Ceramic composite insulating film and method for manufacturing the same

Abstract

The application relates to the field of insulating film materials, and particularly discloses a ceramic composite insulating film and a preparation method thereof, which comprises the following raw material components in parts by weight: 100 parts of epoxy resin, 28-64 parts of composite ceramic reinforcing filler, 25-40 parts of flaky ceramic reinforcing filler, 5-11 parts of a curing agent, 1.5-4 parts of a curing accelerator, 1-4 parts of a toughening agent and 0.3-1 part of an antioxidant. The composite ceramic reinforcing filler and the flaky ceramic reinforcing filler are compounded and added, so that the mechanical strength, the insulating performance and the heat resistance of the epoxy resin-based insulating film can be comprehensively improved, meanwhile, the high heat conduction performance can be maintained, and the application scene requirements of needing to consider the insulation, heat dissipation and high-temperature resistance can be well met.

Description

Technical Field

[0001] This invention relates to the field of insulating film materials, and in particular to a ceramic composite insulating film and its preparation method. Background Technology

[0002] Insulating films are primarily used for electrical isolation and are widely applied in electronic devices, new energy batteries, power systems, semiconductor packaging, and aerospace. When used for insulation protection in electronic devices, power batteries, and new energy vehicle components, in addition to high requirements for insulation performance and mechanical strength, high requirements for thermal conductivity and high-temperature resistance are often placed on considering the product's heat dissipation performance and its high-temperature operating environment.

[0003] Epoxy resin is a widely used insulating film substrate due to its excellent electrical insulation properties, mechanical properties, and simple molding process. For example, patent CN115960556A discloses an insulating film for automotive liquid cooling plates, and patent CN117986809B describes a high thermal conductivity insulating film made of a high thermal conductivity insulating resin composition and its preparation method.

[0004] However, epoxy resin has poor thermal conductivity, typically ranging from 0.17 to 0.21 W / (m·K). Furthermore, the long-term operating temperature range for epoxy resin insulating films is generally around 120-150℃, limiting their use in certain high-temperature environments. Therefore, to further improve the long-term stability and performance of the insulating film, it is necessary to further improve the electrical insulation properties and mechanical strength of the epoxy resin.

[0005] Therefore, it is 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 ceramic composite insulating 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 ceramic composite insulating film, comprising the following raw material components in parts by weight: 100 parts epoxy resin, 28-64 parts composite ceramic reinforcing filler, 25-40 parts flake ceramic reinforcing filler, 5-11 parts curing agent, 1.5-4 parts curing accelerator, 1-4 parts toughening agent, and 0.3-1 parts antioxidant; The composite ceramic reinforced filler is prepared through the following steps: A-1. Silicon nitride powder is prepared by soaking it in a mixed acid consisting of H2O2 aqueous solution and hydrochloric acid under heating. A-2. Basalt fibers are soaked in NaOH solution under heating to obtain pretreated basalt fibers; A-3. Pretreated hydroxylated silicon nitride powder and basalt fiber are assembled to obtain a composite filler; A-4. Grafting epoxy resin-modified acrylate copolymer onto composite filler yields composite ceramic reinforced filler; The sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Hydroxylated plate-shaped hexagonal boron nitride was prepared by wet ball milling followed by hydrothermal treatment with NaOH aqueous solution. B-2. Grafting epoxy resin-modified acrylate copolymer onto hydroxylated plate-like hexagonal boron nitride yields plate-like ceramic reinforcing filler.

[0008] Preferably, step A-1 specifically involves: adding silicon nitride powder to a mixed acid consisting of H2O2 aqueous solution and hydrochloric acid, stirring and refluxing at 60-95°C for 2-8 hours, filtering, washing and drying the solid product to obtain hydroxylated silicon nitride powder.

[0009] Preferably, step A-2 specifically involves: adding basalt fibers to a NaOH solution, stirring at 60-80°C for 1-4 hours, filtering, washing and drying the solid product to obtain pretreated basalt fibers.

[0010] Preferably, step A-3 specifically includes: A-3-1. Pretreated basalt fiber, aluminum nitrate and ethanol are added to deionized water and ultrasonically dispersed to obtain dispersion 1. A-3-2. Hydroxylated silicon nitride powder is added to deionized water and ultrasonically dispersed. The resulting dispersion 2 is added to dispersion 1 under stirring. The pH is adjusted to 7.5-8.5. The resulting mixture is transferred to a reaction vessel and heated to react. After the reaction is completed, the mixture is filtered, the solid is washed, dried, calcined, cooled, and ground to obtain the composite filler.

[0011] Preferably, step A-4 specifically includes: A-4-1. Take the composite filler and add it to a mixture of deionized water and ethanol. After ultrasonic dispersion, add vinyltriethoxysilane, heat and stir to react, filter, wash the solid and disperse it in ethyl acetate to obtain a composite filler dispersion. A-4-2. Acrylic acid, methyl methacrylate, and glycidyl methacrylate are mixed to obtain a monomer mixture. A-4-3. Add a portion of the monomer mixture, epoxy resin, emulsifier, initiator, and polymerization inhibitor to ethyl acetate and stir to obtain a mixed emulsion; add the remaining monomer mixture and emulsifier to ethyl acetate and stir to obtain a monomer emulsion. A-4-4. Add the mixed emulsion to the composite filler dispersion, heat and stir to react, add monomer emulsion dropwise, raise the temperature after the dropwise addition is complete, stir to react, filter after the reaction is complete, wash and dry the solid product to obtain the composite ceramic reinforced filler.

[0012] Preferably, the composite ceramic reinforcing filler is prepared by the following steps: A-1. Add silicon nitride powder to a mixed acid consisting of 15-30wt% H2O2 aqueous solution and 20-35wt% hydrochloric acid in a volume ratio of 1:2, controlling the ratio of silicon nitride powder to mixed acid to be (10-20):1 (mg / L). Stir and reflux at 60-95℃ for 2-8 hours, filter, wash the solid product with deionized water and dry to obtain hydroxylated silicon nitride powder. A-2. Add basalt fiber to a 0.1-2M NaOH solution, controlling the ratio of basalt fiber to NaOH solution to be (8-15):1 (mg / L), stir at 55-90℃ for 1-3 hours, filter, wash the solid product with deionized water and dry to obtain pretreated basalt fiber. A-3. Preparation of composite fillers: A-3-1. Add 1-4g of pretreated basalt fiber, 1.06-4.26g of aluminum nitrate, and 30-120mL of ethanol to 60-240mL of deionized water, and ultrasonically disperse for 0.5-2h to obtain dispersion 1. A-3-2. Add 3-12g of hydroxylated silicon nitride powder to 200-900mL of deionized water and ultrasonically disperse for 0.5-2h. Add the resulting dispersion 2 to dispersion 1 under stirring and stir for 1-3h. Add 5-20wt% ammonia water dropwise to adjust the pH to 7.5-8.5. Transfer the resulting mixture to a reaction vessel and react at 200-240℃ for 4-8h. Cool, filter, wash the solid with deionized water and dry it. Then calcine at 480-600℃ for 1-3h, cool, and grind to obtain the composite filler.

