Preparation method of epoxy insulating material based on filler surface modification

Abstract

The invention belongs to the technical field of epoxy insulating materials, and particularly relates to a preparation method of an epoxy insulating material based on filler surface modification. According to the epoxy insulating material based on filler surface modification, the hyperbranched molecule modified electrical filler is introduced into the epoxy resin and the curing component, and three-stage gradient curing is adopted in the curing process; the hyperbranched structure of hyperbranched molecules, fluorine and amido functional groups connected in the hyperbranched structure and the properties of imide rings are fully utilized, so that the processability such as viscosity and the electrical properties such as bulk resistivity and breakdown strength of the epoxy insulating material are improved in multiple aspects, and the high-performance epoxy insulating material is provided; therefore, the technical problem of low performance of the epoxy insulating material in the prior art is solved.

Description

Technical Field

[0001] This application belongs to the field of epoxy insulation materials technology, and particularly relates to a method for preparing epoxy insulation materials based on filler surface modification. Background Technology

[0002] Epoxy resin composites have become one of the core insulation materials for modern electrical equipment due to their excellent mechanical properties, electrical properties and processability. They are widely used in the manufacture of electrical equipment such as pot insulators, dry-type transformers, and GIS (gas-insulated switchgear). For example, they are used to prepare transformer winding insulation protection layers, insulator bodies and insulation components of GIS.

[0003] However, with the development of high-voltage, ultra-high-voltage, and even extra-high-voltage power transmission technologies, the performance requirements for epoxy insulation materials are constantly increasing, especially in terms of insulation strength, thermal stability, and processability, which present numerous challenges. Traditional methods typically involve introducing a high proportion of inorganic fillers into epoxy resin to improve insulation performance. Although the high dielectric strength and low dielectric loss of inorganic fillers can effectively optimize the dielectric properties of composite materials, this strategy suffers from the following technical bottlenecks: 1) Deterioration of processability: The high filler content introduces additional interfacial resistance between the inorganic filler and epoxy resin, in addition to the molecular chain movement resistance of the epoxy resin itself, resulting in a significant increase in system viscosity. The following are some of the main issues: 1) Reduced resin fluidity and impregnation efficiency during casting, which can easily induce internal bubbles and micro-defects; 2) Filler sedimentation and dispersion instability: Inorganic fillers undergo gravitational sedimentation in liquid resin due to density differences, leading to macroscopic phase separation. This not only degrades the mechanical strength of the material but also causes electric field distortion and induces partial discharge; 3) Organic-inorganic interface defects: Insufficient chemical bonding at the interface between the two phases forms a weak bonding region, which can easily become the starting point for charge accumulation and discharge channels under high field strength. It is evident that defects in the compatibility between inorganic fillers and epoxy resin can degrade the processing and electrical properties of epoxy insulation materials, making it necessary to improve the compatibility between inorganic fillers and epoxy insulation materials.

[0004] Alumina, an electrical filler, is one of the main inorganic fillers used in epoxy insulation materials. Electrical fillers are a type of inorganic filler with high purity and controllable morphology and particle size. Electrical fillers sold on the market are divided into ordinary electrical fillers and surface-modified electrical fillers. However, surface-modified electrical fillers generally focus on optimizing a single performance and lack the ability to improve the performance of epoxy insulation materials in multiple ways, resulting in the current low performance of epoxy insulation materials. Summary of the Invention

[0005] In view of this, this application provides a method for preparing epoxy insulation materials based on filler surface modification, which is used to solve the technical problem of low performance of epoxy insulation materials in the prior art.

[0006] The first aspect of this application provides an epoxy insulating material based on filler surface modification, the raw materials including epoxy resin, curing components and hyperbranched molecularly modified electrical fillers;

[0007] The branching unit of the hyperbranched molecule contains an imide ring (-CO-NR-CO-).

[0008] The branching units of the hyperbranched molecule are connected to fluorine-containing groups and amino-terminal functional groups.

[0009] Preferably, the epoxy resin is selected from at least one of bisphenol epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin.

[0010] Preferably, the bisphenol epoxy resin is selected from at least one of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and bisphenol type epoxy resin.

[0011] Preferably, the curing component includes an anhydride curing agent and an imidazole accelerator.

[0012] Preferably, the electrical filler is an inorganic electrical filler, selected from at least one of aluminum nitride, boron nitride, magnesium oxide, zinc oxide, titanium oxide, aluminum nitride, and mica.

[0013] Preferably, the electrical filler is an electrical filler surface-modified with an epoxy silane coupling agent.

[0014] Preferably, the epoxy silane coupling agent is selected from at least one of γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560), γ-(2,3-epoxypropoxypropyl)trimethoxysilane (A-187), and β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane (KBM-303).

