Ester-group-containing functionality-controllable epoxy resin and preparation and low-temperature recovery method of composite material of ester-group-containing functionality-controllable epoxy resin

Abstract

The invention relates to preparation and low-temperature recovery methods of ester group-containing functionality-controllable epoxy resin and a composite material thereof. The method comprises the following steps: carrying out click chemical reaction on a thiol compound and carbon-carbon double bond-containing epoxide in a solvent under the initiation of 365nm ultraviolet light at the reaction temperature of 0-20 DEG C for 0.25-6 hours, and drying the solution by distillation to obtain the ester group-containing functionality-controllable epoxy resin, the molar ratio of sulfydryl to carbon-carbon double bonds in the thiol compound is 1: 1. According to the invention, an ester group-containing structure is introduced through click chemistry, and the controllability of the functionality degree of the epoxy resin is realized, so that the crosslinking density of a cured product is accurately regulated and controlled. The design not only endows a cured product with an excellent toughening effect, higher glass transition temperature and remarkably improved mechanical properties, but also endows the cured product with green and efficient degradation properties.

Description

Technical Field

[0001] The present invention belongs to the field of high molecular compounds, relates to the technical field of epoxy resins, and particularly relates to a preparation and low-temperature recovery method of an epoxy resin with controllable ester group functionality and its composite material. Background Art

[0002] Due to its excellent mechanical properties, chemical stability and adhesion properties, epoxy resins have been widely used in many fields such as electronics, aerospace, automotive, construction and wind turbine blades. However, the chemical structure of traditional epoxy resins is mainly composed of C-C, C-O and C-N bonds, and the bond energies of these bonds are relatively high, resulting in difficulty in degradation and recycling after use. Especially in the field of wind turbine blades with large-scale applications, the treatment after retirement has become an increasingly serious environmental problem. With the global emphasis on environmental protection, developing recyclable epoxy resin systems has become an important research direction in the field of materials science. In recent years, it has been found that epoxy resin systems containing dynamic bonds have relatively good degradability. The introduction of dynamic bonds provides potential degradability for the degradation of epoxy resins, and is more likely to undergo hydrolysis or cleavage under specific conditions (such as acid, base or enzyme catalysis), thereby realizing the degradation and recycling of materials. CN115353610B discloses an aqueous epoxy resin degradable in water and its preparation method. By reacting a hydrophilic polyhydroxy diacid with an epoxy resin, an aqueous epoxy resin containing a large number of hydroxyl groups and ester bonds can be obtained. The unique network structure in this resin can promote the occurrence of transesterification hydrolysis reactions from multiple angles, thereby realizing the complete degradation of the material in water (transesterification-degradation). CN116675656B discloses a biomass epoxy monomer, a highly heat-resistant epoxy resin and a preparation method. Using bisphenolic acid and ethylene glycol as raw materials, a phenolic compound is synthesized by a solvent-free method, and the phenolic compound is reacted with epichlorohydrin to synthesize a tetra-functional biomass epoxy monomer. A biomass epoxy resin that is degradable, recyclable and reshaped is prepared using natural camphoric acid as a curing agent. The above technologies verify that the introduction of dynamic ester groups can endow epoxy resins with recyclable and reusable characteristics. However, the existing preparation methods of epoxy resins containing ester groups have problems such as poor controllability of functionality and difficulty in adjusting crosslinking density, and the degradation methods are usually complex and require harsh conditions, which limits their application in high-performance composite materials. Summary of the Invention

[0003] The purpose of the present invention is to solve the problems that the service performance and degradation performance of existing epoxy resins are difficult to match, and the degradation method is complex and requires harsh conditions, and to provide a preparation and low-temperature recovery method of an epoxy resin with controllable ester group functionality and its composite material.

[0004] Through click chemistry, the present invention efficiently links a multi-thiol compound containing an ester group with an epoxide containing a double bond to generate a novel epoxy resin containing an ester group with controllable functionality. This method not only realizes the degradability of epoxy resins but also significantly improves the comprehensive properties of the cured products, including toughening effect, glass transition temperature, and mechanical properties, by precisely controlling the functionality and crosslinking density. This epoxy resin system provides a new idea for solving the environmental problem of the difficult recycling of traditional epoxy resins and at the same time meets the strict requirements of high-performance composite materials for material properties.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A kind of epoxy resin with controllable functionality containing an ester group, the general molecular structure formula of the epoxy resin is as follows:

[0006] R1, R2, R3 are one or more of an aliphatic carbon chain of C1-C 18 the benzene ring and its derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus, or silicon elements; R4, R5 are a hydrogen atom, an aliphatic carbon chain of C1-C 18 the benzene ring and its derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus, or silicon elements.

