A high-temperature-resistant capacitor base film and a preparation method thereof

Abstract

The application discloses a high-temperature-resistant capacitor base film and a preparation method thereof. The base film is prepared from the following raw materials in parts by weight: 100 parts of polypropylene, 15-23 parts of cyclic olefin copolymer, 5-14 parts of filler A, and 4-9 parts of filler B. The cyclic olefin copolymer is added to the polypropylene, so that the high-temperature resistance and the mechanical properties of the polypropylene can be significantly improved. The mechanical strength, the dielectric constant, the anti-breakdown strength of the polypropylene can be comprehensively improved by compounding the fillers A and B, and the heat resistance of the polypropylene can be further improved. Meanwhile, the inorganic fillers contained in the fillers A and B can be uniformly dispersed in the polypropylene, and the compatibility problem between the cyclic olefin copolymer and the polypropylene can be better solved.

Description

Technical Field

[0001] This invention relates to the field of capacitor base film materials, and in particular to a high-temperature resistant capacitor base film and its preparation method. Background Technology

[0002] Capacitor film is the core material of film capacitors. As one of the three major passive components, capacitors are widely used in various electronic products. Among them, film capacitors, benefiting from their high voltage withstand capability, good temperature characteristics, and long lifespan, have significant advantages and broad prospects in new energy fields such as new energy vehicles, photovoltaics, and wind power generation.

[0003] Polypropylene (PP) resin is a widely used material for capacitor base films. However, PP base films suffer from poor high-temperature resistance; their breakdown strength decreases rapidly with increasing temperature, especially above 100°C. At high temperatures, the breakdown strength of PP films drops sharply, leading to increased dielectric loss and making them unsuitable for high-temperature applications. Therefore, improving the high-temperature resistance of PP films is crucial for the development of capacitor films. Furthermore, improving the breakdown resistance and aging resistance of PP base films is also a problem that needs to be solved in the preparation of high-performance PP base films.

[0004] Patent CN118165421A provides a polypropylene composite material and a polypropylene film polypropylene capacitor film, which can improve heat resistance by adding cyclic olefin copolymers to polypropylene, but does not optimize the aging resistance.

[0005] Therefore, it is now necessary to improve existing technologies to provide more reliable solutions. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a high-temperature resistant capacitor base film and its preparation method, in order to address the shortcomings of the prior art.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 15-23 parts cyclic olefin copolymer, 5-14 parts filler A, and 4-9 parts filler B; Filler A is prepared through the following steps: S1-1, Acid pickling treatment is performed on the glass fiber; S1-2. Aluminum-hybridized porous barium chloride is deposited on the pickled glass fiber to obtain porous barium carbonate-coated glass fiber. S1-3, impregnated with loaded antioxidant, to obtain antioxidant barium carbonate-glass fiber composite particles; S1-4. Coating maleic anhydride-grafted polypropylene yields filler A; Filler B is a composite obtained by depositing calcium carbonate on the surface of graphene oxide and then coating it with maleic anhydride-grafted polypropylene.

[0008] Preferably, filler A is prepared by the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fiber is added to a mixed acid consisting of hydrogen peroxide and sulfuric acid, heated under reflux, and the solid is washed with deionized water until neutral and dried to obtain acid-washed glass fiber. S1-2, Porous barium chloride with deposited aluminum hybrid: Pickled glass fiber, aluminum chloride, barium chloride, and hexadecyltrimethylammonium chloride were added to deionized water and ultrasonically dispersed. The pH was then adjusted to alkaline with sodium hydroxide solution, and sodium carbonate aqueous solution was added dropwise with stirring. The resulting mixture was transferred to a reaction vessel and reacted at 140-170℃ for 2-8 hours. The mixture was then filtered, washed, dried, and calcined to obtain porous hybrid barium carbonate coated glass fiber. S1-3, Impregnated with loaded antioxidant: Porous hybrid barium carbonate coated glass fiber was added to an ethanol solution of antioxidant ODP, ultrasonically dispersed, sealed, shaken, filtered, washed, and dried to obtain antioxidant barium carbonate-glass fiber composite particles. S1-4, Maleic anhydride-coated grafted polypropylene: S1-4-1. Add the antioxidant barium carbonate-glass fiber composite particles to xylene and disperse them by ultrasonication to obtain composite particle dispersion A. S1-4-2. Maleic anhydride-grafted polypropylene is added to xylene, and composite particle dispersion A is added under continuous stirring. The mixture is heated and stirred, allowed to stand, and dried until the solvent is completely evaporated to obtain composite particles A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0009] Preferably, step S1-1 specifically includes: Glass fibers are added to a mixed acid consisting of 15-25 wt% hydrogen peroxide and 90-98 wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:(0.2-1). The mixture is heated under reflux at 80-100℃ for 4-16 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried to obtain acid-washed glass fibers. Step S1-2 is as follows: Take 0.5-2g of acid-washed glass fiber, 0.665-2.66g of aluminum chloride, 1.04-4.16g of barium chloride, and 0.8-3.2g of hexadecyltrimethylammonium chloride and add them to 100-400mL of deionized water. Disperse the mixture ultrasonically for 45-180min. Then, adjust the pH to 9-11 with 0.25-1mol / L sodium hydroxide solution. Add 10-50mL of sodium carbonate aqueous solution with a concentration of 0.05-0.2g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 140-170℃ for 2-8h. After the reaction is complete, filter the mixture, wash the solid with deionized water, dry it at 80-100℃ for 3-12h, and then calcine it in air at 750-850℃ for 1.5-6h to obtain porous hybrid barium carbonate coated glass fiber.

[0010] Preferably, steps S1-3 are as follows: Take 1.5-6g of porous hybrid barium carbonate coated glass fiber and add it to 50-200mL of ethanol solution of antioxidant ODP with a mass concentration of 2.5-10%. Disperse the solution ultrasonically for 0.5-2h, seal it, shake it overnight at 50-70℃, filter it, wash it with ethanol, and vacuum dry it at 70-90℃ for 6-24h to obtain antioxidant barium carbonate-glass fiber composite particles.

