Low-temperature curing epoxy adhesive with high modulus and high elongation at break as well as preparation method and application of low-temperature curing epoxy adhesive

Abstract

The invention provides a low-temperature curing epoxy adhesive with high modulus and high elongation at break and a preparation method of the low-temperature curing epoxy adhesive, and belongs to the technical field of adhesives. The epoxy adhesive comprises the following components in parts by mass: 100 parts of mixed epoxy resin, 0.1-5 parts of a coupling agent, 0.1-5 parts of a stabilizer, 40-100 parts of a curing agent and 2-10 parts of a curing accelerator. Every 100 parts of the mixed epoxy resin comprises 10-30 parts of liquid epoxy resin A, 10-30 parts of solid epoxy resin B, 10-30 parts of a diluent C and 30-60 parts of modified epoxy resin D. The modified epoxy resin D is obtained by reacting diisocyanate with a polyol polymer in the presence of a catalyst and reacting a reaction product with glycidyl. The epoxy adhesive has the characteristics of high modulus, high elongation at break, low curing temperature and good humidity and heat resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials, in particular to the technical field of adhesives, and specifically relates to a low-temperature curing epoxy adhesive with high modulus and high elongation at break, and a preparation method and application thereof. Background Art

[0002] Epoxy resin is a general term for compounds containing epoxy groups. Due to its good adhesion, corrosion resistance, electrical insulation, high strength and other characteristics, it is widely used in adhesives, seals, potting, molding compounds and other fields, involving electronics, industry, aviation and other industries. The vast majority of single-component epoxy adhesives are thermosetting products. According to their curing temperature, products cured at 60℃-90℃ are classified as low-temperature curing products. Low-temperature curing epoxy adhesives are widely used in key components of consumer electronics, such as screens, cameras, fingerprint modules, acoustic modules, chips and other devices that are not heat-resistant. At the same time, these devices are relatively sophisticated, involving the intersection of optics, acoustics, electronics and structures, and the application scenarios are complex, with strict requirements on the bonding performance, modulus and toughness of the adhesive.

[0003] The Chinese patent application publication CN117801209A discloses a polyurethane-modified epoxy resin and a preparation method thereof, and a novel polyurethane-modified epoxy resin is prepared by the addition reaction of polyisocyanate and epoxy resin. The modified epoxy resin has high shear strength after curing at room temperature, and good double 85 performance, but the elongation at break is only 28%-34%, and the toughness is poor. CN112300741A discloses a two-component epoxy adhesive that cures quickly at room temperature, with a tensile strength greater than 10MPa, an elongation at break greater than 100%, and good bonding performance for metal materials such as stainless steel. However, the epoxy adhesive is a two-component adhesive, which is limited in use in most single-component application scenarios, and the tensile strength is still not high enough. CN115785866A discloses a single-component low-temperature curing epoxy adhesive with low modulus and high bonding strength, which can achieve rapid curing at 80°C, and at low modulus (<300MPa), there is no cracking after cold and hot shock. However, the epoxy adhesive has poor toughness and cracking when the modulus is high.

[0004] In summary, when the modulus of epoxy adhesives in the prior art is high, the bonding performance is better, but the toughness will deteriorate, and there is a risk of device failure during falling or hot and cold shock; when the modulus is low, a higher elongation at break can be achieved, but the material is soft, and some precision devices will have a large displacement at the bonding part when disturbed, affecting the accuracy of the device, and the bonding force and heat resistance will deteriorate. Therefore, the development of a low-temperature curing epoxy adhesive with high modulus and high elongation at break is of great significance for the high-reliability bonding of key devices in the consumer electronics industry. Summary of the invention

[0005] In view of the above problems, the present invention provides a low-temperature curing epoxy adhesive with high modulus and high elongation at break and a preparation method thereof. After epoxy resin is modified by polyurethane, it is matched with liquid epoxy resin, solid epoxy resin and diluent, and then with curing agent and other components to prepare a single-component low-temperature curing epoxy adhesive with both high modulus and high elongation at break. The epoxy adhesive has high adhesion and wet heat reliability to both polycarbonate (PC) and stainless steel.

[0006] In order to achieve the above object, the present invention specifically adopts the following technical solutions: A low-temperature curing epoxy adhesive with high modulus and high elongation at break comprises the following components, measured in parts by mass: 100 parts of a mixed epoxy resin, 0.1-5 parts of a coupling agent, 0.1-5 parts of a stabilizer, 40-100 parts of a curing agent, and 1-6 parts of a curing accelerator; wherein every 100 parts of the mixed epoxy resin comprises 10-30 parts of a liquid epoxy resin A, 10-30 parts of a solid epoxy resin B, 10-30 parts of a diluent C, and 30-60 parts of a modified epoxy resin D; the modified epoxy resin D is obtained by reacting a diisocyanate and a polyol polymer in the presence of a catalyst, and then reacting the reaction product with glycidol.