[0013] A-4. Preparation of composite ceramic reinforcing fillers: A-4-1. Take 2-8g of composite filler and add it to a mixture of 10-40mL of deionized water and 65-260mL of ethanol. Disperse the mixture by ultrasonication for 30-90min. Then add 0.25-0.9g of vinyltriethoxysilane and stir the mixture at 60-80℃ for 1.5-6h. Filter the mixture, wash the solid with ethanol, and add it to 60-240mL of ethyl acetate. Disperse the mixture by ultrasonication for 0.5-2h to obtain a dispersion of composite filler. A-4-2. Mix 0.75-3g acrylic acid, 1.25-5g methyl methacrylate, and 1.3-5.2g glycidyl methacrylate to obtain a monomer mixture; A-4-3. Add 1 / 6-1 / 3 of the total mass of the monomer mixture, 2.7-10.8 g of epoxy resin, 0.4-1.6 g of emulsifier, 0.09-0.36 g of initiator, and 0.006-0.024 g of polymerization inhibitor to 40-160 mL of ethyl acetate and stir for 0.5-2 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.2-0.8 g of emulsifier to 30-120 mL of ethyl acetate and stir for 30-90 min to obtain a monomer emulsion; A-4-4. Under stirring, the mixed emulsion is added to the composite filler dispersion and stirred at 60-72℃ for 0.5-3h. The monomer emulsion is added dropwise under stirring and maintained at the temperature, and the addition is completed in 1-3h. Then the temperature is raised to 85-95℃ and stirred for 2-8h. The temperature is lowered to 30-50℃, filtered, and the solid product is washed with ethyl acetate and ethanol in sequence and dried under vacuum to obtain the composite ceramic reinforced filler.

[0014] Preferably, the sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Preparation of hydroxylated plate-like hexagonal boron nitride: B-1-1. Take hexagonal boron nitride, ethanol, deionized water and polyacrylamide, mix them and add them to a ball mill, ball mill, centrifuge the product, wash the solid and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Add the flake-shaped hexagonal boron nitride to NaOH aqueous solution, disperse it by ultrasonication, place the resulting mixture in a reaction vessel, react under heating, filter after the reaction is completed, wash, dry and grind the solid product to obtain hydroxylated flake-shaped hexagonal boron nitride. B-2. Using the same method as in step A-4, graft epoxy resin-modified acrylate copolymers onto hydroxylated plate-like hexagonal boron nitride to obtain plate-like ceramic reinforcing fillers; the specific steps are as follows: B-2-1. Hydroxylated flake-shaped hexagonal boron nitride was added to a mixture of deionized water and ethanol, ultrasonically dispersed, and then vinyltriethoxysilane was added. The mixture was heated and stirred to react, filtered, and the solid was washed and dispersed in ethyl acetate. The mixture was then ultrasonically dispersed to obtain a boron nitride dispersion. B-4-2. Mix acrylic acid, methyl methacrylate, and glycidyl methacrylate to obtain a monomer mixture; B-4-3. Add a portion of the monomer mixture, epoxy resin, emulsifier, initiator, and polymerization inhibitor to ethyl acetate and stir to obtain a mixed emulsion; add the remaining monomer mixture and emulsifier to ethyl acetate and stir to obtain a monomer emulsion. B-4-4. Under stirring, the mixed emulsion is added to the boron nitride dispersion, heated and stirred to react, and the monomer emulsion is added dropwise. After the addition is complete, the temperature is raised and the reaction is stirred. After the reaction is complete, the mixture is filtered, and the solid product is washed and dried to obtain the sheet-like ceramic reinforcing filler.

[0015] Preferably, the sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Preparation of hydroxylated plate-like hexagonal boron nitride: B-1-1. Take 5-20g of hexagonal boron nitride, 125-500mL of ethanol, 50-200mL of deionized water and 0.1-0.4g of polyacrylamide and mix them in a ball mill. Control the ball-to-material ratio to be (5-15):1. Ball mill for 6-14h. Centrifuge the product, wash the solid with ethanol and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Take 2.5-10g of plate-shaped hexagonal boron nitride and add it to 150-600mL of NaOH aqueous solution with a concentration of 2-8mol / L. After ultrasonic dispersion for 0.5-2h, place the resulting mixture in a reaction vessel and react at 150-190℃ for 2-8h. Filter the mixture, wash the solid product with deionized water until neutral, dry it under vacuum, and grind it to obtain hydroxylated plate-shaped hexagonal boron nitride. B-2. Using the same method as in step A-4, graft epoxy resin-modified acrylate copolymers onto hydroxylated plate-like hexagonal boron nitride to obtain plate-like ceramic reinforcing fillers; the specific steps are as follows: B-2-1. Take 2-8g of hydroxylated flake-shaped hexagonal boron nitride and add it to a mixture of 10-40mL of deionized water and 65-260mL of ethanol. Disperse the mixture by sonication for 30-90min. Then add 0.25-0.9g of vinyltriethoxysilane and stir the mixture at 60-80℃ for 1.5-6h. Filter the mixture, wash the solid with ethanol and add it to 60-240mL of ethyl acetate. Disperse the mixture by sonication to obtain a boron nitride dispersion. B-4-2. Mix 0.75-3g acrylic acid, 1.25-5g methyl methacrylate, and 1.3-5.2g glycidyl methacrylate to obtain a monomer mixture; B-4-3. Add 1 / 6-1 / 3 of the total mass of the monomer mixture, 2.7-10.8 g of epoxy resin, 0.4-1.6 g of emulsifier, 0.09-0.36 g of initiator, and 0.006-0.024 g of polymerization inhibitor to 40-160 mL of ethyl acetate and stir for 0.5-2 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.2-0.8 g of emulsifier to 30-120 mL of ethyl acetate and stir for 30-90 min to obtain a monomer emulsion; B-4-4. Under stirring, the mixed emulsion is added to the boron nitride dispersion and stirred at 60-72℃ for 0.5-3h. The monomer emulsion is added dropwise under stirring and maintained at the temperature, and the addition is completed in 1-3h. Then the temperature is raised to 85-95℃ and stirred for 2-8h. The temperature is lowered to 30-50℃, and the mixture is filtered. The solid product is washed with ethyl acetate and ethanol in sequence and dried under vacuum to obtain the sheet-like ceramic reinforcing filler.

[0016] Preferably, the epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0017] Preferably, the polymerization inhibitor is hydroquinone, the initiator is a mixture of azobisisobutyronitrile and N,N-dimethylaniline in a mass ratio of 1:1, and the emulsifier is a mixture of emulsifier COPS-1 and SDS in a mass ratio of 1:2.

[0018] The present invention also provides a method for preparing the ceramic composite insulating film as described above, comprising the following steps: mixing epoxy resin, composite ceramic reinforcing filler, sheet ceramic reinforcing filler, toughening agent and antioxidant, stirring at 50-85°C for 0.5-2 hours, cooling to room temperature and then adding curing agent and curing accelerator, stirring for 10-45 minutes, uniformly coating the resulting mixture onto a substrate, curing at 75-100°C for 2-10 hours and then peeling off to obtain the insulating film.

[0019] The beneficial effects of this invention are: This invention provides a ceramic composite insulating film and its preparation method. By combining and adding composite ceramic reinforcing fillers and sheet-like ceramic reinforcing fillers, the mechanical strength, insulation performance and heat resistance of the epoxy resin-based insulating film can be comprehensively improved, while maintaining high thermal conductivity. This can well meet the needs of application scenarios that require insulation, heat dissipation and high temperature resistance.

