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

Abstract

The application discloses a kind of aromatic amine epoxy resin curing agent and its design method and insulating epoxy resin and its preparation method, belong to insulating technical field.At least two benzene ring structures are designed, and the benzene ring structures are connected by functional bridge bond;An amino functional group is respectively arranged at the two ends of the designed structure;High electron-withdrawing substituent group is not arranged at the ortho position of the designed amino functional group;Get aromatic amine epoxy resin curing agent;Functional bridge bond is arranged at the 1,4 or 1,3 substitution site of benzene ring structure.Multiple aromatic diamines are used as the curing agent component of epoxy resin, rigid aromatic structure is introduced into the epoxy main chain to enhance its thermal stability and improve the glass transition temperature;Functional bridge bond is introduced between benzene rings as breaking benzene ring conjugated structure, to improve electrical performance.Can prepare high-temperature stability and high-resistance high-voltage direct-current insulating epoxy resin.Help to solve the electrical performance of key insulating parts in DC GIS / GIL under the action of high temperature gradient and high electric field.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of insulation, and particularly relates to a curing agent for aromatic amine epoxy resin, a design method thereof, and an insulating epoxy resin and a preparation method thereof. BACKGROUND

[0002] With large-scale development of offshore wind power and plateau hydropower, DC GIS / GIL has become the main equipment for large-scale clean energy transmission in the future due to small land occupation, high reliability, and small environmental impact. Under DC voltage, the electric field in the material is resistive distribution, which is different from the resistive distribution of the electric field in the internal equipment under traditional DC voltage. This is easy to accumulate surface charge on the surface of the insulating material, and induce surface flashover failure. 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 greatly with the increase of temperature. A radial temperature gradient is formed inside the insulator, the maximum electric field position moves to the ground shell, resulting in a decrease in effective insulation distance, further distortion of the surface electric field of the material, and a large decrease in surface flashover voltage.

[0003] At present, researchers mainly propose to use micron particles and nanoparticles for material modification to increase the electrical properties of epoxy composites. However, due to the large specific surface area of nanoparticles, agglomeration easily occurs, which cannot be uniformly dispersed in the material, and the current requirements of large-scale industrial applications cannot be met. In addition, the glass transition temperature of the commercial epoxy resin matrix material used for electrical insulation is only about 120℃, which further limits the electrical properties of the electrical epoxy material under high temperature gradient and high electric field conditions. The problems in the related art have not yet been effectively solved, 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 the epoxy resin matrix material in the modification process of the epoxy composite, it is urgent to find a new high-temperature-stable and high-resistive epoxy resin for high-voltage direct-current insulation and a preparation method thereof to meet the design requirements of key insulating parts in DC GIS / GIL under high temperature gradient and high electric field conditions. SUMMARY

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

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The application discloses a design method of an aromatic amine epoxy resin curing agent.

[0008] Design at least two benzene ring structures, and connect the benzene ring structures through a functional bridge; set one amino functional group at two ends of the designed structure; do not set a high electron-withdrawing substituent group at an ortho position of the designed amino functional group; and obtain the aromatic amine epoxy resin curing agent.

[0009] The functional bridge is arranged at a 1, 4 substitution position or a 1, 3 substitution position of the benzene ring structure.

[0010] Preferably, the functional bridge is a strong electron-withdrawing group or a large steric hindrance group.

[0011] Further preferably, the strong electron-withdrawing group is -C=O or -SO2.

[0012] Further preferably, the large steric hindrance group is -C2H6, -C2F6 or -C6H 12 .

[0013] The application further discloses an aromatic amine epoxy resin curing agent obtained by using the design method.

[0014] The application further discloses a preparation method of an insulating epoxy resin, which is prepared by using the aromatic amine epoxy resin curing agent obtained by using the design method, and comprises the following steps.

[0015] 1) dissolving the aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, performing first heating and stirring until complete dissolution, and obtaining an aromatic amine epoxy resin curing agent solution;

[0016] 2) adding the aromatic amine epoxy resin curing agent solution obtained in the step 1) into preheated epoxy resin monomers, and performing second heating and stirring under the condition of continuous vacuum extraction; then adding fillers, performing third heating and stirring, and performing first degassing treatment, and obtaining a pouring material;

[0017] 3) pouring the pouring material obtained in the step 2) into a preheated mold, performing second degassing treatment, naturally cooling to room temperature after curing, demolding, and obtaining the insulating epoxy resin.

[0018] Preferably, in the step 1), the use amount ratio of the aromatic amine epoxy resin curing agent, the acetone and the dimethylacetamide is (10-15) g:(2-8) mL:(10-15) mL.

[0019] The heating temperature of the first heating and stirring is 50-80 DEG C, and the stirring time is 20-40 min.

