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 an epoxy adhesive as well as a preparation method and application thereof. The epoxy adhesive contains liquid epoxy resin, bisphenol S epoxy resin, a liquid aromatic amine curing agent and optional coupling agent, filler and auxiliaries. The bisphenol S epoxy resin has a structure as shown in a formula (1). The key points of the invention are as follows: the liquid epoxy resin and the bisphenol S epoxy resin with a specific structure are taken as main bodies, and on the basis, the liquid epoxy resin and the bisphenol S epoxy resin are matched with the specific liquid aromatic amine curing agent and the optional coupling agent, filler and assistant to form the epoxy adhesive, so that the epoxy resin adhesive has excellent heat resistance and improved compression resistance; the epoxy adhesive provided by the invention can maintain high bonding strength in a high-temperature welding environment, ensures that the sealing performance of an electronic component is not damaged, reduces the damage of the high-temperature environment to the electronic component, and is simple in preparation process and suitable for industrial production. # imgabs0 #

Description

Technical Field

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

[0002] With the continuous development of electronic technology, epoxy adhesives have become one of the important pillars of the electronics industry. Epoxy adhesives are widely used in the bonding, potting and encapsulation of electronic components, and play an important role in the fixation, sealing, moisture-proof, anti-corrosion and anti-counterfeiting of electronic components. However, with the further development of electronic technology, it is often necessary to assemble electronic components to meet application requirements. In the actual production process, the reflow soldering process is usually used to achieve electrical connection between the circuit board and the frame board. The principle is to heat through an external heat source to melt and flow the solder paste, so as to firmly solder the electronic components on the circuit board. In the reflow soldering step, 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 the temperature will be close to 280 °C. High temperature will pose a risk of damaging electronic components, and with the increase in the number of reflow soldering times, the risk of damage to electronic components will also increase accordingly. Therefore, it is required that the adhesives used for sealing and potting electronic components have excellent high-temperature resistance and still maintain good bonding strength performance in high-temperature welding environments and after experiencing high-temperature welding environments. On the contrary, if the heat resistance of the adhesive is poor, it will further increase 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 high-temperature welding environments to meet the above application requirements. Summary of the Invention

[0003] 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 bonding strength in high-temperature processes such as reflow soldering and cannot well protect electronic components. It has excellent high-temperature resistance and still maintains high bonding strength and toughness even in high-temperature environments (200-280 °C), so as to protect electronic components and reduce the risk of damage to electronic components.

[0004] Specifically, the epoxy adhesive contains liquid epoxy resin, bisphenol S epoxy resin, liquid curing agent and optionally coupling agent, filler, and additive; the liquid curing agent is a liquid aromatic amine curing agent; the bisphenol S epoxy resin has the structure shown in formula (1);

[0005]

[0006] In formula (1), R1 and R2 are each independently an alkylene group having 1 to 5 carbon atoms, R3 to R6 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is an integer of 1 to 5.

[0007] In a preferred embodiment, the content of the liquid epoxy resin is 20 to 30 parts by weight, the content of the bisphenol S epoxy resin is 30 to 50 parts by weight, the content of the liquid curing agent is 10 to 25 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 5 parts by weight.

[0008] In a preferred embodiment, the liquid epoxy resin is bisphenol A epoxy resin and / or bisphenol F epoxy resin.

[0009] In a preferred embodiment, the viscosity of the liquid epoxy resin at 25 °C is 1000 to 5500 mPa·s.

[0010] In a preferred embodiment, the preparation method of the bisphenol S epoxy resin includes:

[0011] S1. React bisphenol S with a carbonate compound having the structure shown in formula (2) in the presence of a catalyst to obtain an intermediate product;

[0012] S2. React the obtained intermediate product with a haloepoxyalkane compound in the presence of a quaternary ammonium salt and a basic substance, and the obtained solid product is the bisphenol S epoxy resin;

[0013]

[0014] In formula (2), R7 and R8 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.

[0015] In a preferred embodiment, in step S1, the molar ratio of bisphenol S to the carbonate compound is 1:(1 to 4).

[0016] In a preferred embodiment, the carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, and 1,2-butylene carbonate.

[0017] In a preferred embodiment, the conditions of the first reaction include: an inert gas atmosphere, a reaction temperature of 150 to 240 °C, and a reaction time of 1 to 4 h.

[0018] In a preferred embodiment, in step S2, the mass ratio of the intermediate product to the haloepoxyalkane compound is 1:(3 to 20).

[0019] In a preferred embodiment, the chemical general formula of the haloepoxyalkane compound is X-R9-CHOCH2, where X is a halogen atom and R9 is an alkylene group with 1 to 5 carbon atoms.

