Aromatic amine epoxy resin curing agent and design method thereof, and insulating epoxy resin and preparation method thereof

Abstract

The invention discloses an aromatic amine epoxy resin curing agent, a design method thereof, insulating epoxy resin and a preparation method thereof, and belongs to the technical field of insulation. At least two benzene ring structures are designed, and the benzene ring structures are connected through functional bridge bonds; an amino functional group is arranged at each of two ends of the designed structure; the ortho-position of the designed amino functional group is not provided with a high-electron-withdrawing substituent group; the aromatic amine epoxy resin curing agent is obtained; and the functional bridge bond is arranged at a 1, 4 or 1, 3 substitution position of the benzene ring structure. Polyaromatic diamine is used as a curing agent component of the epoxy resin, and a rigid aromatic structure is introduced into an epoxy main chain to enhance the thermal stability of the epoxy main chain and increase the glass-transition temperature; functional bridge bonds are introduced between benzene rings to break the conjugated structure of the benzene rings, so that the electrical performance is improved. And the high-temperature-stability and high-resistance insulating epoxy resin for the high-voltage direct current can be prepared. And the electrical performance of a key insulating part in the direct-current GIS / GIL under the action of a high temperature gradient and a high electric field can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of insulation, and in particular relates to an aromatic amine epoxy resin curing agent and a design method thereof, and an insulating epoxy resin and a preparation method thereof. Background Art

[0002] With the large-scale development of offshore wind power and plateau hydropower, DC GIS / GIL has become the main equipment for large-scale clean energy delivery in the future because of its advantages such as small footprint, high reliability and low environmental impact. Under DC voltage, the electric field inside the material is resistive, which is different from the resistive distribution of the electric field inside the equipment under traditional DC voltage. This easily accumulates surface charges on the surface of the insulating material and induces surface flashover failures. Since the temperature of the guide rod is close to the glass transition temperature of the epoxy material, and the resistivity of the epoxy material decreases significantly with increasing temperature. A radial temperature gradient will be formed inside the insulator, and the maximum electric field position will move toward the grounded shell, resulting in a decrease in the effective insulation distance, further distortion of the electric field on the surface of the material, and a significant decrease in the surface flashover voltage.

[0003] At present, researchers mainly propose to use micron and nanoparticles to modify materials to increase the electrical properties of epoxy composites. However, due to the large specific surface area of ​​nanoparticles, they are prone to agglomeration problems and cannot be evenly dispersed inside the material. They still cannot meet the requirements of large-scale industrial applications. In addition, the glass transition temperature of commercial epoxy resin matrix materials used for electrical insulation is only about 120°C, which further limits the electrical performance of electrical epoxy materials under high temperature gradients and high electric field conditions. There is currently no effective solution to the problems in the related technology, and it is difficult to meet the design requirements of key insulating parts in DC GIS / GIL.

[0004] In view of the problems of nanoparticle agglomeration, uneven dispersion and low glass transition temperature of epoxy resin matrix materials in the modification process of epoxy composite materials, it is urgent to find a new high-voltage DC insulation epoxy resin with high thermal stability and high resistance and its preparation method to meet the design requirements of key insulating parts in DC GIS / GIL under high temperature gradient and high electric field conditions. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide an aromatic amine epoxy resin curing agent and a design method thereof and an insulating epoxy resin and a preparation method thereof, so as to solve the technical problem that the electrical performance of key insulating parts in DC GIS / GIL is poor under high temperature gradient and high electric field.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a design method of an aromatic amine epoxy resin curing agent, comprising: Designing at least two benzene ring structures, wherein the benzene ring structures are connected by a functional bridge bond; setting an amino functional group at both ends of the designed structure; not setting a high electron-withdrawing substituent group at the ortho position of the designed amino functional group; and obtaining an aromatic amine epoxy resin curing agent; The functional bridge bond is arranged at the 1,4 substitution position or the 1,3 substitution position of the benzene ring structure.

[0007] Preferably, the functional bridge is a strong electron-withdrawing group or a large steric hindrance group.

[0008] Further preferably, the strong electron withdrawing group is -C=O or -SO2.

[0009] Further preferably, the bulky steric hindering group is -C2H6, -C2F6 or -C6H 12 .

[0010] The invention also discloses an aromatic amine epoxy resin curing agent, which is obtained by adopting the design method.

[0011] The present invention also discloses a method for preparing an insulating epoxy resin, which is prepared by using the aromatic amine epoxy resin curing agent obtained by the above-mentioned design method, and comprises the following steps: 1) dissolving the aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, heating and stirring for the first time until it is completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution; 2) adding the aromatic amine epoxy resin curing agent solution obtained in step 1) to the preheated epoxy resin monomer, and heating and stirring for a second time under continuous vacuum; then adding filler, heating and stirring for a third time, and performing a first degassing treatment to obtain a casting material; 3) The casting material obtained in step 2) is poured into a preheated mold, and a second degassing treatment is performed. After curing, the casting material is naturally cooled to room temperature, and demolded to obtain an insulating epoxy resin.

