Single-component epoxy adhesive suitable for magnetic induction heating curing and preparation method thereof

Abstract

The invention relates to a single-component epoxy adhesive suitable for magnetic induction heating curing and a preparation method of the single-component epoxy adhesive. The adhesive comprises the following components in percentage by weight: 3-10% of a modifier, 3-15% of bisphenol F type epoxy resin, 1-4% of alkyl glycidyl ether, 5-14% of a curing agent, 35-50% of filler, 0.5-2% of carbon black, 0.5-3% of fumed silica, 0.5-5% of an auxiliary agent and the balance of first bisphenol A type epoxy resin, the modifier is polyurethane modified epoxy resin; the curing agent comprises dicyandiamide and imidazole, and the weight ratio of the dicyandiamide to the imidazole is (3-8): (2-6). According to the invention, the modifier is limited to be polyurethane modified epoxy resin, fumed silica is added, and the curing agent comprises the compounding of dicyandiamide and imidazole, so that the prepared adhesive can keep the heat conduction and toughening properties, further balance the stability and sag resistance, and meet the application of a magnetic induction heating process.

Description

Technical Field

[0001] This invention relates to the field of epoxy adhesive technology, specifically to a one-component epoxy adhesive suitable for magnetic heating curing and its preparation method. Background Technology

[0002] In the bonding of precision components such as magnets and electronic parts, single-component epoxy adhesives are widely used due to their advantages such as convenient application and no need for on-site mixing. Magnetic heating curing technology, with its high efficiency, energy saving, and precise temperature control, is gradually becoming the core curing method for this type of adhesive. It uses an alternating magnetic field to heat the magnetic substrate or filler, achieving rapid curing of the adhesive and significantly improving production efficiency. Current research has explored magnetic heating curing of single-component epoxy adhesives, but epoxy adhesives have shortcomings in mechanical properties, storage stability, and application adaptability, limiting their application in high-end precision manufacturing. Therefore, developing a magnetic heating curing single-component epoxy adhesive that combines high tensile shear strength, excellent thermal conductivity, good storage stability, and anti-sagging properties has become an urgent technical problem to be solved in this field.

[0003] Chinese invention patent application CN114032056A discloses a single-component epoxy resin adhesive for bonding magnetic steel. It uses epoxy resin, toughening agent, metal / magnetic powder filler, and dicyandiamide-based curing agent, and can be cured by high-frequency electromagnetic heating for 1-2 minutes with a thermal efficiency exceeding 90%, making it suitable for bonding magnetic steel. However, this adhesive has limited tensile and shear strength, making it difficult to withstand the mechanical stress of precision components. Furthermore, it is prone to sagging under vertical construction or high-temperature curing conditions, affecting bonding accuracy. Summary of the Invention

[0004] The first aspect of this invention provides a one-component epoxy adhesive suitable for magnetic heating curing, comprising, by weight percentage: 3-10% modifier, 3-15% bisphenol F type epoxy resin, 1-4% alkyl glycidyl ether, 5-14% curing agent, 35-50% filler, 0.5-2% carbon black, 0.5-3% fumed silica, 0.5-5% additives, with the balance being a first bisphenol A type epoxy resin; wherein the modifier is a polyurethane-modified epoxy resin.

[0005] The curing agent comprises dicyandiamide and imidazole, wherein the weight ratio of dicyandiamide to imidazole is (3-8):(2-6).

[0006] Optionally, by weight percentage, the components include: 5-10% modifier, 4-6% bisphenol F epoxy resin, 1-3% alkyl glycidyl ether, 3-8% dicyandiamide, 2-6% imidazole, 35-45% filler, 0.5-2% carbon black, 0.6-1.1% fumed silica, 0.5-3% additives, and the balance is made up with first bisphenol A epoxy resin; the modifier is a polyurethane modified epoxy resin.

