Highly adhesive toughened epoxy resin glue and its preparation method

Abstract

This invention discloses a high-adhesion toughened epoxy resin adhesive and its preparation method, belonging to the field of epoxy resin technology. The epoxy resin adhesive of this invention comprises the following components by weight: 100 parts epoxy resin, 5-8 parts modified silica, and 100-195 parts modified polyimide curing agent; the modified polyimide curing agent is obtained by linear polycondensation of hydrophobic diamine and pyromellitic anhydride. The modified polyimide curing agent forms a semi-interpenetrating network structure with the epoxy resin, which bears stress and prevents crack propagation; simultaneously, the chain segments dissipate energy through force slippage and tensile stress, improving impact toughness; the polar imide bonds in the structure, in conjunction with the hydroxyl groups generated by the crosslinking of epoxy resin and curing agent, impart strong adhesive strength; the hydrophobic fluorosilicone segments form a continuous hydrophobic interface, resulting in a highly dense adhesive layer that effectively blocks moisture intrusion and maintains long-term high adhesive strength, making it suitable for use in electronic device encapsulation materials.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin technology, specifically to a high-adhesion toughened epoxy resin adhesive and its preparation method. Background Technology

[0002] Epoxy resin is a thermosetting polymer prepared by cross-linking epoxy groups with amines, acid anhydrides, or imidazole curing agents and then curing it through heat. It possesses chemical stability, thermal stability, high strength, and good adhesion, and is widely used in electronic device packaging materials and other fields. However, it also has certain drawbacks. Thermosetting epoxy resin has high rigidity and almost no toughness, making it prone to cracking under external forces such as vibration and impact. Furthermore, the adhesive layer has poor resistance to damp heat, allowing moisture to easily penetrate and damage the interfacial bonding, reducing the adhesion between the epoxy resin and metal components, leading to adhesive layer detachment and shortening the lifespan of electronic devices.

[0003] Existing modification techniques for epoxy resin adhesives often focus on optimizing a single property. For example, adding small-molecule amine curing agents can improve heat resistance, but it also increases brittleness. Another approach is to use rubber elastomers or core-shell particle physical blends in epoxy resins to improve toughness, but this can reduce bond strength. Hydrophobic modification often leads to decreased interfacial compatibility. Furthermore, epoxy resin curing typically requires high temperatures, which can damage the substrate and cause thermal deformation. Small-molecule accelerators are often added to lower the curing temperature and time and improve curing efficiency, but these small molecules are prone to migration and thermal volatilization, creating new problems. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, the present invention provides a high-adhesion toughened epoxy resin adhesive and its preparation method. By using long-chain modified polyimide as a curing agent, a semi-interpenetrating network structure is formed with epoxy resin, thereby improving the impact toughness, bonding strength and reducing the initial curing temperature of the epoxy resin adhesive.

[0005] This invention is achieved through the following technical solution:

[0006] A high-adhesion toughening epoxy resin adhesive, comprising the following components by weight: 100 parts epoxy resin, 5-8 parts modified silica, and 100-195 parts modified polyimide curing agent; wherein the modified polyimide curing agent is obtained by linear polycondensation of hydrophobic diamine and pyromellitic anhydride.

[0007] In one specific embodiment, the epoxy resin is a bisphenol A type epoxy resin, and the epoxy equivalent of the bisphenol A type epoxy resin is 450~550 g / eq.

[0008] In one specific embodiment, the modified silica is nano-silica with a surface treated with an aminosilane coupling agent, and the particle size of the nano-silica is 15~25 nm.

[0009] In one specific embodiment, the aminosilane coupling agent is 3-aminopropyltriethoxysilane.

[0010] In one specific embodiment, the hydrophobic diamine has the structural formula shown in Formula 1:

[0011] Formula 1.

