Preparation method of aramid mica paper

Abstract

The application discloses a preparation method of aramid mica paper, comprising the following steps: (1) subjecting meta-aramid fibrid to CF4 plasma modification, and then dispersing the modified meta-aramid fibrid to obtain slurry A; dispersing meta-aramid short-cut fibers to obtain slurry B; and dispersing mica to obtain slurry C; (2) uniformly mixing the slurry A, the slurry B and the slurry C, and then papermaking and hot-pressing to obtain the aramid mica paper. The aramid mica paper is used for motor insulation materials of wind-driven generators, and the insulation material has high electrical strength, good corona resistance and high temperature resistance grade; the material can reduce the corona phenomenon and the partial discharge phenomenon in the high-speed running process of the wind-driven generator, and prolongs the service life of the wind-driven generator.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to a method for preparing insulating paper. Background Art

[0002] When wind turbines operate at high loads, corona and partial discharge are inevitable. To extend the life of wind turbines and reduce failures, it is necessary to improve the corona resistance and partial discharge inception voltage of the insulation materials used in the motors. Furthermore, the insulation materials may stretch and bend during installation, necessitating improvements in mechanical properties such as tensile strength, elongation at break, and tear resistance. Aramid materials offer excellent mechanical properties and a certain degree of electrical strength, but their corona resistance is poor. Mica materials offer excellent electrical strength and corona resistance, but their mechanical properties are poor. Combining these two materials will complement each other's shortcomings and enhance the overall performance of the insulation material.

[0003] For example, patent document CN114214867A discloses a corona-resistant aramid mica insulation paper and its preparation method, which includes the following steps: Step 1, first decomposing aramid chopped fibers, polyethylene oxide, and water, and then adding aramid fibrils to decompress them to obtain a first slurry; Step 2, adding muscovite flakes to the first slurry to decompress them to obtain a second slurry, wherein the total mass of aramid chopped fibers, aramid fibrils, and muscovite flakes in the second slurry accounts for 0.04-0.07%; Step 3, dehydrating, forming, pressing, drying, and hot pressing the second slurry in sequence to obtain aramid / mica insulation paper. This patent significantly improves the corona resistance of aramid paper by adding high-temperature and corona-resistant muscovite flakes to the manufacturing process of aramid paper, avoiding the problem of aramid paper being easily aged due to repeated electric shocks under high temperature and high pressure, and meeting the application requirements of equipment for a long insulation life cycle.

[0004] However, the patent's use of polyethylene oxide makes the product less heat-resistant, and the resulting aramid mica paper is prone to sticking to the rollers during subsequent high-temperature hot pressing, hindering production. Furthermore, the electrical and mechanical properties of the product produced under this patent also need to be improved. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology and provide a method for preparing aramid mica paper with excellent high temperature resistance, mechanical properties and electrical properties.

[0006] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0007] A method for preparing aramid mica paper comprises the following steps:

[0008] (1) Meta-aramid fibrids were modified by CF4 plasma, and the modified meta-aramid fibrids were dispersed to obtain slurry A; meta-aramid short fibers were dispersed to obtain slurry B; and mica was dispersed to obtain slurry C;

[0009] (2) Slurry A, slurry B and slurry C are mixed evenly, and then papered and hot-pressed to obtain aramid mica paper.

[0010] The present invention performs CF4 plasma modification on meta-aramid fibrids. CF4 plasma can graft fluoride ions onto the meta-aramid fibrids, and the fluoride ions can provide the meta-aramid fibrids with higher corona resistance. At the same time, CF4 plasma is easy to clean and hardly remains in the meta-aramid fibrids. Therefore, the present invention selects CF4 plasma to modify the meta-aramid fibrids.

[0011] In the above preparation method, when the meta-aramid fibrid is subjected to CF4 plasma modification, the volume ratio of CF4 gas to Ar gas is preferably (1-5):(5-30), the flow rate is 0.1-5 SLM, and the treatment time is 1-10 minutes. Within this process parameter range, the fluoride ion grafting rate of CF4 plasma modification can be maximized, ensuring economic efficiency. Furthermore, the above volume ratio of CF4 gas to Ar gas can control the amount of fluoride ion grafting, avoiding the modification effect caused by insufficient grafting and the deterioration of the mechanical and electrical properties of the aramid mica paper product caused by excessive grafting.