[0020] In this invention, composite ceramic reinforcing fillers with a high aspect ratio are uniformly dispersed in the insulating film matrix and interwoven to form a three-dimensional network structure, significantly improving thermal conductivity and mechanical strength. The added lamellar ceramic reinforcing fillers are interwoven and dispersed into the network structure, filling the gaps and creating a "maze effect." The lamellar structure significantly extends the charge migration path, suppressing partial discharge and electrical tree growth, thereby increasing the breakdown field strength. The three-dimensional network structure acts as an insulating skeleton, while the layered structure provides directional barrier; the combination of these two structures further enhances insulation performance. Simultaneously, the lamellar structure serves as a mechanical transfer surface for loads, while the three-dimensional network structure forms a three-dimensional load-bearing support skeleton; the combination of these two structures further improves mechanical strength. Furthermore, the lamellar structure provides in-plane heat conduction channels, which, together with the fiber-formed three-dimensional network structure, construct a multi-dimensional heat conduction network, creating more continuous heat conduction pathways and improving heat conduction efficiency and uniformity in all directions. Attached Figure Description

[0021] Figure 1 The infrared absorption spectra of silicon nitride (Si3N4) powder and hydroxylated silicon nitride powder (Si3N4-OH) prepared in Example 1 are shown. Figure 2 The infrared absorption spectra of the pretreated basalt fibers (BF-OH) and composite fillers (BF-Al-Si3N4) prepared in Example 1 are shown. Figure 3 The image shows a scanning electron microscope (SEM) image of the composite filler prepared in Example 1. Figure 4 The infrared absorption spectra of the plate-like hexagonal boron nitride (h-BN) and hydroxylated plate-like hexagonal boron nitride (BN-OH) prepared in Example 1 are shown. Figure 5 The tensile strength test results are for the examples and comparative examples; Figure 6 The breakdown field strength test results are for the examples and comparative examples; Figure 7 The thermal conductivity test results are for the examples and comparative examples; Figure 8 The tensile strength retention rate test results are for the examples and comparative examples; Figure 9 The breakdown field strength retention rate test results are for the examples and comparative examples. Detailed Implementation

[0022] 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.

[0023] 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.

[0024] 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.

[0025] This invention provides a ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 28-64 parts composite ceramic reinforcing filler, 25-40 parts flake ceramic reinforcing filler, 5-11 parts curing agent, 1.5-4 parts curing accelerator, 1-4 parts toughening agent, and 0.3-1 parts antioxidant.

[0026] The composite ceramic reinforcing filler in this invention is prepared through the following steps: A-1. Add silicon nitride powder to a mixed acid consisting of H2O2 aqueous solution and hydrochloric acid, stir and reflux at 60-95℃ for 2-8 hours, filter, wash and dry the solid product to obtain hydroxylated silicon nitride powder. A-2. Add basalt fibers to NaOH solution, stir at 60-80℃ for 1-4 hours, filter, wash and dry the solid product to obtain pretreated basalt fibers; A-3. Pretreated hydroxylated silicon nitride powder and basalt fiber are assembled to obtain a composite filler: A-3-1. Pretreated basalt fiber, aluminum nitrate and ethanol are added to deionized water and ultrasonically dispersed to obtain dispersion 1. A-3-2. Hydroxylated silicon nitride powder is added to deionized water and ultrasonically dispersed. The resulting dispersion 2 is added to dispersion 1 under stirring. The pH is adjusted to 7.5-8.5. The resulting mixture is transferred to a reaction vessel and heated to react. After the reaction is completed, the mixture is filtered, the solid is washed, dried, calcined, cooled, and ground to obtain the composite filler. A-4. Grafting epoxy resin-modified acrylate copolymers onto composite fillers yields composite ceramic-reinforced fillers: A-4-1. Take the composite filler and add it to a mixture of deionized water and ethanol. After ultrasonic dispersion, add vinyltriethoxysilane, heat and stir to react, filter, wash the solid and disperse it in ethyl acetate to obtain a composite filler dispersion. A-4-2. Acrylic acid, methyl methacrylate, and glycidyl methacrylate are mixed to obtain a monomer mixture. A-4-3. Add a portion of the monomer mixture, epoxy resin, emulsifier, initiator, and polymerization inhibitor to ethyl acetate and stir to obtain a mixed emulsion; add the remaining monomer mixture and emulsifier to ethyl acetate and stir to obtain a monomer emulsion. A-4-4. Add the mixed emulsion to the composite filler dispersion, heat and stir to react, add monomer emulsion dropwise, raise the temperature after the dropwise addition is complete, stir to react, filter after the reaction is complete, wash and dry the solid product to obtain the composite ceramic reinforced filler.

[0027] In this invention, the sheet-like ceramic reinforcing filler is prepared through the following steps: B-1. Hydroxylated plate-like hexagonal boron nitride (all hexagonal boron nitride in this invention is powder) is prepared by wet ball milling followed by hydrothermal treatment with NaOH aqueous solution: B-1-1. Take hexagonal boron nitride, ethanol, deionized water and polyacrylamide, mix them and add them to a ball mill, ball mill, centrifuge the product, wash the solid and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Add the flake-shaped hexagonal boron nitride to NaOH aqueous solution, disperse it by ultrasonication, place the resulting mixture in a reaction vessel, react under heating, filter after the reaction is completed, wash, dry and grind the solid product to obtain hydroxylated flake-shaped hexagonal boron nitride. B-2. Using the same method as in step A-4, graft epoxy resin-modified acrylate copolymers onto hydroxylated plate-like hexagonal boron nitride to obtain plate-like ceramic reinforcing fillers; the specific steps are as follows: B-2-1. Hydroxylated flake-shaped hexagonal boron nitride was added to a mixture of deionized water and ethanol, ultrasonically dispersed, and then vinyltriethoxysilane was added. The mixture was heated and stirred to react, filtered, and the solid was washed and dispersed in ethyl acetate. The mixture was then ultrasonically dispersed to obtain a boron nitride dispersion. B-4-2. Mix acrylic acid, methyl methacrylate, and glycidyl methacrylate to obtain a monomer mixture; B-4-3. Add a portion of the monomer mixture, epoxy resin, emulsifier, initiator, and polymerization inhibitor to ethyl acetate and stir to obtain a mixed emulsion; add the remaining monomer mixture and emulsifier to ethyl acetate and stir to obtain a monomer emulsion. B-4-4. Under stirring, the mixed emulsion is added to the boron nitride dispersion, heated and stirred to react, and the monomer emulsion is added dropwise. After the addition is complete, the temperature is raised and the reaction is stirred. After the reaction is complete, the mixture is filtered, and the solid product is washed and dried to obtain the sheet-like ceramic reinforcing filler.

[0028] In a preferred embodiment, the epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0029] In a preferred embodiment, the polymerization inhibitor is hydroquinone, the initiator is a mixture of azobisisobutyronitrile and N,N-dimethylaniline in a mass ratio of 1:1, and the emulsifier is a mixture of emulsifier COPS-1 and SDS in a mass ratio of 1:2.

[0030] In this invention, the combined addition of composite ceramic reinforcing fillers and sheet-like ceramic reinforcing fillers comprehensively improves the mechanical strength, insulation performance, and heat resistance of epoxy resin-based insulating films, while maintaining high thermal conductivity. This effectively meets the needs of applications requiring insulation, heat dissipation, and high-temperature resistance, such as the insulation protection of electronic devices and power batteries. The preparation and mechanism of action of the composite ceramic reinforcing fillers and sheet-like ceramic reinforcing fillers are described in detail below to facilitate understanding of this invention.