[0007] In a preferred embodiment, the liquid epoxy resin A includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin.

[0008] In a preferred embodiment, the solid epoxy resin B is selected from any one or a combination of epoxy resins of types DER671, DER662E, DER663U, and DER664U.

[0009] In a preferred embodiment, the diluent C is at least one of trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, dibromoneopentyl glycol diglycidyl ether, castor oil triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0010] In a preferred embodiment, the coupling agent is a silicon-based coupling agent and / or a titanate coupling agent.

[0011] In a further preferred embodiment, the silicon-based coupling agent is at least one of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, 3-glycidylpropylmethyldiethoxysilane, 3-glycidylpropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane.

[0012] In a further preferred embodiment, the titanate coupling agent is at least one of the products of model PlenactTTS and / or Plenact 46B produced by Ajinomoto Co., Ltd. of Japan.

[0013] In a preferred embodiment, the stabilizer is an organic acid.

[0014] In a further preferred embodiment, the stabilizer is at least one of fumaric acid, barbituric acid, salicylic acid and citric acid.

[0015] In a preferred embodiment, the curing agent is at least one of trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis-3-mercaptopropionate, pentaerythritol tetrakisthioacetate, and pentaerythritol tetrakis(3-mercaptobutyrate).

[0016] In a further preferred embodiment, the curing accelerator is at least one of the FXR series products of Fuji Chemical Co., Ltd., Japan, the PN series products of Ajinomoto Co., Ltd., Japan, the MY series products of Ajinomoto Co., Ltd., Japan, and the EH-50 series products of Aidico Co., Ltd., Japan.

[0017] In a preferred embodiment, the preparation method of the modified epoxy resin D comprises the following steps: P1. Add diisocyanate and polyol polymer into a reaction container at a molar ratio of (-N=C=O):(-OH) of (2.06-2.12):1, then add catalyst E accounting for 0.05%-0.2% of the total mass of diisocyanate and polyol polymer, and control the temperature of the reaction system to 10°C-30°C under an inert gas atmosphere for 1-3 hours to obtain a prepolymer F; P2. Under an inert gas atmosphere, add glycidol into a reaction container; the amount of glycidol is added according to the molar ratio of -OH in glycidol to -N=C=O in prepolymer F of (1.01~1.03):1; heat to 50°C~80°C and react for 2~4 hours to obtain modified epoxy resin D.

[0018] In a further preferred embodiment, the diisocyanate is selected from any one or a combination of MDI, PAPI, TDI, XDI, HDI, HMDI, and IPDI.

[0019] In a further preferred embodiment, the polyol polymer is selected from at least one of polyether polyols, bio-based polyols, and polyester polyols.

[0020] In a further preferred embodiment, the catalyst E is dibutyltin dilaurate.

[0021] The present invention also provides a method for preparing the epoxy adhesive in any of the above schemes, comprising the following steps: S1, respectively adding the mixed epoxy resin, the coupling agent and the stabilizer into a planetary mixer with cooling function and high-speed dispersing function, evacuating to a vacuum degree of ≤-96KPa, with an orbital speed of 20-40rpm, a high-speed dispersing speed of 800-1200rpm, and stirring for 30-60 minutes; S2, add the curing agent to the planetary mixer, evacuate to a vacuum degree of ≤-96KPa, the revolution speed is 20-40rpm, the high-speed dispersion speed is 800-1200rpm, and stir for 30-60 minutes; at the same time, pass ice water to control the temperature of the reaction system to ≤30°C; S3, adding the curing accelerator to the planetary mixer, evacuating to a vacuum degree of ≤-96KPa, the revolution speed is 20-40rpm, the high-speed dispersion speed is 1000-1400rpm, and stirring for 30-60 minutes; at the same time, passing ice water to control the temperature of the reaction system to ≤30°C; after the stirring is completed, discharging and packaging to obtain an epoxy adhesive.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: (1) In the present application, a low-temperature curing epoxy adhesive having high modulus (>1300MPa), high elongation at break (>110%), high strength and high toughness was prepared by rationally combining a homemade modified epoxy resin with a liquid epoxy resin, a solid epoxy resin and a diluent.

[0023] (2) The epoxy adhesive provided in this application also has a high initial shear strength (>22MPa) and good moisture and heat resistance.

[0024] (3) The epoxy adhesive provided in this application has high adhesion and wet heat reliability to both polycarbonate (PC) and stainless steel.

[0025] (4) The epoxy adhesive in the present application can ensure the adhesion to materials of consumer electronic modules (such as camera modules, fingerprint modules, acoustic modules, etc.) while avoiding the problem of displacement of the bonding parts due to poor toughness and low elongation at break of the adhesive, which in turn leads to deterioration of device precision. It can also avoid the problem of deterioration of device precision due to poor moisture and heat resistance of the adhesive. DETAILED DESCRIPTION

[0026] The following content is combined with the embodiments to clearly and completely describe the technical solution of the present application so that those skilled in the art can fully understand the present application. Obviously, the described embodiments are only some preferred embodiments of the present application, rather than all embodiments. Any equivalent transformation or substitution made to the following implementation modes by those of ordinary skill in the art without creative work belongs to the protection scope of the present application.

