A high-voltage and high-temperature resistant film for wind power capacitors and a preparation method thereof

Abstract

The present invention relates to the technical field of capacitor films, and in particular to a high-voltage and high-temperature-resistant film for a wind power capacitor and a preparation method thereof, wherein the high-voltage and high-temperature-resistant film comprises a polypropylene-based film layer, and the polypropylene-based film layer is prepared from a modified polypropylene material. By using anhydrous dichloromethane as a solvent under an inert atmosphere, 3,5-bis(trifluoromethyl)aniline and vinylsulfonyl chloride undergo a substitution reaction under certain conditions, and further undergo a graft copolymerization reaction with polypropylene under the action of an initiator to obtain a modified polypropylene material, and in the process of preparing the film, the preheating temperature, the stretching temperature and the stretching ratio of the transverse and longitudinal stretching are controlled to ensure the uniformity of the film stretching, so that the film finally prepared has good mechanical properties and high temperature resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitor films, and in particular to a high-voltage and high-temperature resistant film for wind power capacitors and a preparation method thereof. Background Art

[0002] Existing metallized capacitor films are widely used in electronics, home appliances, communications, electricity, electrified railways, hybrid vehicles, wind power generation, solar power generation and other industries. As an important energy storage device, capacitors have developed from the initial simple form to today's complex devices. Compared with batteries and electrochemical capacitors, dielectric capacitors have higher operating voltage and power density, longer life and greater cycle stability. According to the dielectric material, they can be divided into: ceramic capacitors, electrolytic capacitors, paper dielectric capacitors, polymer film capacitors, etc. With the development of advanced electronics and power systems, film capacitors with high energy storage performance have become particularly important. Polymer-based materials stand out because of their flexibility, cost-effectiveness and customizable functional characteristics, and become the main dielectric of film capacitors. These film capacitors have gradually begun to be widely used in smart grids, new energy vehicles and other fields due to their advantages such as high breakdown field strength, high power density, small dielectric loss, small size and low cost. However, due to its low dielectric constant, it is difficult to improve its capacitance and energy storage density, which hinders the further development of film capacitors.

[0003] Chinese patent application number 201710580920.9 discloses a method for preparing a high-temperature resistant polypropylene film for capacitors, wherein a polypropylene raw material is put into an extruder for extrusion, sheet casting, biaxial synchronous stretching and heat setting to form a film, and then the film is cooled, thickness measured, trimmed and corona treated, rolled up, and subjected to secondary aging treatment to obtain a high-temperature resistant polypropylene film for capacitors; Chinese patent application number 202111264985.5 discloses a biaxially oriented polypropylene film for capacitors, comprising a three-layer structure of an upper surface layer, an intermediate layer and a lower surface layer, wherein polypropylene resin A is used as the intermediate layer raw material and polypropylene resin B is used as the surface layer raw material, which are respectively fed into a main and radial double extruder for melting, and after plasticization, are extruded through a three-channel composite die head to obtain a sheet-like fluid, which is cast and formed by a chilled roller and a high-pressure air knife, and then longitudinally stretched and transversely stretched by a longitudinal stretching machine and a transverse stretching machine in turn to obtain a biaxially oriented polypropylene film for capacitors; the above-mentioned improvements to the film are mainly concentrated on the preparation process, and the performance improvement of the prepared film is limited, so the research on new dielectric materials has become a focus of attention. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a high-voltage and high-temperature-resistant film for wind power capacitors and a preparation method thereof, wherein the high-voltage and high-temperature-resistant film comprises a polypropylene-based film layer, and the polypropylene-based film layer is prepared from a modified polypropylene material. The modified polypropylene material is obtained by using anhydrous dichloromethane as a solvent under an inert atmosphere, and 3,5-di(trifluoromethyl)aniline and vinylsulfonyl chloride undergo a substitution reaction under certain conditions, and further undergoing a graft copolymerization reaction with polypropylene under the action of an initiator. The film finally prepared has good mechanical properties and high temperature resistance.

