High-heat-resistance epoxy adhesive as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of epoxy adhesives, and particularly relates to a high-heat-resistance epoxy adhesive as well as a preparation method and application thereof. The epoxy adhesive contains modified bisphenol S epoxy resin, a multifunctional epoxy monomer, an epoxy diluent, a curing agent and optional coupling agent, filler and auxiliaries. The modified bisphenol S epoxy resin is obtained by carrying out modification reaction on unmodified bisphenol S epoxy resin and a modifier; the modifier is selected from ethylene-vinyl acetate copolymer emulsion and / or polyvinyl acetate emulsion. The key point of the invention is that the specific modified bisphenol S epoxy resin and the multifunctional epoxy monomer are used as the main components of the epoxy adhesive, and the components cooperate with each other to provide the heat resistance of the epoxy resin adhesive, so that the epoxy resin adhesive can maintain higher bonding strength in a high-temperature welding environment; and the sealing performance of the electronic component is prevented from being damaged.

Description

Technical Field

[0001] The present invention belongs to the technical field of epoxy adhesives, and particularly relates to a high heat-resistant epoxy adhesive, a preparation method thereof, and an application thereof. Background Art

[0002] Epoxy adhesives are a type of polymer adhesives with excellent bonding properties, high strength, high electrical resistance, corrosion resistance, etc., which have been widely used in the bonding, sealing, and encapsulation of electronic components, playing an important role in the fixation, sealing, moisture-proof, corrosion-proof, and anti-counterfeiting of electronic components, and becoming one of the important pillar industries in the electronics industry. However, due to the further development of electronic technology, in the process of manufacturing electronic components, sometimes it is also necessary to assemble through processes such as wave soldering or reflow soldering. During this process, it is required that the electronic adhesive has excellent high-temperature resistance and can withstand more external forces at high temperatures to ensure the integrity of the sealing of electronic components.

[0003] Reflow soldering is a process that uses an external heat source to heat and melt the solder for wetting the welding, mainly used for the welding of surface-mounted electronic components. Its principle is to heat through an external heat source to melt and flow the solder paste, thereby firmly welding the electronic components to the circuit board. For example, the reflow soldering process is usually used to achieve electrical connection between the circuit board and the frame board. In the steps of reflow soldering, it is necessary to place the circuit board, the frame board, and the electronic components connected to the circuit board as a whole in a reflow soldering furnace for reflow soldering. The temperature in the reflow soldering furnace is relatively high, usually above 220°C, and sometimes even close to 280°C. High temperature poses a risk of damaging electronic components, and as the number of reflow soldering times increases, the risk of damage to electronic components also increases accordingly. Therefore, it is required that the adhesives used for sealing and encapsulating electronic components have excellent high-temperature resistance and still maintain good bonding strength performance in a high-temperature welding environment and after experiencing a high-temperature welding environment. Conversely, if the heat resistance of the adhesive is poor, it will further exacerbate the risk of damage to electronic components. However, the current epoxy adhesives do not perform well in terms of heat resistance and bonding performance in a high-temperature welding environment and cannot well meet the above application requirements. Summary of the Invention

[0004] One of the purposes of the present invention is to provide a high heat-resistant epoxy adhesive aiming at the problem that the existing epoxy resin adhesives have poor heat resistance and cannot well protect electronic components in high-temperature processes such as reflow soldering. It has excellent high-temperature resistance and still maintains high bonding strength and toughness even in a high-temperature environment (200 - 280°C), thereby being able to protect electronic components and reduce the risk of damage to electronic components.

[0005] Specifically, the epoxy adhesive contains modified bisphenol S epoxy resin, polyfunctional epoxy monomer, epoxy diluent, curing agent, and optionally coupling agent, filler, and additive; the modified bisphenol S epoxy resin is obtained by subjecting unmodified bisphenol S epoxy resin to a modification reaction with a modifier; the modifier is selected from ethylene-vinyl acetate copolymer emulsion and / or polyvinyl acetate emulsion; the polyfunctional epoxy monomer has a structure represented by formula (1) and / or formula (2).

[0006]

[0007] In formula (1) and formula (2), R1, R2, R3, R1`, R2`, and R3` are each independently an alkylene group having 1 to 5 carbon atoms, and R4 and R4` are each independently a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or -O-R5-CHOCH2, where R5 is an alkylene group having 1 to 5 carbon atoms.

[0008] In a preferred embodiment, the content of the modified bisphenol S epoxy resin is 25 to 45 parts by weight, the content of the polyfunctional epoxy monomer is 10 to 20 parts by weight, the content of the epoxy diluent is 15 to 30 parts by weight, the content of the curing agent is 5 to 15 parts by weight, the content of the coupling agent is 0 to 2 parts by weight, the content of the filler is 0 to 20 parts by weight, and the content of the additive is 0 to 3 parts by weight.

[0009] In a preferred embodiment, before the modification reaction, the modifier is subjected to demulsification and drying treatments to obtain an intermediate product, and the obtained intermediate product is then subjected to a modification reaction with unmodified bisphenol S epoxy resin.

[0010] In a preferred embodiment, the mass ratio of the unmodified bisphenol S epoxy resin to the intermediate product is 1:(0.2 to 0.6).

[0011] In a preferred embodiment, the conditions of the modification reaction include: a temperature of 120 to 150 °C and a time of 1 to 3 h.

[0012] In a preferred embodiment, the preparation method of the unmodified bisphenol S epoxy resin includes: subjecting bisphenol S and a first halogenated epoxyalkane compound to a polymerization reaction in the presence of a first basic substance and a first organic solvent, and the obtained solid product is the unmodified bisphenol S epoxy resin.

[0013] In a preferred embodiment, the general chemical formula of the first halogenated epoxyalkane compound is X1-R6-CHOCH2, where X1 is a halogen atom and R6 is an alkylene group having 1 to 5 carbon atoms.

[0014] In a preferred embodiment, the molar ratio of bisphenol S, the first halogenated epoxyalkane compound, and the first basic substance is 1:(2 - 20):(1 - 3).

[0015] In a preferred embodiment, the conditions for the polymerization reaction include: a temperature of 20 - 80°C and a time of 1 - 12 h.

[0016] In a preferred embodiment, the method for preparing the polyfunctional epoxy monomer includes: subjecting a phenolic compound having the structure shown in formula (3) and / or formula (4) and a second halogenated epoxyalkane compound II to a substitution reaction in the presence of a second basic substance and a second organic solvent, and the resulting solid product is the polyfunctional epoxy monomer;

[0017]

[0018] In formula (3) and formula (4), R4 and R4` are each independently a hydrogen atom, an alkyl group having 1 - 5 carbon atoms, or an alkoxy group having 1 - 5 carbon atoms.