[0012] In one specific embodiment, the preparation of the modified polyimide curing agent includes the following steps:

[0013] S1. Dissolve 2,5-diaminobenzoic acid in anhydrous dichloromethane, place in an ice bath, and add an organic base and ditert-butyl dicarbonate sequentially: stir at room temperature for 8-12 hours; quench, extract, and purify by column chromatography to obtain product A;

[0014] S2. Under nitrogen atmosphere, the acid-binding agent and (3,3,3-trifluoropropyl)dichloromethylsilane were dissolved in anhydrous toluene; the temperature was raised to 60-80 °C, and a toluene solution of 2,4,6-tris(dimethylaminomethyl)phenol was added dropwise with stirring. After the addition was complete, stirring was continued for 11-16 hours; the product was then cooled, concentrated, and purified by column chromatography to obtain product B.

[0015] S3. Dissolve product B and the acid-binding agent in anhydrous THF and place in an ice bath; then add product A and react for 5-8 hours; cool and purify by column chromatography to obtain product C.

[0016] S4. Dissolve product C in anhydrous dichloromethane, place in an ice bath, add triethylamine; add trimethylsilyl trifluoromethanesulfonate dropwise and stir for 0.5-2 hours; add saturated NaHCO3 solution, concentrate the organic phase, purify by column chromatography, and dry to obtain hydrophobic diamine;

[0017] S5. Under nitrogen protection, hydrophobic diamine is dissolved in anhydrous DMAc; pyromellitic anhydride is added, and the mixture is reacted at 0-25 °C for 20-24 hours; acetic anhydride and pyridine are added, and the mixture is heated to 100-125 °C and reacted for 2-6 hours; the mixture is cooled, precipitated with ethanol, and dried to obtain the modified polyimide curing agent.

[0018] In one specific embodiment, the organic base in step S1 is triethylamine, and the amount used is 3-4 times the molar amount of 2,5-diaminobenzoic acid; the amount of ditert-butyl dicarbonate is 2.4-3 times the molar amount of 2,5-diaminobenzoic acid.

[0019] In one specific embodiment, the amount of 2,4,6-tris(dimethylaminomethyl)phenol used in step S2 is 0.95-1 times the molar amount of (3,3,3-trifluoropropyl)dichloromethylsilane; the acid-binding agent in steps S2 and S3 is N,N-diisopropylethylamine or triethylamine, and the amount used is 1.1-1.5 times the molar amount of (3,3,3-trifluoropropyl)dichloromethylsilane.

[0020] In one specific embodiment, the amount of product B used in step S3 is 0.95-1 times the molar amount of product A; the amount of acid-binding agent used is 1.1-1.5 times the molar amount of product A.

[0021] In one specific embodiment, the amount of triethylamine used in step S4 is 3-4 times the molar amount of product C; the amount of trimethylsilyl trifluoromethanesulfonate used is 2.4-3 times the molar amount of product C.

[0022] In one specific embodiment, the amount of hydrophobic diamine used in step S5 is 1.6-2.55 times the molar amount of pyromellitic anhydride; the amount of acetic anhydride used is 2-4 times the molar amount of pyromellitic anhydride; the amount of pyridine used is 0.2-1 times the molar amount of pyromellitic anhydride; and the number average molecular weight of the modified polyimide curing agent is 2000-3500 g / mol.

[0023] Another objective of this invention is to protect a method for preparing a high-adhesion toughened epoxy resin adhesive, comprising the following steps: mixing epoxy resin and modified silica in a mixer at 100-250 r / min for 5-10 minutes; adding a modified polyimide curing agent and mixing at 300-450 r / min for 10-15 minutes; transferring to a vacuum drying oven and degassing at room temperature under -0.09-0.1 MPa for 10-15 minutes to obtain a high-adhesion toughened epoxy resin adhesive.