[0020] Preferably, the weight ratio of the aromatic amine epoxy resin curing agent, the epoxy resin monomer and the filler is (5-30):(10-40):(30-60);

[0021] The preheating temperature of the epoxy resin monomer is 50-80℃, and the preheating time is 4-8h;

[0022] The heating temperature of the third heating and stirring is 60-120℃, and the stirring time is 10-30min;

[0023] The heating temperature of the third heating and stirring is 60-120℃, and the stirring time is 10-30min;

[0024] The first degassing treatment is carried out at a vacuum degree of 1-10mbar, and the temperature is kept at 60-120℃ for 30-120min;

[0025] Preferably, in step 3), the mold is pre-sprayed with a release agent and heated to 100℃;

[0026] The second degassing treatment is carried out at a vacuum degree of 1-10mbar, and the temperature is kept at 60-120℃ for 30-60min;

[0027] The curing condition is as follows: the temperature is raised to 120-140℃, and kept for 60-180min; then the temperature is raised to 150-180℃ for 60-120min, and kept for 120-300min; then the temperature is raised to 190-210℃ for 60-120min, and kept for 60-180min.

[0028] The application further discloses an insulating epoxy resin prepared by the preparation method.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] The application discloses a design method of aromatic amine epoxy resin curing agent, comprising the following steps: designing at least two benzene ring structures, introducing rigid aromatic structures into the epoxy main chain to enhance its thermal stability and improve the glass transition temperature; enabling it to maintain performance unchanged at a higher temperature, thereby widening the application range of the epoxy resin; introducing a functional bridge between the benzene rings as a means to break the benzene ring conjugated structure, effectively improving the electrical performance of the epoxy resin, especially the introduction of strong electron-withdrawing groups and large steric hindering groups, which respectively build electron traps and hinder the pi-pi stacking effect between benzene rings, block the charge transport within and between the epoxy molecular chains, and significantly improve the resistance performance. An amino functional group is arranged at both ends of the designed structure; the amino functional group serves as a crosslinking reaction site with the epoxy functional group in the epoxy resin monomer, and the arrangement of the amino functional group at both ends can ensure sufficient reaction of the curing agent with the epoxy resin to form a uniform crosslinking network. Because the high electron-withdrawing group can greatly reduce the reactivity, no high electron-withdrawing substituent group is arranged at the ortho position of the designed amino functional group to ensure the high reactivity of the amine during the crosslinking reaction and ensure complete curing of the material inside the large insulating part. The functional bridge is arranged at the 1,4 substitution position or the 1,3 substitution position of the benzene ring structure; the 1,2 substitution position may cause too low reactivity and subsequent curing reaction difficulty. Reasonable substitution position ensures that the main chain has a certain degree of freedom and can perform axial rotation movement. The design method of the aromatic amine epoxy resin curing agent disclosed by the application starts from the molecular structure design, systematically considers the demand for improving thermal stability and electrical performance, and provides scientific guidance for developing high-performance epoxy resin curing agents. By adjusting the benzene ring structure, the type and substitution position of the functional bridge, the performance of the curing agent can be flexibly controlled to adapt to different application requirements. The aromatic amine epoxy resin curing agent can be used for preparing high-temperature stability and high-resistance high-voltage direct-current insulation epoxy resin, and is helpful to solve the electrical performance of key insulating parts in direct-current GIS / GIL under the action of high temperature gradient and high electric field.

[0031] Further, the introduced functional bridge bonds are divided into two categories. The first category is a strong electron-withdrawing group, which builds an electron trap between the benzene ring structures to block the charge transport within the molecular chain of the epoxy. The strong electron-withdrawing group 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 insulation components in DC GIS / GIL, which need to maintain stable electrical performance under high temperature gradients and high electric fields. The second category is a large steric hindrance group, which increases the intermolecular distance by using its large volume to hinder the π-π stacking effect between benzene rings, thereby blocking the charge transport between different epoxy molecular chains. This further enhances the electrical resistance performance of the epoxy resin, and by increasing the intermolecular distance, it improves the overall stability and durability of the material. On the one hand, the introduction of rigid structures in the epoxy crosslinking backbone improves thermal stability, and on the other hand, the use of two types of functional bridge bond functional groups builds carrier traps to improve electrical performance.

[0032] The application also discloses the aromatic amine epoxy resin curing agent obtained by the design method, which considers the reactivity with the epoxy resin monomer, ensures the smooth progress of the curing process, and optimizes the processing performance of the epoxy resin. The aromatic amine epoxy resin curing agent can enhance the thermal stability of the epoxy resin, significantly improve the electrical resistance performance of the epoxy resin, ensure the smooth progress of the curing process, and optimize the processing performance of the epoxy resin.

