Long pot life dual-cure interpenetrating network type one-component epoxy resin adhesive, preparation method and application

Abstract

The present application relates to the technical field of epoxy resin adhesive, in particular to a long applicable period dual-curing interpenetrating network type one-component epoxy resin adhesive, a preparation method and application, the adhesive is composed of 100 parts of E-51 epoxy resin, 15-35 parts of modified imidazole curing agent, 10-40 parts of active diluent, 0.2-2.0 parts of free radical polymerization initiator by weight fraction; The modified imidazole curing agent has the functions of latency and toughening. The one-component epoxy adhesive of the present application has a long room temperature storage period, which can reach 570-632 hours; only heating is needed to simultaneously realize free radical polymerization curing and thermal curing, forming an interpenetrating network type resin material with high strength and high toughness; there is no strict requirement for raw materials and packaging substrates, overcoming many defects existing in traditional dual-curing epoxy adhesives.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin adhesive technology, specifically to a long-life, dual-curing, interpenetrating network type single-component epoxy resin adhesive, its preparation method, and its application. Background Technology

[0002] Adhesives composed of basic components such as epoxy resin, curing agent, and toughening agent have advantages such as strong adhesion, chemical corrosion resistance, and excellent electrical insulation properties, and are widely used in electronic components, integrated circuits, circuit board packaging, and other fields. According to packaging form, epoxy resin adhesives are divided into single-component and two-component types. Single-component adhesives are thermosetting adhesives where epoxy resin and a latent curing agent are pre-mixed evenly and packaged in a single container. Single-component adhesives can be stored at room temperature for a long time and do not require re-weighing and mixing before use; they are ready to use immediately. Heating is sufficient to activate the reaction between the curing agent and epoxy resin, curing them into a three-dimensional cross-linked network structure polymer material with high adhesive strength. To ensure storage stability and curing strength, the curing agent in a one-component epoxy adhesive should meet the following requirements: it should have high latency or stability at room temperature, the activation temperature should be as low as possible, and it should have high reactivity during the curing process after activation. The stability required for room temperature storage and the high reactivity required during the curing process are inherently a pair of mutually restrictive and difficult-to-reconcile contradictions. Therefore, for one-component epoxy adhesives, the most core and critical technology lies in selecting a latent curing agent that balances stability and curing activity.

[0003] In the existing technology, most single-component epoxy resin adhesives use imidazole curing agents or imidazole derivatives as latent curing agents. Although they can meet certain application requirements, they have the following problems: (1) Most imidazole curing agents, such as imidazole, 2-methylimidazole and 2-phenylimidazole, are solid powders at room temperature, which have poor compatibility with epoxy resin, resulting in uneven curing of the adhesive and deterioration of various properties; (2) Imidazole curing agents have high reactivity, resulting in a short pot life of the adhesive and failing to meet the requirements for room temperature storage stability; (3) A few Imidazole curing agents of various types, such as 2-ethyl-4-methylimidazole and 1-cyanoethyl-2-ethyl-4-methylimidazole, are liquid at room temperature, but their synthesis routes are complex and expensive, leading to an increase in the overall cost of adhesives; (4) Most of the existing modified imidazole curing agents with a certain degree of latency have activation temperatures higher than 120°C, and the adhesive needs to be cured under high temperature conditions, which is not suitable for heat-sensitive application scenarios; (5) Epoxy resin materials cured by imidazole curing agents are brittle and lack toughness, making them difficult to withstand impact and tearing.

[0004] To improve the impact resistance of cured epoxy resin adhesives, toughening agents are often used to improve the toughness of the cured resin and enhance the material's ability to withstand impact loads. Toughening agents include inert toughening agents and reactive toughening agents. Inert toughening agents do not participate in the resin curing reaction and include dibutyl phthalate, dioctyl phthalate, nitrile rubber, polybutadiene, and various inorganic nanomaterials such as nano-silica and calcium carbonate. Reactive toughening agents participate in the resin curing reaction and are relatively fewer in variety, such as carboxyl-terminated nitrile rubber, carboxyl-terminated polybutadiene, and liquid polysulfide rubber. Small-molecule toughening agents such as dibutyl phthalate and dioctyl phthalate are prone to migration and can be dissolved or extracted by the medium in which the material is located, causing secondary pollution. Inorganic nanomaterials significantly increase the viscosity of the resin system, degrading the adhesive's workability. Acrylonitrile rubber, polybutadiene, and carboxyl-terminated polybutadiene and carboxyl-terminated nitrile rubber with functional groups have poor compatibility with epoxy resins and are prone to phase separation, leading to a decrease in the modulus and strength of the cured material. Currently, there are relatively few reports on curing agents with toughening properties.