[0031] I. Composite ceramic reinforced filler 1. Preparation mechanism: First, H2O2 and hydrochloric acid were used as mixed acids to introduce a large number of hydroxyl groups on the surface of silicon nitride through conventional acid washing methods (Wu Peiyao, Bao Chonggao, Li Shijia, et al. Effect of hydroxylation combined with silane coupling agent modification on the properties of photocurable Si3N4 paste [J]. Bulletin of the Chinese Ceramic Society, 2022, 41(6):2134-2142.), to obtain hydroxylated silicon nitride powder; at the same time, the hydroxyl groups on the surface of basalt fibers were enriched by alkaline immersion treatment to obtain pretreated basalt fibers; Grafting using Al 3+ As a component of the Overseas Chinese Federation, hydroxylated silicon nitride powder is assembled and grafted onto the surface of pretreated basalt fibers through coordination and / or electrostatic adsorption, resulting in a composite filler by coating the pretreated basalt fiber surface with hydroxylated silicon nitride powder. In this process, hydrothermal aluminum salts are blended with the pretreated basalt fibers. 3+ Al coordinates with the hydroxyl groups on the surface of pretreated basalt fibers and combines with hydroxylated silicon nitride powder. 3+ It can coordinate and bind with hydroxyl groups on the surface of hydroxylated silicon nitride powder, thereby achieving the connection between the powder and the hydroxyl group. Then, through hydrothermal reaction and high-temperature calcination, Al... 3+ It is converted into Al2O3, thereby firmly grafting hydroxylated silicon nitride powder onto the surface of pretreated basalt fiber through stable chemical bonds; Finally, epoxy resin-modified acrylate copolymer grafting was performed on the composite filler: first, vinyltriethoxysilane was used to introduce double bonds that could participate in subsequent polymerization reactions on the surface of the composite filler, and then acrylic acid, methyl methacrylate, and glycidyl methacrylate were used as acrylic acid / acrylate monomers, and epoxy resin E-51 was compounded as a modifying component. The epoxy resin-modified acrylate copolymer was obtained by in-situ polymerization on the composite filler, and finally, a composite ceramic reinforced filler was obtained. The main mechanism of epoxy resin copolymerization modification of polyacrylate is: epoxy resin undergoes ring-opening reaction under the catalysis of N,N-dimethylaniline, and then copolymerizes with acrylic acid / acrylate monomers (Zhuang Caihong, Wang Hui, Yin Jian, et al. Preparation of epoxy acrylate resin and its polyurethane modification [J]. Journal of Central South University: Natural Science Edition, 2012, 43(7):6.DOI:CNKI:SUN:ZNGD.0.2012-07-017.).

[0032] 2. Mechanism of action: Silicon nitride is a ceramic material with excellent insulation and thermal conductivity. Its electrical breakdown strength is typically 15–40 kV / mm, and its theoretical intrinsic thermal conductivity can reach 200–320 W / (m·K), with practical applications typically achieving 60–90 W / (m·K). Simultaneously, it possesses high mechanical strength, thermal stability, chemical stability, and strong oxidation resistance, making it an ideal ceramic filler for insulating films. Its main drawbacks are high brittleness and susceptibility to pulverization, high surface polarity leading to agglomeration, and poor compatibility with organic matrices.

[0033] Basalt fiber is a natural mineral fiber with high mechanical strength and excellent insulation properties. It also exhibits excellent high-temperature resistance, strong chemical stability, and is flame-retardant and environmentally friendly. However, when used as a filler in insulating films, it suffers from low thermal conductivity and poor compatibility with organic matrices.

[0034] In this invention, a composite is formed by coating silicon nitride onto the surface of basalt fibers. On one hand, the silicon nitride forms a thermally conductive outer layer, which significantly improves the insufficient thermal conductivity of basalt fibers. Simultaneously, the loading effect of the basalt fibers helps promote the dispersion of silicon nitride and reduce its agglomeration. Furthermore, the basalt fibers act as a supporting skeleton, and the coating with epoxy resin-modified acrylate copolymers further mitigates the pulverization caused by the high brittleness of silicon nitride. On the other hand, the grafting of silicon nitride helps improve the surface roughness of the basalt fibers, enhancing the chemical bonding and mechanical interlocking with the matrix, reducing interfacial debonding, and increasing the interfacial connection strength with the matrix. Moreover, silicon nitride can transmit and bear loads, and basalt fibers serve as a stress-bearing supporting skeleton structure; the combination of these two elements further improves the mechanical strength of the insulating film.

[0035] In this invention, by further combining the coating of epoxy resin-modified acrylate copolymer with good compatibility with the epoxy resin matrix of the insulating film with the formation of a composite structure, the problem of poor compatibility between silicon nitride and basalt fibers and the insulating film matrix can be simultaneously solved, promoting the uniform dispersion of the two materials in the insulating film matrix, thereby better exerting their reinforcing effect. On the other hand, the acrylate copolymer itself can also act as a flexible segment to absorb impact energy, improve flexibility, and reduce microcracks.

[0036] In the epoxy resin modified acrylate copolymer of the present invention, by optimizing the formulation components and incorporating epoxy resin modification, the compatibility between the polymer and the epoxy resin insulating film matrix can be improved. The main reasons include: (1) The side chain of the introduced glycidyl methacrylate has an active glycidyl epoxy group. The chemical properties of this group are highly similar to the epoxy group of the epoxy resin itself, which improves the compatibility between the two. The epoxy group containing glycidyl acrylate has high reactivity and can undergo ring-opening addition reaction with the active functional groups in the epoxy resin system, thereby combining into the cross-linking network system of the epoxy resin in the form of covalent bonds, and finally further improving the compatibility. (2) The incorporation of epoxy resin makes the chemical structure of the polymer more similar to the epoxy resin insulating film matrix. The unreacted epoxy groups and ether bonds (from the epoxy resin skeleton) in the polymer molecule can undergo ring-opening reaction under the action of curing agent, just like the epoxy resin in the matrix. After cross-linking and curing, they form an interpenetrating network structure with the matrix, which improves the compatibility stability from the structural source.

[0037] II. Laminated ceramic reinforcing fillers Preparation mechanism: Hexagonal boron nitride powder was ball-milled to obtain plate-like hexagonal boron nitride. Then, a large number of hydroxyl groups were introduced into the plate-like hexagonal boron nitride through a hydrothermal reaction in NaOH solution to obtain hydroxylated plate-like hexagonal boron nitride. The surface of the hydroxylated plate-like hexagonal boron nitride was directly modified by reacting vinyltriethoxysilane with the hydroxyl groups, thereby introducing double bonds that can participate in subsequent polymerization reactions to obtain plate-like ceramic reinforcing filler. Finally, epoxy resin-modified acrylate copolymer was grafted onto the plate-like ceramic reinforcing filler through in-situ polymerization to obtain the final plate-like ceramic reinforcing filler. The preparation and action mechanism of this copolymer grafting are the same as those in the composite ceramic reinforcing filler.

[0038] Mechanism of action: Hexagonal boron nitride (h-BN) possesses excellent thermal conductivity, insulation properties, mechanical strength, and thermal stability. When fabricated into sheet-like hexagonal boron nitride, the high aspect ratio sheet structure forms thermally conductive pathways, thereby enhancing thermal conductivity. Furthermore, the sheet-like filler readily forms a stacked structure in the matrix, effectively transferring stress and hindering crack propagation, thus improving tensile strength while moderately mitigating brittleness. Grafting with epoxy resin-modified acrylate copolymers significantly improves their compatibility with the epoxy resin matrix, promoting their uniform dispersion in the insulating film matrix.

[0039] III. The combined effect of composite ceramic reinforced fillers and sheet-like ceramic reinforced fillers: Composite ceramic reinforcing fillers with a high aspect ratio are uniformly dispersed in the insulating film matrix and interwoven to form a three-dimensional network structure, significantly improving thermal conductivity and mechanical strength. The added lamellar ceramic reinforcing fillers are interwoven and dispersed into the network structure, filling the gaps and creating a "maze effect." The lamellar structure significantly extends the charge migration path, suppressing partial discharge and electrical tree growth, thereby increasing the breakdown field strength. The three-dimensional network structure acts as an insulating skeleton, while the layered structure provides directional barrier properties; the combination of these two structures further enhances insulation performance. Simultaneously, the lamellar structure serves as a mechanical transfer surface for loads, while the three-dimensional network structure forms a three-dimensional load-bearing support skeleton; the combination of these two structures further improves mechanical strength. Furthermore, the lamellar structure provides in-plane heat conduction channels, synergistically constructing a multi-dimensional heat conduction network with the fiber-formed three-dimensional network structure, creating more continuous heat conduction pathways, improving thermal efficiency and anisotropic heat conduction uniformity.