[0007] Existing technologies typically focus only on the thermal conductivity or toughening of adhesives, using dicyandiamide or a single accelerator as the curing agent in epoxy resin systems to achieve improved thermal conductivity or toughening effects. However, they do not address stability-related aspects and have limited compatibility with magnetic heating processes. This invention, by specifying the modifier as polyurethane-modified epoxy resin, adding fumed silica, and using dicyandiamide and imidazole as the curing agent in a weight ratio of (3-8):(2-6), produces an adhesive that maintains thermal conductivity and toughening properties while further balancing stability and anti-sagging properties, thus meeting the requirements of magnetic heating processes. It is speculated that the polyurethane-modified epoxy resin effectively improves the system's toughness and compensates for the brittleness of pure epoxy by embedding flexible segments into the epoxy resin crosslinking network. The hydrophobic fumed silica forms a three-dimensional network structure in the system, significantly enhancing anti-sagging properties and preventing adhesive loss during vertical construction or high-temperature curing. Its dispersion stability complements the toughening effect of the modifier and does not affect the heat conduction channels. The combination of dicyandiamide and imidazole amine provides rigid support for high-temperature curing, while imidazole precisely controls the curing rate, ensuring rapid curing within 15 minutes at 165℃ under magnetic heating and preventing premature reaction during room temperature storage. The synergy of these three factors enables the adhesive to maintain thermal conductivity and toughening properties while achieving a balance between storage stability (viscosity increase percentage ≤15.84%) and anti-sagging properties (sagging length ≤5.15mm), thus resolving the contradiction between the multiple requirements of rapid curing, stable storage, and anti-sagging in the magnetic heating process.

[0008] The bisphenol F type epoxy resin includes at least one of the following grades: 862, YDF-170, YDF-175, BEF-170, NPEF-170, DER354, EPON863, and BPSF-170.

[0009] The raw materials for preparing the polyurethane modified epoxy resin include: second bisphenol A type epoxy resin, aliphatic polyisocyanate, catalyst, and polypropylene glycol. The weight ratio of the second bisphenol A type epoxy resin, aliphatic polyisocyanate, and catalyst is (260-320):(180-200):(0.25-0.4).

[0010] The first bisphenol A type epoxy resin and the second bisphenol A type epoxy resin are selected from at least one of the following grades: E44, E51, E31, E39D, E42, E54, E60.

[0011] The aliphatic polyisocyanate includes at least one of HDI trimer, HDI dimer, IPDI (isophorone diisocyanate), HMDI (hexamethylene diisocyanate), TDI trimer (aliphatic modified), XDI (phenylenediamine diisocyanate), and NDI (naphthalene diisocyanate).

[0012] The catalyst comprises at least one of dibutyltin dilaurate, dioctyltin dilaurate (DOTL), stannous octoate, dibutyltin maleate, zinc isooctanoate, tetrabutyl titanate, and zirconium acetylacetonate.

[0013] The molecular weight of the polypropylene glycol is 200-1000.

[0014] The method for preparing the polyurethane-modified epoxy resin includes: mixing a second bisphenol A type epoxy resin, an aliphatic polyisocyanate, and a portion of a catalyst, and reacting to prepare a prepolymer; lowering the temperature of the prepared prepolymer to 30-50°C, and then slowly adding polypropylene glycol and the remaining catalyst sequentially at a rate of 40-80 drops / minute; after the addition is complete, maintaining the temperature to carry out the reaction, thereby obtaining the polyurethane-modified epoxy resin.

[0015] The raw material ratio and structural design of the self-made polyurethane modified epoxy resin of this invention form a synergistic effect, significantly improving the tensile shear strength of the adhesive. The second bisphenol A type epoxy resin provides a rigid framework. The -NCO groups of the aliphatic polyisocyanate react with the hydroxyl groups of the epoxy resin to form a prepolymer. The flexible segments of polypropylene glycol are subsequently incorporated into the prepolymer, constructing a cross-linked structure of "rigid matrix - flexible segments." The precise weight ratio of the catalyst (260-320):(180-200):(0.25-0.4) controls the reaction rate, ensuring sufficient reaction between the -NCO groups and polypropylene glycol, avoiding incomplete reaction leading to insufficient incorporation of flexible segments or excessive cross-linking, which increases brittleness. This synergistic effect of raw material ratio and structural design allows the modifier to efficiently fuse with the bisphenol A and bisphenol F type epoxy resin matrix, forming a uniform and dense cross-linked network, significantly improving mechanical properties and enabling the tensile shear strength to exceed 30 MPa.

[0016] The imidazoles include blocked imidazoles.

[0017] The blocked imidazole includes at least one of the following brands: LBW-E80, EMI-24, 2E4MZ-CN, C11Z, 1B2MZ, TMA-imidazole, IM-8, and IM-12.

[0018] The filler is pretreated with epoxy silane.