[0005] The technical solution of the present invention to solve the above problems is as follows:

[0006] A high-voltage and high-temperature resistant film for a wind power capacitor comprises a polypropylene base film layer, wherein the polypropylene base film layer is prepared from a modified polypropylene material, and the preparation process of the modified polypropylene material is as follows:

[0007] S1. In an inert atmosphere, triethylamine and 3,5-di(trifluoromethyl)aniline were added to anhydrous dichloromethane as a solvent, and vinylsulfonyl chloride was added thereto under ice bath conditions. The mixture was mixed for 20-30 minutes, and then the temperature was raised to 20-25° C., and the reaction was performed for 6-8 hours, and then the mixture was heated to reflux for 8-12 hours;

[0008] S2. Add polypropylene, initiator and the reactant obtained in step S1 into a reactor, mix them evenly and heat them to a molten state to cause a graft copolymerization reaction. After reacting for 8-12 hours, turn off the stirring, introduce inert gas into the reactor and open the piston at the lower end of the reactor to discharge the material. After passing through a cold water tank, pelletize to obtain the modified polypropylene material.

[0009] The polypropylene raw material selected in the present invention is isotactic polypropylene with an isotacticity of ≥96% and a density of 0.91 g / cm 2 , MFI≈2.5g / 10min; Isotactic polypropylene is because the methyl groups in the polypropylene molecular chain are distributed on one side of the main chain, and its structure is the most regular and very easy to crystallize. The larger the isotactic index, the higher the crystallinity, the higher the heat resistance, and the elastic modulus, tensile, bending and compressive strength also increase accordingly; the present invention uses isotactic polypropylene as a raw material to ensure that the prepared film has relatively excellent performance.

[0010] Furthermore, in step S1, the preparation process of anhydrous dichloromethane is: putting dichloromethane into a reactor, adding calcium hydride, refluxing for 3-5 hours, then distilling it out, and storing it in a 4A molecular sieve; the subsequent processing process is: adding anhydrous ethanol to the remaining calcium hydride in the reactor, stirring at room temperature until it is completely decomposed, and then pouring it into a waste liquid barrel.

[0011] Furthermore, in step S1, vinylsulfonyl chloride is added dropwise.

[0012] Furthermore, the initiator in step S2 is any one of benzoyl peroxide, dodecyl peroxide, azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, and cumene hydroperoxide.

[0013] Furthermore, in step S1, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere; and in step S2, the inert gas is nitrogen or argon.

[0014] The present invention also provides a method for preparing a high-voltage and high-temperature resistant film for a wind power capacitor, comprising the following steps:

[0015] A1, conveying the prepared modified polypropylene material to a melt extruder, extruding it through a die head, and conveying it to a roller pressing structure for cooling and film pressing to obtain a cast sheet with uniform thickness;

[0016] A2, preheating the cast sheet, stretching it longitudinally and transversely, cooling it with a cooling roller, and annealing the cooled film to obtain a polypropylene base film layer;

[0017] A3. Pre-treat the obtained polypropylene base film layer; send the pre-treated polypropylene base film layer into a vacuum coating machine, perform vacuum evaporation operation on the corona surface of the polypropylene base film layer to form a zinc coating layer, and then coat a layer of aluminum coating on the surface of the zinc coating layer and perform a temperature diffusion treatment to obtain the high-voltage and temperature-resistant film.

[0018] Furthermore, in step A1, the cooling temperature of the casting is 20-45°C.

[0019] Furthermore, in step A2, the preheating temperature is 130-140° C., and the preheating time is 80-120 seconds.

[0020] Furthermore, in step A2, the stretching ratio of the longitudinal stretching is 450-520%, the preheating temperature of the longitudinal stretching is 110-130°C, and the stretching temperature is 85-105°C; the stretching ratio of the transverse stretching is 780-900%, the preheating temperature of the transverse stretching is 165-185°C, and the stretching temperature is 140-155°C.

[0021] Since the film has an inherent stretching ratio during the stretching process, uniform stretching can only be achieved when the film is stretched to a certain ratio. If the stretching ratio is too low, a dead zone that is not stretched often occurs, affecting the uniformity of the film. Therefore, as the stretching ratio increases, the uniformity of the film stretching improves, and the uniformity of the film thickness and the surface flatness improve. Therefore, in the present invention, the sheet is stretched longitudinally at a certain rate to orient the polymer molecules longitudinally, and the preheating temperature and stretching temperature of the longitudinal stretching are controlled to be as low as possible, and the stretching ratio is as high as possible. Similarly, the preheating temperature and stretching temperature of the transverse stretching are controlled to be as low as possible, but problems may also occur if the temperature is too low. Therefore, the preheating temperature of the transverse stretching is controlled to be 165-185°C, and the stretching temperature is controlled to be 140-155°C.

