Toughening type single-component epoxy adhesive and preparation method thereof

Abstract

The invention discloses a toughened single-component epoxy adhesive and a preparation method thereof, and belongs to the technical field of epoxy adhesives. The invention relates to a toughening type single-component epoxy adhesive and a preparation method thereof. The flexible epoxy resin composition comprises the following raw material components in parts by mass: 18-20 parts of an epoxy resin base material, 21-23 parts of flexible epoxy resin, 24-26 parts of elastomer modified epoxy resin, 14-16 parts of shell-core structure rubber, 1-3 parts of a thixotropic agent, 5-7 parts of a first curing agent, 3-4 parts of a second curing agent, 3-4 parts of an accelerant, 0.3-0.5 part of a coupling agent and 5-8 parts of a heat stabilizer. Wherein the first curing agent comprises a melamine curing agent; the second curing agent is obtained by sequentially reacting 5 ', 5-diallyl-2, 2'-biphenol with phenylphosphonic dichloride and then reacting with mercaptoethylamine; the heat stabilizer is obtained by reacting fullerene with unsaturated alcohol; the material prepared by the invention has better mechanical properties and high temperature resistance.

Description

Technical Field

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

[0002] Epoxy resin adhesives, as an important polymer material, have been widely used in aerospace, automotive manufacturing, electronics, building materials, and new energy fields due to their unique performance advantages. Their core advantage lies in the ability to highly customize and control the microstructure and macroscopic properties of the cured epoxy resin network through careful selection of the epoxy resin matrix, functional modifiers, and efficient curing agents, thereby endowing it with a series of excellent comprehensive properties. These include: outstanding chemical resistance; excellent mechanical properties, such as high tensile strength, compressive strength, and fatigue strength; low volume shrinkage during curing, which helps reduce internal stress and improve bonding reliability; and excellent electrical insulation properties and long-term resistance to environmental aging.

[0003] Based on the above characteristics, epoxy resin adhesives have been developed into an important type of structural adhesive. They can not only achieve strong bonding between different materials, but also partially replace or enhance traditional mechanical connection methods (such as welding, bolts, screws or riveting), thereby simplifying assembly processes, reducing structural weight, improving stress distribution and enhancing the overall durability of the structure.

[0004] However, with the continuous advancement of modern industrial technology, more stringent requirements have been placed on the service environment of structural adhesives. For example, in the aerospace and rail transportation fields, materials need to maintain stable mechanical properties over a wide temperature range; in the fields of electronic packaging and new energy, adhesives are required to possess both good flame retardancy and thermal stability to ensure safe use. Although traditional single-component epoxy adhesives have advantages such as ease of use and stable storage, they still face many challenges in practical applications: their intrinsic brittleness is relatively high, and their impact resistance and fracture toughness are insufficient, making them prone to cracking in stress concentration areas and leading to bond failure; their heat resistance is limited, and they are prone to thermal degradation or modulus reduction at high temperatures, affecting long-term service reliability; at the same time, most epoxy systems lack effective flame retardant functions, posing a risk of combustion in open flame or high-temperature environments, limiting their application in situations with high fire safety requirements.

[0005] Therefore, there is an urgent need to develop a toughened one-component epoxy adhesive that combines high toughness, good flame retardancy, and excellent heat resistance. Summary of the Invention

[0006] The purpose of this invention is to provide a toughened one-component epoxy adhesive and its preparation method to solve the technical problems mentioned in the background art.

[0007] The technical solution to achieve the objective of this invention is: In a first aspect, the present invention provides a toughened one-component epoxy adhesive, wherein, by weight, the raw material components include 18-20 parts by weight of epoxy resin base, 21-23 parts by weight of flexible epoxy resin, 24-26 parts by weight of elastomer-modified epoxy resin, 14-16 parts by weight of core-shell structured rubber, 1-3 parts by weight of thixotropic agent, 5-7 parts by weight of first curing agent, 3-4 parts by weight of second curing agent, 3-4 parts by weight of accelerator, 0.3-0.5 parts by weight of coupling agent, and 5-8 parts by weight of heat stabilizer.

