Functional amine curing agent and vacuum infusion epoxy resin composite preparation and low temperature recovery method

Abstract

A functional amine curing agent and a method for preparing and recycling a vacuum infusion epoxy resin composite. The composite uses a functional amine curing agent containing easily degradable ester groups, which can be degraded under mild conditions after curing with epoxy resin. The matching low-temperature recycling method uses a two-step catalytic degradation process: the first step uses a Lewis acid catalyst to break the C-N bond; the second step uses amine, alcohol or alcohol amine compounds and alkaline catalyst to break the ester group, achieving complete degradation at 100 DEG C or below under normal pressure. The degradation products can be directly reused as curing agents, toughening agents or chain extenders. The present application significantly reduces the environmental burden of traditional epoxy resin which is difficult to degrade without changing the existing molding process, and has good environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of polymer compounds, specifically the field of epoxy resin technology, and relates to a method for preparing and recovering a functional amine curing agent and a vacuum-infused epoxy resin composite material at low temperature. Background Technology

[0002] With the increasing global demand for clean energy, wind power, as an important renewable energy technology, has developed rapidly. Wind turbine blades, as one of the core components of wind power systems, play a crucial role in the efficiency and economics of wind power generation due to their performance and lifespan. Currently, wind turbine blades are mainly manufactured using vacuum infusion technology, which is widely used due to its high efficiency and high quality. However, as a large number of wind turbine blades gradually reach the end of their service life and are decommissioned, how to dispose of these decommissioned blades has become an urgent environmental and resource problem. In the manufacturing process of wind turbine blades, vacuum-infused epoxy resin is one of the key materials, used in large quantities and playing a decisive role in the blade's performance. Traditional vacuum-infused epoxy resins mainly use aliphatic amines and cycloaliphatic amines as curing agents. The large C-C and CN bond energies in these curing agents pose significant challenges to the degradation and recycling of the cured epoxy resin. CN106832767A discloses a biodegradable epoxy resin composition for fiber-reinforced vacuum infusion, its preparation method, and its recycling method. It uses biodegradable aliphatic amine curing agent ACV-1001, biodegradable alicyclic amine curing agent ACV-1005, alicyclic epoxy resin TTA21, and accelerator benzyl alcohol as curing agent components. However, the degradation method uses strong acid, which can easily cause secondary pollution to the environment. CN119684573A discloses a high-strength insulating Schiff base biodegradable epoxy resin material and its preparation method. Although the Schiff base exchange mechanism can be used to degrade it with amines, the synthesis is difficult and the raw material cost is high. In the prior art, although there are patent reports on the synthesis methods of amine curing agents containing dynamic bonds, these curing agents are expensive and have poor processability, making them difficult to apply in large-scale industrial production. For example, imine dynamic bonds (C=N) result in mostly solid products. Mixing solid curing agents with epoxy resin is difficult and requires solvents. Solvents increase process complexity and easily cause defects in the cured product. In addition, existing degradation methods usually require high temperature or strong acid and alkali conditions, which not only increases recycling costs but also limits the recycling efficiency of composite materials, making it difficult to meet the requirements of sustainable development. Summary of the Invention

[0003] The purpose of this invention is to solve the problems of difficult degradation, high cost, and easy secondary pollution of existing vacuum-infused epoxy resins used in wind turbine blades. It provides a method for preparing and low-temperature recycling a functional amine curing agent and a vacuum-infused epoxy resin composite material, which simultaneously meets the requirements of wind turbine blade manufacturing for low viscosity, long service life and high performance of epoxy resin.

[0004] The composite material of this invention meets the requirements of low viscosity, long service life, and high performance of vacuum-infused epoxy resin for wind turbine blades. Through optimized formulation design and innovative degradation methods, it achieves highly efficient degradation of the cured epoxy resin. This invention employs a two-step catalytic degradation method, enabling complete degradation of the cured epoxy resin at atmospheric pressure and below 100°C. This significantly reduces energy consumption and costs during the recycling process, providing an efficient, economical, and environmentally friendly solution for the sustainable recycling of wind turbine blades.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A functional amine curing agent, wherein the curing agent has the following general molecular structural formula:

[0007]

[0008] Where R1-R3 is C1-C 18 The structure includes one or more of the following: aliphatic carbon chains, benzene rings and their derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus or silicon; R4-R6 are hydrogen atoms, C1-C 18 It includes one or more of the following: aliphatic carbon chains, benzene rings and their derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus or silicon.