[0007] A preparation method of the epoxy resin with controllable functionality containing an ester group as claimed in claim 1, the method is: a thiol compound and an epoxide containing a carbon-carbon double bond undergo a click chemical reaction under the initiation of 365 nm ultraviolet light in a solvent, the reaction temperature is 0-20 o °C, the reaction time is 0.25-6 h, after completion, the solution is evaporated to dryness to obtain the epoxy resin with controllable functionality containing an ester group; the molar ratio of the mercapto group in the thiol compound to the carbon-carbon double bond is 1:1. The involved chemical equation is as follows:

[0008] Furthermore, the thiol compound is one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(3-mercaptopropionate), glycerol tri(3-mercaptopropionate), neopentyl glycol bis(3-mercaptopropionate), trimethylolethane tri(3-mercaptopropionate), polyethylene glycol bis(3-mercaptopropionate), or dipentaerythritol hexa(3-mercaptopropionate); the epoxide containing a carbon-carbon double bond is one of allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, fluoroallyl glycidyl ether, or butenyl glycidyl ether; The solvent is at least one of toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, ether, tetrahydrofuran, chloroform, acetone, and acetonitrile.

[0009] A composite material containing an epoxy resin with controllable ester group functionality prepared by the above preparation method, the composite material includes an epoxy resin component, a curing agent component, a curing accelerator, and a toughening agent; the molar ratio of epoxy groups to active hydrogen in the curing agent is 1:1 - 1.2; the curing accelerator accounts for 0 wt% - 3 wt% of the composite material, and the toughening agent accounts for 0 wt% - 5 wt% of the composite material; The epoxy resin component includes an epoxy resin with controllable ester group functionality and a conventional epoxy resin, and the epoxy resin with controllable ester group functionality accounts for 0.1 wt% - 50 wt% of the epoxy resin component; the conventional epoxy resin accounts for 50 wt% - 99.9 wt% of the epoxy resin component; the conventional epoxy resin is bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4 - butanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, alicyclic glycidyl ether, cyclohexanedimethanol diglycidyl ether, C12 - C14 fatty alcohol glycidyl ether, phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, methyltetrahydrophthalic acid diglycidyl ester, endomethylenetetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, trimellitic anhydride triglycidyl ester, 4,5 - epoxyhexane - 1,2 - dicarboxylic acid diglycidyl ester, pyromellitic acid tetraglycidyl ester, 4,4'-diaminodiphenylmethane epoxy resin, triglycidyl p - aminophenol, tetraglycidyl m - xylylenediamine, triglycidyl carbamate, N,N,N',N'-tetraglycidyl - 4,4'-diaminodiphenyl ether, triglycidyl isocyanurate, or one or more of them; The curing agent component is an amine curing agent or an acid anhydride curing agent; The amine curing agent is one or more of 3 - aminomethyl - 3,5,5 - trimethylcyclohexylamine, 4,4 - diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl - 4,4 - diaminodicyclohexylmethane, menthane diamine, hydrogenated diaminodiphenylmethane, N - aminoethylpiperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diaminodiphenylmethane, diaminodiphenyl sulfone, m - xylylenediamine, polyetheramine, dicyandiamide, and isophorone diamine; The acid anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dodecenyl succinic anhydride, maleic anhydride, pyromellitic dianhydride, chlorendic anhydride, polyazelanic anhydride, endomethylenetetrahydrophthalic anhydride, benzophenone tetracarboxylic dianhydride; The curing accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)benzene, 1,8-diazabicyclo[5,4,0]-7-undecene, benzyldimethylamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-mercaptobenzothiazole, metal acetylacetonate; The toughening agent is one or several of inorganic nanoparticles, polyether polyol, polysulfide rubber, and PU prepolymer.

[0010] A preparation method of the above-mentioned epoxy resin composite material with controllable ester group functionality takes various raw materials according to the raw material content and mixes them, and sets the temperature at room temperature - 200 o °C, and the curing time is 2 - 24 h.