[0008] The epoxy resin base material includes any one or at least a combination of two of the following: liquid bisphenol A epoxy resin DER331 from Dow; liquid bisphenol A epoxy resin DER332 from Dow; liquid bisphenol A epoxy resin DER383 from Dow; liquid bisphenol A epoxy resin JER828 from Mitsubishi Chemical; liquid bisphenol A epoxy resin Epotec YD 128 from Aditya Birla Chemicals; liquid bisphenol F epoxy resin DER 354 from Dow; liquid bisphenol A / F mixed epoxy resin DER 353 from Dow; aliphatic epoxy resin DER 736 from Dow; polypropylene glycol diglycidyl ether DER 732 from Dow; solid bisphenol A epoxy resin DER 661 from Dow; phenolic epoxy resin DEN 438 from Dow; and brominated epoxy resin DER 542 from Dow.

[0009] The flexible epoxy resins include any one or at least a combination of DER 732 from Dow Chemical; Epo-Tek 310A from Epoxy Technology; XB-4122, PY-322 and PY-4122US from Ciba-Geigy; WC-68 from Wilmington Chemical; Anthiol R-12 from Pacific Anchor; NC-514 and NC-514S from Cardiolite; EP-49-10N from ADEKA; EP-49-20 from ADEKA; EP-49-23 from ADEKA; and EP-49-25 from ADEKA.

[0010] The elastomer-modified epoxy resins include any one or at least two combinations of Hypox DA 323 from CVC Thermosets; EPON 58005 and EPON 58034 from Miller-Stephenson; JER871 and JER872 from Mitsubishi Chemical; B-Tough A1, A2 and A3 from Croda; YD-171 and YD-172 from Nippon Steel Chemical Co., Ltd.; EPU-6, EPU-7N, EPU-11F, EPU-15F, EPU-1395, EPU-738, EPU-17, EPU-17T-6 and EPU-80 from ADEKA; KanAce MX154; and Acryset BPA328.

[0011] The core-shell structured rubber particles include: Zefiac series from Aica Kogyo; Paraaloid EXL2650A, EXL 2655 and EXL2691 A from The Dow Chemical Company; Kane Ace® MX series including MX 120, MX 125, MX 130, MX 136, MX 551, MX553 from Kaneka Corporation; and METABLEN SX-006 from Mitsubishi Rayon.

[0012] The promoters include isophorone bis(dimethylurea) Omicure U35 from Huntsman; 4,4′-methylene bis(phenyldimethylurea) Omicure U52 from Huntsman; and phenyldimethylurea Omicure U405 from Huntsman.

[0013] Furthermore, the first curing agent includes a dicyandiamide curing agent.

[0014] Furthermore, the second curing agent is obtained by reacting 5',5-diallyl-2,2'-biphenyldiphenol with phenylphosphonic dichloride and then with mercaptoethylamine.

[0015] Furthermore, the heat stabilizer is obtained by reacting fullerene with an unsaturated alcohol.

[0016] In a second aspect, the present invention provides a method for preparing a toughened one-component epoxy adhesive as described in the first aspect, comprising the following preparation steps: (1) Weigh and prepare each raw material component; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 100-200 parts by weight of dimethyl sulfoxide and 0.01-0.03 parts by weight of catalyst H-MCM-22 are stirred and mixed for 60-80 min, and then reacted at atmospheric pressure and 200-210℃ for 5-10 h. The dimethyl sulfoxide is removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 50-70 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 50-70 min, then degas under vacuum to obtain toughened single-component epoxy adhesive.

