Toughened epoxy resin composite material as well as preparation, degradation and recovery method and product application thereof

Abstract

The invention relates to a toughened epoxy resin composite material, a preparation and degradation recovery method thereof, and a product application, and belongs to the field of epoxy resin toughening. The composite material comprises a component A and a component B, the component A comprises epoxy resin, an epoxy resin diluent and a hyperbranched epoxy resin flexibilizer, and the component B comprises an amine curing agent, an anhydride curing agent and an accelerant; the mass ratio of the component A to the component B is 100: (30-65), and every 100 parts of the component A comprises 20-70 wt% of epoxy resin, 1-30 wt% of an epoxy resin diluent and 5-50 wt% of a hyperbranched epoxy resin flexibilizer; every 100 parts of the component B comprises 10 wt%-90 wt% of an amine curing agent, 5 wt%-85 wt% of an anhydride curing agent and 0 wt%-5 wt% of an accelerant. The target product can be synthesized through two-step controllable reaction, tedious protection steps are not needed, and the technological process is remarkably shortened. The reaction is carried out under normal pressure and medium and low temperature conditions, high-pressure equipment or a high-energy-consumption process is not needed, and the method is suitable for industrial large-scale production.

Description

Technical Field

[0001] The invention belongs to the field of degradable epoxy resin and epoxy resin toughening, and particularly relates to a toughened epoxy resin composite material, a preparation method thereof, a degradation and recycling method thereof, and an application of the product. Background Art

[0002] Epoxy resin, an important thermosetting polymer material, is widely used in aerospace, electronic packaging, coatings, composite materials, and other fields due to its excellent bonding properties, chemical stability, mechanical strength, and electrical insulation. However, while the three-dimensional cross-linked network structure formed after curing imparts high strength and high modulus, it also leads to inherent brittleness and poor impact resistance. It is particularly prone to cracking under dynamic loads or in low-temperature environments, severely restricting its application in high-end fields. Furthermore, the insoluble and infusible nature of epoxy resin after curing also means that waste epoxy resin poses a significant environmental burden.

[0003] To improve the toughness of epoxy resins, researchers both domestically and internationally have proposed various toughening strategies. Early approaches primarily involved the addition of rubber elastomers (such as carboxyl-terminated nitrile butadiene rubber (CTBN)) or thermoplastics (such as polyethersulfone and polyimide). However, these methods often result in a significant decrease in the material's modulus and heat resistance, and the toughening phase suffers from poor compatibility with the epoxy matrix, leading to phase separation. In recent years, the incorporation of nanoparticles (such as nanosilica and carbon nanotubes) has garnered attention due to its synergistic strengthening and toughening effects. For example, patent CN116102684A discloses a method for preparing a core-shell submicron / nanoparticle toughening agent. Using emulsion polymerization, styrene was grafted onto polybutadiene latex to synthesize a series of core-shell polybutadiene-grafted polystyrene copolymers. By tailoring the composition and micromorphology of the rubber particles, a core-shell toughening agent with controllable structure was prepared. However, challenges such as difficulty dispersing the nanoparticles, agglomeration, and high cost have limited their large-scale application. In addition, although chemical modification methods (such as introducing flexible segments) can improve toughness, the synthesis steps are complicated and may sacrifice other properties of epoxy resins.

[0004] Hyperbranched polymers, due to their highly branched three-dimensional structure, abundant terminal functional groups, and intramolecular cavities, have become a research hotspot in the field of epoxy resin toughening. Compared with traditional linear toughening agents, hyperbranched polymers have low viscosity, high solubility, and good compatibility with epoxy matrices. They can absorb energy through mechanisms such as crazing and shear yielding, significantly improving toughness without significantly reducing the material's rigidity or heat resistance. Summary of the Invention