[0015] Preferably, the epoxy insulating material based on filler surface modification comprises, by weight, 100 parts by weight of epoxy resin, 30-100 parts by weight of curing component, and 5-100 parts by weight of hyperbranched molecularly modified electrical filler.

[0016] The second aspect of this application provides a method for preparing an epoxy insulating material based on filler surface modification, which can prepare the epoxy insulating material based on filler surface modification described in the first aspect, comprising the following steps:

[0017] Preparation steps of branched monomers: A benzene ring derivative containing halogen, nitro and trifluoromethyl substituents is subjected to nucleophilic substitution and nitro reduction sequentially with phloroglucinol or a benzene ring derivative containing amino, nitro and trifluoromethyl substituents to obtain a branched monomer.

[0018] Preparation steps of hyperbranched molecules: The branched monomer and the dianhydride monomer are subjected to an imide ring condensation reaction to obtain hyperbranched molecules, wherein the molar ratio of the branched monomer to the dianhydride is 1~5:1;

[0019] Preparation steps of epoxy silane modified electrical filler: Silane coupling agent and electrical filler are subjected to silane hydrolysis and condensation reaction to obtain epoxy silane modified electrical filler;

[0020] Preparation steps of hyperbranched molecular modified alumina electrical filler: hyperbranched molecules and epoxy silane modified electrical filler are subjected to nucleophilic epoxy ring-opening reaction to obtain hyperbranched molecular modified electrical filler;

[0021] Curing steps for epoxy insulation materials based on filler surface modification: After mixing epoxy resin, curing components and hyperbranched molecularly modified electrical fillers, the mixture is degassed and cured to obtain epoxy insulation materials based on filler surface modification.

[0022] Preferably, in the preparation step of the branched monomer, the benzene ring derivative containing halogen, nitro and trifluoromethyl substituents is selected from at least one of 2-chloro-4-nitro-5-trifluoromethylbenzene, 2-trifluoromethyl-4-chloronitrobenzene, 2-bromo-4-nitro-5-trifluoromethylbenzene, and 2-iodo-4-nitro-5-trifluoromethylbenzene; the benzene ring derivative containing amino, nitro and trifluoromethyl substituents is selected from 3-trifluoromethyl-4-nitroaniline.

[0023] Preferably, in the preparation step of the branched monomer, the acid-binding agent used for nucleophilic substitution is potassium carbonate, and the solvent is N,N-dimethylformamide; the reducing agent used for nitro reduction is iron, and the activity promoter is hydrochloric acid solution.

[0024] Preferably, in the preparation step of the hyperbranched molecule, the dianhydride monomer used is selected from at least one of pyromellitic dianhydride (PMDA), ether dianhydride (OPDA), and biphenyl dianhydride (s-BPDA).

[0025] Preferably, in the preparation step of the hyperbranched molecule, the catalyst used for the polycondensation reaction of the imide ring is at least one of pyridine, triethylamine, N-methylimidazolium, and quinoline; the dehydrating agent is at least one of acetic anhydride, propionic anhydride, and benzoic anhydride; and the solvent is selected from dimethylacetamide (DMAC).

[0026] Preferably, in the preparation step of epoxy silane modified electrical filler, the catalyst used for the silane hydrolysis condensation reaction is at least one of hydrochloric acid solution, nitric acid solution, and ammonia water.

[0027] Preferably, in the preparation step of epoxy silane modified electrical filler, the mass ratio of epoxy silane coupling agent to electrical filler is 0.2~1:100; in the preparation step of hyperbranched molecule modified electrical filler, the mass ratio of hyperbranched molecule to epoxy silane modified electrical filler is 2~10:100.

[0028] Preferably, in the curing step of the epoxy insulation material based on filler surface modification, the curing process includes: pre-curing at a low temperature of 60~90℃ for 1~2h, transition curing at a medium temperature of 100~120℃ for 2~4h, and deep curing at a high temperature of 140~150℃ for 6~18h.

[0029] The third aspect of this application provides the application of the epoxy insulating material based on filler surface modification described in the first aspect in the preparation of electrical equipment.

[0030] Compared with the prior art, the method for preparing epoxy insulation material based on filler surface modification provided in this application has at least the following beneficial effects:

[0031] 1. This application provides a method for preparing epoxy insulating materials based on filler surface modification, which introduces hyperbranched molecular modified electrical fillers into epoxy resin and curing components; the hyperbranched structure of the hyperbranched molecules, the fluorine and amine functional groups connected in the hyperbranched structure, and the properties of the imide ring itself improve the processing performance such as viscosity, the electrical properties such as volume resistivity and breakdown strength of epoxy insulating materials in many ways.

