Epoxy resin adhesive as well as preparation method and application thereof

Abstract

The invention discloses an epoxy resin adhesive as well as a preparation method and application thereof, and relates to the technical field of adhesives, the epoxy resin adhesive comprises the following components: epoxy resin, a modified flexibilizer, a curing agent, a filler and a coloring agent; wherein the modified toughening agent is prepared by the following steps: dissolving PEG in deionized water, and adding alpha-CD for reaction; then adding DIBM for reaction, precipitating, washing and drying to obtain an intermediate product; the intermediate product, bio-based polyester polyol and IPDI are subjected to a polymerization reaction, a modified toughening agent with a rotaxane structure and disulfide bonds is obtained, when the modified toughening agent is impacted by external force, an alpha-CD ring can slide along PEG, a pulley effect is generated, local stress is dispersed to a larger range, and the toughness of the adhesive is greatly improved; the rotaxane structure and the epoxy matrix are connected without chemical bonds, and the integrity of a cross-linked network is not damaged by the sliding motion of the rotaxane structure, so that the glass-transition temperature is not reduced while the toughening is realized.

Description

Technical Field

[0001] This invention relates to the field of adhesive technology, specifically to an epoxy resin adhesive, its preparation method, and its application. Background Technology

[0002] Epoxy resin adhesives are widely used in high-end fields such as aerospace, automotive manufacturing, and electronic packaging due to their excellent bonding strength, chemical resistance, and electrical insulation. However, the inherent defects of epoxy resins after curing, such as high crosslinking density, brittleness, and poor impact resistance, have long limited their reliability under dynamic loads and extreme environments. To solve this problem, existing technologies mainly use liquid rubber (such as carboxyl-terminated nitrile rubber CTBN), rigid nanoparticles (such as nano-SiO2), or thermoplastic resins (such as polyetherimide PEI) for toughening modification. More importantly, none of the above methods can impart a removable adhesive layer. For high-value components in aerospace, new energy vehicles, and other fields, if defects occur after bonding or recycling is required, destructive disassembly is often the only option, resulting in serious waste.

[0003] However, all of the above methods have inherent limitations: liquid rubber toughening can improve impact strength, but it will significantly reduce the glass transition temperature (Tg) and modulus of the material, sacrificing heat resistance; nanoparticle toughening faces difficulties in dispersion and interfacial compatibility, and the toughening effect is limited; thermoplastic resin toughening often leads to a sharp increase in system viscosity and deterioration of process performance. Summary of the Invention

[0004] The present invention aims to solve the problem that existing epoxy resin adhesives are difficult to combine high impact strength, high Tg, and good bonding and disassembly performance.

[0005] To address the aforementioned problems, in a first aspect, the present invention provides an epoxy resin adhesive comprising the following components in parts by weight: 60 parts epoxy resin, 5-10 parts modified toughening agent, 5-15 parts curing agent, 10-30 parts filler, and 2-5 parts colorant. The modified toughening agent is prepared through the following steps: Step 1: Dissolve polyethylene glycol (PEG) in deionized water and add α-cyclodextrin (α-CD) to react; The hydrophilic chains of PEG are in an extended state in water. The hydrophobic cavity of α-CD can self-assemble with the PEG chain through hydrogen bonding and hydrophobic interactions to form a quasi-rotaxane structure, which is a classic reaction in supramolecular chemistry. Step 2: Add 1,1'-dithiobis(3-isocyano-4-methylbenzene) and react to precipitate, wash, and dry to obtain the intermediate product; PEG has hydroxyl groups at both ends, which react with isocyanate groups to form urethane bonds, forming large-volume end-capping groups, locking α-CD onto the PEG chain to form [2] rotaxane; at the same time, disulfide bonds are introduced; Step 3: The intermediate product is polymerized with bio-based polyester polyol and isophorone diisocyanate (IPDI) to obtain the modified toughening agent.