[0027] The bisphenol F epoxy resin EPICLON EXA-830LVP used in the following examples is a product of DIC Corporation of Japan. Solid epoxy resin DER671 is a product of Dow Chemical Company of the United States. Curing agent Karenz MT PE1 (CAS No.: 31775-89-0) is a product of Showa Corporation of Japan. Trimethylolpropane tris (3-mercaptopropionate) is a product of SC Organic Chemical Co., Ltd. of Japan. Curing accelerator FXR1020 is a product of Fuji Chemical Co., Ltd. of Japan. PN-23J is a product of Ajinomoto Co., Ltd. of Japan.

[0028] A specific embodiment of the present invention provides a method for preparing a low temperature curing epoxy adhesive, comprising the following steps: S1. In parts by mass, 100 parts of mixed epoxy resin, 0.1-5 parts of coupling agent and 0.1-5 parts of stabilizer are respectively added into a planetary mixer with cooling function and high-speed dispersing function, evacuated to a vacuum degree of ≤-96KPa, the revolution speed is 20-40rpm, the high-speed dispersing speed is 800-1200rpm, and stirred for 30-60 minutes; wherein, every 100 parts of mixed epoxy resin includes 10-30 parts of liquid epoxy resin A, 10-30 parts of solid epoxy resin B, 10-30 parts of diluent C, and 30-60 parts of modified epoxy resin D; the modified epoxy resin D is obtained by reacting a diisocyanate and a polyol polymer in the presence of a catalyst, and then reacting the reaction product with glycidol.

[0029] S2. Add 40-100 parts of curing agent to the planetary mixer, evacuate, set the revolution speed to 20-40rpm, set the high-speed dispersion speed to 800-1200rpm, and stir for 30-60 minutes; meanwhile, pass ice water to control the temperature of the reaction system to ≤30°C; S3. Add 2-10 parts of curing accelerator to the planetary mixer, evacuate, set the revolution speed to 20-40rpm, set the high-speed dispersion speed to 1000-1400rpm, and stir for 30-60 minutes; meanwhile, pass ice water to control the temperature of the reaction system to ≤30°C; after the stirring is completed, discharging and packaging to obtain epoxy adhesive.

[0030] As an example, the amount of the coupling agent in step S1 is 0.1, 0.2, 0.3, 0.5, 0.6, 0.8, 1.5, 2, 2.5, 3, 4 or 5, but is not limited thereto.

[0031] As an example, the amount of the stabilizer in step S1 is 0.1 parts, 0.4 parts, 0.7 parts, 0.9 parts, 1 parts, 1.2 parts, 1.3 parts, 1.8 parts, 2 parts, 3.5 parts, 4.5 parts or 5 parts, but is not limited thereto.

[0032] As an example, the revolution speed of the planetary mixer in step S1 is 20 rpm, 25 rpm, 30 rpm, 35 rpm or 40 rpm, but is not limited thereto.

[0033] As an example, the high-speed dispersion speed of the planetary mixer in step S1 is 800 rpm, 900 rpm, 1000 rpm or 1200 rpm, but is not limited thereto.

[0034] As an example, the mixing time of the planetary mixer in step S1 is 30 minutes, 40 minutes, 50 minutes or 60 minutes, but is not limited thereto.

[0035] As an example, the number of parts of liquid epoxy resin A in every 100 parts of mixed epoxy resin in step S1 is 10 parts, 12 parts, 13 parts, 15 parts, 16 parts, 20 parts, 23 parts, 25 parts, 28 parts or 30 parts, but is not limited thereto.

[0036] As an example, the number of parts of solid epoxy resin B in every 100 parts of mixed epoxy resin in step S1 is 10 parts, 14 parts, 15 parts, 17 parts, 19 parts, 20 parts, 22 parts, 25 parts, 26 parts or 30 parts, but is not limited thereto.

[0037] As an example, the number of parts of the diluent C in every 100 parts of the mixed epoxy resin in step S1 is 10 parts, 12 parts, 15 parts, 18 parts, 20 parts, 24 parts, 25 parts, 27 parts or 30 parts, but is not limited thereto.

[0038] As an example, the amount of modified epoxy resin D in every 100 parts of mixed epoxy resin in step S1 is 30 parts, 32 parts, 35 parts, 38 parts, 40 parts, 43 parts, 45 parts, 50 parts, 52 parts, 55 parts or 60 parts, but is not limited thereto.

[0039] As an example, the number of parts of the curing agent in step S2 is 40 parts, 48 ​​parts, 50 parts, 53 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts, 80 parts, 85 parts, 90 parts or 100 parts, but is not limited thereto.