[0011] A low-temperature recovery method of the above-mentioned epoxy resin composite material with controllable ester group functionality, the method is: Step 1: Immerse the composite material casting body in the catalytic degradation solution, and carry out a catalytic bond-breaking reaction for 1 - 100 hours within the temperature range of 60 - 100 o °C to obtain a solid-liquid mixture; Step 2: Further degradation of the residual resin: Immerse the incompletely degraded product in Step 1 in an organic solvent containing a Lewis acid catalyst, and carry out catalytic bond-breaking within the temperature range of 30 - 100 o °C, supplemented with microwave treatment, and react for 1 - 100 hours to obtain a degraded mixed solution. The degraded mixed solution is separated by vacuum distillation to obtain a recovered organic solvent and a recovered resin product.

[0012] Further, in Step 1, the catalytic degradation solution includes a mixture of one or several of amine compounds, alcohol compounds, and alcoholamine compounds, as well as a basic catalyst; The mass ratio of the basic catalyst is 0.1 - 10%, and the mass ratio of other compounds is 90 - 99.9%.

[0013] The amine compounds are one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, butanediamine, hexanediamine, isophoronediamine, oleylamine, isopropylamine, tert-butylamine, benzylamine, cyclohexylamine, propyleneamine, pyrrolidineamine; The alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, cyclohexanol, glycerol, ethylene glycol, propylene glycol, butanediol, pentanediol, pentaerythritol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, polytetrahydrofuran diol, polypropylene glycol, castor oil-based diol, and polycarbonate diol; The alkanolamine compound is one or more of ethanolamine, diethanolamine, isopropanolamine, aminomethyl propanol, hydroxyethyl ethylenediamine, diethylene glycol amine, 1-amino-2-propanol, 1-amino-2-butanol, phenylethanolamine, 2-amino-2-methyl-1-propanol, and 2-amino-1-butanol; The basic catalyst is one or several of 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-7-undecene, N-aminoethyl piperazine, and modified 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0014] Further, in step two, the mass ratio of the Lewis acid catalyst is 0.1 wt% - 10 wt%, and the mass ratio of the organic solvent is 90 wt% - 99.9 wt%; The Lewis acid catalyst is one or more of aluminum trichloride, ferric trichloride, titanium tetrachloride, boron trifluoride, boron trichloride, zinc chloride, zinc acetate, trimethylaluminum, diethylzinc, triphenylboron, scandium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, and aluminum chloride-imidazole salt; The organic solvent is at least one of isopentane, n-pentane, petroleum ether, hexane, cyclohexane, benzene, toluene, dichloromethane, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, ether, tetrahydrofuran, chloroform, dioxane, acetone, and acetonitrile.

[0015] A method for reusing the recovered resin product obtained by the above method, the method is: mixing the hydroxyl-terminated recovered resin product and epichlorohydrin according to a molar ratio of 1:1.5 - 2, adding a phase transfer catalyst to the reaction system, and the dosage is 0.1 - 5% of the mass of the recovered resin product. Under stirring conditions, the reaction system is heated to 30 - 100 o °C, preferably 50 - 80 o °C, the reaction time is 1 - 10 hours, preferably 3 - 6 hours. Add an alkaline solution to the above reaction system, the base is preferably sodium hydroxide, the mass concentration of the alkaline solution is 60 - 100%, and the dosage is 1 - 5 times the molar amount of the recovered resin product; Under stirring conditions, the reaction system is heated to 30 - 100 o °C, preferably 50 - 80 oC is subjected to a closed-loop reaction for 1 - 10 hours, preferably 3 - 6 hours. After the reaction is completed, stirring is stopped, and the reaction product is cooled to room temperature. An appropriate amount of water is added for washing. After stirring evenly, it is allowed to stand for layer separation. The aqueous layer is removed, and the washing is repeated several times until the aqueous layer is neutral. After drying, the excess epichlorohydrin in the organic layer is removed by rotary evaporation to obtain the recycled epoxy resin.

[0016] Further, the phase transfer catalyst is one of tetrabutylammonium bromide, tetraethylammonium bromide, benzyltriethylammonium chloride, cetyltrimethylammonium bromide, tetraphenylphosphonium bromide, ethyltriphenylphosphonium bromide, etc.

[0017] A low-temperature catalytic degradation method for a recyclable epoxy resin composite material, wherein the recyclable epoxy resin composite material is prepared by compounding a recyclable epoxy resin compound, a reinforcing body, and auxiliary materials. The degradation, recovery, and reuse methods of the recyclable epoxy resin composite material can be realized with reference to the compound.

