Preparation method of curing agent, curing agent, resin composition and composite material
By designing a staged reaction to prepare an amine borate ester curing agent, the problems of complex resin handling and storage were solved, achieving stable storage and excellent mechanical properties of carbon fiber filament-wound composite materials, which are suitable for continuous production.
Patent Information
- Application Number
- CN202510905831.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-02
- Publication Date
- 2025-11-14
Smart Images
Figure CN120943853A_ABST
Abstract
Description
Technical Field
[0001] This disclosure relates to the field of sheet metal processing and molding, and in particular to a method for preparing a curing agent, as well as the curing agent, resin composition, and composite material. Background Technology
[0002] Filament winding has been recognized as one of the preferred methods for low-cost manufacturing of high-performance carbon fiber composites. However, its efficiency in producing composite products is significantly affected by the resin used. The resin used for winding has always been characterized by complex handling, the need for timely use after mixing (otherwise it will easily harden), and the overall production process being influenced by the resin's curing time.
[0003] Latent curing agents, when mixed with epoxy resin, can be stored stably at room temperature, and the curing reaction only occurs when specific triggering conditions are met. The advent of latent curing agents allows epoxy resin prepolymers and curing agents to be formulated into single-component packages for sale, simplifying construction, saving costs, and reducing waste. Summary of the Invention
[0004] To address the problems existing in related technologies, this disclosure provides a method for preparing a curing agent, as well as the curing agent, resin composition, and composite material.
[0005] According to a first aspect of the present disclosure, a method for preparing a curing agent is provided, the method comprising:
[0006] Diethylene glycol, boric acid, diol and solvent in a first preset mass ratio are reacted under a first preset condition to obtain a first reaction system;
[0007] The first reaction system, a dicarboxylic acid and dimethylethanolamine in a second preset mass ratio are reacted and dehydrated under a second preset condition to obtain a second reaction system;
[0008] The solvent in the second reaction system is removed and dried to obtain a curing agent.
[0009] In some embodiments of this disclosure, the reaction of diethylene glycol, boric acid, diol, and solvent in a first preset mass ratio under first preset conditions to obtain a first reaction system includes:
[0010] The diethylene glycol, boric acid, diol and solvent in the first preset mass ratio are reacted at a temperature of 85-100°C for 20-40 minutes and water is removed by azeotropic distillation. Then the temperature is raised to 105-115°C until no water generated by the reaction can be collected, thus obtaining the first reaction system.
[0011] The first preset mass ratio is (3.8~6.3):(2.2~3.9):(1.5~2.7):(2.7~5.5).
[0012] In some embodiments of this disclosure, the diol includes at least one of ethylene glycol and neopentyl glycol;
[0013] The solvent includes toluene.
[0014] In some embodiments of this disclosure, the step of reacting the first reaction system, a dicarboxylic acid and dimethylethanolamine in a second preset mass ratio, and removing water under second preset conditions to obtain a second reaction system includes:
[0015] The temperature of the first reaction system is cooled to 85-100°C. The dicarboxylic acid and dimethylethanolamine in the second preset mass ratio are added to the first reaction system and heated and stirred. At the same time, water is removed by azeotropic distillation. Then, the temperature is raised to 105-115°C at the first preset heating rate until no water generated by the reaction can be collected, and the second reaction system is obtained.
[0016] The second preset mass ratio is (2.1~4.0):(2.2~3.9).
[0017] In some embodiments of this disclosure, the dicarboxylic acid includes at least one of oxalic acid and adipic acid.
[0018] In some embodiments of this disclosure, removing the solvent from the second reaction system and drying it to obtain the curing agent includes:
[0019] After cooling the second reaction system to 20-30°C, it is then heated to 105-115°C at the second preset heating rate for vacuum distillation until no distillate is produced, thus obtaining the pre-curing agent.
[0020] The pre-curing agent is placed in a vacuum oven and dried at 50–70°C to obtain the curing agent.
[0021] According to a second aspect of the present disclosure, a curing agent is provided, which is prepared by the curing agent preparation method described above;
[0022] The curing agent includes amine borate esters.
[0023] According to a third aspect of the present disclosure, a resin composition is provided, the resin composition comprising: 90 to 95 parts by weight of epoxy resin, 0.5 to 1 part by weight of accelerator and 4.5 to 9 parts by weight of curing agent as described above.
[0024] In some embodiments of this disclosure, the epoxy resin includes at least one of 128 epoxy resin or TDE-85 epoxy resin.
[0025] The promoter includes at least one of substituted urea, imidazole, or modified imidazole.
[0026] According to a fourth aspect of the present disclosure, a composite material is provided, which is prepared by winding the above-described resin composition with carbon fibers.