[0040] 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.

[0041] Information on the source of main raw materials: Epoxy resin E-51, Jiangsu Haolong Chemical Co., Ltd.; Dicyandiamide, Changzhou Tongxiang Chemical Co., Ltd.; 2-Ethyl-4-methylimidazolium, Antioxidant 1010, Jiangsu Haolong Chemical Co., Ltd.; Toughening agent CMP-410, Wenzhou Qingming Chemical Co., Ltd.; Silicon nitride powder, particle size 0.5-1μm, Shanghai Liantian Materials Technology Co., Ltd.; Basalt fiber, average diameter 16μm, average length 3mm, Jiangxi Shuobang New Materials Technology Co., Ltd.; Vinyltriethoxysilane, Nanjing Xuanhao New Materials Technology Co., Ltd.; Acrylic acid, methyl methacrylate, glycidyl methacrylate, Nantong Runfeng Petrochemical Co., Ltd.; Hexagonal boron nitride (powder), average particle size 1.2μm, Suzhou Kaifa New Materials Technology Co., Ltd.; Emulsifier COPS-1, Nanjing Baiju Technology Co., Ltd.

[0042] Example 1 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 44 parts composite ceramic reinforcing filler, 32 parts flake ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; Among them, the epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazolium, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0043] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, composite ceramic reinforcing filler, sheet ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 90°C for 6 hours before being peeled off to obtain an insulating film.

[0044] The composite ceramic reinforcing filler is prepared through the following steps: A-1. Preparation of hydroxylated silicon nitride powder: Silicon nitride powder was added to a mixed acid consisting of 25 wt% H2O2 and 30 wt% hydrochloric acid in a volume ratio of 1:2, and the ratio of silicon nitride powder to mixed acid was controlled to be 15:1 (mg / L). The mixture was stirred and refluxed at 80°C for 4 hours, filtered, and the solid product was washed with deionized water and then vacuum dried at 100°C for 10 hours to obtain hydroxylated silicon nitride powder. A-2, Basalt fiber pretreatment: Basalt fibers were added to a 0.5M NaOH solution, and the ratio of basalt fibers to NaOH solution was controlled at 10:1 (mg / L). The mixture was stirred at 70℃ for 1.5h, filtered, and the solid product was washed with deionized water and then vacuum dried at 100℃ for 8h to obtain pretreated basalt fibers. A-3. Pretreated basalt fibers and hydroxylated silicon nitride powder are assembled to obtain a composite filler: A-3-1. Add 2g of pretreated basalt fiber, 2.13g of aluminum nitrate, and 60mL of ethanol to 120mL of deionized water, and ultrasonically disperse for 1h to obtain dispersion 1. A-3-2. 6g of hydroxylated silicon nitride powder was added to 450mL of deionized water and ultrasonically dispersed for 1h. The resulting dispersion 2 was added to dispersion 1 under stirring and stirred for 90min. Then, 10wt% ammonia water was added dropwise to adjust the pH to 8. The resulting mixture was transferred to a reaction vessel and reacted at 220℃ for 6h. After cooling, the mixture was filtered. The solid was washed with deionized water and dried at 100℃ for 6h. Then, it was calcined at 500℃ for 1.5h, cooled, and ground to obtain the composite filler. A-4. Grafting epoxy resin-modified acrylate copolymers onto composite fillers yields composite ceramic-reinforced fillers: A-4-1. Take 4g of composite filler and add it to a mixture of 20mL of deionized water and 130mL of ethanol. Disperse it by sonication for 45min. Then add 0.45g of vinyltriethoxysilane and stir the mixture at 65℃ for 3h. Filter the mixture. Wash the solid with ethanol and add it to 120mL of ethyl acetate. Disperse it by sonication to obtain a composite filler dispersion. A-4-2. Mix 1.5g acrylic acid, 2.5g methyl methacrylate, and 2.6g glycidyl methacrylate to obtain a monomer mixture; A-4-3. Add 1 / 4 of the total mass of the monomer mixture, 5.4 g of epoxy resin E-51, 0.8 g of emulsifier, 0.18 g of initiator, and 0.012 g of polymerization inhibitor to 80 mL of ethyl acetate and stir for 1 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.4 g of emulsifier to 60 mL of ethyl acetate and stir for 45 min to obtain a monomer emulsion; A-4-4. Under stirring, the mixed emulsion was added to the composite filler dispersion and stirred at 65°C for 1 hour. The monomer emulsion was then added dropwise under stirring and maintained at the temperature, and the addition was completed within 1.5 hours. The temperature was then raised to 90°C and stirred for 4 hours. The temperature was then lowered to 40°C and filtered. The solid product was washed with ethyl acetate and ethanol in sequence and dried under vacuum at 80°C overnight to obtain the composite ceramic reinforced filler.

[0045] The sheet-like ceramic reinforcing filler is prepared through the following steps: B-1. Preparation of hydroxylated plate-like hexagonal boron nitride: B-1-1. Take 10g of hexagonal boron nitride, 250mL of ethanol, 100mL of deionized water and 0.2g of polyacrylamide and add them into a ball mill. Control the ball-to-material ratio to be 8:1 and ball mill for 10h. Centrifuge the product, wash the solid with ethanol and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Take 5g of flake-shaped hexagonal boron nitride and add it to 300mL of NaOH aqueous solution with a concentration of 4mol / L. After ultrasonic dispersion for 1h, place the resulting mixture in a reaction vessel and react at 170℃ for 5h. Filter the mixture, wash the solid product with deionized water until neutral, dry it under vacuum at 100℃ for 10h, and grind it to obtain hydroxylated flake-shaped hexagonal boron nitride. B-2. Grafting epoxy resin-modified acrylate copolymers onto hydroxylated plate-like hexagonal boron nitride yields plate-like ceramic reinforcing fillers. The method is basically the same as A-4, with the only difference being the proportion of some components. Specific steps include: B-2-1. Take 4.5g of hydroxylated flake-shaped hexagonal boron nitride and add it to a mixture of 20mL of deionized water and 130mL of ethanol. Disperse it by sonication for 1h. Then add 0.4g of vinyltriethoxysilane and stir the reaction at 65℃ for 3h. Filter the mixture. Wash the solid with ethanol and add it to 100mL of ethyl acetate. Disperse it by sonication for 1h to obtain a boron nitride dispersion. B-4-2. Mix 1.5g acrylic acid, 2.5g methyl methacrylate, and 2.6g glycidyl methacrylate to obtain a monomer mixture; B-4-3. Add 1 / 4 of the total mass of the monomer mixture, 5.4 g of epoxy resin E-51, 0.8 g of emulsifier, 0.18 g of initiator, and 0.012 g of polymerization inhibitor to 80 mL of ethyl acetate and stir for 1 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.4 g of emulsifier to 60 mL of ethyl acetate and stir for 45 min to obtain a monomer emulsion; B-4-4. Under stirring, the mixed emulsion was added to the boron nitride dispersion and stirred at 65°C for 1 hour. The monomer emulsion was then added dropwise under stirring and maintained at the temperature, and the addition was completed within 1.5 hours. The temperature was then raised to 90°C and stirred for 4 hours. The temperature was then lowered to 40°C and filtered. The solid product was washed with ethyl acetate and ethanol in sequence and dried under vacuum at 80°C overnight to obtain the sheet-like ceramic reinforcing filler.