[0019] Optionally, the filler includes a metal oxide.

[0020] Optionally, the metal oxide filler includes at least one of aluminum oxide, magnesium oxide, zirconium oxide, titanium dioxide, zinc oxide, beryllium oxide, and aluminum nitride.

[0021] Optionally, by weight percentage, the particle size distribution of the filler is as follows: 15-25% of the filler with a particle size of 2-8 μm, 5-15% of the filler with a particle size of 0.5-1.5 μm, and the filler with a particle size of 10-30 μm to make up the balance.

[0022] This invention utilizes epoxy silane pretreatment of metal oxide fillers, which synergistically combine with a specific particle size distribution to achieve a balance between high thermal conductivity and high strength. Metal oxides themselves possess excellent thermal conductivity. Epoxy silane pretreatment improves the interfacial compatibility between the filler and the epoxy resin matrix through chemical bonding, reducing interfacial voids and thermal resistance, while simultaneously enhancing interfacial bonding strength, ensuring strength transfer. The particle size distribution design constructs a dense packing structure of "large particles forming the framework, medium particles filling the gaps, and small particles filling the micropores," maximizing the filler contact area and forming continuous, efficient thermal conduction channels (thermal conductivity ≥ 0.58 W / (m²)). This process avoids stress concentration caused by filler agglomeration. Pretreatment solves the interfacial bonding problem, and particle size distribution solves the problems of thermal conductivity continuity and packing density. The two work together to ensure that the adhesive maintains high tensile shear strength (≥36MPa) while having high thermal conductivity.

[0023] The fumed silica includes hydrophobic fumed silica.

[0024] The alkyl glycidyl ethers include at least one of benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether.

[0025] This invention utilizes a specific type of alkyl glycidyl ether to achieve a synergistic balance between toughening and viscosity reduction through precise control of its structure and dosage. As an active diluent, the epoxy groups of the alkyl glycidyl ether participate in the curing reaction, avoiding performance loss caused by the volatilization of inactive diluents. Simultaneously, the flexible alkyl segments can embed into the epoxy resin crosslinking network, alleviating internal stress during curing and achieving toughening. The simplicity of its molecular structure also reduces system viscosity, improving application flowability. Furthermore, when the dosage is limited to 1-4%, excessive dilution will not lead to a decrease in crosslinking density. This synergistic effect of "active participation + flexible toughening + moderate viscosity reduction" solves the problems of excessive viscosity and difficult application in pure epoxy resin systems, while avoiding insufficient toughness caused by viscosity reduction, thus achieving a balance between application adaptability and mechanical properties.

[0026] The additives include coupling agents and dispersants.

[0027] The coupling agent includes an epoxy silane coupling agent.

[0028] The epoxy silane coupling agent includes at least one of the following grades: KH560, KH570, KH792, A-187, A-186, Z-6040, Z-6011, and KBE-403.

[0029] The dispersant includes at least one of the following brands: BYK-110, BYK-163, BYK-180, BYK-9076, EFKA-4010, EFKA-4050, TEGODispers750W, TEGODispers760W, Lubrizol Solsperse24000, and Solsperse32500.

[0030] The second aspect of the present invention provides a method for preparing an epoxy adhesive, comprising the following steps: mixing bisphenol A epoxy resin, a modifier, bisphenol F epoxy resin, and alkyl glycidyl ether uniformly to obtain an epoxy resin composite; adding filler, fumed silica, carbon black, and dispersant to the epoxy resin composite and mixing uniformly to obtain a mixture; adding coupling agent and curing agent to the mixture and mixing uniformly to obtain an epoxy adhesive.

[0031] Beneficial effects 1. The present invention specifies that the modifier is polyurethane modified epoxy resin, adds fumed silica, and the curing agent includes dicyandiamide and imidazole, wherein the weight ratio of dicyandiamide and imidazole is (3-8):(2-6). The resulting adhesive can maintain thermal conductivity and toughening properties while further balancing stability and anti-sagging properties, thus meeting the application requirements of magnetic induction heating process.

[0032] 2. This invention uses a self-made polyurethane modified epoxy resin. The raw materials include: second bisphenol A type epoxy resin, aliphatic polyisocyanate, catalyst, and polypropylene glycol. The weight ratio of the second bisphenol A type epoxy resin, aliphatic polyisocyanate, and catalyst is (260-320):(180-200):(0.25-0.4), which can further improve the tensile shear strength of the adhesive to more than 30 MPa.