[0032] 2. The epoxy insulation material preparation method based on filler surface modification provided in this application adopts a three-stage gradient curing process, which makes full use of the activity differences of different functional groups such as amine and epoxy, and sequentially performs low-temperature pre-curing, medium-temperature transition curing and high-temperature deep curing. This can eliminate defects at the interface between electrical filler and epoxy body, form a dense cross-linked network, and improve the electrical properties such as bulk resistivity and breakdown strength of the epoxy insulation material based on filler surface modification. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 A schematic diagram of the reaction process of branched monomer A3 in the method for preparing epoxy insulating material based on filler surface modification provided in Example 1 of this application;

[0035] Figure 2This is a schematic diagram of the reaction process of branched monomer A3 in the method for preparing epoxy insulating material based on filler surface modification provided in Example 4 of this application. Detailed Implementation

[0036] This application provides a method for preparing epoxy insulation materials based on filler surface modification, which solves the technical problem of low performance of epoxy insulation materials in the prior art.

[0037] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Improving the compatibility between inorganic fillers and epoxy resins by introducing surface functional groups on the surface of inorganic fillers is an effective solution to enhance the performance of epoxy insulation materials. For example, some pre-surface modified electrical filler alumina currently on the market. However, current electrical filler alumina generally focuses on optimizing a single property and lacks a multi-faceted approach to improving the performance of epoxy insulation materials, resulting in relatively low performance of current epoxy insulation materials. In view of the shortcomings of the current low performance of epoxy insulation materials, this application provides an epoxy insulation material based on filler surface modification. Taking electrical filler alumina as an example, the raw materials of the epoxy insulation material based on filler surface modification include epoxy resin, curing components, and hyperbranched molecularly modified electrical filler alumina. The branching units of the hyperbranched molecules contain imide rings (-CO-NR-CO-) and are connected to fluorine-containing groups and amino terminal functional groups.

[0039] The epoxy insulation material based on filler surface modification provided in this application introduces hyperbranched molecularly modified alumina electrical filler into the basic raw materials such as epoxy resin and curing components. Specifically, hyperbranched molecular modification is introduced onto the surface of the alumina electrical filler. As those skilled in the art know, the structure of a hyperbranched molecule includes a "central core unit," "branching units," and "terminal functional groups." The central core unit generally has multiple reaction sites, such as hydroxyl and amino groups, while the branching units form the backbone of the hyperbranched polymer. These branching units continuously connect and extend through reactions, forming more branches and thus hyperbranching. For example, in this application, the branching units are initially connected / extended through a nucleophilic substitution reaction, and the branches contain fluorine-containing groups at their ends. Then, nucleophilic substitution is performed... The reduction of nitro groups at the ends of the branching units in the reaction results in the presence of amine groups at the ends of the branching units. This leads to the condensation reaction of some of the amine groups at the ends of the branching units with the dianhydride, further connecting / extending the branching units containing the amine ring (-CO-NR-CO-). This yields hyperbranched molecules with fluorinated groups and amine terminal functional groups. When the surface-modified electrical filler alumina of the hyperbranched molecules is added to epoxy resin, the molecular chain entanglement effect of the hyperbranched three-dimensional topology of the hyperbranched molecules significantly reduces the viscosity of the system. Simultaneously, the strong polar matching effect of fluorine elements in the fluorinated groups connected to the branching units achieves optimal interaction between the filler and the epoxy resin. The molecular-level wetting process forms a defect-free chemically bonded interface, reducing interfacial damping and thus lowering the viscosity of the epoxy insulation system, improving processing performance, reducing internal bubbles and micro-defects, and enhancing the performance of the epoxy insulation material. On the other hand, the high electronegativity of fluorine atoms in the fluorine-containing groups connected by branched units constructs deep trap energy levels at the interface, inducing electron localization effects, reducing space charge density, increasing breakdown field strength, and simultaneously blocking surface discharge channels, thereby improving the electrical properties of the epoxy insulation material. Furthermore, based on the difference in reactivity between the amine groups and acid anhydrides connected by branched units, a three-stage gradient curing process is achieved, preferentially triggering low-temperature pre-curing of the amine-epoxy crosslinking, forming a dense pre-crosslinked layer on the filler surface. The network achieves space locking of the filler, eliminates defects at the interface between the electrical filler and the epoxy matrix, and then activates the medium-temperature transition curing of the resin bulk crosslinking to construct an interface-matrix transition network, releases internal stress and optimizes dispersion homogeneity. Next, the high-temperature deep curing of the fluorinated crosslinking network is completed to form a three-dimensional interpenetrating structure between the filler and the matrix, achieving synergistic enhancement of the mechanical and electrical properties of the interface, and improving the performance of epoxy insulation materials in conjunction with the imide ring itself. Thus, the hyperbranched molecularly modified electrical filler alumina provided in this application can improve the performance of epoxy insulation materials in many ways through the hyperbranched structure, the fluorine and amine functional groups connected in the hyperbranched structure, and the properties of the imide ring itself, overcoming the defect of low performance of epoxy insulation materials.