[0020] In a preferred embodiment, the dosage of the quaternary ammonium salt is 1 to 5 wt% of the intermediate product.

[0021] In a preferred embodiment, the dosage of the basic substance is 5 to 15 wt% of the intermediate product.

[0022] In a preferred embodiment, the conditions of the second reaction include: an inert gas atmosphere; the reaction temperature is 80 to 120 °C, and the reaction time is 1 to 4 h.

[0023] In a preferred embodiment, the second reaction includes: mixing the obtained intermediate product with a haloepoxyalkane compound and a quaternary ammonium salt and heating to 80 to 120 °C, reacting for 1 to 4 h under the protection of an inert gas, then dropping the basic substance into the above mixture in the form of a solution, and then continuing to react for 1 to 3 h under the protection of an inert gas and at 80 to 120 °C. The solid obtained after filtration, washing, and drying is the bisphenol S epoxy resin.

[0024] In a preferred embodiment, the auxiliary agent is selected from at least one of a thixotropic agent, a stabilizer, a leveling agent, and an antifoaming agent.

[0025] A second object of the present invention is to provide a method for preparing the above epoxy adhesive, which includes: mixing a liquid epoxy resin, a bisphenol S epoxy resin, a liquid 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 the application of the above epoxy adhesive in the encapsulation of electronic components in a high-temperature welding environment.

[0027] Advantages: The key of the present invention lies in using liquid epoxy resin and bisphenol S epoxy resin with a specific structure as the main body, and on this basis, cooperating with a specific liquid curing agent (liquid aromatic amine curing agent) and optional coupling agent, filler, and auxiliary agent to form an epoxy adhesive. Since the molecular chain of bisphenol S epoxy resin contains -SO2- polar groups and a chain segment structure of -O-C-C-O-C(=O)-, on the one hand, it is beneficial to improve the bonding strength of the epoxy adhesive, and on the other hand, it can increase the flexibility of the molecular chain, reduce the rigidity of the molecule to a certain extent, improve the heat resistance and compressive capacity of the epoxy adhesive, and enhance the toughness of the colloid. At the same time, the liquid aromatic amine curing agent cooperates with bisphenol S epoxy resin, which is beneficial to reducing the viscosity of the epoxy adhesive system, improving its curing performance, and further increasing the glass transition temperature (Tg) after curing. Thus, the components cooperate with each other, making the epoxy resin adhesive have excellent heat resistance, a relatively high Tg value after curing, and improved compressive performance. It can still maintain a relatively 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. Detailed implementation mode

[0028] The epoxy adhesive provided by the present invention contains liquid epoxy resin, bisphenol S epoxy resin, a liquid curing agent, and optional coupling agent, filler, and auxiliary agent. The bisphenol S epoxy resin has the structure shown in formula (1);

[0029]

[0030] In formula (1), R1 and R2 are each independently an alkylene group with 1 to 5 carbon atoms, R3 to R6 are each independently a hydrogen atom or an alkyl group with 1 to 3 carbon atoms, and n is an integer from 1 to 5, such as 1, 2, 3, 4, 5. 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 3 carbon atoms include, but are not limited to: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl or tert-butyl.

[0031] In the present invention, the liquid curing agent is a liquid aromatic amine curing agent, and its specific examples include, but are not limited to: DL50 and 101 of Evonik Industries AG, MXDA of Mitsubishi Corporation, Ecure-11 of Shanghai Jituo Materials Technology Co., Ltd., Ethacure200 and Ethacure300 of Albemarle Corporation, etc. at least one of them.

[0032] In the present invention, the content of the liquid epoxy resin is preferably 20 to 30 parts by weight, such as 20, 22, 25, 28, 30 parts by weight or any value therebetween. The content of the bisphenol S epoxy resin is preferably 30 to 50 parts by weight, such as 30, 35, 40, 45, 50 parts by weight or any value therebetween. The content of the liquid curing agent is preferably 10 to 25 parts by weight, such as 10, 12, 15, 18, 20, 22, 25 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, 1.5, 2 parts by weight or any value therebetween. The content of the filler is preferably 0 to 20 parts by weight, such as 0, 5, 10, 12, 15, 18, 20 parts by weight or any value therebetween. The content of the auxiliary agent is preferably 0 to 5 parts by weight, such as 0, 0.1, 0.2, 0.5, 1, 2, 3, 4, 5 parts by weight or any value therebetween.