[0012] In the above preparation method, preferably, the modified meta-aramid fibrids are dispersed to obtain slurry A, which is then dispersed in a deflaker for 5-10 minutes at a speed of 1500-3000 rpm / min. The modified meta-aramid fibrids are required to act as a binder, and the specific deflaking treatment facilitates uniform dispersion and bonding with the meta-aramid chopped fibers and mica.

[0013] In the above preparation method, preferably, the length of the meta-aramid short fibers is 5-7 mm. The reason for controlling the length of the meta-aramid short fibers to 5-7 mm is that the meta-aramid short fibers within this range can achieve better bonding strength with the modified meta-aramid fibrids and mica, providing higher mechanical properties. Outside this range, the uniformity of the aramid mica paper may be reduced, and the mechanical properties may be low.

[0014] In the above preparation method, preferably, when the meta-aramid chopped fibers are dispersed to obtain slurry B, they are dispersed in a deflaker for 2-5 minutes at a speed of 2000-3500 rpm / min. The deflaking treatment ensures that the meta-aramid chopped fibers are uniformly mixed with the modified meta-aramid fibrids and mica, thereby ensuring that their effects are fully exerted.

[0015] In the above preparation method, the mica is preferably calcined mica and / or synthetic mica, with the calcined mica having a particle size of 70-120 μm and the synthetic mica having a particle size of 90-180 μm, and the mass ratio of synthetic mica to calcined mica being (0-50):(50-100). Controlling the mica particle size within the above range allows for more uniform dispersion of the mica, providing better uniformity for the aramid mica paper, thereby enhancing product performance. An appropriate amount of synthetic mica can provide the aramid mica paper with improved corona resistance and high electrical strength retention. However, the surface of synthetic mica is smoother than that of calcined mica, and excessive use can deteriorate the mechanical properties of the aramid mica paper. More preferably, the mica must include synthetic mica, i.e., the mica is composed of both calcined mica and synthetic mica. The synergistic effect of the synthetic mica and the fluoride-modified meta-aramid fibrids helps improve the product's corona resistance.

[0016] In the above preparation method, preferably, when the mica is dispersed to obtain slurry C, it is dispersed in a deflaker for 1-5 minutes at a speed of 1500-3000 rpm / min. The deflaking treatment of the mica allows it to be better mixed with the modified meta-aramid fibrids and meta-aramid chopped fibers, ensuring better performance of their effects.

[0017] In the above preparation method, preferably, slurries A, B, and C are uniformly mixed using a deflaking machine. After slurries A, B, and C are uniformly mixed, the mass ratio of the modified meta-aramid fibrid, meta-aramid chopped fibers, and mica is (30-70): (5-25): (30-55). Controlling within this mass ratio allows the production of aramid mica paper with both high corona resistance and high mechanical properties. Specifically, the modified meta-aramid fibrid serves as a binder, and controlling its mass content ensures uniform dispersion and bonding of the meta-aramid chopped fibers and mica. If the modified meta-aramid fibrid is not treated within this range, the meta-aramid chopped fibers and mica are unevenly dispersed, resulting in poor aramid mica paper production and mica shedding, resulting in mica shedding and low surface strength. Meta-aramid chopped fibers provide strength to aramid mica paper. Too little meta-aramid chopped fibers will result in insufficient mechanical properties, while too much will also affect the mechanical properties. Furthermore, excessive use of meta-aramid chopped fibers will reduce the proportion of meta-aramid fibrils, affecting product bonding, reducing surface strength, and making the mica more susceptible to detachment. Mica is used to provide aramid mica paper with higher corona resistance. Using too little mica will reduce surface uniformity, failing to achieve the desired effect of improving corona resistance. Using too much will weaken the bonding strength of the aramid mica paper and reduce its mechanical properties.

[0018] In the above preparation method, preferably, during papermaking, the paper is made by a PTI Kaiser method rapid paper sheet former, 3-9 L of water is added, the bubbling time is 5-10 s, and the paper is left to stand for 5-10 s. The aramid mica paper is then dehydrated and dried.

[0019] In the above preparation method, preferably, during hot pressing, the hot pressing temperature is 260-320° C., the hot pressing pressure is 0.5-5 MPa, and the hot pressing speed is 2-8 m / min.