[0024] Beneficial effects

[0025] This invention provides a high-adhesion toughened epoxy resin adhesive and its preparation method. The high-adhesion toughened epoxy resin adhesive incorporates a modified polyimide obtained by linear polycondensation of a hydrophobic diamine and pyromellitic anhydride as a curing agent. By using the long-chain modified polyimide as a curing agent, the polymer can form a semi-interpenetrating network structure with the epoxy resin. When cracks are generated under external force, this network can bridge and anchor cracks, bearing stress and dissipating energy. It can also synergistically work with nano-silica particles to prevent crack propagation. Furthermore, the chain segments dissipate energy through slippage and tensile stress, thus imparting impact toughness to the adhesive layer. Additionally, by introducing polar imide bonds, the hydroxyl groups generated from the crosslinking of the epoxy resin and the curing agent can form hydrogen bonds with the hydroxyl groups or oxides on the surface of the metal substrate, thereby improving the adhesive layer's bonding strength. Simultaneously, hydrophobic fluorosilicone segments are uniformly dispersed in the adhesive layer, forming a continuous hydrophobic interface. This results in a highly dense adhesive layer that effectively prevents moisture intrusion and maintains long-term high bonding strength. Furthermore, in the modified polyimide chain, the tertiary amine's N contains lone pair electrons, which can form coordinate bonds with the epoxy group, weakening the CO bond on the epoxy ring, reducing the ring-opening activation energy of the epoxy bond, accelerating the ring-opening reaction of the curing agent, lowering the initial curing temperature, thereby increasing the curing rate, and avoiding the migration and volatilization of the accelerator. Attached Figure Description

[0026] Figure 1 The synthetic route for modified polyimide curing agents;

[0027] Figure 2 The 1H NMR spectrum of product B is shown below.

[0028] Figure 3 The hydrogen nuclear magnetic resonance spectrum of a hydrophobic diamine;

[0029] Figure 4 Infrared spectra of the modified polyimide curing agent and epoxy resin adhesive cured samples in Example 1. Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise specified, the experimental methods used in the embodiments are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0032] The raw materials used in the examples and comparative examples are described below:

[0033] Epoxy resin 1: Model NPES-901, epoxy equivalent 450-500 g / eq, purchased from Shenzhen Jiadida New Material Technology Co., Ltd.

[0034] Epoxy resin 2: Model HY-901L, epoxy equivalent 460-490 g / eq, purchased from Anhui Hengyuan Technology Co., Ltd.

[0035] Epoxy resin 3: Model HY011, epoxy equivalent 455~550 g / eq, purchased from Anhui Hengyuan Technology Co., Ltd.

[0036] Modified polyimide curing agent 1: self-made, preparation method is as follows:

[0037] S1. Dissolve 2,5-diaminobenzoic acid (1 mol equivalent) in anhydrous dichloromethane, heat to 0 °C in an ice bath, and then add triethylamine (3.5 mol equivalent) and di-tert-butyl dicarbonate (2.8 mol equivalent) sequentially. Slowly raise the temperature to room temperature and stir the reaction for 10 hours. Quench the reaction with saturated ammonium chloride solution, extract the organic phase, wash with saturated sodium bicarbonate solution, concentrate, and purify by column chromatography to obtain product A, with a yield of 98%.

[0038] S2. Under nitrogen atmosphere, (3,3,3-trifluoropropyl)dichloromethylsilane (1 molar equivalent) and N,N-diisopropylethylamine (1.2 molar equivalent) were dissolved in anhydrous toluene and stirred until dissolved. The temperature was raised to 75 °C, and a toluene solution of 2,4,6-tris(dimethylaminomethyl)phenol (0.95 molar equivalent) was added dropwise with stirring. After the addition was complete, stirring was continued for 16 hours to complete the reaction. The mixture was cooled, filtered, the filtrate was concentrated, and purified by column chromatography to obtain product B, with a yield of 86%.

[0039] S3. Dissolve product B (0.95 molar equivalents) and N,N-diisopropylethylamine (1.3 molar equivalents) in anhydrous THF and in an ice bath; then add product A (1 molar equivalent) and react for 7 hours; cool and purify by column chromatography to obtain product C, yield 93%;

[0040] S4. Dissolve product C (1 molar equivalent) in anhydrous dichloromethane in an ice bath, add triethylamine (3.5 molar equivalents); then slowly add trimethylsilyl trifluoromethanesulfonate (2.8 molar equivalents) and stir for 2 hours; add saturated NaHCO3 solution, concentrate the organic phase, purify by column chromatography, concentrate, and dry to obtain hydrophobic diamine, yield 97%;

[0041] S5. Dissolve hydrophobic diamine (2 molar equivalents) in anhydrous DMAc; add pyromellitic anhydride (1 molar equivalent) and react at 0 °C for 24 hours; add acetic anhydride (2.4 molar equivalents) and pyridine (0.5 molar equivalents), heat to 110 °C and react for 6 hours; cool, precipitate with ethanol and wash repeatedly, dry at 60 °C for 24 hours to obtain modified polyimide curing agent 1 with a number average molecular weight of 2500 g / mol.