[0033] In the present invention, the viscosity of the liquid epoxy resin at 25 °C is preferably 1000 to 5500 mPa·s, such as 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 5000 mPa·s, 5500 mPa·s or any value therebetween. The liquid epoxy resin can be any one of the existing liquid epoxy resins satisfying a viscosity of 1000 to 5000 mPa·s at 25 °C, and is preferably bisphenol A epoxy resin and / or bisphenol F epoxy resin. Controlling the viscosity of the liquid epoxy resin within the above preferred range is conducive to the sufficient and uniform mixing between the liquid epoxy resin, the bisphenol S epoxy resin, the liquid curing agent and other optional raw materials, thereby improving the curing performance and bonding performance of the epoxy adhesive.

[0034] In the present invention, the bisphenol S epoxy resin is preferably prepared by the following method: S1. Bisphenol S and a carbonate compound having a structure shown in formula (2) are subjected to a first reaction in the presence of a catalyst to obtain an intermediate product; S2. The obtained intermediate product and a haloepoxyalkane compound are subjected to a second reaction in the presence of a quaternary ammonium salt and a basic substance, and the obtained solid product is the bisphenol S epoxy resin;

[0035]

[0036] In formula (2), R7 and R8 are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Specific examples of the alkyl group having 1 to 3 carbon atoms are as described above and will not be elaborated herein one by one.

[0037] In the present invention, in step S1, the molar ratio of bisphenol S to the carbonate compound is preferably 1:(1 - 4). Based on 1 mol of bisphenol S, the amount of the carbonate compound is preferably 1 - 4 mol, such as 1 mol, 1.5 mol, 2 mol, 3 mol, 4 mol or any value therebetween.

[0038] In the present invention, in step S1, the carbonate compound may be a kind of compound having the structure shown in formula (2), and is preferably at least one selected from ethylene carbonate, propylene carbonate, 1,2-butylene carbonate.

[0039] In the present invention, in step S1, the conditions of the first reaction preferably include: an inert gas atmosphere, such as inert gases like nitrogen, argon, xenon, etc.; the reaction temperature is 150 - 240 °C, such as 150 °C, 170 °C, 200 °C, 220 °C, 240 °C or any value therebetween; the reaction time is 1 - 4 h, such as 1 h, 2 h, 3 h, 4 h or any value therebetween.

[0040] In the present invention, in step S2, the mass ratio of the intermediate product to the haloepoxyalkane compound is preferably 1:(3 - 20), such as 1:3, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20 or any value therebetween.

[0041] In the present invention, in step S2, the haloepoxyalkane compound may be a kind of compound having the chemical general formula X-R9-CHOCH2 structure, and it may specifically be any commercially available compound having the above chemical general formula structure. Among them, X is a halogen atom, such as a chlorine atom, a bromine atom or an iodine atom; R9 is an alkylene group with 1 - 5 carbon atoms, and its specific examples are as described above and will not be elaborated here one by one. Considering the availability of raw materials, the second haloepoxyalkane compound is particularly preferably epichlorohydrin and / or epichlorobutane.

[0042] In the present invention, in step S2, the quaternary ammonium salt is a kind of compound formed by replacing all four hydrogen atoms in the ammonium ion with hydrocarbon groups, and its chemical general formula is (R)4-N-X, where X is one of a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and R is preferably an alkyl group with 1 - 5 carbon atoms. Specific examples of the quaternary ammonium salt include, but are not limited to: at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetrapropylammonium bromide, tetrabutylammonium bromide, tetrapentylammonium bromide, tetramethylammonium fluoride, tetramethylammonium chloride, tetramethylammonium iodide, and is preferably at least one of tetramethylammonium bromide, tetraethylammonium bromide, tetramethylammonium chloride.

[0043] The dosage of the quaternary ammonium salt is preferably 1-5 wt% of the intermediate product, such as 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt% or any value between them.

[0044] In the present invention, in step S2, the conditions of the second reaction preferably include: an inert gas atmosphere, such as inert gases like nitrogen, argon, xenon, etc.; the reaction temperature is 80-120 °C, such as 80 °C, 90 °C, 100 °C, 110 °C, 120 °C or any value between them; the reaction time is 3-8 h, such as 3 h, 4 h, 5 h, 6 h, 7 h, 8 h or any value between them.

[0045] In the present invention, the intermediate product, the haloepoxyalkane compound, the quaternary ammonium salt, and the basic substance can be mixed in any order and manner and then subjected to the second reaction. Preferably, the second reaction may include the following steps: mixing the obtained intermediate product with the haloepoxyalkane compound and the quaternary ammonium salt and heating to 80-120 °C, reacting for 1-3.5 h under inert gas protection, then dropping the basic substance into the above mixture in the form of a solution, and then continuing to react for 1-3 h under inert gas protection and at 80-120 °C. The solid obtained after filtration, washing, and drying is the bisphenol S epoxy resin. Among them, the time for dropping the basic substance in the form of a solution is preferably completed within 2-3 h.