[0012] Preferably, in step 1), the usage ratio of aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15) g: (2-8) mL: (10-15) mL; The heating temperature of the first heating and stirring is 50~80℃, and the stirring time is 20~40min.

[0013] Preferably, the weight ratio of aromatic amine epoxy resin curing agent: epoxy resin monomer: filler is (5-30): (10-40): (30-60); The preheating temperature of epoxy resin monomer is 50~80℃, and the preheating time is 4~8h; The heating temperature of the second heating and stirring is 60~120℃, and the stirring time is 10~60min; The heating temperature of the third heating and stirring is 60-120°C, and the stirring time is 10-30min; The conditions for the first degassing treatment are: 60-120℃ temperature and pressure for 30-120min at a vacuum degree of 1-10mbar; Preferably, in step 3), the mold is sprayed with a release agent in advance and heated to 100° C.; The conditions for the second degassing treatment are: keeping the temperature and pressure at 60-120℃ for 30-60min under a vacuum degree of 1-10mbar; The curing conditions are: heating to 120~140°C, keeping warm for 60~180min; then heating to 150~180°C after 60~120min, keeping warm for 120~300min; then heating to 190~210°C after 60~120min, keeping warm for 60~180min.

[0014] The invention also discloses an insulating epoxy resin which is prepared by adopting the preparation method.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a design method of an aromatic amine epoxy resin curing agent, comprising: designing at least two benzene ring structures, introducing a rigid aromatic structure into an epoxy main chain to enhance its thermal stability and increase the glass transition temperature; enabling it to maintain performance unchanged at a higher temperature, thereby broadening the application range of epoxy resin; introducing a functional bridge bond between benzene rings as a means of breaking the conjugated structure of the benzene rings, effectively improving the electrical properties of the epoxy resin, especially the introduction of a strong electron-withdrawing group and a large steric hindrance group, respectively by constructing an electron trap and hindering the π-π stacking effect between benzene rings, blocking the charge transfer within and between epoxy molecular chains, and significantly improving the resistance performance. An amino functional group is respectively arranged at both ends of the designed structure; the amino functional group is used as a site for cross-linking reaction with the epoxy functional group in the epoxy resin monomer, and an amino functional group is respectively arranged at both ends, which can ensure that the curing agent and the epoxy resin fully react to form a uniform cross-linked network. Because high electron-withdrawing groups will greatly reduce the reaction activity, high electron-withdrawing substitution groups are not set at the ortho position of the designed amino functional group to ensure high amine reactivity during the cross-linking reaction and to ensure that the material is completely cured when the large insulating part is cured. The functional bridge bond is set at the 1,4 substitution position or the 1,3 substitution position of the benzene ring structure; the 1,2 substitution position may cause the reaction activity to be too low, and the subsequent curing reaction is more difficult. Reasonable substitution positions ensure that the main chain has a certain degree of freedom and can perform axial rotation. The design method of the aromatic amine epoxy resin curing agent disclosed in the present invention starts from the molecular structure design, systematically considers the needs of improving thermal stability and electrical properties, and provides scientific guidance for the development of high-performance epoxy resin curing agents. By adjusting the benzene ring structure, the type of functional bridge bond and the substitution position, the performance of the curing agent can be flexibly adjusted to adapt it to different application requirements. It can be used to prepare epoxy resins for high-voltage DC insulation with high thermal stability and high resistance. It helps to solve the electrical performance of key insulating parts in DC GIS / GIL under high temperature gradients and high electric fields.

[0016] Furthermore, the introduced functional bridge bonds are divided into two categories. The first category is strong electron-withdrawing groups, which construct electron traps between benzene ring structures to block charge transfer within the epoxy molecular chain. Strong electron-withdrawing groups can effectively absorb and fix electrons, thereby reducing the free movement of charges within the molecular chain. This is particularly important for electrical applications that require high resistance performance, such as key insulating parts in DC GIS / GIL, which need to maintain stable electrical performance under high temperature gradients and high electric fields. The second category is large steric hindrance groups, which use their large volume to increase the molecular distance, hinder the π-π stacking effect between benzene rings, and block the charge transfer between different epoxy molecular chains; further enhance the resistance performance of epoxy resin, and improve the overall stability and durability of the material by increasing the molecular distance. On the one hand, by introducing a rigid structure in the epoxy cross-linked main chain to improve thermal stability, on the other hand, using two types of functional bridge bond functional groups, carrier traps are constructed to improve electrical performance.

[0017] The present invention also discloses an aromatic amine epoxy resin curing agent obtained by the above design method, wherein the design of the aromatic amine epoxy resin curing agent takes into account the reaction activity with the epoxy resin monomer, ensures the smooth progress of the curing process, and thus optimizes the processing performance of the epoxy resin. The thermal stability of the epoxy resin can be enhanced, the resistance performance of the epoxy resin can be significantly improved, and the smooth progress of the curing process can be ensured, thereby optimizing the processing performance of the epoxy resin.