[0022] Further, the obtained polypropylene base film layer is pretreated, the obtained polypropylene base film layer is first subjected to corona discharge treatment and then to aging treatment, the pretreated polypropylene base film layer is sent to a vacuum coating machine, zinc metal is sent to an evaporation crucible through a conveying mechanism in the vacuum coating machine, the zinc metal is changed from a zinc solution to zinc vapor in the evaporation crucible, a vacuum evaporation operation is performed on the corona surface of the polypropylene base film layer in a coating chamber to form a zinc coating, an aluminum wire is sent to the evaporation crucible, the aluminum wire is changed from an aluminum solution to aluminum vapor in the evaporation crucible, and an ultrasonic generator is used to generate a zinc coating. The upper surface of the zinc coating is vacuum-deposited in a coating chamber to form an aluminum coating, and further subjected to a temperature diffusion treatment to obtain the high-voltage and temperature-resistant film. The temperature diffusion treatment is divided into three stages, the first stage is at 4°C / h, from room temperature to 42°C, the second stage is at 12°C / h, from 42°C to 90°C, and the third stage is at 15°C / h, from 90°C to 120°C. The temperature treatment can effectively promote the microstructural changes of the polypropylene base film layer and the metal between the zinc coating and the aluminum coating, and improve the tightness between the polypropylene base film layer and the metal coating.

[0023] The present invention has the following beneficial effects:

[0024] In the process of preparing modified polypropylene materials, firstly, anhydrous dichloromethane is used as solvent and triethylamine is used as acid binding agent under inert atmosphere, and vinyl sulfonyl chloride is added dropwise under ice bath conditions, and then the temperature is raised, 3,5-di(trifluoromethyl)aniline and vinyl sulfonyl chloride undergo substitution reaction, and then graft copolymerization reaction with polypropylene occurs under the action of initiator to obtain modified polypropylene materials, successfully introducing functional groups such as benzene ring and sulfone group into the polypropylene polymer skeleton, thereby increasing the melting point and improving the thermal stability of the polymer; in addition, the orientation polarization ability of the high polarity sulfone group introduced into the polymer side chain under high electric field can realize the regulation of polymer structure and performance; and the introduction of high energy CF bond can enhance the thermal stability of the polymer. In addition, in the process of film preparation, the uniformity of film stretching is ensured by controlling the preheating temperature, stretching temperature and stretching ratio of transverse and longitudinal stretching. DETAILED DESCRIPTION

[0025] The following will be combined with the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] The polypropylene raw material used in the present invention was purchased from Yangzi Petrochemical Co., Ltd. (brand F401), with an isotacticity of ≥96% and a density of 0.91 g / cm 2 , MFI≈2.5g / 10min; triethylamine CAS No.: 121-44-8; 3,5-bis(trifluoromethyl)aniline CAS No.: 328-74-5; dichloromethane CAS No.: 75-09-2; vinylsulfonyl chloride CAS No.: 6608-47-5. All reagents used are commercially available.

[0027] Example 1

[0028] A high-voltage and high-temperature resistant film for a wind power capacitor comprises a polypropylene base film layer, wherein the polypropylene base film layer is prepared from a modified polypropylene material, and the preparation process of the modified polypropylene material is as follows:

[0029] S1. In a nitrogen atmosphere, 50 parts by weight of anhydrous dichloromethane was used as a solvent, 18 parts by weight of triethylamine and 32 parts by weight of 3,5-di(trifluoromethyl)aniline were added thereto, 35 parts by weight of vinylsulfonyl chloride was added thereto dropwise under ice bath conditions, the mixture was mixed for 25 minutes, the temperature was raised to 25° C., the reaction was carried out for 7 hours, and then the reaction was carried out under reflux for 10 hours;

[0030] S2. Add 42 parts by weight of polypropylene, 8 parts by weight of initiator benzoyl peroxide and the reactant obtained in step S1 into a reactor, mix them evenly and heat them to a molten state to cause a graft copolymerization reaction. After reacting for 10 hours, turn off the stirring, introduce nitrogen gas into it, open the piston at the lower end of the reactor to discharge the material, and pelletize it after passing through a cold water tank to obtain a modified polypropylene material.