[0046] In a specific embodiment, the second reaction is carried out in the following manner: first dissolve the intermediate product in the haloepoxyalkane compound, add the quaternary ammonium salt after heating to 80-120 °C, react for 1-4 h under an inert gas atmosphere, then drop the basic substance into the above mixture in the form of a solution, and then continue to react for 1-3 h under inert gas protection and at 80-120 °C. The solid obtained after filtration, washing, and drying is the bisphenol S epoxy resin.

[0047] In the present invention, in step S2, the basic substance only needs to be a kind of compound that can provide a basic environment for the reaction system, and is preferably independently selected from at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate. The dosage of the basic substance is preferably 5-15 wt% of the intermediate product, such as 5 wt%, 8 wt%, 10 wt%, 12 wt%, 15 wt% or any value between them.

[0048] Specific examples of the coupling agent in the present invention 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.

[0049] 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, titanium dioxide, etc.).

[0050] In the present invention, specific examples of the additives include, but are not limited to, at least one of thixotropic agents, stabilizers, polymerization inhibitors, antioxidants, flame retardants, adhesion promoters, dyes, pigments, defoamers, leveling agents, homogenizing agents, and ion scavengers. The additives are preferably selected from at least one of thixotropic agents, stabilizers, leveling agents, and defoamers, and particularly preferably a thixotropic agent. The thixotropic agent is preferably fumed silica, and specifically, it can be selected from at least one of H8, H20, H30 of Waker Company, TS-530, TS720 of Cabot Company, and R972, R974, R976, R202, R8200 of Degussa Company.

[0051] In the present invention, the preparation method of the epoxy adhesive includes: mixing liquid epoxy resin, bisphenol S epoxy resin, liquid curing agent, and optionally coupling agent, filler, and additive under vacuum conditions, and then the epoxy adhesive is obtained.

[0052] In a specific embodiment, the preparation method of the epoxy adhesive includes: adding liquid epoxy resin, bisphenol S epoxy resin, and optionally coupling agent into a double planetary hybrid reactor and stirring evenly under vacuum conditions through a first mixing treatment, then adding liquid curing agent and stirring evenly under vacuum conditions through a second mixing treatment, and optionally, continuing to add filler and additive and stirring evenly under vacuum conditions through a third mixing treatment, and then the epoxy adhesive is obtained.

[0053] Further, the vacuum condition is preferably a vacuum degree ≤ 0.098 MPa.

[0054] Further, the temperature of the first mixing treatment 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 beneficial to accelerate the mixing speed. The time of the first mixing treatment is not specifically limited as long as the liquid epoxy resin, bisphenol S epoxy resin, and optionally coupling agent can be evenly mixed.

[0055] Further, the temperatures of the second mixing treatment and the third mixing treatment 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 treatment and the third mixing treatment are not specifically limited as long as the added raw materials can be evenly mixed.

[0056] In addition, the terms "first", "second", and "third" are for the purpose of description only and should not be construed as limiting the type or quantity of the defined technical features.

[0057] The present invention will be described in detail below through 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 the field or according to the product specifications are followed. For reagents or instruments without the manufacturer noted, they are all conventional products that can be obtained through commercial purchase.

[0058] In the following examples and comparative examples, the parts of each raw material refer to parts by weight.

[0059] Sources of raw materials involved in the following examples and comparative examples: Bisphenol A epoxy resin, purchased from Dainippon Ink and Chemicals, Inc., grade 850CPR, with a viscosity of 3500 - 5500 mPa·s at 25°C; Bisphenol A epoxy resin, purchased from Hexion Inc., USA, grade EPON 872, with a viscosity of 1500 - 3800 mPa·s at 25°C; Bisphenol F epoxy resin, purchased from Nan Ya Plastics Corporation, Taiwan, China, grade NPEF-170, with a viscosity of 2000 - 5000 mPa·s at 25°C; Bisphenol A epoxy resin, purchased from Dainippon Ink and Chemicals, Inc., grade 840S, with a viscosity of 9000 - 11000 mPa·s at 25°C; Bisphenol A epoxy resin, purchased from Hexion Inc., USA, grade EPON 815C, with a viscosity of 500 - 700 mPa·s at 25°C.