[0046] The polymerization inhibitor is hydroquinone, the initiator is a mixture of azobisisobutyronitrile and N,N-dimethylaniline in a mass ratio of 1:1, and the emulsifier is a mixture of emulsifier COPS-1 (sodium allyl hydroxypropanesulfonate) and SDS (sodium dodecyl sulfate) in a mass ratio of 1:2.

[0047] Example 2 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 38 parts composite ceramic reinforcing filler, 36 parts flake ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0048] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, composite ceramic reinforcing filler, sheet ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 85°C for 6 hours before being peeled off to obtain an insulating film.

[0049] The preparation methods for the composite ceramic reinforcing filler and the sheet-like ceramic reinforcing filler are the same as in Example 1.

[0050] Example 3 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 48 parts composite ceramic reinforcing filler, 28 parts flake ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0051] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, composite ceramic reinforcing filler, sheet ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 90°C for 6 hours before being peeled off to obtain an insulating film.

[0052] The preparation methods for the composite ceramic reinforcing filler and the sheet-like ceramic reinforcing filler are the same as in Example 1.

[0053] Comparative Example 1 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 76 parts flake ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0054] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, flake ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 90°C for 6 hours before being peeled off to obtain an insulating film.

[0055] The preparation method of the sheet-like ceramic reinforcing filler is the same as in Example 1.

[0056] Comparative Example 2 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 76 parts composite ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0057] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, composite ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 90°C for 6 hours before being peeled off to obtain an insulating film.

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

[0059] Comparative Example 3 The only difference between this example and Example 1 is that: The composite ceramic reinforcing filler in this example was prepared through the following steps: A-1. Basalt fiber pretreatment, the specific steps are the same as in Example 1; A-2. Grafting epoxy resin-modified acrylate copolymers onto pretreated basalt fibers yields a composite ceramic reinforcing filler: A-2-1. Take 4g of pretreated basalt fiber and add it to a mixture of 20mL deionized water and 130mL ethanol. Disperse it by ultrasonication for 45min. Then add 0.45g of vinyltriethoxysilane and stir the mixture at 65℃ for 3h. Filter the mixture. Wash the solid with ethanol and add it to 120mL of ethyl acetate. Disperse it by ultrasonication to obtain a composite filler dispersion. A-2-2. Mix 1.5g acrylic acid, 2.5g methyl methacrylate, and 2.6g glycidyl methacrylate to obtain a monomer mixture; A-2-3. Add 1 / 4 of the total mass of the monomer mixture, 5.4 g of epoxy resin E-51, 0.8 g of emulsifier, 0.18 g of initiator, and 0.012 g of polymerization inhibitor to 80 mL of ethyl acetate and stir for 1 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.4 g of emulsifier to 60 mL of ethyl acetate and stir for 45 min to obtain a monomer emulsion; A-2-4. Under stirring, the mixed emulsion was added to the composite filler dispersion and stirred at 65°C for 1 hour. The monomer emulsion was then added dropwise under stirring and maintained at the temperature, and the addition was completed within 1.5 hours. The temperature was then raised to 90°C and stirred for 4 hours. The temperature was then lowered to 40°C and filtered. The solid product was washed with ethyl acetate and ethanol in sequence and dried under vacuum at 80°C overnight to obtain the composite ceramic reinforced filler.

[0060] Comparative Example 4 A ceramic composite insulating film comprising the following raw material components in parts by weight: 100 parts epoxy resin, 11 parts polymer-coated basalt fiber, 33 parts polymer-coated silicon nitride, 32 parts sheet ceramic reinforcing filler, 8 parts curing agent, 2.5 parts curing accelerator, 2 parts toughening agent, and 0.5 parts antioxidant; The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

[0061] The preparation method of this ceramic composite insulating film is as follows: Epoxy resin, polymer-coated basalt fiber, polymer-coated silicon nitride, sheet ceramic reinforcing filler, toughening agent, and antioxidant are mixed and stirred at 70°C for 1 hour. After cooling to room temperature, curing agent and curing accelerator are added and stirred for 30 minutes. The resulting mixture is uniformly coated on a polytetrafluoroethylene board and cured at 90°C for 6 hours before being peeled off to obtain an insulating film.

[0062] The preparation method of the sheet-like ceramic reinforcing filler is the same as in Example 1.

[0063] The polymer-coated basalt fiber is prepared through the following steps: 1-1. Basalt fiber pretreatment, the specific steps are the same as in Example 1; 1-2. Grafting epoxy resin-modified acrylate copolymer onto pretreated basalt fibers yields polymer-coated basalt fibers: 1-2-1. Take 4g of pretreated basalt fiber and add it to a mixture of 20mL deionized water and 130mL ethanol. Disperse it by ultrasonication for 45min. Then add 0.45g of vinyltriethoxysilane and stir the mixture at 65℃ for 3h. Filter the mixture. Wash the solid with ethanol and add it to 120mL of ethyl acetate. Disperse it by ultrasonication to obtain a composite filler dispersion. 1-2-2. Mix 1.5g acrylic acid, 2.5g methyl methacrylate and 2.6g glycidyl methacrylate to obtain a monomer mixture; 1-2-3. Add 1 / 4 of the total mass of the monomer mixture, 5.4 g of epoxy resin E-51, 0.8 g of emulsifier, 0.18 g of initiator, and 0.012 g of polymerization inhibitor to 80 mL of ethyl acetate and stir for 1 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.4 g of emulsifier to 60 mL of ethyl acetate and stir for 45 min to obtain a monomer emulsion; 1-2-4. Under stirring, the mixed emulsion was added to the composite filler dispersion and stirred at 65°C for 1 hour. The monomer emulsion was added dropwise under stirring and kept warm, and the addition was completed in 1.5 hours. Then the temperature was raised to 90°C and stirred for 4 hours. The temperature was lowered to 40°C and filtered. The solid product was washed with ethyl acetate and ethanol in sequence and dried under vacuum at 80°C overnight to obtain polymer-coated basalt fibers.

[0064] Polymer-coated silicon nitride is prepared through the following steps: 2-1. Preparation of hydroxylated silicon nitride powder, the specific steps are the same as in Example 1; 1-2. Grafting epoxy resin-modified acrylate copolymer onto hydroxylated silicon nitride powder yields polymer-coated silicon nitride: 1-2-1. Take 4g of hydroxylated silicon nitride powder and add it to a mixture of 20mL of deionized water and 130mL of ethanol. Disperse it by ultrasonication for 45min. Then add 0.45g of vinyltriethoxysilane and stir the mixture at 65℃ for 3h. Filter the mixture. Wash the solid with ethanol and add it to 120mL of ethyl acetate. Disperse it by ultrasonication to obtain a composite filler dispersion. 1-2-2. Mix 1.5g acrylic acid, 2.5g methyl methacrylate and 2.6g glycidyl methacrylate to obtain a monomer mixture; 1-2-3. Add 1 / 4 of the total mass of the monomer mixture, 5.4 g of epoxy resin E-51, 0.8 g of emulsifier, 0.18 g of initiator, and 0.012 g of polymerization inhibitor to 80 mL of ethyl acetate and stir for 1 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.4 g of emulsifier to 60 mL of ethyl acetate and stir for 45 min to obtain a monomer emulsion; 1-2-4. Under stirring, the mixed emulsion was added to the composite filler dispersion and stirred at 65°C for 1 hour. The monomer emulsion was added dropwise under stirring and kept warm, and the addition was completed in 1.5 hours. Then the temperature was raised to 90°C and stirred for 4 hours. The temperature was lowered to 40°C and filtered. The solid product was washed with ethyl acetate and ethanol in sequence and dried under vacuum at 80°C overnight to obtain polymer-coated silicon nitride.