[0005] To address the above-mentioned technical problems, the present invention provides a toughened epoxy resin composite, its preparation, degradation and recovery methods, and product applications. The present invention utilizes a simple two-step process to synthesize a hyperbranched epoxy resin toughening agent containing ester and ether bonds. A polyol (such as trifunctional glycerol) provides multiple hydroxyl sites. When alternately condensed with a diacid, the steric hindrance and reactivity of the multiple hydroxyl groups preferentially form branching points rather than linear segments, gradually building a hyperbranched polyester backbone. By controlling the acid value of the reaction system, a hyperbranched polyester with terminal carboxyl groups is obtained. Subsequently, the carboxylate ion acts as a nucleophile to attack the electron-deficient oxygen atom (the epoxy ring strain region) in the glycidyl ether epoxy group, initiating ring-opening polymerization of the epoxy groups to produce the hyperbranched epoxy resin toughening agent. The prepared epoxy resin toughener combines the initial polyol branching points with subsequent epoxy group grafting to form a highly branched three-dimensional network. The intramolecular cavity and multi-terminal group characteristics facilitate stress dispersion and energy dissipation. The terminal epoxy groups impart excellent compatibility and co-curing ability to the resin and epoxy matrix, participating in the formation of a cross-linked network during the curing process, achieving a synergistic toughening-reinforcement effect and significantly improving the toughness of the epoxy resin. Furthermore, the abundant ester bonds in the molecular chain of the hyperbranched epoxy resin toughener, introduced into the epoxy resin composite, impart degradability to the cured epoxy resin. The degradation solution, comprising an ionic liquid, a strong base, and a degradation solvent, achieves efficient depolymerization of the ester-bonded epoxy resin through the solvation and catalysis of the ionic liquid, the nucleophilic attack of the strong base, and the synergistic effects of the solvent. The degradation products can be fully recovered and reused through simple post-processing.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A toughened epoxy resin composite comprises a component A and a component B; the component A comprises an epoxy resin, an epoxy resin diluent, and a hyperbranched epoxy resin toughening agent; the component B comprises an amine curing agent, an acid anhydride curing agent, and an accelerator; the mass ratio of the component A to the component B is 100:30-65, and every 100 parts of the component A comprises 20wt%-70wt% of the epoxy resin, 1wt%-30wt% of the epoxy resin diluent, and 5wt%-50wt% of the hyperbranched epoxy resin toughening agent; and every 100 parts of the component B comprises 10wt%-90wt% of the amine curing agent, 5wt%-85wt% of the acid anhydride curing agent, and 0wt%-5wt% of the accelerator.

[0008] Furthermore, the epoxy resin is one or more of glycidyl ether epoxy resin, glycidyl amine epoxy resin, and glycidyl ester epoxy resin; the glycidyl ether epoxy resin is glycidyl-terminated poly(bisphenol A-co-epichlorohydrin) , bisphenol A diglycidyl ether , polyethylene glycol diglycidyl ether , Bisphenol A propoxylic acid diglycidyl ether , bisphenol F diglycidyl ether One or more of; the glycidyl ester epoxy resin is diglycidyl hexahydrophthalate or diglycidyl terephthalate ;

[0009] The epoxy resin diluent is a small molecule oligomer with a terminal epoxy group; the epoxy resin diluent is at least one of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, benzyl glycidyl ether, butyl glycidyl ether, and phenyl glycidyl ether;

[0010] The molecular structure formula of the hyperbranched epoxy resin toughening agent is as follows:

[0011]

[0012] Wherein, R1, R2, R3, and R4 are one or more of a C1-C18 aliphatic carbon chain, a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus, or silicon and its derivatives; m = 1 to 20; n = 2 to 6;

[0013] The amine curing agent is one or more of an aromatic amine, an aliphatic amine, or a polyetheramine. The aromatic amine is one or more of m-phenylenediamine (MPD), diaminodiphenylmethane (DDM), diaminodiphenylsulfone (DDS), and methylaniline. The aliphatic amine is one or more of menthanediamine, 1,3-bis(aminomethyl)cyclohexane, diaminodicyclohexylmethane (PACM), 3,3'-dimethyl-4,4-diaminodicyclohexylmethane (MACM), 4,4'-diaminodicyclohexylmethane, and isophoronediamine (IPDA). The polyetheramine is selected based on a molecular weight of 230 to 2000, at least two terminal amino groups, a polyether backbone, and an amino group as the terminal active functional group. Polyetheramines include one or more of polyetheramine D230 and polyetheramine D400.

[0014] The acid anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and methylhexahydrophthalic anhydride;

[0015] The accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethanolamine, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0016] Furthermore, the preparation method of the hyperbranched epoxy resin toughening agent is:

[0017] Step 1: using polyol and diacid to carry out esterification reaction to obtain a hyperbranched polyester skeleton with carboxyl terminal groups;

[0018] Step 2: The hyperbranched polyester skeleton synthesized in step 1 is subjected to ring-opening polymerization with a difunctional glycidyl ether to synthesize a hyperbranched epoxy resin toughening agent having an epoxy end group.