[0027] The beneficial effects of this disclosure include, but are not limited to: the method for preparing the curing agent provided by this disclosure does not require high-pressure reaction conditions and has a high process safety factor. Furthermore, through a staged reaction design, side reactions can be precisely controlled, avoiding the generation of byproducts, and forming an amine-boron ester curing agent. This amine-boron ester curing agent forms intramolecular coordination bonds at room temperature, inhibiting reactivity, allowing the amine-boron ester curing agent and epoxy resin to be stored stably at room temperature for a long period. Moreover, the carbon fiber wound composite material prepared with this amine-boron ester curing agent exhibits excellent mechanical properties.
[0028] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description
[0029] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of these embodiments. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the present disclosure, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without inventive effort.
[0030] Figure 1 This is a schematic diagram of a method for preparing a curing agent according to an exemplary embodiment of the present disclosure. Detailed Implementation
[0031] To make the objectives, technical solutions, and advantages of this disclosure clearer, the technical solutions of this disclosure will be clearly and completely described below in conjunction with the embodiments of this disclosure. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.
[0032] Filament winding has been recognized as one of the preferred methods for low-cost manufacturing of high-performance carbon fiber composites. However, its efficiency in producing composite products is significantly affected by the resin used. The resin used for winding has always been characterized by complex handling, the need for timely use after mixing (otherwise it will easily harden), and the overall production process being influenced by the resin's curing time.
[0033] Latent curing agents, when mixed with epoxy resin, can be stored stably at room temperature, and the curing reaction only occurs when specific triggering conditions are met. The advent of latent curing agents allows epoxy resin prepolymers and curing agents to be formulated into single-component packages for sale, simplifying construction, saving costs, and reducing waste.
[0034] Based on this, this disclosure provides a method for preparing a curing agent that does not require high-pressure reaction conditions and has a high process safety factor. Furthermore, through a staged reaction design, side reactions can be precisely controlled, avoiding the generation of byproducts, and forming an amine-boron ester curing agent. This amine-boron ester curing agent forms intramolecular coordination bonds at room temperature, inhibiting reactivity, allowing the amine-boron ester curing agent and epoxy resin to be stored stably at room temperature for a long period. Moreover, the carbon fiber wound composite material prepared using this amine-boron ester curing agent exhibits excellent mechanical properties.
[0035] An exemplary embodiment of this disclosure provides a method for preparing a curing agent, such as... Figure 1 As shown, the preparation method includes:
[0036] S100. Diethylene glycol, boric acid, diol and solvent in a first preset mass ratio are reacted under the first preset conditions to obtain the first reaction system.
[0037] For example, diethylene glycol, boric acid, and diol can be placed in a four-necked round-bottom flask according to a first preset mass ratio, and a solvent can be added to the four-necked round-bottom flask. The mixture can then react under the first preset conditions to obtain the first reaction system.
[0038] S200. The first reaction system, a dicarboxylic acid and dimethylethanolamine in a second preset mass ratio are reacted under a second preset condition and water is removed to obtain the second reaction system.
[0039] For example, dicarboxylic acid and dimethylethanolamine can be added to the first reaction system in a four-necked round-bottom flask according to the second preset mass ratio, reacted and dehydrated under the second preset conditions to obtain the second reaction system.
[0040] S300. Remove the solvent from the second reaction system and dry it to obtain the curing agent.
[0041] The curing agent preparation method provided in this embodiment does not require high-pressure reaction conditions, resulting in a high process safety factor. Furthermore, through a staged reaction design, side reactions can be precisely controlled, avoiding the generation of byproducts and forming an amine-boron ester curing agent. This amine-boron ester curing agent forms intramolecular coordination bonds at room temperature, inhibiting reactivity and allowing for long-term stable storage at room temperature after mixing with epoxy resin. Moreover, the carbon fiber wound composite material prepared using this amine-boron ester curing agent exhibits excellent mechanical properties.
[0042] In an exemplary embodiment, diethylene glycol, boric acid, diol and solvent in a first preset mass ratio are reacted under first preset conditions to obtain a first reaction system, including: reacting diethylene glycol, boric acid, diol and solvent in a first preset mass ratio at a temperature of 85-100°C for 20-40 min and removing water by azeotropic distillation, then raising the temperature to 105-115°C until no water generated by the reaction can be collected, to obtain the first reaction system; the first preset mass ratio is (3.8-6.3):(2.2-3.9):(1.5-2.7):(2.7-5.5).