[0011] Preferably, steps S1-4 are as follows: S1-4-1. Add 1-4g of antioxidant barium carbonate-glass fiber composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion A. S1-4-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion A while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0012] Preferably, filler A is prepared by the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Porous barium chloride with deposited aluminum hybrid: 1 g of acid-washed glass fiber, 1.33 g of aluminum chloride, 2.08 g of barium chloride, and 1.6 g of hexadecyltrimethylammonium chloride were added to 200 mL of deionized water and ultrasonically dispersed for 90 min. Then, the pH was adjusted to 10 with 0.5 mol / L sodium hydroxide solution. 25 mL of 0.1 g / mL sodium carbonate aqueous solution was added dropwise with stirring. The resulting mixture was transferred to a reaction vessel and reacted at 160 °C for 4 h. After the reaction was completed, the mixture was filtered, the solid was washed with deionized water, dried at 90 °C for 6 h, and then calcined at 800 °C for 3 h in air atmosphere to obtain porous hybrid barium carbonate coated glass fiber. S1-3, Impregnated with loaded antioxidant: Take 3g of porous barium carbonate coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant barium carbonate-glass fiber composite particles. S1-4, Maleic anhydride-coated grafted polypropylene: S1-4-1. Add 2g of antioxidant barium carbonate-glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A. S1-4-2. Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0013] Preferably, filler B is prepared by the following steps: S2-1. Pretreatment of graphene oxide with a mixed acid composed of nitric acid and sulfuric acid yields acidified graphene oxide. S2-2, Calcium carbonate is deposited on the surface of acidified graphite oxide to obtain calcium carbonate-graphene oxide complex particles; S2-3. Maleic anhydride-grafted polypropylene is coated onto the surface of calcium carbonate-graphene oxide composite particles to obtain filler B.

[0014] Preferably, filler B is prepared by the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of nitric acid and sulfuric acid, heated to reflux, cooled, washed with deionized water until neutral, and dried to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: Acidified graphene oxide was added to deionized water, ultrasonically dispersed, calcium chloride was added, sodium carbonate aqueous solution was added dropwise while stirring, the reaction was stirred, filtered, washed, and dried to obtain calcium carbonate-graphene oxide complex particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add calcium carbonate-graphene oxide composite particles to xylene and disperse by ultrasonication to obtain composite particle dispersion B. S2-3-2. Add maleic anhydride-grafted polypropylene to xylene, add composite particle dispersion B while stirring, stir, let stand, and then dry until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0015] Preferably, filler B is prepared by the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 70-90°C for 3-12 hours, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: Add 0.75-3g of acidified graphene oxide to 50-200mL of deionized water, sonicate for 30-120min, add 0.4-1.7g of calcium chloride, stir for 15-60min, and add 10-40mL of sodium carbonate aqueous solution with a concentration of 0.04-0.16g / mL dropwise while stirring. Stir the reaction for 0.5-2h, filter, wash with deionized water, and vacuum dry to obtain calcium carbonate-graphene oxide composite particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add 0.5-2g of calcium carbonate-graphene oxide composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion B. S2-3-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion B while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0016] The present invention also provides a method for preparing the high-temperature resistant capacitor base film as described above, comprising the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 245-260℃ to obtain a melt; Step 2: Cool the melt and cast it into sheets; Step 3: Preheat the casting at 130-145℃, and then perform biaxial stretching at 150-165℃, with a longitudinal stretching ratio of 3-5 times and a transverse stretching ratio of 4-6.5 times. Step 4: Heat setting and cooling to obtain a high-temperature resistant capacitor base film.

[0017] The beneficial effects of this invention are: This invention provides a high-temperature resistant capacitor base film. By adding cyclic olefin copolymers to polypropylene, the high-temperature resistance and mechanical properties of polypropylene can be significantly improved. By compounding filler A and filler B, the mechanical strength, dielectric constant, and breakdown strength of polypropylene can be comprehensively improved, and the heat resistance of polypropylene can be further improved. Moreover, while achieving uniform dispersion of the inorganic fillers contained in filler A and filler B in polypropylene, the compatibility problem between cyclic olefin copolymers and polypropylene is also well solved.

[0018] In this invention, antioxidants are loaded through the microporous structure of the alumina-barium carbonate composite coating layer, and then combined with the maleic anhydride-grafted polypropylene membrane as the outermost coating layer, which can achieve a good sustained-release effect of antioxidants, thereby extending the efficacy of antioxidants and ultimately increasing the service life of polypropylene membranes.

[0019] Graphene oxide in filler B significantly improves the mechanical properties, flame retardancy, and thermal stability of polypropylene films. Calcium carbonate enhances the rigidity and heat resistance of polypropylene films. As a nucleating agent, calcium carbonate increases the crystallinity of polypropylene and reduces melt viscosity, improving flowability. In-situ synthesis and loading of calcium carbonate onto graphene oxide facilitates uniform dispersion. Simultaneously, the loaded calcium carbonate exerts a pulling effect on the two-dimensional planar graphene oxide, reducing its curling and promoting its unfolding, thus better leveraging the reinforcing effect of graphene oxide. Furthermore, the interweaving of the two-dimensional planar filler B with the linear filler A forms a network structure, further enhancing the mechanical strength and heat resistance of the polypropylene film. Attached Figure Description

[0020] Figure 1 The tensile strength test results are for embodiments and comparative examples of the present invention; Figure 2 The aging resistance test results are for embodiments and comparative examples of the present invention; Figure 3 These are the test results of the antioxidant sustained-release performance of filler A of the present invention; Figure 4 The heat shrinkage rate test results are for embodiments and comparative examples of the present invention; Figure 5The breakdown voltage test results are for embodiments and comparative examples of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0022] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0023] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available. For examples where specific conditions are not specified, conventional conditions or conditions recommended by the manufacturer are followed. For reagents or instruments whose manufacturers are not specified, they are all commercially available products.