[0009] A method for preparing the above-mentioned functional amine curing agent, wherein the method comprises: reacting a thiol compound and an unsaturated amine in a solvent with an initiator under heating conditions to undergo a click chemical reaction at a temperature of 0-100℃ for a reaction time of 0.25-12 h; after the reaction is completed, the solution is evaporated to dryness to obtain the functional amine curing agent; in the reactants, the molar ratio of the mercapto group in the thiol compound to the carbon-carbon double bond in the unsaturated amine is 1:1, and the mass ratio of the unsaturated amine to the initiator is 100:0.5-1. The relevant chemical equations are as follows:

[0010]

[0011] Furthermore, in the thiol compound, R1 and R2 are C1-C6. 18The structure comprises one or more of the following: aliphatic carbon chains, benzene rings and their derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus or silicon elements; preferably, one or more of the following: pentaerythritol tetra(3-mercaptopropionate), bispentaerythritol hexa(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), bis(3-mercaptopropionic acid) ethylene glycol, polyethylene glycol di(3-mercaptopropionate), polypropylene glycol di(3-mercaptopropionate), terephthalate di(2-mercaptoethyl terephthalate), glycerol tri(3-mercaptopropionate) or adipate di(2-mercaptoethyl terephthalate);

[0012] In the unsaturated amine, R3 is C1-C. 18 The structure includes one or more of the following: aliphatic carbon chains, benzene rings and their derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus or silicon; R4-R6 are hydrogen atoms, C1-C 18 The structure comprises one or more of the following: aliphatic carbon chains, benzene rings and their derivatives, and heterocyclic structures and their derivatives containing oxygen, nitrogen, sulfur, phosphorus or silicon elements; preferably, allylamine, N-methylallylamine, diallylamine, acrylamide, N-isopropylacrylamide, p-aminostyrene, cinnamylamine, N-methylcinnamylamine, 3-cyclohexene-1-amine, 2-aminonorbornene or 1-amino-1,3-butadiene;

[0013] The solvent is at least one selected from toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, diethyl ether, tetrahydrofuran, chloroform, acetone, and acetonitrile.

[0014] The initiator is one of the following: peroxide initiator (benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxide, tert-butyl peroxybenzoate, diisopropyl peroxide, dicyclohexyl peroxide, etc.), azo initiator (azobisisobutyronitrile, azobisisoheptanenitrile, etc.), or persulfate initiator (potassium persulfate, sodium persulfate, ammonium persulfate, etc.).

[0015] A biodegradable vacuum-infused epoxy resin composite for wind turbine blades containing a functional amine curing agent prepared by the above-mentioned preparation method is characterized in that: the composite comprises a curing agent component, an epoxy resin 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 0wt%-5wt% of the epoxy resin composite; and the toughening agent accounts for 0wt%-20wt% of the epoxy resin composite.

[0016] Further, the curing agent component includes a functional amine curing agent and an epoxy resin amine curing agent, wherein the functional amine curing agent accounts for 0.1wt%-50wt% of the curing agent component, and the epoxy resin amine curing agent accounts for 50wt%-99.9wt% of the curing agent component; the epoxy resin amine curing agent is one or more selected from isophorone diamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, alkyl diamine, hydrogenated diaminodiphenylmethane, N-aminoethylpiperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diaminodiphenyl sulfone, m-phenylenediamine, polyetheramine, and dicyandiamide;

[0017] The epoxy resin components include glycidyl ether epoxy resin, glycidyl amine epoxy resin, and glycidyl ester epoxy resin, wherein the glycidyl ether epoxy resin accounts for 0wt%-60wt% of the epoxy resin components; the glycidyl amine epoxy resin accounts for 0wt%-60wt% of the epoxy resin components; and the glycidyl ester epoxy resin accounts for 40wt%-100wt% of the epoxy resin components.

[0018] The glycidyl ether epoxy resin is one or more of the following: bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, hydrogenated bisphenol A epoxy resin, linear phenolic epoxy resin, o-cresol formaldehyde epoxy resin, 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, resorcinol diglycidyl ether, naphthol formaldehyde epoxy resin, biphenyl diglycidyl ether, alicyclic glycidyl ether, cyclohexanediol diglycidyl ether, and C12-C14 fatty alcohol glycidyl ether.