[0018] The present invention also discloses a method for preparing an insulating epoxy resin, which is prepared by using an aromatic amine epoxy resin curing agent obtained by the above-mentioned design method. The aromatic amine molecule in the aromatic amine epoxy resin curing agent contains a benzene ring structure, so that the cured insulating epoxy resin has excellent heat resistance and can withstand the erosion of a high temperature environment without significant performance degradation. The aromatic amine epoxy resin curing agent enables the insulating epoxy resin to maintain stable performance in various chemical media, which is particularly important for insulating materials used in complex environments. The aromatic amine epoxy coating after curing can form a hard surface with high strength and hardness, so that it performs well when subjected to mechanical stress. The aromatic amine in the aromatic amine epoxy resin curing agent has high reactivity, a fast reaction speed with the epoxy resin, and can complete the curing process in a short time, thereby improving production efficiency. The presence of the benzene ring structure not only improves the heat resistance, but also gives the aromatic amine epoxy resin curing agent good oxidation resistance and stability, thereby extending the service life of the product. While maintaining high strength and hardness, it also has certain flexibility and adhesion, and can better adapt to complex application scenarios.

[0019] The present invention also discloses an insulating epoxy resin obtained by the above-mentioned preparation method. By introducing a rigid aromatic structure into the epoxy cross-linking main chain, the thermal stability of the epoxy resin is significantly improved, so that it can maintain insulation performance for a long time in a high temperature environment. The two types of functional bridge bond functional groups are used to construct carrier traps, which effectively improves the electrical properties of the epoxy resin, especially the resistance performance and breakdown strength, so that it can meet the insulation requirements of high-voltage electrical equipment. The characteristics of high thermal stability and high electrical strength make the insulating epoxy resin have a wide range of application prospects in high-voltage electrical equipment such as DC GIS / GIL. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The Fourier transform infrared spectra of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention are shown; Figure 2 The differential scanning calorimetry results of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention are shown; Figure 3 This is a comparison chart of the high-temperature DC breakdown strength and high-temperature volume resistivity results of the insulating epoxy resins obtained in Examples 1-5 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0023] The present invention is further described in detail below in conjunction with the accompanying drawings: The invention discloses a design method of an aromatic amine epoxy resin curing agent, comprising the following steps: 1) The curing agent contains two or more benzene ring structures, and the benzene ring structures are connected by functional bridge bonds; 2) The two ends of the curing agent designed above contain an amino functional group respectively, which serves as a site for cross-linking reaction with the epoxy functional group in the epoxy resin monomer, ensuring that the high thermal stability benzene ring structure can serve as the main body of the epoxy cross-linking structure, thereby improving the thermal stability of the material; 3) No high electron-withdrawing substituent group is set at the ortho position of the above-mentioned amino functional group to ensure high reactivity of the amine during the cross-linking reaction and to ensure that the material is completely cured inside when the large insulating part is cured; 4) The benzene rings of the curing agent are connected by functional bridge bonds, which are located at the 1,4 substitution position or 1,3 substitution position of the benzene ring, ensuring that the main chain has a certain degree of freedom and can perform axial rotation movement.

[0024] Furthermore, the functional bridge bonds in step 4) are divided into two categories. The first type of functional bridge bonds are strong electron-withdrawing groups that block the transmission of π electrons between benzene rings in the chain; the second type of functional bridge bonds are large steric hindrance groups that increase the molecular distance and block the electron transmission between different chains. The strong electron-withdrawing group and the large steric hindrance group are set at the para position of the amino group.

[0025] Among them, the first type of functional bridge bond is a strong electron-withdrawing group, including but not limited to -C=O or -SO2, such as one or more of Formula 1 to Formula 2: Formula 1: ; Formula 2: .

[0026] The second type of functional bridge is a large steric hindrance group, including but not limited to -C2H6, -C2F6 or -C6H 12 Etc., such as one or more of Formula 3 to Formula 5: Formula 3: ; Formula 4: ; Formula 5: .

