special dewatering curve, and the forming consistency is 0.12%; the dewatering curve comprises three stages:

[0120] The first stage: the dewatering is performed by using the gravity of the pulp, so that the wet web with a high water content is formed;

[0121] The second stage: the dewatering element is provided with a low vacuum suction, and the partial dewatering is performed under the low vacuum condition (-8 kPa);

[0122] The third stage: the vacuum suction of the dewatering element is increased, and the dewatering is performed under the high vacuum condition (-25 kPa), so that most of the water in the wet web is removed;

[0123] (5) The aramid insulation paper base paper is obtained after subsequent pressing and drying;

[0124] (6) The base paper is wound, and is subjected to composite hot pressing by using an electromagnetic induction high-temperature roller press, the linear pressure is 275 N / m, and the hot pressing temperature is 310°C, so that the aramid insulation paper of the present comparative example is obtained.

[0125] Comparative Example 4

[0126] The aramid insulation paper of the present comparative example comprises the following components by mass:

[0127] 50 parts of aramid short-cut fiber, 50 parts of aramid fibrid, 3 parts of aramid nano-fiber, and 1 part of filling additive.

[0128] wherein the aramid short-cut fiber has a size of 6 mm in length; the aramid nanofiber is selected from spherical particles with a particle size D90=150 nm; the aramid fibrid has a size of 0.80 mm in length and a specific surface area of 98 m 2 / g, a beating degree of 71°SR, and a pulp concentration of 0.13%; the filling additive is selected from unground spherical aluminum nitride particles with a particle size D90=10 μm.

[0129] The aramid insulation paper of the present comparative example is prepared by the following steps:

[0130] (1) The aramid fibrid (50 parts) is pretreated by using a pulper and a defibrator;

[0131] (2) The filling additive (1 part) is directly and fully stirred with the aramid nanofiber (0.5 part) without grinding to obtain a mixture;

[0132] (3) The aramid short-cut fiber (50 parts), the remaining aramid nanofiber (2.5 parts) and the mixture are fully mixed in the treated aramid fibrid to obtain a pulp;

[0133] (4) The pulp is delivered onto the wire by a hydraulic headbox. The pulp is first formed into a turbulent flow by a turbulent flow generator in the hydraulic headbox, and then the pulp is evenly and stably distributed along the full width of the paper machine. The turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2-5%, and the concentration of the pulp is 0.5±0.1%;

[0134] (5) The pulp is formed by a special dewatering curve wet forming method on a long net paper machine, and the forming concentration is 0.12%. The dewatering curve includes three stages:

[0135] The first stage: the pulp is dewatered by using its own gravity to form a wet paper web with a high water content;

[0136] The second stage: a lower vacuum suction force is provided to the dewatering element, and the wet paper web is partially dewatered under low vacuum condition (-8 kPa) to form a structure of aramid short-cut fiber and aramid fibrid wrapping aramid nanofiber and filling additive in the wet paper web;

[0137] The third stage: the vacuum suction force of the dewatering element is increased, and the wet paper web is dewatered under high vacuum condition (-25 kPa) to remove most of the water in the wet paper web;

[0138] (6) The aramid insulation paper base paper is obtained after subsequent pressing and drying;

[0139] (7) The raw paper is wound and composite hot-pressed by an electromagnetic induction high-temperature roller press, the linear pressure is 275 N / m, the hot-pressing temperature is 310 ℃, and the aramid insulation paper of the present comparative example is obtained.

[0140] Comparative Example 5

[0141] The aramid insulation paper of the present comparative example comprises the following components by mass:

[0142] 50 parts of aramid short-cut fibers, 50 parts of aramid fibrids, 3 parts of aramid nanofibers, and 1 part of a filling additive.

[0143] The size of the aramid short-cut fibers is: length 8 mm; the aramid nanofibers are selected as spherical particles with a particle size D90 = 150 nm; the size of the aramid fibrids is: length 0.9 mm, specific surface area 98 m 2 / g, beating degree 71°SR, and pulp concentration 0.13%; the filling additive is selected as spherical aluminum nitride particles with a particle size D90 = 50 μm after wet grinding.