[0019] The glycidylamine epoxy resin is one or more of the following: 4,4'-diaminodiphenylmethane epoxy resin, triglycidyl-p-aminophenol, tetraglycidyl-m-phenylenediamine, triglycidyl carbamate, N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenyl ether, and triglycidyl triisocyanate.

[0020] The glycidyl ester epoxy resin is one or more of the following: diglycidyl phthalate, hexahydrodiglycidyl phthalate, diglycidyl terephthalate, diglycidyl isophthalate, diglycidyl tetrahydrophthalate, diglycidyl methyltetrahydrophthalate, diglycidyl methylmethylenetetrahydrophthalate, diglycidyl adipate, triglycidyl trimellitate, tetraglycidyl pyromellitic acid, and soybean oil-based glycidyl ester.

[0021] The curing accelerator is one or more of the following: 2,4,6-tris(dimethylaminomethyl)benzene, 1,8-diazabicyclo(5,4,0)-7-undecene, benzyl dimethylamine, 1,5,7-trizabicyclo[4.4.0]dec-5-ene, 2-ethyl-4-methylimidazolium, 1-cyanoethyl-2-ethyl-4-methylimidazolium, 2-mercaptobenzothiazole, and metal salts of acetylacetone;

[0022] The toughening agent is one or more of inorganic nanoparticles, polyether polyols, polysulfide rubber, and PU prepolymers.

[0023] Furthermore, the composite material also includes reinforcing bodies and auxiliary materials;

[0024] The reinforcement is at least one of carbon fiber, glass fiber, natural fiber, chemical fiber and fabrics made of fiber materials, carbon nanomaterials, boron nitride nanomaterials, metal nanoparticles, metal oxide nanoparticles, and organic nanoparticles, accounting for 50wt%-65wt% of the total mass of the composite material;

[0025] The auxiliary materials are at least one of the following: accelerator, diluent, plasticizer, toughening agent, thickener, coupling agent, defoamer, leveling agent, ultraviolet absorber, antioxidant, brightener, fluorescent reagent, pigment, and filler, accounting for 0.1wt%-2wt% of the total mass of the composite material.

[0026] A method for preparing the above-mentioned vacuum-infused epoxy resin composite material, wherein the method comprises: taking various raw materials according to their content and mixing them, heating to 25-180℃ and holding for curing for 2-24 hours.

[0027] A method for low-temperature recovery of the above-mentioned vacuum-infused epoxy resin composite, wherein the method comprises:

[0028] Step 1: The biodegradable wind turbine blade is immersed in an organic solvent containing a Lewis acid catalyst using vacuum-infused epoxy resin composite material, and a catalytic bond-breaking reaction is carried out at 30-100℃ for 1-100 hours to obtain a degradation mixture solution; the degradation mixture solution is subjected to vacuum distillation to separate the recovered organic solvent and the recovered resin product.

[0029] Step 2: Immerse the recycled resin product obtained in Step 1 into the catalytic degradation solution and carry out the catalytic bond breaking reaction at 30-100℃ for 1-100h to obtain the final degradation mixture solution and the oligomer with terminal amino groups.

[0030] Further, in step one, the Lewis acid catalyst is one or more selected from aluminum trichloride, ferric trichloride, titanium tetrachloride, boron trifluoride, boron trichloride, zinc chloride, trimethylaluminum, diethylzinc, triphenylboron, scandium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, and aluminum chloride-imidazolium salt; the organic solvent is at least one selected from isopentane, n-pentane, petroleum ether, hexane, cyclohexane, benzene, toluene, dichloromethane, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, diethyl ether, petroleum ether, tetrahydrofuran, chloroform, dioxane, acetone, and acetonitrile; the mass percentage of the Lewis acid catalyst is 0.1-10%, and the mass percentage of the organic solvent is 90-99.9%.

[0031] Furthermore, in step two, the catalytic degradation liquid includes one or more of amine compounds, alcohol compounds, and alkaline amine compounds, as well as an alkaline catalyst.

[0032] The alkaline catalyst accounts for 0.1-10% of the total mass, while other compounds account for 90-99.9% of the total mass.

[0033] The amine compound is one or more selected from ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, butanediamine, hexanediamine, isophoronediamine, oleylamine, isopropylamine, tert-butylamine, benzylamine, cyclohexylamine, acrylamine, and pyrrolidineamine.

[0034] The alcohol compounds are one or more selected from methanol, ethanol, isopropanol, butanol, cyclohexanol, glycerol, ethylene glycol, propylene glycol, butanediol, pentanediol, pentaerythritol, 1,4-cyclohexanediethanol, tricyclodecanediethanol, polytetrahydrofurandiol, polypropylene glycol, castor oil-based diol, and polycarbonate diol.