[0040] Accordingly, this application also provides the above-mentioned method for preparing epoxy insulating materials based on filler surface modification, the preparation method including the steps of preparing branched monomers, preparing hyperbranched molecules, modifying electrical filler alumina, and curing.

[0041] In the preparation of branched monomers, benzene ring derivatives containing halogens, nitro groups, and trifluoromethyl substituents, such as 2-chloro-4-nitro-5-trifluoromethylbenzene and 2-trifluoromethyl-4-chloronitrobenzene, were nucleophilically substituted with benzene ring derivatives containing amino groups, nitro groups, and trifluoromethyl substituents, such as 3-trifluoromethyl-4-nitroaniline, or phloroglucinol, followed by nitro reduction to obtain branched monomers. The raw materials used in the preparation of branched monomers are shown in Table 1, and the reaction process is as follows: Figure 1-2 As shown, the branched monomer is named A3 monomer, and its chemical structure is shown in Formula I, Formula II, and Formula III.

[0042] Table 1: Raw materials for branched monomers

[0043]

[0044]

[0045] The preparation of hyperbranched molecules involves the polycondensation reaction of a branched monomer A3 containing an amino group with the imide ring of a dianhydride monomer. This process links / extends the terminal amino groups of some branched monomers into branched units containing an imide ring (-CO-NR-CO-). The dianhydride monomer is named B2 monomer, as shown in Table 2. The structures of the hyperbranched molecules obtained by the polycondensation reaction of branched monomer A3 (Formulas I, II, and III) and the dianhydride monomer with the imide ring are shown in Formulas IV, V, and VI. In the polycondensation reaction of the polyimide ring, since the raw materials of the branched monomer are already limited, the process involves... After the substitution reaction, the branched monomer contains more than 3 amino groups. Therefore, when the molar ratio of branched monomer A3 to dianhydride monomer B2 is 1:1, and the molar ratio of amino groups in branched monomer A3 to anhydride in dianhydride monomer B2 is 1:1, there will be excess amino groups remaining, which will participate in the subsequent reaction with epoxy groups. In this application, the molar ratio of branched monomer A3 to dianhydride monomer B2 is limited to 1 to 5:1. For example, the molar ratio of branched monomer A3 to dianhydride monomer B2 can be 1.1:1, 1.3:1, 1.5:1, 2:1, 3:1, 4:1, or 5:1.

[0046] Table 2: Dihydride Monomer B2

[0047]

[0048] Formula IV, Formula V, Formula VI;

[0049] In equations IV, V, and VI, R 1 R 2 and R 3 Selected from branched units containing an imide ring (-CO-NR-CO-) or an amino group (NH2), R 1 R 2 and R 3 It includes at least one branched unit containing an imide ring (-CO-NR-CO-) and an amino group (NH2).

[0050] In the steps of modifying electrical filler alumina and curing, this application first uses an epoxy silane coupling agent such as KH-560 to perform silane hydrolysis and condensation with the hydroxyl groups on the surface of the electrical filler alumina to obtain epoxy silane-modified electrical filler alumina. Then, the amino terminal functional groups of the hyperbranched molecules are used to carry out a nucleophilic epoxy ring-opening reaction to incorporate the hyperbranched molecules and electrical filler alumina into the crosslinking network of the epoxy insulation material, thereby improving the performance of the epoxy insulation material.

[0051] The following will provide a detailed description of the preparation method of epoxy insulation material based on filler surface modification provided in this application, in conjunction with embodiments and experimental examples.

[0052] Example 1

[0053] This embodiment provides a method for preparing epoxy insulating materials based on filler surface modification. The preparation method includes a branched monomer preparation step, a hyperbranched molecule preparation step, an epoxy silane modified electrical filler alumina preparation step, a hyperbranched molecule modified electrical filler alumina preparation step, and a curing step for the epoxy insulating material based on filler surface modification.

[0054] The reaction process of branched monomer A3 is as follows: Figure 1 As shown, the preparation steps include: first, adding 0.2 mol of 3-trifluoromethyl-4-nitroaniline, 0.4 mol of 2-chloro-4-nitro-5-trifluoromethylbenzene, 0.25 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, and carrying out a nucleophilic substitution reaction at 90°C for 6 h, followed by purification by silica gel column chromatography, and drying the eluent to obtain a branched intermediate product; then adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, and carrying out a nitro reduction reaction at 90°C for 6 h, followed by filtration of the reaction solution, purification by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0055] The preparation steps of the hyperbranched molecule include: adding 0.05 moles of branching monomer A3, 0.03 moles of ether dianhydride (OPDA) as B2 monomer, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0056] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours under constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0057] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 5:100, stirring at 300 rad / s for 8 h at 50 °C to obtain hyperbranched molecular modified electrical filler alumina.