[0027] The invention discloses a design method of an aromatic amine epoxy resin curing agent, comprising: designing at least two benzene ring structures, introducing a rigid aromatic structure into an epoxy main chain to enhance its thermal stability and improve the glass transition temperature; the benzene ring structure can provide sufficient rigidity and stability, so that the cured epoxy resin has better mechanical properties and thermal stability. Multiple benzene ring structures can enhance the intermolecular force of the curing agent, increase the crosslinking density of the epoxy resin, and thus improve its hardness, strength and heat resistance. The benzene ring structures are connected by functional bridge bonds; by introducing functional bridge bonds between the benzene rings as a means of breaking the conjugated structure of the benzene rings and improving the electrical properties, the selection and design of the functional bridge bonds are crucial to the performance of the curing agent. It connects different benzene ring structures, affecting the flexibility, reactivity of the curing agent and the performance of the final epoxy resin. By selecting a suitable functional bridge bond, the chemical properties of the curing agent, such as reaction rate, curing temperature, etc., can be regulated, thereby optimizing the processing performance and final use performance of the epoxy resin. An amino functional group is set at each end of the designed structure; the amino functional group is used as a site for cross-linking reaction with the epoxy functional group in the epoxy resin monomer. Setting an amino functional group at each end can ensure that the curing agent fully reacts with the epoxy resin to form a uniform cross-linked network. The curing agent has high reactivity and can react quickly and completely with the epoxy resin to form a dense cross-linked structure, thereby improving the mechanical properties and chemical corrosion resistance of the epoxy resin. No high electron-withdrawing substituent group is set at the ortho position of the designed amino functional group; the presence of a high electron-withdrawing substituent group will reduce the reactivity of the amino functional group, thereby affecting the reaction efficiency of the curing agent and the epoxy resin. Therefore, avoid setting such a substituent group at the ortho position of the amino functional group during design. Ensure that the amino functional group maintains a high reactivity, so that the curing agent can fully and quickly react with the epoxy resin to form a high-quality cross-linked network, thereby improving the comprehensive performance of the epoxy resin. Reasonable substitution positions can optimize the molecular configuration of the curing agent and improve its reactivity and stability. Further control the chemical and physical properties of the curing agent, such as solubility and viscosity, so that it can better adapt to different epoxy resin systems and processing conditions. It is used to prepare epoxy resins for high-voltage DC insulation with high thermal stability and high resistance. It helps to solve the electrical performance of key insulation parts in DC GIS / GIL under high temperature gradients and high electric fields.

[0028] The present invention also discloses an aromatic amine epoxy resin curing agent obtained by the above design method, wherein the design of the aromatic amine epoxy resin curing agent takes into account the reaction activity with the epoxy resin monomer, ensures the smooth progress of the curing process, and thus optimizes the processing performance of the epoxy resin. The thermal stability of the epoxy resin can be enhanced, the resistance performance of the epoxy resin can be significantly improved, and the smooth progress of the curing process can be ensured, thereby optimizing the processing performance of the epoxy resin.

[0029] The invention discloses a method for preparing an insulating epoxy resin, comprising the following steps: 1) Dissolving the aromatic amine epoxy resin curing agent: dissolving the aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, and heating and stirring to make the aromatic amine epoxy resin curing agent completely dissolved in the solvent to obtain an aromatic amine epoxy resin curing agent solution; 2) Dispersion of aromatic amine epoxy resin curing agent: Add the aromatic amine epoxy resin curing agent solution into the preheated epoxy resin monomer, and heat and stir under continuous vacuum; 3) Casting: Add filler (usually Al2O3 particles) to the above mixture, heat and stir, and degas to obtain casting material; 4) Curing: pour the casting material obtained in step 3) into a preheated mold for degassing, then raise the curing environment temperature to 120-140°C and keep it warm for 60-180 minutes; then raise the temperature to 150-180°C after 60-120 minutes and keep it warm for 120-300 minutes; then raise the temperature to 190-210°C after 60-120 minutes and keep it warm for 60-180 minutes; then stop heating, cool naturally to room temperature with the furnace, demold, and obtain insulating epoxy resin.

[0030] Furthermore, in step 1), the usage ratio of aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15) g: (2-8) mL: (10-15) mL.

[0031] The heating temperature of the solution is between 50 and 80°C, and the heating and stirring time is between 20 and 40 minutes.

[0032] Furthermore, in step 2), the preheating temperature of the epoxy resin is 50-80° C. for 4-8 hours to improve the fluidity of the epoxy resin and remove moisture.

[0033] The heating and stirring temperature is 60~120℃, and the stirring time is 10~60min, depending on the reactivity of the curing agent and the solvent content, so that the solvent is completely volatilized and the vacuum degree is 1~10mbar.

[0034] Furthermore, in step 3), the degassing treatment refers to keeping the epoxy resin mixture and the filler warm and pressurized for 30 to 120 minutes under the conditions of a vacuum degree of 1 to 10 mbar and a temperature of 60 to 120° C., so as to ensure that the viscosity of the casting material is 6000 to 12000 mPa·s.

[0035] The weight ratio of aromatic amine epoxy resin curing agent: epoxy resin monomer: filler is (5-30): (10-40): (30-60); the heating temperature for heating and stirring is 60~120℃, and the stirring time is 10-30min.

[0036] Furthermore, in step 4), the mold needs to be sprayed with a release agent in advance and then heated to 100°C.

[0037] The degassing treatment conditions are: at a vacuum degree of 1-10 mbar, keep the temperature and pressure at 60-120°C for 30-60 minutes.