[0006] The intermediate product is a rotaxane structural unit with isocyanate groups at both ends, which can react with the hydroxyl groups of bio-based polyester polyols to form a block copolymer structure. IPDI is used as a chain extender to adjust the molecular weight.

[0007] Compared with the prior art, the epoxy resin adhesive of the present invention has the following beneficial effects, but not limited to: a modified toughening agent is introduced into the epoxy resin adhesive. The modified toughening agent is formed by self-assembling polyethylene glycol and α-cyclodextrin to form a rotaxane-like structure, and then end-capped by isocyanate containing disulfide bonds in 1,1'-dithiobis(3-isocyano-4-methylbenzene) to construct a rotaxane structural unit [2] and embed it into the polyurethane backbone. After the toughening agent is blended and cured with epoxy resin, the rotaxane structure is uniformly dispersed in the epoxy crosslinking network. When subjected to external impact, the α-CD ring can slide along the polyethylene glycol chain to generate a pulley effect, which disperses the local stress to a larger range and effectively dissipates the impact energy, thereby greatly improving the toughness of the adhesive. At the same time, since the rotaxane structure is not chemically bonded to the epoxy body, its sliding motion does not destroy the integrity of the crosslinking network. Therefore, the glass transition temperature can be kept from decreasing while toughening.

[0008] Furthermore, the aromatic disulfide bonds in 1,1'-dithiobis(3-isocyano-4-methylbenzene) can undergo reversible breakage and recombination under heating or reducing conditions. When the cured adhesive layer is exposed to a solution containing dithiol and heated, the disulfide bonds undergo an exchange reaction, leading to the dissociation of the rotaxane structure and the degradation of the crosslinked network, thereby enabling the controlled disassembly of the adhesive layer. This function is of great significance for the repair, upgrading, and recycling of high-value components such as aerospace structural parts, new energy vehicle battery packs, and precision electronic components.

[0009] Preferably, in steps 1-3, the mass ratio of polyethylene glycol, α-cyclodextrin and 1,1'-dithiobis(3-isocyano-4-methylbenzene) is 1:(1.1-1.5):(2.2-2.8); the mass ratio of the intermediate product to the bio-based polyester polyol and isophorone diisocyanate is 1:(4-8):(1-3).

[0010] Specifically, controlling the mass ratio of polyethylene glycol, α-cyclodextrin, and 1,1'-dithiobis(3-isocyanate-4-methylbenzene) within the range of 1:(1.1-1.5):(2.2-2.8) ensures that α-cyclodextrin is fully wrapped around the polyethylene glycol chain (with a slight excess of α-cyclodextrin), while ensuring sufficient 1,1'-dithiobis(3-isocyanate-4-methylbenzene) to completely seal both ends. Controlling the mass ratio of the intermediate product to bio-based polyester polyol and isophorone diisocyanate within the range of 1:(4-8):(1-3) allows the rotaxane structural units to be uniformly embedded in the polyurethane main chain, ensuring both toughening effect and avoiding compatibility degradation due to excessive rotaxane units.

[0011] Preferably, in step 1, the reaction conditions are: stirring at 100-300 rpm for 12-24 hours at 20-30°C.

[0012] Preferably, in step 1, the number-average molecular weight of the polyethylene glycol is 1000-4000.

[0013] Preferably, in step 1, the purity of the α-cyclodextrin is ≥98%.

[0014] Preferably, in step 2, the reaction conditions are as follows: the catalyst is added under nitrogen protection, and the reaction is carried out at 50-70°C with stirring at 100-300 rpm for 6-12 hours.

[0015] Specifically, the mild conditions are conducive to the self-assembly process of polyethylene glycol and α-cyclodextrin. Too high a temperature will destroy hydrogen bonding and lead to dissociation, while too low a temperature will result in a slow assembly rate. A moderate rotation speed ensures uniform mixing without shear damage. Sufficient reaction time ensures complete formation of quasi-rotaxanes.