[0060] The epoxy equivalent involved in the following examples and comparative examples was 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. 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 (g) of the sample to be measured, N is the concentration (mol / L) of the perchloric acid - glacial acetic acid standard solution, and S is the volume (mL) of the perchloric acid - glacial acetic acid standard solution consumed in the titration.

[0061] Preparation Example 1

[0062] In a four-necked flask equipped with a mechanical stirrer paddle, a thermometer, a condenser, and a constant-pressure funnel, 2 g of Na2CO3, 100 g of bisphenol S (0.4 mol), and 80 g of ethylene carbonate (0.91 mol) were added. After complete melting and reaction at 180 °C for 3 h under nitrogen protection, the intermediate product 1 was washed with deionized water; 120 g of intermediate product 1 and 800 g of epichlorohydrin were added to the reaction vessel to dissolve into a mixture. After the temperature was raised to 90 °C, 6 g of tetraethylammonium bromide was added, and an etherification reaction was carried out at 90 °C under nitrogen protection for 3.5 h; 24 g of an aqueous NaOH solution (concentration 50 wt%) was added dropwise over 2.5 h. After the addition was complete, the reaction continued at 90 °C under nitrogen protection for 2 h. The solid was obtained by vacuum filtration, and the product was repeatedly washed with deionized water until the pH value of the washing solution was about 7. The solid obtained after drying was bisphenol S epoxy resin 1.

[0063] It was proved by testing that the bisphenol S epoxy resin 1 has the structure shown in formula (1), where R1 and R2 are methylene groups, R3 to R6 are all hydrogen atoms, and n is 3. By epoxy equivalent testing, the epoxy equivalent of bisphenol S epoxy resin 1 is 585 g / eq, which is close to the theoretical value, verifying the successful preparation of bisphenol S epoxy resin 1 with the above structure.

[0064] Preparation Example 2

[0065] In a four-necked flask equipped with a mechanical stirrer paddle, a thermometer, a condenser, and a constant-pressure funnel, 2 g of MgCO3, 100 g of bisphenol S (0.4 mol), and 80 g of 1,2-butene carbonate (0.69 mol) were added. After complete melting and reaction at 220 °C for 3 h under nitrogen protection, the intermediate product 1 was washed with deionized water; 100 g of intermediate product 1 and 400 g of epichlorohydrin were added to the reaction vessel to dissolve into a mixture. After the temperature was raised to 95 °C, 6 g of tetramethylammonium bromide was added, and an etherification reaction was carried out at 95 °C under nitrogen protection for 1.5 h; 24 g of an aqueous NaOH solution (concentration 50 wt%) was added dropwise over 2.5 h. After the addition was complete, the reaction continued at 95 °C under nitrogen protection for 2 h. The solid was obtained by vacuum filtration, and the product was repeatedly washed with deionized water until the pH value of the washing solution was about 7. The solid obtained after drying was bisphenol S epoxy resin 2.

[0066] It was proved by testing that the bisphenol S epoxy resin 2 has the structure shown in formula (1), where R1 and R2 are methylene groups, R3 and R6 are hydrogen atoms, R4 and R5 are ethyl groups, and n is 2. By epoxy equivalent testing, the epoxy equivalent of bisphenol S epoxy resin 1 is 475 g / eq, which is close to the theoretical value, verifying the successful preparation of bisphenol S epoxy resin 2 with the above structure.

[0067] Preparation Example 3

[0068] In a four-necked flask equipped with a mechanical stirrer paddle, a thermometer, a condenser, and a constant-pressure funnel, 2 g of K2CO3, 100 g of bisphenol S (0.4 mol), and 120 g of propylene carbonate (1.18 mol) were added. After complete melting and reaction at 200 °C under nitrogen protection for 4 h, the intermediate product 1 was washed with deionized water; 150 g of intermediate product 1 and 880 g of epichlorohydrin were added to the reaction vessel to dissolve into a mixture. After the temperature was raised to 95 °C, 6 g of tetramethylammonium chloride was added, and an etherification reaction was carried out at 95 °C under nitrogen protection for 2 h; 20 g of an aqueous NaOH solution (concentration 50 wt%) was added dropwise over 3 h. After the addition was complete, the reaction was continued at 95 °C under nitrogen protection for 2.5 h. The solid was obtained by vacuum filtration, and the product was repeatedly washed with deionized water until the pH value of the washing solution was about 7. The solid obtained after drying was bisphenol S epoxy resin 3.