[0043] In this embodiment, diethylene glycol, boric acid, diol, and solvent in a first preset mass ratio are placed in a four-necked round-bottom flask and reacted at a temperature of 85–100°C for 20–40 min, followed by azeotropic distillation to remove water. The low-temperature reaction condition of 85–100°C avoids dehydration and carbonization of the diol, and the short reaction time of 20–40 min ensures the initial formation of the borate ester. The reaction temperature can be, for example, 85°C, 95°C, or 100°C, or any value between these exemplary reaction temperatures; for example, any value between 90–95°C. The reaction time can be, for example, 20 min, 30 min, or 40 min, or any value between these exemplary reaction times; for example, any value between 25–35 min.
[0044] After reacting diethylene glycol, boric acid, diol and solvent in the first preset mass ratio at low temperature (85-100℃) for a short time (20-40 min), the temperature can be gradually increased to 105-115℃ at a heating rate of 2℃ / min to remove water, so as to ensure the conversion rate of borate ester. Heating is stopped when no more water generated by the reaction enters the water separator.
[0045] The first preset mass ratio of diethylene glycol, boric acid, diol, and solvent is (3.8–6.3):(2.2–3.9):(1.5–2.7):(2.7–5.5). This ensures complete esterification of boric acid and guarantees the efficiency of azeotropic distillation for water removal, preventing side reactions caused by local overheating. For example, the first preset mass ratio of diethylene glycol, boric acid, diol, and solvent can be 3.8:2.2:1.5:2.7, 5:3:2:4, or 6.3:3.9:2.7:5.5. The first preset mass ratio can also be any value between the exemplary preset mass ratios, for example, the first preset mass ratio can also be any value between 4:2.5:2:3 and 6:3.5:2.5:5.
[0046] In one exemplary embodiment, the diol includes at least one of ethylene glycol and neopentyl glycol, and the solvent includes toluene.
[0047] When ethylene glycol and neopentyl glycol are used as curing agents prepared from diols to cure resins, they can slow down the curing rate, extend the pot life of the resin, and improve the resin's hydrolysis resistance. It should be noted that either ethylene glycol or neopentyl glycol can be used, or both can be used simultaneously. Toluene has high azeotropic distillation efficiency for dehydration and is easily removed subsequently, leaving low residue; therefore, toluene is selected as the solvent in this embodiment.
[0048] In an exemplary embodiment, a first reaction system, a second preset mass ratio of dicarboxylic acid and dimethylethanolamine are reacted and dehydrated under second preset conditions to obtain a second reaction system. The reaction process includes: cooling the temperature of the first reaction system to 85-100°C, adding the second preset mass ratio of dicarboxylic acid and dimethylethanolamine to the first reaction system and heating and stirring, while simultaneously removing water by azeotropic distillation, and then heating to 105-115°C at a first preset heating rate until no water generated by the reaction can be collected, thereby obtaining the first reaction system; the second preset mass ratio is (2.1-4.0):(2.2-3.9).
[0049] Cooling the first reaction system to 85–100°C before adding dicarboxylic acid and dimethyl ethanol avoids the instantaneous and violent reaction of the dicarboxylic acid and dimethyl ethanol at high temperatures. After adding the materials, heat and stir for 60–80 minutes, while simultaneously removing water through azeotropic distillation to prevent water molecules from breaking the borate ester bonds and ensure the latency of the curing agent. The cooling temperature can be, for example, 85°C, 95°C, or 100°C, or any value between these exemplary cooling temperatures; for example, any value between 90 and 95°C. The heating and stirring time can be, for example, 60 minutes, 70 minutes, or 80 minutes, or any value between these exemplary heating and stirring times; for example, any value between 65 and 75 minutes.
[0050] After heating and stirring at 85–100°C, the temperature can be increased to 105–115°C at a first preset heating rate of 1.5–3°C / min until no water generated in the reaction can be collected by azeotropic distillation. This removes water molecules, yielding a second reaction system, preventing water molecules from breaking the borate ester bonds and ensuring the latent properties of the curing agent. The first preset heating rate can be 1.5°C / min, 2°C / min, or 3°C / min, or any value between these exemplary rates, such as 2–2.5°C / min. The heating temperature can be, for example, 105°C, 110°C, or 115°C, or any value between these exemplary rates, such as 108–112°C.
[0051] A second preset mass ratio of dicarboxylic acid to dimethylethanolamine within the range of (2.1–4.0):(2.2–3.9) ensures complete reaction of the carboxyl groups, prevents free carboxylic acid from initiating epoxy resin pre-curing, and avoids side reactions. For example, the second preset mass ratio of dicarboxylic acid to dimethylethanolamine can be 2.1:3.9, 3.0:3.0, or 4.0:2.2. The second preset mass ratio can also be any value between the exemplary preset mass ratios, such as any value between 2.1:3.5 and 3.5:2.5.