[0033] The application also discloses a preparation method of an insulating epoxy resin using the aromatic amine epoxy resin curing agent obtained by the 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 cured aromatic amine epoxy coating can form a hard surface with high strength and hardness, making it perform well under mechanical stress. The aromatic amine in the aromatic amine epoxy resin curing agent has high reactivity, and the reaction with the epoxy resin is fast, enabling the curing process to be completed in a short time and improving production efficiency. The presence of the benzene ring structure not only improves the heat resistance but also endows the aromatic amine epoxy resin curing agent with good oxidation resistance and stability, prolonging the service life of the product. While maintaining high strength and hardness, it also has certain flexibility and adhesion, which can better adapt to complex application scenarios.

[0034] The application also discloses the insulating epoxy resin prepared by the preparation method. By introducing the rigid aromatic structure into the epoxy cross-linking main chain, the thermal stability of the epoxy resin is improved significantly, so that the epoxy resin can maintain the insulation performance for a long time in a high-temperature environment. By using two types of functional bridge bond functional groups to build carrier traps, the electrical performance of the epoxy resin is effectively improved, especially the resistance performance and the breakdown strength, so that the epoxy resin 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 application prospect in high-voltage electrical equipment such as direct-current GIS / GIL. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The Fourier infrared spectrum of the insulating epoxy resin obtained in the examples 1-5 and the comparative example 1 of the application;

[0036] Figure 2 The differential scanning calorimetry result graph of the insulating epoxy resin obtained in the examples 1-5 and the comparative example 1 of the application;

[0037] Figure 3 The high-temperature direct-current breakdown strength and high-temperature volume resistivity result comparison graph of the insulating epoxy resin obtained in the examples 1-5 and the comparative example 1 of the application. DETAILED DESCRIPTION

[0038] In order to make the personnel in the technical field better understand the application scheme, the technical scheme in the embodiments of the application will be described clearly and completely in combination with the drawings in the embodiments of the application. Obviously, the described embodiments are only a part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the protection scope of the application.

[0039] It should be noted that the terms "first", "second" and the like in the specification and claims of the application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0040] The application will be described in further detail below in combination with the drawings:

[0041] The application discloses a design method of an aromatic amine epoxy resin curing agent, and comprises the following steps:

[0042] 1) the curing agent comprises two or more benzene ring structures, and the benzene ring structures are connected through functional bridge bonds;

[0043] 2) one amino functional group is arranged at each end of the designed curing agent, as a crosslinking reaction position with an epoxy functional group in an epoxy resin monomer, so that the high-heat-stable benzene ring structure can be used as a main body of an epoxy crosslinking structure, and the thermal stability of the material is improved;

[0044] 3) no high electron-withdrawing substituent group is arranged at the ortho position of the amino functional group, so that the high reactivity of the amine during the crosslinking reaction is ensured, and the internal curing of the material during the curing of a large insulating part is ensured;

[0045] 4) the benzene rings of the curing agent are connected through functional bridge bonds, the positions of the functional bridge bonds are located at 1,4 substitution positions or 1,3 substitution positions of the benzene rings, and the main chain has a certain degree of freedom and can perform axial rotation movement.

[0046] Further, the functional bridge bonds in step 4) are divided into two categories, the first category of functional bridge bonds is a strong electron-withdrawing group, which blocks the transmission of pi electrons between the benzene rings in the chain; the second category of functional bridge bonds is a large steric hindrance group, which increases the intermolecular distance and blocks the electron transmission between different chains. The strong electron-withdrawing group and the large steric hindrance group are arranged at the para position of the amino group.

[0047] The first category of functional bridge bonds is a strong electron-withdrawing group, including but not limited to -C=O or -SO2, and the like, such as one or more of formula 1 to formula 2:

[0048] Formula 1:

[0049] ;

[0050] Formula 2:

[0051] .

[0052] The second category of functional bridge bonds is a large steric hindrance group, including but not limited to -C2H6, -C2F6 or -C6H 12 , and the like, such as one or more of formula 3 to formula 5:

[0053] Formula 3:

[0054] ;

[0055] Formula 4:

[0056] ;

[0057] Formula 5:

[0058] .