[0018] The composite material further includes a reinforcing body and auxiliary materials; The reinforcing body is at least one of carbon fiber, glass fiber, natural fiber, chemical fiber, fabric made of fiber material, nanocarbon material, boron nitride nanomaterial, metal nanoparticle, metal oxide nanoparticle, and organic nanoparticle, accounting for 50wt% - 65wt% of the total mass of the composite material; The auxiliary materials are at least one of accelerator, diluent, plasticizer, toughening agent, thickening agent, coupling agent, defoaming agent, leveling agent, ultraviolet absorber, antioxidant, brightening agent, fluorescent reagent, pigment, and filler, accounting for 0.1wt% - 2wt% of the total mass of the composite material.

[0019] The beneficial effects of the present invention compared with the prior art are as follows: (1) The present invention prepares an epoxy resin with controllable ester group functionality by the click chemistry method. This method has significant advantages such as clear structure, high yield, and low cost. In addition, this epoxy resin with controllable ester group functionality can be compatible with commonly used existing curing agents, meeting the usage requirements in actual production.

[0020] (2) The epoxy resin with controllable ester group functionality can achieve the dissociation of the ester group under the action of amine, alcohol, or alcohol-amine compounds, thereby endowing the material with the properties of degradation and recovery.

[0021] (3) The present invention provides a supporting low-temperature recycling method, which adopts a two-step catalytic degradation process. First, the ester group is cleaved by ammonolysis; subsequently, the C-N bond is cleaved by catalysis with a Lewis acid. The recovered reinforcing material can be reused after separation, washing with water and drying. Finally, after the resin degradation product removes the solvent by vacuum distillation, it can be reacted with epichlorohydrin and used as a resin again. Detailed Embodiments

[0022] The technical solutions of the present invention will be further described below in conjunction with embodiments, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention, without departing from the spirit and scope of the technical solutions of the present invention, shall be covered by the protection scope of the present invention.

[0023] The present invention introduces an ester group-containing structure through click chemistry, and at the same time realizes the controllability of the functionality of the epoxy resin, thereby precisely regulating the crosslinking density of the cured product. This design not only endows the cured product with excellent toughening effect, higher glass transition temperature and significantly improved mechanical properties, but also makes it have green and efficient degradation properties. Through a specific chemical synthesis method, the epoxy resin of the present invention can form a network structure with an ideal crosslinking density during the curing process, and can be degraded under mild conditions, significantly reducing the impact on the environment. This innovative technology provides a new solution for the sustainable development of epoxy resins, and is expected to achieve more environmentally friendly and efficient material applications in multiple fields. Example 1

[0024] Synthesis and preparation of epoxy resin 1 with controllable functionality containing an ester group:

[0025] Accurately weigh 3.81 g of pentaerythritol tetra(3-mercaptopropionate) and 4.56 g of allyl glycidyl ether, dissolve them separately in 50 mL of methanol, and place them in a round-bottom flask. Under the protection of nitrogen and in an ice-water bath, irradiate the round-bottom flask with a UV lamp with a wavelength of 365 nm. Gradually add the allyl glycidyl ether solution to the pentaerythritol tetra(3-mercaptopropionate) solution and stir. After irradiating for 15 min at 20 o °C, the reaction is completed. The solvent is removed using a rotary evaporator to obtain epoxy resin 1 with controllable functionality containing an ester group. Example 2

[0026] Synthesis and preparation of epoxy resin 2 with controllable functionality containing an ester group:

[0027] Accurately weigh 2.38 g of ethylene glycol bis(3-mercaptopropionate) and 2.84 g of glycidyl methacrylate, dissolve them in 30 mL of tetrahydrofuran respectively, and place them in a round-bottom flask. Under the protection of nitrogen and in an ice-water bath, irradiate the round-bottom flask with a UV lamp with a wavelength of 365 nm. Gradually add the glycidyl methacrylate solution to the ethylene glycol bis(3-mercaptopropionate) solution and stir. After irradiating for 60 min at 18 o After the reaction is completed after C irradiation for 60 min, use a rotary evaporator to remove the solvent to obtain epoxy resin 2 with a controllable functionality containing ester groups. Example 3

[0028] Synthesis and preparation of epoxy resin 3 with a controllable functionality containing ester groups:

[0029] Accurately weigh 3.99 g of trimethylolpropane tris(3-mercaptopropionate) and 3.84 g of butenyl glycidyl ether, dissolve them in 80 mL of ethanol respectively, and place them in a round-bottom flask. Under the protection of nitrogen and in an ice-water bath, irradiate the round-bottom flask with a UV lamp with a wavelength of 365 nm. Gradually add the trimethylolpropane tris(3-mercaptopropionate) solution to the butenyl glycidyl ether solution and stir. After irradiating for 6 h at 0 o After the reaction is completed after C irradiation for 6 h, use a rotary evaporator to remove the solvent to obtain epoxy resin 3 with a controllable functionality containing ester groups. Example 4

[0030] Synthesis and preparation of epoxy resin 4 with a controllable functionality containing ester groups:

[0031] Accurately weigh 2.80 g of neopentyl glycol bis(3-mercaptopropionate) and 2.56 g of glycidyl acrylate, dissolve them in 40 mL of diethyl ether respectively, and place them in a round-bottom flask. Under the protection of nitrogen and in an ice-water bath, irradiate the round-bottom flask with a UV lamp with a wavelength of 365 nm. Gradually add the neopentyl glycol bis(3-mercaptopropionate) solution to the glycidyl acrylate solution and stir. After irradiating for 3 h at 10 o After the reaction is completed after C irradiation for 3 h, use a rotary evaporator to remove the solvent to obtain epoxy resin 4 with a controllable functionality containing ester groups. Example 5

[0032] Preparation of epoxy resin composite 1 with a controllable functionality containing ester groups Table 1 Epoxy resin composite 1 Epoxy resin component formulation table (100 g)

[0033] Take 10 g of the above epoxy resin 1 (0.53 eq / 100 g) and 1.7 g of m-xylenediamine, mix them evenly, remove the bubbles, transfer them to a stainless-steel mold pre-coated with a release agent, and cure at 80 o C for 2 h to obtain the degradable epoxy resin 1. Example 6

[0034] Preparation of the epoxy resin composite material 2 with controllable functionality containing ester groups Table 2 Epoxy resin composite material 2 Epoxy resin component formulation table (100 g)

[0035] Take 10 g of the above epoxy resin 2 (0.57 eq / 100 g) and 3.17 g of molten 4,4'-diaminodiphenylmethane, mix them evenly, remove the bubbles, transfer them to a stainless-steel mold pre-coated with a release agent, and cure at 80 o C for 2 h, 120 o C for 2 h, 150 o C for 4 h to obtain the degradable epoxy resin 2. Example 7

[0036] Preparation of the epoxy resin composite material 3 with controllable functionality containing ester groups Table 3 Epoxy resin composite material 3 Epoxy resin component formulation table (100 g)

[0037] Take 10 g of the above epoxy resin 3 (0.51 eq / 100 g), 2.4 g of isophorone diamine and 0.1 g of 2,4,6-tris(dimethylaminomethyl)benzene, mix them evenly, remove the bubbles, transfer them to a stainless-steel mold pre-coated with a release agent, and cure at 80 o C for 4 h, 150 o C for 1 h to obtain the degradable epoxy resin 3. Example 8

[0038] Preparation of the epoxy resin composite material 4 with controllable functionality containing ester groups Table 4 Epoxy resin composite material 4 Epoxy resin component formulation table (100 g)

[0039] Take 10 g of the above epoxy resin 4 (0.80 eq / 100 g) and 1.01 g of tetrahydrophthalic anhydride, mix them evenly, remove the bubbles, transfer them to a stainless-steel mold pre-coated with a release agent, and cure at 150 o C for 24 h to obtain the degradable epoxy resin 4.

[0040] Comparative Example 1: Epoxy resin composite of comparative example Take 10 g of E51 bisphenol A glycidyl ether epoxy resin (0.51 eq / 100g) and 3.11 g of polyetheramine D230, mix them evenly, remove the bubbles, transfer them to a stainless-steel mold pre-coated with a release agent, and cure at 80 o °C for 12 h to obtain the epoxy resin of the comparative example.