[0019] The chemical equations involved are as follows:

[0020]

[0021] Furthermore, the preparation method of the hyperbranched epoxy resin toughening agent is specifically as follows:

[0022] Step 1, preparation of carboxyl-terminated hyperbranched polyester skeleton: take diacid and place it in a three-necked flask, connect a serpentine condenser with a water separator, heat the oil bath to 70-100°C, add a polyol with a molar mass of 0.1-1 times that of the diacid, heat to 130-200°C, stir and react under nitrogen for 1-10 hours, and measure the acid value of the reaction system every 30-60 minutes to determine the degree of esterification reaction. The acid value of the obtained carboxyl-terminated hyperbranched polyester skeleton should be within the range of 120-180 mg KOH / g. If the acid value is too high, continue to extend the reaction time. After the reaction is completed, place the carboxyl-terminated hyperbranched polyester skeleton in a vacuum oven at 80-100°C to dry the moisture;

[0023] Step 2: Preparation of hyperbranched epoxy resin toughening agent

[0024] Place a carboxyl-terminated hyperbranched polyester backbone and a calculated amount of difunctional glycidyl ether in a three-necked flask, connect a serpentine condenser with a water separator, raise the temperature to 80-150°C, and stir the reaction under nitrogen for 1-10 hours. Measure the acid value of the reaction system every 30-60 minutes. The acid value of the resulting hyperbranched epoxy resin toughening agent should be within the range of 0-3 mg KOH / g, the epoxy value should be within the range of 0.5-0.8 eq / 100g, and the viscosity should be within the range of 1000-2000 mPa·s. If the acid value, epoxy value, and viscosity are not within the range, continue to adjust the reaction conditions such as the reactant ratio, reaction temperature, and reaction time.

[0025] Furthermore, the polyol structure is , wherein R1 and R2 are one or more of a C1-C18 aliphatic carbon chain, a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus or silicon and its derivatives. The polyol is one or more of glycerol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, xylitol, and sorbitol; the diacid structure is , wherein R3 is one or more of a C1-C18 aliphatic carbon chain, a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus, or silicon and its derivatives. The diacid is one or more of succinic acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid. The difunctional glycidyl ether is one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and cyclohexanedimethanol diglycidyl ether.

[0026] A method for preparing the above-mentioned toughened epoxy resin composite material comprises: weighing component A and component B according to a set mass ratio; mixing the components A and B respectively and then mixing them to obtain a mixture; ultrasonically defoaming the mixture, injecting it into a mold, and curing it at 80-200°C for 1-10 hours to obtain a degradable epoxy resin composite material.

[0027] A degradation and recovery method for the toughened epoxy resin composite prepared by the above preparation method comprises the following steps: immersing 1 part of the toughened epoxy resin composite in 1 to 10 parts of a degradation liquid according to a mass ratio, heating the mixture to 80 to 150° C. for a degradation reaction for 0.5 to 10 hours, and then adding deionized water in an amount of 1 to 5 times the weight of the degradation liquid mixture to the obtained degradation mixture to precipitate and separate the degradation products, thereby obtaining a precipitated first degradation product and a liquid second degradation product.

[0028] Furthermore, the degradation liquid is a mixture of an ionic liquid, a strong base and a degradation solvent; the ionic liquid accounts for 0.5wt%~30wt% of the degradation liquid, the strong base accounts for 0.5wt%~30wt% of the degradation liquid, and the degradation solvent accounts for 50wt%~99wt% of the degradation liquid.

[0029] Furthermore, the ionic liquid is an ionic liquid containing imidazolium, ammonium, pyridinium and phosphonium cations, and is paired with various halide anions, including at least one of 1-butyl-3-methylimidazolium chloride ([Bmim] [Cl]), tetrabutylphosphine bromide ([TBP] [Br]), 1-butyl-2-methylpyridinium chloride ([BmPyr] [Cl]), 1-ethyl-3-methylimidazolium chloride ([Emim] [Cl]), 1-butyl-1-methylpiperidinium iodide ([BmPip] [I]), and 1-butyl-1-methylpyrrolidinium chloride ([BmPyrr] [Cl]);

[0030] The strong base is at least one of 1,5,7-triazabicyclo[4.4.0]decene-5-ene TBD, 1,8-diazabicyclo[5.4.0]undec-7-ene DBU, 1,5-diazabicyclo[4.3.0]non-5-ene DBN, and tetramethylguanidine TMG;

[0031] The degradation solvent is at least one of pure water, ethanol, ethylene glycol, propylene glycol, ethanolamine, diethylenetriamine, and triethylenetetramine.