[0058] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at a low temperature of 60℃ for 1 hour, a medium temperature transition curing at 100℃ for 2 hours, and a high temperature deep curing at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0059] Example 2

[0060] This embodiment provides a method for preparing epoxy insulating materials based on filler surface modification. The preparation method includes the preparation steps of branched monomers, hyperbranched molecules, epoxy silane-modified electrical filler alumina, hyperbranched molecule-modified electrical filler alumina, and curing steps of epoxy insulating materials based on filler surface modification. The difference between the preparation method and Example 1 is the amount of branched monomers A3 and B2.

[0061] The preparation steps of the branched monomer include: first, adding 0.2 mol of 3-trifluoromethyl-4-nitroaniline, 0.4 mol of 2-chloro-4-nitro-5-trifluoromethylbenzene, 0.25 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, carrying out a nucleophilic substitution reaction at 90°C for 6 h, purifying by silica gel column chromatography, and drying the eluent to obtain the branched intermediate product; then adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, carrying out a nitro reduction reaction at 90°C for 6 h, filtering the reaction solution, purifying by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0062] The preparation steps of the hyperbranched molecule include: adding 0.05 moles of branching monomer A3, 0.025 moles of ether dianhydride (OPDA) as B2 monomer, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0063] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours under constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0064] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 5:100, and stirring at 300 rad / s for 8 h at 50 °C to obtain hyperbranched molecular modified electrical filler alumina.

[0065] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at a low temperature of 60℃ for 1 hour, a medium temperature transition curing at 100℃ for 2 hours, and a high temperature deep curing at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0066] Example 3

[0067] This embodiment provides a method for preparing epoxy insulating materials based on filler surface modification. The preparation method includes the preparation steps of branched monomers, hyperbranched molecules, epoxy silane-modified electrical filler alumina, hyperbranched molecule-modified electrical filler alumina, and curing steps of epoxy insulating materials based on filler surface modification. The difference between the preparation method and Example 1 lies in the type of B2 monomer.

[0068] The preparation steps of the branched monomer include: first, adding 0.2 mol of 3-trifluoromethyl-4-nitroaniline, 0.4 mol of 2-chloro-4-nitro-5-trifluoromethylbenzene, 0.25 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, carrying out a nucleophilic substitution reaction at 90°C for 6 h, purifying by silica gel column chromatography, and drying the eluent to obtain the branched intermediate product; then adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, carrying out a nitro reduction reaction at 90°C for 6 h, filtering the reaction solution, purifying by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0069] The preparation steps of the hyperbranched molecule include: adding 0.05 moles of branching monomer A3, 0.03 moles of pyromellitic anhydride (PMDA) as monomer B2, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0070] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours under constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0071] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 5:100, and stirring at 300 rad / s for 8 h at 50 °C to obtain hyperbranched molecular modified electrical filler alumina.

[0072] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at a low temperature of 60℃ for 1 hour, a medium temperature transition curing at 100℃ for 2 hours, and a high temperature deep curing at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0073] Example 4

[0074] This embodiment provides an epoxy insulating material based on filler surface modification. The preparation method includes the preparation steps of branched monomers, hyperbranched molecules, epoxy silane-modified electrical filler alumina, hyperbranched molecule-modified electrical filler alumina, and curing steps of the epoxy insulating material based on filler surface modification. The difference between the preparation method and that of Example 1 lies in the type of branched monomer A3.

[0075] The reaction process of branched monomer A3 is as follows: Figure 2 As shown, the preparation steps include: first, adding 0.2 mol of phloroglucinol, 0.6 mol of 2-trifluoromethyl-4-chloronitrobenzene, 0.35 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, and carrying out a nucleophilic substitution reaction at 90°C for 6 h, followed by purification by silica gel column chromatography, and drying the eluent to obtain a branched intermediate product; then, adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, and carrying out a nitro reduction reaction at 90°C for 6 h, followed by filtration of the reaction solution, purification by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0076] The preparation steps of the hyperbranched molecule include: adding 0.05 moles of branching monomer A3, 0.03 moles of ether dianhydride (OPDA) as B2 monomer, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0077] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours under constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0078] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 5:100, and stirring at 300 rad / s for 8 h at 50 °C to obtain hyperbranched molecular modified electrical filler alumina.

[0079] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at a low temperature of 60℃ for 1 hour, a medium temperature transition curing at 100℃ for 2 hours, and a high temperature deep curing at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0080] Example 5

[0081] This embodiment provides an epoxy insulating material based on filler surface modification. The preparation method includes the steps of preparing branched monomers, preparing hyperbranched molecules, preparing epoxy silane-modified electrical filler alumina, preparing hyperbranched molecule-modified electrical filler alumina, and curing the epoxy insulating material based on filler surface modification.