[0065] Comparative Example 5 The only difference between this example and Example 1 is that: In this example, the composite filler of Example 1 is used instead of the composite ceramic reinforcing filler in the raw material components of Example 1, and the amount of composite filler added is 11 parts by weight.

[0066] Comparative Example 6 The only difference between this example and Example 1 is that: In this example, epoxy resin E-51 is not added in step A-4-3 of the preparation of composite ceramic reinforcing filler, and step A-4-2 is changed to: mix 2.5g acrylic acid, 4.5g methyl methacrylate and 5g glycidyl methacrylate to obtain a monomer mixture; In this example, epoxy resin E-51 is not added in step B-4-3 of the preparation of sheet-like ceramic reinforcing filler, and step B-4-2 is changed to: mixing 2.5g of acrylic acid, 4.5g of methyl methacrylate and 5g of glycidyl methacrylate to obtain a monomer mixture.

[0067] Comparative Example 7 The only difference between this example and Example 1 is that: In this example, the plate-shaped hexagonal boron nitride in step B-1-2 of preparing the plate-shaped ceramic reinforcing filler is replaced with hexagonal boron nitride.

[0068] I. Performance Characterization Reference Figure 1 The infrared absorption spectra of silicon nitride (Si3N4) powder and hydroxylated silicon nitride powder (Si3N4-OH) prepared in Example 1 show that the characteristic peaks of OH bonds in the spectrum of Si3N4-OH are significantly enhanced, which is attributed to the introduction of abundant hydroxyl groups.

[0069] Reference Figure 2 The infrared absorption spectra of the pretreated basalt fiber (BF-OH) and composite filler (BF-Al-Si3N4) prepared in Example 1 show that obvious OH bond characteristic peaks appeared in the BF-OH spectrum, indicating that abundant hydroxyl groups were successfully introduced into the surface of the basalt fiber through pretreatment. The characteristic peaks of Si3N4, Si-O-Si from BF, and Al-O from the BF-Al-Si3N4 spectrum indicate that the assembly of hydroxylated silicon nitride powder and pretreated basalt fiber was successfully achieved.

[0070] Reference Figure 3 The image shown is a scanning electron microscope (SEM) image of the composite filler prepared in Example 1. It can be seen that a large number of particles are grafted onto the surface of the basalt fibers in the composite filler. Figure 2 Analysis shows that these particles are Si3N4 particles grafted by Al.

[0071] Reference Figure 4 The infrared absorption spectra of the plate-like hexagonal boron nitride (h-BN) and hydroxylated plate-like hexagonal boron nitride (BN-OH) prepared in Example 1 are shown. It can be seen that the characteristic peak of the OH bond in the spectrum of BN-OH is significantly enhanced, indicating that abundant hydroxyl groups were successfully introduced into the plate-like hexagonal boron nitride.

[0072] II. Performance Testing 1. Mechanical properties The tensile strength of the insulating films prepared in the examples and comparative examples was tested in accordance with standard GB / T 1040.1-2018. 2. Insulation performance Referring to standard GB / T1408.1-2006, the breakdown field strength of the insulating films prepared in the examples and comparative examples was tested using a voltage breakdown tester. 3. Thermal conductivity The thermal conductivity of the insulating films prepared in the examples and comparative examples was tested using a thermal conductivity meter in accordance with the standard ASTM D5470-2006 (the test method was the transient planar heat source method).

[0073] 4. High temperature resistance The insulating films prepared in the examples and comparative examples were kept at 180°C for 6 hours, and then the tensile strength and breakdown field strength were tested according to the above method. The tensile strength retention rate and breakdown field strength retention rate after high-temperature treatment were calculated. Tensile strength retention rate = (Tensile strength after high-temperature treatment / Tensile strength before high-temperature treatment) × 100%; Breakdown field strength retention rate = (breakdown field strength after high temperature treatment / breakdown field strength before high temperature treatment) × 100%.

[0074] The test results are shown in Table 1 below: The test results in Table 1 show that: The insulating films prepared in Examples 1-3 have high tensile strength and breakdown field strength, good thermal conductivity, and excellent high temperature resistance, exhibiting excellent comprehensive performance. In Comparative Example 1, no composite ceramic reinforcing filler was added, and in Comparative Example 2, no sheet-like ceramic reinforcing filler was added; the overall performance of both decreased significantly. In Comparative Example 3, the assembly of hydroxylated silicon nitride powder and pretreated basalt fiber was not carried out, resulting in a significant decrease in thermal conductivity, tensile strength, breakdown field strength, and heat resistance. Comparative Example 4 uses a physical blend of pretreated basalt fiber coated with polymer and hydroxylated silicon nitride powder coated with polymer. The decrease in its overall performance indicates that assembling hydroxylated silicon nitride powder and pretreated basalt fiber into a composite can better improve the overall performance of the insulating film.

[0075] In Comparative Example 5, composite fillers were used instead of composite ceramic reinforcing fillers. However, the compatibility between hydroxylated silicon nitride powder and pretreated basalt fiber and insulating film matrix was not improved by coating epoxy resin-modified acrylate copolymer, resulting in a decrease in overall performance. Comparative Example 6 uses an acrylate copolymer to coat the composite filler, but the epoxy resin is missing, which reduces the compatibility between the composite ceramic reinforced filler and the insulating film matrix, ultimately leading to a certain degree of decrease in overall performance. The results of Comparative Example 7 show that using flake hexagonal boron nitride can better improve the insulation performance, thermal conductivity, mechanical strength and heat resistance of the insulating film than using hexagonal boron nitride powder.

[0076] 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 ceramic composite insulating film, characterized in that, It includes the following raw material components in parts by weight: 100 parts epoxy resin, 28-64 parts composite ceramic reinforcing filler, 25-40 parts flake ceramic reinforcing filler, 5-11 parts curing agent, 1.5-4 parts curing accelerator, 1-4 parts toughening agent, and 0.3-1 parts antioxidant; The composite ceramic reinforced filler is prepared through the following steps: A-1. Silicon nitride powder is prepared by soaking it in a mixed acid consisting of H2O2 aqueous solution and hydrochloric acid under heating. A-2. Basalt fibers are soaked in NaOH solution under heating to obtain pretreated basalt fibers; A-3. Pretreated hydroxylated silicon nitride powder and basalt fiber are assembled to obtain a composite filler; A-4. Grafting epoxy resin-modified acrylate copolymer onto composite filler yields composite ceramic reinforced filler; The sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Hydroxylated plate-shaped hexagonal boron nitride was prepared by wet ball milling followed by hydrothermal treatment with NaOH aqueous solution. B-2. Grafting epoxy resin-modified acrylate copolymer onto hydroxylated plate-like hexagonal boron nitride yields plate-like ceramic reinforcing filler.

2. The ceramic composite insulating film according to claim 1, characterized in that, Step A-1 is as follows: Add silicon nitride powder to a mixed acid consisting of H2O2 aqueous solution and hydrochloric acid, stir and reflux at 60-95℃ for 2-8 hours, filter, wash and dry the solid product to obtain hydroxylated silicon nitride powder. Step A-2 specifically involves adding basalt fibers to a NaOH solution, stirring at 60-80℃ for 1-4 hours, filtering, washing and drying the solid product to obtain pretreated basalt fibers.

3. The ceramic composite insulating film according to claim 2, characterized in that, Step A-3 is as follows: A-3-1. Pretreated basalt fiber, aluminum nitrate and ethanol are added to deionized water and ultrasonically dispersed to obtain dispersion 1. A-3-2. Hydroxylated silicon nitride powder is added to deionized water and ultrasonically dispersed. The resulting dispersion 2 is added to dispersion 1 under stirring. The pH is adjusted to 7.5-8.

5. The resulting mixture is transferred to a reaction vessel and heated to react. After the reaction is completed, the mixture is filtered, the solid is washed, dried, calcined, cooled, and ground to obtain the composite filler.