[0035] The alkanolamine compound is one or more selected from ethanolamine, diethanolamine, isopropanolamine, aminomethylpropanol, hydroxyethyl ethylenediamine, diethylene glycolamine, 1-amino-2-propanol, 1-amino-2-butanol, phenylethanolamine, 2-amino-2-methyl-1-propanol, and 2-amino-1-butanol.

[0036] The alkaline catalyst is one or more of the following: 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diaza-bicyclo(5,4,0)-7-undecene, N-aminoethylpiperazine, and modified 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0037] A method for degrading a vacuum-infused epoxy resin composite material (including reinforcement and auxiliary materials) for wind turbine blades, the method comprising:

[0038] Step 1: The biodegradable wind turbine blade is immersed in an organic solvent containing a Lewis acid catalyst using vacuum-infused epoxy resin composite material, and a catalytic bond-breaking reaction is carried out at 30-100℃ for 1-100 hours to obtain a degradation mixture solution; the degradation mixture solution is subjected to vacuum distillation to separate the recovered organic solvent, recovered resin product and reinforcing fiber.

[0039] The Lewis acid catalyst comprises 0.1-10% by mass, and the organic solvent comprises 90-99.9% by mass.

[0040] The Lewis acid catalyst is one or more of the following: aluminum trichloride, ferric trichloride, titanium tetrachloride, boron trifluoride, boron trichloride, zinc chloride, trimethylaluminum, diethylzinc, triphenylboron, scandium trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, and aluminum chloride-imidazolium salt.

[0041] The solvent is at least one of isopentane, n-pentane, petroleum ether, hexane, cyclohexane, benzene, toluene, dichloromethane, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, tert-butanol, diethyl ether, petroleum ether, tetrahydrofuran, chloroform, dioxane, acetone, and acetonitrile.

[0042] Step 2: Add the recycled resin product obtained in Step 1 to the catalytic degradation solution and carry out the catalytic bond breaking reaction at 30-100℃ for 1-100h to obtain the final degradation mixture solution.

[0043] The catalytic degradation liquid includes one or more of amine compounds, alcohol compounds, and alkaline amine compounds, as well as an alkaline catalyst.

[0044] The alkaline catalyst accounts for 0.1-10% of the total mass, while other compounds account for 90-99.9% of the total mass.

[0045] The amine compound is one or more of the following: ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, butanediamine, hexanediamine, isophoronediamine, oleylamine, isopropylamine, tert-butylamine, benzylamine, cyclohexylamine, acrylamine, and pyrrolidineamine.

[0046] The alcohol compounds are one or more selected from methanol, ethanol, isopropanol, butanol, cyclohexanol, glycerol, ethylene glycol, propylene glycol, butanediol, pentanediol, pentaerythritol, 1,4-cyclohexanediethanol, tricyclodecanediethanol, polytetrahydrofurandiol, polypropylene glycol, castor oil-based diol, and polycarbonate diol.

[0047] The alkanolamine compound is one or more of the following: ethanolamine, diethanolamine, isopropanolamine, aminomethylpropanol, hydroxyethyl ethylenediamine, diethylene glycolamine, 1-amino-2-propanol, 1-amino-2-butanol, phenylethanolamine, 2-amino-2-methyl-1-propanol, and 2-amino-1-butanol.

[0048] The alkaline catalyst is one or more of the following: 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diaza-bicyclo(5,4,0)-7-undecene, N-aminoethylpiperazine, and modified 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

[0049] The advantages of this invention over the prior art are as follows:

[0050] (1) The present invention utilizes click chemistry to prepare ester-containing functional amine curing agents, which has advantages such as definite structure, high yield and low cost. The curing activity of the functional amine curing agents is consistent with that of the currently used aliphatic amines and alicyclic amines. It can be cured to obtain castings and composite materials that meet the performance requirements without changing the existing vacuum injection molding process.

[0051] (2) After the functional amine curing agent reacts with the epoxy resin, the introduced ester group can dissociate under the action of amine compounds, alcohol compounds and alkanolamine compounds, thus giving it degradation and recycling properties.