[0041] Mechanical properties of epoxy resin Table 5 Thermodynamic properties of epoxy resin Example 9

[0042] Degradation of degradable epoxy resin 1 First-step degradation: Weigh about 2 g of degradable epoxy resin 1, add 16 g of ethanolamine and 0.8 g of 2,4,6-tris(dimethylaminomethyl)phenol, ensure that the reagent completely infiltrates the epoxy resin, seal the container containing the above mixture, and place it in a constant temperature environment of 60 o °C and heat for 100 hours to carry out the preliminary degradation reaction, and separate the resin that has not been completely degraded for subsequent degradation operations; Second-step degradation: Add 1.8 g of triphenylboron and 30 mL of acetone to the preliminary degradation product, ensure that the reagent completely infiltrates the preliminary degradation product, seal the container containing the above mixture, and place it in a constant temperature environment of 30 o °C and heat for 100 hours to carry out the complete degradation reaction. After the reaction is completed, rotary evaporate the solvent to obtain the epoxy resin recovery product. Example 10

[0043] Degradation of degradable epoxy resin 2 First-step degradation: Weigh about 2 g of degradable epoxy resin 2, add 20 g of diethylenetriamine and 0.6 g of N-aminoethylpiperazine, ensure that the reagent completely infiltrates the epoxy resin, seal the container containing the above mixture, and place it in a constant temperature environment of 100 o °C and heat for 1 hour to carry out the preliminary degradation reaction, and separate the resin that has not been completely degraded for subsequent degradation operations; Second-step degradation: Add 2.8 g of zinc chloride and 30 mL of ethanol to the preliminary degradation product, ensure that the reagent completely infiltrates the preliminary degradation product, seal the container containing the above mixture, and place it in a constant temperature environment of 100 o °C and heat for 1 hour to carry out the complete degradation reaction. After the reaction is completed, rotary evaporate the solvent to obtain the epoxy resin recovery product. Example 11

[0044] Degradation of degradable epoxy resin 3 First-step degradation: Weigh approximately 2 g of degradable epoxy resin 3, add 24 g of hydroxyethyl ethylenediamine and 1.0 g of 1,8-diazabicyclo[5.4.0]undec-7-ene, ensure that the reagent completely wets the epoxy resin, seal the container containing the above mixture, and place it in an 80 o °C constant-temperature environment and heat for 72 hours to carry out the preliminary degradation reaction. Separate the resin that has not been completely degraded for subsequent degradation operations; Second-step degradation: Add 3.29 g of zinc acetate and 30 mL of isopropanol to the preliminary degradation product, ensure that the reagent completely wets the preliminary degradation product, seal the container containing the above mixture, and place it in a 65 o °C constant-temperature environment and heat for 48 hours to carry out the complete degradation reaction. After the reaction is completed, rotary evaporate the solvent to obtain the epoxy resin recovery product. Example 12

[0045] Degradation of degradable epoxy resin 4 First-step degradation: Weigh approximately 4 g of degradable epoxy resin 4, add 28 g of m-xylenediamine and 1.6 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, ensure that the reagent completely wets the epoxy resin, seal the container containing the above mixture, and place it in a 100 o °C constant-temperature environment and heat for 12 hours to carry out the preliminary degradation reaction. Separate the resin that has not been completely degraded for subsequent degradation operations; Second-step degradation: Add 3.7 g of aluminum chloride-imidazolium salt and 30 mL of acetonitrile to the preliminary degradation product, ensure that the reagent completely wets the preliminary degradation product, seal the container containing the above mixture, and place it in a 100 o °C constant-temperature environment and heat for 12 hours to carry out the complete degradation reaction. After the reaction is completed, rotary evaporate the solvent to obtain the epoxy resin recovery product.

[0046] Comparative Example 2: Degradation of the comparative example epoxy resin The degradation method of the comparative example resin refers to Example 13. The difference is that the comparative example epoxy resin could not be degraded, and only obvious swelling and fragmentation phenomena occurred in the solvent. Example 13

[0047] Recycling and utilization of the degradation product: Weigh 2 g of the above recovery product, mix it with 6 g of epichlorohydrin, and add 0.6 g of tetrabutylammonium bromide to the reaction system. Under stirring conditions, heat the reaction system to 100 o °C and react for 4 hours. After cooling to room temperature, add 50 mL of sodium hydroxide aqueous solution (1 mol / L) to the above reaction system. Under stirring conditions, heat the reaction system to 30 oC, carry out a closed-loop reaction for 1 hour. After the reaction is completed, stop stirring, cool the reaction product to room temperature, add an appropriate amount of water for washing, stir evenly and then let it stand for layer separation to remove the aqueous layer. Repeat the washing several times until the aqueous layer is neutral. After drying, rotary evaporate the excessive epichlorohydrin in the organic layer to obtain the regenerated epoxy resin.