[0069] It was proved by testing that the bisphenol S epoxy resin 3 has the structure shown in formula (1), where R1 and R2 are ethylidene, R3 and R6 are hydrogen atoms, R4 and R5 are methyl groups, and n is 2. By testing the epoxy equivalent, the epoxy equivalent of bisphenol S epoxy resin 1 was 440 g / eq, which was close to the theoretical value, verifying the successful preparation of bisphenol S epoxy resin 3 with the above structure.

[0070] Example 1

[0071] S1. 30 parts of bisphenol A epoxy resin 850 CPR, 30 parts of bisphenol S epoxy resin 1, and 1 part of γ-mercaptopropyltriethoxysilane were successively added to a double-planet hybrid reactor, and the temperature was controlled at 75 °C and stirred evenly under vacuum;

[0072] S2. After the temperature was lowered to 25 °C, 23 parts of the 101 curing agent from Evonik Industries AG was added to the reactor in step S1 and stirred evenly under vacuum;

[0073] S3. 15 parts of light calcium carbonate and 1 part of Cabot's TS720 fumed silica were added to the reactor in step S2. After stirring evenly under vacuum, the product was discharged to obtain an epoxy adhesive, denoted as A1.

[0074] Example 2

[0075] S1. 20 parts of bisphenol A epoxy resin EPON 872, 50 parts of bisphenol S epoxy resin 2, and 0.5 part of γ-methacryloxypropyltrimethoxysilane were successively added to a double-planet hybrid reactor, and the temperature was controlled at 75 °C and stirred evenly under vacuum;

[0076] S2. After the temperature was lowered to 25 °C, 10 parts of the Ethacure 200 curing agent from Albemarle Corporation was added to the reactor in step S1 and stirred evenly under vacuum;

[0077] S3. Add 19 parts of light calcium carbonate, 0.1 part of carbon black, and 0.4 part of R972 fumed silica from Degussa to the reaction kettle in step S2. After stirring evenly under vacuum, the epoxy adhesive can be discharged, denoted as A2.

[0078] Example 3

[0079] S1. Add 25 parts of bisphenol F epoxy resin NPEF-170, 42 parts of bisphenol S epoxy resin 3, and 1.5 parts of γ-mercaptopropyltriethoxysilane to the double planetary hybrid reaction kettle in sequence. Control the temperature at 75 °C and stir evenly under vacuum;

[0080] S2. After reducing the temperature to 25 °C, add 18 parts of Ecure-11 curing agent from Shanghai Jituo Materials Technology Co., Ltd. to the reaction kettle in step S1 and stir evenly under vacuum;

[0081] S3. Add 11 parts of bentonite and 2.5 parts of H8 fumed silica from Waker to the reaction kettle in step S2. After stirring evenly under vacuum, the epoxy adhesive can be discharged, denoted as A3.

[0082] Example 4

[0083] Prepare the epoxy adhesive according to the method of Example 1, except that the same amount of bisphenol A epoxy resin 840S (viscosity at 25 °C is 9000 - 11000 mPa·s) is used instead of bisphenol A epoxy resin 850CPR (viscosity at 5 °C is 3500 - 5500 mPa·s), and the other conditions are the same as those in Example 1. Thus, the prepared epoxy adhesive is denoted as A4.

[0084] Example 5

[0085] Prepare the epoxy adhesive according to the method of Example 1, except that the same amount of bisphenol A epoxy resin EPON 815C (viscosity at 25 °C is 500 - 700 mPa·s) is used instead of bisphenol A epoxy resin 850CPR (viscosity at 25 °C is 3500 - 5500 mPa·s), and the other conditions are the same as those in Example 1. Thus, the prepared epoxy adhesive is denoted as A5.

[0086] Comparative Example 1

[0087] Prepare the reference epoxy adhesive according to the method of Example 1, except that the same amount of bisphenol S epoxy resin 300SS from Compton, USA (detected that its molecular structure does not contain carbonate derivative group structure) is used instead of bisphenol S epoxy resin 1, and the other conditions are the same as those in Example 1. Thus, the prepared reference epoxy adhesive is denoted as DA1.

[0088] Comparative Example 2

[0089] The reference epoxy adhesive was prepared according to the method of Example 1, except that bisphenol A epoxy resin 850CPR with the same weight parts was used to replace bisphenol S epoxy resin 1, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive was obtained and denoted as DA3.

[0090] Comparative Example 3

[0091] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same parts of aliphatic amine curing agent Baxxodur EC280 (purchased from BASF Group, Germany) were used to replace Curing agent 101, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive was obtained and denoted as DA4.

[0092] Comparative Example 4

[0093] The reference epoxy adhesive was prepared according to the method of Example 1, except that the same parts of liquid imidazole curing agent API (purchased from BASF Group, Germany) were used to replace Curing agent 101, and the other conditions were the same as those in Example 1. Thus, the reference epoxy adhesive was obtained and denoted as DA5.