[0052] (3) The low-temperature recycling method provided by the present invention adopts a two-step catalytic degradation method. The first step uses Lewis acid to catalyze the breaking of CN bonds, and the second step uses alkali to catalyze the breaking of ester groups, thereby reducing the degradation temperature under normal pressure to below 100°C. The degradation process is green and there is no waste discharge. The recycled reinforcing material can be reused after separation, washing and drying. The final resin degradation product can be used as a curing agent, toughening agent and chain extender. Detailed Implementation

[0053] The technical solution of the present invention will be further described below with reference to the embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention. Example 1:

[0054] Synthesis and preparation of functional amine curing agent 1:

[0055]

[0056] Accurately weigh 3.81 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester and dissolve it in 50 mL of ethanol in a round-bottom flask. Weigh 2.28 g of allylamine and 0.02 g of azobisisobutyronitrile and dissolve them in 50 mL of ethanol. Under nitrogen protection, gradually add the allylamine solution to the pentaerythritol tetrakis(3-mercaptopropionic acid) ester solution and stir. React at 100 °C for 15 min. Remove the solvent using a rotary evaporator to obtain functional amine curing agent 1. Example 2:

[0057] Synthesis and preparation of functional amine curing agent 2:

[0058]

[0059] Accurately weigh 2.38 g of bis(3-mercaptopropionic acid) ethylene glycol and dissolve it in 50 mL of dichloromethane in a round-bottom flask. Weigh 1.94 g of 3-cyclohexene-1-amine and 0.02 g of azobisisobutyronitrile and dissolve them in 50 mL of dichloromethane. Under nitrogen protection, gradually add the 3-cyclohexene-1-amine solution to the bis(3-mercaptopropionic acid) ethylene glycol solution and stir. React at 40 °C for 12 h. Remove the solvent using a rotary evaporator to obtain functional amine curing agent 2. Example 3:

[0060] Synthesis and preparation of functional amine curing agent 3:

[0061]

[0062] Accurately weigh 3.81 g of trimethylolpropane tris(3-mercaptopropionate) and dissolve it in 50 mL of isopropanol in a round-bottom flask. Weigh 3.57 g of p-aminostyrene and 0.06 g of potassium persulfate and dissolve them in 50 mL of isopropanol. Under nitrogen protection, gradually add the p-aminostyrene solution to the trimethylolpropane tris(3-mercaptopropionate) solution and stir. React at 60 °C for 6 h. Remove the solvent using a rotary evaporator to obtain functional amine curing agent 3. Example 4:

[0063] Synthesis and preparation of functional amine curing agent 4:

[0064]

[0065] Accurately weigh 3.99 g of pentaerythritol tetrakis(3-mercaptopropionic acid) ester and dissolve it in 50 mL of chloroform. Place the solution in a round-bottom flask. Weigh 2.84 g of N-methylallylamine and 0.04 g of benzoyl peroxide and dissolve them in 50 mL of chloroform. Under nitrogen protection, gradually add the N-methylallylamine solution to the pentaerythritol tetrakis(3-mercaptopropionic acid) ester solution and stir. React at 80 °C for 4 h. Remove the solvent using a rotary evaporator to obtain functional amine curing agent 4. Example 5:

[0066] Preparation of epoxy resin system material 1 containing functional amine curing agent 1

[0067] Table 1. Ingredient list for epoxy resin system material 1

[0068]

[0069] Take the above system material, stir it evenly to remove air bubbles, transfer it to a stainless steel mold pre-coated with release agent, cure at 80℃ for 2 hours, at 120℃ for 2 hours, and at 150℃ for 4 hours to obtain epoxy resin 1. Example 6:

[0070] Preparation of epoxy resin system material 2 containing functional amine curing agent 2

[0071] Table 2. Ingredient list for epoxy resin system material 2

[0072]

[0073] Take the above system material, stir it evenly to remove air bubbles, transfer it to a stainless steel mold pre-coated with release agent, and cure it at room temperature for 24 hours to obtain epoxy resin 2. Example 7:

[0074] Preparation of epoxy resin system material 3 containing functional amine curing agent 3

[0075] Table 3. Ingredient list for epoxy resin system material 3

[0076]

[0077] Take the above system material, stir it evenly to remove air bubbles, transfer it to a stainless steel mold pre-coated with release agent, and cure it at 150℃ for 2 hours to obtain epoxy resin 3. Example 8:

[0078] Preparation of epoxy resin system material 4 containing functional amine curing agent 4

[0079] Table 4. Ingredient List for Epoxy Resin System Material 4

[0080]

[0081] Take the above system material, stir it evenly to remove air bubbles, transfer it to a stainless steel mold pre-coated with release agent, and cure it at 120℃ for 8 hours to obtain epoxy resin 4.