[0144] The preparation method of the aramid insulation paper of the present comparative example comprises the following steps:

[0145] (1) The aramid fibrids (50 parts) are pretreated by a pulper and a defibrator;

[0146] (2) The filling additive (1 part) is wet ground, and then mixed with the aramid nanofibers (0.5 parts) to obtain a mixture;

[0147] (3) The aramid short-cut fibers (50 parts), the remaining aramid nanofibers (2.5 parts), and the mixture are added to the treated aramid fibrids and mixed to obtain a pulp;

[0148] (4) The pulp is delivered onto the wire by a hydraulic headbox, which means that the aramid long fibers are first formed into turbulent flow by a turbulent flow generator in the hydraulic headbox, and then the pulp is uniformly and stably distributed along the full width of the paper machine, the turbulent flow generated by the turbulent flow generator is micro-turbulent flow, the turbulent flow intensity is 0.2-5%, and the pulp concentration is 0.5±0.1%;

[0149] (5) The pulp is formed by a special dewatering curve wet forming method on a long net paper machine, and the forming consistency is 0.12%; the dewatering curve comprises three stages:

[0150] The first stage: dewatering by using the gravity of the pulp to form a wet paper web with a high water content;

[0151] Second stage: provide lower vacuum suction force to the dehydration element, partially dehydrate under low vacuum condition (-8 kPa), form the structure of aramid short-cut fiber and aramid precipitated fiber wrapping aramid nanofiber and filling additive in the wet paper web;

[0152] Third stage: increase the vacuum suction force of the dehydration element, dehydrate under high vacuum condition (-25 kPa), remove most of the water in the wet paper web;

[0153] (6) After subsequent pressing and drying, obtain aramid insulation paper base paper;

[0154] (7) Roll up the base paper and use electromagnetic induction high-temperature roller press for composite hot pressing, linear pressure is 275 N / m, hot pressing temperature is 310℃, thus obtain the voltage aramid insulation paper of the present comparative example.

[0155] Comparative Example 6:

[0156] The difference between the present comparative example and Example 3 is that, in the present comparative example, the vacuum degree of the second stage of partial dehydration under low vacuum condition in step (5) of the preparation method is adjusted to -15 kPa, and other components, proportions, processes and parameters are consistent with those of Example 3.

[0157] Comparative Example 7:

[0158] The difference between the present comparative example and Example 3 is that, in the present comparative example, the vacuum degree of the third stage of partial dehydration under high vacuum condition in step (5) of the preparation method is adjusted to -30 kPa, and other components, proportions, processes and parameters are consistent with those of Example 3.

[0159] The prepared products of the above examples and comparative examples are tested for performance, and the results are shown in Table 1 below.

[0160] Table 1. Performance test results of aramid insulation paper of each example and comparative example

[0161]

[0162] The above test results show that:

[0163] Comparative Example 1 has a small decrease in mechanical properties and a more obvious decrease in electrical strength and initial partial discharge voltage, compared with Example 1, because no aramid nanofiber and filling additive is added in Comparative Example 1.

[0164] Comparative example 2, 3, 4 relative to comparative example 1, respectively, no aramid nanofiber, no filler additive, filler additive is not ground. Comparative example 2 only has a filler additive, and the performance of the material except the initial partial discharge voltage is slightly decreased. This is because the filler additive can play a role in heat conduction, and alleviate the phenomenon of the initial partial discharge voltage decrease caused by temperature rise. However, the micron-sized filler additive has a certain impact on the structure of aramid insulation paper in the absence of the joint action of nanofiber, which leads to the decline of the comprehensive performance. In comparative example 3, only aramid nanofiber is used, and the performance of the finished product is improved as a whole, but the improvement of the initial partial discharge voltage is not obvious. In comparative example 4, the surface of the filler additive is not ground, and the stabilizing effect of nanofiber on the filler additive is lacking. The aramid nanofiber and aramid fibrid, chopped fiber only have a coating and fixing effect on the additive, so the overall performance of the material is slightly decreased.

[0165] In comparative example 5, the particle size of the filler additive is increased (the particle size of aramid nanofiber is fixed), and the performance of the paper is obviously decreased. This is because the particle size is too large, which has a certain destructive effect on the structure of aramid insulation paper.

[0166] Comparative examples 6, 7 relative to examples 2, 3, the dehydration curve is adjusted. In comparative example 6, the vacuum degree of the front dehydration curve is increased, and the performance of the paper is greatly decreased. This is because when the front dehydration vacuum degree is too high, the micron-nanometer structure in the aramid wet paper body is easily damaged, resulting in poor paper uniformity and insufficient performance. In comparative example 7, the vacuum degree of the rear dehydration curve is increased (since reducing the vacuum degree will cause incomplete dehydration and cannot proceed with the subsequent paper drawing work, so comparative example is not given), and the performance of the paper is also greatly decreased. This is also because the microstructure of aramid paper is damaged. At the same time, too high vacuum degree in the later stage will accelerate the wear of the forming net, which is not conducive to production work.