[0059] The design method of the aromatic amine epoxy resin curing agent disclosed in the application comprises: designing at least two benzene ring structures, introducing rigid aromatic structures into the 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 forces of the curing agent, improve 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 benzene rings as a means to break the conjugated structure of benzene rings and improve electrical performance, the selection and design of functional bridge bonds are crucial to the performance of the curing agent. It connects different benzene ring structures and affects the flexibility, reactivity of the curing agent and the performance of the final epoxy resin. By selecting appropriate functional bridge bonds, the chemical properties of the curing agent, such as reaction rate, curing temperature, etc. can be controlled, and the processing performance and final use performance of the epoxy resin can be optimized. An amino functional group is arranged at both ends of the designed structure; the amino functional group serves as a site for crosslinking reaction with the epoxy functional group in the epoxy resin monomer, and the arrangement of an amino functional group at both ends can ensure the full reaction of the curing agent with the epoxy resin to form a uniform crosslinking network. The curing agent has high reaction activity and can quickly and completely react with the epoxy resin to form a dense crosslinking structure, thereby improving the mechanical properties and chemical corrosion resistance of the epoxy resin. No high electron-withdrawing substituent group is arranged 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, when designing, avoid arranging such substituent groups at the ortho position of the amino functional group. Ensure that the amino functional group maintains high reactivity, so that the curing agent can fully and quickly react with the epoxy resin to form a high-quality crosslinking network, thereby improving the comprehensive performance of the epoxy resin. Reasonable substitution position can optimize the molecular configuration of the curing agent, improve its reactivity and stability. Further regulate the chemical properties and physical properties of the curing agent, such as solubility, viscosity, etc., so that it can better adapt to different epoxy resin systems and processing conditions. It is used for preparing high-thermal-stability and high-resistance epoxy resin for high-voltage direct-current insulation. It helps to solve the electrical performance of key insulation parts in DC GIS / GIL under the action of high temperature gradient and high electric field.

[0060] The application also discloses the aromatic amine epoxy resin curing agent obtained by the design method, the design of the aromatic amine epoxy resin curing agent considers the reactivity with the epoxy resin monomer, ensures the smooth progress of the curing process, and thus optimizes the processing performance of the epoxy resin.

[0061] The application discloses a preparation method of an insulating epoxy resin.

[0062] 1) Dissolution of the aromatic amine epoxy resin curing agent: the aromatic amine epoxy resin curing agent is dissolved in a mixed solvent of acetone and dimethylacetamide, and heated and stirred so that the aromatic amine epoxy resin curing agent is completely dissolved in the solvent to obtain an aromatic amine epoxy resin curing agent solution;

[0063] 2) Dispersion of the aromatic amine epoxy resin curing agent: the aromatic amine epoxy resin curing agent solution is added into the preheated epoxy resin monomer, and heated and stirred under the condition of continuous vacuum extraction;

[0064] 3) Casting: filler (generally Al2O3 particles) is added into the mixture, heated and stirred, and degassing treatment is performed to obtain a casting material;

[0065] 4) Curing: the casting material obtained in step 3) is cast into a preheated mold, degassing treatment is performed, then the curing environment temperature is increased to 120-140 DEG C, and the temperature is kept for 60-180 min; then the temperature is increased to 150-180 DEG C for 60-120 min, and the temperature is kept for 120-300 min; then the temperature is increased to 190-210 DEG C for 60-180 min; then the heating is stopped, and the mold is naturally cooled to room temperature in the furnace, and the mold is demolded to obtain the insulating epoxy resin.

[0066] Further, in step 1), the amount ratio of the aromatic amine epoxy resin curing agent, acetone and dimethylacetamide is (10-15) g:(2-8) mL:(10-15) mL.

[0067] The heating temperature of the solution is 50-80 DEG C, and the heating and stirring time is 20-40 min.

[0068] Further, in step 2), the preheating temperature of the epoxy resin is 50-80 DEG C, and the time is 4-8 h, so as to improve the flowability of the epoxy resin and remove water.

[0069] The heating and stirring temperature is 60-120 DEG C, and the stirring time is 10-60 min, which depends on the reactivity of the curing agent and the solvent content, so that the solvent is completely volatilized, and the vacuum degree is 1-10 mbar.

[0070] Further, in step 3), the degassing treatment refers to keeping the epoxy resin mixture and the filler at a vacuum degree of 1-10 mbar and a temperature of 60-120℃ for 30-120 min, so as to ensure that the pouring material has a viscosity of 6000-12000 mPa·s.

[0071] The weight ratio of the aromatic amine epoxy resin curing agent, the epoxy resin monomer, and the filler is (5-30):(10-40):(30-60); the heating temperature of the heating and stirring is 60-120℃, and the stirring time is 10-30 min.

[0072] Further, in step 4), the mold needs to be sprayed with a release agent in advance, and then heated to 100℃.

[0073] The degassing treatment is performed at a vacuum degree of 1-10 mbar and a temperature of 60-120℃ for 30-60 min.