[0020] Wind power generation is essential for the use of motors. Early-generation motors suffered from various problems due to aging insulation materials and poor corona resistance, significantly reducing power generation efficiency. The aramid mica paper produced by the present invention can be used as insulation for these motors, significantly improving the material's electrical strength and corona resistance while maintaining mechanical strength, making it suitable for high-speed wind turbines.

[0021] The aramid mica paper of the present invention comprises modified meta-aramid fibrids, meta-aramid chopped fibers, and mixed mica. Slurry A primarily comprises meta-aramid fibrids modified with CF4 plasma, slurry B primarily comprises meta-aramid chopped fibers of a predetermined length, and slurry C primarily comprises one or both of calcined mica and synthetic mica (preferably synthetic mica). By using these three components and adjusting the proportions of each component, the resulting aramid mica paper exhibits excellent high-temperature resistance, enhanced corona resistance and electrical strength, and improved mechanical strength. The mechanical strength, electrical strength, and corona resistance of the resulting aramid mica paper are all superior to those of unmodified aramid mica paper, potentially extending the service life of wind turbines. Furthermore, the present invention utilizes domestically produced aramid and mica raw materials, reducing raw material restrictions. The modified aramid mica paper exhibits high-temperature resistance, exceptional electrical properties, high corona resistance, and excellent mechanical properties, making it suitable for use in wind turbine motor insulation.

[0022] In the present invention, the modified meta-aramid fibrils have higher corona resistance due to the grafting of fluoride ions. The modified meta-aramid fibrils provide bonding, electrical strength and partial corona resistance, the meta-aramid chopped fibers provide mechanical strength, and the mica can provide high temperature resistance and high corona resistance, especially the high temperature resistance of synthetic mica is higher than that of natural mica. The present invention innovatively utilizes CF4 plasma to modify and optimize the meta-aramid fibrils that mainly provide bonding. This specific modification method is conducive to mutual coordination with other components, which is conducive to better improving the corona resistance of the product, especially after coordination with mica containing synthetic mica, the electrical resistance is more excellent and the electrical strength retention rate is higher. The present invention uses the synergistic coordination of the above three components to make the improved aramid mica paper have better electrical strength, corona resistance, mechanical properties and high temperature resistance.

[0023] The motor produced by the aramid mica paper of the present invention can avoid corona phenomenon and partial discharge phenomenon during operation, and can be applied to the motor insulation material of wind generators requiring high corona partial discharge voltage resistance and frequency conversion function.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. The aramid mica paper produced by the preparation method of the present invention uses slurry A (CF4 plasma-modified meta-aramid fibrid), slurry B (meta-aramid chopped fiber) and slurry C (mica) as raw materials. It can combine the dual advantages of high strength, good dielectric properties and chemical stability of pure aramid paper with the good corona resistance of pure mica paper, thereby improving the corona resistance of aramid mica paper, reducing partial discharge, and enhancing the mechanical strength and electrical strength of the aramid mica composite material.

[0026] 2. The aramid mica paper of the present invention is used as an insulation material for the motor of a wind turbine. The insulation material has high electrical strength, good corona resistance, and high temperature resistance. The use of the material can reduce the corona phenomenon and partial discharge phenomenon during the high-speed operation of the wind turbine, thereby increasing the service life of the wind turbine. DETAILED DESCRIPTION

[0027] In order to facilitate understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0028] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0029] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0030] Example 1:

[0031] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0032] 1. Preparation of Component A:

[0033] Meta-aramid fibrids were modified with CF4 plasma. The modification conditions were: a CF4 gas to Ar gas ratio of 1:10 (v / v), a flow rate of 3 SLM, and a treatment time of 5 minutes. 30% by weight of the modified meta-aramid fibrids (the modified meta-aramid fibrids accounted for 30% of the mass of the aramid mica paper; the following examples and comparative examples are the same) were deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0034] 2. Preparation of component B:

[0035] 15% by weight of meta-aramid short-cut fibers (meta-aramid short-cut fibers account for 15% of the mass of aramid mica paper, the same as in the following examples and comparative examples), with a length of 5 mm, were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0036] 3. Preparation of component C:

[0037] Component C consists of calcined mica and synthetic mica. The calcined mica has a particle size of 70-120 μm (D50 approximately 100 μm, the same in the following examples and comparative examples), and the synthetic mica has a particle size of 90-180 μm (D50 approximately 100 μm, the same in the following examples and comparative examples). The ratio of synthetic mica to calcined mica is 1:10 (w / w). 55% by weight of the mica (mica accounts for 55% of the mass of the aramid mica paper, the same in the following examples and comparative examples) is deflaked in a deflaking machine at 3000 rpm for 1 minute and set aside.