[0016] Preferably, the catalyst is dibutyltin dilaurate or stannous octoate, and the amount of catalyst added is 0.05-0.2 wt% of 1,1'-dithiobis(3-isocyano-4-methylbenzene).

[0017] Specifically, nitrogen protection prevents isocyanate groups from reacting with moisture in the air; a catalyst accelerates the reaction between isocyanate and hydroxyl groups; temperature control at 50-70℃ ensures the reaction rate while avoiding side reactions; and sufficient reaction time ensures complete end-capping.

[0018] Preferably, in step 3, the polymerization reaction is carried out under nitrogen protection at 70-90°C with stirring at 100-300 rpm for 4-8 hours.

[0019] Specifically, this temperature range is suitable for the chain extension reaction of polyurethane, ensuring the reaction rate while avoiding side reactions caused by high temperatures; nitrogen protection prevents isocyanate groups from reacting with moisture; and sufficient reaction time ensures that the molecular weight increases to an appropriate range.

[0020] Preferably, the epoxy resin is one or more of bisphenol A type epoxy resin, bisphenol F type epoxy resin, and phenolic epoxy resin.

[0021] Preferably, the curing agent is dicyandiamide, and the particle size D90 of the dicyandiamide is <10 μm.

[0022] Specifically, dicyandiamide is a commonly used latent curing agent for epoxy resins. When mixed with epoxy resins, it is stable at room temperature (for more than 6 months) and cures rapidly when heated to 145-160℃, making it suitable for the industrial application of single-component epoxy adhesives. Controlling the particle size of dicyandiamide to D90 < 10 μm ensures that it is uniformly dispersed in epoxy resins, and that the curing reaction proceeds uniformly, avoiding internal stress and uneven performance caused by localized curing agent aggregation.

[0023] Preferably, the filler is aluminum hydroxide or magnesium hydroxide with an average particle size of 1-10 μm.

[0024] Specifically, aluminum hydroxide and magnesium hydroxide are environmentally friendly inorganic flame retardants. When heated, they decompose and release water of crystallization, absorb heat and dilute combustible gases, and at the same time generate an oxide heat insulation layer, which can improve the flame retardancy rating of epoxy resin from V-1 to V-0. By controlling the particle size within the range of 1-10um, it is possible to ensure good dispersion of fillers in resin without causing agglomeration or excessive viscosity of the system due to excessively small particle size.

[0025] Preferably, the colorant is carbon black.

[0026] In this invention, carbon black not only serves as a coloring agent but also has a thixotropic regulating function: the oxygen-containing functional groups on the surface of carbon black nanoparticles can form hydrogen bonds with epoxy resin, improving the thixotropy of the adhesive (thixotropic index ≥1.7 at 90℃), preventing filler from settling during storage and curing, and avoiding sagging during vertical surface construction.

[0027] Secondly, the present invention discloses a preparation method for preparing the epoxy resin adhesive as described above, comprising the following steps: S1. Weigh the epoxy resin, modified toughening agent, curing agent, filler and colorant according to the weight ratio; S2. Add epoxy resin and modified toughening agent to the reaction vessel and stir and mix at 60-80℃ for 30-60 minutes. S3. Add curing agent, filler and colorant, and disperse at 1000-2000 rpm for 40-60 min under vacuum conditions at 80-100℃; S4. Cool to below 40°C, filter, degas, and package to obtain the epoxy resin adhesive.

[0028] The preparation method uses conventional reaction vessel equipment and can be obtained through steps such as premixing, high-speed dispersion, cooling and filtration. The process is simple, requires no special equipment or harsh conditions, and is easy to achieve industrial-scale production.

[0029] Thirdly, the present invention also discloses the application of the epoxy resin adhesive described above in the bonding of aerospace structural components, the encapsulation of new energy vehicle battery packs, the encapsulation of electronic components, or the reversible bonding of high-value components.