[0017] Furthermore, the preparation method of the second curing agent is as follows: Under nitrogen protection, 10-11 parts by weight of triethylamine, 13-14 parts by weight of 5',5-diallyl-2,2'-biphenylhydroquinone, and 100-110 parts by weight of toluene are stirred and mixed evenly. 9.5-10.5 parts by weight of phenylphosphonic dichloride are added dropwise at room temperature, and the addition is completed within 10 minutes. The mixture is then heated to 60-70°C and kept at this temperature for 11-13 hours. The mixture is then washed with deionized water until clear and non-turbid. Next, toluene is removed by distillation, and the mixture is allowed to stand overnight. The obtained crystals were removed and dried to obtain an intermediate. Under nitrogen protection, 90-110 parts by mass of tetrahydrofuran were added to the intermediate and stirred for 20-40 minutes. Then, 3.8-4.2 parts by mass of mercaptoethylamine were added and stirred for another 25-35 minutes. Finally, 0.48-0.54 parts by mass of photoinitiator were added, and the mixture was reacted at room temperature under ultraviolet light for 50-70 minutes. The tetrahydrofuran was then removed by rotary evaporation. The mixture was washed 2-4 times with acetone and deionized water, and then dried to obtain the second curing agent.

[0018] Furthermore, the photoinitiator is benzoin dimethyl ether.

[0019] Furthermore, the ultraviolet light wavelength is 320~420nm.

[0020] Furthermore, the heat stabilizer is prepared as follows: 5.8-7 parts by weight of unsaturated alcohol, 2-3 parts by weight of C60, 100-200 parts by weight of chloroform, and 0.34-0.48 parts by weight of aluminum trichloride are stirred and mixed for 50-70 minutes, then heated to 60-70°C and stirred for 23-25 ​​hours, then allowed to stand and separate, the chloroform is washed away with anhydrous ethanol, and dried to obtain the heat stabilizer.

[0021] Furthermore, the unsaturated alcohol includes allyl alcohol.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects: (1) The toughened single-component epoxy adhesive of the present invention comprises epoxy resin base, flexible epoxy resin, elastomer-modified epoxy resin, core-shell structure rubber, thixotropic agent, first curing agent, second curing agent, accelerator, coupling agent, and heat stabilizer. The introduction of flexible epoxy resin increases the flexibility of molecular chain segments, reduces internal stress, and improves elongation at break. The elastomer-modified epoxy resin and core-shell structure rubber, as highly efficient toughening components, form micron or nano-sized elastic particles through in-situ phase separation during the curing process. These dispersed phases... The particles can effectively induce crazes and hinder crack propagation, and absorb a large amount of fracture energy through plastic deformation, thereby significantly improving the toughness of the adhesive; the coupling agent enhances the interfacial bonding between the filler and the matrix, improving the integrity and durability of the overall structure; the thixotropic agent imparts good rheological properties to the adhesive, preventing flow and settling during construction; the heat stabilizer maintains the performance stability of the adhesive under long-term high-temperature environments; the synergistic effect of the components enables the prepared single-component epoxy adhesive to maintain good processability while possessing excellent toughness and thermal stability.

[0023] (2) The second curing agent of the present invention is prepared by the following reaction pathway: First, the phenolic hydroxyl group in 5',5-diallyl-2,2'-biphenyl reacts with the chlorine atom in phenylphosphonic dichloride to generate a flame-retardant intermediate containing a phosphate ester structure; subsequently, the unsaturated olefin double bond in the intermediate molecule reacts with the mercapto group in mercaptoethylamine under initiation conditions to undergo a highly efficient thiol-olefin click reaction, introducing a terminal primary amino group, and finally obtaining a multifunctional curing agent with both flame retardancy and reactivity; the second curing agent reacts with the epoxy group in the epoxy resin through the amino group at the end of the molecule. A ring-opening reaction is generated to achieve chemical grafting and curing with the epoxy matrix. At the same time, liquid crystal units with rigid biphenyl structures are successfully introduced into the cross-linking network. The biphenyl liquid crystal structure has high bond energy and molecular orientation order, which can effectively enhance the rigidity and thermal stability of the cross-linking network and compensate for the decrease in heat resistance caused by the introduction of rubber elastomers. The phosphate ester groups introduced into the molecule can play a condensed phase flame retardant role at high temperatures, further improving the thermal decomposition temperature and flame retardant performance of the material. The introduction of the second curing agent effectively improves the toughness while significantly improving the heat resistance and flame retardancy of the adhesive.