[0032] An application of the product obtained by the above degradation recovery method is: the first degradation product is mixed with epoxy resin to prepare secondary epoxy resin, and the second degradation product is distilled and reused as degradation liquid.

[0033] Compared with the prior art, the advantages of the present invention are:

[0034] The present invention synthesizes the target product through a two-step controlled reaction. Compared to existing multi-step polycondensation or complex protection-deprotection methods, this method eliminates the need for cumbersome protection steps and significantly shortens the process flow. The reaction is carried out under normal pressure and at medium to low temperatures, eliminating the need for high-pressure equipment or energy-intensive processes, making it suitable for industrial scale-up.

[0035] This method precisely controls the branching density and molecular weight distribution of hyperbranched polyesters by adjusting the polyol functionality and the diacid / polyol molar ratio. The excess carboxylic acid strategy ensures a single terminal functional group in the carboxyl-terminated polyester, which is then converted to epoxy-terminated groups through a glycidyl ether ring-opening reaction. This avoids the reduced curing efficiency caused by mixed terminal groups (e.g., coexistence of hydroxyl and carboxyl groups) in traditional one-step methods.

[0036] The present invention achieves efficient selective depolymerization and resource recycling of epoxy resin through the synergistic catalytic mechanism of the ionic liquid-strong base system. Its green indicators, economic efficiency and product value are significantly better than traditional technologies, providing a degradation and recycling strategy for epoxy-based composite waste that has both environmental benefits and industrial feasibility. DETAILED DESCRIPTION

[0037] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0038] Example 1: Preparation of carboxyl-terminated hyperbranched polyester backbone

[0039] Take 2.2 mol of succinic acid and place it in a three-necked flask, connect a serpentine condenser with a water separator, heat the oil bath to 70°C, add 1 mol of pentaerythritol, heat to 130°C, and stir under nitrogen protection for 10 hours. At the same time, measure the acid value of the reaction system every 30 minutes. After the reaction, place the obtained end-carboxyl hyperbranched polyester skeleton in a vacuum oven at 80°C to dry the moisture.

[0040] Example 2: Preparation of carboxyl-terminated hyperbranched polyester backbone

[0041] Take 2.2 mol of terephthalic acid and place it in a three-necked flask, connect a serpentine condenser with a water separator, raise the oil bath temperature to 80°C, add 1 mol of trimethylolpropane, raise the temperature to 150°C, and react with nitrogen protection and stirring for 5 hours. Remove excess water with a water separator and measure the acid value of the reaction system every 30 minutes. After the reaction, place the obtained end-carboxyl hyperbranched polyester skeleton in a vacuum oven at 80°C to dry the water.

[0042] Example 3: Preparation of carboxyl-terminated hyperbranched polyester backbone

[0043] Take 2.2 mol of adipic acid and place it in a three-necked flask, connect a serpentine condenser with a water separator, raise the oil bath temperature to 80°C, add 1 mol of propylene glycol, raise the temperature to 160°C, and react with stirring under nitrogen protection for 6 hours. Remove excess water with a water separator and measure the acid value of the reaction system every 30 minutes. After the reaction, place the obtained end-carboxyl hyperbranched polyester skeleton in a vacuum oven at 80°C to dry the water.

[0044] The comprehensive properties of the carboxyl-terminated hyperbranched polyesters obtained in the above three groups of examples were measured using acid-base titration and are shown in the following table:

[0045]

[0046] Example 4: Preparation of hyperbranched epoxy resin toughening agent

[0047] 1 mol of the carboxyl-terminated hyperbranched polyester backbone prepared in Example 1 and 2.5 mol of 1,4-butanediol diglycidyl ether were placed in a three-necked flask connected to a serpentine condenser with a water separator. The temperature was raised to 120°C and stirred under nitrogen for 6 hours. The acid value of the reaction system was measured every 30 minutes. The resulting hyperbranched epoxy resin toughening agent had an acid value of 2 mg KOH / g, an epoxy value of 0.62 eq / 100 g, and a viscosity of 1207 mPa·s. This hyperbranched epoxy resin toughening agent is referred to as "Toughening Agent 1#" in the examples below.