Claims

1. A kind of epoxy resin with controllable ester group functionality, characterized in that: The general molecular structure formula of the epoxy resin is as follows: R1, R2, and R3 are one or more of an aliphatic carbon chain of C1-C 18 a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus, or silicon elements and its derivatives; R4 and R5 are one or more structures selected from a hydrogen atom, an aliphatic carbon chain having C1-C 18 , a benzene ring and its derivatives, and a heterocyclic structure containing oxygen, nitrogen, sulfur, phosphorus or silicon elements and its derivatives.

2. A method for preparing an epoxy resin with controllable ester group functionality as described in claim 1, characterized in that: The method is as follows: a thiol compound and a carbon-carbon double bond-containing epoxide undergo a click chemical reaction under the initiation of 365 nm ultraviolet light in a solvent, the reaction temperature is 0 - 20 o °C, the reaction time is 0.25 - 6 h. After completion, the solution is evaporated to dryness to obtain an epoxy resin with a controllable ester group functionality; the molar ratio of the mercapto group to the carbon-carbon double bond in the thiol compound is 1:

1.

3. The preparation method of an epoxy resin with controllable ester group functionality according to claim 2, characterized in that: The thiol compound is one of pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(3-mercaptopropionate), glycerol tri(3-mercaptopropionate), neopentyl glycol bis(3-mercaptopropionate), trimethylolethane tri(3-mercaptopropionate), polyethylene glycol bis(3-mercaptopropionate), or dipentaerythritol hexa(3-mercaptopropionate); The carbon-carbon double bond-containing epoxide is one of allyl glycidyl ether, glycidyl methacrylate, glycidyl acrylate, fluoroallyl glycidyl ether, or butenyl glycidyl ether; The solvent is at least one of toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, ether, tetrahydrofuran, chloroform, acetone, and acetonitrile; 4. A composite material containing an epoxy resin with a controllable ester group functionality prepared by the preparation method described in claim 2 or 3, characterized in that: The composite material includes an epoxy resin component, a curing agent component, a curing accelerator, and a toughening agent; the molar ratio of epoxy groups to active hydrogen in the curing agent is 1:1 - 1.2; the curing accelerator accounts for 0 wt% - 3 wt% of the composite material, and the toughening agent accounts for 0 wt% - 5 wt% of the composite material; The epoxy resin component includes an ester group-containing functionality-controllable epoxy resin and a conventional epoxy resin, and the ester group-containing functionality-controllable epoxy resin accounts for 0.1 wt% - 50 wt% of the epoxy resin component; The conventional epoxy resin accounts for 50 wt% - 99.9 wt% of the epoxy resin component; the conventional epoxy resin is one or more of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, glycerol triglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, polypropylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, alicyclic glycidyl ether, cyclohexanedimethanol diglycidyl ether, C12-C14 fatty alcohol glycidyl ether, phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, methyltetrahydrophthalic acid diglycidyl ester, endomethylenetetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, trimellitic anhydride triglycidyl ester, 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester, pyromellitic acid tetraglycidyl ester, 4,4'-diaminodiphenylmethane epoxy resin, triglycidyl p-aminophenol, tetraglycidyl m-xylenediamine, triglycidyl carbamate, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether, or triglycidyl isocyanurate; The curing agent component is an amine curing agent or an acid anhydride curing agent; The amine curing agent is one or more of 3-aminomethyl-3,5,5-trimethylcyclohexylamine, 4,4-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, methylamine, hydrogenated diaminodiphenylmethane, N-aminoethylpiperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diaminodiphenylmethane, diaminodiphenylsulfone, meta-xylylenediamine, polyetheramine, dicyandiamide, and isophoronediamine; The acid anhydride curing agent is one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, dodecenylsuccinic anhydride, maleic anhydride, pyromellitic anhydride, chlorobridged anhydride, polyazelaic anhydride, endomethylenetetrahydrophthalic anhydride, and benzophenonetetracarboxylic anhydride; The curing accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)benzene, 1,8-diazabicyclo(5,4,0)-7-undecene, benzyldimethylamine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-mercaptobenzothiazole, and acetylacetone metal salt; The toughening agent is one or more of inorganic nanoparticles, polyether polyols, polysulfide rubber, and PU prepolymer.