[0024] (3) The heat stabilizer of the present invention is obtained by reacting fullerene with unsaturated alcohol; by utilizing the carbon-carbon double bond in the unsaturated alcohol molecule to undergo a Diels-Alder (DA) addition reaction with fullerene C60, the surface chemical modification of C60 is achieved; not only are polar groups introduced on the surface of fullerene, enhancing its compatibility with epoxy groups, but also the aggregation tendency of C60 in the adhesive system is effectively suppressed, significantly improving its dispersibility and stability in the resin matrix; the uniformly dispersed C60 nanoparticles can play multiple roles in the material: on the one hand, its highly conjugated spherical structure has excellent self-sustaining properties. The free radical scavenging ability effectively terminates the free radical chain degradation reaction of polymer chains under thermo-oxidative conditions, thus slowing down the aging process of materials. On the other hand, C60 can promote the formation of a char layer when heated. This char layer has a good thermal barrier effect, which can effectively block the transfer of heat and oxygen, further improving the thermal stability and flame retardant properties of the material. Using unsaturated alcohol-modified fullerene C60 as a heat stabilizer not only improves its dispersion behavior in the system, but also fully leverages its synergistic effects in anti-oxidation, heat degradation resistance and flame retardancy, significantly improving the long-term service stability of single-component epoxy adhesives under high-temperature environments.

[0025] (4) In the preparation process of the toughened single-component epoxy adhesive of the present invention, the heat stabilizer and the second curing agent are first premixed and reacted. The alcohol introduced after the heat stabilizer is modified with unsaturated alcohol undergoes an alkylation reaction with the benzene ring in the second curing agent molecule to carry out chemical grafting, which causes multiple second curing agent molecules to be covalently linked to the fullerene core of the heat stabilizer, forming a hyperbranched structure with fullerene as the branching center and multiple arms extending. This not only further improves the dispersion stability of the second curing agent in the system, but also enhances its interfacial compatibility and crosslinking with the epoxy resin matrix. Density; During subsequent curing, these grafted second curing agents retain active amino groups, which can continue to react with epoxy groups, introducing functional units containing biphenyl structures and phosphate ester groups more uniformly into the crosslinking network. At the same time, the fullerene core acts as a thermally stable center, playing an antioxidant and flame-retardant role. Through the multiple crosslinking effects brought about by the hyperbranched network, the thermal stability of the material is significantly improved. Meanwhile, the multi-point toughening mechanism at the molecular scale optimizes the stress transmission process and enhances the energy dissipation capacity, thereby further improving the overall toughness and service stability of the single-component epoxy adhesive under high-temperature conditions. Detailed Implementation

[0026] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0027] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0028] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0029] UV chamber: 100W power, wavelength range 320~420nm. Example

[0030] A method for preparing a toughened one-component epoxy adhesive includes the following preparation steps: (1) Weigh and prepare each raw material component: 18-20 parts by weight of epoxy resin base, 21-23 parts by weight of flexible epoxy resin, 24-26 parts by weight of elastomer modified epoxy resin, 14-16 parts by weight of core-shell structure rubber, 1-3 parts by weight of thixotropic agent, 5-7 parts by weight of first curing agent, 3-4 parts by weight of second curing agent, 3-4 parts by weight of accelerator, 0.3-0.5 parts by weight of coupling agent, and 5-8 parts by weight of heat stabilizer; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 100-200 parts by weight of dimethyl sulfoxide and 0.01-0.03 parts by weight of catalyst H-MCM-22 are stirred and mixed for 60-80 min, and then reacted at atmospheric pressure and 200-210℃ for 5-10 h. The dimethyl sulfoxide is removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 50-70 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 50-70 min, then degas under vacuum to obtain toughened single-component epoxy adhesive.