[0024] This invention provides a high-temperature resistant capacitor base film, the raw materials for which, by weight, include: 100 parts polypropylene, 15-23 parts cyclic olefin copolymer, 5-14 parts filler A, and 4-9 parts filler B.

[0025] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 245-260℃ to obtain a melt; Step 2: Cool the melt and cast it into sheets; Step 3: Preheat the casting at 130-145℃, and then perform biaxial stretching at 150-165℃, with a longitudinal stretching ratio of 3-5 times and a transverse stretching ratio of 4-6.5 times. Step 4: Heat setting and cooling to obtain a high-temperature resistant capacitor base film.

[0026] In this invention, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers are added to a mixed acid consisting of 15-25 wt% hydrogen peroxide and 90-98 wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:(0.2-1). The mixture is heated under reflux at 80-100℃ for 4-16 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried to obtain acid-washed glass fibers. S1-2. Aluminum-hybridized porous barium chloride is deposited on the pickled glass fiber to obtain porous barium carbonate-coated glass fiber: Take 0.5-2g of acid-washed glass fiber, 0.665-2.66g of aluminum chloride, 1.04-4.16g of barium chloride, and 0.8-3.2g of hexadecyltrimethylammonium chloride and add them to 100-400mL of deionized water. Disperse the mixture ultrasonically for 45-180min. Then, adjust the pH to 9-11 with 0.25-1mol / L sodium hydroxide solution. Add 10-50mL of sodium carbonate aqueous solution with a concentration of 0.05-0.2g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 140-170℃ for 2-8h. After the reaction is complete, filter the mixture, wash the solid with deionized water, dry it at 80-100℃ for 3-12h, and then calcine it in air at 750-850℃ for 1.5-6h to obtain porous hybrid barium carbonate coated glass fiber.

[0027] S1-3, Impregnation with loaded antioxidant to obtain antioxidant barium carbonate-glass fiber composite particles: Take 1.5-6g of porous hybrid barium carbonate coated glass fiber and add it to 50-200mL of ethanol solution of antioxidant ODP with a mass concentration of 2.5-10%. Disperse the solution ultrasonically for 0.5-2h, seal it, shake it overnight at 50-70℃, filter it, wash it with ethanol, and vacuum dry it at 70-90℃ for 6-24h to obtain antioxidant barium carbonate-glass fiber composite particles.

[0028] S1-4. Coating maleic anhydride-grafted polypropylene yields filler A: S1-4-1. Add 1-4g of antioxidant barium carbonate-glass fiber composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion A. S1-4-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion A while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0029] In this invention, filler B is a composite obtained by depositing calcium carbonate on the surface of graphene oxide and then coating it with maleic anhydride-grafted polypropylene. Filler B is prepared through the following steps: S2-1. Pretreatment of graphene oxide with a mixed acid consisting of nitric acid and sulfuric acid yields acidified graphene oxide: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 70-90°C for 3-12 hours, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum to obtain acidified graphene oxide. S2-2, Calcium carbonate is deposited on the surface of acidified graphene oxide to obtain calcium carbonate-graphene oxide complex particles: Add 0.75-3g of acidified graphene oxide to 50-200mL of deionized water, sonicate for 30-120min, add 0.4-1.7g of calcium chloride, stir for 15-60min, and add 10-40mL of sodium carbonate aqueous solution with a concentration of 0.04-0.16g / mL dropwise while stirring. Stir the reaction for 0.5-2h, filter, wash with deionized water, and vacuum dry to obtain calcium carbonate-graphene oxide composite particles. S2-3. Maleic anhydride-grafted polypropylene is coated onto the surface of calcium carbonate-graphene oxide composite particles to obtain filler B: S2-3-1. Add 0.5-2g of calcium carbonate-graphene oxide composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion B. S2-3-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion B while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0030] This invention significantly improves the high-temperature resistance and mechanical properties of polypropylene by adding cyclic olefin copolymers. By compounding fillers A and B, the mechanical strength, dielectric constant, and breakdown strength of polypropylene can be comprehensively improved, and the heat resistance of polypropylene can be further enhanced. Moreover, while ensuring the uniform dispersion of the inorganic fillers contained in fillers A and B in polypropylene, the compatibility problem between cyclic olefin copolymers and polypropylene is also well solved. The main mechanism of this invention is analyzed and explained below to facilitate understanding of this invention.

[0031] Invention Mechanism: I. Cyclic Olefin Copolymers Cyclic olefin copolymers (COYCs) exhibit excellent heat resistance, with glass transition temperatures between 140-170°C and short-term heat resistance reaching 150°C. They also possess high heat distortion temperatures. Adding COYCs to polypropylene can improve its high-temperature resistance (Gopanna A, et al. European Polymer Journal, 2018, 439–451). However, COYCs have poor compatibility with polypropylene, and uneven dispersion in the polypropylene system leads to numerous mechanically weak points and areas prone to electrical breakdown, adversely affecting the mechanical properties and breakdown strength of polypropylene. In this invention, both filler A and filler B have a maleic anhydride-grafted polypropylene coating to improve their dispersion in the polypropylene system. This coating acts as an excellent compatibilizer, forming a transition component in the blend after being added to the polypropylene system. Simultaneously, it improves the compatibility between the COYC and polypropylene, thereby overcoming the aforementioned defects when COYCs are used in polypropylene.