[0048] Example 5: Preparation of hyperbranched epoxy resin toughening agent

[0049] 1 mol of the carboxyl-terminated hyperbranched polyester backbone prepared in Example 2 and 3.5 mol of cyclohexanedimethanol diglycidyl ether were placed in a three-necked flask connected to a serpentine condenser with a water separator. The temperature was raised to 140°C and stirred under nitrogen for 6 hours. The acid value of the reaction system was measured every 30 minutes. The resulting hyperbranched epoxy resin toughening agent had an acid value of 2 mg KOH / g, an epoxy value of 0.75 eq / 100 g, and a viscosity of 1523 mPa·s. This hyperbranched epoxy resin toughening agent is referred to as "Toughening Agent 2#" in the examples below.

[0050] Example 6: Preparation of hyperbranched epoxy resin toughening agent

[0051] 1 mol of the carboxyl-terminated hyperbranched polyester backbone prepared in Example 3 and 2.5 mol of 1,6-hexanediol diglycidyl ether were placed in a three-necked flask. A serpentine condenser with a water separator was attached. The temperature was raised to 80°C and stirred under nitrogen for 10 hours. The acid value of the reaction system was measured every 30 minutes. The resulting hyperbranched epoxy resin toughening agent had an acid value of 3 mg KOH / g, an epoxy value of 0.5 eq / 100 g, and a viscosity of 1143 mPa·s. This hyperbranched epoxy resin toughening agent is referred to as "Toughening Agent 3#" in the examples below.

[0052] The comprehensive properties of the hyperbranched epoxy resin toughening agents obtained in Examples 4 to 6 are as follows:

[0053]

[0054] Example 7: Preparation of toughened epoxy resin

[0055] To prepare a toughened epoxy resin, the weight ratio of component A to component B was 100:30. Component A contained 42.6 parts of bisphenol A diglycidyl ether E51 (average epoxy value 0.51), 21.8 parts of hexahydrophthalic acid diglycidyl ester, 5.3 parts of 1,4-butanediol diglycidyl ether, and 30.3 parts of toughening agent 1. Component B contained 24.3 parts of diaminodiphenylmethane, 29.8 parts of diaminodicyclohexylmethane, 33.5 parts of polyetheramine D230, 10.7 parts of tetrahydrophthalic anhydride, and 1.7 parts of 2,4,6-tris(dimethylaminomethyl)phenol. After mixing, the mixture was ultrasonically defoamed for 10 minutes, poured into a mold, and cured in an oven at 100°C for 5 hours.

[0056] Example 8: Preparation of toughened epoxy resin

[0057] To prepare a toughened epoxy resin, the weight ratio of component A to component B was 100:37. Component A, per 100 parts, consisted of: 33.6 parts of bisphenol A diglycidyl ether (average epoxy value 0.44), 43.7 parts of diglycidyl terephthalate, 3.2 parts of ethylene glycol diglycidyl ether, and 19.5 parts of toughening agent 2. Component B, per 100 parts, consisted of: 41.6 parts of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, 33.8 parts of polyetheramine D230, 22.1 parts of phthalic anhydride, and 2.5 parts of benzyldimethylamine. After thorough mixing, ultrasonic defoaming was performed for 10 minutes, followed by pouring into a mold and curing in a 120°C oven for 4 hours.

[0058] Example 9: Preparation of toughened epoxy resin

[0059] Prepare a toughened epoxy resin with a weight ratio of 100:45 for component A and component B. Component A (per 100 parts) contains: 45.1 parts bisphenol A diglycidyl ether with an average epoxy value of 0.51, 35.3 parts diglycidyl terephthalate, 5.5 parts 1,6-hexanediol diglycidyl ether, and 14.1 parts toughening agent #3. Component B (per 100 parts) contains: 15.8 parts diaminodicyclohexylmethane, 16.9 parts polyetheramine D400, 65.3 parts hexahydrophthalic anhydride, and 2 parts benzyldimethylamine. After thorough mixing, ultrasonic defoaming was performed for 10 minutes. The mixture was then poured into a mold and cured in an oven at 150°C for 5 hours.