[0031] The preparation process of anhydrous dichloromethane is as follows: put dichloromethane into a reactor, add calcium hydride, reflux for 5 hours, evaporate it, and store it in a 4A molecular sieve; the subsequent treatment process is as follows: add anhydrous ethanol to the remaining calcium hydride in the reactor, stir at room temperature until it is completely decomposed, and then pour it into a waste liquid barrel.

[0032] A method for preparing a high-voltage and high-temperature resistant film for a wind power capacitor comprises the following steps:

[0033] A1. The prepared modified polypropylene material is conveyed to a melt extruder, extruded through a die head, and conveyed to a roller pressing structure for cooling and film pressing to obtain a casting sheet with uniform thickness; wherein the cooling temperature of the casting sheet is 35° C.;

[0034] A2, preheating the cast sheet, then stretching it longitudinally and transversely, cooling it with a cooling roller, and annealing the cooled film to obtain a polypropylene base film layer; wherein the preheating temperature is 135°C, the preheating time is 100s; the stretching ratio of the longitudinal stretching is 500%, the preheating temperature of the longitudinal stretching is 120°C, and the stretching temperature is 95°C; the stretching ratio of the transverse stretching is 850%, the preheating temperature of the transverse stretching is 175°C, and the stretching temperature is 150°C;

[0035] A3. Pre-treat the obtained polypropylene base film layer, perform corona discharge treatment on the obtained polypropylene base film layer and then perform aging treatment on the obtained polypropylene base film layer, send the pre-treated polypropylene base film layer into a vacuum coating machine, send zinc metal into an evaporating crucible through a conveying mechanism in the vacuum coating machine, the zinc metal changes from zinc solution to zinc vapor in the evaporating crucible, vacuum evaporation is performed on the corona surface of the polypropylene base film layer in a coating chamber to form a zinc coating, send aluminum wire into the evaporating crucible, the aluminum wire changes from aluminum solution to aluminum vapor in the evaporating crucible, and under the action of an ultrasonic generator, continue to vacuum evaporation on the upper surface of the zinc coating in the coating chamber to form an aluminum coating, further perform temperature rise diffusion treatment to obtain a high-voltage and temperature-resistant thin film, wherein the temperature rise diffusion treatment is divided into three stages, the first stage is 4°C / h, from room temperature to 42°C, the second stage is 12°C / h, from 42°C to 90°C, and the third stage is 15°C / h, from 90°C to 120°C.

[0036] Example 2

[0037] Compared with Example 1, the reaction conditions in the preparation process of the modified polypropylene material and the high-pressure and temperature-resistant film are different in this example, and the rest of the process refers to Example 1.

[0038] The preparation process of modified polypropylene material is as follows:

[0039] S1. In a nitrogen atmosphere, 65 parts by weight of anhydrous dichloromethane was used as a solvent, 25 parts by weight of triethylamine and 40 parts by weight of 3,5-di(trifluoromethyl)aniline were added thereto, 45 parts by weight of vinylsulfonyl chloride was added thereto dropwise under ice bath conditions, the temperature was raised to 25° C. after mixing for 30 minutes, the reaction was performed for 8 hours, and then the reaction was performed under reflux for 12 hours;

[0040] S2. Add 52 parts by weight of polypropylene, 12 parts by weight of initiator benzoyl peroxide and the reactant obtained in step S1 into a reactor, mix them evenly and heat them to a molten state to cause a graft copolymerization reaction. After reacting for 12 hours, turn off the stirring, introduce nitrogen gas into it, open the piston at the lower end of the reactor to discharge the material, and pelletize it after passing through a cold water tank to obtain a modified polypropylene material.