[0040] As an example, the revolution speed of the planetary mixer in step S2 is 20 rpm, 25 rpm, 30 rpm, 35 rpm or 40 rpm, but is not limited thereto.

[0041] As an example, the high-speed dispersion speed of the planetary mixer in step S2 is 800 rpm, 900 rpm, 1000 rpm or 1200 rpm, but is not limited thereto.

[0042] As an example, the mixing time of the planetary mixer in step S2 is 30 minutes, 40 minutes, 50 minutes or 60 minutes, but is not limited thereto.

[0043] As an example, the amount of the curing accelerator in step S3 is 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts or 10 parts, but is not limited thereto.

[0044] As an example, the revolution speed of the planetary mixer in step S3 is 20 rpm, 25 rpm, 30 rpm, 35 rpm or 40 rpm, but is not limited thereto.

[0045] As an example, the high-speed dispersion speed of the planetary mixer in step S3 is 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm or 1400 rpm, but is not limited thereto.

[0046] As an example, the mixing time of the planetary mixer in step S3 is 30 minutes, 40 minutes, 50 minutes or 60 minutes, but is not limited thereto.

[0047] In a preferred embodiment, the liquid epoxy resin A includes at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin.

[0048] In a further preferred embodiment, the bisphenol A epoxy resin is selected from epoxy resins of models 828US, 828EL, JER828EL, 825, and EPIKOTE 828EL produced by Mitsubishi Chemical Corporation.

[0049] In a further preferred embodiment, the bisphenol F epoxy resin is selected from epoxy resins of model JER807 and 1750 produced by Mitsubishi Chemical Corporation or epoxy resins of model EXA-830LVP produced by DIC Corporation of Japan.

[0050] In a further preferred embodiment, the glycidylamine epoxy resin is selected from epoxy resins of models EP-3950L and EP-3980S produced by ADEKA Corporation of Japan.

[0051] In a further preferred embodiment, the glycidyl ester epoxy resin is an epoxy resin of model EX-721 produced by Nagase Chemicals Co., Ltd. of Japan. In a preferred embodiment, the solid epoxy resin B is selected from any one or a combination of epoxy resins with types DER671, DER662E, DER663U, and DER664U.

[0052] In a preferred embodiment, the diluent C is at least one of trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, dibromoneopentyl glycol diglycidyl ether, castor oil triglycidyl ether, and pentaerythritol tetraglycidyl ether.

[0053] In a preferred embodiment, the preparation method of the modified epoxy resin D comprises the following steps: P1. Add diisocyanate and polyol polymer into a reaction vessel at a molar ratio of (-N=C=O):(-OH) of (2.06-2.12):1, then add catalyst E accounting for 0.05%-0.2% of the total mass of diisocyanate and polyol polymer, and react for 1-3 hours at a temperature of 10°C-30°C under an inert gas (e.g., nitrogen) atmosphere to obtain a prepolymer F; P2. Under an inert gas (such as nitrogen) atmosphere, add glycidol into a reaction container; the amount of glycidol is added according to the molar ratio of -OH in glycidol to -N=C=O in prepolymer F of (1.01-1.03):1; heat to 50°C-80°C and react for 2-4 hours to obtain modified epoxy resin D.

[0054] As an example, the molar ratio of -N=C=O in the diisocyanate to -OH in the polyol polymer in step P1 is 2.06:1, 2.07:1, 2.09:1, 2.1:1, 2.12:1, but is not limited thereto.

[0055] As an example, in step P1, the percentage of catalyst E to the total mass of diisocyanate and polyol polymer is 0.05%, 0.1%, 0.15% or 0.2%, but it is not limited thereto.

[0056] As an example, the reaction temperature in step P1 is 10°C, 12°C, 14°C, 15°C, 20°C, 22°C, 25°C or 30°C, but is not limited thereto.

[0057] As an example, the reaction time in step P1 is 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours, but is not limited thereto.

[0058] As an example, the molar ratio of -N=C=O in the prepolymer F to -OH in glycidol in step P2 is 1.01:1, 1.02:1, 1.03:1, but is not limited thereto.

[0059] As an example, the reaction temperature in step P2 is 50°C, 53°C, 54°C, 55°C, 60°C, 65°C, 70°C or 80°C, but is not limited thereto.

[0060] As an example, the reaction time in step P2 is 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours, but is not limited thereto.

[0061] In a further preferred embodiment, the diisocyanate in step P1 is selected from any one or a combination of MDI (diphenylmethane diisocyanate), PAPI (polymethylene polyphenyl polyisocyanate), TDI (toluene diisocyanate), XDI (meta-xylylenediisocyanate), HDI (hexamethylene diisocyanate), HMDI (dicyclohexylmethane diisocyanate), and IPDI (isophorone diisocyanate).

