Aromatic amine epoxy resin curing agent, insulating epoxy resin and preparation method therefor

Abstract

The present invention belongs to the technical field of insulation, and discloses an aromatic amine epoxy resin curing agent, an insulating epoxy resin and a preparation method therefor. The curing agent is designed to include at least two benzene ring structures connected via a functional bridging linkage, with an amino functional group arranged at each end of the designed structure, and no strong electron withdrawing substituent provided at the ortho positions of the designed amino functional groups, thereby yielding the aromatic amine epoxy resin curing agent, wherein the functional bridging linkage is located at the 1,4 or 1,3 positions of the benzene ring structures. A polyaromatic diamine is used as a curing agent component for an epoxy resin, and a rigid aromatic structure is introduced into an epoxy backbone to enhance the thermal stability thereof and increase the glass transition temperature thereof; and a functional bridging linkage is also introduced between benzene rings to break the conjugation structure of the benzene ring and improve the electrical performance. An insulating epoxy resin for a high-voltage direct current with a high thermal stability and a high resistivity can be prepared. The present invention helps to solve the electrical performance problems of a key insulating member in a direct current GIS / GIL under a high temperature gradient and a high electric field.

Description

An aromatic amine epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. Technical Field

[0001] This invention belongs to the field of insulation technology, specifically relating to an aromatic amine epoxy resin curing agent, an insulating epoxy resin, and a method for preparing the same. Background Technology

[0002] With the large-scale development of offshore wind power and high-altitude hydropower, DC GIS (Gas Insulated Switchgear) / GIL (Gas Insulated Transmission Lines) have become the main equipment for large-scale clean energy transmission due to their advantages such as small footprint, high reliability, and minimal environmental impact. Under DC voltage, the internal electric field of the material exhibits a resistive distribution, unlike the resistive distribution of the internal electric field under traditional DC voltage. This easily leads to the accumulation of surface charges on the surface of the insulating material, inducing surface flashover faults. Since the conductor temperature is close to the glass transition temperature of the epoxy material, and the resistivity of epoxy material decreases significantly with increasing temperature, a radial temperature gradient forms inside the insulator. The location of the maximum electric field shifts towards the grounded outer shell, resulting in a decrease in the effective insulation distance, further distortion of the surface electric field, and a significant drop in the surface flashover voltage.

[0003] Currently, researchers mainly propose using micron- and nanoparticle doping to modify materials and enhance the electrical properties of epoxy composites. However, due to the large specific surface area of ​​nanoparticles, they are prone to agglomeration and cannot be uniformly dispersed within the material, thus failing to meet the requirements of large-scale industrial applications. Furthermore, the glass transition temperature of commercial epoxy resin matrix materials used for electrical insulation is only around 120°C, further limiting the electrical performance of epoxy materials under high temperature gradients and high electric fields. Effective solutions to these technical problems have not yet been proposed, making it difficult to meet the design requirements of critical insulation components in DC GIS / GIL.

[0004] In response to the problems of nanoparticle agglomeration, uneven dispersion, and low glass transition temperature of epoxy resin matrix materials during the modification process of epoxy composites, there is an urgent need to find a new epoxy resin with high thermal stability and high resistivity for high voltage DC insulation and its preparation method, so as to meet the design requirements of key insulation components in DC GIS / GIL under high temperature gradient and high electric field conditions. Technical issues

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide an aromatic amine epoxy resin curing agent, an insulating epoxy resin and a method for preparing the same, so as to solve the technical problem of poor electrical performance of key insulating components in DC GIS / GIL under high temperature gradient and high electric field. Technical solutions

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] In a first aspect, the present invention provides an aromatic amine epoxy resin curing agent, comprising:

[0008] The design structure consists of at least two benzene rings connected by functional bridge bonds; an amino functional group is set at each end of the design structure; no strong electron-withdrawing substituents are set at the adjacent positions of the amino functional groups.

[0009] The functional bridging bond is located at the 1,4 substitution site or the 1,3 substitution site of the benzene ring structure.

[0010] Furthermore, the functional bridging bond described in this invention is a strong electron-withdrawing group or a large steric hindrance group.

[0011] Furthermore, the strong electron-withdrawing group described in this invention is -C=O or -SO2.

[0012] Furthermore, the large steric hindrance group described in this invention is -C2H6, -C2F6, or -C6H. 12 .

[0013] Secondly, the present invention provides a method for preparing an insulating epoxy resin, comprising the following steps:

[0014] 1) Dissolve the above aromatic amine epoxy resin curing agent in a mixed solvent of acetone and dimethylacetamide, and heat and stir for the first time until completely dissolved to obtain an aromatic amine epoxy resin curing agent solution;

[0015] 2) Add the aromatic amine epoxy resin curing agent solution obtained in step 1) to the preheated epoxy resin monomer, and perform a second heating and stirring under continuous vacuum conditions; then add filler, perform a third heating and stirring, and perform a first degassing treatment to obtain the casting material.