[0038] 4. Preparation of aramid mica paper:

[0039] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 30:15:55) and mixed thoroughly using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with 5 L of water added, a bubbling time of 10 seconds, a 5-second rest period, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 280°C, a pressure of 3 MPa, and a speed of 4 m / min to obtain aramid mica paper.

[0040] The performance test results of the above aramid mica paper are as follows:

[0041] The electrical strength is 31.37 kV / mm, the corona resistance time under a test voltage of 1.8 kV can reach 13.5 h, the initial partial discharge voltage of a discharge amount of 10 pC is 0.76 kV, and the aging retention rate and mechanical properties are shown in Table 1. Among them, the electrical performance is tested by the national standard GB / T 1408.1-2006, and the mechanical performance is tested by the national standard: GB / T 12914-2008, and the same below.

[0042] Comparative Example 1:

[0043] A preparation method of aramid mica paper, the aramid mica paper comprises components A, B and C, and comprises the following steps:

[0044] 1. Preparation of component A:

[0045] 30% of unmodified meta-aramid fiber is defibrated in a defibrator at a speed of 3000 rpm / min for 10 min, and is prepared for use.

[0046] 2. Preparation of component B:

[0047] 15% of meta-aramid short fibers with a length of 5 mm are stirred in a defibrator at a speed of 3000 rpm / min for 2 min, and are prepared for use.

[0048] 3. Preparation of component C:

[0049] Component C is calcined mica and synthetic mica, the particle size of the calcined mica is 70-120 μm, the particle size of the synthetic mica is 90-180 μm, and the ratio of the synthetic mica to the calcined mica is 1:10 (w / w). 55% of the mica is defibrated in a defibrator at a speed of 3000 rpm / min for 1 min, and is prepared for use.

[0050] 4. Preparation of aramid mica paper:

[0051] The above-mentioned components A, B and C are mixed (i.e. the mass ratio of the modified meta-aramid fiber, the meta-aramid short fiber and the mica is 30:15:55), are uniformly mixed in a defibrator, are papered in a PTI Keeser method rapid paper former, are watered 5 L, are bubbled for 10 s, are placed for 5 s, are dehydrated and dried to obtain aramid mica paper. The aramid mica paper is hot-pressed to obtain aramid mica paper, and the hot-pressing conditions are temperature: 280℃, pressure: 3 MPa, and vehicle speed: 4 m / min.

[0052] The performance of the above-mentioned aramid mica paper is tested, and the results are as follows:

[0053] The electrical strength is 21.62 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 6.5 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.52 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0054] Example 2:

[0055] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0056] 1. Preparation of Component A:

[0057] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 3:17 (v / v), a flow rate of 3 SLM, and a treatment time of 5 minutes. 40% by weight of the modified meta-aramid fibrids were then deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0058] 2. Preparation of component B:

[0059] 10% by weight of meta-aramid short-cut fibers with a length of 7 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0060] 3. Preparation of component C:

[0061] Component C is composed of calcined mica with a particle size of 70-120 μm. 50% of the calcined mica by weight is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0062] 4. Preparation of aramid mica paper:

[0063] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 40:10:50) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with 4 L of water added, a bubbling time of 10 seconds, a 5-second rest period, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 300°C, a pressure of 3 MPa, and a speed of 5 m / min to obtain aramid mica paper.

[0064] The performance test results of the above aramid mica paper are as follows:

[0065] The electrical strength is 41.18 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 21.5 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.64 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0066] Comparative Example 2:

[0067] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0068] 1. Preparation of Component A:

[0069] 40% by weight of unmodified meta-aramid fibrils were deflaked in a deflaker at a speed of 3000 rpm / min for 10 minutes and set aside.

[0070] 2. Preparation of component B:

[0071] 10% by weight of meta-aramid short-cut fibers with a length of 7 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0072] 3. Preparation of component C:

[0073] Component C is composed of calcined mica with a particle size of 70-120 μm. 50% of the calcined mica by weight is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0074] 4. Preparation of aramid mica paper:

[0075] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 40:10:50) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with 4 L of water added, a bubbling time of 10 seconds, a 5-second rest period, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 300°C, a pressure of 3 MPa, and a speed of 5 m / min to obtain aramid mica paper.