[0033] 3. This invention achieves high thermal conductivity (≥0.58W / (m·k)) while maintaining high tensile shear strength (≥36MPa) by limiting the filler to metal oxides pretreated with epoxy silane and specifying that the filler particle size distribution is as follows: 15-25% of 2-8μm particles, 5-15% of 0.5-1.5μm particles, and a balance of 10-30μm particles.

[0034] 4. By adding specific types of alkyl glycidyl ethers, this invention can achieve a balance between toughening and viscosity reduction, avoiding excessive system viscosity that is detrimental to construction.

[0035] 5. By using a combination of coupling agent and dispersant, this invention ensures that fillers with high filling amount (≥40wt%) can be stably and uniformly dispersed and form a strong interfacial bond, thereby reducing production costs. Attached Figure Description

[0036] Figure 1 The images show the tensile shear strength tests performed using the adhesives of Example 1 and Comparative Example 1. The upper image corresponds to the three parallel samples of Example 1, and the lower image corresponds to the three parallel samples of Comparative Example 1.

[0037] Figure 2 The images are photographs after flow resistance tests were conducted using the adhesives of Example 1 and Comparative Example 1, with the left image corresponding to Example 1 and the right image corresponding to Comparative Example 5.

[0038] Figure 3 The glass transition temperature test curve is shown for the adhesive in Example 1. Detailed Implementation

[0039] Examples 1-5, Comparative Examples 1-14 A one-component epoxy adhesive suitable for magnetic heating curing, the components of which are shown in Table 1 by weight percentage: Table 1

[0040] The bisphenol A epoxy resin was E51 type, purchased from Guangzhou Xuxiang Chemical Co., Ltd.; the bisphenol F epoxy resin was purchased from Hubei Langbowan Biomedical Co., Ltd., grade: 862; the alkyl glycidyl ether was benzyl glycidyl ether, purchased from Aladdin Chemical Reagent Co., Ltd.; the dicyandiamide was purchased from Aladdin Chemical Reagent Co., Ltd.; the blocked imidazole (LBW-E80, purchased from Guangzhou Beicai Coatings Co., Ltd.); the epoxy silane-treated spherical alumina (A252, purchased from Dongguan Dongchao New Material Technology Co., Ltd., consisting of 70wt% alumina with a particle size of 20μm + 20wt% alumina with a particle size of 5μm + 10wt% alumina with a particle size of 1μm); carbon black (660R, purchased from Shandong Nuoyuan Chemical Technology Co., Ltd.); fumed silica (hydrophobic type, purchased from Weifang Sanjia Chemical Co., Ltd.); coupling agent (KH560, purchased from Jinan Yingyu Chemical Co., Ltd.); and dispersant (BYK-110, purchased from Jining Fangyu Chemical Co., Ltd.).

[0041] The preparation method of the polyurethane-modified epoxy resin includes the following steps: Bisphenol A type epoxy resin (E44 type, purchased from Chuzhou Huisheng Electronic Materials Co., Ltd.), aliphatic polyisocyanate (HDI trimer curing agent, NCO content: 22%, purchased from Zhengzhou Alpha Chemical Co., Ltd.), and dibutyltin dilaurate (DBTL, catalyst, purchased from Merck Life Sciences) were added sequentially to a reaction flask in a weight ratio of epoxy resin:HDI:DBTL of 300:190.9:0.3. The reaction was carried out under nitrogen protection, at a reaction temperature of 70℃, a stirring speed of 800 rpm, and a reaction time of 2.5 minutes to prepare a prepolymer of epoxy resin and polyisocyanate. At the beginning of the reaction, a small sample was taken for Fourier Transform Infrared (FTIR) spectroscopy, and the initial peak area of ​​the -NCO groups in the sample was recorded. During the reaction, a small sample was taken every 15 minutes, and FTIR tests were performed periodically. The reaction was stopped when the peak area of ​​the remaining -NCO groups was one-third of the initial peak area.