[0082] Comparative Example 1:

[0083] Comparative Epoxy Resin System Materials

[0084] Take 10 g of E51 bisphenol A glycidyl ether epoxy resin (0.51 eq / 100g) and 3.11 g of triethylenetetramine, mix them, remove air bubbles after stirring, transfer the mixture to a stainless steel mold pre-coated with a release agent, and cure at room temperature for 12 hours to obtain the comparative epoxy resin.

[0085] Mechanical properties of epoxy resin

[0086] Table 5 Thermodynamic properties of epoxy resins

[0087] Example 9:

[0088] Degradation of epoxy resin 1:

[0089] The first step of degradation involves dissolving 2.5 g of ferric chloride in 50 mL of ethanol to form a homogeneous degradation solution. Approximately 3 g of epoxy resin 1 is weighed and completely immersed in the degradation solution, ensuring full contact between the resin and the solution. The container containing the degradation solution and epoxy resin is sealed and heated at a constant temperature of 70°C for 12 hours to allow for initial degradation of the resin. After the reaction is complete, the initial degradation product is separated by filtration and set aside for later use.

[0090] In the second step of degradation, 20 g of diethylenetriamine and 0.8 g of 2,4,6-tris(dimethylaminomethyl)phenol were added to the preliminary degradation product to ensure complete impregnation and uniform mixing of all components. The container containing the mixture was sealed and heated in a constant temperature environment of 80°C for 12 hours to allow the resin to degrade completely, yielding a yellowish-brown viscous liquid. Example 10:

[0091] Degradation of epoxy resin 2:

[0092] The first step of degradation involves dissolving 2.8 g of zinc chloride in 40 mL of methanol to form a homogeneous degradation solution. Approximately 2 g of epoxy resin 2 is weighed and completely immersed in the degradation solution, ensuring full contact between the resin and the solution. The container containing the degradation solution and epoxy resin is sealed and heated at a constant temperature of 100°C for 2 hours to allow for initial degradation of the resin. After the reaction is complete, the initial degradation product is separated by filtration and set aside for later use.

[0093] In the second step of degradation, 36 g of tetraethylenepentamine and 0.6 g of N-aminoethylpiperazine were added to the preliminary degradation product to ensure complete impregnation and uniform mixing of all components. The container containing the mixture was sealed and heated in a constant temperature environment of 40°C for 100 hours to allow the resin to degrade completely, yielding a yellowish-brown viscous liquid. Example 11:

[0094] Degradation of epoxy resin 3:

[0095] The first step of degradation involved dissolving 4.2 g of ytterbium trifluoromethanesulfonate in 60 mL of chloroform to form a homogeneous degradation solution. Approximately 2.6 g of epoxy resin 3 was weighed and completely immersed in the degradation solution, ensuring full contact between the resin and the solution. The container containing the degradation solution and epoxy resin was sealed and heated at a constant temperature of 40°C for 100 hours to allow for initial degradation of the resin. After the reaction was complete, the initial degradation products were separated by filtration and set aside for later use.

[0096] In the second step of degradation, 18 g of ethanolamine and 1.2 g of 1,8-diaza-bicyclo(5,4,0)-7-undecene were added to the preliminary degradation product to ensure complete impregnation and uniform mixing of all components. The container containing the mixture was sealed and heated at a constant temperature of 100°C for 1 hour to allow complete degradation of the resin, yielding a yellow viscous liquid. Example 12:

[0097] Degradation of epoxy resin 4:

[0098] The first step of degradation involved dissolving 2.2 g of boron trichloride in 50 mL of acetone to form a homogeneous degradation solution. Approximately 1.6 g of epoxy resin 4 was weighed and completely immersed in the degradation solution, ensuring full contact between the resin and the solution. The container containing the degradation solution and epoxy resin was sealed and heated at a constant temperature of 80°C for 12 hours to allow for initial degradation of the resin. After the reaction was complete, the initial degradation products were separated by filtration and set aside for later use.

[0099] In the second step of degradation, 22 g of aminomethylpropanol and 1.1 g of 1,5,7-triazabicyclo[4.4.0]dec-5-ene were added to the above preliminary degradation product to ensure complete impregnation and uniform mixing of all components. The container containing the above mixture was sealed and heated in a constant temperature environment of 80°C for 4 hours to allow the resin to degrade completely, yielding a brownish-yellow viscous liquid.