4. The ceramic composite insulating film according to claim 3, characterized in that, Step A-4 is as follows: A-4-1. Take the composite filler and add it to a mixture of deionized water and ethanol. After ultrasonic dispersion, add vinyltriethoxysilane, heat and stir to react, filter, wash the solid and disperse it in ethyl acetate to obtain a composite filler dispersion. A-4-2. Acrylic acid, methyl methacrylate, and glycidyl methacrylate are mixed to obtain a monomer mixture. A-4-3. Add a portion of the monomer mixture, epoxy resin, emulsifier, initiator, and polymerization inhibitor to ethyl acetate and stir to obtain a mixed emulsion; add the remaining monomer mixture and emulsifier to ethyl acetate and stir to obtain a monomer emulsion. A-4-4. Add the mixed emulsion to the composite filler dispersion, heat and stir to react, add monomer emulsion dropwise, raise the temperature after the dropwise addition is complete, stir to react, filter after the reaction is complete, wash and dry the solid product to obtain the composite ceramic reinforced filler.

5. The ceramic composite insulating film according to claim 4, characterized in that, The composite ceramic reinforced filler is prepared through the following steps: A-1. Add silicon nitride powder to a mixed acid consisting of 15-30wt% H2O2 aqueous solution and 20-35wt% hydrochloric acid in a volume ratio of 1:2, controlling the ratio of silicon nitride powder to mixed acid to be (10-20):1 (mg / L). Stir and reflux at 60-95℃ for 2-8 hours, filter, wash the solid product with deionized water and dry to obtain hydroxylated silicon nitride powder. A-2. Add basalt fiber to a 0.1-2M NaOH solution, controlling the ratio of basalt fiber to NaOH solution to be (8-15):1 (mg / L), stir at 55-90℃ for 1-3 hours, filter, wash the solid product with deionized water and dry to obtain pretreated basalt fiber. A-3. Preparation of composite fillers: A-3-1. Add 1-4g of pretreated basalt fiber, 1.06-4.26g of aluminum nitrate, and 30-120mL of ethanol to 60-240mL of deionized water, and ultrasonically disperse for 0.5-2h to obtain dispersion 1. A-3-2. Add 3-12g of hydroxylated silicon nitride powder to 200-900mL of deionized water and ultrasonically disperse for 0.5-2h. Add the resulting dispersion 2 to dispersion 1 under stirring and stir for 1-3h. Add 5-20wt% ammonia water dropwise to adjust the pH to 7.5-8.

5. Transfer the resulting mixture to a reaction vessel and react at 200-240℃ for 4-8h. Cool, filter, wash the solid with deionized water and dry it. Then calcine at 480-600℃ for 1-3h, cool, and grind to obtain the composite filler. A-4. Preparation of composite ceramic reinforcing fillers: A-4-1. Take 2-8g of composite filler and add it to a mixture of 10-40mL of deionized water and 65-260mL of ethanol. Disperse the mixture by ultrasonication for 30-90min. Then add 0.25-0.9g of vinyltriethoxysilane and stir the mixture at 60-80℃ for 1.5-6h. Filter the mixture, wash the solid with ethanol, and add it to 60-240mL of ethyl acetate. Disperse the mixture by ultrasonication for 0.5-2h to obtain a dispersion of composite filler. A-4-2. Mix 0.75-3g acrylic acid, 1.25-5g methyl methacrylate, and 1.3-5.2g glycidyl methacrylate to obtain a monomer mixture; A-4-3. Add 1 / 6-1 / 3 of the total mass of the monomer mixture, 2.7-10.8 g of epoxy resin, 0.4-1.6 g of emulsifier, 0.09-0.36 g of initiator, and 0.006-0.024 g of polymerization inhibitor to 40-160 mL of ethyl acetate and stir for 0.5-2 h to obtain a mixed emulsion; add the remaining monomer mixture and 0.2-0.8 g of emulsifier to 30-120 mL of ethyl acetate and stir for 30-90 min to obtain a monomer emulsion; A-4-4. Under stirring, the mixed emulsion is added to the composite filler dispersion and stirred at 60-72℃ for 0.5-3h. The monomer emulsion is added dropwise under stirring and maintained at the temperature, and the addition is completed in 1-3h. Then the temperature is raised to 85-95℃ and stirred for 2-8h. The temperature is lowered to 30-50℃, filtered, and the solid product is washed with ethyl acetate and ethanol in sequence and dried under vacuum to obtain the composite ceramic reinforced filler.

6. The ceramic composite insulating film according to claim 5, characterized in that, The sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Preparation of hydroxylated plate-like hexagonal boron nitride: B-1-1. Take hexagonal boron nitride, ethanol, deionized water and polyacrylamide, mix them and add them to a ball mill, ball mill, centrifuge the product, wash the solid and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Add the flake-shaped hexagonal boron nitride to NaOH aqueous solution, disperse it by ultrasonication, place the resulting mixture in a reaction vessel, react under heating, filter after the reaction is completed, wash, dry and grind the solid product to obtain hydroxylated flake-shaped hexagonal boron nitride. B-2. Using the same method as in step A-4, graft epoxy resin-modified acrylate copolymer onto hydroxylated plate-like hexagonal boron nitride to obtain plate-like ceramic reinforcing filler.

7. The ceramic composite insulating film according to claim 6, characterized in that, The sheet-like ceramic reinforcing filler is prepared by the following steps: B-1. Preparation of hydroxylated plate-like hexagonal boron nitride: B-1-1. Take 5-20g of hexagonal boron nitride, 125-500mL of ethanol, 50-200mL of deionized water and 0.1-0.4g of polyacrylamide and mix them in a ball mill. Control the ball-to-material ratio to be (5-15):

1. Ball mill for 6-14h. Centrifuge the product, wash the solid with ethanol and freeze dry to obtain flake hexagonal boron nitride. B-1-2. Take 2.5-10g of plate-shaped hexagonal boron nitride and add it to 150-600mL of NaOH aqueous solution with a concentration of 2-8mol / L. After ultrasonic dispersion for 0.5-2h, place the resulting mixture in a reaction vessel and react at 150-190℃ for 2-8h. Filter the mixture, wash the solid product with deionized water until neutral, dry it under vacuum, and grind it to obtain hydroxylated plate-shaped hexagonal boron nitride. B-2. Using the same method as in step A-4, graft epoxy resin-modified acrylate copolymer onto hydroxylated plate-like hexagonal boron nitride to obtain plate-like ceramic reinforcing filler.

8. The ceramic composite insulating film according to claim 5, characterized in that, The epoxy resin is epoxy resin E-51, the curing agent is dicyandiamide, the curing accelerator is 2-ethyl-4-methylimidazole, the toughening agent is toughening agent CMP-410, and the antioxidant is antioxidant 1010.

9. The ceramic composite insulating film according to claim 5, characterized in that, The polymerization inhibitor is hydroquinone, the initiator is a mixture of azobisisobutyronitrile and N,N-dimethylaniline in a mass ratio of 1:1, and the emulsifier is a mixture of emulsifier COPS-1 and SDS in a mass ratio of 1:

2.

10. A method for preparing a ceramic composite insulating film as described in any one of claims 1-9, characterized in that, The process includes the following steps: mixing epoxy resin, composite ceramic reinforcing filler, flake ceramic reinforcing filler, toughening agent, and antioxidant; stirring at 50-85℃ for 0.5-2 hours; cooling to room temperature; adding curing agent and curing accelerator; stirring for 10-45 minutes; uniformly coating the resulting mixture onto a substrate; curing at 75-100℃ for 2-10 hours; and then peeling off to obtain an insulating film.

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