5. A method for preparing the epoxy resin composite containing ester group with controllable functionality as described in claim 4, characterized in that: Take various raw materials according to the raw material content and mix them, set the temperature to room temperature - 200 o °C, and the curing time is 2 - 24 h.

6. A low-temperature recovery method for the ester group functionality controllable epoxy resin composite material according to claim 4, characterized in that: The method is: Step 1: Immerse the composite material casting into the catalytic degradation solution and conduct a catalytic bond-breaking reaction for 1 to 100 hours within the temperature range of 60 - 100 o °C to obtain a solid-liquid mixture; Step 2: Immerse the incompletely degraded product from Step 1 in an organic solvent containing a Lewis acid catalyst, and carry out catalytic bond cleavage within the temperature range of 30-100 o °C, assisted by microwave treatment, and react for 1-100 hours to obtain a degradation mixed solution. The degradation mixed solution is separated by vacuum distillation to obtain a recovered organic solvent and a recovered resin product.

7. A method for low-temperature recovery of an epoxy resin composite material with controllable ester group functionality according to claim 6, characterized in that: In step 1, the catalytic degradation liquid includes an amine compound, an alcohol compound, a mixture of one or more of an alcoholamine compound and an alkaline catalyst; The mass proportion of the alkaline catalyst is 0.1-10%, and the mass proportion of other compounds is 90-99.9%; The amine compound is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, butanediamine, hexamethylenediamine, isophoronediamine, oleylamine, isopropylamine, tert-butylamine, benzylamine, cyclohexylamine, acrylamine and pyrrolidineamine; The alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, cyclohexanol, glycerol, ethylene glycol, propylene glycol, butanediol, pentanediol, pentaerythritol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, polytetrahydrofuran diol, polypropylene glycol, castor oil-based diol, and polycarbonate diol; The alcoholamine compound is one or more of ethanolamine, diethanolamine, isopropanolamine, aminomethylpropanol, hydroxyethylethylenediamine, diglycolamine, 1-amino-2-propanol, 1-amino-2-butanol, phenylethanolamine, 2-amino-2-methyl-1-propanol, and 2-amino-1-butanol; The alkaline catalyst is one or more of modified products of 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diaza-bicyclo(5,4,0)-7-undecene, N-aminoethylpiperazine, and 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

8. A method for low-temperature recovery of an epoxy resin composite material with controllable ester group functionality according to claim 6, characterized in that: In step 2, the mass proportion of the Lewis acid catalyst is 0.1wt%-10wt%, and the mass proportion of the organic solvent is 90wt%-99.9wt%; The Lewis acid catalyst is one or more of aluminum trichloride, iron trichloride, titanium tetrachloride, boron trifluoride, boron trichloride, zinc chloride, zinc acetate, trimethylaluminum, diethylzinc, triphenylboron, scandium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, aluminum chloride-imidazolium salt; The organic solvent is at least one of isopentane, n-pentane, petroleum ether, hexane, cyclohexane, benzene, toluene, dichloromethane, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, ether, tetrahydrofuran, chloroform, dioxane, acetone, acetonitrile.

9. A method for recycling a recycled resin product obtained by the method according to any one of claims 6 to 8, characterized in that: The method is as follows: Take the hydroxyl-terminated recycled resin product and epichlorohydrin and mix them in a molar ratio of 1:1.5 - 2. Add a phase transfer catalyst to the reaction system, with the dosage being 0.1 - 5% of the mass of the recycled resin product. Under stirring conditions, heat the reaction system to 30 - 100 o °C, and the reaction time is 1 - 10 hours. Add an alkaline solution to the above reaction system. The mass concentration of the alkaline solution is 60 - 100%, and the dosage is 1 - 5 times the molar amount of the recycled resin product. Under stirring conditions, heat the reaction system to 30 - 100 o °C to carry out a ring-closing reaction, and the reaction time is 1 - 10 hours. After the reaction is completed, stop stirring, cool the reaction product to room temperature, add an appropriate amount of water for washing, stir evenly and then let it stand for stratification. Remove the water layer, repeat the washing several times until the water layer is neutral. After drying, rotary evaporate the excess epichlorohydrin in the organic layer to obtain the regenerated epoxy resin.

10. The method according to claim 9, wherein: The phase transfer catalyst is one of tetrabutylammonium bromide, tetraethylammonium bromide, benzyltriethylammonium chloride, cetyltrimethylammonium bromide, tetraphenylphosphonium bromide, ethyltriphenylphosphonium bromide, etc.

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