[0030] Aerospace structural components have extremely high requirements for material strength, toughness, and weather resistance. The adhesive of this invention combines high strength and high toughness, meeting the requirements for use in extreme environments. New energy vehicle battery packs have special requirements for flame retardancy and maintainability. The flame-retardant filler and reversible bonding function of this invention can simultaneously meet safety requirements and the disassembly and maintenance needs of battery modules. Electronic component packaging has strict requirements for heat resistance and insulation. The adhesive of this invention has a Tg ≥ 122℃, and its conductivity / insulation properties can be adjusted by carbon black. Reversible bonding of high-value components is one of the core advantages of this invention. Utilizing the dynamic reversible properties of disulfide bonds, controllable disassembly can be achieved under specific conditions, providing a guarantee for the repair, upgrading, and recycling of components. Detailed Implementation

[0031] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0032] The terminology used in the embodiments of this application is for the purpose of describing particular implementations only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the implementations of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the implementation regulations of this application.

[0034] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this application are commercially available or can be prepared using existing methods; for example, the sources and types of raw material components involved in the following preparation examples, embodiments, and comparative examples are as follows: Polyethylene glycol (PEG): number average molecular weight 2000, analytical grade, purchased from Aladdin Reagent (Shanghai) Co., Ltd., catalog number P109788; α-Cyclodextrin (α-CD): Purity ≥98%, purchased from Tokyo Chemical Industry Co., Ltd., item number C0080; 1,1'-Dithiobis(3-isocyano-4-methylbenzene) (DIBM): CAS No. 672288-55-0, purity ≥95%; purchased from Sigma-Aldrich, catalog number 900910; Dibutyltin dilaurate (DBTDL): analytical grade, catalyst; purchased from Aladdin Reagent (Shanghai) Co., Ltd., catalog number D102907; Stannous octoate: analytical grade, catalyst; purchased from Aladdin Reagent (Shanghai) Co., Ltd., catalog number D105555; Isophorone diisocyanate (IPDI): Industrial grade; purchased from Aladdin Reagent (Shanghai) Co., Ltd., item number S108475; Bio-based polyester polyol: Brand Bio-POL-1000, number average molecular weight 1000, industrial grade, purchased from Shandong Lanxing Dongda Chemical Co., Ltd. Epoxy resin: Bisphenol A type epoxy resin, E-51, epoxy equivalent 200g / eq; purchased from Nan Ya Epoxy Resin, grade NPEL-128; Dicyandiamide: Dyhard 100S, particle size D90 < 5 μm; purchased from AlzChem, Germany; Aluminum hydroxide: H-WF-5, average particle size 5µm; purchased from Chalco Shandong Co., Ltd. Carbon black: Vulcan® 3, N330; purchased from Cabot (China) Investment Co., Ltd.

[0037] Preparation Example 1

[0038] The modified toughening agent is prepared by following these steps in sequence: Step 1: Add 10g of polyethylene glycol to a 500mL three-necked flask, add 100mL of deionized water, stir to dissolve, then add 13g of α-cyclodextrin, and react at 200rpm for 18h in a constant temperature water bath at 25℃. Step 2: Add 25g of 1,1'-dithiobis(3-isocyano-4-methylbenzene) and 0.031g of dibutyltin dilaurate, immediately purge with nitrogen for protection, heat to 60℃, and continue stirring at 200rpm for 9h. After the reaction is complete, slowly pour the reaction solution into a beaker containing 500mL of anhydrous diethyl ether (in an ice-water bath), stirring while pouring, and a white precipitate will form. After standing for 30min, filter with a Buchner funnel and collect the filter cake. Wash the filter cake three times with 50mL of anhydrous ethanol, soaking for 5min each time, and then filter to obtain a solid. Finally, transfer the solid to a vacuum drying oven and dry it under vacuum at 50℃ for 12h to obtain the intermediate product. Step 3: Take 10g of the intermediate product and add it to a 500mL three-necked flask along with 60g of bio-based polyester polyol and 20g of isophorone diisocyanate. Purge the air three times with nitrogen. Under nitrogen protection, heat to 80℃ and stir at 200rpm for 6 hours. After the reaction is complete, pour the viscous liquid into a polytetrafluoroethylene dish and cool to room temperature to obtain the modified toughening agent.