[0076] The performance test results of the above aramid mica paper are as follows:

[0077] The electrical strength is 26.79 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 10.1 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.55 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0078] Example 3:

[0079] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0080] 1. Preparation of Component A:

[0081] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 1:19 (v / v), a flow rate of 0.5 SLM, and a treatment time of 5 minutes. 45% by weight of the modified meta-aramid fibrids were then deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0082] 2. Preparation of component B:

[0083] 15% by weight of meta-aramid short-cut fibers with a length of 7 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0084] 3. Preparation of component C:

[0085] Component C consists of calcined mica and synthetic mica. The calcined mica has a particle size of 70-120 μm, while the synthetic mica has a particle size of 90-180 μm. The ratio of synthetic mica to calcined mica is 1:5 (w / w). 40% of the mica by weight is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0086] 4. Preparation of aramid mica paper:

[0087] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 45:15:40) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with a water injection of 9 L, a bubbling time of 10 seconds, a rest period of 5 seconds, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 310°C, a pressure of 4 MPa, and a speed of 5 m / min to obtain aramid mica paper.

[0088] The performance test results of the above aramid mica paper are as follows:

[0089] The electrical strength is 42.61 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 17 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.67 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0090] Example 4:

[0091] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0092] 1. Preparation of Component A:

[0093] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 1:19 (v / v), a flow rate of 0.5 SLM, and a treatment time of 5 minutes. 45% by weight of the modified meta-aramid fibrids were then deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0094] 2. Preparation of component B:

[0095] 15% by weight of meta-aramid short-cut fibers with a length of 7 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0096] 3. Preparation of component C:

[0097] Component C is composed of calcined mica with a particle size of 70-120 μm. Only calcined mica is used. 40% by weight of the calcined mica is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0098] 4. Preparation of aramid mica paper:

[0099] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 45:15:40) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with a water injection of 9 L, a bubbling time of 10 seconds, a rest period of 5 seconds, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 310°C, a pressure of 4 MPa, and a speed of 5 m / min to obtain aramid mica paper.

[0100] The performance test results of the above aramid mica paper are as follows:

[0101] The electrical strength was 42.75 kV / mm, the corona resistance time at a test voltage of 1.8 kV reached 20 hours, the onset partial discharge voltage at a discharge of 10 pC was 0.74 kV, and the aging retention and mechanical properties are shown in Table 1. This example does not use synthetic mica. Although the mechanical and electrical properties are slightly higher than those of Example 3, the aging electrical strength retention is low, and the high-temperature resistance is reduced.

[0102] Example 5:

[0103] A preparation method of aramid mica paper, the aramid mica paper comprises components A, B and C, and comprises the following steps:

[0104] 1. Preparation of component A:

[0105] The meta-aramid fiber is subjected to CF4 plasma modification, and the modification conditions are as follows: the addition ratio of CF4 gas to Ar gas is 1:10 (v / v), the flow rate is 2 SLM, and the treatment time is 5 min. 45% of the modified meta-aramid fiber is subjected to defibration in a defibrator at a rotation speed of 3000 rpm / min for 10 min.

[0106] 2. Preparation of component B:

[0107] 15% of the meta-aramid short fiber with a length of 6 mm is stirred in a defibrator at a rotation speed of 3000 rpm / min for 2 min.

[0108] 3. Preparation of component C:

[0109] The component C is calcined mica and synthetic mica, the particle size of the calcined mica is 70-120 μm, the particle size of the synthetic mica is 90-180 μm, and the ratio of the synthetic mica to the calcined mica is 1:4 (w / w). 40% of the mica is subjected to defibration in a defibrator at a rotation speed of 3000 rpm / min for 1 min.

[0110] 4. Preparation of aramid mica paper:

[0111] The components A, B and C are mixed (i.e., the mass ratio of the modified meta-aramid fiber, the meta-aramid short fiber and the mica is 45:15:40), and then mixed uniformly in a defibrator. The aramid mica paper is obtained by papermaking in a PTI Keeser method rapid paper former, water injection 9 L, bubbling time 10 s, standing for 5 s, dehydration and drying. The aramid mica paper is obtained by hot pressing of the aramid mica paper, and the hot pressing conditions are as follows: temperature: 310°C, pressure: 4 MPa, and speed: 5 m / min.