[0038] The invention discloses a method for preparing an insulating epoxy resin, which is prepared by using an aromatic amine epoxy resin curing agent obtained by the above-mentioned design method. The use of a mixed solvent helps the aromatic amine epoxy resin curing agent to dissolve better, and heating and stirring ensure that the curing agent is completely dissolved in the solvent, providing a uniform and stable curing agent solution for subsequent steps, which is conducive to improving the quality and performance of the final product. Preheating the epoxy resin monomer helps to reduce its viscosity and facilitate mixing with the curing agent solution. Continuous vacuuming and mixing under heating and stirring conditions help to remove bubbles and volatiles in the mixture and improve the uniformity and density of the casting material. Adding fillers and heating and stirring again can further improve the properties of the casting material, such as mechanical strength, heat resistance, etc. The first degassing treatment helps to further remove the gas in the casting material and reduce the pores and defects in the final product. Preheating the mold helps the casting material to better fill the mold and reduce the stress caused by temperature differences. The second degassing treatment further ensures that the gas in the casting material is removed, improving the density and insulation performance of the product. The curing process enables the casting material to form a stable chemical structure, giving the final product the required mechanical strength and electrical properties. Demolding after natural cooling to room temperature helps reduce product deformation or cracking caused by rapid temperature changes.

[0039] The present invention also discloses an insulating epoxy resin obtained by the above-mentioned preparation method. By introducing a rigid aromatic structure into the epoxy cross-linking main chain, the thermal stability of the epoxy resin is significantly improved, so that it can maintain insulation performance for a long time in a high temperature environment. The two types of functional bridge bond functional groups are used to construct carrier traps, which effectively improves the electrical properties of the epoxy resin, especially the resistance performance and breakdown strength, so that it can meet the insulation requirements of high-voltage electrical equipment. The characteristics of high thermal stability and high electrical strength make the insulating epoxy resin have a wide range of application prospects in high-voltage electrical equipment such as DC GIS / GIL.

[0040] The raw materials used in the embodiments of the present invention are as follows: Bisphenol A epoxy resin (DGEBA, WSR618 E51, epoxy value: 0.51 eq. / 100 g) was provided by Nantong Xingchen Synthetic Materials Co., Ltd., China.

[0041] 4,4'-Diaminodiphenylmethane (DDM), 4,4'-diaminobenzophenone (DBP), and 2,2-bis(4-aminophenyl)hexafluoropropane (6FDAM) were provided by Shanghai MacLean Biochemical Technology Co., Ltd., China.

[0042] Methyltetrahydrophthalic anhydride (MTHPA), 2,4,6-trimethylphenol, acetone, and N,N-dimethylacetamide (DMAc) were provided by Sigma-Aldrich, USA.

[0043] Example 1 A method for preparing an insulating epoxy resin comprises the following steps: In this embodiment 1, 4,4'-diaminobenzophenone (DBP) containing two benzene ring structures and a strong electron-withdrawing group -C=O is used as an aromatic amine epoxy resin curing agent, and the functional bridge bond is substituted at the 1,4 position on the benzene ring (see Formula 3). The preparation method of the insulating epoxy resin provided includes the following steps: 1) Dissolve 10 g of DBP in 2 mL of acetone and 10 mL of dimethylacetamide, heat to 50 °C, and heat and stir for 20 min to completely dissolve DBP to obtain an aromatic amine epoxy resin curing agent solution; 2) Preheat the epoxy resin in an oven at 60°C for 5 hours, then mix the aromatic amine epoxy resin curing agent solution with 10g of epoxy resin, and heat and stir in a continuously vacuumed beaker at 70°C for 30 minutes; then add 30g of alumina filler to the mixture, heat and stir at 60°C for 30 minutes, and degas at 60°C for 30 minutes under a vacuum degree of 1mbar to obtain a casting material; 3) The castable obtained above is heated to 120°C, and the mold is sprayed with a release agent and preheated at 100°C, and the castable is poured into the mold, and degassed at 100°C for 60 minutes under a vacuum degree of 10 mbar; 4) Then, the ambient temperature is raised to 140°C over 60 minutes and kept at this temperature for 60 minutes; then, the ambient temperature is raised to 180°C over 60 minutes and kept at this temperature for 120 minutes; then, the ambient temperature is raised to 200°C over 60 minutes and kept at this temperature for 60 minutes; then, the heating is stopped, the mixture is naturally cooled to room temperature in the furnace, and the mixture is demolded to obtain an insulating epoxy resin named EP-DBP.

[0044] Example 2 A method for preparing an insulating epoxy resin comprises the following steps: In this embodiment 2, 4,4'-diaminodiphenyl sulfone (DDS) containing two benzene ring structures and a strong electron-withdrawing group -SO2 is used as an aromatic amine epoxy resin curing agent (see Formula 2). The preparation method of the insulating epoxy resin provided includes the following steps: 1) 30g DDS was dissolved in 5mL acetone and 12mL dimethylacetamide, heated to 60℃, and heated and stirred for 30min to completely dissolve the DDS to obtain an aromatic amine epoxy resin curing agent solution; 2) Preheat the epoxy resin in an oven at 80°C for 4 hours, then mix the aromatic amine epoxy resin curing agent solution with 20g of epoxy resin, and heat and stir in a continuously vacuumed beaker at 60°C for 30 minutes; then add 30g of alumina filler to the mixture, heat and stir at 60°C for 30 minutes, and degas at 80°C for 60 minutes under a vacuum degree of 5mbar to obtain a casting material; 3) The castable obtained above is heated to 130°C, and the mold is sprayed with a release agent and preheated at 100°C. The castable is poured into the mold and degassed at 100°C for 60 minutes under a vacuum degree of 5 mbar; 4) Subsequently, the ambient temperature is raised to 120°C over 60 minutes and kept at this temperature for 180 minutes; then, the ambient temperature is raised to 150°C over 120 minutes and kept at this temperature for 180 minutes; then, the ambient temperature is raised to 190°C over 60 minutes and kept at this temperature for 180 minutes; then, the heating is stopped, the sample is naturally cooled to room temperature in the furnace, and the sample is demolded to obtain an insulating epoxy resin named EP-DDS.