[0019] In a preferred embodiment, the phenolic compound is selected from at least one of trans - resveratrol, cis - resveratrol, piceatannol, and 3,4',5 - trihydroxy - 3'-methoxy - trans - stilbene.

[0020] In a preferred embodiment, the general chemical formula of the second halogenated epoxyalkane compound is X2 - R7 - CHOCH2, where X2 is a halogen atom and R7 is an alkylene group having 1 - 5 carbon atoms.

[0021] In a preferred embodiment, the molar ratio of the phenolic compound to the second halogenated epoxyalkane compound is 1:(4 - 30).

[0022] In a preferred embodiment, the conditions for the substitution reaction include: a temperature of 80 - 100°C and a time of 4 - 10 h.

[0023] In a preferred embodiment, the epoxy diluent is an epoxy diluent containing a benzene ring and is selected from at least one of cardanol glycidyl ether, propylene oxide o - tolyl ether, phenyl glycidyl ether, and o - tolyl glycidyl ether.

[0024] In a preferred embodiment, the curing agent is selected from epoxy resin - imidazole adducts and / or epoxy resin - aliphatic amine adducts.

[0025] A second object of the present invention is to provide a method for preparing the above - mentioned epoxy adhesive, and the preparation method includes: mixing a modified bisphenol S epoxy resin, a polyfunctional epoxy monomer, an epoxy diluent, a curing agent, and optionally a coupling agent, a filler, and an auxiliary agent under vacuum conditions to obtain the epoxy adhesive.

[0026] A third object of the present invention is to further provide an application of the above epoxy adhesive in the encapsulation of electronic components in a high-temperature welding environment.

[0027] Beneficial effects: The key of the present invention lies in using the modified bisphenol S epoxy resin obtained by modifying with a specific modifier and the polyfunctional epoxy monomer with a specific structure as the main components of the epoxy adhesive. On this basis, it is combined with an epoxy diluent, a curing agent, and optionally a coupling agent, a filler, and an auxiliary agent to form an epoxy adhesive. The modification treatment of bisphenol S epoxy resin is beneficial to improving the thermal stability and toughness of the epoxy adhesive. The addition of the polyfunctional epoxy monomer with a specific structure can increase the glass transition temperature (Tg) of the epoxy adhesive and the colloidal strength after curing of the epoxy adhesive. The mutual cooperation among the components enables the epoxy resin adhesive to have excellent heat resistance, still maintain a high bonding strength in a high-temperature welding environment (reflow soldering), ensure that the sealing performance of electronic components is not damaged, reduce the damage to electronic components in a high-temperature environment, and the preparation process of the epoxy adhesive provided by the present invention is simple and suitable for industrial production. Specific embodiments

[0028] The epoxy adhesive provided by the present invention contains a modified bisphenol S epoxy resin, a polyfunctional epoxy monomer, an epoxy diluent, a curing agent, and optionally a coupling agent, a filler, and an auxiliary agent; the modified bisphenol S epoxy resin is obtained by carrying out a modification reaction on an unmodified bisphenol S epoxy resin with a modifier; the modifier is selected from ethylene-vinyl acetate copolymer emulsion and / or polyvinyl acetate emulsion; the polyfunctional epoxy monomer has a structure shown in formula (1) and / or formula (2);

[0029]

[0030] In formula (1) and formula (2), R1, R2, R3, R1`, R2`, and R3` are each independently an alkylene group with 1 to 5 carbon atoms, and R4 and R4` are each independently a hydrogen atom, an alkyl group with 1 to 5 carbon atoms, an alkoxy group with 1 to 5 carbon atoms, or -O-R5-CHOCH2, and R5 is an alkylene group with 1 to 5 carbon atoms. Among them, specific examples of the alkylene group with 1 to 5 carbon atoms include, but are not limited to: methylene, ethylene, n-propylene, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, or neopentyl. Specific examples of the alkyl group with 1 to 5 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl, 2,2-dimethylpropyl, 1,2-dimethylpropyl, or 1-ethylpropyl. Specific examples of the alkoxy group with 1 to 5 carbon atoms include, but are not limited to: methoxy, ethoxy, propoxy, butoxy, or pentyloxy.

[0031] In the present invention, the content of the modified bisphenol S epoxy resin is preferably 25 to 45 parts by weight, such as 25, 30, 35, 40, 45 parts by weight or any value therebetween. The content of the polyfunctional epoxy monomer is preferably 10 to 20 parts by weight, such as 10, 12, 15, 18, 20 parts by weight or any value therebetween. The content of the epoxy diluent is preferably 15 to 30 parts by weight, such as 15, 18, 20, 22, 25, 28, 30 parts by weight or any value therebetween. The content of the curing agent is preferably 5 to 15 parts by weight, such as 5, 8, 10, 12, 15 parts by weight or any value therebetween. The content of the coupling agent is preferably 0 to 2 parts by weight, such as 0, 0.1, 0.2, 0.5, 0.8, 1, 1.2, 1.5, 1.5, 2 parts by weight or any value therebetween. The content of the filler is preferably 0 to 20 parts by weight, such as 0, 2, 5, 8, 10, 12, 15, 18, 20 parts by weight or any value therebetween. The content of the auxiliary agent is preferably 0 to 3 parts by weight, such as 0, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.5, 3 parts by weight or any value therebetween.

[0032] In the present invention, specific examples of the ethylene-vinyl acetate copolymer emulsion (also known as EVA latex) include, but are not limited to: at least one of CP149 purchased from Celanese Chemical, DA-102 and DA102H from Dalian Chemical Industry Co., Ltd. in Taiwan, China, VAE-806H, BJ-707, and BJ-705 from Shandong Binli New Materials Co., Ltd. Specific examples of the polyvinyl acetate emulsion (also known as PVAc emulsion, white latex) include, but are not limited to: BJ-235 of Beijing Huabiao Brand, PVAc emulsion of Chongqing Ruiya Biotechnology Co., Ltd., etc.