[0082] The preparation steps of branched monomer A3 include: first, adding 0.2 mol of phloroglucinol, 0.6 mol of 2-trifluoromethyl-4-chloronitrobenzene, 0.35 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, carrying out a nucleophilic substitution reaction at 90°C for 6 h, purifying by silica gel column chromatography, and drying the eluent to obtain the branched intermediate product; then, adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, carrying out a nitro reduction reaction at 90°C for 6 h, filtering the reaction solution, purifying by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0083] The preparation steps of the hyperbranched molecule include: adding 0.06 moles of branching monomer A3, 0.02 moles of biphenyltetracarboxylic dianhydride (s-BPDA) as B2 monomer, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0084] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:1 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid to adjust the pH of the system to 3-5; stirring the reaction at 400 rad / s for 9 hours under constant temperature of 70℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0085] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 10:100, and stirring at 60℃ and 400 rad / s for 98 h to obtain hyperbranched molecular modified electrical filler alumina.

[0086] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, imidazole accelerator, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:50:0.6:50, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at 70℃ for 1 hour, at 110℃ for 2 hours, and at 150℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0087] Example 6

[0088] This embodiment provides an epoxy insulating material based on filler surface modification. The preparation method includes the preparation steps of branched monomers, hyperbranched molecules, epoxy silane-modified boron nitride electrical filler, hyperbranched molecule-modified boron nitride electrical filler, and curing steps of the epoxy insulating material based on filler surface modification. The difference between the preparation method and that of Example 4 lies in the type of B2 monomer.

[0089] The preparation steps of branched monomer A3 include: first, adding 0.2 mol of phloroglucinol, 0.6 mol of 2-trifluoromethyl-4-chloronitrobenzene, 0.35 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, carrying out a nucleophilic substitution reaction at 90°C for 6 h, purifying by silica gel column chromatography, and drying the eluent to obtain the branched intermediate product; then, adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, carrying out a nitro reduction reaction at 90°C for 6 h, filtering the reaction solution, purifying by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0090] The preparation steps of the hyperbranched molecule include: adding 0.08 moles of branching monomer A3, 0.02 moles of pyromellitic anhydride (PMDA) as monomer B2, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0091] The preparation steps of epoxy silane-modified boron nitride electrical filler include: dispersing boron nitride electrical filler and silane coupling agent KH560 in a 100:2 mass ratio in a mixed solvent of ethanol / deionized water, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 200 rad / s for 10 hours under constant temperature of 80℃, and centrifuging and drying to obtain epoxy silane-modified boron nitride electrical filler.

[0092] The preparation steps of hyperbranched molecular modified electrical filler boron nitride include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler boron nitride in N-methylpyrrolidone (NMP) at a mass ratio of 20:100, and stirring at 70°C at a speed of 200 rad / s for 10 h to obtain hyperbranched molecular modified electrical filler boron nitride.

[0093] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methylhexahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler boron nitride are thoroughly mixed under constant temperature conditions in a mass ratio of 100:70:0.8:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at 80℃ for 2 hours, at 120℃ for 3 hours, and at 150℃ for 11 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0094] Example 7

[0095] This embodiment provides a method for preparing epoxy insulation material based on filler surface modification. As a first comparative embodiment, the preparation method includes a curing step of epoxy insulation material based on filler surface modification.

[0096] The curing steps of the epoxy insulation material based on filler surface modification include: bisphenol A type epoxy resin, curing components methyltetrahydrophthalic anhydride and N,N-dimethylbenzylamine, and electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at a low temperature of 60℃ for 1 hour, a medium temperature transition curing at 100℃ for 2 hours, and a high temperature deep curing at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the epoxy insulation material based on filler surface modification.

[0097] Example 8

[0098] This embodiment provides a method for preparing epoxy insulating materials based on filler surface modification. As a second comparative embodiment, the preparation method includes the preparation steps of epoxy silane modified electrical filler alumina and the curing steps of epoxy insulating materials based on filler surface modification.

[0099] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours at a constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina;

[0100] The curing steps of the filler-surface modified epoxy insulation material include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and epoxysilane modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and pre-cured sequentially at 60℃ for 1 hour, at 100℃ for 2 hours, and at 140℃ for 10 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the filler-surface modified epoxy insulation material.

[0101] Example 9

[0102] This embodiment provides a method for preparing epoxy insulating materials based on filler surface modification. As a third comparative embodiment, the preparation method includes the steps of preparing branched monomers, preparing hyperbranched molecules, preparing epoxy silane-modified electrical filler alumina, preparing hyperbranched molecule-modified electrical filler alumina, and curing the epoxy insulating material based on filler surface modification.