[0062] In a further preferred embodiment, the polyol polymer in step P1 is selected from at least one of polyether polyol, bio-based polyol and polyester polyol.

[0063] In a further preferred embodiment, the polyether polyol is selected from at least one of PEG (polyethylene glycol), PPG (polypropylene glycol), and PTMG (polytetramethylene glycol); for example, PEG-2000, PEG-3000, PPG-400, PPG-800, PPG-2000, PPG-3000, PTMG-850, PTMG-1000, and PTMG-2000.

[0064] In a further preferred embodiment, the bio-based polyol is BASF Sovermol ® At least one of the series products. For example, the bio-based polyol is selected from Sovermole 750 and Sovermole 805.

[0065] In a further preferred embodiment, the polyester polyol is selected from Priplast 3162, Priplast 3172, Priplast 3192 of Croda Chemicals (Shanghai) Co., Ltd., or / and XCPA-110, XCPA-195 selected from Asahikawa Chemical (Suzhou) Co., Ltd., or / and Capa 3050, Capa 3031 selected from Perstorp UK Ltd.

[0066] In a further preferred embodiment, the catalyst E in step P1 is dibutyltin dilaurate.

[0067] The coupling agent used in this application is a type of compound that can improve the dispersion of fillers in adhesives, and can also improve the wetting and bonding of the interface between the adhesive and the adherend. In a preferred embodiment, the coupling agent in step S1 is a silicon-based coupling agent or / and a titanate coupling agent. In a further preferred embodiment, the silicon-based coupling agent is at least one of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane (KH-560), 3-glycidylpropylmethyldiethoxysilane, 3-glycidylpropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane; or / and, the titanate coupling agent is selected from the model PlenactTTS, Plenact 46B or other similar products of Ajinomoto Co., Ltd. of Japan.

[0068] The stabilizer used in the present application is a material that can reduce the reactivity of the single-component epoxy adhesive and improve the storage stability at room temperature or below, but at the same time does not affect or has little effect on the curing speed during high temperature curing. In a preferred embodiment, the stabilizer in step S1 is an organic acid. In a further preferred embodiment, the stabilizer is at least one of fumaric acid, barbituric acid, salicylic acid, and citric acid.

[0069] The curing agent used in the present application is a class of compounds rich in active hydrogen, which does not react with epoxy resin at room temperature or below, but can react quickly with epoxy groups under the catalysis of a curing accelerator when the temperature is increased. The curing agent is characterized in that it contains at least one mercapto group (-SH) in the molecular structure. In a preferred embodiment, the curing agent in step S2 is at least one of trimethylolpropane tris (3-mercaptopropionate), pentaerythritol tetra-3-mercaptopropionate, pentaerythritol tetrathioacetate, and tetrakis (3-mercaptobutyric acid) pentaerythritol ester. In a further preferred embodiment, the curing agent in step S2 is tetrakis (3-mercaptobutyric acid) pentaerythritol ester.

[0070] The curing accelerator used in the present application is a compound that is stable at room temperature and can catalyze the ring-opening reaction between the thiol group in the curing agent and the epoxy group in the epoxy resin when heated to 60-80°C. In a preferred embodiment, the curing accelerator in step S3 includes a combination of one or more of hydrazides, modified imidazoles, amine derivatives, and microcapsule curing agents. For example, the curing accelerator is at least one of the FXR series products (such as FXR1020, FXR1081) of Fuji Chemical Co., Ltd. of Japan, the PN series products (such as PN-23, PN-23J, PN-40, PN-50) of Ajinomoto Co., Ltd. of Japan, the MY series products (such as MY-24, MY-25, MY-H) of Ajinomoto Co., Ltd. of Japan, and the EH-50 series products (such as EH-5011S, EH-5046S) of EDICO Co., Ltd. of Japan.

[0071] Example 1 A method for preparing an epoxy adhesive comprises the following steps: S1. In terms of mass fractions, 100 parts of mixed epoxy resin (30 parts of EXA-830LVP, 20 parts of DER671, 20 parts of trimethylolpropane triglycidyl ether and 30 parts of modified epoxy resin D), 1.5 parts of KH-560 and 0.8 parts of salicylic acid are added to a planetary mixer with cooling function and high-speed dispersing function, and vacuumed (for example, the vacuum degree is -96KPa), the revolution speed is 30rpm, the high-speed dispersing speed is 800rpm, and stirred for 30 minutes. The preparation method of modified epoxy resin D comprises the following steps: P1. Add IPDI and PPG-400 into a reaction vessel at a molar ratio of (-N=C=O):(-OH) of 2.1:1, then add dibutyltin dilaurate accounting for 0.12% of the total mass of IPDI and PPG-400, introduce nitrogen, control the temperature of the reaction system to 20° C. and react for 3 hours to obtain prepolymer F; P2. Under a nitrogen atmosphere, glycidol was added to a reaction vessel; the amount of glycidol was added in a ratio of 1.02:1 between the molar ratio of -OH in glycidol and -N=C=O in prepolymer F; the temperature was raised to 70°C and the reaction was carried out for 4 hours to obtain a modified epoxy resin D (denoted as D1).