[0033] In the present invention, preferably, before the modification reaction, the modifier is subjected to demulsification and drying treatments to obtain an intermediate product, and the obtained intermediate product is then subjected to a modification reaction with unmodified bisphenol S epoxy resin. The method of the demulsification treatment can be selected from at least one of chemical demulsification method, physical demulsification method, biological demulsification method, combined demulsification method, and membrane demulsification method, and the specific operation methods and steps can follow the existing well-known methods. The present invention preferably adopts a physical demulsification method or a chemical demulsification method. Among them, the physical demulsification method mainly accelerates the particle collision speed through strong stirring, reduces the zeta potential of the emulsifier, thereby achieving demulsification. The specific implementation process of the physical demulsification method can be as follows: Rapidly stir through a high-speed disperser until liquid-solid separation occurs, and after filtration and drying, an intermediate product is obtained. The chemical demulsification method mainly demulsifies by adding a solvent with strong polarity such as an alcohol solvent to the emulsion. The specific implementation process of the chemical demulsification method can be as follows: Mix and stir the emulsion with a polar solvent for a certain period of time, then filter and dry, and the obtained solid is the intermediate product after demulsification. Specific examples of the polar solvent include but are not limited to at least one of methanol, ethanol, acetone, and dimethylformamide.

[0034] Further, the mass ratio of the unmodified bisphenol S epoxy resin to the intermediate product is preferably 1:(0.2 - 0.6), such as 1:0.2, 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.5, 1:0.6 or any value therebetween.

[0035] Further, the conditions of the modification reaction preferably include: the temperature is 120 - 150 °C, such as 120 °C, 130 °C, 140 °C, 150 °C or any value therebetween; the time is 1 - 3 h, such as 1 h, 1.5 h, 2 h, 2.5 h, 3 h or any value therebetween.

[0036] In the present invention, no specific restrictions are imposed on the source of the unmodified bisphenol S epoxy resin, which can be unmodified bisphenol S epoxy resin sold on the market or unmodified bisphenol S epoxy resin prepared according to existing methods or modification methods. The unmodified bisphenol S epoxy resin is preferably prepared by the following method: Bisphenol S and a first haloepoxyalkane compound are subjected to a polymerization reaction in the presence of a first basic substance and a first organic solvent, and the obtained solid product is the unmodified bisphenol S epoxy resin. The unmodified bisphenol S epoxy resin has the structure shown in formula (5):

[0037]

[0038] In formula (5), R6 is an alkylene group with 1 - 5 carbon atoms, and its specific examples are the same as those described above and will not be elaborated here one by one. n is an integer from 1 to 10, such as 1, 2, 3, 5, 7, 9, 10, etc.

[0039] Further, the epoxy equivalent of the unmodified bisphenol S epoxy resin is preferably 200 to 600 g / eq (g / mol), such as 200 g / eq, 300 g / eq, 350 g / eq, 400 g / eq, 500 g / eq, 600 g / eq, or any value therebetween.

[0040] In the preparation process of the above unmodified bisphenol S epoxy resin, the molar ratio of bisphenol S to the first halogenated epoxy alkane compound and the first basic substance is preferably 1:(2 to 20):(1 to 3). Based on 1 mol of the amount of bisphenol S, the amount of the first halogenated epoxy alkane compound is preferably 2 to 20 mol, such as 2 mol, 5 mol, 8 mol, 10 mol, 12 mol, 15 mol, 18 mol, 20 mol, or any value therebetween, more preferably 8 to 12 mol; the amount of the first basic substance is preferably 1 to 3 mol, such as 1 mol, 1.5 mol, 2 mol, 2.5 mol, 3 mol, or any value therebetween.

[0041] In the preparation process of the above unmodified bisphenol S epoxy resin, the conditions of the polymerization reaction preferably include: the temperature is 20 to 80°C, such as 20°C, 30°C, 35°C, 40°C, 50°C, 60°C, 70°C, 80°C, or any value therebetween, preferably 35 to 50°C; the time is 1 to 12 h, such as 1 h, 2 h, 5 h, 7 h, 10 h, 12 h, or any value therebetween.

[0042] In the preparation process of the above unmodified bisphenol S epoxy resin, there is no specific limitation on the mixing order of bisphenol S, the first halogenated epoxy alkane compound, the first basic substance, and the first organic solvent. It can be mixed simultaneously and then subjected to a polymerization reaction, or some raw materials can be mixed first, and then the remaining raw materials can be added and mixed for a polymerization reaction. In a specific embodiment, the preparation steps of the unmodified bisphenol S epoxy resin are as follows: bisphenol S and the first halogenated epoxy alkane compound are mixed and dissolved in the first organic solvent to obtain a mixture A, then the first basic substance and the first organic solvent are mixed and dissolved to obtain a mixture B. The temperature of the mixture A is raised to 20 to 80°C (preferably 35 to 50°C), and then the mixture B is dropped into the mixture A, and a polymerization reaction is carried out at 20 to 80°C (preferably 35 to 50°C) for 1 to 12 h. After filtration, washing, and drying, the obtained solid is the unmodified bisphenol S epoxy resin.

[0043] In the preparation process of the above unmodified bisphenol S epoxy resin, the first halogenated epoxyalkane compound can be any compound with the chemical general formula X1-R6-CHOCH2, and specifically, it can be any commercially available compound with the above chemical general formula structure. Among them, X1 is a halogen atom, such as a chlorine atom, a bromine atom or an iodine atom; R6 is an alkylene group with 1 to 5 carbon atoms, and its specific examples are as described above and will not be elaborated here one by one. Considering the easy availability of raw materials, the first halogenated epoxyalkane compound is particularly preferably epichlorohydrin and / or epichlorobutane.

[0044] In the present invention, the preparation method of the polyfunctional epoxy monomer preferably includes: subjecting a phenolic compound having the structure shown in formula (3) and / or formula (4) to a substitution reaction with a second halogenated epoxyalkane compound II in the presence of a second basic substance and a second organic solvent, and the resulting solid product is the polyfunctional epoxy monomer;

[0045]

[0046] In formula (3) and formula (4), R4 and R4` are each independently a hydrogen atom, an alkyl group with 1 to 5 carbon atoms or an alkoxy group with 1 to 5 carbon atoms. Among them, the specific examples of the alkylene group with 1 to 5 carbon atoms, the alkyl group with 1 to 5 carbon atoms, and the alkoxy group with 1 to 5 carbon atoms are as described above and will not be elaborated here one by one.

[0047] In the present invention, the epoxy functionality of the polyfunctional epoxy monomer is 3 to 4. The epoxy equivalent of the polyfunctional epoxy monomer is preferably 110 to 150 g / eq, such as 110 g / eq, 120 g / eq, 130 g / eq, 140 g / eq, 150 g / eq or any value between them.