[0041] In a method for preparing a high-voltage and high-temperature-resistant film for a wind power capacitor, the cooling temperature of the casting in step A1 is 45°C; the preheating temperature in step A2 is 140°C, the preheating time is 120s, the stretching ratio of longitudinal stretching is 520%, the preheating temperature of longitudinal stretching is 130°C, and the stretching temperature is 105°C; the stretching ratio of transverse stretching is 900%, the preheating temperature of transverse stretching is 185°C, and the stretching temperature is 155°C.

[0042] The rest of the process is as in Example 1.

[0043] Example 3

[0044] Compared with Example 1, the reaction conditions in the preparation process of the modified polypropylene material and the high-pressure and temperature-resistant film are different in this example, and the rest of the process refers to Example 1.

[0045] The preparation process of modified polypropylene material is as follows:

[0046] S1. In a nitrogen atmosphere, 45 parts by weight of anhydrous dichloromethane was used as a solvent, 12 parts by weight of triethylamine and 28 parts by weight of 3,5-di(trifluoromethyl)aniline were added thereto, 32 parts by weight of vinylsulfonyl chloride was added thereto dropwise under ice bath conditions, the temperature was raised to 20° C. after mixing for 20 minutes, the reaction was carried out for 6 hours, and then the reaction was carried out under reflux for 8 hours;

[0047] S2. Add 38 parts by weight of polypropylene, 6 parts by weight of initiator benzoyl peroxide and the reactant obtained in step S1 into a reactor, mix them evenly and heat them to a molten state to cause a graft copolymerization reaction. After reacting for 8 hours, turn off the stirring, introduce nitrogen gas into it, open the piston at the lower end of the reactor to discharge the material, and pelletize it after passing through a cold water tank to obtain a modified polypropylene material.

[0048] In a method for preparing a high-voltage and high-temperature-resistant film for a wind power capacitor, the cooling temperature of the casting in step A1 is 20°C; the preheating temperature in step A2 is 130°C, the preheating time is 80s, the stretching ratio of longitudinal stretching is 450%, the preheating temperature of longitudinal stretching is 110°C, and the stretching temperature is 85°C; the stretching ratio of transverse stretching is 780%, the preheating temperature of transverse stretching is 165°C, and the stretching temperature is 140°C.

[0049] The rest of the process is as in Example 1.

[0050] Comparative Example 1

[0051] Compared with Example 1, 3,5-di(trifluoromethyl)aniline was not added during the preparation of the modified polypropylene material, and the remaining processes were the same as those of Example 1.

[0052] The preparation process of the modified polypropylene material is as follows: 42 parts by weight of polypropylene, 8 parts by weight of initiator benzoyl peroxide and 35 parts by weight of vinyl sulfonyl chloride are added into a reactor, mixed evenly and heated to a molten state to cause a graft copolymerization reaction, and after reacting for 10 hours, stirring is turned off, nitrogen gas is introduced into the reactor, and the piston at the lower end of the reactor is opened to discharge the material, and the material is pelletized after passing through a cold water tank to obtain the modified polypropylene material.

[0053] Comparative Example 2

[0054] Compared with Example 1, vinyl sulfonyl chloride is not added during the preparation of the modified polypropylene material, and the remaining processes refer to Example 1.

[0055] The preparation process of the modified polypropylene material is as follows: 42 parts by weight of polypropylene and 32 parts by weight of 3,5-di(trifluoromethyl)aniline are added into a reactor, mixed evenly and heated to a molten state, stirring is turned off after the reaction for 10 hours, nitrogen gas is introduced into the reactor and the piston at the lower end of the reactor is opened to discharge the material, and pelletized after passing through a cold water tank to obtain the modified polypropylene material.

[0056] Comparative Example 3

[0057] Compared with Example 1, 3,5-di(trifluoromethyl)aniline and vinylsulfonyl chloride are directly mixed with polypropylene, and the rest of the process is the same as Example 1.

[0058] The preparation process of the modified polypropylene material is as follows: 42 parts by weight of polypropylene, 32 parts by weight of 3,5-di(trifluoromethyl)aniline and 35 parts by weight of vinylsulfonyl chloride are added into a reactor, mixed evenly and heated to a molten state, reacted for 10 hours and then the stirring was turned off, nitrogen gas was introduced into the reactor and the piston at the lower end of the reactor was opened to discharge the material, and pelletized after passing through a cold water tank to obtain the modified polypropylene material.