[0031] The preparation method of the second curing agent is as follows: Under nitrogen protection, 10-11 parts by weight of triethylamine, 13-14 parts by weight of 5',5-diallyl-2,2'-biphenylhydroquinone, and 100-110 parts by weight of toluene are stirred and mixed evenly. 9.5-10.5 parts by weight of phenylphosphonic dichloride are added dropwise at room temperature, and the addition is completed within 10 minutes. The mixture is then heated to 60-70°C and kept at this temperature for 11-13 hours. The mixture is then washed with deionized water until clear and non-turbid. Toluene is then removed by distillation, and the mixture is allowed to stand overnight to collect the resulting crystals. The intermediate was dried to obtain an intermediate. Under nitrogen protection, 90-110 parts by weight of tetrahydrofuran were added to the intermediate and stirred for 20-40 minutes. Then, 3.8-4.2 parts by weight of mercaptoethylamine were added and stirred for another 25-35 minutes. Finally, 0.48-0.54 parts by weight of photoinitiator benzoin dimethyl ether were added. The mixture was then reacted at room temperature under ultraviolet light in an ultraviolet box for 50-70 minutes. The tetrahydrofuran was then removed by rotary evaporation. The mixture was washed 2-4 times with acetone and deionized water, and then dried to obtain the second curing agent.

[0032] The heat stabilizer is prepared as follows: 5.8-7 parts by weight of allyl alcohol, 2-3 parts by weight of C60, 100-200 parts by weight of chloroform, and 0.34-0.48 parts by weight of aluminum trichloride are stirred and mixed for 50-70 minutes, then heated to 60-70℃ and stirred for 23-25 ​​hours. After standing and separation, the chloroform is washed away with anhydrous ethanol and dried to obtain the heat stabilizer. Example 1

[0033] A method for preparing a toughened one-component epoxy adhesive includes the following preparation steps: (1) Weigh and prepare each raw material component; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 100 parts by weight of dimethyl sulfoxide and 0.01 parts by weight of catalyst H-MCM-22 were stirred and mixed for 60 min, and then reacted at atmospheric pressure and 200℃ for 5 h. The dimethyl sulfoxide was removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 50 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 50 min, and then degas under vacuum to obtain toughened single-component epoxy adhesive.

[0034] The preparation method of the second curing agent is as follows: Under nitrogen protection, 10 parts by mass of triethylamine, 13 parts by mass of 5',5-diallyl-2,2'-biphenylhydroquinone, and 100 parts by mass of toluene are stirred and mixed evenly. 9.5 parts by mass of phenylphosphonic dichloride are added dropwise at room temperature. After the addition is completed within 10 minutes, the mixture is heated to 60°C and kept at that temperature for 11 hours. Then, it is washed with deionized water until it is clear and non-turbid. Next, the toluene is removed by distillation, and the mixture is left to stand overnight. The resulting crystals are then removed and dried to obtain an intermediate. Under nitrogen protection, 90 parts by mass of tetrahydrofuran are added to the aforementioned intermediate and stirred for 20 minutes. Then, 3.8 parts by mass of mercaptoethylamine are added and stirred for another 25 minutes. Finally, 0.48 parts by mass of photoinitiator benzoin dimethyl ether are added. The mixture is then reacted at room temperature under ultraviolet light in an ultraviolet box for 50 minutes. The tetrahydrofuran is then removed by rotary evaporation. The mixture is washed twice with acetone and deionized water, and then dried to obtain the second curing agent.

[0035] The heat stabilizer is prepared as follows: 5.8 parts by mass of allyl alcohol, 2 parts by mass of C60, 100 parts by mass of chloroform, and 0.34 parts by mass of aluminum trichloride are stirred and mixed for 50 min, then heated to 60℃ and stirred for 23 h, then allowed to stand and separate, chloroform is washed away with anhydrous ethanol, and dried to obtain the heat stabilizer. Example 2

[0036] A method for preparing a toughened one-component epoxy adhesive includes the following preparation steps: (1) Weigh and prepare each raw material component; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 150 parts by weight of dimethyl sulfoxide and 0.02 parts by weight of catalyst H-MCM-22 were stirred and mixed for 70 min, and then reacted at atmospheric pressure and 205℃ for 8 h. The dimethyl sulfoxide was removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 60 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 60 min, and then degas under vacuum to obtain toughened single-component epoxy adhesive.