[0042] The temperature of the prepared prepolymer was lowered to 40°C, and then 66.7 g of polypropylene glycol P400 (purchased from Merck Life Sciences) and 0.3 g of DBTL were slowly added dropwise at a rate of 1 drop per second. After the addition was complete, the temperature was raised to 50°C and maintained thereafter, and the mixture was stirred at 800 rpm for 1-2 hours. Small samples were taken every 15 minutes. The reaction ended when the peak of -NCO in the FTIR spectrum disappeared. The resulting sample was then cooled to room temperature (25°C) to obtain the polyurethane-modified epoxy resin.

[0043] A method for preparing a one-component epoxy adhesive suitable for magnetic heating and curing comprises the following steps: Bisphenol A epoxy resin, modifier, bisphenol F epoxy resin and alkyl glycidyl ether are added to the reaction vessel of the mold temperature controller in sequence. The mixture is then stirred in the mold temperature controller under the following conditions: vacuum environment, temperature 25℃, 1200rpm and stirring time 30min. After stirring, the epoxy resin composite is obtained. Filler, fumed silica, carbon black, and dispersant were added to the epoxy resin composite and stirred under vacuum, 25°C, 100 rpm, and for 10 minutes to ensure complete mixing of the filler into the resin composite. After stirring, the stirring speed was increased to 1200 rpm, and stirring continued for 20 minutes. Add coupling agent, dicyandiamide and imidazole to the mixing tank of the mold temperature controller in sequence. After the addition is complete, stir under the following conditions: vacuum, 25°C, 100 rpm and stirring time for 10 min. After stirring is completed, increase the stirring speed to 1200 rpm and continue stirring for 20 min. After stirring is completed, epoxy adhesive is obtained.

[0044] Comparative Example 15 An epoxy adhesive, purchased from Shenzhen Denodis Technology Co., Ltd., brand name: D96.

[0045] Performance testing methods The adhesives prepared in the examples and comparative examples were subjected to the following performance tests, and the test data are listed in Table 2.

[0046] 1. Storage stability performance: Take out the products of the examples and comparative examples, and perform viscosity tests according to the "ASTM D4287 cone plate rotation viscometer method": record the viscosity data of the adhesive on the 1st and 7th days under normal temperature (25°C) storage conditions, and calculate the percentage increase in viscosity of the adhesive on the 7th day relative to the viscosity on the 1st day.

[0047] 2. Tensile Shear Strength Performance: The products from the examples and comparative examples were taken out, and using a 2mm × 25mm × 100mm magnet as the test substrate, the tensile shear strength of the adhesive against cast iron was tested according to GB / T 7124—2008 "Determination of Tensile Shear Strength of Adhesives (Rigid Material to Rigid Material)". The curing conditions were 165℃ for 15 minutes. Figure 1 As shown, the mechanical properties of Example 1 are superior to those of Comparative Example 1.

[0048] 3. Resistance to Flow: The products from the examples and comparative examples were taken out, and a 2mm × 25mm × 100mm magnet was used as the test substrate. Referring to GB / T 31113-2014 "Test Method for Resistance to Flow of Adhesives", the adhesive was tested under the following conditions: heated to 165℃ in an alternating magnetic field at a heating rate of 50℃ / min for 15 minutes; the substrate was placed vertically at 90°; the adhesive coating area was 2mm × 25mm; and the coating amount was 0.625g. The distance the adhesive fell vertically (sag length) was measured. The sagging length was used as a reference standard for the adhesive's resistance to flow. Figure 2 As shown, Example 1 exhibits better resistance to flow than Comparative Example 5.

[0049] 4. Thermal conductivity: Samples of the products from the examples and comparative examples were prepared and tested according to the "Standard Test Method for Thermal Conductivity of Thermally Conductive and Insulating Materials" (ASTM D5470-17). The thermal conductivity of different products was recorded.

[0050] 5. Glass transition temperature: Samples of the products from the examples and comparative examples were prepared and tested according to GB-T 40396-2021 "Test method for glass transition temperature of polymer-based composite materials - Dynamic mechanical analysis method (DMA)". The glass transition temperatures of different products were recorded. Figure 3 As shown, the adhesive prepared in Example 1 has excellent thermal properties.