[0005] To improve the mechanical properties of adhesives, dual-curing technology is often used in existing technologies. The publicly disclosed dual-curing epoxy adhesives have the following problems in practical applications: (1) They require a variety of active monomers and photoinitiators, and the process is complicated. Not only do they require expensive UV curing equipment for the initial free radical polymerization and curing of active monomers, but they also require high-temperature heating equipment to heat to about 150°C for the later thermal curing of epoxy resin. The equipment, raw materials and energy consumption are large and the cost is high; (2) They have strict requirements for raw materials and construction substrates and are too selective: Traditional dual-curing adhesives require that the adhesive must have high light transmittance and that the composition of the adhesive cannot contain any substances that absorb or scatter ultraviolet light. The pigments and fillers (difficult to avoid in actual use); not suitable for the encapsulation of heat-sensitive electronic components and plastic parts, because high temperature will directly cause such devices to fail; also not suitable for the encapsulation of products with complex three-dimensional structures, as deep holes and narrow slits in such products will form shadow areas for light and cannot be effectively photocured; (3) the photocurable network and the thermocurable network cannot be formed simultaneously. The photocurable network formed in the early stage will hinder the movement and diffusion of thermocurable network component molecules, resulting in uneven and insufficient curing, which will eventually generate internal stress in the material matrix, eventually leading to material warping, cracking and reduced strength. To this end, a long-term dual-curing interpenetrating network type single-component epoxy resin adhesive, preparation method and application are proposed. Summary of the Invention

[0006] To address the problems of existing single-component epoxy adhesives, such as short pot life, high cost, high curing temperature, poor toughness of cured products, and unsatisfactory toughening effect; and traditional dual-curing epoxy adhesives, such as high equipment, raw material, and energy consumption, high cost, high selectivity to raw materials and construction substrates, and unsatisfactory mechanical properties, this invention provides a long-pot life dual-curing interpenetrating network type single-component epoxy resin adhesive, its preparation method, and its application.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a long-lasting, dual-curing, interpenetrating network type single-component epoxy resin adhesive, comprising, by weight: 100 parts of E-51 epoxy resin, 15-35 parts of modified imidazole curing agent, 10-40 parts of reactive diluent, and 0.2-2.0 parts of free radical polymerization initiator;

[0008] The synthetic formulation of the modified imidazole curing agent includes, by weight, 0.8–1.2 parts propylene carbonate, 0.8–1.2 parts imidazole, 0.8–1.2 parts polyethylene glycol monomethyl ether, and 1 part organic acid anhydride, as well as antioxidants and catalysts by weight percentage; the preparation process of the modified imidazole curing agent includes the following steps:

[0009] S1, propylene carbonate and imidazole were added to a three-necked flask equipped with a reflux condenser according to the proportion of the synthesis formula, and reacted at 140°C for 4 hours to obtain hydroxypropyl-substituted imidazole for later use.

[0010] S2, polyethylene glycol monomethyl ether, organic acid anhydride and antioxidant are added to a three-necked flask equipped with a reflux condenser and a water separator according to the proportion of the synthesis formula. After reacting at 130-170℃ for 4-6 hours, organic acid anhydride-polyethylene glycol monomethyl ether monoester compound is obtained for later use.

[0011] S3, the hydroxypropyl-substituted imidazole obtained in step S1, the organic acid anhydride-polyethylene glycol monomethyl ether monoester compound obtained in step S2, and the catalyst are added to a three-necked flask equipped with a reflux condenser and a water separator, and reacted at 180-205°C for 5.5-8 hours to obtain the modified imidazole curing agent.

[0012] Preferably, the reactive diluent is glycidyl methacrylate containing carbon-carbon double bonds and epoxy groups; and the free radical polymerization initiator is benzoyl peroxide.