[0048] In the present invention, the epoxy equivalent can be measured by the commonly used test methods in the prior art, and preferably the following method is adopted: dissolve the sample to be measured in one of organic solvents such as chloroform, acetone, benzene, chlorobenzene, etc., add tetraethylammonium bromide and crystal violet indicator, and then titrate with a perchloric acid - glacial acetic acid standard solution until the solution turns green and stop. Calculate the epoxy equivalent according to the following formula: EEW = 10000W / (N*S), where EEW is the epoxy equivalent (g / mol = g / eq), W is the mass of the sample to be measured (g), N is the concentration of the perchloric acid - glacial acetic acid standard solution (mol / L), and S is the volume of the perchloric acid - glacial acetic acid standard solution consumed in the titration (mL).

[0049] In the preparation process of the above-mentioned polyfunctional epoxy monomer, the phenolic compound may be a kind of compound having the structure shown in formula (2) or formula (3), and specifically may be at least one of trans-resveratrol, cis-resveratrol, piceatannol, and 3,4',5-trihydroxy-3'-methoxy-trans-stilbene. The phenolic compound is preferably trans-resveratrol and / or cis-resveratrol. Compared with traditional epoxy monomers, the epoxy monomer prepared from such bio-based phenolic compounds has the characteristics of no cytotoxicity and genotoxicity, making the epoxy adhesive more in line with the current development theme and trend of green environmental protection.

[0050] In the preparation process of the above-mentioned polyfunctional epoxy monomer, the second halogenated epoxy alkane compound may be a kind of compound having the chemical general formula X2-R7-CHOCH2, and specifically may be any commercially available compound having the above chemical general formula structure. Among them, X2 is a halogen atom, such as a chlorine atom, a bromine atom or an iodine atom; R7 is an alkylene group with 1 to 5 carbon atoms, and its specific examples are as described above and will not be elaborated here. Considering the easy availability of raw materials, the second halogenated epoxy alkane compound is particularly preferably epichlorohydrin and / or epichlorobutane.

[0051] In the preparation process of the above-mentioned polyfunctional epoxy monomer, the molar ratio of the phenolic compound to the second halogenated epoxy alkane compound is preferably 1:(4 - 30), such as 1:4, 1:6, 1:10, 1:15, 1:20, 1:25, 1:30 or any value between them.

[0052] In the preparation process of the above-mentioned polyfunctional epoxy monomer, the conditions of the substitution reaction preferably include: the temperature is 80 - 100 °C, such as 80 °C, 85 °C, 90 °C, 95 °C, 100 °C or any value between them; the time is 4 - 10 h, such as 4 h, 5 h, 6 h, 8 h, 10 h or any value between them.

[0053] In the preparation process of the above-mentioned polyfunctional epoxy monomer, the substitution reaction is preferably carried out in the following manner: Mix the phenolic compound having the structure shown in formula (3) and / or formula (4) with the second halogenated epoxy alkane compound II and simultaneously heat up to 80 - 100 °C to obtain a mixed solution C. Mix and dissolve the second basic substance and the second organic solvent to obtain a mixed solution D. Then, add the mixed solution D dropwise to the above-mentioned mixed solution C within 2 - 4 h, and continue to react at 80 - 100 °C for 4 - 6 h. After filtration, washing, and drying, the obtained solid is the polyfunctional epoxy monomer.

[0054] In the present invention, the types of the first basic substance and the second basic substance may be the same or different, as long as they can provide a basic environment for the reaction system, and each is independently preferably selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate.

[0055] In the present invention, the types of the first organic solvent and the second organic solvent may be the same or different, and each is independently preferably selected from at least one of ethanol, methanol, and N,N-dimethylformamide.

[0056] In the present invention, specific examples of the epoxy diluent include, but are not limited to, at least one of ethylene glycol diglycidyl ether, butanediol diglycidyl ether, hexanediol diglycidyl ether, polypropylene glycol diglycidyl ether, trimethylolpropane glycidyl ether, cardanol glycidyl ether, propylene oxide o-tolyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether. The epoxy diluent is preferably an epoxy diluent containing a benzene ring, such as at least one of cardanol glycidyl ether, phenyl glycidyl ether, and o-tolyl glycidyl ether. In this case, it is more beneficial to increase the glass transition temperature (Tg) of the cured epoxy adhesive and improve the heat resistance of the epoxy adhesive.

[0057] In the present invention, the curing agent is preferably selected from epoxy resin-imidazole adducts and / or epoxy resin-fatty amine adducts, and specifically may be selected from at least one of PN-23, PN-23J, PN-40, PN-40J, MY-24 of Ajinomoto of Japan, EH-3293, EH-3293S, H3615 of Asahi Denka of Japan, HX-3721, HX-3741 of Asahi Kasei of Japan, and FXE-1000 of Fuji Kasei of Japan.

[0058] In the present invention, specific examples of the coupling agent include, but are not limited to, at least one of methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, γ-mercaptopropyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)-propyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, and bis(γ-triethoxysilylpropyl)-tetrasulfide.

[0059] In the present invention, the filler is selected from at least one of talcum powder, silica powder, calcium carbonate, bentonite, and inorganic pigments (such as carbon black and titanium dioxide).

[0060] In the present invention, specific examples of the auxiliary agent include, but are not limited to, at least one of a thixotropic agent, a stabilizer, a polymerization inhibitor, an antioxidant, a flame retardant, an adhesion promoter, a dye, a pigment, an antifoaming agent, a leveling agent, a homogenizing agent, and an ion scavenger. The thixotropic agent is particularly preferably a thixotropic agent, and the thixotropic agent is preferably silica, which may specifically be selected from at least one of H8, H20, H30 of Waker Corporation, TS-530, TS720 of Cabot Corporation, and R972, R974, R976, R202, R8200 of Degussa Corporation.

[0061] In the present invention, the preparation method of the epoxy adhesive includes: mixing a modified bisphenol S epoxy resin, a polyfunctional epoxy monomer, an epoxy diluent, a curing agent, and optionally a coupling agent, a filler, and an auxiliary agent under vacuum conditions, and then the epoxy adhesive is obtained.

[0062] In a specific embodiment, the preparation method of the epoxy adhesive includes: adding a modified bisphenol S epoxy resin, a bio-based polyfunctional epoxy monomer, an epoxy diluent, and optionally a coupling agent into a double planetary hybrid reactor and stirring evenly under vacuum conditions through a first mixing process, then adding a curing agent and stirring evenly under vacuum conditions through a second mixing process, and optionally, adding a filler and an auxiliary agent and continuing to stir evenly under vacuum conditions through a third mixing process, and then the epoxy adhesive is obtained.

[0063] In the present invention, further, the vacuum condition is preferably a vacuum degree ≤ 0.098 MPa.