[0042] Modified polyimide curing agent 2: self-made. The preparation method is the same as that of modified polyimide curing agent 1, except that the amount of hydrophobic diamine is adjusted to 2.55 molar equivalents. The number average molecular weight of modified polyimide curing agent 2 is 2000 g / mol.

[0043] Modified polyimide curing agent 3: self-made. The preparation method is the same as that of modified polyimide curing agent 1, except that the amount of hydrophobic diamine is adjusted to 1.6 molar equivalents. The number average molecular weight of modified polyimide curing agent 3 is 3500 g / mol.

[0044] Modified polyimide curing agent 4: self-made. The preparation method is the same as that of modified polyimide curing agent 1, except that 2,4,6-tris(dimethylaminomethyl)phenol in step S2 is replaced with phenol.

[0045] Modified polyimide curing agent 5: self-made. The preparation method is the same as that of modified polyimide curing agent 1, except that (3,3,3-trifluoropropyl)dichloromethylsilane in step S2 is replaced with N-butylmethylsilicon chloride.

[0046] Modified polyimide curing agent 6: self-made. The preparation method is the same as that of modified polyimide curing agent 1. The difference is that steps S1, S2, S3 and S4 are not performed, and the hydrophobic diamine in step S5 is replaced with m-phenylenediamine, and the amount is adjusted to 1.27 molar equivalents.

[0047] Unless otherwise specified, all components and raw materials used in the embodiments and comparative examples of this invention are commercially available, and the same type of components and raw materials are used in each parallel experiment.

[0048] Examples and Comparative Examples

[0049] A high-adhesion toughening epoxy resin adhesive, the weight parts of which are shown in Table 1, is prepared by the following method:

[0050] Epoxy resin and modified silica were mixed in a mixer at 250 r / min for 8 minutes; modified polyimide curing agent was added and the mixture was stirred at 450 r / min for 12 minutes; the mixture was then transferred to a vacuum drying oven and degassed at room temperature under 0.1 MPa for 15 minutes to obtain a high-adhesion toughened epoxy resin adhesive.

[0051] Table 1. High-adhesion toughened epoxy resin adhesives (parts by weight)

[0052]

[0053] The high-adhesion toughened epoxy resin adhesive prepared in the examples and comparative examples was subjected to the following performance tests, and the results are shown in the figure and table 2, respectively.

[0054] 1. Proton NMR spectroscopy: The synthesized product B and the hydrophobic diamine sample were dissolved in deuterated DMSO to prepare solutions with a concentration of 1.0 wt%. The NMR spectra of the samples were measured using a proton NMR spectrometer at 400 MHz. The results are as follows: Figure 2 , Figure 3 As shown, the integral number is consistent with the hydrogen number of products A and B, and the chemical shift is consistent with its chemical environment, indicating that the target product was synthesized.

[0055] 2. Infrared Spectroscopy: The modified polyimide curing agent and epoxy resin adhesive cured samples from Example 1 were mixed with potassium bromide at a ratio of 1:50 to prepare a pellet. An Avatar 380 spectrometer was used for this test. Before testing, a blank background was scanned, followed by the placement of the pellet for testing. The scanning range was 500-4000 cm⁻¹. -1 The result is as follows Figure 4 As shown.

[0056] 3. Glass transition temperature (Tg) test: The glass transition temperature of the epoxy resin cured samples was determined using a TA Q200 differential scanning calorimeter. Epoxy resin cured samples were prepared by curing the epoxy resin at 130 ℃ for 30 minutes. The heating rate during testing was 10 K / min, the N2 flow rate was 50 mL / min, and the scanning range was 40-220 ℃.