[0013] Preferably, in step S1, the organic acid anhydride is methyl nadic anhydride.

[0014] Preferably, in step S2, the polyethylene glycol monomethyl ether raw material used is in a liquid state at room temperature.

[0015] Preferably, in step S2, the antioxidant is 2,6-di-tert-butyl-p-cresol, and the amount used is 0.5% of the total mass of the three substances: the hydroxypropyl-substituted imidazole product obtained in step S1, the polyethylene glycol monomethyl ether raw material used in step S2, and the organic acid anhydride.

[0016] Preferably, in step S3, the catalyst is p-toluenesulfonic acid, and the amount used is 1% of the total mass of the three substances: the hydroxypropyl-substituted imidazole product obtained in step S1, the polyethylene glycol monomethyl ether raw material used in step S2, and the organic acid anhydride.

[0017] The present invention also discloses a method for preparing the adhesive, comprising the following steps:

[0018] A1. At room temperature, dissolve the free radical polymerization initiator in the reactive diluent according to the specified ratio to obtain the reactive diluent solution for later use.

[0019] A2, then mix E-51 epoxy resin, modified imidazole curing agent and reactive diluent solution in proportion, then stir and degas, and after mixing evenly, obtain long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0020] This invention also discloses the application of a long-term, dual-curing, interpenetrating network type single-component epoxy resin adhesive in epoxy resin curing, wherein the curing process conditions are 90–110°C for 2–4 hours.

[0021] The technical concept of this invention is as follows: Glycidyl methacrylate is a low-viscosity liquid at room temperature. Its molecular structure contains C=C double bonds and epoxy groups, exhibiting good compatibility with epoxy resin. This effectively reduces the viscosity of epoxy resin adhesives and improves the workability of the adhesive. Under the action of a free radical polymerization initiator, the C=C double bonds in glycidyl methacrylate can undergo free radical polymerization, and its epoxy groups can also polymerize under the action of imidazole curing agents. Therefore, under the combined action of the free radical polymerization initiator and the modified imidazole curing agent, the glycidyl methacrylate-epoxy resin adhesive can form an interpenetrating network after free radical curing and thermosetting. This allows the two polymer networks to interpenetrate and permanently entangle at the molecular level, thereby efficiently transferring stress, delaying material failure, and improving the tensile strength of the cured adhesive.

[0022] Polyethylene glycol monomethyl ether contains flexible long chains and terminal hydroxyl groups in its molecular structure. After reacting with Nadic anhydride, it generates a monoester. Propylene carbonate reacts with imidazole to generate hydroxypropyl imidazole, and the reaction process is shown in the following formula (1). After the polyethylene glycol monomethyl ether-organic acid anhydride monoester undergoes an esterification reaction with hydroxypropyl imidazole, a long flexible chain is introduced onto the imidazole ring through ester bonds. On the one hand, the long flexible chain can reduce the reactivity of the imidazole ring through steric hindrance and its encapsulation of the imidazole ring, so that the modified imidazole curing agent has good stability under room temperature conditions, thus giving the adhesive a long service life. Under heating conditions, the flexible long chains bonded to the curing agent molecule are prone to conformational rearrangement, thereby unsealing the imidazole ring and initiating the curing reaction of the epoxy groups in epoxy resin and glycidyl methacrylate. On the other hand, the long flexible chain linked to the imidazole ring can also toughen the cured resin matrix, so that it has good elongation at break while maintaining high strength.

[0023] (1).

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention provides an epoxy adhesive that combines high tensile strength and high fracture toughness. Upon heating, this adhesive undergoes both carbon-carbon double-bond free radical polymerization and epoxy group ring-opening polymerization for dual curing. An interpenetrating polymer network is formed by polymerizing epoxy resin and glycidyl methacrylate. The two networks are permanently interpenetrating, achieving molecular chain segment-level mixing and topological entanglement, resulting in high adhesive strength. Simultaneously, the long, flexible chains bonded to the modified imidazole curing agent molecules are also permanently bonded to the interpenetrating network matrix along with the modified imidazole curing agent. When the matrix material is subjected to stress, energy is absorbed and toughened through conformational rearrangement of the flexible polyethylene glycol ether chains on the curing agent molecules. This completely solves the problem of toughening agent migration and precipitation, and incompatibility leading to a decrease in material strength.