[0064] In the present invention, further, the temperature of the first mixing process is preferably 70 - 80 °C, such as 70 °C, 72 °C, 75 °C, 78 °C, 80 °C or any value between them. At this time, it is more conducive to accelerating the mixing speed. The time of the first mixing process is not specifically limited, as long as the modified bisphenol S epoxy resin, the bio-based polyfunctional epoxy monomer, the epoxy diluent, and optionally the coupling agent can be evenly mixed.

[0065] In the present invention, further, the temperatures of the second mixing process and the third mixing process are each independently preferably 20 - 30 °C, such as 20 °C, 22 °C, 25 °C, 28 °C, 30 °C or any value between them. The times of the second mixing process and the third mixing process are not specifically limited, as long as the added raw materials can be evenly mixed.

[0066] In addition, the terms "first", "second", and "third" are only for the purpose of convenient description and cannot be construed as limiting the type or quantity of the defined technical features.

[0067] The present invention will be described in detail below with specific embodiments. The examples are intended to explain the present invention and should not be construed as limiting the present invention. For those without specific technical or conditions noted in the examples, the techniques or conditions described in the literature in this field or according to the product specifications are followed. Those reagents or instruments without the manufacturer noted are all conventional products that can be obtained through commercial purchase.

[0068] In the following examples and comparative examples, the parts of each raw material refer to parts by weight.

[0069] In the following examples and comparative examples, the epoxy equivalent involved is obtained by the following steps: Dissolve 1 g of the sample to be measured in 10 mL of chloroform, add 10 mL of tetraethylammonium bromide and 2 drops of crystal violet indicator, and then titrate with a 0.1 mol / L perchloric acid - glacial acetic acid standard solution until the solution turns green and stop. Calculate the epoxy equivalent according to the following formula: EEW = 10000W / (N*S), where EEW is the epoxy equivalent (g / mol), W is the mass of the sample to be measured (g), N is the concentration of the perchloric acid - glacial acetic acid standard solution (mol / L), and S is the volume of the perchloric acid - glacial acetic acid standard solution consumed in the titration (mL).

[0070] Preparation Example 1 Preparation of Modified Bisphenol S Epoxy Resin

[0071] Dissolve 100 g of bisphenol S in 200 g of absolute ethanol, add 370 g of epichlorohydrin, mix and stir evenly in a three - necked flask and heat up to 50 °C. Dissolve 34 g of sodium hydroxide in 330 g of absolute ethanol as the dropping solution and drop it all into the three - necked flask within 2.5 h. After dropping, react for another 5 h; after the reaction is completed, filter under reduced pressure to obtain a solid, add deionized water to wash the product repeatedly until the pH value of the washing solution is 6 - 8, and obtain bisphenol S epoxy resin 1 with an epoxy equivalent of 350 g / eq.

[0072] Demulsify the CP149 latex purchased from Celanese Chemical and dry it for later use; add 20 g of the dried and demulsified CP149 solid product to 100 g of bisphenol S epoxy resin 1, and then carry out a mixing reaction at 120 °C for 2 h. The cooled solid is crushed and ball - milled, and the obtained powder is modified bisphenol S epoxy resin 1.

[0073] Preparation Example 2 Preparation of Modified Bisphenol S Epoxy Resin

[0074] Dissolve 80 g of bisphenol S in 160 g of absolute ethanol, add 590 g of epichlorohydrin, mix and stir evenly in a three-necked flask and heat up to 35 °C. Dissolve 27 g of sodium hydroxide in 260 g of absolute ethanol, and add it dropwise into the three-necked flask within 2 h as a dropping solution. After the dropping is completed, react for another 7 h. After the reaction is completed, filter under reduced pressure to obtain a solid, add deionized water to wash the product repeatedly until the pH value of the washing solution is 6 - 8, and obtain bisphenol S epoxy resin 2 with an epoxy equivalent of 380 g / eq.

[0075] Demulsify the DA-102H latex purchased from Dalian Chemical Industry in Taiwan, China, and dry it for standby; add 40 g of the demulsified and dried DA-102 solid product to 100 g of bisphenol S epoxy resin 2, and then react and mix at 150 °C for 3 h. The cooled solid is crushed and ball-milled, and the obtained powder is the modified bisphenol S epoxy resin 2.

[0076] Preparation of Modified Bisphenol S Epoxy Resin in Preparation Example 3

[0077] Dissolve 120 g of bisphenol S in 240 g of absolute ethanol, add 255 g of epichlorobutane, mix and stir evenly in a three-necked flask and heat up to 35 °C. Dissolve 40 g of sodium hydroxide in 350 g of absolute ethanol, and add it dropwise into the three-necked flask within 3 h as a dropping solution. After the dropping is completed, react for another 10 h. After the reaction is completed, filter under reduced pressure to obtain a solid, add deionized water to wash the product repeatedly until the pH value of the washing solution is 6 - 8, and obtain bisphenol S epoxy resin 3 with an epoxy equivalent of 410 g / eq.

[0078] Demulsify the polyvinyl acetate emulsion with the brand name BJ-235 purchased from Huabiao Brand Company in Beijing and dry it for standby; add 60 g of the demulsified and dried DA-102 solid product to 100 g of bisphenol S epoxy resin 3, and then mix and react at 130 °C for 2 h. The cooled solid is crushed and ball-milled, and the obtained powder is the modified bisphenol S epoxy resin 3.

[0079] Preparation of Modified Bisphenol S Epoxy Resin in Preparation Example 4

[0080] Demulsify the DA-102 latex purchased from Dalian Chemical Industry in Taiwan, China, and dry it for standby; add 60 g of the demulsified and dried DA-102 solid product to 100 g of bisphenol S epoxy resin 300SS from Compton Company in the United States, and then react and mix at 130 °C for 2 h. The cooled solid is crushed and ball-milled, and the obtained powder is the modified bisphenol S epoxy resin 4.

[0081] Preparation of Modified Bisphenol S Epoxy Resin in Preparation Example 5

[0082] The modified bisphenol S epoxy resin 5 was prepared according to the method of Preparation Example 1, except that the amount of the CP149 solid product after demulsification and drying was 10 g, and the other conditions were the same as those in Preparation Example 1. Thus, the modified bisphenol S epoxy resin 5 was obtained.

[0083] Preparation Example 6 Preparation of Modified Bisphenol S Epoxy Resin

[0084] The modified bisphenol S epoxy resin 3 was prepared according to the method of Preparation Example 1, except that the amount of the CP149 solid product after demulsification and drying was 80 g, and the other conditions were the same as those in Preparation Example 1. Thus, the modified bisphenol S epoxy resin 3 was obtained.