[0016] 3) Pour the casting material obtained in step 2) into a preheated mold, perform a second degassing treatment, and after curing, allow it to cool naturally to room temperature before demolding to obtain insulating epoxy resin.

[0017] Furthermore, in step 1) of the present invention, the ratio of aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15)g: (2-8)mL: (10-15)mL.

[0018] The heating temperature for the first heating and stirring is 50~80℃, and the stirring time is 20~40min.

[0019] Furthermore, the weight ratio of aromatic amine epoxy resin curing agent: epoxy resin monomer: filler in this invention is (5-30):(10-40):(30-60);

[0020] The preheating temperature of the epoxy resin monomer is 50~80℃, and the preheating time is 4~8h;

[0021] The heating temperature for the second heating and stirring is 60~120℃, and the stirring time is 10~60min;

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

[0023] The conditions for the first degassing treatment are: under a vacuum of 1~10 mbar, at a temperature and pressure of 60~120℃ for 30~120 min.

[0024] Furthermore, in step 3) of the present invention, the method for obtaining the preheated mold includes: spraying a release agent in advance and heating it to 100°C;

[0025] The conditions for the second degassing treatment are: under a vacuum of 1-10 mbar, at a temperature and pressure of 60-120°C for 30-60 minutes.

[0026] The curing conditions are as follows: heat to 120~140℃ and hold for 60~180 min; then heat to 150~180℃ for 60~120 min and hold for 120~300 min; then heat to 190~210℃ for 60~120 min and hold for 60~180 min.

[0027] Thirdly, the present invention provides an insulating epoxy resin, which is prepared by the above-described preparation method. Beneficial effects

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] This invention discloses an aromatic amine epoxy resin curing agent, comprising: designing at least two benzene ring structures to introduce rigid aromatic structures into the epoxy backbone to enhance its thermal stability and increase its glass transition temperature; enabling it to maintain its performance at higher temperatures, thereby broadening the application range of epoxy resin; introducing functional bridging bonds between benzene rings as a means to break the conjugated structure of benzene rings, effectively improving the electrical properties of epoxy resin, especially the introduction of strong electron-withdrawing groups and large steric hindrance groups, which respectively block charge transport within and between epoxy molecular chains by constructing electron traps and hindering π-π stacking between benzene rings, significantly improving electrical resistance. An amino functional group is set at each end of the designed structure; the amino functional group serves as a site for cross-linking reaction with the epoxy functional groups in the epoxy resin monomer. The presence of an amino functional group at each end ensures sufficient reaction between the curing agent and the epoxy resin, forming a uniform cross-linked network. Because strong electron-withdrawing groups significantly reduce reactivity, no strong electron-withdrawing substituents are placed at the ortho positions of the designed amino functional groups to ensure high reactivity of the amine during the crosslinking reaction, guaranteeing complete internal curing of the material during the curing of large insulating components. Functional bridging bonds are placed at the 1,4 or 1,3 substitution positions of the benzene ring structure; 1,2 substitution positions may result in too low reactivity, making subsequent curing reactions difficult. Appropriate substitution positions ensure the main chain has a certain degree of freedom, allowing for axial rotation. The aromatic amine epoxy resin curing agent disclosed in this invention, starting from molecular structure design, systematically considers the need to improve thermal stability and electrical properties, providing scientific guidance for the development of high-performance epoxy resin curing agents. By adjusting the benzene ring structure, the type of functional bridging bonds, and the substitution positions, the performance of the curing agent can be flexibly controlled to adapt to different application requirements. It can be used to prepare epoxy resins for high thermal stability and high resistivity in high-voltage DC insulation. It helps to solve the electrical performance problems of key insulating components in DC GIS / GIL under high temperature gradients and high electric fields.

[0030] Furthermore, the introduced functional bridging groups are divided into two categories. The first category consists of strong electron-withdrawing groups, which construct electron traps between benzene ring structures to block charge transport within the epoxy molecular chain. These groups effectively absorb and fix electrons, thereby reducing the free movement of charges within the molecular chain. This is particularly important for electrical applications requiring high electrical resistance, such as key insulating components in DC GIS / GIL, which need to maintain stable electrical performance under high temperature gradients and high electric fields. The second category consists of large steric hindrance groups, which utilize their large volume to increase the intermolecular spacing, hindering the π-π stacking interaction between benzene rings and thus blocking charge transport between different epoxy molecular chains. This further enhances the electrical resistance of the epoxy resin and improves the overall stability and durability of the material by increasing the intermolecular spacing. On the one hand, a rigid structure is introduced into the epoxy crosslinking backbone to improve thermal stability; on the other hand, the two types of functional bridging groups are used to construct carrier traps, thereby improving electrical performance.