[0072] S2, add 74 parts of Karenz MT PE1 (pentaerythritol tetrakis(3-mercaptobutyrate) ester) into the planetary mixer, evacuate (for example, the vacuum degree is -96 KPa), rotate at 30 rpm, and at a high-speed dispersion speed of 800 rpm, and stir for 60 minutes; meanwhile, pass ice water to control the temperature of the reaction system to ≤30°C (for example, 10°C); S3. Add 7.7 parts of FXR1020 to the planetary mixer, evacuate (for example, the vacuum degree is -96 KPa), set the revolution speed to 30 rpm, set the high-speed dispersion speed to 1200 rpm, and stir for 60 minutes; meanwhile, pass ice water to control the temperature of the reaction system to ≤30°C (for example, 10°C); after the stirring is completed, discharge and package to obtain the epoxy adhesive.

[0073] Example 2 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Embodiment 1, except that in step S1, the number of parts of EXA-830LVP is 20 parts, the number of parts of the modified epoxy resin D (D1) is 40 parts; and the number of parts of Karenz MT PE1 in step S2 is 69 parts.

[0074] Example 3 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Embodiment 1, except that in step S1, the number of EXA-830LVP is 20 parts, the number of DER671 is 10 parts, and the number of modified epoxy resin D (D1) is 50 parts; and the number of Karenz MT PE1 in step S2 is 70 parts.

[0075] Example 4 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Embodiment 1, except that PPG-400 in step P1 is replaced by PPG-800, the obtained modified epoxy resin D is recorded as D2, the modified epoxy resin D in step S1 is D2; and the number of parts of Karenz MT PE1 in step S2 is 70 parts.

[0076] Example 5 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Embodiment 4, except that in step S1, the number of parts of EXA-830LVP is 20 parts, the number of parts of the modified epoxy resin D (D2) is 40 parts; and the number of parts of Karenz MT PE1 in step S2 is 64 parts.

[0077] Example 6 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Embodiment 4, except that in step S1, the number of EXA-830LVP is 20 parts; the number of DER671 is 10 parts; the modified epoxy resin D is D2, the number of which is 50 parts; and the number of Karenz MT PE1 in step S2 is 65 parts.

[0078] Example 7 The method for preparing the epoxy adhesive in this embodiment is basically the same as that in Example 1, except that in step S1, the diluent C is pentaerythritol tetraglycidyl ether, the number of parts is 20 parts; the curing agent is trimethylolpropane tris (3-mercaptopropionate), the number of parts is 68 parts; the curing accelerator is PN-23J, the number of parts is 7.5 parts. The revolution speed of the planetary mixer in steps S1 and S2 is 40rpm, the high-speed dispersion speed is 1200rpm, and the stirring time is 60 minutes. The revolution speed of the planetary mixer in step S3 is 40rpm, the high-speed dispersion speed is 1400rpm, and the stirring time is 60 minutes.

[0079] Example 8 The method for preparing the epoxy adhesive in this embodiment is substantially the same as that in Example 7, except that the modified epoxy resin D in step S1 is D2, and the number of parts is 30. The revolution speed of the planetary mixer in steps S1 and S2 is 20 rpm, the high-speed dispersion speed is 800 rpm, and the stirring time is 30 minutes. The revolution speed of the planetary mixer in step S3 is 20 rpm, the high-speed dispersion speed is 1000 rpm, and the stirring time is 30 minutes.

[0080] Comparative Example 1 A method for preparing an epoxy adhesive comprises the following steps: R1. In terms of mass fractions, 100 parts of mixed epoxy resin (20 parts of EXA-830LVP, 20 parts of DER671, 20 parts of trimethylolpropane triglycidyl ether and 40 parts of modified epoxy resin G), 1.5 parts of KH-560 and 0.8 parts of salicylic acid are added to a planetary mixer with cooling function and high-speed dispersing function, evacuated (for example, the vacuum degree is -96KPa), the revolution speed is 40rpm, the high-speed dispersing speed is 800rpm, and stirred for 30 minutes. The preparation method of modified epoxy resin G includes the following steps: under a nitrogen atmosphere, epoxy resin E51 and prepolymer F prepared in step P1 of Example 1 are added to a reaction vessel at a mass ratio of 100:25, heated to 70°C for reaction for 4 hours, and side chain modified modified epoxy resin G is obtained.