[0057] 4. Non-isothermal curing kinetics test: The isothermal curing behavior of the epoxy resin was detected using a TA Q200 differential scanning calorimeter. 10 mg of epoxy resin was placed in an aluminum crucible, and dynamic scanning was performed under a N2 atmosphere at a rate of 50 mL / min, with a heating rate of 10 K / min and a scanning temperature range of 40-220 ℃. The obtained DSC curves were analyzed using TA Universal Analysis software to obtain the characteristic temperatures during the curing process, i.e., the curing reaction initiation temperature T. i Peak temperature T p End temperature T f .

[0058] 5. Bonding strength: Two 100*25*1.6 mm aluminum substrates were prepared according to GB7124-2008 standard and bonded together with epoxy resin adhesive. The bonding surface length was 12.5 mm and the epoxy resin adhesive thickness was 0.2 mm. The bonding strength was tested using a universal testing machine, with the failure time controlled between 65 s ± 20 s and the loading rate 10 mm / min.

[0059] 6. Impact resistance: The impact strength of the epoxy resin cured sample was tested according to GB / T 1843-2008 standard. An 80*10*4 mm notched epoxy resin cured sample with a notch depth of 2 mm was prepared and tested using a 2.75 J pendulum impact tester. The impact absorbed energy was recorded and the impact strength was calculated.

[0060] 7. Waterproof performance test: The test shall be conducted in accordance with GB / T 2423.3 standard. The epoxy resin adhesive cured sample shall be placed in a damp heat aging chamber and aged for 1000 hours at 85 ℃ and 85%RH. After being taken out, it shall be placed in an environment of 23 ℃ and 50%RH for 24 hours to test the bond strength retention rate.

[0061] Table 2 Performance test results of high-adhesion toughened epoxy resin adhesive

[0062]

[0063] From the appendix Figure 4 It can be seen that in the spectrum of the modified polyimide curing agent, the peak appears at 2980-2830 cm⁻¹. -1 The stretching vibrations attributed to CH2 peak at 1411 cm⁻¹. -1 1260 cm -1 This is the absorption signal of Si-CH3 in (3,3,3-trifluoropropyl)dichloromethylsilane, with a peak at 962 cm⁻¹. -1 The absorption signal is near Si-O-Ph; 3400-3300 cm⁻¹ -1 The broad peak at 1552 cm⁻¹ is a characteristic signal of the terminal amino group. -1 The vibration belongs to the -CN stretching vibration; the peak occurs at 1776 cm. -1 and 1728 cm -1 The characteristic signal is the -C=O on the imide ring, 1378 cm⁻¹ -1 It is a characteristic signal of the imide five-membered ring-CNC, 762 cm⁻¹ -1 The vicinity is characterized by the deformation vibration of the imide five-membered ring; however, there is no vibration at 1856 cm⁻¹. -1 1765 cm -1The presence of a -C=O characteristic signal belonging to pyromellitic anhydride indicates the successful synthesis of the modified polyimide curing agent.

[0064] In the spectrum of the cured epoxy resin sample, the range is 3650-3450 cm⁻¹. -1 Characteristic signals belonging to hydroxyl groups in epoxy resin were observed nearby at 1245 cm. -1 Stretching vibrations belonging to the epoxy resin Ph-OC were observed at 831 cm⁻¹. -1 Characteristic signals belonging to the para-phenylene oxide of epoxy resin were observed, and the range was 3400-3300 cm. -1 The signal at the terminal amino group weakened and did not reach 913 cm. -1 Characteristic peaks belonging to epoxy groups were observed nearby, along with other signals from the modified polyimide, indicating that the modified polyimide successfully underwent a crosslinking reaction with the epoxy resin, and the epoxy resin adhesive cured sample was successfully prepared.