[0094] Test Example

[0095] The epoxy adhesives prepared in the above examples and comparative examples were subjected to shear strength, high-temperature resistance, glass transition temperature (Tg), toughness, and reflow soldering tests according to the following methods, and the results are shown in Table 1.

[0096] (1) Shear strength test: The test was carried out according to the method in Standard GB / T 7124-2008. The epoxy adhesives obtained in the above examples and comparative examples were used to prepare stainless steel-to-stainless steel shear specimens with a lap area of 25.4 mm * 12.7 mm and an adhesive layer thickness of 0.2 mm. After curing at 120 °C for 60 min, the shear strengths at 25 °C, 130 °C, and 200 °C were respectively tested, and the tensile speed was 5 mm / min.

[0097] (2) High-temperature resistance test: The epoxy adhesives obtained in the above examples and comparative examples were used to prepare stainless steel-to-stainless steel shear specimens with a lap area of 25.4 mm * 12.7 mm and an adhesive layer thickness of 0.2 mm. After curing at 120 °C for 60 min, the shear strength was tested after standing at room temperature until it reached room temperature, denoted as S 25℃Prepare stainless-steel-to-stainless-steel shear specimens with a lap area of 25.4 mm × 12.7 mm and an adhesive layer thickness of 0.2 mm from the epoxy adhesives obtained in the above examples and comparative examples. After curing under the conditions of 120°C for 60 min, place the prepared shear specimens in an ESPEC oven with the temperature set at 220°C. Take out the specimens after 5 days and 10 days respectively, and then place them at room temperature until they reach room temperature, and then test their shear strength, denoted as S` 25℃ 、S`` 25℃ , and calculate the remaining shear strength D 5day =(S 25℃ -S` 25℃ ) / S 25℃ after 5 days of placement and the remaining shear strength D 10day =(S 25℃ -S`` 25℃ ) / S 25℃ after 10 days of placement. The higher the proportion of the remaining shear strength, the better the heat resistance of the cured adhesive.

[0098] (3) Glass transition temperature (Tg) test: Under the condition of an N2 intake of 100 mL / min, perform dynamic thermomechanical analysis (TMA) test on the specimen using a TA Discovery TMA450 analyzer. Under a force of 0.20 N, bring the specimen into contact with the bending probe, and then heat the specimen from 0°C to 250°C at a rate of 5°C / min. During the test cycle, adjust the force by ±0.08 N at a frequency of 0.10 Hz. Thus, the glass transition temperature (Tg) of the epoxy adhesive is measured, and the data is the average of three independent runs.

[0099] (4) Toughness test: Refer to the standard of GB / T 528-2009 "Determination of Tensile Stress-Strain Properties of Vulcanized Rubber or Thermoplastic Rubber", prepare dumbbell specimens of type 4 with a thickness of 0.4 mm, and test the dumbbell specimens 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. Place the dumbbell specimens in an ESPEC oven with the temperature set at 220°C. Take out the specimens after 5 days and 10 days, and then place them at room temperature until they reach room temperature and then conduct the test to obtain the elongation at break data after 5 days and 10 days of aging.

[0100] (5) Reflow soldering test: Apply glue to the relay components for dotting and sealing treatment. After curing at 120°C for 60 minutes, conduct a water leak test before reflow soldering (put the relay in water, heat it up to 100°C, and boil for 1 - 2 minutes. If there is a problem with the sealing, air bubbles will overflow from the relay). Use the Rehm lead-free hot air reflow soldering machine CR-1002 for reflow soldering treatment. Set the reflow soldering process to 5 minutes, the preheating temperature to 150°C, the heating rate to 3°C / s, the starting soldering temperature to 220°C, the maximum temperature to 260°C, the soldering time to 60 seconds, the time above 250°C to about 5 - 10 seconds, and end the reflow soldering process after cooling to below 50°C. Conduct a water leak test on the relay after reflow soldering (put the relay in water, heat it up to 100°C, and boil for 1 - 2 minutes. If there is a problem with the sealing, air bubbles will overflow from the relay), and calculate the failure ratio. For the relays with intact sealing and no leakage, conduct another reflow soldering treatment, check the sealing of the relays, and calculate the failure ratio. The higher the failure ratio, the worse the heat resistance and heat compression resistance of the glue.