[0037] The preparation method of the second curing agent is as follows: Under nitrogen protection, 10.5 parts by mass of triethylamine, 13.3 parts by mass of 5',5-diallyl-2,2'-biphenylhydroquinone, and 105 parts by mass of toluene are stirred and mixed evenly. 10 parts by mass of phenylphosphonic dichloride are added dropwise at room temperature. After the addition is completed within 10 minutes, the mixture is heated to 65°C and kept at that temperature for 12 hours. Then, it is washed with deionized water until it is clear and non-turbid. Toluene is then removed by distillation and the mixture is left to stand overnight. The resulting crystals are then removed and dried to obtain an intermediate. Under nitrogen protection, 100 parts by mass of tetrahydrofuran are added to the aforementioned intermediate and stirred for 30 minutes. Then, 4 parts by mass of mercaptoethylamine are added and stirred for another 30 minutes. Finally, 0.51 parts by mass of photoinitiator benzoin dimethyl ether is added. The mixture is then reacted at room temperature under ultraviolet light in an ultraviolet box for 60 minutes. Tetrahydrofuran is then removed by rotary evaporation. The mixture is washed three times with acetone and deionized water, and then dried to obtain the second curing agent.

[0038] The heat stabilizer is prepared as follows: 6.4 parts by mass of allyl alcohol, 2.5 parts by mass of C60, 150 parts by mass of chloroform, and 0.41 parts by mass of aluminum trichloride are stirred and mixed for 60 min, then heated to 65℃ and stirred for 24 h, then allowed to stand and separate, chloroform is washed away with anhydrous ethanol, and dried to obtain the heat stabilizer. Example 3

[0039] A method for preparing a toughened one-component epoxy adhesive includes the following preparation steps: (1) Weigh and prepare each raw material component; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 200 parts by mass of dimethyl sulfoxide and 0.03 parts by mass of catalyst H-MCM-22 were stirred and mixed for 80 min, and then reacted for 10 h at atmospheric pressure and 210 °C. The dimethyl sulfoxide was removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 70 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 70 min, and then degas under vacuum to obtain toughened single-component epoxy adhesive.

[0040] The preparation method of the second curing agent is as follows: Under nitrogen protection, 11 parts by mass of triethylamine, 14 parts by mass of 5',5-diallyl-2,2'-biphenylhydroquinone, and 110 parts by mass of toluene are stirred and mixed evenly. 10.5 parts by mass of phenylphosphonic dichloride are added dropwise at room temperature. After the addition is completed within 10 minutes, the mixture is heated to 70°C and kept at that temperature for 13 hours. Then, it is washed with deionized water until it is clear and non-turbid. Toluene is then removed by distillation and the mixture is left to stand overnight. The resulting crystals are then removed and dried to obtain an intermediate. Under nitrogen protection, 110 parts by mass of tetrahydrofuran are added to the intermediate and stirred for 40 minutes. Then, 4.2 parts by mass of mercaptoethylamine are added and stirred for another 35 minutes. Then, 0.54 parts by mass of photoinitiator benzoin dimethyl ether is added. The mixture is then reacted at room temperature under ultraviolet light in an ultraviolet box for 70 minutes. Tetrahydrofuran is then removed by rotary evaporation. The mixture is washed four times with acetone and deionized water, and then dried to obtain the second curing agent.

[0041] The heat stabilizer is prepared as follows: 7 parts by mass of allyl alcohol, 3 parts by mass of C60, 200 parts by mass of chloroform, and 0.48 parts by mass of aluminum trichloride are stirred and mixed for 70 min, then heated to 70 °C and stirred for 25 h, then allowed to stand and separate, chloroform is washed away with anhydrous ethanol, and dried to obtain the heat stabilizer. Example 4

[0042] The difference between Example 4 and Example 2 lies in the raw material composition, as detailed in Table 1 below. The remaining steps are the same as in Example 2. Comparative Examples 1-3

[0043] The difference between Comparative Examples 1-3 and Example 2 lies in the raw material composition, as detailed in Table 1 below. The remaining steps are the same as in Example 2. Comparative Example 4

[0044] The difference between Comparative Example 4 and Example 2 is that the heat stabilizer used is fullerene C60, while the other steps are the same as in Example 2. Comparative Example 5