[0085] Preparation Example 7 Preparation of Polyfunctional Epoxy Monomer

[0086] A three-necked round-bottom flask was equipped with a reflux condenser and a dropping funnel. Under a N2 atmosphere, 43 g of cis-resveratrol (0.188 mol) and 400 g of epichlorohydrin (4.323 mol) were added to the three-necked flask, and the reaction temperature was raised to 90 °C to obtain a mixed solution. Subsequently, 28 g of sodium hydroxide was dissolved in 240 g of ethanol, and this sodium hydroxide solution was added dropwise to the mixed solution of resveratrol and epichlorohydrin through the dropping funnel within 2 h. The mixed solution changed from the initial off-white slurry to light orange, and the reaction was continued with stirring at 90 °C for 4.5 h. The filtrate was filtered, concentrated under reduced pressure, and washed with distilled water and brine to obtain an off-white waxy solid, which was the bio-based polyfunctional epoxy monomer 1. The epoxy equivalent was measured to be 132 g / eq.

[0087] It was proven by testing that the bio-based polyfunctional epoxy monomer 1 had the structure shown in formula (2), where R1ˋ, R2ˋ, and R3ˋ were methylene groups, and R4ˋ was a hydrogen atom.

[0088] Preparation Example 8 Preparation of Polyfunctional Epoxy Monomer

[0089] A three-necked round-bottom flask was equipped with a reflux condenser and a dropping funnel. Under a N2 atmosphere, 60 g of trans-resveratrol (0.263 mol) and 690 g of epichlorobutane (6.476 mol) were added to the three-necked flask, and the reaction temperature was raised to 80 °C to obtain a mixed solution. Subsequently, 40 g of sodium hydroxide was dissolved in 350 g of ethanol, and this sodium hydroxide solution was added dropwise to the mixed solution of trans-resveratrol and epichlorohydrin through the dropping funnel within 3 h. The mixed solution changed from the initial off-white slurry to light orange, and the reaction was continued with stirring at 90 °C for 5 h. The filtrate was filtered, concentrated under reduced pressure, and washed with distilled water and brine to obtain an off-white waxy solid, which was the bio-based polyfunctional epoxy monomer 2. The epoxy equivalent was measured to be 146 g / eq.

[0090] It has been proven by testing that the bio-based polyfunctional epoxy monomer 2 has the structure shown in formula (1), where R1, R2, and R3 are ethylene groups, and R4 is a hydrogen atom.

[0091] Preparation Example 9 Preparation of Polyfunctional Epoxy Monomer

[0092] A three-necked round-bottom flask was equipped with a reflux condenser and a dropping funnel. Under a nitrogen atmosphere, 70 g of piceatannol (3,4,3',5'-tetrahydroxy-trans-stilbene) (0.287 mol) and 268 g of epichlorohydrin (2.9 mol) were added to the three-necked flask. The reaction temperature was raised to 100 °C to obtain a mixed solution. Subsequently, 40 g of sodium hydroxide was dissolved in 350 g of ethanol, and this sodium hydroxide solution was added dropwise to the mixed solution of piceatannol and epichlorohydrin within 3 h through the dropping funnel. The mixed solution changed from the initial off-white slurry to light orange. The reaction was continued with stirring at 90 °C for 6 h, filtered, the filtrate was concentrated under reduced pressure, and washed with distilled water and brine to obtain an off-white waxy solid, which was the bio-based polyfunctional epoxy monomer 3. The epoxy equivalent was measured to be 117 g / eq.

[0093] It has been proven by testing that the bio-based polyfunctional epoxy monomer 3 has the structure shown in formula (1), where R1, R2, and R3 are methylene groups, and R4 is -O-CH2CH2-CHOCH2.

[0094] Comparative Preparation Example 1 Preparation of Reference Epoxy Monomer

[0095] The reference epoxy monomer was prepared according to the method of Preparation Example 6, except that 1,2,4-trihydroxybenzene in the same molar amount was used instead of trans-resveratrol, and the other conditions were the same as those in Preparation Example 6. Thus, the reference epoxy monomer was prepared.

[0096] Example 1 Preparation of Epoxy Adhesive

[0097] S1. 45 parts of modified bisphenol S epoxy resin 1, 10 parts of bio-based polyfunctional epoxy monomer 1, 23 parts of cardanol glycidyl ether, and 1 part of γ-mercaptopropyltriethoxysilane were successively added to a double-planet hybrid power reactor, and the temperature was controlled at about 75 °C, and stirred evenly under vacuum;

[0098] S2. After the temperature was lowered to 25 °C, 7 parts of the PN-23 curing agent of Ajinomoto were added to the reactor in step S1, and stirred evenly under vacuum;

[0099] S3. 11 parts of light calcium carbonate and 3 parts of Cabot's TS720 fumed silica were added to the reactor in step S2, and after stirring evenly under vacuum, the product was discharged to obtain an epoxy adhesive, denoted as A1.

[0100] Example 2 Preparation of Epoxy Adhesive

[0101] S1. Add 25 parts of modified bisphenol S epoxy resin 2, 20 parts of bio-based polyfunctional epoxy monomer 2, 30 parts of phenyl glycidyl ether, and 0.5 part of γ-methacryloyloxypropyltrimethoxysilane into a double-planet hybrid reactor in sequence, control the temperature at about 75°C, and stir evenly under vacuum;

[0102] S2. After reducing the temperature to 25°C, add 10 parts of EH-3293S curing agent from Asahi Kasei Corporation of Japan into the reactor in step S1, and stir evenly under vacuum;

[0103] S3. Add 13 parts of light calcium carbonate, 0.5 part of titanium dioxide, and 1 part of R972 fumed silica from Degussa Corporation into the reactor in step S2, stir evenly under vacuum, and then discharge to obtain an epoxy adhesive, denoted as A2.

[0104] Preparation of epoxy adhesive in Example 3

[0105] S1. Add 35 parts of modified bisphenol S epoxy resin 3, 14 parts of bio-based polyfunctional epoxy monomer 3, 15 parts of o-tolyl glycidyl ether, and 1.5 parts of γ-mercaptopropyltriethoxysilane into a double-planet hybrid reactor in sequence, control the temperature at about 75°C, and stir evenly under vacuum;

[0106] S2. After reducing the temperature to 25°C, add 15 parts of HX-3741 curing agent purchased from Asahi Kasei of Japan into the reactor in step S1, and stir evenly under vacuum;

[0107] S3. Add 17.5 parts of bentonite and 2 parts of H8 fumed silica from Waker Corporation into the reactor in step S2, stir evenly under vacuum, and then discharge to obtain an epoxy adhesive, denoted as A3.