[0059] Comparative Example 4

[0060] Compared with Comparative Example 1, in the preparation process of the modified polypropylene material, polypropylene and vinyl sulfonyl chloride are directly mixed, and the remaining processes refer to Comparative Example 1.

[0061] The preparation process of the modified polypropylene material is as follows: 42 parts by weight of polypropylene and 35 parts by weight of vinyl sulfonyl chloride are added into a reactor, mixed evenly and heated to a molten state, stirring is turned off after the reaction for 10 hours, nitrogen gas is introduced into the reactor and the piston at the lower end of the reactor is opened to discharge the material, and pelletized after passing through a cold water tank to obtain the modified polypropylene material.

[0062] Related tests

[0063] The materials prepared in the examples and comparative examples were subjected to relevant performance tests, wherein the heat shrinkage rate was measured after heating at 120° C. for 15 min. The test results are shown in Table 1.

[0064] Table 1

[0065]

[0066] From the above data, it can be found that the test results of Examples 1-3 are better than those of Comparative Examples 1-4. From the test results of the embodiments, it can be found that the tensile strength of the prepared material is above 100 MPa, the thermal shrinkage rate (longitudinal) is about 0.7%, and the thermal shrinkage rate (transverse) is about 0.02%. In addition, the comprehensive performance of Example 1 is better, which can ensure the reliability of its use.

[0067] The materials prepared in the embodiments and comparative examples are used in the preparation of capacitors. All detection tests are carried out under the premise of ensuring safety. The prepared capacitors are subjected to relevant performance tests, wherein the breakdown strength is tested using a program-controlled withstand voltage tester, the dielectric constant is tested using a radio frequency impedance material analyzer, and the dielectric loss factor is tested using a radio frequency impedance material analyzer. The test results are shown in Table 2.

[0068] Table 2

[0069]

[0070] From the above test data analysis, it can be seen that the test results of Examples 1-3 are better than those of Comparative Examples 1-4, indicating that grafting 3,5-di(trifluoromethyl)aniline and vinylsulfonyl chloride onto polypropylene through reaction can effectively improve the comprehensive properties of polypropylene, obtain modified polypropylene materials with better comprehensive properties, and help improve the dielectric constant and breakdown strength of the film.

[0071] As an important electronic component, polypropylene film capacitors have many excellent properties. However, with the development of the electronic / electrical industry, the specific capacity and energy storage density of film capacitors made of polypropylene are difficult to improve due to the low dielectric constant. Compared with the prior art, in the present invention, a modified polypropylene material is prepared by modifying polypropylene, and a high-voltage and temperature-resistant film with better comprehensive performance is further prepared. In the process of preparing the modified polypropylene material, anhydrous dichloromethane is first used as a solvent and triethylamine is used as an acid binder under an inert atmosphere. Vinyl sulfonyl chloride is added dropwise thereto under ice bath conditions. The temperature is then raised, and 3,5-di(trifluoromethyl)aniline undergoes a substitution reaction with vinyl sulfonyl chloride. Then, a graft copolymerization reaction is carried out with polypropylene under the action of an initiator to obtain a modified polypropylene material. Functional groups such as benzene rings and sulfone groups are successfully introduced into the polypropylene polymer skeleton. The introduction of a ring structure can increase the rigidity of the molecular chain and weaken the thermal motion of the molecule. The introduction of a ring structure can minimize single bonds, thereby increasing the melting point and improving the thermal stability of the polymer. At the same time, the polypropylene raw material selected in the present invention is isotactic polypropylene, and its structure The most regular, with a higher crystallinity, and high crystallinity is also beneficial to improving the thermal stability of the polymer, and the elastic modulus, tensile, bending and compressive strengths are also improved accordingly; in addition, in the present invention, a high-polarity sulfone group is introduced into the polymer side chain, and the orientation polarization ability of the high-dipole functional group under a high electric field can realize the regulation of the polymer structure and performance, and the high dipole moment of the -SO2- side group is beneficial to the frictionless orientation polarization of the -SO2- side group dipole, so that the -SO2- side group can realize free rotation and conformational adjustment in the formed polymer network structure region and reduce the loss caused by orientation polarization; and a high-energy CF bond is also introduced into the polymer side chain, which can further enhance the thermal stability of the polymer.