[0112] The performance of the aramid mica paper is tested, and the results are as follows:

[0113] The electrical strength is 42.76 kV / mm, the corona resistance time under a test voltage of 1.8 kV can reach 17.2 h, the initial partial discharge voltage under a discharge amount of 10 pC is 0.71 kV, and the aging retention rate and the mechanical properties are shown in Table 1.

[0114] Example 6:

[0115] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0116] 1. Preparation of Component A:

[0117] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 1:10 (v / v), a flow rate of 2 SLM, and a treatment time of 5 minutes. 45% by weight of the modified meta-aramid fibrids were then deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0118] 2. Preparation of component B:

[0119] 15% by weight of meta-aramid short-cut fibers with a length of 6 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0120] 3. Preparation of component C:

[0121] Component C is composed of calcined mica, the particle size of the calcined mica is 70-120 μm, 40% of the calcined mica is taken by weight, and is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0122] 4. Preparation of aramid mica paper:

[0123] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 45:15:40) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with a water injection of 9 L, a bubbling time of 10 seconds, a rest period of 5 seconds, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 310°C, a pressure of 4 MPa, and a speed of 5 m / min to obtain aramid mica paper.

[0124] The performance test results of the above aramid mica paper are as follows:

[0125] The electrical strength is 41.53 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 15 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.72 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0126] Example 7:

[0127] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0128] 1. Preparation of Component A:

[0129] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 1:25 (v / v), a flow rate of 5 SLM, and a treatment time of 5 minutes. 50% by weight of the modified meta-aramid fibrids were then deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0130] 2. Preparation of component B:

[0131] 10% by weight of meta-aramid short-cut fibers with a length of 5 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0132] 3. Preparation of component C:

[0133] Component C consists of calcined mica and synthetic mica. The calcined mica has a particle size of 70-120 μm, while the synthetic mica has a particle size of 90-180 μm. The ratio of synthetic mica to calcined mica is 1:15 (w / w). 40% of the mica by weight is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0134] 4. Preparation of aramid mica paper:

[0135] Mix the above three components (A, B, and C) (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica is 50:10:40) and mix thoroughly using a deflaker. Form paper in a PTI Kaiser rapid paper former by adding 5 L of water, bubbling for 10 seconds, allowing it to rest for 5 seconds, dehydrating, and drying to obtain aramid mica-based paper. Hot pressing the prepared paper at a temperature of 300°C, a pressure of 4 MPa, and a speed of 4 m / min yields aramid mica paper.

[0136] The performance test results of the above aramid mica paper are as follows:

[0137] The electrical strength is 43.09 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 22.5 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.81 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0138] Comparative Example 3:

[0139] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0140] 1. Preparation of Component A:

[0141] 50% by weight of unmodified meta-aramid fibrils were deflaked in a deflaker at a speed of 3000 rpm / min for 10 minutes and set aside.

[0142] 2. Preparation of component B:

[0143] 10% by weight of meta-aramid short-cut fibers with a length of 5 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0144] 3. Preparation of component C:

[0145] Component C is composed of calcined mica, the particle size of the calcined mica is 70-120 μm, 40% of the calcined mica is taken by weight, and is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0146] 4. Preparation of aramid mica paper:

[0147] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 50:10:40) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with 5 L of water added, a bubbling time of 10 seconds, a 5-second rest period, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 300°C, a pressure of 4 MPa, and a speed of 4 m / min to obtain aramid mica paper.

[0148] The performance test results of the above aramid mica paper are as follows:

[0149] The electrical strength is 43.27 kV / mm, the corona resistance time at a test voltage of 1.8 kV can reach 18.3 h, the initial partial discharge voltage with a discharge capacity of 10 pC is 0.78 kV, and the aging retention rate and mechanical properties are shown in Table 1.

[0150] Example 8:

[0151] A method for preparing aramid mica paper, wherein the aramid mica paper comprises components A, B, and C, and comprises the following steps:

[0152] 1. Preparation of Component A:

[0153] Meta-aramid fibrids were modified with CF4 plasma using a CF4 to Ar gas ratio of 10:1 (v / v), a flow rate of 3 SLM, and a treatment time of 5 minutes. 30% by weight of the modified meta-aramid fibrids were deflaked in a deflaker at 3000 rpm / min for 10 minutes and set aside.