[0031] The aromatic amine epoxy resin curing agent of the present invention takes into account the reactivity with epoxy resin monomers, ensuring a smooth curing process and thus optimizing the processing performance of epoxy resin. It can enhance the thermal stability of epoxy resin, significantly improve its electrical resistance, and ensure a smooth curing process, thereby optimizing the processing performance of epoxy resin.

[0032] This invention also discloses a method for preparing insulating epoxy resin, using the aforementioned aromatic amine epoxy resin curing agent. The aromatic amine molecules in the curing agent contain benzene ring structures, giving the cured insulating epoxy resin excellent heat resistance, enabling it to withstand high-temperature environments without significant performance degradation. The aromatic amine epoxy resin curing agent allows 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 forms a hard surface with high strength and hardness, resulting in excellent performance under mechanical stress. The aromatic amines in the curing agent have high reactivity, reacting quickly with the epoxy resin and completing the curing process in a short time, improving production efficiency. The presence of the benzene ring structure not only improves heat resistance but also endows the aromatic amine epoxy resin curing agent with good oxidation resistance and stability, extending the product's service life. While maintaining high strength and hardness, it also possesses a certain degree of flexibility and adhesion, better adapting to complex application scenarios.

[0033] This invention also discloses an insulating epoxy resin prepared by the above-described method. By introducing a rigid aromatic structure into the epoxy crosslinking backbone, the thermal stability of the epoxy resin is significantly improved, enabling it to maintain its insulating properties for extended periods at high temperatures. The use of two types of functional bridging groups to construct carrier traps effectively enhances the electrical properties of the epoxy resin, particularly its resistivity and breakdown strength, allowing it to meet the insulation requirements of high-voltage electrical equipment. The high thermal stability and high electrical strength of this insulating epoxy resin make it a promising candidate for widespread application in high-voltage electrical equipment such as DC GIS / GIL systems. Attached Figure Description

[0034] Figure 1 shows the Fourier transform infrared spectra of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention.

[0035] Figure 2 shows the differential scanning calorimetry results of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention.

[0036] Figure 3 is a comparison of the high-temperature DC breakdown strength and high-temperature volume resistivity of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention. Embodiments of the present invention

[0037] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0038] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0039] The present invention will now be described in further detail with reference to the accompanying drawings:

[0040] This invention discloses an aromatic amine epoxy resin curing agent, which may include:

[0041] 1) The curing agent contains two or more benzene ring structures, which are connected by functional bridging bonds to form the designed structure;

[0042] 2) The above-mentioned structure contains an amino functional group at each end, which serves as a site for cross-linking reaction with the epoxy functional group in the epoxy resin monomer. This ensures that the high thermal stability of the benzene ring structure can serve as the main body of the epoxy cross-linking structure, thereby improving the thermal stability of the material.

[0043] 3) No strong electron-withdrawing substituents are placed at the ortho position of the above-mentioned amino functional groups to ensure the high reactivity of the amine during the crosslinking reaction and to ensure complete internal curing of the material during the curing of large insulating parts.

[0044] 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 rotate axially.

[0045] It should be noted that functional bridging bonds can be divided into two categories. The first type consists of strong electron-withdrawing groups that block the transport of π electrons between benzene rings within the chain. The second type consists of sterically hindered groups that increase the intermolecular distance and block electron transport between different chains. Strong electron-withdrawing groups and sterically hindered groups are located at the para-position of the amino group.

[0046] It should be noted that strong electron-withdrawing groups, also known as electron-modulating groups, are bridging groups that can regulate the electronic properties of a molecule by altering the electron density on the benzene ring. These groups affect the charge transport capability of the molecule, and their mechanism of action includes a combination of electronegativity, inductive effects, and resonance effects. For example, groups such as -O-, -S-, carbonyl (-C=O), and sulfonyl (-SO2) can reduce the electron density of the adjacent benzene ring through inductive or resonance effects, thereby suppressing nonlocal electron transport and improving the insulation properties of the material. In semi-quantitative analysis, the influence of these groups on the molecular electronic structure and properties can be evaluated using theoretical calculations such as Mulliken charge distribution and electrostatic potential distribution, combined with experimentally measured electrical properties. The introduction of strong electron-withdrawing groups typically leads to a significant reduction in the electron density of the benzene ring region, which helps improve the insulation properties of epoxy resins.

[0047] It should be noted that large sterically hindered groups refer to bridging groups that are relatively large and can significantly affect intermolecular packing and molecular chain conformation. These groups primarily influence the insulating properties of materials by altering the molecular packing pattern and free volume through steric hindrance. Examples include -C2H6, -C2F6, and -C6H. 10 The introduction of large-volume groups disrupts the close packing of molecular chains, increasing the proportion of free volume and the intermolecular distance. Molecular dynamics simulations and X-ray diffraction experiments have shown that the introduction of large sterically hindered groups significantly increases the proportion of free volume and the intermolecular distance of epoxy resins, thus improving the insulation properties of the material. Compared with electron-regulating groups, large sterically hindered groups have a more significant impact on the intermolecular distance, but the two may have overlapping functions in some cases (e.g., 6FDAM has both electron-withdrawing and steric-hinding effects).