[0081] R2, add 76 parts of Karenz MT PE1 (pentaerythritol tetrakis(3-mercaptobutyrate) ester) into the planetary mixer, evacuate (for example, the vacuum degree is -96 KPa), rotate at 30 rpm, and at a high-speed dispersion speed of 800 rpm, and stir for 60 minutes; meanwhile, pass ice water to control the temperature of the reaction system to ≤30°C (for example, 10°C); R3. Add 7.7 parts of FXR1020 to the planetary mixer, evacuate (for example, the vacuum degree is -96 KPa), set the revolution speed to 30 rpm, set the high-speed dispersion speed to 1200 rpm, and stir for 60 minutes; at the same time, pass ice water to control the temperature of the reaction system to ≤30°C (for example, 10°C); after the stirring is completed, discharge and package to obtain the epoxy adhesive.

[0082] Comparative Example 2 The method for preparing the epoxy adhesive in this comparative example is basically the same as that in comparative example 1, except that in step R1, the number of EXA-830LVP is 10 parts, the number of DER671 is 10 parts, and the number of modified epoxy resin G is 60 parts.

[0083] Performance determination of epoxy adhesives The raw material compositions of the epoxy adhesives in Examples 1 to 8 and Comparative Examples 1 to 2 are summarized in Table 1.

[0084] Table 1 Raw material composition of epoxy adhesive in Examples 1 to 8 and Comparative Examples 1 to 2

[0085] The properties of the epoxy adhesives prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were tested. The test results are shown in Table 2. The test methods are as follows.

[0086] (1) Tensile shear strength: Stainless steel / PC lap joints were prepared by heat curing at 70°C for 30 min and tested using a universal electronic tensile testing machine (Shimadzu AG-IC20KN) at a tensile rate of 10 mm / min. The average value of 10 groups of samples was taken.

[0087] (2) Tensile strength and elongation at break: Prepare samples in accordance with the requirements of GB / T 1040.2-2006 “Determination of tensile properties of plastics Part 2: Test conditions for molded and extruded plastics”. Heat cure at 70°C for 30 min. Test with a universal electronic tensile testing machine (Shimadzu AG-IC20KN) at a tensile rate of 50 mm / min. Take the average value of 10 groups of samples.

[0088] (3) Storage modulus: tested using DMA850 from TA Instruments, USA. The test mode is tensile mode. The specimen length is 20 mm, the width is 5 mm, and the thickness is 0.5 mm. It is prepared by heat curing at 70°C for 30 min. Test parameters: temperature range is 0-80°C, the corresponding value of 25°C is taken, the frequency is 1 Hz, and the scanning is 5°C / min.

[0089] (4) Double 85 test: Stainless steel / PC overlap was prepared by heat curing at 70°C for 30 min. After being placed in a double 85 test chamber (Shenzhen Hongjijia Technology XHD-800L) for 500 h, it was tested using a universal electronic tensile testing machine (Shimadzu AG-IC20KN) at a tensile rate of 10 mm / min. The average value of 10 groups of samples was taken.

[0090] Table 2 Performance test results of epoxy adhesives in Examples 1 to 8 and Comparative Examples 1 to 2

[0091] It can be seen from the experimental data in Table 2 that in this application, by reasonably matching the homemade main chain modified epoxy resin with liquid epoxy resin, solid epoxy resin and diluent, an epoxy adhesive with high modulus (>1300MPa), high elongation at break (>110%) and high strength and toughness is prepared. At the same time, the high modulus and high elongation at break epoxy adhesive also has a high initial shear strength (>22MPa) and good resistance to moisture and heat. In contrast, the side chain modified epoxy resin is used in Comparative Examples 1 to 2. Although the obtained epoxy adhesive maintains a high modulus, the elongation at break is significantly reduced, the shear strength is slightly reduced, and the resistance to moisture and heat is poor. This is because the modified epoxy resin D (such as D1 and D2) used in the examples is toughened by introducing a main chain polyurethane structure into the epoxy resin network, which can appropriately reduce the crosslinking degree of the epoxy resin network, increase the content of polyurethane, improve the toughness and elasticity of the cured network structure, and have both high modulus and high elongation at break, thereby improving the adhesion to stainless steel and PC substrates. The modified epoxy resin G used in the comparative example is toughened by a side chain polyurethane structure, which is toughened and crosslinked by the side chain of the epoxy resin network. The main network has a high degree of crosslinking, resulting in insufficient toughness. Although the modulus is high, the elongation at break is low. It can also be seen from Table 2 that, compared with the epoxy adhesives prepared in Examples 1 to 3, Examples 4 to 6 increase the molecular weight of the modified epoxy resin D (the molecular weight of PPG increases from 400 to 800) and the proportion of the modified epoxy resin D in the mixed epoxy resin. Although the storage modulus decreases, the elongation at break increases significantly. This is because the polyurethane soft and hard block structure containing polyether components in the main chain of the modified epoxy resin D can effectively improve the toughness and elasticity of the cured network.

[0092] The above-described embodiments are only preferred embodiments of the present application and are not intended to limit the scope of protection of the present application. For any person skilled in the art, the present application may have various changes and modifications. Any simple equivalent changes and modifications made based on the scope of protection of the present application and the contents of the specification should be included in the scope of protection of the present application.