[0032] II. Packing Material A 1. Preparation process of filler A: (1) First, the glass fiber is pickled with a mixture of hydrogen peroxide and concentrated sulfuric acid to remove surface impurities and increase surface roughness and oxygen-containing functional groups (such as carboxyl groups) to increase active sites, which is beneficial for subsequent loading. (2) Then, through hydrothermal reaction combined with high-temperature calcination, porous barium chloride coated with aluminum is deposited in situ on the glass fiber. In this process, the acid-washed glass fiber is first mixed with aluminum chloride, barium chloride, and hexadecyltrimethylammonium chloride as a template agent. 3+ Ba 2+ The aluminum hydroxide and barium hydroxide are combined with oxygen-containing functional groups such as carboxyl groups on the surface of glass fiber through coordination and electrostatic adsorption. Under alkaline conditions, precipitates (aluminum hydroxide and barium hydroxide) are formed and deposited in situ on the surface of glass fiber. Then, barium hydroxide reacts with sodium carbonate to generate barium carbonate. Finally, under high temperature calcination, aluminum hydroxide is finally converted into aluminum oxide and uniformly doped with barium carbonate to obtain an aluminum oxide-barium carbonate composite coating layer. The template agent hexadecyltrimethylammonium chloride decomposes, which causes a large number of pores to be formed on the aluminum oxide-barium carbonate composite coating layer. (3) Then, by impregnation, antioxidants are loaded into the pores of the alumina-barium carbonate composite coating layer to obtain antioxidant barium carbonate-glass fiber composite particles. (4) Finally, maleic anhydride-grafted polypropylene is coated on the surface of the antioxidant barium carbonate-glass fiber composite particles by wet coating to obtain filler A.

[0033] In packing A: The addition of glass fiber significantly improves the tensile strength, impact resistance, and flexural strength of polypropylene film. It can effectively disperse stress and reduce the deformation of the material under stress. In addition, glass fiber can also improve the heat resistance of polypropylene film, restrict the movement of polypropylene molecular chains, reduce the coefficient of thermal expansion, and enable the material to maintain shape stability at high temperatures.

[0034] Barium carbonate can improve the dielectric constant of BOPE, resulting in high breakdown strength and high energy density. Simultaneously, barium carbonate can enhance the tensile strength, modulus, and heat resistance of polypropylene films, while reducing material shrinkage and improving dimensional stability. In this invention, barium carbonate is used to coat glass fibers to form a high aspect ratio composite fiber structure, which further enhances dielectric properties and reduces barium carbonate aggregation to a certain extent, promoting its dispersion and better interaction with the polypropylene matrix.

[0035] Furthermore, the barium carbonate coating layer is uniformly doped with alumina, which further enhances the high-temperature resistance of the polypropylene film. It can also increase the crystallization temperature and mechanical properties of polypropylene. In addition, the high strength of alumina can improve the structural stability of the pores formed in the alumina-barium carbonate composite coating layer, reduce pore collapse, facilitate the loading of subsequent antioxidants, and compensate to some extent for the loss of mechanical strength caused by the formation of pore structure.

[0036] During use, especially under high-temperature environments, polypropylene membranes are prone to significant performance degradation due to thermo-oxidative aging. Adding antioxidants can improve their anti-aging properties. Furthermore, in this invention, the antioxidant is loaded onto the microporous structure of the alumina-barium carbonate composite coating layer, and combined with the outermost maleic anhydride-grafted polypropylene membrane, achieving a good sustained-release effect of the antioxidant, thereby extending its efficacy and ultimately increasing the service life of the polypropylene membrane.

[0037] The coating of maleic anhydride-grafted polypropylene solves the problems of poor dispersion and easy aggregation of inorganic materials such as glass fiber, barium carbonate, and alumina in polypropylene systems, and can also improve the compatibility between cyclic olefin copolymers and polypropylene.

[0038] III. Packing Material B 1. Preparation process of filler B: First, graphene oxide is pretreated with a mixture of concentrated nitric acid and concentrated sulfuric acid to enrich the carboxyl groups on the surface of graphene oxide, which is beneficial for subsequent deposition of calcium carbonate. Then, calcium chloride is mixed with acidified graphene oxide. Ca2+ and carboxyl groups on the surface of acidified graphene oxide are linked to the acidified graphene oxide through electrostatic and / or coordination interactions. After that, it reacts with sodium carbonate to generate calcium carbonate, thus obtaining calcium carbonate-graphene oxide complex particles. Finally, maleic anhydride-grafted polypropylene was coated onto the surface of calcium carbonate-graphene oxide composite particles using a wet coating process to obtain filler B.

[0039] In packing B: The addition of graphene oxide to polypropylene (PP) films significantly improves their mechanical properties, flame retardancy, and thermal stability. Calcium carbonate enhances the rigidity and heat resistance of PP films. As a nucleating agent, calcium carbonate increases the crystallinity of PP and also reduces melt viscosity, improving flowability. In-situ synthesis and loading of calcium carbonate onto graphene oxide facilitates uniform dispersion. Simultaneously, the loaded calcium carbonate exerts a pulling effect on the two-dimensional planar graphene oxide, reducing its curling and promoting its unfolding, thus better leveraging the reinforcing effect of graphene oxide. Furthermore, the interweaving of two-dimensional planar filler B and linear filler A forms a network structure, further enhancing the mechanical strength and heat resistance of the PP film.

[0040] The coating of maleic anhydride-grafted polypropylene solves the problems of poor dispersion and easy aggregation of inorganic materials such as graphene oxide and calcium carbonate in polypropylene systems, and can also improve the compatibility between cyclic olefin copolymers and polypropylene.

[0041] The above is the general concept of the present invention. Based on this, detailed embodiments and comparative examples are provided below to further illustrate the present invention.

[0042] Polypropylene, brand SK, grade R370Y, purchased from Suzhou Yitianli Plastics Co., Ltd. Cyclic olefin copolymer (COC), brand: Zeon 750R from Japan, purchased from Shanghai Shiruixiang Plastics Co., Ltd.; Glass fiber, diameter 9-13μm, length 1-3mm, Taian Haoda New Materials Co., Ltd.