[0074] The preparation method of the insulating epoxy resin disclosed in the present application uses the aromatic amine epoxy resin curing agent obtained by the above design method for preparation, and the use of mixed solvents helps the aromatic amine epoxy resin curing agent to be better dissolved, and the heating and stirring ensures that the curing agent is completely dissolved in the solvent, providing a uniform and stable curing agent solution for the 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, making it easier to mix with the curing agent solution. Continuous vacuuming and mixing under heating and stirring conditions help to remove bubbles and volatile substances from the mixture, improving the uniformity and density of the pouring material. Adding fillers and heating and stirring again can further improve the performance of the pouring material, such as mechanical strength, heat resistance, etc. The first degassing treatment helps to further remove gas from the pouring material, reducing pores and defects in the final product. Preheating the mold helps the pouring material to better fill the mold, reducing stress caused by temperature differences. The second degassing treatment further ensures that the gas in the pouring material is removed, improving the density and insulation performance of the product. The curing process allows the pouring material to form a stable chemical structure, giving the final product the required mechanical strength and electrical performance. After natural cooling to room temperature, the mold is demolded, which helps to reduce product deformation or cracking caused by rapid temperature changes.

[0075] The present application also discloses an insulating epoxy resin prepared by the above preparation method. By introducing a rigid aromatic structure into the epoxy crosslinking backbone, the thermal stability of the epoxy resin is significantly improved, allowing it to maintain insulation performance for a long time in high temperature environments. The use of two types of functional bridge bond functional groups to construct carrier traps effectively improves the electrical performance of the epoxy resin, especially the resistance and breakdown strength, allowing it to 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 application prospect in direct current GIS / GIL and other high-voltage electrical equipment.

[0076] The raw materials used in the embodiments of the present application are as follows:

[0077] Bisphenol A epoxy resin (DGEBA, WSR618 E51, epoxy value: 0.51 eq. / 100 g) was provided by Nantong Xingchen Synthetic Materials Co., Ltd., China.

[0078] 4,4'-diaminodiphenyl methane (DDM), 4,4'-diaminobenzophenone (DBP) and 2,2-bis(4-aminophenyl) hexafluoropropane (6FDAM) were provided by Shanghai McLean Biotechnology Co., Ltd., China.

[0079] Methyltetrahydrophthalic anhydride (MTHPA), 2,4,6-trimethylphenol, acetone and N,N-dimethylacetamide (DMAc) were provided by Sigma-Aldrich, USA.

[0080] Example 1

[0081] A method for preparing an insulating epoxy resin, comprising the following steps:

[0082] In this embodiment 1, 4,4'-diaminobenzophenone (DBP) containing two benzene ring structures and a strong electron-withdrawing group -C=O was used as an aromatic amine epoxy resin curing agent, and the functional bridge was at the 1,4 substitution position on the benzene ring (see formula 3). A method for preparing an insulating epoxy resin was provided, comprising the following steps:

[0083] 1) 10 g of DBP was dissolved in 2 mL of acetone and 10 mL of dimethylacetamide, heated to 50°C, and heated and stirred for 20 min to make DBP completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution;

[0084] 2) The epoxy resin was preheated at 60°C in an oven for 5 h, then the above-mentioned aromatic amine epoxy resin curing agent solution was mixed with 10 g of epoxy resin, and heated and stirred in a beaker with continuous vacuum, the heating temperature was 70°C, and the stirring time was 30 min; then 30 g of alumina filler was added to the mixture, and heated and stirred at 60°C for 30 min, and degassed at 60°C under a vacuum degree of 1 mbar for 30 min, to obtain a casting material;

[0085] 3) The above-mentioned casting material was heated to 120°C, and at the same time the mold was preheated at 100°C after spraying a release agent, and the casting material was poured into the mold, and degassed at 100°C under a vacuum degree of 10 mbar for 60 min;

[0086] 4) Then the ambient temperature is raised to 140°C for 60 min, and then to 180°C for 120 min, and then to 200°C for 60 min. Then, stop heating, and the furnace is naturally cooled to room temperature, and the mold is demolded to obtain an insulating epoxy resin, which is named EP-DBP.

[0087] Example 2

[0088] A method for preparing an insulating epoxy resin comprises the following steps:

[0089] In this example 2, 4,4'-diaminodiphenyl sulfone (DDS) containing two benzene ring structures and strong electron-withdrawing group -SO2 is used as an aromatic amine epoxy resin curing agent (see formula 2). The method for preparing an insulating epoxy resin comprises the following steps:

[0090] 1) 30 g of DDS is dissolved in 5 mL of acetone and 12 mL of dimethylacetamide, heated to 60°C, and heated and stirred for 30 min to make DDS completely dissolved to obtain an aromatic amine epoxy resin curing agent solution;