[0048] The distinction between strong electron-withdrawing groups and sterically hindered groups is mainly based on their electronic and steric effects. However, in actual molecular design, some bridging groups may possess both functions simultaneously. For strong electron-withdrawing groups, semi-quantitative analysis can be performed through theoretical calculations (such as Mulliken charge distribution and electrostatic potential distribution) and experimental data. For sterically hindered groups, characterization is mainly achieved through molecular structural parameters (such as free volume and intermolecular distance).

[0049] Among them, the first type of functional bridging bond is a strong electron-withdrawing group, including but not limited to -C=O or -SO2, such as one or two of Formulas 1 to 2:

[0050] Formula 1:

[0051] ;

[0052] Formula 2:

[0053] .

[0054] The second type of functional bridging bond consists of sterically hindered groups, including but not limited to -C2H6, -C2F6, or -C6H. 12 Etc., such as one or more of Equations 3 to 5:

[0055] Formula 3:

[0056] ;

[0057] Formula 4:

[0058] ;

[0059] Formula 5:

[0060] .

[0061] This invention discloses an aromatic amine epoxy resin curing agent, comprising: designing at least two benzene ring structures to introduce rigid aromatic structures into the epoxy backbone to enhance its thermal stability and increase its glass transition temperature; the benzene ring structures can provide sufficient rigidity and stability, enabling the cured epoxy resin to have better mechanical properties and thermal stability. Multiple benzene ring structures can enhance the intermolecular forces of the curing agent, increase the crosslinking density of the epoxy resin, thereby improving its hardness, strength, and heat resistance. The benzene ring structures are connected by functional bridging bonds; by introducing functional bridging bonds between benzene rings as a means to break the conjugated structure of the benzene rings and improve electrical properties, the selection and design of functional bridging bonds are crucial to the performance of the curing agent. These bonds connect different benzene ring structures, affecting the flexibility, reactivity, and final performance of the epoxy resin. By selecting appropriate functional bridging bonds, the chemical properties of the curing agent, such as reaction rate and curing temperature, can be controlled, thereby optimizing the processing performance and final application performance of the epoxy resin. An amino functional group is placed at each end of the designed structure. These amino functional groups serve as sites for cross-linking reactions with the epoxy functional groups in the epoxy resin monomer. The presence of an amino functional group at each end ensures sufficient reaction between the curing agent and the epoxy resin, forming a uniform cross-linked network. This results in highly reactive curing agents that react rapidly and completely with the epoxy resin to form a dense cross-linked structure, thereby improving the mechanical properties and chemical resistance of the epoxy resin. Strong electron-withdrawing substituents are not placed at the adjacent positions of the designed amino functional groups. The presence of strong electron-withdrawing substituents reduces the reactivity of the amino functional groups, thus affecting the reaction efficiency between the curing agent and the epoxy resin. Therefore, such substituents are avoided at the adjacent positions of the amino functional groups during the design process. Ensuring high reactivity of the amino functional groups allows the curing agent to react fully and rapidly with the epoxy resin, forming a high-quality cross-linked network, thereby improving the overall performance of the epoxy resin. Appropriate substitution positions can optimize the molecular configuration of the curing agent, improving its reactivity and stability. Further adjustments to the chemical and physical properties of the curing agent, such as solubility and viscosity, allow for better adaptation to different epoxy resin systems and processing conditions. This is used to prepare epoxy resins for high-voltage DC insulation with high thermal stability and high resistivity. It helps address the electrical performance issues of critical insulation components in DC GIS / GIL under high temperature gradients and high electric fields.

[0062] The aromatic amine epoxy resin curing agent of this invention is designed with reactivity with epoxy resin monomers in mind, ensuring a smooth curing process and thus optimizing the processing performance of the epoxy resin. It enhances the thermal stability of the epoxy resin, significantly improves its electrical resistance, and ensures a smooth curing process, thereby optimizing the processing performance of the epoxy resin.

[0063] This invention also discloses a method for preparing an insulating epoxy resin, comprising the following steps:

[0064] 1) Dissolution of aromatic amine epoxy resin curing agent: The above aromatic amine epoxy resin curing agent is dissolved in a mixed solvent of acetone and dimethylacetamide, and the mixture is heated and stirred for the first time to completely dissolve the aromatic amine epoxy resin curing agent in the solvent, thereby obtaining an aromatic amine epoxy resin curing agent solution.

[0065] 2) Dispersion of aromatic amine epoxy resin curing agent: The above aromatic amine epoxy resin curing agent solution is added to the preheated epoxy resin monomer, and then heated and stirred for a second time under continuous vacuum conditions.