[0043] Antioxidant ODP, Ba Shifu (Shanghai) Biomedical Technology Co., Ltd.; Maleic anhydride-grafted polypropylene, model XH3221C2DPAV, Dongguan Shenghao Plastic Raw Materials Co., Ltd. Graphene oxide, 200nm in diameter, Shanghai Maoguo Nanotechnology Co., Ltd. Barium carbonate, average particle size 0.2 μm, Nanjing Chemical Reagent Co., Ltd.

[0044] Example 1: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 8.5 parts filler A, and 6 parts filler B.

[0045] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 255°C to obtain a melt; Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0046] In this embodiment, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Porous barium chloride with deposited aluminum hybrid: S1-2-1. Take 2.6g of sodium carbonate and add it to 25mL of deionized water. Stir for 5min to obtain a sodium carbonate solution. S1-2-2. Take 1g of acid-washed glass fiber, 1.33g of aluminum chloride, 2.08g of barium chloride, and 1.6g of hexadecyltrimethylammonium chloride and add them to 200mL of deionized water. Disperse the mixture by sonication for 90min. Then adjust the pH value to 10 with 0.5mol / L sodium hydroxide solution. Add 25mL of sodium carbonate aqueous solution with a concentration of 0.1g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 160℃ for 4h. After the reaction is completed, filter the mixture. Wash the solid with deionized water and dry it at 90℃ for 6h. Then calcine it in air at 800℃ for 3h to obtain porous hybrid barium carbonate coated glass fiber. S1-4, Impregnated with antioxidant: Take 3g of porous barium carbonate coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant barium carbonate-glass fiber composite particles. S1-5, Maleic anhydride-coated grafted polypropylene: Add 2g of antioxidant barium carbonate-glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A; Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Then, add the composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0047] In this embodiment, filler B is prepared through the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 80°C for 6 h, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum at 95°C for 12 h to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: 1.5 g of acidified graphene oxide was added to 100 mL of deionized water and ultrasonically dispersed for 60 min. 0.85 g of calcium chloride was added and stirred for 30 min. 20 mL of sodium carbonate aqueous solution with a concentration of 0.08 g / mL was added dropwise while stirring. The reaction was stirred for 1 h. The mixture was filtered, washed with deionized water, and vacuum dried at 120 °C for 12 h to obtain calcium carbonate-graphene oxide composite particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add 1g of calcium carbonate-graphene oxide composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion B. S2-3-2. Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion B while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0048] Example 2: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 8 parts filler A, and 6.5 parts filler B.

[0049] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 255°C to obtain a melt; Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0050] In this embodiment, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Porous barium chloride with deposited aluminum hybrid: S1-2-1. Take 2.6g of sodium carbonate and add it to 25mL of deionized water. Stir for 5min to obtain a sodium carbonate solution. S1-2-2. Take 1.25g of acid-washed glass fiber, 1.33g of aluminum chloride, 2.08g of barium chloride, and 1.6g of hexadecyltrimethylammonium chloride and add them to 200mL of deionized water. Disperse the mixture by sonication for 90min. Then adjust the pH value to 10 with 0.5mol / L sodium hydroxide solution. Add 25mL of sodium carbonate aqueous solution with a concentration of 0.1g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 160℃ for 4h. After the reaction is completed, filter the mixture. Wash the solid with deionized water and dry it at 90℃ for 6h. Then calcine it in air at 800℃ for 3h to obtain porous hybrid barium carbonate coated glass fiber. S1-4, Impregnated with antioxidant: Take 3g of porous barium carbonate coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant barium carbonate-glass fiber composite particles. S1-5, Maleic anhydride-coated grafted polypropylene: Add 2g of antioxidant barium carbonate-glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A; Add 3.5g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0051] In this embodiment, filler B is prepared through the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 80°C for 6 h, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum at 95°C for 12 h to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: 1.5 g of acidified graphene oxide was added to 100 mL of deionized water and ultrasonically dispersed for 60 min. 0.85 g of calcium chloride was added and stirred for 30 min. 20 mL of sodium carbonate aqueous solution with a concentration of 0.08 g / mL was added dropwise while stirring. The reaction was stirred for 1 h. The mixture was filtered, washed with deionized water, and vacuum dried at 120 °C for 12 h to obtain calcium carbonate-graphene oxide composite particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add 1g of calcium carbonate-graphene oxide composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion B. S2-3-2. Add 3.5g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion B while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0052] Example 3: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 9 parts filler A, and 5.5 parts filler B.

[0053] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 255°C to obtain a melt; Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0054] In this embodiment, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Porous barium chloride with deposited aluminum hybrid: S1-2-1. Take 2.6g of sodium carbonate and add it to 25mL of deionized water. Stir for 5min to obtain a sodium carbonate solution. S1-2-2. Take 0.9g of acid-washed glass fiber, 1.33g of aluminum chloride, 2.08g of barium chloride, and 1.6g of hexadecyltrimethylammonium chloride and add them to 200mL of deionized water. Disperse the mixture by sonication for 90min. Then adjust the pH value to 10 with 0.5mol / L sodium hydroxide solution. Add 25mL of sodium carbonate aqueous solution with a concentration of 0.1g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 160℃ for 4h. After the reaction is completed, filter the mixture. Wash the solid with deionized water and dry it at 90℃ for 6h. Then calcine it in air at 800℃ for 3h to obtain porous hybrid barium carbonate coated glass fiber. S1-4, Impregnated with antioxidant: Take 3g of porous barium carbonate coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant barium carbonate-glass fiber composite particles. S1-5, Maleic anhydride-coated grafted polypropylene: Add 2g of antioxidant barium carbonate-glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A; Add 3.5g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0055] In this embodiment, filler B is prepared through the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 80°C for 6 h, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum at 95°C for 12 h to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: 1.8 g of acidified graphene oxide was added to 100 mL of deionized water and ultrasonically dispersed for 60 min. 0.85 g of calcium chloride was added and stirred for 30 min. 20 mL of sodium carbonate aqueous solution with a concentration of 0.08 g / mL was added dropwise while stirring. The reaction was stirred for 1 h, filtered, washed with deionized water, and vacuum dried at 120 °C for 12 h to obtain calcium carbonate-graphene oxide composite particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add 1g of calcium carbonate-graphene oxide composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion B. S2-3-2. Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion B while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

[0056] Comparative Example 1: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 6 parts filler B, and 1.5 parts antioxidant ODP.