[0045] Example 3 A method for preparing an insulating epoxy resin comprises the following steps: In this embodiment 3, 2,2-bis(4-aminophenyl)propane (DAM) containing two benzene ring structures and a large steric hindering group -C2H6 is used as an aromatic amine epoxy resin curing agent (see Formula 3). The preparation method of the insulating epoxy resin provided includes the following steps: 1) Dissolve 12g DAM in 6mL acetone and 14mL dimethylacetamide, heat to 60℃, and stir for 25min to completely dissolve DAM to obtain aromatic amine epoxy resin curing agent solution; 2) Preheat the epoxy resin in an oven at 50°C for 8 hours, then mix the aromatic amine epoxy resin curing agent solution with 35g of epoxy resin, and heat and stir in a continuously vacuumed beaker at 80°C for 20 minutes; then add 45g of alumina filler to the mixture, heat and stir at 60°C for 10 minutes, and degas at 90°C for 45 minutes under a vacuum degree of 3mbar to obtain a casting material; 3) The castable obtained above is heated to 115°C, and the mold is sprayed with a release agent and preheated at 100°C. The castable is poured into the mold and degassed at 90°C for 60 minutes under a vacuum degree of 5 mbar; 4) Subsequently, the ambient temperature is raised to 130°C over 60 minutes and kept at this temperature for 90 minutes; then, the ambient temperature is raised to 150°C over 100 minutes and kept at this temperature for 120 minutes; then, the ambient temperature is raised to 210°C over 120 minutes and kept at this temperature for 120 minutes; then, the heating is stopped, the sample is naturally cooled to room temperature in the furnace, and the sample is demolded to obtain an insulating epoxy resin named EP-DAM.

[0046] Example 4 A method for preparing an insulating epoxy resin comprises the following steps: In this embodiment 4, 2,2-bis(4-aminophenyl)hexafluoropropane (6FDAM) containing two benzene ring structures and a bulky bridge bond -C2F6 is used as an aromatic amine epoxy resin curing agent, and the functional bridge bond is substituted at the 1,4 position on the benzene ring (see Formula 4). The preparation method for preparing the insulating epoxy resin provided includes the following steps: 1) Dissolve 15 g of 6FDAM in 8 mL of acetone and 15 mL of dimethylacetamide, heat to 80 °C, and heat and stir for 40 min to completely dissolve 6FDAM to obtain an aromatic amine epoxy resin curing agent solution; 2) preheating the epoxy resin in an oven at 50°C for 5 hours, then mixing the aromatic amine epoxy resin curing agent solution with 40g of epoxy resin, heating and stirring in a continuously vacuumed beaker at 120°C for 60 minutes; then adding 60g of alumina filler to the mixture, heating and stirring at 120°C for 30 minutes, and degassing at 120°C for 120 minutes under a vacuum degree of 10mbar to obtain a casting material; 3) The castable obtained above is heated to 140°C, and the mold is sprayed with a release agent and preheated at 100°C. The castable is poured into the mold and degassed at 100°C for 60 minutes under a vacuum degree of 1 mbar; 4) Then, the ambient temperature is raised to 140°C over 60 minutes and kept at this temperature for 60 minutes; then, the ambient temperature is raised to 180°C over 60 minutes and kept at this temperature for 120 minutes; then, the ambient temperature is raised to 200°C over 60 minutes and kept at this temperature for 60 minutes; then, the heating is stopped, the mixture is naturally cooled to room temperature in the furnace, and the mixture is demolded to obtain an insulating epoxy resin named EP-6FDAM.