[0091] 2) The epoxy resin is preheated at 80°C in an oven for 4 h, and then the above-mentioned aromatic amine epoxy resin curing agent solution is mixed with 20 g of epoxy resin, and heated and stirred in a beaker with continuous vacuum, the heating temperature is 60°C, and the stirring time is 30 min. Then 30 g of alumina filler is added to the mixture, and heated and stirred at 60°C for 30 min, and degassed at 80°C for 60 min under a vacuum of 5 mbar to obtain a casting material;

[0092] 3) The above-mentioned casting material is heated to 130°C, and the mold is preheated at 100°C after being sprayed with a release agent, and the casting material is poured into the mold, and degassed at 100°C for 60 min under a vacuum of 5 mbar;

[0093] 4) Then the ambient temperature is raised to 120°C for 60 min, and then to 150°C for 180 min, and then to 190°C for 180 min. Then, stop heating, and the furnace is naturally cooled to room temperature, and the mold is demolded to obtain an insulating epoxy resin, which is named EP-DDS.

[0094] Example 3

[0095] A method for preparing an insulating epoxy resin comprises the following steps:

[0096] This embodiment 3 uses 2,2-bis(4-aminophenyl)propane (DAM) containing two benzene ring structures and a large steric hindering group -C2H6 as the aromatic amine epoxy resin curing agent (see formula 3), and provides a preparation method for preparing an insulating epoxy resin, which comprises the following steps:

[0097] 1) 12 g of DAM was dissolved in 6 mL of acetone and 14 mL of dimethylacetamide, heated to 60°C, and heated and stirred for 25 min to make DAM completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution;

[0098] 2) The epoxy resin was preheated at 50°C in an oven for 8 h, then the above-mentioned aromatic amine epoxy resin curing agent solution was mixed with 35 g of epoxy resin, and heating and stirring was carried out in a beaker under continuous vacuum, the heating temperature was 80°C, and the stirring time was 20 min; then 45 g of alumina filler was added to the mixture, and heating and stirring was carried out at 60°C for 10 min, and degassing treatment was carried out at 90°C for 45 min under a vacuum degree of 3 mbar, to obtain a casting material;

[0099] 3) The above-mentioned obtained casting material was heated to 115°C, and at the same time, the mold was preheated at 100°C after being sprayed with a release agent, and the casting material was poured into the mold, and degassing treatment was carried out at 90°C for 60 min under a vacuum degree of 5 mbar;

[0100] 4) Then the ambient temperature was raised to 130°C for 60 min, and held for 90 min; then raised to 150°C for 100 min, and held for 120 min; then raised to 210°C for 120 min, and held for 120 min; then, the heating was stopped, and the furnace was naturally cooled to room temperature, demolded, to obtain an insulating epoxy resin, named EP-DAM.

[0101] Embodiment 4

[0102] A preparation method of an insulating epoxy resin, comprising the following steps:

[0103] This embodiment 4 uses 2,2-bis(4-aminophenyl)hexafluoropropane (6FDAM) containing two benzene ring structures and a large volume bridge -C2F6 as the aromatic amine epoxy resin curing agent, and the functional bridge is at the 1,4 substitution position on the benzene ring (see formula 4), and provides a preparation method for preparing an insulating epoxy resin, which comprises the following steps:

[0104] 1) 15 g of 6FDAM was dissolved in 8 mL of acetone and 15 mL of dimethylacetamide, heated to 80°C, and heated and stirred for 40 min to make 6FDAM completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution;

[0105] 2) The epoxy resin was preheated in an oven at 50°C for 5h, then the above aromatic amine epoxy resin curing agent solution was mixed with 40g of epoxy resin, and heated stirring was carried out in a beaker with continuous vacuum extraction, the heating temperature was 120°C, and the stirring time was 60min; then 60g of alumina filler was added to the mixture, and heated stirring was carried out at 120°C for 30min, and degassing treatment was carried out at 120°C for 120min under a vacuum degree of 10mbar, to obtain a casting material;

[0106] 3) The above obtained casting material was heated to 140°C, and the mold was preheated at 100°C after being sprayed with a release agent, and the casting material was cast into the mold, and degassing treatment was carried out at 100°C for 60min under a vacuum degree of 1mbar;

[0107] 4) Then the ambient temperature was increased to 140°C for 60min, then increased to 180°C for 120min, then increased to 200°C for 60min, then the heating was stopped, and the furnace was naturally cooled to room temperature, demolding was carried out, to obtain an insulating epoxy resin, named EP-6FDAM.