[0065] As shown in Table 2, by introducing polar imide bonds, the hydroxyl groups generated by the crosslinking of epoxy resin and curing agent can form hydrogen bonds with the hydroxyl groups or oxides on the surface of the metal substrate, thereby increasing the bonding strength. In Example 4, the modified polyimide curing agent, with its smaller molecular weight, exhibits good compatibility with epoxy resin and can quickly wet the substrate and form chemical bonds. However, the short molecular chain leads to insufficient cohesive strength of the adhesive layer, resulting in decreased bonding strength. In contrast, the modified polyimide curing agent in Example 5 has a larger molecular weight, resulting in poorer compatibility with epoxy resin and a tendency for molecular chain aggregation. This leads to micro-defects within the adhesive layer, insufficient molecular chain diffusion at the interface, weakened interfacial interaction, and decreased bonding strength. Comparative Examples 3 and 4 lack polar groups that can interact with the substrate, thus significantly reducing their bonding strength.

[0066] Meanwhile, in the embodiments, when long-chain modified polyimide is used as a curing agent, on the one hand, the polymer can form a semi-interpenetrating network structure with the epoxy resin. When cracks are generated by external force, it can bridge and rivet the cracks, bear stress to dissipate energy, and prevent crack propagation. On the other hand, the chain segments slide and stretch under force to dissipate energy, thereby improving impact toughness. Among them, in Example 4, due to the short molecular chain, it cannot effectively absorb energy, resulting in a decrease in impact strength. In Example 5, the molecular chain is prone to agglomeration, forming stress concentration points, which actually reduces performance. Comparative Example 3 lacks large steric hindrance side chains, and the prepared modified polyimide chain is prone to agglomeration and cannot be well inserted into the epoxy resin crosslinking network, thus consuming less energy. In contrast, Comparative Example 4 uses small molecule m-phenylenediamine as a curing agent, resulting in a rigid network with no slip space for the molecular chain. There is no energy consumption mechanism when cracks propagate, resulting in extremely low impact strength.

[0067] Table 2 also shows that, compared to Comparative Examples 2-4, when the hydrophobic component (3,3,3-trifluoropropyl)dichloromethylsilane was introduced, the fluorosilicone segments in the examples were uniformly dispersed in the adhesive layer, forming a continuous hydrophobic interface. The adhesive layer had high density, effectively preventing moisture intrusion and maintaining long-term high bonding strength. In Example 4, the fluorosilicone segment density was low, and the surface energy of the adhesive layer was only reduced to a limited extent, allowing moisture to easily penetrate through the adhesive layer. In Example 5, molecular chain aggregation caused tiny gaps to form inside the adhesive layer, allowing moisture to penetrate to the interface and destroying the bonding effect.

[0068] Furthermore, when grafting accelerators into modified polyimide chains, the nitrogen atom of the tertiary amine contains a lone pair of electrons, which can form a coordination bond with the epoxy group, weakening the CO bond on the epoxy ring, lowering the ring-opening activation energy of the epoxy bond, accelerating the ring-opening reaction of the curing agent, lowering the initial curing temperature, and thus increasing the curing rate. Example 4 shows that the low molecular weight modified polyimide contains more tertiary amine per unit mass, resulting in higher catalytic efficiency and a lower initial curing temperature; Example 5 shows a decrease in the unit concentration of tertiary amine, leading to an increase in the initial curing temperature. In contrast, Comparative Example 4 uses a curing agent with low steric hindrance, resulting in a large contact area with the epoxy resin, thus achieving a very low initial curing temperature and high curing efficiency.

[0069] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A high bond toughened epoxy resin glue, characterized by, The product comprises, by weight, the following components: 100 parts epoxy resin, 5-8 parts modified silica, and 100-195 parts modified polyimide curing agent; the modified polyimide curing agent is obtained by linear polycondensation of hydrophobic diamine and pyromellitic anhydride; the amount of hydrophobic diamine is 1.6-2.55 times the molar amount of pyromellitic anhydride; the structural formula of the hydrophobic diamine is shown in Formula 1. Formula 1.

2. The high-adhesion toughened epoxy resin adhesive as described in claim 1, characterized in that, The modified silica is nano-silica with a surface treated with an aminosilane coupling agent, and the particle size of the nano-silica is 15~25 nm.