[0026] 2. The modified imidazole curing agent provided by this invention is liquid at room temperature and has excellent miscibility with epoxy resin. By grafting long flexible chains onto the imidazole ring through esterification, the reactivity of imidazole at room temperature is reduced, giving the epoxy resin adhesive a long pot life. When heated, the long flexible chains rearrange and expand, unblocking the imidazole ring, allowing the adhesive to cure quickly in the low-to-medium temperature range of 90-110°C. This achieves a balance between room temperature stability and rapid curing at medium temperatures.

[0027] 3. The long-term curing dual-curing interpenetrating network type single-component epoxy resin adhesive of the present invention does not require special equipment for curing. It only needs to be heated to no more than 120°C to simultaneously achieve free radical polymerization curing and thermal curing, ensuring that glycidyl methacrylate and epoxy resin are cured synchronously to form an interpenetrating network type polymer material with high strength and high toughness. It has no strict requirements on raw materials and encapsulation substrates, overcoming many defects of traditional dual-curing epoxy adhesives. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments, which illustrate the above and other technical features and advantages of the present invention. However, the following embodiments are merely preferred embodiments of the present invention and are not exhaustive.

[0029] I. Preparation of Modified Imidazole Curing Agent in Long-Lasting, Dual-Cure Interpenetrating Network Type One-Component Epoxy Resin Adhesive

[0030] Example 1:

[0031] S1, 0.8 parts of propylene carbonate and 0.8 parts of imidazole were added to a three-necked flask equipped with a reflux condenser and reacted at 140°C for 4 hours to obtain hydroxypropyl-substituted imidazole for later use.

[0032] S2, 1.2 parts of polyethylene glycol monomethyl ether, 1 part of methyl nadic anhydride, and the antioxidant 2,6-di-tert-butyl-p-cresol were added to a three-necked flask equipped with a reflux condenser and a water separator. After reacting at 130°C for 4 hours, a methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound was obtained for later use. The amount of 2,6-di-tert-butyl-p-cresol used was 0.5% of the total mass of the hydroxypropyl-substituted imidazole product obtained in step S1 and the three raw materials polyethylene glycol monomethyl ether and methyl nadic anhydride used in step S2.

[0033] S3, the hydroxypropyl-substituted imidazole obtained in step S1, the methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound obtained in step S2, and the p-toluenesulfonic acid catalyst are added to a three-necked flask equipped with a reflux condenser and a water separator, and reacted at 180°C for 5.5 hours to obtain a liquid, highly fluid modified imidazole curing agent; wherein, the amount of p-toluenesulfonic acid used is 1% of the total mass of the hydroxypropyl-substituted imidazole obtained in step S1, the polyethylene glycol monomethyl ether used in step S2, and the methyl nadic anhydride.

[0034] Example 2:

[0035] S1, 1.2 parts of propylene carbonate and 1.2 parts of imidazole were added to a three-necked flask equipped with a reflux condenser and reacted at 140°C for 4 hours to obtain hydroxypropyl-substituted imidazole for later use.

[0036] S2, 0.8 parts of polyethylene glycol monomethyl ether, 1 part of methyl nadic anhydride, and the antioxidant 2,6-di-tert-butyl-p-cresol were added to a three-necked flask equipped with a reflux condenser and a water separator. After reacting at 170°C for 5.5 hours, a methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound was obtained for later use. The amount of 2,6-di-tert-butyl-p-cresol used was 0.5% of the total mass of the hydroxypropyl-substituted imidazole product obtained in step S1 and the three raw materials polyethylene glycol monomethyl ether and methyl nadic anhydride used in step S2.

[0037] S3, the hydroxypropyl-substituted imidazole obtained in step S1, the methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound obtained in step S2, and the p-toluenesulfonic acid catalyst are added to a three-necked flask equipped with a reflux condenser and a water separator, and reacted at 190°C for 6 hours to obtain a liquid, highly fluid modified imidazole curing agent; wherein, the amount of p-toluenesulfonic acid used is 1% of the total mass of the hydroxypropyl-substituted imidazole obtained in step S1, the polyethylene glycol monomethyl ether used in step S2, and the methyl nadic anhydride.