[0045] The difference between Comparative Example 5 and Example 2 lies in steps (2) and (3) as follows: (3) Flexible epoxy resin, elastomer-modified epoxy resin, core-shell structure rubber, thixotropic agent, coupling agent, and heat stabilizer are mixed and stirred under planetary stirring for 60 minutes. Then, while stirring, the first curing agent, the second curing agent, and the accelerator are added. Stirring is continued under planetary stirring for 60 minutes. Then, the mixture is degassed under vacuum to obtain a toughened single-component epoxy adhesive. The remaining steps are the same as in Example 2. Example of effect

[0046] Table 1 below shows the raw material composition of Examples 1-4 and Comparative Examples 1-5, and the performance test results of the toughened one-component epoxy adhesive after curing: Table 1 Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Bisphenol A epoxy resin NPEL 128 18 19 20 19 19 19 19 19 Liquid bisphenol F type epoxy resin DER354 19 KanAce MX154 24 25 26 25 25 25 25 25 Acryset BPA 328 25 Flexible epoxy resin NC 514S 19.5 20 20.5 20 20 20 20 20 20 Flexible epoxy resin EP-49-10N 1.5 2 2.5 2 2 2 2 2 2 γ-glycidyl etheroxypropyltrimethoxysilane Silquest A-187 0.3 0.4 0.5 0.4 0.4 0.4 0.4 0.4 0.4 Core-shell structured rubber particles Zefiac F351 14 15 16 15 15 15 15 15 15 Thixotropic agent Aerosil R202 1 2 3 2 2 2 2 2 2 Dicyandiamide (DDA) 5 CI 5 5 7 5 9 5 9 5 5 Second curing agent 3 4 4 4 4 4 4 Heat stabilizer 5 6 8 6 6 6 6 4,4′-Methylenebis(phenyldimethylurea) accelerator Omicure U52 3 3 4 3 3 3 3 3 3 Shear strength (MPa) GB / T7124 46.89 48.36 47.52 47.98 35.20 38.24 30.26 23.3 41.27 Extreme oxygen index (%) 32.6 33.4 32.9 32.2 27.0 30.8 25.9 28.2 33.1 Shear strength (MPa) at 150℃ 39.86 42.55 40.93 42.28 27.45 30.59 2.78 10.24 33.28 As shown in Table 1, the toughened one-component epoxy adhesives obtained in Examples 1-4 after curing exhibit good mechanical properties, flame retardant properties, and thermal stability.

[0047] The difference between Comparative Example 1 and Example 2 is that no second curing agent was used, no biphenyl liquid crystal was introduced, and a hyperbranched structure could not be formed. After curing, the mechanical properties of the toughened one-component epoxy adhesive decreased, the flame retardancy decreased, and the thermal stability decreased.

[0048] The difference between Comparative Example 2 and Example 2 is that no heat stabilizer was used, no fullerene C60 was introduced, and a hyperbranched structure could not be formed. After curing, the mechanical properties of the toughened one-component epoxy adhesive decreased, the flame retardancy decreased, and the thermal stability decreased.

[0049] The difference between Comparative Example 3 and Example 2 is that no second curing agent and heat stabilizer were used, no biphenyl liquid crystal and fullerene C60 were introduced and no hyperbranched structure could be formed, and the toughening effect of the introduced elastomer-modified epoxy resin and other components led to a decrease in thermal stability. After curing, the mechanical properties of the toughened one-component epoxy adhesive decreased, the flame retardancy decreased, and the thermal stability decreased.

[0050] The difference between Comparative Example 4 and Example 2 is that only fullerene is used as the heat stabilizer. Fullerene agglomerates and cannot form hyperbranched structures, resulting in decreased mechanical properties, reduced flame retardancy, and reduced thermal stability.

[0051] The difference between Comparative Example 5 and Example 2 is that the epoxy adhesive is prepared by directly mixing the raw material components, which cannot form a hyperbranched structure. After curing, the mechanical properties of the toughened single-component epoxy adhesive decrease and the thermal stability is reduced.