3. The high-adhesion toughened epoxy resin adhesive as described in claim 1, characterized in that, The epoxy resin is a bisphenol A type epoxy resin, and the epoxy equivalent of the bisphenol A type epoxy resin is 450~550 g / eq.

4. The high-adhesion toughened epoxy resin adhesive as described in claim 1, characterized in that, The preparation of the modified polyimide curing agent includes the following steps: S1. Dissolve 2,5-diaminobenzoic acid in anhydrous dichloromethane, place in an ice bath, and add an organic base and ditert-butyl dicarbonate sequentially: stir at room temperature for 8-12 hours; quench, extract, and purify by column chromatography to obtain product A; S2. Under nitrogen atmosphere, the acid-binding agent and (3,3,3-trifluoropropyl)dichloromethylsilane were dissolved in anhydrous toluene; the temperature was raised to 60-80 °C, and a toluene solution of 2,4,6-tris(dimethylaminomethyl)phenol was added dropwise with stirring. After the addition was complete, stirring was continued for 11-16 hours; the product was then cooled, concentrated, and purified by column chromatography to obtain product B. S3. Dissolve product B and the acid-binding agent in anhydrous THF and place in an ice bath; then add product A and react for 5-8 hours; cool and purify by column chromatography to obtain product C. S4. Dissolve product C in anhydrous dichloromethane, place in an ice bath, add triethylamine; add trimethylsilyl trifluoromethanesulfonate dropwise and stir for 0.5-2 hours; add saturated NaHCO3 solution, concentrate the organic phase, purify by column chromatography, and dry to obtain hydrophobic diamine; S5. Under nitrogen protection, hydrophobic diamine is dissolved in anhydrous DMAc; pyromellitic anhydride is added, and the mixture is reacted at 0-25 °C for 20-24 hours; acetic anhydride and pyridine are added, and the mixture is heated to 100-125 °C and reacted for 2-6 hours; the mixture is cooled, precipitated with ethanol, and dried to obtain the modified polyimide curing agent.

5. The high-adhesion toughened epoxy resin adhesive as described in claim 4, characterized in that, The organic base in step S1 is triethylamine, used in an amount 3-4 times the molar amount of 2,5-diaminobenzoic acid; the amount of ditert-butyl dicarbonate is 2.4-3 times the molar amount of 2,5-diaminobenzoic acid; the amount of 2,4,6-tris(dimethylaminomethyl)phenol in step S2 is 0.95-1 times the molar amount of (3,3,3-trifluoropropyl)dichloromethylsilane; the acid-binding agent in steps S2 and S3 is N,N-diisopropylethylamine or triethylamine, used in an amount 1.1-1.5 times the molar amount of (3,3,3-trifluoropropyl)dichloromethylsilane.

6. The high-adhesion toughened epoxy resin adhesive as described in claim 4, characterized in that, In step S3, the amount of product B is 0.95-1 times the molar amount of product A; the amount of the acid-binding agent is 1.1-1.5 times the molar amount of product A; in step S4, the amount of triethylamine is 3-4 times the molar amount of product C; and the amount of trimethylsilyl trifluoromethanesulfonate is 2.4-3 times the molar amount of product C.

7. The high-adhesion toughened epoxy resin adhesive as described in claim 4, characterized in that, The amount of acetic anhydride used is 2-4 times the molar amount of pyromellitic anhydride; the amount of pyridine used is 0.2-1 times the molar amount of pyromellitic anhydride; and the number average molecular weight of the modified polyimide curing agent is 2000-3500 g / mol.

8. The method for preparing the high-adhesion toughened epoxy resin adhesive as described in claim 1, characterized in that, The process includes the following steps: placing epoxy resin and modified silica in a mixer and stirring for 5-10 minutes at 100-250 r / min to mix them thoroughly; adding modified polyimide curing agent and stirring for 10-15 minutes at 300-450 r / min; transferring to a vacuum drying oven and degassing at room temperature under -0.09-0.1 MPa for 10-15 minutes to obtain a high-adhesion toughened epoxy resin adhesive.

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