[0038] Example 3:

[0039] S1, 0.9 parts of propylene carbonate and 0.9 parts of imidazole were added to a three-necked flask equipped with a reflux condenser and reacted at 140°C for 4 hours to obtain hydroxypropyl-substituted imidazole for later use.

[0040] S2, 1.1 parts of polyethylene glycol monomethyl ether, 1 part of methyl nadic anhydride, and the antioxidant 2,6-di-tert-butyl-p-cresol were added to a three-necked flask equipped with a reflux condenser and a water separator. After reacting at 160°C for 5.5 hours, a methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound was obtained for later use. The amount of 2,6-di-tert-butyl-p-cresol used was 0.5% of the total mass of the hydroxypropyl-substituted imidazole product obtained in step S1 and the three raw materials polyethylene glycol monomethyl ether and methyl nadic anhydride used in step S2.

[0041] S3, the hydroxypropyl-substituted imidazole obtained in step S1, the methyl nadic anhydride-polyethylene glycol monomethyl ether monoester compound obtained in step S2, and the p-toluenesulfonic acid catalyst are added to a three-necked flask equipped with a reflux condenser and a water separator, and reacted at 190°C for 6 hours to obtain a liquid, highly fluid modified imidazole curing agent; wherein, the amount of p-toluenesulfonic acid used is 1% of the total mass of the hydroxypropyl-substituted imidazole obtained in step S1, the polyethylene glycol monomethyl ether used in step S2, and the methyl nadic anhydride.

[0042] In the synthesis of the modified imidazole curing agent in the long-life dual-curing interpenetrating network type single-component epoxy adhesives in Examples 1-3 above, the amounts of each substance are expressed as parts by weight, and the formulation and process are shown in Table 1. The polyethylene glycol monomethyl ether raw material used has a weight-average molecular weight of 200 and is liquid at room temperature. The nuclear magnetic resonance hydrogen spectrum test shows that the number-average molecular weight of the polyethylene glycol monomethyl ether raw material is also about 200. Its amount of substance is obtained by dividing the mass by 200.

[0043] Table 1 - Synthesis formulations and processes of modified imidazole curing agents in Examples 1-3

[0044]

[0045] II. Preparation of Long-Lasting, Dual-Cure Interpenetrating Network Type One-Component Epoxy Resin Adhesive

[0046] Example 4:

[0047] A1. At room temperature, 0.5 parts of benzoyl peroxide (BPO) are dissolved in 10 parts of glycidyl methacrylate to obtain a glycidyl methacrylate solution for later use.

[0048] A2, add 100 parts of E-51 epoxy resin, 23.9 parts of the modified imidazole curing agent prepared in Example 3, and the glycidyl methacrylate solution prepared in step A1 into a degassing box, and stir and degas using a vacuum stirrer for 8 minutes to obtain a long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0049] Example 5:

[0050] A1, at room temperature, 1.5 parts of benzoyl peroxide were dissolved in 30 parts of glycidyl methacrylate to obtain a glycidyl methacrylate solution for later use.

[0051] A2, add 100 parts of E-51 epoxy resin, 23.9 parts of the modified imidazole curing agent prepared in Example 3, and the glycidyl methacrylate solution prepared in step A1 into a degassing box, and stir and degas using a vacuum stirrer for 8 minutes to obtain a long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0052] Example 6:

[0053] A1, at room temperature, 2.0 parts of benzoyl peroxide were dissolved in 40 parts of glycidyl methacrylate to obtain a glycidyl methacrylate solution for later use.

[0054] A2, add 100 parts of E-51 epoxy resin, 23.9 parts of the modified imidazole curing agent prepared in Example 3, and the glycidyl methacrylate solution prepared in step A1 into a degassing box, and stir and degas using a vacuum stirrer for 8 minutes to obtain a long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0055] Example 7:

[0056] A1, at room temperature, 0.5 parts of benzoyl peroxide are dissolved in 10 parts of glycidyl methacrylate to obtain a glycidyl methacrylate solution for later use.