[0103] The preparation steps of branched monomer A3 include: first, adding 0.2 mol of 3-trifluoromethyl-4-nitroaniline, 0.4 mol of 2-chloro-4-nitro-5-trifluoromethylbenzene, 0.25 mol of potassium carbonate, and an appropriate amount of N,N-dimethylformamide solution to a reaction vessel, carrying out a nucleophilic substitution reaction at 90°C for 6 h, purifying by silica gel column chromatography, and drying the eluent to obtain the branched intermediate product; then, adding 0.1 mol of the branched intermediate product, 0.6 mol of iron powder, and an appropriate amount of hydrochloric acid solution to a reaction vessel, carrying out a nitro reduction reaction at 90°C for 6 h, filtering the reaction solution, purifying by silica gel column chromatography, and drying the eluent to obtain the branched monomer A3.

[0104] The preparation steps of the hyperbranched molecule include: adding 0.05 moles of branching monomer A3, 0.03 moles of ether dianhydride (OPDA) as B2 monomer, and appropriate amounts of acetic anhydride dehydrating agent and pyridine catalyst into a reactor and stirring at 300 rad / s for 8 h at 40 °C; after the polycondensation reaction of the imide ring is completed, the mixture is poured into a large amount of methanol to precipitate, the precipitate is collected and washed and vacuum dried multiple times to finally obtain a hyperbranched molecule in which the branching unit includes an imide ring and the branching unit is connected to a fluorine-containing group and an amino terminal functional group.

[0105] The preparation steps of epoxy silane modified electrical filler alumina include: dispersing electrical filler alumina and silane coupling agent KH560 in a 100:0.5 mass ratio in an ethanol / deionized water mixed solvent, transferring to a reaction vessel, and adding dilute hydrochloric acid dropwise to adjust the pH of the system to 3-5; stirring the reaction at 300 rad / s for 8 hours under constant temperature of 60℃, and centrifuging and drying to obtain epoxy silane modified electrical filler alumina.

[0106] The preparation steps of hyperbranched molecular modified electrical filler alumina include: dispersing fluorine-containing hyperbranched molecules and epoxy silane modified electrical filler alumina in acetone at a mass ratio of 5:100, and stirring at 300 rad / s for 8 h at 50 °C to obtain hyperbranched molecular modified electrical filler alumina.

[0107] The curing steps of the epoxy insulation material based on filler surface modification include: bisphenol A type epoxy resin, curing component methyltetrahydrophthalic anhydride, N,N-dimethylbenzylamine, and hyperbranched molecularly modified electrical filler alumina are thoroughly mixed under constant temperature conditions in a mass ratio of 100:39:0.5:70, followed by vacuum degassing to obtain a mixture; the mixture is poured into a mold and cured at 140℃ for 13 hours; after curing, it is naturally cooled to room temperature and then demolded to obtain the epoxy insulation material based on filler surface modification.

[0108] Experimental Example 1

[0109] This experiment uses the epoxy insulation materials based on filler surface modification provided in Examples 1-9 as test samples for performance testing. The performance tests include viscosity testing before curing and electrical performance testing after curing. The viscosity test was conducted according to the national standard GB / T10247-2008, with a test temperature of 120℃ and a rotation method. The volume resistivity test was conducted according to the national standard GB / T1410-2006, with a test voltage of 100V. The breakdown voltage test was conducted according to the national standard GB / T1408.1-2016, with a voltage ramp rate of 1kV / s and uniform voltage ramp. The test results are shown in Table 3.

[0110] Table 3: Viscosity and Electrical Properties Test Results

[0111]

[0112] As shown in Table 3, the epoxy insulation material based on filler surface modification provided in Example 7, due to the direct addition of unmodified ordinary electrical filler alumina to the epoxy resin, has poor interfacial compatibility and a large amount of added alumina. This results in strong interfacial resistance between alumina and epoxy resin, in addition to the molecular chain movement resistance of the epoxy resin itself. Consequently, the epoxy insulation material based on filler surface modification has high viscosity, poor flowability and impregnation efficiency, is prone to inducing internal bubbles and micro-defects, has poor processing performance, and is difficult to cast into molds to prepare large epoxy insulation devices. In contrast, the epoxy insulation material based on filler surface modification provided in Example 8 uses silane coupling. Modified alumina electrical filler and silane coupling agent improve interfacial compatibility, resulting in improved viscosity of epoxy insulation materials based on filler surface modification, better processing performance, fewer defects, and better performance in large epoxy insulation devices. The epoxy insulation materials based on filler surface modification provided in Examples 1-6 further utilize hyperbranched molecular modification of alumina electrical filler. Hyperbranched molecules improve the viscosity of epoxy insulation materials based on filler surface modification through various effects such as hyperbranched structure, fluorine and amine functional groups connected in the hyperbranched structure, and the properties of the imide ring itself. This also improves the volume resistivity and breakdown strength of the epoxy insulation materials based on filler surface modification.