[0039] Preparation Example 2

[0040] The only difference compared to Preparation Example 1 is: (1) In step 1, the amount of α-cyclodextrin added was reduced from 13g to 11g; (2) In step 2, the amount of 1,1'-dithiobis(3-isocyanate-4-methylbenzene) added is reduced from 25g to 22g, and 0.031g of dibutyltin dilaurate is replaced with 0.011g of stannous octoate. (3) Reduce the bio-based polyester polyol from 60g to 40g, and at the same time reduce the isophorone diisocyanate from 20g to 10g; The other steps and conditions were exactly the same as in Preparation Example 1, and the modified toughening agent was finally obtained.

[0041] Preparation Example 3

[0042] The only difference compared to Preparation Example 1 is: (4) In step 1, the amount of α-cyclodextrin added was increased from 13g to 15g; (5) In step 2, the amount of 1,1'-dithiobis(3-isocyanate-4-methylbenzene) added is increased from 25g to 28g, and the amount of dibutyltin dilaurate added is increased from 0.031g to 0.056g. (6) Increase the amount of bio-based polyester polyol from 60g to 80g, and increase the amount of isophorone diisocyanate from 20g to 30g; The other steps and conditions were exactly the same as in Preparation Example 1, and the modified toughening agent was finally obtained.

[0043] Example 1

[0044] This embodiment discloses an epoxy resin adhesive, which is prepared according to the following steps: S1. Weigh 60g of epoxy resin, 7.5g of the modified toughening agent of Preparation Example 1, 10g of dicyandiamide, 20g of aluminum hydroxide and 3.5g of carbon black according to the following weight proportions. S2. Add epoxy resin and modified toughening agent to a 1L reaction vessel, turn on the stirrer, set the speed to 500rpm, heat to 70℃, and stir and mix at a constant temperature for 45min to make the two fully compatible. S3. Add dicyandiamide, aluminum hydroxide, and carbon black sequentially to the reactor. Turn on the vacuum pump and stabilize the vacuum level inside the reactor at -0.08 MPa (gauge pressure). While maintaining the vacuum, raise the temperature to 90℃, adjust the stirring speed to 1500 rpm, and disperse at high speed for 50 minutes; during this period, observe the material temperature and control it at 90±2℃. S4. After dispersion, turn off the heating, introduce cooling water through the jacket, reduce the stirring speed to 200 rpm, and cool down to below 35℃. Filter the material through a 100-mesh stainless steel screen to remove agglomerated particles. Transfer the filtered material to a vacuum degassing machine and degas for 15 minutes at -0.09 MPa. Finally, seal the product in an aluminum foil bag to obtain epoxy resin adhesive.

[0045] Example 2

[0046] Compared with Example 1, the only difference is that the raw material components are adjusted to: 60g epoxy resin, 10g modified toughening agent of Preparation Example 1, 5g dicyandiamide, 10g aluminum hydroxide, and 2g carbon black. The other steps and conditions are exactly the same as in Example 1, and the epoxy resin adhesive is finally obtained.

[0047] Example 3

[0048] Compared with Example 1, the only difference is that the raw material components are adjusted to: 60g epoxy resin, 10g modified toughening agent of Preparation Example 1, 15g dicyandiamide, 30g aluminum hydroxide, and 5g carbon black. The other steps and conditions are exactly the same as in Example 1, and the epoxy resin adhesive is finally obtained.