[0108] Preparation of epoxy adhesive in Example 4

[0109] Prepare the epoxy adhesive according to the method of Example 1, except that the same amount of modified bisphenol S epoxy resin 4 is used instead of modified bisphenol S epoxy resin 1, and the other conditions are the same as those in Example 1. Thus, an epoxy adhesive is prepared and denoted as A4.

[0110] Preparation of epoxy adhesive in Example 5

[0111] Prepare the epoxy adhesive according to the method of Example 1, except that the same amount of ethylene glycol diglycidyl ether is used instead of cardanol glycidyl ether, and the other conditions are the same as those in Example 1. Thus, an epoxy adhesive is prepared and denoted as A5.

[0112] Preparation of epoxy adhesive in Example 6

[0113] The epoxy adhesive was prepared according to the method of Example 1, except that the same amount of modified bisphenol S epoxy resin 5 was used instead of modified bisphenol S epoxy resin 1, and the other conditions were the same as those in Example 1. Thus, the epoxy adhesive obtained was denoted as A5.

[0114] Preparation of Epoxy Adhesive in Example 7

[0115] The epoxy adhesive was prepared according to the method of Example 1, except that the same amount of modified bisphenol S epoxy resin 6 was used instead of modified bisphenol S epoxy resin 1, and the other conditions were the same as those in Example 1. Thus, the epoxy adhesive obtained was denoted as A5.

[0116] Preparation of Reference Epoxy Adhesive in Comparative Example 1

[0117] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same amount of bisphenol S epoxy resin 300SS from Compton Corporation, USA was used instead of modified bisphenol S epoxy resin 1, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive obtained was denoted as DA1.

[0118] Preparation of Reference Epoxy Adhesive in Comparative Example 2

[0119] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same amount of unmodified bisphenol S epoxy resin 1 was used instead of modified bisphenol S epoxy resin 1, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive obtained was denoted as DA2.

[0120] Preparation of Reference Epoxy Adhesive in Comparative Example 3

[0121] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same amount of trifunctional epoxy monomer ERISYS GE-31 (trimethylol ethane triglycidyl ether) from Huntsman, USA was used to replace the bio-based polyfunctional epoxy monomer 1, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive obtained was denoted as DA3.

[0122] Preparation of Reference Epoxy Adhesive in Comparative Example 4

[0123] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same amount of the reference epoxy monomer prepared in Comparative Preparation Example 1 was used to replace the bio-based polyfunctional epoxy monomer 1, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive obtained was denoted as DA4.

[0124] Test Example

[0125] The epoxy adhesives prepared in the above examples and comparative examples were tested for shear strength, high temperature resistance, glass transition temperature (Tg), toughness, and reflow soldering according to the following methods. The results are shown in Table 1.

[0126] (1) Shear strength test: The test was conducted according to the method in standard GB / T 7124-2008. The epoxy adhesives obtained in the above embodiments and comparative examples were used to prepare stainless steel-to-stainless steel shear sheets with an overlap area of ​​25.4 mm*12.7 mm. The thickness of the adhesive layer was 0.2 mm. After curing at 120°C for 60 min, the shear strength was tested at 25°C, 130°C, and 200°C, respectively, and the tensile speed was 5 mm / min.

[0127] (2) High temperature resistance test: The epoxy adhesives obtained in the above embodiments and comparative examples were used to prepare stainless steel-to-stainless steel shear sheets with an overlap area of ​​25.4 mm*12.7 mm. The thickness of the adhesive layer was 0.2 mm. After curing at 120°C for 60 min, the shear strength was tested after the sheets were allowed to stand at room temperature until they reached room temperature. The result was denoted as S 25℃ The epoxy adhesives obtained in the above embodiments and comparative examples were used to prepare stainless steel-to-stainless steel shear sheets with an overlap area of ​​25.4 mm*12.7 mm, and the thickness of the adhesive layer was 0.2 mm. After curing at 120°C for 60 min, the prepared shear specimens were placed in an ESPEC oven with the temperature set to 220°C. The specimens were taken out after being placed for 5 days and 10 days respectively, and their shear strengths were tested after being placed at room temperature, and were recorded as S` 25℃ ,S`` 25℃ , and calculate the residual shear strength D after 5 days of placement 5day =(S 25℃ -S` 25℃ ) / S 25℃ And the residual shear strength D after 10 days of placement 10day =(S 25℃ -S`` 25℃ ) / S 25℃ The higher the residual shear strength ratio is, the better the heat resistance of the adhesive after curing is.

[0128] (3) Glass transition temperature (Tg) test: The sample was subjected to dynamic thermomechanical analysis (TMA) test by TADiscovery TMA450 analyzer under the condition of N2 inlet volume of 100 mL / min. The sample was contacted with a bending probe under a force of 0.20 N, and then the sample was heated from 0 ° C to 250 ° C at a rate of 5 ° C / min. During the test cycle, the force was adjusted by ± 0.08 N at a frequency of 0.10 Hz. The glass transition temperature (Tg) of the epoxy adhesive was measured, and the data was the average of three independent runs.

[0129] (4) Toughness test: Referring to the standard of GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", type 4 dumbbell specimens with a thickness of 0.4 mm were prepared. The dumbbell specimens were tested with an Instron universal tensile testing machine to obtain the elongation at break data. The larger the value, the better the toughness of the material. The dumbbell specimens were placed in an ESPEC oven with the temperature set at 220 °C. After 5 days and 10 days, the specimens were taken out, allowed to return to room temperature, and then tested to obtain the elongation at break data after aging for 5 days and 10 days.

[0130] (5) Reflow soldering test: Glue was applied to the relay components for dotting and sealing. After curing under the conditions of 120 °C for 60 min, a water leak tightness test was carried out before reflow soldering (the relay was placed in water and heated to 100 °C and boiled for 1 - 2 min. If there was a problem with the tightness, bubbles would overflow from the relay). Reflow soldering was carried out using a Hoba lead-free hot air reflow soldering machine CR-1002. The reflow soldering process was set for 5 min, the preheating temperature was 150 °C, the heating rate was 3 °C / s, the soldering start temperature was 220 °C, the maximum temperature was 260 °C, the soldering time was 60 s, the time above 250 °C was about 5 - 10 s, and the reflow soldering process ended after cooling to below 50 °C. A water leak tightness test was carried out on the relay after reflow soldering (the relay was placed in water and heated to 100 °C and boiled for 1 - 2 min. If there was a problem with the tightness, bubbles would overflow from the relay), and the failure ratio was calculated. For the relays with intact tightness and no leakage, reflow soldering was carried out again to check the tightness of the relay, and the failure ratio was calculated. The higher the failure ratio, the worse the heat resistance and heat compression resistance of the glue.