[0057] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, antioxidant ODP, and filler B evenly, and then melt-extrude them at 255°C using an extruder to obtain a melt. Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0058] The preparation method of filler B is the same as in Example 1.

[0059] The only difference between Comparative Example 2 and Example 1 is that filler B is not added in this example.

[0060] Comparative Example 3: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 5 parts filler A, 6 parts filler B, and 1.5 parts antioxidant ODP.

[0061] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, filler B, and antioxidant ODP evenly, and then melt-extrude them through an extruder at 255°C to obtain a melt. Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0062] In this embodiment, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Maleic anhydride-coated grafted polypropylene: Add 2g of acid-washed glass fiber to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A; Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Then, add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain pickled glass fiber coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0063] The preparation method of filler B is the same as in Example 1.

[0064] Comparative Example 4: A high-temperature resistant capacitor base film, the raw materials for which are prepared by weight include: 100 parts polypropylene, 19 parts cyclic olefin copolymer, 7 parts filler A, 1.5 parts barium carbonate, and 6 parts filler B.

[0065] The preparation method of this high-temperature resistant capacitor base film includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, barium carbonate, and filler B evenly, and then melt-extrude them through an extruder at 255°C to obtain a melt; Step 2: Cool the melt in a casting machine and cast it into sheets at a cooling temperature of 90°C; Step 3: Preheat the casting at 140℃, and then perform biaxial stretching at 160℃, with a longitudinal stretching ratio of 4.5 times and a transverse stretching ratio of 6 times. Step 4: Heat set the stretched sheet obtained in Step 3 at 170°C for 20 seconds, then cool it to room temperature to obtain a high-temperature resistant capacitor base film.

[0066] In this embodiment, filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Deposited alumina: 1g of acid-washed glass fiber, 1.33g of aluminum chloride, and 1.6g of hexadecyltrimethylammonium chloride were added to 200mL of deionized water and ultrasonically dispersed for 90min. Then, the pH value was adjusted to 10 with 0.5mol / L sodium hydroxide solution. The resulting mixture was transferred to a reaction vessel and reacted at 160℃ for 4h. After the reaction was completed, the mixture was filtered, the solid was washed with deionized water, dried at 90℃ for 6h, and then calcined at 800℃ for 3h in air atmosphere to obtain porous alumina-coated glass fiber. S1-4, Impregnated with antioxidant: Take 3g of porous alumina-coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant glass fiber composite particles. S1-5, Maleic anhydride-coated grafted polypropylene: Add 2g of antioxidant glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A; Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Then, add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain antioxidant glass fiber composite particles coated with maleic anhydride-grafted polypropylene, i.e., filler A.

[0067] The preparation method of filler B is the same as in the implementation. The only difference between Comparative Example 5 and Example 1 is that aluminum chloride is not added in step S1-2-2 of the preparation of filler A in this example.

[0068] The only difference between Comparative Example 6 and Example 1 is that the antioxidant barium carbonate-glass fiber composite particles prepared in Example 1 are used as filler A.

[0069] The only difference between Comparative Example 7 and Example 1 is that the calcium carbonate-graphene oxide composite particles prepared in Example 1 are used as filler B.

[0070] The only difference between Comparative Example 8 and Example 1 is that the antioxidant barium carbonate-glass fiber composite particles prepared in Example 1 are used as filler A, and the calcium carbonate-graphene oxide composite particles prepared in Example 1 are used as filler B.

[0071] Performance testing 1. Tensile strength test Referring to standard ASTM D882-12, "Standard Test Methods for Tensile Properties of Films and Sheets," the tensile breaking strength of the polypropylene capacitor base films prepared in the examples and comparative examples was tested using a universal tensile testing machine. The test results are shown in Table 1 below. Figure 1 As shown: Table 1 The test results show that Examples 1-3 have high mechanical strength, while Comparative Examples 1-8 show varying degrees of decrease. Comparative Examples 1 and 2 only added filler A and filler B respectively, failing to form a network structure in the system, resulting in a significant decrease in mechanical properties. Comparative Examples 6, 7, and 8 did not coat at least one of filler A and filler B with maleic anhydride-grafted polypropylene, leading to a significant decrease in mechanical strength. Furthermore, Comparative Example 8 failed to achieve uniform dispersion of filler A and filler B and failed to improve the compatibility between the cyclic olefin copolymer and polypropylene, resulting in an even greater decrease in mechanical properties.

[0072] 2. Aging resistance (1) The base film was aged at 75%RH and 120℃ for 240h, and then the tensile breaking strength was tested. The longitudinal tensile strength retention rate was calculated as (longitudinal tensile strength after aging / longitudinal tensile strength before aging) * 100 / .

[0073] The test results are shown in Table 2 below. Figure 2 As shown: Table 2 The test results show that Examples 1-3 have excellent aging resistance, while Comparative Examples 1-8 show varying degrees of decline. Although antioxidants were added to the raw materials in Comparative Examples 1 and 3, they did not have a sustained-release function, resulting in a significant decrease in their efficacy.