[0060] Example 10: Preparation of toughened epoxy resin

[0061] To prepare a toughened epoxy resin, the weight ratio of component A to component B was 100:54. Component A, per 100 parts, consisted of 22.4 parts of bisphenol A diglycidyl ether (average epoxy value 0.51), 28.5 parts of hexahydrophthalic acid diglycidyl ester, 7.9 parts of 1,6-hexanediol diglycidyl ether, and 41.2 parts of toughening agent 3. Component B, per 100 parts, consisted of 51.6 parts of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, 35.2 parts of polyetheramine D230, 10.8 parts of hexahydrophthalic anhydride, and 2.4 parts of benzyldimethylamine. After thorough mixing, ultrasonic defoaming was performed for 10 minutes. The resin was then poured into a mold and cured in an 80°C oven for 7 hours.

[0062] Example 11: Preparation of toughened epoxy resin

[0063] To prepare a toughened epoxy resin, the weight ratio of component A to component B was 100:60. Component A, per 100 parts, consisted of: 32.6 parts of bisphenol A diglycidyl ether with an average epoxy value of 0.44, 38.7 parts of hexahydrophthalic acid diglycidyl ester, 5.8 parts of 1,4-butanediol diglycidyl ether, and 22.9 parts of toughening agent #1. Component B, per 100 parts, consisted of: 23.8 parts of methylaniline, 34.1 parts of polyetheramine D400, 39.5 parts of methylhexahydrophthalic anhydride, and 2.6 parts of benzyldimethylamine. After thorough mixing, ultrasonic defoaming was performed for 10 minutes, followed by pouring into a mold and curing in an oven at 110°C for 5 hours.

[0064] The comprehensive properties of the epoxy resin composites obtained by curing the above Examples 7 to 11 are shown in the following table:

[0065]

[0066] Example 12: Degradation of toughened epoxy resin

[0067] The epoxy resin obtained by curing in Example 7 was subjected to degradation. The weight ratio of epoxy resin to degradation solution was 1:3. For every 100 parts of degradation solution, the following components were weighed: 15 parts 1-butyl-3-methylimidazolium chloride, 15 parts TBD, and 70 parts ethanolamine. Under nitrogen protection, the mixture was stirred at 80°C for 9 hours to complete degradation, yielding a degradation mixture. The degradation mixture was a light yellow solution.

[0068] Example 13: Degradation of toughened epoxy resin

[0069] The epoxy resin obtained by curing in Example 11 was subjected to degradation. The weight ratio of epoxy resin to degradation solution was 1:1. For every 100 parts of degradation solution, the following components were weighed: 15 parts tetrabutylphosphonium bromide, 25 parts DBN, and 60 parts diethylenetriamine. Under nitrogen protection, the mixture was stirred at 100°C for 8 hours to complete degradation, yielding a degradation mixture. The degradation mixture was a light yellow solution.

[0070] Example 14: Degradation of toughened epoxy resin

[0071] The epoxy resin obtained by curing in Example 9 was subjected to degradation. The weight ratio of epoxy resin to degradation solution was 1:5. For every 100 parts of degradation solution, the following components were weighed: 20 parts 1-butyl-2-methylpyridinium chloride, 15 parts DBU, and 65 parts triethylenetetramine. Under nitrogen protection, the mixture was stirred at 120°C for 4 hours to complete degradation, yielding a degradation mixture. The degradation mixture was a pale yellow solution.

[0072] Example 15: Full Recycling of Toughened Epoxy Resin

[0073] The degradation mixture from Example 14 was selected, and deionized water (twice the volume of the mixture) was added to the mixture. The mixture was stirred and allowed to stand until the solids were completely precipitated. A solid first degradation product and a liquid second degradation product were separated. The first degradation product was mixed with bisphenol A diglycidyl ether having an average epoxy value of 0.51 and cured with a calculated amount of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane. The cured resin had a tensile strength of 65.1 MPa and an elongation at break of 4.1%. The liquid second degradation product, after rotary evaporation to remove the deionized water, was used as a degradation solution to degrade the epoxy resin obtained by curing in Example 9. Under nitrogen protection, the resin was completely degraded by stirring at 120°C for 4 hours.