[0057] A2, add 100 parts of E-51 epoxy resin, 16.04 parts of the modified imidazole curing agent prepared in Example 3, and the glycidyl methacrylate solution prepared in step A1 into a degassing box, and stir and degas using a vacuum stirrer for 8 minutes to obtain a long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0058] Example 8:

[0059] A1, at room temperature, 0.5 parts of benzoyl peroxide are dissolved in 10 parts of glycidyl methacrylate to obtain a glycidyl methacrylate solution for later use.

[0060] A2, add 100 parts of E-51 epoxy resin, 32.08 parts of the modified imidazole curing agent prepared in Example 3, and the glycidyl methacrylate solution prepared in step A1 into a degassing box, and stir and degas using a vacuum stirrer for 8 minutes to obtain a long-life dual-curing interpenetrating network type single-component epoxy resin adhesive.

[0061] The formulations of the long-life dual-curing interpenetrating network type single-component epoxy resin adhesives prepared in Examples 4 to 8 above are shown in Table 2. In all of them, the modified imidazole curing agent obtained in Example 3 is used, and the amount of each component is expressed in parts by weight.

[0062] Table 2 - Formulations of Long-Lasting Dual-Cure Interpenetrating Network One-Component Epoxy Resin Adhesives (Examples 4-8)

[0063]

[0064] III. Performance Testing of Long-Lasting, Dual-Cure Interpenetrating Network Type Single-Component Epoxy Resin Adhesives

[0065] 1. Room temperature storage period test

[0066] The room temperature gel time test was conducted with reference to the section on room temperature gel time testing in Chinese Patent CN202410603354.9. Adhesive materials for the room temperature storage period test of adhesives in Examples 4-6 were prepared according to the formulations shown in Table 3: Benzoyl peroxide was dissolved in glycidyl methacrylate to form a solution at room temperature; then, E-51 epoxy resin, the modified imidazole curing agent prepared in Example 3, the glycidyl methacrylate solution, and propylene glycol methyl ether were stirred and mixed evenly to obtain the adhesive materials for the room temperature storage period test of each example. Approximately 10g of each adhesive material for the room temperature storage period test was weighed, added to a transparent sample bottle, sealed, and stored at room temperature. The change in fluidity was observed, and the time taken from the completion of preparation to complete loss of fluidity was recorded as the room temperature storage period of each adhesive. The results are shown in Table 4.

[0067] 2. Mechanical property testing

[0068] The mechanical property testing was conducted with reference to the section on mechanical property testing in Chinese Patent CN202410603354.9. Long-life, double-curing, interpenetrating network, single-component epoxy resin adhesives prepared in Examples 4-8 were used. The adhesives were poured into a dumbbell-shaped polytetrafluoroethylene mold and cured at the temperatures and times shown in Table 4. After demolding, the samples were placed on a flat steel plate and then placed back into an oven at the original curing temperature for 20 minutes. After removal, they were allowed to cool naturally and left at room temperature for at least 24 hours. Tensile properties were tested using a universal testing machine according to national standard GB / T 1040.1-2018: the tensile rate was 5 mm / min, where the tensile strength was the maximum stress the sample could withstand before fracture, and the elongation at break was the ratio of the increase in gauge distance at fracture to the initial gauge length. The test results are shown in Table 4.

[0069] Table 3 - Adhesive formulations used for room temperature storage period testing of adhesives in Examples 4-6

[0070]

[0071] Table 4 - Performance test results of long-life dual-curing interpenetrating network type single-component epoxy resin adhesives in Examples 4-8

[0072]

[0073] In the preparation process of the adhesives and their room temperature storage test materials in Examples 4-8, whether vacuum stirring for degassing or simple stirring is used, the modified imidazole curing agent can be mixed quickly and evenly with components such as E-51 epoxy resin, and the resulting adhesive material always maintains a homogeneous state during storage, indicating that the modified imidazole curing agent of the present invention has good compatibility with components such as epoxy resin.

[0074] As shown in Table 4, the epoxy resin adhesive provided by this invention has a long room temperature storage period of 570–632 hours. When the adhesive is cured at 90–110°C for 2–4 hours, the tensile strength of the cured material reaches 83.4–90.1 MPa and the elongation at break reaches 11.5–14.0%. The presence of both high tensile strength and high elongation at break demonstrates that the technical solution of this invention can achieve the purpose of the invention.