[0052] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A toughened one-component epoxy adhesive, characterized in that, By mass, the raw material components include 18-20 parts epoxy resin base, 21-23 parts flexible epoxy resin, 24-26 parts elastomer modified epoxy resin, 14-16 parts core-shell structure rubber, 1-3 parts thixotropic agent, 5-7 parts first curing agent, 3-4 parts second curing agent, 3-4 parts accelerator, 0.3-0.5 parts coupling agent, and 5-8 parts heat stabilizer.

2. The toughened one-component epoxy adhesive according to claim 1, characterized in that, The first curing agent includes a dicyandiamide curing agent.

3. The toughened one-component epoxy adhesive according to claim 1, characterized in that, The second curing agent is obtained by reacting 5',5-diallyl-2,2'-biphenyldiphenol with phenylphosphonic dichloride and then with mercaptoethylamine.

4. The toughened one-component epoxy adhesive according to claim 1, characterized in that, The heat stabilizer is obtained by reacting fullerene with unsaturated alcohol.

5. A method for preparing a toughened one-component epoxy adhesive as described in any one of claims 1 to 4, characterized in that, The preparation steps include the following: (1) Weigh and prepare each raw material component; (2) Under nitrogen protection, the second curing agent, heat stabilizer, 100-200 parts by weight of dimethyl sulfoxide and 0.01-0.03 parts by weight of catalyst H-MCM-22 are stirred and mixed for 60-80 min, and then reacted at atmospheric pressure and 200-210℃ for 5-10 h. The dimethyl sulfoxide is removed by vacuum distillation to obtain the premix. (3) Mix flexible epoxy resin, elastomer modified epoxy resin, core-shell structure rubber, thixotropic agent and coupling agent, stir under planetary stirring for 50-70 min, then add first curing agent, premix and accelerator while stirring, continue stirring under planetary stirring for 50-70 min, then degas under vacuum to obtain toughened single-component epoxy adhesive.

6. The method for preparing the toughened one-component epoxy adhesive according to claim 5, characterized in that, The preparation method of the second curing agent is as follows: Under nitrogen protection, 10-11 parts by weight of triethylamine, 13-14 parts by weight of 5',5-diallyl-2,2'-biphenylhydroquinone, and 100-110 parts by weight of toluene are stirred and mixed evenly. 9.5-10.5 parts by weight of phenylphosphonic dichloride are added dropwise at room temperature, and the addition is completed within 10 minutes. The mixture is then heated to 60-70°C and kept at this temperature for 11-13 hours. The mixture is then washed with deionized water until clear and non-turbid. Toluene is then removed by distillation, and the mixture is allowed to stand overnight to obtain the desired product. The crystals were removed and dried to obtain an intermediate. Under nitrogen protection, 90-110 parts by weight of tetrahydrofuran were added to the intermediate and stirred for 20-40 minutes. Then, 3.8-4.2 parts by weight of mercaptoethylamine were added and stirred for another 25-35 minutes. Finally, 0.48-0.54 parts by weight of photoinitiator were added, and the mixture was reacted at room temperature under ultraviolet light for 50-70 minutes. The tetrahydrofuran was then removed by rotary evaporation. The mixture was washed 2-4 times with acetone and deionized water, and then dried to obtain the second curing agent.

7. The method for preparing the toughened one-component epoxy adhesive according to claim 6, characterized in that, The photoinitiator used is benzoin dimethyl ether.

8. The method for preparing the toughened one-component epoxy adhesive according to claim 6, characterized in that, The ultraviolet light wavelength is 320~420nm.

9. The method for preparing the toughened one-component epoxy adhesive according to claim 5, characterized in that, The heat stabilizer is prepared as follows: 5.8-7 parts by mass of unsaturated alcohol, 2-3 parts by mass of C60, 100-200 parts by mass of chloroform, and 0.34-0.48 parts by mass of aluminum trichloride are stirred and mixed for 50-70 minutes, then heated to 60-70℃ and stirred for 23-25 ​​hours. After standing and separation, the chloroform is washed away with anhydrous ethanol and dried to obtain the heat stabilizer.

10. The method for preparing the toughened one-component epoxy adhesive according to claim 5, characterized in that, The unsaturated alcohols include allyl alcohol.