[0066] 3) Casting: Add filler (usually Al2O3 particles) to the above mixture, heat and stir for the third time, and perform the first degassing treatment to obtain the casting material;

[0067] 4) Curing: Pour the casting material obtained in step 3) into a preheated mold and perform a second degassing treatment. Then, raise the curing temperature to 120~140℃ and hold for 60~180min; then raise the temperature to 150~180℃ after 60~120min and hold for 120~300min; then raise the temperature to 190~210℃ after 60~120min and hold for 60~180min; then, stop heating and allow it to cool naturally to room temperature in the furnace. Demold to obtain insulating epoxy resin.

[0068] In some embodiments of this application, in step 1), the ratio of aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15) g: (2-8) mL: (10-15) mL. This ratio ensures that the aromatic amine epoxy resin curing agent is completely dissolved in the solvent, guaranteeing the uniform dispersion of the aromatic amine epoxy resin curing agent in the epoxy resin, which is beneficial to improving the overall performance of the cured epoxy resin.

[0069] In some embodiments of this application, the heating temperature for the first heating and stirring is 50~80°C, and the heating and stirring time is 20~40 min.

[0070] In some embodiments of this application, in step 2), the preheating temperature of the epoxy resin is 50~80°C and the time is 4~8h, which improves the fluidity of the epoxy resin and removes moisture.

[0071] In some embodiments of this application, the temperature of the second and third heating and stirring is 60~120°C, and the stirring time is 10~60 min, depending on the reactivity of the curing agent and the solvent content, so that the solvent evaporates completely, and the vacuum degree is 1~10 mbar.

[0072] It should be noted that the heating temperature of the first heating and stirring is slightly lower than that of the second and third heating and stirring. This can prevent processing difficulties caused by increased viscosity of the mixture and can also allow for rapid curing during the subsequent curing process, preventing filler sedimentation.

[0073] In some embodiments of this application, in step 3), the first degassing treatment refers to keeping the epoxy resin mixture and filler under vacuum of 1~10 mbar and temperature of 60~120℃ for 30~120 min to ensure that the viscosity of the castable is 6000~12000 mPa·s.

[0074] In some embodiments of this application, 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 10-30 min. This ratio of epoxy resin to aromatic amine epoxy resin curing agent ensures complete reaction between the two, which is beneficial for improving the overall performance of the cured epoxy resin. A high proportion of filler can enhance the mechanical strength of the cured epoxy resin.

[0075] In some embodiments of this application, in step 4), the mold needs to be sprayed with a release agent in advance and then heated to 100°C.

[0076] The degassing conditions are: under a vacuum of 1-10 mbar, at 60-120℃ and pressure for 30-60 minutes.

[0077] This invention discloses a method for preparing an insulating epoxy resin. The method uses the aforementioned aromatic amine epoxy resin curing agent. Using a mixed solvent helps the aromatic amine epoxy resin curing agent dissolve better, while heating and stirring ensure the curing agent is completely dissolved in the solvent, providing a uniform and stable curing agent solution for subsequent steps, which is beneficial for improving the quality and performance of the final product. Preheating the epoxy resin monomer helps reduce its viscosity, facilitating mixing with the curing agent solution. Continuous vacuuming and mixing under heating and stirring conditions helps eliminate air bubbles and volatiles in the mixture, improving the uniformity and density of the castable. Adding filler and reheating and stirring further improves the properties of the castable, such as mechanical strength and heat resistance. The first degassing treatment helps further remove gas from the castable, reducing porosity and defects in the final product. Preheating the mold helps the castable fill the mold better, reducing stress caused by temperature differences. The second degassing treatment further ensures that gas is removed from the castable, improving the density and insulation performance of the product. The curing process forms a stable chemical structure in the castable, 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.

[0078] This invention also discloses an insulating epoxy resin prepared by the above-described method. By introducing a rigid aromatic structure into the epoxy crosslinking backbone, the thermal stability of the epoxy resin is significantly improved, enabling it to maintain its insulating properties for extended periods at high temperatures. The use of two types of functional bridging groups to construct carrier traps effectively enhances the electrical properties of the epoxy resin, particularly its resistivity and breakdown strength, allowing it to meet the insulation requirements of high-voltage electrical equipment. The high thermal stability and high electrical strength of this insulating epoxy resin make it a promising candidate for widespread application in high-voltage electrical equipment such as DC GIS / GIL systems.

[0079] The present application will be further illustrated below through several embodiments and comparative examples. In the following embodiments and comparative examples, the raw materials used are as follows:

[0080] Bisphenol A epoxy resin (DGEBA, WSR618 E51, epoxy value: 0.51 eq. / 100 g) was supplied by Nantong Xingchen Synthetic Materials Co., Ltd., China.

[0081] 4,4'-Diaminodiphenylmethane (DDM), 4,4'-Diaminobenzophenone (DBP) and 2,2-bis(4-aminophenyl)hexafluoropropane (6FDAM) were supplied by Shanghai Maclean Biotechnology Co., Ltd., China.