[0074] (2) To further verify the antioxidant sustained-release performance of filler A, the following tests were conducted: Take 2g of the filler A prepared in Example 1 and add it to 100mL of ethanol. Stir for 30min to obtain a sample dispersion. Maintain the temperature at 50℃. Test the concentration of antioxidant ODP in the sample dispersion every 24 hours (using high performance liquid chromatography) for 360h. Calculate the cumulative release of antioxidant ODP at different times and plot the sustained-release curve. The results are as follows: Figure 3 As shown in the test results, filler A can achieve the slow release of antioxidant ODP.

[0075] 3. Heat shrinkage rate test The transverse thermal shrinkage rate of polypropylene capacitor base films prepared according to the ASTM D2732 test examples and comparative examples was measured at high temperature (130°C, 30 min). The test results are shown in Table 3 below. Figure 4 As shown: Table 3 The test results show that Examples 1-3 exhibit excellent heat resistance, while Comparative Examples 1-8 show varying degrees of decline. Comparative Examples 1 and 2, lacking fillers A and B, show a significant decrease in heat resistance. Comparative Example 3, lacking alumina and barium carbonate in filler A, suffers from reduced heat resistance. In Comparative Example 4, barium carbonate alone in the polypropylene system is difficult to disperse uniformly and fails to form a high aspect ratio structure, resulting in a significant decrease in heat resistance. Comparative Example 5 demonstrates that the alumina doped in the porous hybrid barium carbonate-coated glass fiber improves heat resistance. Comparative Examples 6, 7, and 8 failed to address the dispersion issues of fillers A and B, resulting in a significant decrease in heat resistance. Comparative Example 8, in particular, suffers an even greater decrease in heat resistance due to its failure to improve the compatibility between the cyclic olefin copolymer and polypropylene.

[0076] 4. Breakdown voltage test An insulation withstand voltage tester (HZJY-115, Hezhong Electric) was used. The test time was 20s, the cutoff voltage was 5kV, and the test was conducted at arbitrary points at 0.2m intervals along the 1.5m TD direction. The test data were recorded, and the average value of all test data was recorded as the breakdown voltage test result.

[0077] The breakdown voltage was tested at room temperature (25℃) and high temperature (150℃), and the test results are shown in Table 4 below. Figure 5 As shown: Table 4 The test results show that Examples 1-3 exhibit excellent puncture resistance, while Comparative Examples 1-8 show varying degrees of decline. Comparative Example 1, lacking filler A, shows a significant decrease in puncture resistance. Comparative Example 3, lacking barium carbonate in filler A, suffers from decreased puncture resistance. In Comparative Example 4, barium carbonate, added alone to the polypropylene system, is difficult to disperse uniformly and fails to form a high aspect ratio structure, resulting in decreased puncture resistance. Comparative Examples 6, 7, and 8 fail to address the dispersibility issues of fillers A and B, leading to decreased puncture resistance.

[0078] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details.

Claims

1. A high-temperature resistant capacitor base film, characterized in that, The raw materials for its preparation include, by weight: 100 parts polypropylene, 15-23 parts cyclic olefin copolymer, 5-14 parts filler A, and 4-9 parts filler B; Filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fiber is added to a mixed acid consisting of hydrogen peroxide and sulfuric acid, heated under reflux, and the solid is washed with deionized water until neutral and dried to obtain acid-washed glass fiber. S1-2, Porous barium carbonate with deposited aluminum hybrid: Pickled glass fiber, aluminum chloride, barium chloride, and hexadecyltrimethylammonium chloride were added to deionized water and ultrasonically dispersed. The pH was then adjusted to alkaline with sodium hydroxide solution, and sodium carbonate aqueous solution was added dropwise with stirring. The resulting mixture was transferred to a reaction vessel and reacted at 140-170℃ for 2-8 hours. The mixture was then filtered, washed, dried, and calcined to obtain porous hybrid barium carbonate coated glass fiber. S1-3, Impregnated with loaded antioxidant: Porous hybrid barium carbonate coated glass fiber was added to an ethanol solution of antioxidant ODP, ultrasonically dispersed, sealed, shaken, filtered, washed, and dried to obtain antioxidant barium carbonate-glass fiber composite particles. S1-4, Maleic anhydride-coated grafted polypropylene: S1-4-1. Add the antioxidant barium carbonate-glass fiber composite particles to xylene and disperse them by ultrasonication to obtain composite particle dispersion A. S1-4-2. Maleic anhydride-grafted polypropylene is added to xylene, and composite particle dispersion A is added under continuous stirring. The mixture is heated and stirred, allowed to stand, and dried until the solvent is completely evaporated to obtain composite particles A coated with maleic anhydride-grafted polypropylene, i.e., filler A. Filler B is prepared through the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of nitric acid and sulfuric acid, heated to reflux, cooled, washed with deionized water until neutral, and dried to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: Acidified graphene oxide was added to deionized water, ultrasonically dispersed, calcium chloride was added, sodium carbonate aqueous solution was added dropwise while stirring, the reaction was stirred, filtered, washed, and dried to obtain calcium carbonate-graphene oxide complex particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add calcium carbonate-graphene oxide composite particles to xylene and disperse by ultrasonication to obtain composite particle dispersion B. S2-3-2. Add maleic anhydride-grafted polypropylene to xylene, add composite particle dispersion B while stirring, stir, let stand, and then dry until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

2. The high-temperature resistant capacitor substrate film according to claim 1, characterized in that, Step S1-1 is as follows: Glass fibers are added to a mixed acid consisting of 15-25 wt% hydrogen peroxide and 90-98 wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:(0.2-1). The mixture is heated under reflux at 80-100℃ for 4-16 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried to obtain acid-washed glass fibers. Step S1-2 is as follows: Take 0.5-2g of acid-washed glass fiber, 0.665-2.66g of aluminum chloride, 1.04-4.16g of barium chloride, and 0.8-3.2g of hexadecyltrimethylammonium chloride and add them to 100-400mL of deionized water. Disperse the mixture ultrasonically for 45-180min. Then adjust the pH to 9-11 with 0.25-1mol / L sodium hydroxide solution. Add 10-50mL of sodium carbonate aqueous solution with a concentration of 0.05-0.2g / mL dropwise while stirring. Transfer the resulting mixture to a reaction vessel and react at 140-170℃ for 2-8h. After the reaction is complete, filter the mixture, wash the solid with deionized water, dry it at 80-100℃ for 3-12h, and then calcine it in air at 750-850℃ for 1.5-6h to obtain porous hybrid barium carbonate coated glass fiber.