[0108] Example 5

[0109] A method for preparing an insulating epoxy resin, comprising the following steps:

[0110] This example 5 uses 1,1-bis(4-aminophenyl)cyclohexane (CHA) containing two benzene ring structures and a large steric hindering group -C6H 12 as an aromatic amine epoxy resin curing agent (see formula 5), and provides a method for preparing an insulating epoxy resin, comprising the following steps:

[0111] 1) 10g of CHA was dissolved in 7mL of acetone and 13mL of dimethylacetamide, heated to 75°C, and heated stirring was carried out for 25min, so that the CHA was completely dissolved, to obtain an aromatic amine epoxy resin curing agent solution;

[0112] 2) The epoxy resin was preheated in an oven at 67°C for 5h, then the above aromatic amine epoxy resin curing agent solution was mixed with 28g of epoxy resin, and heated stirring was carried out in a beaker with continuous vacuum extraction, the heating temperature was 110°C, and the stirring time was 40min; then 50g of alumina filler was added to the mixture, and heated stirring was carried out at 110°C for 30min, and degassing treatment was carried out at 90°C for 70min under a vacuum degree of 8mbar, to obtain a casting material;

[0113] 3) The obtained casting material was heated to 110°C, and the mold was preheated at 100°C after spraying the mold release agent. The casting material was cast into the mold, and degassing was performed at 110°C for 60 min under a vacuum of 1 mbar;

[0114] 4) The ambient temperature was then increased to 140°C over 60 min, and held for 120 min. Then, the temperature was increased to 180°C over 120 min, and held for 300 min. Then, the temperature was increased to 210°C over 120 min, and held for 180 min. Then, the heating was stopped, and the mold was naturally cooled to room temperature. The insulation epoxy resin was obtained, and was named EP-CHA.

[0115] Comparative Example 1:

[0116] A method for preparing an insulation epoxy resin, comprising the following steps:

[0117] Comparative Example 1 used 4,4'-diaminodiphenyl methane (DDM) containing two benzene ring structures as a curing agent, and the two benzene rings were directly connected by a methylene group. The method for preparing the prepared epoxy resin sample included the following steps:

[0118] 1) 10 g of DDM was dissolved in 2 mL of acetone and 10 mL of dimethylacetamide, heated to 60°C, and heated and stirred for 20 min to completely dissolve the DDM;

[0119] 2) The epoxy resin was preheated in an oven at 60°C for 5 h. Then, the above-mentioned aromatic amine epoxy resin curing agent solution was mixed with 15 g of epoxy resin, and heated and stirred in a beaker with continuous vacuum extraction. The heating temperature was 70°C, and the stirring time was 30 min. Then, 40 g of alumina filler was added to the mixture, and heated and stirred at 60°C for 30 min to obtain a casting material;

[0120] 3) The obtained casting material was heated to 100°C, and the mold was preheated at 100°C after spraying the mold release agent. The casting material was cast into the mold, and degassing was performed at 100°C for 60 min under a vacuum of 10 mbar;

[0121] 4) The ambient temperature was then increased to 140°C over 60 min, and held for 60 min. Then, the temperature was increased to 180°C over 60 min, and held for 120 min. Then, the temperature was increased to 200°C over 60 min, and held for 60 min. Then, the heating was stopped, and the mold was naturally cooled to room temperature. The insulation epoxy resin was obtained, and was named EP-DDM.

[0122] The curing agent used in Comparative Example 1 herein is a traditional commonly used aniline curing agent, which is directly connected by a methylene group at the 1,4 substitution position between two benzene rings, so as to form a charge transmission channel between the benzene ring structures in the molecular chain and between the molecular chains, so that the electrical insulation performance is weak. Therefore, as a comparison, we verify the influence of the introduction of the functional bridge bond on the electrothermal performance of the aniline cured epoxy resin.

[0123] Referring to Figure 1 The Fourier infrared spectrum of the insulating epoxy resin obtained in Example 1-5 and Comparative Example 1 is shown in the following figure. For the insulating epoxy resin prepared in Example 1-5 and Comparative Example 1, Fourier infrared test is carried out, and the test results are compared and analyzed, and the analysis results are as shown in the following figure. Figure 1 As can be seen from the figure, the crosslinking reaction of the epoxy resin and the curing agent is ensured to be complete by the method provided in Example 1-5 and Comparative Example 1.

[0124] Referring to Figure 2 The differential scanning calorimetry result graph of the insulating epoxy resin obtained in Example 1-5 and Comparative Example 1 is shown in the following figure. In order to analyze the influence of the proposed method on the thermal stability, the differential scanning calorimeter is used to measure at 10 ℃ / min under nitrogen atmosphere, and the test results are compared and analyzed, and the analysis results are as shown in the following figure. Figure 2 As can be seen from the figure, the introduction of benzene ring leads to the increase of the glass transition temperature of the epoxy resin, which is much higher than the glass transition temperature (about 120℃) of the traditional acid anhydride cured epoxy resin, which indicates that the thermal stability of the epoxy resin is improved due to the introduction of the multi-benzene ring curing agent.