[0082] Methyltetrahydrophthalic anhydride (MTHPA), 2,4,6-trimethylphenol, acetone, and N,N-dimethylacetamide (DMAc) were supplied by Sigma-Aldrich, USA.

[0083] Example 1

[0084] A method for preparing an insulating epoxy resin includes the following steps:

[0085] Example 1 uses 4,4'-diaminobenzophenone (DBP), which contains two benzene rings and a strong electron-withdrawing group -C=O, as an aromatic amine epoxy resin curing agent. The functional bridging bond is located at the 1,4 substitution position on the benzene ring (see Formula 3). The method for preparing the insulating epoxy resin provided includes the following steps:

[0086] 1) Dissolve 10g DBP in 2mL acetone and 10mL dimethylacetamide, heat to 50℃, and stir for 20min to completely dissolve DBP, thus obtaining an aromatic amine epoxy resin curing agent solution.

[0087] 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 beaker under continuous vacuum at 70°C for 30 minutes. Subsequently, add 30g of alumina filler to the mixture, heat and stir at 60°C for 30 minutes, and degas at 60°C under a vacuum of 1mbar for 30 minutes to obtain the casting material.

[0088] 3) Heat the above-obtained casting material to 120°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 10 mbar and at 100°C.

[0089] 4) The ambient temperature was then raised to 140℃ over 60 minutes and held for 60 minutes; then raised to 180℃ over 60 minutes and held for 120 minutes; then raised to 200℃ over 60 minutes and held for 60 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-DBP (denoted as DBP in Figures 1 and 2).

[0090] Example 2

[0091] A method for preparing an insulating epoxy resin includes the following steps:

[0092] In this embodiment 2, 4,4'-diaminodiphenyl sulfone (DDS), which contains 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 for the provided insulating epoxy resin includes the following steps:

[0093] 1) Dissolve 30g of DDS in 5mL of acetone and 12mL of dimethylacetamide, heat to 60℃, and stir for 30min to completely dissolve the DDS, thus obtaining an aromatic amine epoxy resin curing agent solution.

[0094] 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 beaker under continuous vacuum at 60°C for 30 minutes. Subsequently, add 30g of alumina filler to the mixture, heat and stir at 60°C for 30 minutes, and degas at 80°C under a vacuum of 5mbar for 60 minutes to obtain the casting material.

[0095] 3) Heat the above-obtained casting material to 130°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 5 mbar and at 100°C.

[0096] 4) The ambient temperature was then raised to 120℃ over 60 minutes and held for 180 minutes; then raised to 150℃ over 120 minutes and held for 180 minutes; then raised to 190℃ over 60 minutes and held for 180 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-DDS (denoted as DDS in Figures 1 and 2).

[0097] Example 3

[0098] A method for preparing an insulating epoxy resin includes the following steps:

[0099] In this embodiment 3, 2,2-bis(4-aminophenyl)propane (DAM), which contains two benzene rings and a large sterically hindered group -C2H6, is used as an aromatic amine epoxy resin curing agent (see Formula 3). The method for preparing the insulating epoxy resin provided includes the following steps:

[0100] 1) Dissolve 12g DAM in 6mL acetone and 14mL dimethylacetamide, heat to 60℃, and stir for 25min to completely dissolve DAM, thus obtaining an aromatic amine epoxy resin curing agent solution.

[0101] 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 beaker under continuous vacuum at 80°C for 20 minutes. Subsequently, add 45g of alumina filler to the mixture, heat and stir at 60°C for 10 minutes, and degas at 90°C under a vacuum of 3mbar for 45 minutes to obtain the casting material.

[0102] 3) Heat the above-obtained casting material to 115°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 5 mbar and at 90°C.

[0103] 4) The ambient temperature was then raised to 130℃ over 60 minutes and held for 90 minutes; then raised to 150℃ over 100 minutes and held for 120 minutes; then raised to 210℃ over 120 minutes and held for 120 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-DAM (denoted as DAM in Figures 1 and 2).

[0104] Example 4

[0105] A method for preparing an insulating epoxy resin includes the following steps:

[0106] In this embodiment 4, 2,2-bis(4-aminophenyl)hexafluoropropane (6FDAM), containing two benzene rings and a large-volume bridging bond -C2F6, is used as an aromatic amine epoxy resin curing agent. The functional bridging bond is located at the 1,4 substitution positions on the benzene ring (see Formula 4). The method for preparing the insulating epoxy resin provided includes the following steps:

[0107] 1) Dissolve 15g of 6FDAM in 8mL of acetone and 15mL of dimethylacetamide, heat to 80℃, and stir for 40min to completely dissolve 6FDAM to obtain an aromatic amine epoxy resin curing agent solution.

[0108] 2) Preheat the epoxy resin in an oven at 50°C for 5 hours. Then mix the aromatic amine epoxy resin curing agent solution with 40g of epoxy resin and heat and stir in a beaker under continuous vacuum at 120°C for 60 minutes. Subsequently, add 60g of alumina filler to the mixture, heat and stir at 120°C for 30 minutes, and degas at 120°C under a vacuum of 10mbar for 120 minutes to obtain the casting material.