Claims

1. A low-temperature curing epoxy adhesive with high modulus and high elongation at break, characterized in that: The invention comprises the following components in parts by mass: 100 parts of mixed epoxy resin, 0.1-5 parts of coupling agent, 0.1-5 parts of stabilizer, 40-100 parts of curing agent and 2-10 parts of curing accelerator; wherein, every 100 parts of the mixed epoxy resin comprises 10-30 parts of liquid epoxy resin A, 10-30 parts of solid epoxy resin B, 10-30 parts of diluent C and 30-60 parts of modified epoxy resin D; the modified epoxy resin D is obtained by reacting diisocyanate and polyol polymer in the presence of a catalyst, and then reacting the reaction product with glycidol.

2. The epoxy adhesive according to claim 1, characterized in that The liquid epoxy resin A comprises at least one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin; or / and, the solid epoxy resin B is selected from any one or a combination of epoxy resins with models DER671, DER662E, DER663U, and DER664U; or / and, the diluent C is at least one of trimethylolpropane triglycidyl ether, trimethylolethane triglycidyl ether, dibromoneopentyl glycol diglycidyl ether, castor oil triglycidyl ether, and pentaerythritol tetraglycidyl ether.

3. The epoxy adhesive according to claim 1, characterized in that: The coupling agent is a silicon-based coupling agent or / and a titanate coupling agent; or / and, the stabilizer is an organic acid.

4. The epoxy adhesive according to claim 3, characterized in that: The silicon-based coupling agent is at least one of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, 3-glycidylpropylmethyldiethoxysilane, 3-glycidylpropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, and γ-mercaptopropyltrimethoxysilane; or / and, the titanate coupling agent is a product of Ajinomoto Co., Ltd., Japan, with model number Plenact TTS or / and Plenact 46B.

5. The epoxy adhesive according to claim 3, characterized in that: The stabilizer is at least one of fumaric acid, barbituric acid, salicylic acid and citric acid.

6. The epoxy adhesive according to claim 1, characterized in that: The curing agent is at least one of trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis-3-mercaptopropionate, pentaerythritol tetrakismercaptoacetate, and pentaerythritol tetrakis(3-mercaptobutyrate); or / and the curing accelerator is at least one of the FXR series products of Fuji Chemical Co., Ltd. of Japan, the PN series products of Ajinomoto Co., Ltd. of Japan, the MY series products of Ajinomoto Co., Ltd. of Japan, and the EH-50 series products of Aidico Co., Ltd. of Japan.

7. The epoxy adhesive according to claim 1, characterized in that: The preparation method of modified epoxy resin D comprises the following steps: P1. Add diisocyanate and polyol polymer into a reaction container at a molar ratio of (-N=C=O):(-OH) of (2.06-2.12):1, then add catalyst E accounting for 0.05%-0.2% of the total mass of diisocyanate and polyol polymer, and control the temperature of the reaction system to 10°C-30°C under an inert gas atmosphere for 1-3 hours to obtain a prepolymer F; P2. Under an inert gas atmosphere, add glycidol into a reaction container; the amount of glycidol is added according to the molar ratio of -OH in glycidol to -N=C=O in prepolymer F of (1.01~1.03):1; heat to 50°C~80°C and react for 2~4 hours to obtain modified epoxy resin D.

8. The epoxy adhesive according to claim 7, characterized in that: The diisocyanate is selected from any one or a combination of MDI, PAPI, TDI, XDI, HDI, HMDI, and IPDI; or / and, the polyol polymer is selected from at least one of polyether polyols, bio-based polyols, and polyester polyols; or / and, the catalyst E is dibutyltin dilaurate.

9. The method for preparing the epoxy adhesive according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1, respectively adding the mixed epoxy resin, the coupling agent and the stabilizer into a planetary mixer with cooling function and high-speed dispersing function, evacuating to a vacuum degree of ≤-96Kpa, with an orbital speed of 20-40rpm, a high-speed dispersing speed of 800-1200rpm, and stirring for 30-60 minutes; S2, add the curing agent to the planetary mixer, evacuate to a vacuum degree of ≤-96Kpa, the revolution speed is 20-40rpm, the high-speed dispersion speed is 800-1200rpm, and stir for 30-60 minutes; at the same time, pass ice water to control the temperature of the reaction system to ≤30°C; S3, adding the curing accelerator to the planetary mixer, evacuating to a vacuum degree of ≤-96Kpa, the revolution speed is 20-40rpm, the high-speed dispersion speed is 1000-1400rpm, and stirring for 30-60 minutes; at the same time, passing ice water to control the temperature of the reaction system to ≤30°C; after the stirring is completed, discharging and packaging to obtain an epoxy adhesive.

10. Use of the epoxy adhesive according to any one of claims 1 to 8 in electronic modules.

Images