[0154] 2. Preparation of component B:

[0155] 15% by weight of meta-aramid short-cut fibers with a length of 5 mm were stirred at a speed of 3000 rpm / min for 2 minutes and set aside.

[0156] 3. Preparation of component C:

[0157] Component C consists of calcined mica and synthetic mica. The calcined mica has a particle size of 70-120 μm, while the synthetic mica has a particle size of 90-180 μm. The ratio of synthetic mica to calcined mica is 1:10 (w / w). 55% of the mica by weight is deflaked in a deflaking machine at 3000 rpm / min for 1 minute and set aside.

[0158] 4. Preparation of aramid mica paper:

[0159] Components A, B, and C were mixed (i.e., the mass ratio of modified meta-aramid fibrid, meta-aramid chopped fibers, and mica was 30:15:55) and uniformly mixed using a deflaker. The mixture was then made into paper in a PTI Kaiser rapid paper former, with 5 L of water added, a bubbling time of 10 seconds, a 5-second rest period, dehydration, and drying to obtain aramid mica-based paper. The paper was then hot-pressed at a temperature of 300°C, a pressure of 4 MPa, and a speed of 4 m / min to obtain aramid mica paper.

[0160] The performance test results of the above aramid mica paper are as follows:

[0161] The electrical strength was 25.22 kV / mm, the corona resistance time at a test voltage of 1.8 kV reached 10.9 h, the onset partial discharge voltage at a discharge of 10 pC was 0.49 kV, and the aging retention and mechanical properties are shown in Table 1. In this embodiment, plasma modification using a gas with an excessively high CF4 gas content resulted in excessive grafting of fluorine ions, which in turn affected the electrical and mechanical properties of the aramid mica paper.

[0162] Table 1: Aging retention rates and mechanical properties of Examples 1-8 and Comparative Examples 1-3

[0163]

[0164] Note: Aging retention rate refers to the retention rate of electrical strength.

Claims

1. A method for preparing aramid mica paper, characterized in that: The following steps are involved: (1) The meta-aramid fibrid is modified by CF4 plasma, and the modified meta-aramid fibrid is dispersed to obtain slurry A; Dispersing meta-aramid short fibers to obtain slurry B; dispersing mica to obtain slurry C; (2) Slurry A, slurry B and slurry C are mixed evenly, and then papered and hot-pressed to obtain aramid mica paper; When meta-aramid fiber is modified by CF4 plasma, the volume ratio of CF4 gas to Ar gas is (1-5): (5-30), the flow rate is 0.1-5 SLM, and the treatment time is 1-10 min; When the modified meta-aramid fibrils are dispersed to obtain slurry A, the slurry is dispersed in a deflaker for 5-10 minutes at a speed of 1500-3000 rpm / min; The length of the meta-aramid chopped fibers is 5-7 mm; When the meta-aramid short fibers are dispersed to obtain slurry B, the slurry is dispersed in a deflaker for 2-5 minutes at a speed of 2000-3500 rpm / min; The mica is calcined mica and / or synthetic mica, the particle size of the calcined mica is 70-120 μm, the particle size of the synthetic mica is 90-180 μm, and the mass ratio of the synthetic mica to the calcined mica is (0-50):(50-100); When the mica is dispersed to obtain slurry C, the slurry is dispersed in a deflaker for 1-5 minutes at a speed of 1500-3000 rpm / min; When slurry A, slurry B and slurry C are mixed evenly, a deflaking machine is used to mix them evenly. After slurry A, slurry B and slurry C are mixed evenly, the mass ratio of the modified meta-aramid fibrils, meta-aramid short fibers and mica is (30-70): (5-25): (30-55).

2. The preparation method according to claim 1, characterized in that The mica is calcined mica and synthetic mica.

3. The preparation method according to claim 1, characterized in that During papermaking, the paper is made through a PTI Kaiser method rapid paper sheet former, 3-9 L of water is added, the bubbling time is 5-10 seconds, and it is allowed to stand for 5-10 seconds. The aramid mica paper is then dehydrated and dried. During hot pressing, the hot pressing temperature is 260-320°C, the hot pressing pressure is 0.5-5 MPa, and the hot pressing speed is 2-8 m / min.

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