[0109] 3) Heat the above-obtained casting material to 140°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 1 mbar and at 100°C.

[0110] 4) The ambient temperature was then raised to 140℃ over 60 minutes and held for 60 minutes; then raised to 180℃ over 60 minutes and held for 120 minutes; then raised to 200℃ over 60 minutes and held for 60 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-6FDAM (referred to as 6FDAM in Figures 1 and 2).

[0111] Example 5

[0112] A method for preparing an insulating epoxy resin includes the following steps:

[0113] This embodiment 5 uses a structure containing two benzene rings and a large sterically hindered group -C6H. 12 Using 1,1-bis(4-aminophenyl)cyclohexane (CHA) as an aromatic amine epoxy resin curing agent (see Formula 5), ​​the method for preparing insulating epoxy resin includes the following steps:

[0114] 1) Dissolve 10g CHA in 7mL acetone and 13mL dimethylacetamide, heat to 75℃, and stir for 25min to completely dissolve CHA, thus obtaining an aromatic amine epoxy resin curing agent solution.

[0115] 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 beaker under continuous vacuum at 110°C for 40 minutes. Subsequently, add 50g of alumina filler to the mixture, heat and stir at 110°C for 30 minutes, and degas at 90°C under a vacuum of 8mbar for 70 minutes to obtain the casting material.

[0116] 3) Heat the above-obtained casting material to 110°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 1 mbar and at 110°C.

[0117] 4) The ambient temperature was then raised to 140℃ over 60 minutes and held for 120 minutes; then raised to 180℃ over 120 minutes and held for 300 minutes; then raised to 210℃ over 120 minutes and held for 180 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-CHA (referred to as CHA in Figures 1 and 2).

[0118] Comparative Example 1:

[0119] A method for preparing an insulating epoxy resin includes the following steps:

[0120] Comparative Example 1 uses 4,4'-diaminodiphenylmethane (DDM), which contains two benzene rings, as a curing agent. The two benzene rings are directly linked by methylene groups. The method for preparing the epoxy resin sample provided includes the following steps:

[0121] 1) Dissolve 10g of DDM in 2mL of acetone and 10mL of dimethylacetamide, heat to 60℃, and stir for 20min to ensure that the DDM is completely dissolved;

[0122] 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 beaker under continuous vacuum at 70°C for 30 minutes. Subsequently, add 40g of alumina filler to the mixture and heat and stir at 60°C for 30 minutes to obtain the casting material.

[0123] 3) Heat the above-obtained casting material to 100°C, and at the same time spray the mold with release agent and preheat it to 100°C. Pour the casting material into the mold and degas it for 60 minutes under a vacuum of 10 mbar and at 100°C.

[0124] 4) The ambient temperature was then raised to 140℃ over 60 minutes and held for 60 minutes; then raised to 180℃ over 60 minutes and held for 120 minutes; then raised to 200℃ over 60 minutes and held for 60 minutes; then the heating was stopped and the mixture was allowed to cool naturally to room temperature in the furnace. The mixture was then demolded to obtain insulating epoxy resin, named EP-DDM (denoted as DDM in Figures 1 and 2).

[0125] The curing agent used in Comparative Example 1 is a commonly used aniline curing agent. The 1,4 substitution positions between the two benzene rings are directly linked by methylene groups, thus forming charge transport channels within and between the benzene ring structures of the molecular chain, resulting in weak electrical insulation properties. Therefore, this is used as a comparison to verify the effect of the introduction of functional bridging bonds on the electrothermal properties of aniline-cured epoxy resin.

[0126] Figure 1 shows the Fourier transform infrared spectra of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of the present invention. Fourier transform infrared tests were performed on the insulating epoxy resins prepared in Examples 1-5 and Comparative Example 1, and the test results were compared and analyzed. The analysis results are shown in Figure 1. It can be seen that the methods provided in Examples 1-5 and Comparative Example 1 all ensured the complete crosslinking reaction between the epoxy resin and the curing agent.

[0127] Figure 2 shows the differential scanning calorimetry results of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of this invention. For the insulating epoxy resins prepared in Examples 1-5 and Comparative Example 1, in order to analyze and compare the effect of the proposed method on thermal stability, differential scanning calorimetry was used to measure the temperature at 10℃ / min under a nitrogen atmosphere, and the test results were compared and analyzed. The analysis results are shown in Figure 2. It can be seen that the introduction of benzene rings leads to an increase in the glass transition temperature of epoxy resin, which is much higher than the glass transition temperature of traditional anhydride-cured epoxy resin (approximately 120℃). This indicates that the thermal stability of epoxy resin is improved due to the introduction of polybenzene ring curing agents.