[0074] Comparative Example 1:

[0075] Preparation of comparative epoxy resin composite:

[0076] An untoughened biodegradable epoxy resin was prepared with a weight ratio of Component A to Component B of 100:38. Component A (per 100 parts) contained 42.4 parts of bisphenol A diglycidyl ether with an average epoxy value of 0.51, 48.5 parts of hexahydrophthalic acid diglycidyl ester, and 9.1 parts of 1,6-hexanediol diglycidyl ether. Component B (per 100 parts) contained 51.6 parts of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, 35.2 parts of D230, 10.8 parts of hexahydrophthalic anhydride, and 2.4 parts of benzyldimethylamine. After thorough mixing, the mixture was ultrasonically defoamed for 10 minutes, poured into a mold, and cured in an 80°C oven for 7 hours.

[0077] The comprehensive performance comparison of the epoxy resin body obtained by curing the above comparative example and the epoxy resin body obtained in Example 7 is shown in the following table:

[0078]

[0079] The flexible chain segments of the hyperbranched epoxy resin toughening agent promote local slippage of the molecular chain, delaying brittle fracture, so that the impact strength of the epoxy resin body with the hyperbranched epoxy resin toughening agent is improved compared with the control ratio. At the same time, the flexible chain segments of the toughening agent itself make its Tg lower, which affects the Tg of the epoxy resin body after blending with the epoxy resin.

[0080] Comparative Example Epoxy Resin Degradation:

[0081] The epoxy resin obtained by curing in Comparative Example 1 was subjected to degradation. The weight ratio of epoxy resin to degradation solution was 1:3. For every 100 parts of degradation solution, the solution comprised 20 parts of tetrabutylphosphonium bromide, 10 parts of DBN, and 70 parts of pure water. Under nitrogen protection, the mixture was stirred at 100°C for 7 hours to complete degradation, yielding a degradation mixture.

[0082] Comparative Example Recycling of Epoxy Resin:

[0083] The degradation mixture from Comparative Example 1 was selected. Deionized water (twice the volume of the mixture) was added to the mixture. The mixture was stirred and allowed to stand until the solids completely precipitated. A solid first degradation product and a liquid second degradation product were separated. The first degradation product was mixed with bisphenol A diglycidyl ether having an average epoxy value of 0.51 and cured with a calculated amount of 3,3'-dimethyl-4,4-diaminodicyclohexylmethane. The cured resin exhibited a tensile strength of 57.9 MPa and an elongation at break of 3.1%. The liquid second degradation product, after being evaporated to remove the deionized water, was used as the degradation solution to degrade the epoxy resin obtained from Comparative Example 1. Under nitrogen protection, the resin was completely degraded by stirring at 120°C for 4 hours. This indicates that the addition of a toughening agent does not affect the degradation of the epoxy resin.

Claims

1. A toughened epoxy resin composite, characterized in that: The composite material includes a component A and a component B; the component A includes an epoxy resin, an epoxy resin diluent, and a hyperbranched epoxy resin toughening agent; the component B includes an amine curing agent, an acid anhydride curing agent, and an accelerator; the mass ratio of the component A to the component B is 100:30-65, and every 100 parts of the component A includes 20wt%-70wt% of the epoxy resin, 1wt%-30wt% of the epoxy resin diluent, and 5wt%-50wt% of the hyperbranched epoxy resin toughening agent; and every 100 parts of the component B includes 10wt%-90wt% of the amine curing agent, 5wt%-85wt% of the acid anhydride curing agent, and 0wt%-5wt% of the accelerator.

2. The toughened epoxy resin composite according to claim 1, characterized in that: The epoxy resin is one or more of glycidyl ether epoxy resin, glycidyl amine epoxy resin, and glycidyl ester epoxy resin; The epoxy resin diluent is at least one of 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, benzyl glycidyl ether, butyl glycidyl ether, and phenyl glycidyl ether; The molecular structure formula of the hyperbranched epoxy resin toughening agent is as follows: Wherein, R1, R2, R3, and R4 are one or more of a C1-C18 aliphatic carbon chain, a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus, or silicon and its derivatives; m = 1 to 20; n = 2 to 6; The amine curing agent is one or more of aromatic amine, aliphatic amine or polyether amine; The acid anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and methylhexahydrophthalic anhydride; The accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)phenol, benzyldimethylamine, triethanolamine, 2-ethyl-4-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

3. The toughened epoxy resin composite according to claim 2, characterized in that: The preparation method of the hyperbranched epoxy resin toughening agent is: Step 1: using polyol and diacid to carry out esterification reaction to obtain a hyperbranched polyester skeleton with carboxyl terminal groups; Step 2: The hyperbranched polyester skeleton synthesized in step 1 is subjected to ring-opening polymerization with a difunctional glycidyl ether to synthesize a hyperbranched epoxy resin toughening agent having an epoxy end group.