3. The high-temperature resistant capacitor substrate film according to claim 1, characterized in that, Steps S1-3 are as follows: Take 1.5-6g of porous hybrid barium carbonate coated glass fiber and add it to 50-200mL of ethanol solution of antioxidant ODP with a mass concentration of 2.5-10%. Disperse the solution ultrasonically for 0.5-2h, seal it, shake it overnight at 50-70℃, filter it, wash it with ethanol, and vacuum dry it at 70-90℃ for 6-24h to obtain antioxidant barium carbonate-glass fiber composite particles.

4. The high-temperature resistant capacitor substrate film according to claim 1, characterized in that, Steps S1-4 are as follows: S1-4-1. Add 1-4g of antioxidant barium carbonate-glass fiber composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion A. S1-4-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion A while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

5. The high-temperature resistant capacitor substrate film according to claim 1, characterized in that, Filler A is prepared through the following steps: S1-1. Acid pickling treatment of glass fiber: Glass fibers were added to a mixed acid consisting of 20wt% hydrogen peroxide and 95wt% sulfuric acid in a volume ratio of 3:7, with the liquid-solid ratio controlled at 10:0.

5. The mixture was heated under reflux at 90°C for 8 hours, cooled to room temperature, washed with deionized water until neutral, and vacuum dried at 100°C for 12 hours to obtain acid-washed glass fibers. S1-2, Porous barium carbonate with deposited aluminum hybrid: 1 g of acid-washed glass fiber, 1.33 g of aluminum chloride, 2.08 g of barium chloride, and 1.6 g of hexadecyltrimethylammonium chloride were added to 200 mL of deionized water and ultrasonically dispersed for 90 min. Then, the pH was adjusted to 10 with 0.5 mol / L sodium hydroxide solution. 25 mL of 0.1 g / mL sodium carbonate aqueous solution was added dropwise with stirring. The resulting mixture was transferred to a reaction vessel and reacted at 160 °C for 4 h. After the reaction was completed, the mixture was filtered, the solid was washed with deionized water, dried at 90 °C for 6 h, and then calcined at 800 °C for 3 h in air atmosphere to obtain porous hybrid barium carbonate coated glass fiber. S1-3, Impregnated with loaded antioxidant: Take 3g of porous barium carbonate coated glass fiber and add it to 100mL of ethanol solution of antioxidant ODP with a mass concentration of 5%. Disperse it by ultrasonication for 1h, seal it, shake it overnight at 60℃, filter it, wash it with ethanol, and vacuum dry it at 80℃ for 12h to obtain antioxidant barium carbonate-glass fiber composite particles. S1-4, Maleic anhydride-coated grafted polypropylene: S1-4-1. Add 2g of antioxidant barium carbonate-glass fiber composite particles to 30mL of xylene and ultrasonically disperse for 60min to obtain composite particle dispersion A. S1-4-2. Add 4g of maleic anhydride-grafted polypropylene to 100mL of xylene and stir for 30min. Add composite particle dispersion A while stirring continuously. Stir at 110℃ for 60min, let stand for 2h, and then dry at 85℃ until the solvent is completely evaporated to obtain composite particle A coated with maleic anhydride-grafted polypropylene, i.e., filler A.

6. The high-temperature resistant capacitor substrate film according to claim 1, characterized in that, Filler B is prepared through the following steps: S2-1, Graphene oxide pretreatment: Graphene oxide was added to a mixed acid consisting of 65 wt% nitric acid and 95 wt% sulfuric acid in a volume ratio of 1:3, heated under reflux at 70-90°C for 3-12 hours, cooled to room temperature, washed with deionized water until neutral, and dried under vacuum to obtain acidified graphene oxide. S2-2, Deposited calcium carbonate: Add 0.75-3g of acidified graphene oxide to 50-200mL of deionized water, sonicate for 30-120min, add 0.4-1.7g of calcium chloride, stir for 15-60min, and add 10-40mL of sodium carbonate aqueous solution with a concentration of 0.04-0.16g / mL dropwise while stirring. Stir the reaction for 0.5-2h, filter, wash with deionized water, and vacuum dry to obtain calcium carbonate-graphene oxide composite particles. S2-3, Maleic anhydride-coated grafted polypropylene: S2-3-1. Add 0.5-2g of calcium carbonate-graphene oxide composite particles to 15-60mL of xylene and ultrasonically disperse for 30-120min to obtain composite particle dispersion B. S2-3-2. Add 2-8g of maleic anhydride-grafted polypropylene to 50-200mL of xylene and stir for 15-60min. Add composite particle dispersion B while stirring continuously. Stir at 100-130℃ for 30-120min, let stand for 1-4h, and then dry at 75-90℃ until the solvent is completely evaporated to obtain composite particles B coated with maleic anhydride-grafted polypropylene, i.e., filler B.

7. A method for preparing a high-temperature resistant capacitor substrate film as described in any one of claims 1-6, characterized in that, Includes the following steps: Step 1: Mix polypropylene, cyclic olefin copolymer, filler A, and filler B evenly, and then melt-extrude them through an extruder at 245-260℃ to obtain a melt; Step 2: Cool the melt and cast it into sheets; Step 3: Preheat the casting at 130-145℃, and then perform biaxial stretching at 150-165℃, with a longitudinal stretching ratio of 3-5 times and a transverse stretching ratio of 4-6.5 times. Step 4: Heat setting and cooling to obtain a high-temperature resistant capacitor base film.

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