[0047] Example 5 A method for preparing an insulating epoxy resin comprises the following steps: In this embodiment 5, a structure containing two benzene rings and a large steric hindrance group -C6H 12 1,1-bis(4-aminophenyl)cyclohexane (CHA) is used as an aromatic amine epoxy resin curing agent (see Formula 5), ​​and a method for preparing an insulating epoxy resin is provided, comprising the following steps: 1) Dissolve 10 g CHA in 7 mL acetone and 13 mL dimethylacetamide, heat to 75 °C, and heat and stir for 25 min to completely dissolve CHA to obtain an aromatic amine epoxy resin curing agent solution; 2) Preheat the epoxy resin in an oven at 67°C for 5 hours, then mix the aromatic amine epoxy resin curing agent solution with 28g of epoxy resin, and heat and stir in a continuously vacuumed beaker at 110°C for 40 minutes; then add 50g of alumina filler to the mixture, heat and stir at 110°C for 30 minutes, and degas at 90°C for 70 minutes under a vacuum degree of 8mbar to obtain a casting material; 3) The castable obtained above is heated to 110°C, and the mold is sprayed with a release agent and preheated at 100°C, and the castable is poured into the mold, and degassed at 110°C for 60 minutes under a vacuum degree of 1 mbar; 4) Subsequently, the ambient temperature is raised to 140°C over 60 minutes and kept at this temperature for 120 minutes; then, the ambient temperature is raised to 180°C over 120 minutes and kept at this temperature for 300 minutes; then, the ambient temperature is raised to 210°C over 120 minutes and kept at this temperature for 180 minutes; then, the heating is stopped, the sample is naturally cooled to room temperature in the furnace, and the sample is demolded to obtain an insulating epoxy resin named EP-CHA.

[0048] Comparative Example 1: A method for preparing an insulating epoxy resin comprises the following steps: In this comparative example 1, 4,4'-diaminodiphenylmethane (DDM) containing two benzene ring structures is used as a curing agent, and the two benzene rings are directly connected by a methylene group. The preparation method of the epoxy resin sample provided includes the following steps: 1) Dissolve 10 g of DDM in 2 mL of acetone and 10 mL of dimethylacetamide, heat to 60 °C, and heat and stir for 20 min to completely dissolve the DDM; 2) Preheat the epoxy resin in an oven at 60°C for 5 hours, then mix the aromatic amine epoxy resin curing agent solution with 15g of epoxy resin, and heat and stir in a continuously vacuumed beaker at 70°C for 30 minutes; then add 40g of alumina filler to the mixture, heat and stir at 60°C for 30 minutes to obtain a casting material; 3) The castable obtained above is heated to 100°C, and the mold is sprayed with a release agent and preheated at 100°C, and the castable is poured into the mold, and degassed at 100°C for 60 minutes under a vacuum degree of 10 mbar; 4) Then, the ambient temperature is raised to 140°C over 60 minutes and kept at this temperature for 60 minutes; then, the ambient temperature is raised to 180°C over 60 minutes and kept at this temperature for 120 minutes; then, the ambient temperature is raised to 200°C over 60 minutes and kept at this temperature for 60 minutes; then, the heating is stopped, the mixture is naturally cooled to room temperature in the furnace, and the mixture is demolded to obtain an insulating epoxy resin named EP-DDM.

[0049] The curing agent used in Comparative Example 1 here is a conventional commonly used aniline curing agent, and the 1,4 substitution positions between the two benzene rings are directly connected by a methylene group, so that a charge transfer channel is formed between the benzene ring structures within the molecular chain and between the molecular chains, making its electrical insulation performance weak. Therefore, as a comparison, we use this to verify the effect of the introduction of a functional bridge bond on the electrothermal properties of aniline-cured epoxy resin.

[0050] See also Figure 1 The Fourier infrared spectra of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention are shown in Figure 1. The insulating epoxy resins prepared in Examples 1-5 and Comparative Example 1 were tested by Fourier infrared, and the test results were compared and analyzed. The analysis results are shown in Figure 1. Figure 1 As shown, it can be seen that the methods provided in Examples 1-5 and Comparative Example 1 all ensure that the cross-linking reaction between the epoxy resin and the curing agent is complete.

[0051] See also Figure 2 The figure is a differential scanning calorimetry result diagram of the insulating epoxy resin obtained in Examples 1-5 of the present invention and Comparative Example 1; for the insulating epoxy resin prepared in Examples 1-5 and Comparative Example 1, in order to analyze and compare the effect of the proposed method on thermal stability, a differential scanning calorimeter was used to measure the insulating epoxy resin at 10°C / min in a nitrogen atmosphere, and the test results were compared and analyzed. The analysis results are as follows: Figure 2 As shown, it can be seen that the introduction of benzene rings leads to an increase in the glass transition temperature of the epoxy resin, which is much higher than the glass transition temperature of the traditional anhydride-cured epoxy resin (about 120°C), indicating that the thermal stability of the epoxy resin has been improved due to the introduction of multi-benzene ring curing agent.

[0052] See also Figure 3 : is a comparison chart of the high-temperature DC breakdown strength and high-temperature volume resistivity results of the insulating epoxy resin obtained in Examples 1-5 of the present invention and Comparative Example 1; in order to verify the effect of the proposed method on the high-temperature electrical properties of the epoxy resin, the insulating epoxy resin obtained in Examples 1-5 and Comparative Example 1 was tested for high-temperature electrical properties. Under 120°C, the DC breakdown strength test results and the DC volume resistivity test results are as follows: Figure 3 As shown. It can be found that aromatic amine epoxy resin curing agents containing strong electron-withdrawing bridge bonds and large-volume bridge bonds can maintain high electrical properties at high temperatures. For EP-6FDAM, its breakdown strength at 120°C reached 393.83 kV / mm, and its volume resistivity reached 2.91×10 14 Ω·cm, which are much higher than the performance of traditional anhydride-cured epoxy resins.