[0075] The above description is merely a preferred embodiment of the present invention and is illustrative rather than restrictive. Those skilled in the art will understand that many changes, modifications, and even equivalents can be made within the spirit and scope defined by the claims of the present invention, all of which will fall within the protection scope of the present invention.

Claims

1. A long-lasting, dual-curing, interpenetrating network type, one-component epoxy resin adhesive, characterized in that, By weight, it includes: 100 parts of E-51 epoxy resin, 15-35 parts of modified imidazole curing agent, 10-40 parts of reactive diluent, and 0.2-2.0 parts of free radical polymerization initiator; The synthetic formulation of the modified imidazole curing agent includes, by weight, 0.8–1.2 parts propylene carbonate, 0.8–1.2 parts imidazole, 0.8–1.2 parts polyethylene glycol monomethyl ether, and 1 part organic acid anhydride, as well as antioxidants and catalysts by weight percentage; the preparation process of the modified imidazole curing agent includes the following steps: S1, propylene carbonate and imidazole were added to a three-necked flask equipped with a reflux condenser according to the proportion of the synthesis formula, and reacted at 140°C for 4 hours to obtain hydroxypropyl-substituted imidazole for later use. S2, polyethylene glycol monomethyl ether, organic acid anhydride and antioxidant are added to a three-necked flask equipped with a reflux condenser and a water separator according to the proportion of the synthesis formula. After reacting at 130-170℃ for 4-6 hours, organic acid anhydride-polyethylene glycol monomethyl ether monoester compound is obtained for later use. S3, the hydroxypropyl-substituted imidazole obtained in step S1, the organic acid anhydride-polyethylene glycol monomethyl ether monoester compound obtained in step S2, and the catalyst are added to a three-necked flask equipped with a reflux condenser and a water separator, and reacted at 180-205°C for 5.5-8 hours to obtain the modified imidazole curing agent.

2. The long-life, dual-curing, interpenetrating network type, single-component epoxy resin adhesive as described in claim 1, characterized in that, The reactive diluent is glycidyl methacrylate containing carbon-carbon double bonds and epoxy groups; the free radical polymerization initiator is benzoyl peroxide.

3. The long-life, dual-curing, interpenetrating network type, single-component epoxy resin adhesive as described in claim 1, characterized in that, In step S1, the organic acid anhydride is methylnadic anhydride.

4. The long-life, dual-curing, interpenetrating network type, single-component epoxy resin adhesive as described in claim 1, characterized in that, In step S2, the polyethylene glycol monomethyl ether raw material used is in a liquid state at room temperature.

5. The long-life, dual-curing, interpenetrating network type, single-component epoxy resin adhesive as described in claim 1, characterized in that, In step S2, the antioxidant is 2,6-di-tert-butyl-p-cresol, and the amount used is 0.5% of the total mass of the three substances: the hydroxypropyl-substituted imidazole product obtained in step S1, the polyethylene glycol monomethyl ether raw material used in step S2, and the organic acid anhydride.

6. The long-life, dual-curing, interpenetrating network type, one-component epoxy resin adhesive as described in claim 1, characterized in that, In step S3, the catalyst is p-toluenesulfonic acid, and the amount used is 1% of the total mass of the three substances: the hydroxypropyl-substituted imidazole product obtained in step S1, the raw material polyethylene glycol monomethyl ether, and the organic acid anhydride used in step S2.

7. A method for preparing a long-life, dual-curing, interpenetrating network type, one-component epoxy resin adhesive as described in any one of claims 1-6, characterized in that, Includes the following steps: A1. At room temperature, dissolve the free radical polymerization initiator in the reactive diluent according to the specified ratio to obtain the reactive diluent solution for later use. A2, then mix E-51 epoxy resin, modified imidazole curing agent and reactive diluent solution in proportion, then stir and degas, and after uniform mixing, obtain a dual-curing interpenetrating network type single-component epoxy resin adhesive.

8. The application of a long-life, dual-curing, interpenetrating network type single-component epoxy resin adhesive as described in claim 1 in epoxy resin curing.

9. The application of the long-life, dual-curing, interpenetrating network type single-component epoxy resin adhesive as described in claim 8 in epoxy resin curing, characterized in that, The curing process conditions are: heat preservation at 90-110℃ for 2-4 hours.

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