[0100] Comparative Example 2:

[0101] Comparative degradation of epoxy resin

[0102] The degradation method of the comparative resin is the same as that in Example 9, except that the comparative epoxy resin failed to degrade and only showed obvious swelling and fragmentation in the solvent. Example 13:

[0103] Reuse of degradation products:

[0104] The resin degradation solution obtained above was added as a toughening agent to the new epoxy resin. 10 g of E-51 epoxy resin, 10 g of diglycidyl tetrahydrophthalate, 2.92 g of resin degradation product and 2.81 g of isophorone diamine were accurately weighed, stirred and mixed, and after vacuum degassing, poured into a metal mold and cured at 80°C for 6 h to obtain the recured epoxy resin casting.

[0105] Table 6 Thermodynamic properties of recured epoxy resin castings

[0106]

Claims

1. A process for the low temperature recovery of vacuum infused epoxy resin composites, characterized by: The composite material comprises a curing agent component, an epoxy resin 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 0wt%-5wt% of the epoxy resin composite material; the toughening agent accounts for 0wt%-20wt% of the epoxy resin composite material; the curing agent component comprises a functional amine curing agent and an epoxy resin amine curing agent, the functional amine curing agent is one of 、 、 、 The low-temperature recovery method is: Step one: immerse the degradable vacuum infusion epoxy resin composite material for wind power blades in an organic solvent containing a Lewis acid catalyst, and perform a catalytic bond breaking reaction at 30-100 DEG C for 1-100 h to obtain a degradation mixed solution; perform vacuum distillation on the degradation mixed solution to separate and obtain a recovered organic solvent and a recovered resin product; the Lewis acid catalyst is one or more of aluminum chloride, iron trichloride, titanium tetrachloride, boron trifluoride, boron trichloride, zinc chloride, trimethylaluminum, diethylzinc, triphenylboron, scandium triflate, ytterbium triflate, 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, diethyl ether, petroleum ether, tetrahydrofuran, chloroform, dioxane, acetone, and acetonitrile; the mass ratio of the Lewis acid catalyst is 0.1-10%, and the mass ratio of the organic solvent is 90-99.9%; Step two: immerse the recovered resin product obtained in step one in a catalytic degradation solution, and perform a catalytic bond breaking reaction at 30-100 DEG C for 1-100 h to obtain a final degradation mixed solution; the catalytic degradation solution comprises a mixture of one or more of amine compounds, alcohol compounds, and alcohol amine compounds, and an alkaline catalyst; The mass ratio of the alkaline catalyst is 0.1-10%, and the mass ratio of the other compounds is 90-99.9%; The amine compound is one or more of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, butanediamine, hexanediamine, isophorone diamine, oleylamine, isopropylamine, tert-butylamine, benzylamine, cyclohexylamine, propylene amine, and pyrrolidine amine; The alcohol compound is one or more of methanol, ethanol, isopropanol, butanol, cyclohexanol, glycerol, ethylene glycol, propylene glycol, butanediol, pentanediol, pentaerythritol, 1,4-cyclohexane dimethanol, tricyclodecane dimethanol, polytetrahydrofuran diol, polypropylene glycol, ricin oil-based diol, and polycarbonate diol; The alcohol amine compound is one or more of ethanolamine, diethanolamine, isopropanolamine, aminomethylpropanol, hydroxyethyl ethylenediamine, diethylene glycol amine, 1-amino-2-propanol, 1-amino-2-butanol, phenethylamine, 2-amino-2-methyl-1-propanol, and 2-amino-1-butanol. The basic catalyst is one or more of 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)-7-undecene, N-aminoethylpiperazine, and a modified product of 1,5,7-triazabicyclo[4.4.0]dec-5-ene.

2. The method according to claim 1, wherein the method is characterized by: The functional amine curing agent is prepared by a method comprising the following steps: under the condition of heating, a thiol compound and an unsaturated amine are subjected to a click chemistry reaction in a solvent, using an initiator, the reaction temperature is 0-100 DEG C, the reaction time is 0.25-12 h, and after the reaction is completed, the solution is evaporated to dryness to obtain the functional amine curing agent; in the reactants, the molar ratio of the mercapto group in the thiol compound to the carbon-carbon double bond in the unsaturated amine is 1:1, and the mass ratio of the unsaturated amine to the initiator is 100:0.5-1; The thiol compound is one or more of bis(3-mercaptopropionic acid) ethylene glycol, trimethylolpropane tri(3-mercaptopropionate), and pentaerythritol tetra(3-mercaptopropionate). The unsaturated amine is one or more of allylamine, 3-cyclohexene-1-amine, p-aminostyrene, and N-methylallylamine.