[0053] The present invention proposes a strategy for developing electrical epoxy resin formulations with high thermal stability and high resistance performance using polyaromatic structures and functional bridges. The core is to use polyaromatic diamines as the curing agent component of epoxy resin, introduce rigid aromatic structures into the epoxy main chain to enhance its thermal stability and increase the glass transition temperature; in addition, functional bridges are introduced between benzene rings as a means to break the conjugated structure of the benzene rings and improve electrical performance; the introduced functional bridges are divided into two categories, the first category is a strong electron-withdrawing group, which constructs an electron trap between the benzene ring structure to block the charge transfer within the epoxy molecular chain, and the second category is a large steric hindrance group, which uses its large volume to hinder the π-π stacking effect between the benzene rings to block the charge transfer between different epoxy molecular chains. By designing the molecular structure of the polyaniline functional bridge amine curing agent, on the one hand, a rigid structure is introduced into the epoxy cross-linking main chain to improve thermal stability, and on the other hand, two types of functional bridge functional groups are used to construct carrier traps and improve electrical performance. The formed epoxy resin material with high thermal stability and high electrical strength is helpful to solve the electrical performance of key insulating parts in DC GIS / GIL under high temperature gradient and high electric field.

[0054] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A design method for an aromatic amine epoxy resin curing agent, characterized in that: include: Design at least two benzene ring structures, and the benzene ring structures are connected by a functional bridge bond; An amino functional group is provided at each end of the designed structure; No high electron-withdrawing substituent group is provided at the ortho position of the designed amino functional group; an aromatic amine epoxy resin curing agent is obtained; The functional bridge bond is arranged at the 1,4 substitution position or the 1,3 substitution position of the benzene ring structure.

2. The design method of the aromatic amine epoxy resin curing agent according to claim 1, characterized in that: The functional bridge bond is a strong electron-withdrawing group or a large steric hindrance group.

3. The design method of the aromatic amine epoxy resin curing agent according to claim 2, characterized in that: The strong electron withdrawing group is -C=O or -SO2.

4. The design method of the aromatic amine epoxy resin curing agent according to claim 2, characterized in that: The large steric hindering group is -C2H6, -C2F6 or -C6H 12 .

5. An aromatic amine epoxy resin curing agent, characterized in that: It is obtained by adopting the design method described in any one of claims 1 to 4.

6. A method for preparing an insulating epoxy resin, characterized in that: The preparation method of the aromatic amine epoxy resin curing agent obtained by the design method according to any one of claims 1 to 4 comprises the following steps: 1) dissolving the aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, heating and stirring for the first time until it is completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution; 2) adding the aromatic amine epoxy resin curing agent solution obtained in step 1) to the preheated epoxy resin monomer, and heating and stirring for a second time under continuous vacuum; then adding filler, heating and stirring for a third time, and performing a first degassing treatment to obtain a casting material; 3) The casting material obtained in step 2) is poured into a preheated mold, and a second degassing treatment is performed. After curing, the casting material is naturally cooled to room temperature, and demolded to obtain an insulating epoxy resin.

7. The method for preparing the insulating epoxy resin according to claim 6, characterized in that: In step 1), the usage ratio of the aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15) g: (2-8) mL: (10-15) mL; The heating temperature of the first heating and stirring is 50-80° C., and the stirring time is 20-40 min.

8. The method for preparing the insulating epoxy resin according to claim 6, characterized in that: The weight ratio of the aromatic amine epoxy resin curing agent: epoxy resin monomer: filler is (5-30): (10-40): (30-60); The preheating temperature of the epoxy resin monomer is 50-80°C, and the preheating time is 4-8h; The heating temperature of the second heating and stirring is 60-120°C, and the stirring time is 10-60min; The heating temperature of the third heating and stirring is 60-120°C, and the stirring time is 10-30min; The conditions of the first degassing treatment are: keeping the temperature and pressure at 60-120° C. for 30-120 min under a vacuum degree of 1-10 mbar.

9. The method for preparing the insulating epoxy resin according to claim 6, characterized in that: In step 3), the mold is sprayed with a release agent in advance and heated to 100° C.; The conditions of the second degassing treatment are: keeping temperature and pressure at 60-120°C for 30-60 minutes under a vacuum degree of 1-10 mbar; The curing conditions are: heating to 120-140° C., keeping warm for 60-180 min; then heating to 150-180° C. over 60-120 min, keeping warm for 120-300 min; then heating to 190-210° C. over 60-120 min, keeping warm for 60-180 min.

10. An insulating epoxy resin, characterized in that: The method is prepared by any one of claims 6 to 9.

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