[0113] As can also be seen from Table 3, compared with Examples 1-6, the epoxy insulation material based on filler surface modification provided in Example 7 also used hyperbranched molecularly modified electrical filler alumina, but because the curing conditions were not three-stage gradient curing, the amine groups in the hyperbranched molecules were not utilized to crosslink with the epoxy and form a dense pre-crosslinked network on the filler surface through low-temperature pre-curing. This caused the volume resistivity and breakdown strength of the epoxy insulation material based on filler surface modification to decrease slightly, but it was still higher than the epoxy insulation material based on filler surface modification provided in Examples 7-8.

[0114] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. An epoxy insulating material based on filler surface modification, characterized in that, This includes epoxy resin, curing components, and hyperbranched molecularly modified electrical fillers; The branching unit of the hyperbranched molecule contains an imide ring; The branching units of the hyperbranched molecule are connected to fluorine-containing groups and amino-terminal functional groups.

2. The epoxy insulation material based on filler surface modification according to claim 1, characterized in that, The electrical filler is selected from at least one of aluminum nitride, boron nitride, magnesium oxide, zinc oxide, titanium oxide, aluminum nitride, and mica.

3. The epoxy insulation material based on filler surface modification according to claim 2, characterized in that, The electrical filler is an electrical filler modified with epoxy silane coupling agent.

4. The epoxy insulation material based on filler surface modification according to claim 1, characterized in that, The epoxy resin is selected from at least one of bisphenol epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin.

5. An epoxy insulating material based on filler surface modification according to claim 1, characterized in that, Based on parts by mass, the epoxy insulating material based on filler surface modification includes 100 parts by mass of epoxy resin, 30-100 parts by mass of curing component, and 5-100 parts by mass of hyperbranched molecularly modified electrical filler.

6. A method for preparing epoxy insulating material based on filler surface modification, characterized in that, The preparation of an epoxy insulating material based on filler surface modification according to any one of claims 1-5 includes the following steps: Preparation steps of branched monomers: A benzene ring derivative containing halogen, nitro and trifluoromethyl substituents is subjected to nucleophilic substitution and nitro reduction sequentially with phloroglucinol or a benzene ring derivative containing amino, nitro and trifluoromethyl substituents to obtain a branched monomer. Preparation steps of hyperbranched molecules: The branched monomer and the dianhydride monomer are subjected to an imide ring condensation reaction to obtain hyperbranched molecules, wherein the molar ratio of the branched monomer to the dianhydride is 1~5:1; Preparation steps of epoxy silane modified electrical filler: Silane coupling agent and electrical filler are subjected to silane hydrolysis and condensation reaction to obtain epoxy silane modified electrical filler; Preparation steps of hyperbranched molecular modified alumina electrical filler: hyperbranched molecules and epoxy silane modified electrical filler are subjected to nucleophilic epoxy ring-opening reaction to obtain hyperbranched molecular modified electrical filler; Curing steps for epoxy insulation materials based on filler surface modification: After mixing epoxy resin, curing components and hyperbranched molecularly modified electrical fillers, the mixture is degassed and cured to obtain epoxy insulation materials based on filler surface modification.

7. The method for preparing epoxy insulating material based on filler surface modification according to claim 6, characterized in that, The curing process of epoxy insulation materials based on filler surface modification includes: pre-curing at low temperature of 60~90℃, transition curing at medium temperature of 100~120℃, and deep curing at high temperature of 140~150℃.

8. The method for preparing epoxy insulating material based on filler surface modification according to claim 6, characterized in that, In the preparation steps of epoxy silane-modified electrical fillers, the mass ratio of epoxy silane coupling agent to electrical filler is 0.2~1:100; in the preparation steps of hyperbranched molecule-modified electrical fillers, the mass ratio of hyperbranched molecule to epoxy silane-modified electrical filler is 2~10:

100.

9. A method for preparing epoxy insulating material based on filler surface modification according to claim 6, characterized in that, In the preparation step of the branched monomer, the benzene ring derivative containing halogen, nitro and trifluoromethyl substituents is selected from at least one of 2-chloro-4-nitro-5-trifluoromethylbenzene, 2-trifluoromethyl-4-chloronitrobenzene, 2-bromo-4-nitro-5-trifluoromethylbenzene, and 2-iodo-4-nitro-5-trifluoromethylbenzene; the benzene ring derivative containing amino, nitro and trifluoromethyl substituents is selected from 3-trifluoromethyl-4-nitroaniline.

10. The application of an epoxy insulating material based on filler surface modification as described in any one of claims 6-9 in the preparation of electrical equipment.

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