3. The low-temperature recovery method for vacuum-infused epoxy resin composites according to claim 2, characterized in that: The solvent is at least one of toluene, xylene, dichloromethane, methanol, ethanol, ethylene glycol, propanol, isopropanol, ethyl acetate, diethyl ether, tetrahydrofuran, chloroform, acetone, and acetonitrile; and the initiator is one of a peroxide initiator, an azo initiator, and a persulfate salt.

4. The method of claim 1, wherein the method comprises the following steps: a vacuum pump is used to pump the air in the vacuum chamber to a pressure of 0.01-0.1 MPa; the vacuum chamber is heated to a temperature of 50-100 DEG C; the vacuum chamber is cooled to a temperature of 0-10 DEG C; and the vacuum chamber is opened. The curing agent component comprises a functional amine curing agent and an epoxy resin amine curing agent, the functional amine curing agent accounts for 0.1wt%-50wt% of the curing agent component, and the epoxy resin amine curing agent accounts for 50wt%-99.9wt% of the curing agent component; the epoxy resin amine curing agent is one or more of isophorone diamine, 4,4'-diaminodicyclohexylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, diphenylamine, hydrogenated diaminodiphenylmethane, N-aminoethylpiperazine, ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diaminodiphenyl sulfone, m-xylylenediamine, polyether amine, and dicyandiamide; The epoxy resin component comprises a glycidyl ether epoxy resin, a glycidyl amine epoxy resin, and a glycidyl ester epoxy resin, the glycidyl ether epoxy resin accounts for 0wt%-60wt% of the epoxy resin component, the glycidyl amine epoxy resin accounts for 0wt%-60wt% of the epoxy resin component, and the glycidyl ester epoxy resin accounts for 40wt%-100wt% of the epoxy resin component. The glycidyl ether epoxy resin is one or more of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, tetrabromobisphenol A diglycidyl ether, hydrogenated bisphenol A epoxy resin, linear phenolic epoxy resin, o-cresol formaldehyde epoxy resin, 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, resorcinol diglycidyl ether, naphthol formaldehyde epoxy resin, diphenyl diglycidyl ether, alicyclic glycidyl ether, cyclohexane dimethanol diglycidyl ether, C12-C14 fatty alcohol glycidyl ether; The glycidyl amine epoxy resin is one or more of 4,4'-diaminodiphenylmethane epoxy resin, trisglycidyl-p-aminophenol, tetraglycidyl-m-xylylenediamine, trisglycidyl carbamate, N,N,N',N'-tetraglycidyl-4,4'-oxydianiline, trimeric isocyanuric acid tri-glycidyl ester; The glycidyl ester epoxy resin is one or more of phthalic acid diglycidyl ester, hexahydrophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, methyltetrahydrophthalic acid diglycidyl ester, end methylene tetrahydrophthalic acid diglycidyl ester, adipic acid diglycidyl ester, trimellitic acid triglycidyl ester, pyromellitic acid tetraglycidyl ester, soybean oil glycidyl ester; The curing accelerator is one or more of 2,4,6-tris(dimethylaminomethyl)benzene, 1,8-diazabicyclo(5,4,0)-7-undecene, benzyl dimethyl amine, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-mercaptobenzothiazole, acetylacetone metal salt; The toughening agent is one or more of inorganic nanoparticles, polyether polyol, polysulfide rubber, PU prepolymer.

5. The method of claim 1, wherein the method is characterized by: The composite material further comprises a reinforcing body and an auxiliary material; The reinforcing body is at least one of carbon fiber, glass fiber, natural fiber, chemical fiber, and fabric made of fiber material, nano-carbon material, boron nitride nano material, metal nanoparticles, metal oxide nanoparticles, and organic nanoparticles, and accounts for 50wt%-65wt% of the total mass of the composite material; The auxiliary material is at least one of an accelerator, a diluent, a plasticizer, a toughening agent, a thickening agent, a coupling agent, a defoaming agent, a leveling agent, an ultraviolet absorber, an antioxidant, a brightener, a fluorescent agent, a pigment, and a filler, and accounts for 0.1wt%-2wt% of the total mass of the composite material.

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