[0101] Table 1

[0102]

[0103] From the results in Table 1, it can be seen that compared with Comparative Examples 1 - 4, the epoxy adhesives provided in Examples 1 - 5 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 they can withstand 2 reflow soldering processes without leakage. From the results of Example 1 and Comparative Example 1, it can be seen that using the conventional bisphenol S epoxy resin on the market (whose molecular structure does not contain a carbonate derivative group structure) to replace bisphenol S epoxy resin 1 with a specific structure 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 elongation at break at room temperature and the remaining strength and elongation at break after high-temperature aging at 200°C for 5 days and 10 days, and an increase in the leakage ratio of electronic components after 1 and 2 reflow soldering processes. From the results of Example 1 and Comparative Example 2, it can be seen that when only bisphenol S epoxy resin 1 is used as the resin component in the epoxy adhesive, the shear strength of the epoxy adhesive 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 significantly reduced, and the leakage ratio of electronic components after 1 and 2 reflow soldering processes increases significantly. From the results of Example 1 and Comparative Examples 3 and 4, it can be seen that when using a fatty amine curing agent or a liquid imidazole curing agent to replace the liquid aromatic amine curing agent, the 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 decrease, and the leakage ratio of electronic components after 1 and 2 reflow soldering processes increases.

[0104] 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 liquid epoxy resin, bisphenol S epoxy resin, liquid curing agent and optional coupling agent, filler and auxiliary agent; the liquid curing agent is a liquid aromatic amine curing agent; the bisphenol S epoxy resin has a structure as shown in formula (1); In formula (1), R1 and R2 are each independently a C1-C5 alkylene group, R3-R6 are each independently a hydrogen atom or a C1-C3 alkyl group, and n is an integer of 1-5.

2. The epoxy adhesive according to claim 1, characterized in that: The content of the liquid epoxy resin is 20 to 30 parts by weight, the content of the bisphenol S epoxy resin is 30 to 50 parts by weight, the content of the liquid curing agent is 10 to 25 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 5 parts by weight.

3. The epoxy adhesive according to claim 1, characterized in that: The liquid epoxy resin is bisphenol A epoxy resin and / or bisphenol F epoxy resin; Preferably, the viscosity of the liquid epoxy resin at 25° C. is 1000 to 5500 mPa·s.

4. The epoxy adhesive according to claim 1, characterized in that: The preparation method of the bisphenol S epoxy resin comprises: S1. A first reaction is performed by reacting bisphenol S with a carbonate compound having a structure as shown in formula (2) in the presence of a catalyst to obtain an intermediate product; S2. The intermediate product obtained is subjected to a second reaction with a halogenated epoxy alkylene compound in the presence of a quaternary ammonium salt and an alkaline substance, and the resulting solid product is a bisphenol S epoxy resin; In formula (2), R7 and R8 are each independently a hydrogen atom or a C1-C3 alkyl group.

5. The epoxy adhesive according to claim 4, characterized in that: In step S1, the molar ratio of bisphenol S to carbonate compound is 1:(1-4); Preferably, the carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate and 1,2-butylene carbonate; Preferably, the conditions of the first reaction include: an inert gas atmosphere, a reaction temperature of 150 to 240° C., and a reaction time of 1 to 4 hours.

6. The epoxy adhesive according to claim 4, characterized in that: In step S2, the mass ratio of the intermediate product to the halogenated epoxyalkane compound is 1:(3-20); Preferably, the chemical formula of the halogenated epoxyalkane compound is X-R9-CHOCH2, wherein X is a halogen atom and R9 is a C1-C5 alkylene group; Preferably, the quaternary ammonium salt is used in an amount of 1 to 5 wt % of the intermediate product; Preferably, the amount of the alkaline substance used is 5-15 wt % of the intermediate product.

7. The epoxy adhesive according to claim 4, characterized in that: In step S2, the conditions of the second reaction include: an inert gas atmosphere, a reaction temperature of 80 to 120° C., and a reaction time of 3 to 8 hours. Preferably, the second reaction comprises: mixing the obtained intermediate product with a halogenated epoxy alkylene compound and a quaternary ammonium salt and heating the mixture to 80 to 120° C., reacting the mixture for 1 to 4 hours under the protection of an inert gas, then dropping the alkaline substance into the mixture in the form of a solution, and then continuing the reaction for 1 to 3 hours under the protection of an inert gas at 80 to 120° C., and filtering, washing and drying the solid to obtain the bisphenol S epoxy resin.

8. The epoxy adhesive according to claim 1, characterized in that: The auxiliary agent is selected from at least one of a thixotropic agent, a stabilizer, a leveling agent, and a defoaming agent.

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 liquid epoxy resin, bisphenol S epoxy resin, liquid 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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