[0167] The above is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above is only a preferred embodiment of the present application, and the protection scope of the present application is not limited to the above-mentioned examples. For those skilled in the art, the improvements and changes obtained without departing from the technical concept of the present application shall be considered as the protection scope of the present application.

Claims

1. A high initial partial discharge voltage aramid insulation paper, characterized in that: The composition comprises the following components in parts by weight: 40-60 parts of aramid chopped fibers, 60-40 parts of aramid fibrids, 2-5 parts of aramid nanofibers and 1 part of a filling additive; wherein the filling additive is a micron-sized filling additive; the aramid nanofibers and the filling additive are filled in the pores of the aramid insulating paper, and the aramid nanofibers are adsorbed and / or embedded on the surface of the filling additive; the filling additive comprises at least one of aluminum nitride, boron nitride and silicon carbide; the filling additive is ground to have a specific surface area greater than or equal to 50 m 2 / g; the size of the aramid chopped fibers is 1 to 15 mm, the size of the aramid nanofibers is 50 to 300 nm, and the particle size of the filling additive is 1 to 20 μm; The method for preparing the high initial partial discharge voltage aramid insulation paper comprises the following steps: (1) pre-treating the aramid fibrid; uniformly mixing the filler additive with 0.5 parts by mass of aramid nanofibers to obtain a mixture; fully mixing the mixture, the pre-treated aramid fibrids, aramid chopped fibers, and the remaining aramid nanofibers to obtain a slurry; the pre-treating comprises sequentially treating the aramid fibrids with a pulper and a deflaker; (2) The slurry is put on a fourdrinier paper machine and wet-formed by a dehydration curve, and then post-processed to obtain aramid insulation paper base paper; the dehydration curve includes three stages: The first stage: Dehydrate the pulp by its own gravity to form a wet paper base with a high water content; The second stage: providing a low vacuum suction force to the dehydration element, partially dehydrating under low vacuum conditions, with a vacuum degree of -1~-10kPa, to form a structure of aramid short fibers and aramid fibrids encapsulating aramid nanofibers and filling additives in the wet paper web; The third stage: improve the vacuum suction force of the dehydration element, dehydrate under high vacuum conditions, and the vacuum degree of dehydration is -16~-25kPa to remove most of the moisture in the wet paper web; (3) The aramid insulation paper base paper is wound and rolled at high temperature to obtain the high initial partial discharge voltage aramid insulation paper.

2. A method for preparing the high initial partial discharge voltage aramid insulation paper according to claim 1, characterized in that: The following steps are involved: (1) pre-treating the aramid fibrid; uniformly mixing the filler additive with 0.5 parts by mass of aramid nanofibers to obtain a mixture; and fully mixing the mixture, the pre-treated aramid fibrid, the aramid chopped fibers, and the remaining aramid nanofibers to obtain a slurry; (2) placing the slurry on a fourdrinier paper machine for wet forming through a dehydration curve, and then post-processing to obtain aramid insulation paper base paper; The slurry is conveyed onto the screen by a hydraulic headbox. The hydraulic headbox conveying means firstly passing the slurry through a turbulence generator in the hydraulic headbox to form turbulence, and then uniformly and stably distributing the slurry along the full width of the paper machine. The turbulence generated by the turbulence generator is micro-turbulence, and the turbulence intensity generated is 0.2-5%. The concentration of the slurry is 0.5±0.1%; The dehydration curve consists of 3 stages: The first stage: Dehydrate the pulp by its own gravity to form a wet paper base with a high water content; The second stage: providing a low vacuum suction force to the dehydration element, partially dehydrating under low vacuum conditions, with a vacuum degree of -1~-10kPa, to form a structure of aramid short fibers and aramid fibrids encapsulating aramid nanofibers and filling additives in the wet paper web; The third stage: improve the vacuum suction force of the dehydration element, dehydrate under high vacuum conditions, and the vacuum degree of dehydration is -16~-25kPa to remove most of the moisture in the wet paper web; (3) The aramid insulation paper base paper is wound and rolled at high temperature to obtain the high initial partial discharge voltage aramid insulation paper.

3. The method for preparing high initial partial discharge voltage aramid insulation paper according to claim 2, characterized in that: The post-processing in step (2) includes pressing and drying operations.

4. An application of the high initial partial discharge voltage aramid insulation paper according to claim 1, characterized in that: The high initial partial discharge voltage aramid insulation paper is used in motors of new energy vehicles.

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