[0125] Referring to Figure 3 The high temperature direct current breakdown strength and high temperature volume resistivity result comparison graph of the insulating epoxy resin obtained in Example 1-5 and Comparative Example 1 is shown in the following figure. In order to verify the influence of the proposed method on the high temperature electrical performance of the epoxy resin, the high temperature electrical performance test is carried out on the insulating epoxy resin obtained in Example 1-5 and Comparative Example 1. The direct current breakdown strength test result and the direct current volume resistivity test result under the condition of 120℃ are as shown in the following figure. Figure 3 As can be seen from the figure, the aromatic amine epoxy resin curing agent containing strong electron-withdrawing bridge bond and containing bulky bridge bond can maintain high electrical performance at high temperature. For EP-6FDAM, the breakdown strength at 120℃ reaches 393.83 kV / mm, and the volume resistivity reaches 2.91×10 14 Ω·cm, which are much higher than the performance of the traditional acid anhydride cured epoxy resin.

[0126] The application proposes a strategy of developing high thermal stability and high electrical resistance performance of electrical epoxy resin formula by using multi-aromatic structure and functional bridge. The core is to use multi-aromatic diamine as the curing agent component of epoxy resin, to introduce rigid aromatic structure into the epoxy main chain to enhance its thermal stability and improve the glass transition temperature. In addition, by introducing functional bridge between benzene rings as a means to break the benzene ring conjugate structure and improve electrical performance; the introduced functional bridge is divided into two categories, the first category is a strong electron-withdrawing group, which builds 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 benzene rings to block the charge transfer between different epoxy molecular chains. By designing the molecular structure of the multi-aniline functional bridge amine curing agent, on the one hand, the rigid structure is introduced into the epoxy crosslinking main chain to improve the thermal stability, and on the other hand, the two types of functional bridge functional groups are used to build carrier traps to improve the electrical performance. The formed epoxy resin material with high thermal stability and high electrical strength helps to solve the electrical performance of key insulation parts in DC GIS / GIL under the action of high temperature gradient and high electric field.

[0127] The above is only to illustrate the technical idea of the application, and cannot limit the protection scope of the application. Any modification made according to the technical idea of the application on the basis of the technical scheme falls within the protection scope of the claims of the application.

Claims

1. A method for preparing an insulating epoxy resin, characterized by, The method comprises the following steps: 1) dissolving the aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, and performing first heating and stirring until complete dissolution to obtain an aromatic amine epoxy resin curing agent solution; the aromatic amine epoxy resin curing agent is any one of 4,4'-diaminobenzophenone, 4,4'-diaminodiphenyl sulfone, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-aminophenyl)hexafluoropropane and 1,1-bis(4-aminophenyl)cyclohexane; 2) adding the aromatic amine epoxy resin curing agent solution obtained in step 1) into preheated epoxy resin monomers, and performing second heating and stirring under continuous vacuum; then adding fillers, performing third heating and stirring, and performing first degassing treatment to obtain a pouring material; the epoxy resin monomers are bisphenol A epoxy resin; and the fillers are aluminum oxide; 3) pouring the pouring material obtained in step 2) into a preheated mold, performing second degassing treatment, naturally cooling to room temperature after curing, demolding, and obtaining an insulating epoxy resin.

2. The method for preparing the insulating epoxy resin according to claim 1, characterized in that, In step 1), the weight ratio of the aromatic amine epoxy resin curing agent, acetone and 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 20-40 min.

3. The method for preparing the insulating epoxy resin according to claim 1, characterized in that, the weight ratio of the aromatic amine epoxy resin curing agent, epoxy resin monomers and fillers is (5-30):(10-40):(30-60); the preheating temperature of the epoxy resin monomers is 50-80℃, and the preheating time is 4-8 h; the heating temperature of the second heating and stirring is 60-120℃, and the stirring time is 10-60 min; the heating temperature of the third heating and stirring is 60-120℃, and the stirring time is 10-30 min; the first degassing treatment is performed at a vacuum degree of 1-10 mbar, and the temperature is kept at 60-120℃ for 30-120 min.

4. The method for preparing the insulating epoxy resin according to claim 1, characterized in that, In step 3), the mold is pre-sprayed with a release agent and heated to 100℃; the second degassing treatment is performed at a vacuum degree of 1-10 mbar, and the temperature is kept at 60-120℃ for 30-60 min; the curing conditions are as follows: the temperature is raised to 120-140℃, and kept for 60-180 min; then the temperature is raised to 150-180℃ over 60-120 min, and kept for 120-300 min; then the temperature is raised to 190-210℃ over 60-120 min, and kept for 60-180 min.

5. An insulating epoxy resin, characterized by, The method is prepared by any one of claims 1-4.

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