[0072] In addition, during the film preparation process, the preheating temperature and stretching temperature of the longitudinal stretching are controlled to be as low as possible, and the stretching ratio is as high as possible, so that the polymer molecules are longitudinally oriented; similarly, the preheating temperature and stretching temperature of the transverse stretching are controlled to be as low as possible; and the obtained polypropylene base film layer is first subjected to corona discharge treatment and then to failure treatment, and the pretreated polypropylene base film layer is vacuum evaporated and subjected to temperature diffusion treatment to obtain a high-pressure and temperature-resistant film. During the temperature increase process, the microstructure changes of the polypropylene base film layer and the metal between the coating layers can be effectively promoted, and the tightness between the polypropylene base film layer and the metal coating layer can be improved.

[0073] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0074] Although the embodiments of the present application have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present application, and that the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high voltage and high temperature resistant film for wind power capacitors, comprising a polypropylene base film layer, characterized in that: The polypropylene-based film layer is prepared from a modified polypropylene material, and the preparation process of the modified polypropylene material is as follows: S1. In a nitrogen atmosphere, 50 parts by weight of anhydrous dichloromethane was used as a solvent, 18 parts by weight of triethylamine and 32 parts by weight of 3,5-di(trifluoromethyl)aniline were added thereto, 35 parts by weight of vinylsulfonyl chloride was added thereto dropwise under ice bath conditions, the temperature was raised to 25° C. after mixing for 25 minutes, the reaction was continued for 7 hours, and then the reaction was continued under reflux for 10 hours; S2, adding 42 parts by weight of polypropylene, 8 parts by weight of initiator benzoyl peroxide and the reactant obtained in step S1 into a reactor, mixing them evenly and heating them to a molten state to cause a graft copolymerization reaction, turning off the stirring after reacting for 10 hours, introducing nitrogen gas into the reactor and opening the piston at the lower end of the reactor to discharge the material, and pelletizing the material after passing through a cold water tank to obtain a modified polypropylene material; The preparation process of anhydrous dichloromethane is as follows: put dichloromethane into a reactor, add calcium hydride, reflux for 5 hours, evaporate it, and store it in a 4A molecular sieve; the subsequent treatment process is as follows: add anhydrous ethanol to the remaining calcium hydride in the reactor, stir at room temperature until it is completely decomposed, and then pour it into a waste liquid barrel.

2. The method for preparing a high voltage and high temperature resistant film for a wind power capacitor according to claim 1, characterized in that: The steps include: A1, conveying the prepared modified polypropylene material to a melt extruder, extruding it through a die head, and conveying it to a roller pressing structure for cooling and film pressing to obtain a cast sheet with uniform thickness; A2, preheating the cast sheet, stretching it longitudinally and transversely, cooling it with a cooling roller, and annealing the cooled film to obtain a polypropylene base film layer; A3. Pre-treat the obtained polypropylene base film layer; send the pre-treated polypropylene base film layer into a vacuum coating machine, perform vacuum evaporation operation on the corona surface of the polypropylene base film layer to form a zinc coating layer, and then coat a layer of aluminum coating on the surface of the zinc coating layer and perform a temperature diffusion treatment to obtain the high-voltage and temperature-resistant film.

3. The method for preparing a high voltage and high temperature resistant film for a wind power capacitor according to claim 2, characterized in that: The cooling temperature of the casting in step A1 is 20-45°C.

4. The method for preparing a high voltage and high temperature resistant film for a wind power capacitor according to claim 2, characterized in that: In step A2, the preheating temperature is 130-140° C. and the preheating time is 80-120 seconds.

5. The method for preparing a high voltage and high temperature resistant film for a wind power capacitor according to claim 2, characterized in that: In step A2, the stretching ratio of the longitudinal stretching is 450-520%, the preheating temperature of the longitudinal stretching is 110-130°C, and the stretching temperature is 85-105°C; the stretching ratio of the transverse stretching is 780-900%, the preheating temperature of the transverse stretching is 165-185°C, and the stretching temperature is 140-155°C.

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