[0049] Example 4

[0050] The only difference between this embodiment and Example 1 is that the modified toughening agent in Preparation Example 1 is replaced with the modified toughening agent in Preparation Example 2; the other steps and conditions are exactly the same as in Example 1, and finally an epoxy resin adhesive is obtained.

[0051] Example 5

[0052] The only difference between this embodiment and Example 1 is that the modified toughening agent in Preparation Example 1 is replaced with the modified toughening agent in Preparation Example 3; the other steps and conditions are exactly the same as in Example 1, and finally an epoxy resin adhesive is obtained.

[0053] Comparative Example 1

[0054] The only difference between this comparative example and Example 1 is that the modified toughening agent used in Example 1 was omitted; all other steps and conditions were exactly the same as in Example 1, and the epoxy resin adhesive was finally obtained.

[0055] Comparative Example 2

[0056] The only difference between this comparative example and Example 1 is that the modified toughening agent in Example 1 was replaced with a commercially available epoxy resin adhesive (DP460, 3M). TM Scotch-Weld TM Other steps and conditions are exactly the same as in Example 1, and the epoxy resin adhesive is finally obtained.

[0057] The epoxy resin adhesives prepared in Examples 1-5 and Comparative Examples 1-2 were subjected to performance tests. The test items and test methods are as follows: Shear strength: Tested according to GB / T 7124-2008 "Determination of tensile shear strength of adhesives (rigid material to rigid material)"; the substrate is 2024 aluminum alloy with dimensions of 100mm×25mm×1.6mm; the bonding area is 12.5mm×25mm, and the adhesive layer thickness is controlled at 0.2mm; 5 specimens are prepared for each group of samples, and the universal testing machine is used to test them at a loading rate of 5mm / min. The arithmetic mean is taken as the final result, accurate to 0.1MPa.

[0058] Impact strength: Tested according to GB / T 1843-2008 "Determination of Impact Strength of Plastic Cantilever Beams"; the adhesive was cast into unnotched specimens with dimensions of 80mm × 10mm × 4mm; a cantilever beam impact testing machine was used with a pendulum energy of 2.75J, 5 specimens were tested, and the arithmetic mean was taken as the final result, accurate to 0.1 kJ / m². 2 .

[0059] Glass transition temperature (Tg): determined by differential scanning calorimetry (DSC); instrument model: TAInstruments Q2000; test conditions: nitrogen atmosphere, flow rate 50 mL / min; weigh 5-10 mg of the cured gel sample and place it in an aluminum crucible, and heat it from 25℃ to 200℃ at a heating rate of 10℃ / min; take the midpoint of the second scan curve as the glass transition temperature, accurate to 1℃.

[0060] Debonding performance: The specimens prepared according to the shear strength test standard are immersed in an ethanol solution containing 5% (mass fraction) 1,2-ethylenedithiol and heated in an oil bath at 120℃. One specimen is taken out every 5 minutes, and its residual shear strength is tested according to GB / T 7124-2008. The time (minutes) required for the bond strength to drop to below 10% of the initial strength is recorded. If the strength does not decrease significantly after more than 120 minutes, it is recorded as >120.

[0061] The test results are listed in Table 1, as follows: Table 1

[0062] Analysis of the data in Table 1 shows that the shear strength of the epoxy resin adhesives in Examples 1-5 is ≥31.2 MPa and the impact strength is ≥24.6 kJ / m. 2 The Tg values ​​of Examples 1-5 were significantly higher than those of Comparative Examples 1-2, indicating that the modified toughening agent effectively improved the toughness and strength of the adhesive. Meanwhile, the Tg values ​​of Examples 1-5 remained at 122-128℃, showing no significant decrease compared to Comparative Example 1 without the modified toughening agent, and were higher than those of Comparative Example 2. This proves that the toughening mechanism of the present invention does not sacrifice heat resistance and is superior to traditional toughening agents. The epoxy resin adhesives of Examples 1-5 were completely disassembled within 30 minutes in a solution containing dithiol, while the disassembly time of Comparative Examples 1-2 was greater than 120 minutes. This indicates that the addition of the modified toughening agent achieved reversible bonding of the epoxy resin adhesive.