[0051] Performance test data Table 2

[0052] As shown in Table 1, the formulations of the examples using self-made polyurethane modified epoxy resin, bisphenol F type epoxy resin, dicyandiamide-imidazolium composite curing agent with a weight ratio of (3-8):(2-6), epoxy silane pretreated metal oxide filler with a specific particle size distribution, hydrophobic fumed silica, and a combination of coupling agent and dispersant, along with 1-4% alkyl glycidyl ether, exhibited comprehensive and excellent overall performance: the tensile shear strength reached over 36 MPa (maximum 40.99 MPa), significantly better than Comparative Example 1 (18.49 MPa), Comparative Example 2 (26.82 MPa), and commercially available product comparative examples without modifiers. 15 (30.80 MPa); exhibits outstanding anti-flow properties, with sag lengths not exceeding 5.15 mm, far superior to Comparative Example 5 (22.37 mm) with a single curing agent, Comparative Example 9 (26.35 mm) with calcium carbonate filler, and Comparative Example 11 (14.96 mm) without fumed silica; demonstrates good storage stability, with viscosity increase percentages below 15.84% after 7 days of storage at room temperature, significantly better than Comparative Example 4 (99.45%) and Comparative Example 6 (65.70%) with unbalanced curing agent ratios, and Comparative Example 10 (46.31%) with untreated filler; thermal conductivity remains stable at 0.58 W / (m²). k) and above (maximum 0.66W / (m) k), which is superior to Comparative Example 8 (0.59 W / (m)) of the gradeless metal oxide filler. k), Comparative Example 10 of untreated filler (0.55W / (m)) Comparative Example 9 (0.53W / (m)) and non-metallic oxide fillers The glass transition temperature of the sample remained between 130-143℃, and the thermal properties were stable. In contrast, the comparative sample, due to formulation defects such as lack of self-made polyurethane modifier, single or improper ratio of curing agent, no pretreatment / no gradation of filler, no fumed silica, missing or replaced additives or excessive alkyl glycidyl ether, all showed single or multiple performance shortcomings such as insufficient tensile shear strength, poor anti-sagging, poor storage stability or low thermal conductivity. This fully demonstrates the key role of the synergistic effect of each component in the formulation of the example in improving the overall performance of the adhesive.

Claims

1. A one-component epoxy adhesive suitable for magnetic heating curing, characterized in that, By weight percentage, the components include: 3-10% modifier, 3-15% bisphenol F epoxy resin, 1-4% alkyl glycidyl ether, 5-14% curing agent, 35-50% filler, 0.5-2% carbon black, 0.5-3% fumed silica, 0.5-5% additives, and the balance is made up with first bisphenol A epoxy resin; the modifier is a polyurethane modified epoxy resin; the curing agent includes dicyandiamide and imidazole, and the weight ratio of dicyandiamide to imidazole is (3-8):(2-6).

2. The epoxy adhesive according to claim 1, characterized in that, The raw materials for preparing the polyurethane modified epoxy resin include: second bisphenol A type epoxy resin, aliphatic polyisocyanate, catalyst, and polypropylene glycol. The weight ratio of the second bisphenol A type epoxy resin, aliphatic polyisocyanate, and catalyst is (260-320):(180-200):(0.25-0.4).

3. The epoxy adhesive according to claim 2, characterized in that, The imidazoles include blocked imidazoles.

4. The epoxy adhesive according to claim 3, characterized in that, The filler is pretreated with epoxy silane.

5. The epoxy adhesive according to claim 1 or 4, characterized in that, The filler comprises metal oxides.

6. The epoxy adhesive according to claim 1 or 4, characterized in that, The particle size distribution of the filler, by weight percentage, is as follows: 15-25% of the filler with a particle size of 2-8 μm, 5-15% of the filler with a particle size of 0.5-1.5 μm, and the filler with a particle size of 10-30 μm is used to make up the balance.

7. The epoxy adhesive according to claim 1, characterized in that, The fumed silica includes hydrophobic fumed silica.

8. The epoxy adhesive according to claim 1, characterized in that, The alkyl glycidyl ethers include at least one of benzyl glycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene glycol diglycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether.

9. The epoxy adhesive according to claim 1, characterized in that, The additives include coupling agents and dispersants.

10. A method for preparing the epoxy adhesive according to claim 9, characterized in that, Includes the following steps: Bisphenol A epoxy resin, modifier, bisphenol F epoxy resin and alkyl glycidyl ether are mixed evenly to obtain an epoxy resin composite; filler, fumed silica, carbon black and dispersant are added to the epoxy resin composite and mixed evenly to obtain a mixture; coupling agent and curing agent are added to the mixture and mixed evenly to obtain an epoxy adhesive.

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