[0128] Figure 3 shows a comparison of the high-temperature DC breakdown strength and high-temperature volume resistivity results of the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1 of this invention. To verify the influence of the proposed method on the high-temperature electrical properties of the epoxy resins, high-temperature electrical performance tests were conducted on the insulating epoxy resins obtained in Examples 1-5 and Comparative Example 1. The DC breakdown strength test results and DC volume resistivity test results at 120℃ are shown in Figure 3. It can be found that aromatic amine epoxy resin curing agents containing strong electron-withdrawing bridge bonds and those containing large-volume bridge bonds can maintain high electrical performance at high temperatures. For EP-6FDAM, its breakdown strength at 120℃ reached 393.83 kV / mm, and its volume resistivity reached 2.91 × 10⁻⁶ kV / mm. 14 The Ω·cm values ​​are all far higher than those of traditional anhydride-cured epoxy resins.

[0129] This invention proposes a formulation strategy for electrical epoxy resins with high thermal stability and high electrical resistance by utilizing multi-aromatic structures and functional bridging bonds. The core lies in using polyaromatic diamines as curing agents in epoxy resins, introducing rigid aromatic structures into the epoxy backbone to enhance its thermal stability and increase its glass transition temperature. Furthermore, functional bridging bonds are introduced between benzene rings to break the conjugated structure of the benzene rings, thereby improving electrical performance. The introduced functional bridging bonds are divided into two types: the first type is strongly electron-withdrawing groups, which construct electron traps between the benzene ring structures to block charge transport within the epoxy molecular chain; the second type is sterically hindered groups, whose large size hinders the π-π stacking interaction between benzene rings, thus blocking charge transport between different epoxy molecular chains. By designing the molecular structure of polyaniline functionally bridging amine curing agents, on the one hand, rigid structures are introduced into the epoxy crosslinked backbone to improve thermal stability; on the other hand, the two types of functional bridging groups are used to construct charge carrier traps, thereby improving electrical performance. The resulting epoxy resin material, which possesses high thermal stability and high electrical strength, helps to address the electrical performance issues of key insulation components in DC GIS / GIL under high temperature gradients and high electric fields.

[0130] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. An aromatic amine epoxy resin curing agent, characterized in that, include: The design structure consists of at least two benzene ring structures connected by functional bridging bonds; an amino functional group is set at each end of the design structure. No strong electron-withdrawing substituents are placed in the position adjacent to the amino functional group; The functional bridging bond is located at the 1,4 substitution site or the 1,3 substitution site of the benzene ring structure.

2. The aromatic amine epoxy resin curing agent according to claim 1, characterized in that, The functional bridging bond is a strong electron-withdrawing group or a sterically hindered group.

3. 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 aromatic amine epoxy resin curing agent according to claim 2, characterized in that, The large steric hindrance group is -C2H6, -C2F6 or -C6H 12 .

5. A method for preparing an insulating epoxy resin, characterized in that, Includes the following steps: 1) Dissolve the aromatic amine epoxy resin curing agent according to any one of claims 1-4 in a mixed solvent of acetone and dimethylacetamide, and heat and stir for the first time until completely dissolved to obtain an aromatic amine epoxy resin curing agent solution; 2) Add the aromatic amine epoxy resin curing agent solution obtained in step 1) to the preheated epoxy resin monomer, and perform a second heating and stirring under continuous vacuum conditions; then add filler, perform a third heating and stirring, and perform a first degassing treatment to obtain the casting material. 3) Pour the casting material obtained in step 2) into a preheated mold, perform a second degassing treatment, and after curing, allow it to cool naturally to room temperature before demolding to obtain insulating epoxy resin.

6. The method for preparing the insulating epoxy resin according to claim 5, characterized in that, In step 1), the ratio of aromatic amine epoxy resin curing agent: acetone: dimethylacetamide is (10-15)g: (2-8)mL: (10-15)mL; The heating temperature for the first heating and stirring is 50~80℃, and the stirring time is 20~40min.

7. The method for preparing the insulating epoxy resin according to claim 5, 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℃, and the preheating time is 4~8h; The heating temperature for the second heating and stirring is 60~120℃, and the stirring time is 10~60min; The heating temperature for the third heating and stirring is 60~120℃, and the stirring time is 10-30min; The conditions for the first degassing treatment are: under a vacuum of 1~10 mbar, at a temperature and pressure of 60~120℃ for 30~120 min.

8. The method for preparing the insulating epoxy resin according to claim 5, characterized in that, In step 3), the method for obtaining the preheated mold includes: spraying a release agent in advance and heating it to 100°C; The conditions for the second degassing treatment are: under a vacuum of 1-10 mbar, at a temperature and pressure of 60-120°C for 30-60 minutes. The curing conditions are as follows: heat to 120~140℃ and hold for 60~180 min; then heat to 150~180℃ for 60~120 min and hold for 120~300 min; then heat to 190~210℃ for 60~120 min and hold for 60~180 min.

9. An insulating epoxy resin, characterized in that, It is prepared by the preparation method described in any one of claims 5-8.

Images