[0063] Example 3 showed the highest impact strength; Example 2 showed the highest Tg, but the impact strength was slightly lower; Examples 4-5 used toughening agents from different preparation examples, and the performance was slightly different but generally excellent, indicating that the overall performance of the epoxy resin adhesive prepared by the preparation method of the present invention can be maintained within a stable range.

[0064] In summary, the epoxy resin adhesive provided by this invention has high strength, high toughness, and excellent heat resistance, and can be widely used in high-value fields such as bonding of aerospace structural components, encapsulation of new energy vehicle battery packs, and encapsulation of electronic components.

[0065] The foregoing has described several embodiments of the present invention in detail, but these descriptions are merely preferred embodiments and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the claims of this invention should still fall within the patent coverage of this invention.

Claims

1. An epoxy resin adhesive, characterized in that, It includes the following components in parts by weight: 60 parts epoxy resin, 5-10 parts modified toughening agent, 5-15 parts curing agent, 10-30 parts filler, and 2-5 parts colorant; The modified toughening agent is prepared through the following steps: Step 1: Dissolve polyethylene glycol in deionized water and add α-cyclodextrin to react; Step 2: Add 1,1'-dithiobis(3-isocyano-4-methylbenzene) and react to precipitate, wash, and dry to obtain the intermediate product; Step 3: The intermediate product is polymerized with bio-based polyester polyol and isophorone diisocyanate to obtain the modified toughening agent.

2. The epoxy resin adhesive according to claim 1, characterized in that, In steps 1-3, the mass ratio of polyethylene glycol, α-cyclodextrin and 1,1'-dithiobis(3-isocyano-4-methylbenzene) is 1:(1.1-1.5):(2.2-2.8); the mass ratio of the intermediate product to bio-based polyester polyol and isophorone diisocyanate is 1:(4-8):(1-3).

3. The epoxy resin adhesive according to claim 1, characterized in that, In step 1, the reaction conditions are: stirring at 100-300 rpm for 12-24 hours at 20-30℃.

4. The epoxy resin adhesive according to claim 1, characterized in that, In step 2, the reaction conditions are as follows: the catalyst is added under nitrogen protection, and the reaction is carried out at 50-70°C with stirring at 100-300 rpm for 6-12 hours.

5. The epoxy resin adhesive according to claim 1, characterized in that, In step 3, the polymerization reaction is carried out under nitrogen protection at 70-90°C with stirring at 100-300 rpm for 4-8 hours.

6. The epoxy resin adhesive according to claim 1, characterized in that, The curing agent is dicyandiamide, and the particle size D90 of the dicyandiamide is <10 μm.

7. The epoxy resin adhesive according to claim 1, characterized in that, The filler is aluminum hydroxide or magnesium hydroxide with an average particle size of 1-10 μm.

8. The epoxy resin adhesive according to claim 1, characterized in that, The colorant is carbon black.

9. A preparation method, characterized in that, The preparation of the epoxy resin adhesive as described in any one of claims 1-8 comprises the following steps: S1. Weigh the epoxy resin, modified toughening agent, curing agent, filler and colorant according to the weight ratio; S2. Add epoxy resin and modified toughening agent to the reaction vessel and stir and mix at 60-80℃ for 30-60 minutes. S3. Add curing agent, filler and colorant, and disperse at 1000-2000 rpm for 40-60 min under vacuum conditions at 80-100℃; S4. Cool to below 40°C, filter, degas, and package to obtain the epoxy resin adhesive.

10. The application of an epoxy resin adhesive as described in any one of claims 1-8 in the bonding of aerospace structural components, encapsulation of new energy vehicle battery packs, encapsulation of electronic components, or reversible bonding of high-value components.

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