4. The toughened epoxy resin composite according to claim 3, characterized in that: The preparation method of the hyperbranched epoxy resin toughening agent is specifically as follows: Step 1, preparation of a carboxyl-terminated hyperbranched polyester skeleton: take a diacid and place it in a three-necked flask, connect a serpentine condenser with a water separator, heat the oil bath to 70-100°C, add a polyol with a molar mass of 0.1-1 times that of the diacid, heat to 130-200°C, stir under nitrogen protection, react for 1-10 hours, and measure the acid value of the reaction system every 30-60 minutes. The acid value of the obtained carboxyl-terminated hyperbranched polyester skeleton should be in the range of 120-180 mg KOH / g. After the reaction is completed, the carboxyl-terminated hyperbranched polyester skeleton is placed in a vacuum oven at 80-100°C to dry the moisture; Step 2: Preparation of hyperbranched epoxy resin toughening agent A carboxyl-terminated hyperbranched polyester backbone and a calculated amount of difunctional glycidyl ether were placed in a three-necked flask, connected to a serpentine condenser with a water separator, and heated to 80-150°C. The mixture was stirred under nitrogen protection for 1-10 hours. The acid value of the reaction system was measured every 30-60 minutes. The acid value of the resulting hyperbranched epoxy resin toughening agent should be within the range of 0-3 mg KOH / g, the epoxy value should be within the range of 0.5-0.8 eq / 100 g, and the viscosity should be within the range of 1000-2000 mPa·s.

5. A toughened epoxy resin composite according to claim 3 or 4, characterized in that: The polyol is one or more of glycerol, trimethylolpropane, pentaerythritol, ditrimethylolpropane, xylitol, and sorbitol; the diacid is one or more of succinic acid, adipic acid, sebacic acid, terephthalic acid, and isophthalic acid; and the difunctional glycidyl ether is one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and cyclohexanedimethanol diglycidyl ether.

6. A method for preparing the toughened epoxy resin composite according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: weighing component A and component B according to a set mass ratio; uniformly mixing the component A and the component B respectively, and then mixing to obtain a mixture; ultrasonically defoaming the mixture, injecting the mixture into a mold, and curing the mixture at 80-200° C. for 1-10 hours to obtain a degradable epoxy resin composite.

7. A method for recycling the toughened epoxy resin composite prepared by the preparation method according to claim 6, characterized in that: According to the mass ratio, 1 part of the toughened epoxy resin composite is immersed in 1-10 parts of the degradation liquid, the temperature is raised to 80-150° C. and the degradation reaction is carried out for 0.5-10 hours. Then, deionized water with an amount of 1-5 times the weight of the degradation liquid mixture is added to the obtained degradation mixture to precipitate and separate the degradation products, thereby obtaining a precipitated first degradation product and a liquid second degradation product.

8. The degradation and recycling method of a toughened epoxy resin composite according to claim 7, characterized in that: The degradation liquid is a mixture of an ionic liquid, a strong base and a degradation solvent; the ionic liquid accounts for 0.5wt%~30wt% of the degradation liquid, the strong base accounts for 0.5wt%~30wt% of the degradation liquid, and the degradation solvent accounts for 50wt%~99wt% of the degradation liquid.

9. The degradation and recycling method of a toughened epoxy resin composite according to claim 8, characterized in that: The ionic liquids are ionic liquids containing imidazolium, ammonium, pyridinium and phosphonium cations, and are paired with various halide anions; The strong base is at least one of 1,5,7-triazabicyclo[4.4.0]decene-5-ene, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5-diazabicyclo[4.3.0]non-5-ene, and tetramethylguanidine; The degradation solvent is at least one of pure water, ethanol, ethylene glycol, propylene glycol, ethanolamine, diethylenetriamine, and triethylenetetramine.

10. An application of the product obtained by the degradation recovery method according to any one of claims 7 to 9, characterized in that: The application is as follows: the first degradation product is mixed with epoxy resin to prepare secondary epoxy resin, and the second degradation product is distilled and reused as degradation liquid.

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