[0131] Table 1

[0132]

[0133] As can be seen from the results in Table 1, compared with Comparative Examples 1 to 4, the epoxy adhesives provided in Examples 1 to 7 still have excellent shear strength at high temperatures of 130 °C and 200 °C, and the remaining strength and elongation at break after high-temperature aging at 200 °C for 5 days and 10 days are higher, and no leakage occurs after 2 reflow soldering processes. From the results of Example 1, Comparative Example 1 and Comparative Example 2, it can be seen that using conventional bisphenol S epoxy resins on the market or self-made unmodified bisphenol S epoxy resins to replace the modified bisphenol S epoxy resin results in a decrease in the shear strength of the epoxy adhesive at high temperatures of 130 °C and 200 °C, and a significant decrease in the remaining strength and elongation at break after high-temperature aging at 200 °C for 5 days and 10 days, and a high leakage rate of electronic components after 1 and 2 reflow soldering processes. From the results of Example 1 and Comparative Example 3, it can be seen that when using a conventional trifunctional epoxy monomer on the market to replace the bio-based polyfunctional epoxy monomer 1, the shear strength of the epoxy adhesive at high temperatures of 130 °C and 200 °C is significantly reduced, and the remaining strength and elongation at break after high-temperature aging at 200 °C for 5 days and 10 days are reduced, and the leakage rate of electronic components after 1 and 2 reflow soldering processes is high. From the results of Example 1 and Comparative Example 4, it can be seen that using a monobenzene ring epoxy monomer different from the bio-based polyfunctional epoxy monomer 1 to prepare an epoxy adhesive, its shear strength at high temperatures of 130 °C and 200 °C and the elongation at break after high-temperature aging at 200 °C for 5 days and 10 days are slightly reduced, but the Tg is lower, the remaining strength after high-temperature aging at 200 °C for 5 days and 10 days is reduced, and a certain proportion of leakage occurs in the electronic components after 2 reflow soldering processes.

[0134] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. An epoxy adhesive, characterized in that: The epoxy adhesive contains modified bisphenol S epoxy resin, multifunctional epoxy monomer, epoxy diluent, curing agent and optional coupling agent, filler and auxiliary agent; the modified bisphenol S epoxy resin is obtained by modifying unmodified bisphenol S epoxy resin with a modifier; the modifier is selected from ethylene-vinyl acetate copolymer emulsion and / or polyvinyl acetate emulsion; the multifunctional epoxy monomer has a structure as shown in formula (1) and / or formula (2); In formula (1) and formula (2), R1, R2, R3, R1`, R2` and R3` are each independently a C1-C5 alkylene group, R4 and R4` are each independently a hydrogen atom, a C1-C5 alkyl group, a C1-C5 alkoxy group or -O-R5-CHOCH2, and R5 is a C1-C5 alkylene group.

2. The epoxy adhesive according to claim 1, characterized in that: The content of the modified bisphenol S epoxy resin is 25 to 45 parts by weight, the content of the multifunctional epoxy monomer is 10 to 20 parts by weight, the content of the epoxy diluent is 15 to 30 parts by weight, the content of the curing agent is 5 to 15 parts by weight, the content of the coupling agent is 0 to 2 parts by weight, the content of the filler is 0 to 20 parts by weight, and the content of the auxiliary agent is 0 to 3 parts by weight.

3. The epoxy adhesive according to claim 1, characterized in that: Before the modification reaction, the modifier is subjected to demulsification and drying treatment to obtain an intermediate product, and the intermediate product is then subjected to a modification reaction with unmodified bisphenol S epoxy resin; Preferably, the mass ratio of the unmodified bisphenol S epoxy resin to the intermediate product is 1:(0.2-0.6); Preferably, the modification reaction conditions include: temperature of 120-150° C. and time of 1-3 h.

4. The epoxy adhesive according to claim 1, characterized in that: The preparation method of the unmodified bisphenol S epoxy resin comprises: subjecting bisphenol S to a polymerization reaction with a first halogenated epoxy alkylene compound in the presence of a first alkaline substance and a first organic solvent, and the obtained solid product is the unmodified bisphenol S epoxy resin; Preferably, the general chemical formula of the first halogenated epoxyalkane compound is X1-R6-CHOCH2, wherein X1 is a halogen atom and R6 is a C1-C5 alkylene group.

5. The epoxy adhesive according to claim 4, characterized in that: The molar ratio of the bisphenol S to the first halogenated alkylene oxide compound and the first alkaline substance is 1:(2-20):(1-3); Preferably, the polymerization reaction conditions include: temperature of 20 to 80° C. and time of 1 to 12 hours.

6. The epoxy adhesive according to claim 1, characterized in that: The preparation method of the multifunctional epoxy monomer comprises: subjecting a phenolic compound having a structure as shown in formula (3) and / or formula (4) to a substitution reaction with a second halogenated epoxyalkane compound II in the presence of a second alkaline substance and a second organic solvent, and obtaining a solid product which is the multifunctional epoxy monomer; In formula (3) and formula (4), R4 and R4' are each independently a hydrogen atom, a C1-C5 alkyl group or a C1-C5 alkoxy group; Preferably, the phenolic compound is selected from at least one of trans-resveratrol, cis-resveratrol, piceatannol, and 3,4',5-trihydroxy-3'-methoxy-trans-stilbene; Preferably, the general chemical formula of the second halogenated epoxyalkane compound is X2-R7-CHOCH2, wherein X2 is a halogen atom and R7 is a C1-C5 alkylene group.

7. The epoxy adhesive according to claim 6, characterized in that: The molar ratio of the phenolic compound to the second halogenated epoxyalkylene compound is 1:(4-30); Preferably, the conditions of the substitution reaction include: temperature of 80-100° C. and time of 4-10 h.

8. The epoxy adhesive according to claim 1, characterized in that: The epoxy diluent is an epoxy diluent containing a benzene ring, and is selected from at least one of cardanol glycidyl ether, phenyl glycidyl ether, and o-cresyl glycidyl ether; Preferably, the curing agent is selected from epoxy resin-imidazole adducts and / or epoxy resin-fatty amine adducts.

9. The method for preparing the epoxy adhesive according to any one of claims 1 to 8, characterized in that: The preparation method comprises: mixing modified bisphenol S epoxy resin, multifunctional epoxy monomer, epoxy diluent, curing agent and optional coupling agent, filler and auxiliary agent under vacuum conditions to obtain epoxy adhesive.

10. Use of the epoxy adhesive according to any one of claims 1 to 8 in electronic component packaging under high temperature welding environment.

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