[0052] In one exemplary embodiment, the dicarboxylic acid includes at least one of oxalic acid and adipic acid. Oxalic acid is a short-chain molecule, which can increase the crosslinking density and is suitable for the preparation of high-rigidity composite materials. Adipic acid is a long-chain molecule, which can increase the flexibility of the molecular chain, improve the toughness of the composite material, and the long-chain carboxylic acid can reduce the hydrophilicity of the curing agent, enhancing storage stability.
[0053] In one exemplary embodiment, the second reaction system is desolventized and dried to obtain a curing agent, comprising:
[0054] After cooling the second reaction system to 20-30°C, it is then heated to 105-115°C at the second preset heating rate for vacuum distillation until no distillate is produced, thus obtaining the pre-cured agent.
[0055] The pre-curing agent is placed in a vacuum oven and dried at 50–70°C to obtain the curing agent.
[0056] After cooling the second reaction system to 20–30°C, for example, to room temperature, the reaction stops. The system is then heated to 105–115°C at a second preset heating rate of 1.5–3°C / min for vacuum distillation until no distillate is produced, yielding a pre-cured agent, which is the initial purified product of the second reaction system. The second preset heating rate can be 1.5°C / min, 2°C / min, or 3°C / min, or any value between these exemplary heating rates, for example, any value between 2 and 2.5°C / min. The vacuum distillation temperature can be, for example, 105°C, 110°C, or 115°C, or any value between these exemplary vacuum distillation temperatures, for example, any value between 108 and 112°C.
[0057] The initial purified product of the second reaction system, i.e., the pre-curing agent, is placed in a vacuum oven and dried at 50–70°C to further remove small molecule substances, yielding the curing agent. The drying temperature can be 50°C, 60°C, or 70°C, or any value between these exemplary drying temperatures; for example, the drying temperature can be any value between 55°C and 65°C. Thoroughly drying the curing agent to remove moisture and small molecule substances avoids water molecules initiating the pre-curing of the epoxy resin and the introduction of impurities.
[0058] An exemplary embodiment of this disclosure provides a curing agent prepared by the above-described curing agent preparation method. The curing agent includes an amine-boron ester. The amine-boron ester is thermoresponsive; it forms intramolecular coordination bonds at room temperature, inhibiting reactivity. This allows the curing agent, after being mixed with epoxy resin, to be stored stably at room temperature for extended periods. Users do not need to prepare the resin system on-site, avoiding gelation and waste problems caused by delayed mixing. This is suitable for continuous production scenarios such as winding molding. Furthermore, the curing agent prepared by the above-described curing agent preparation method, through a staged reaction design, allows for precise control of side reactions, avoiding the generation of byproducts.
[0059] An exemplary embodiment of this disclosure provides a resin composition comprising: 90 to 95 parts by weight of epoxy resin, 0.5 to 1 part by weight of an accelerator, and 4.5 to 9 parts by weight of a curing agent as described above.
[0060] The resin composition provided in this embodiment can be stored or sold after mixing the curing agent, accelerator, and epoxy resin in a preset mass ratio. This resin composition can be stored stably at room temperature for a long period, eliminating the need for on-site resin system preparation and avoiding gelation and waste issues caused by delayed mixing. It is suitable for continuous production scenarios such as filament winding. Specifically, the resin composition includes 90-95 parts by mass of epoxy resin, 0.5-1 parts by mass of accelerator, and 4.5-9 parts by mass of the curing agent as described above. This prevents pre-curing of the resin composition at low temperatures and ensures complete curing when the resin composition is used to prepare composite materials with carbon fibers through filament winding.
[0061] In one exemplary embodiment, the epoxy resin includes at least one of 128 epoxy resin or TDE-85 epoxy resin, and the accelerator includes at least one of substituted urea, imidazole, or modified imidazole.
[0062] Among them, epoxy resin 128 exhibits high reactivity, making it suitable for rapid curing applications, while the trifunctional structure of epoxy resin TDE-85 enhances the heat resistance of the composite material. It should be noted that epoxy resin 128 and epoxy resin TDE-85 can be used individually or in combination. Substituted urea accelerators exhibit good low-temperature latency, while imidazole or modified imidazole accelerators can accelerate high-temperature curing, improve production efficiency, and ensure complete curing. It should be noted that substituted urea, imidazole, or modified imidazole can be used individually, in combination of two, or in combination of all three.
[0063] An exemplary embodiment of this disclosure provides a composite material prepared by winding the aforementioned resin composition with carbon fibers.
[0064] The composite material provided in this embodiment is prepared by winding the aforementioned resin composition with carbon fiber. This resin composition can be stored stably at room temperature for a long period after mixing the curing agent, accelerator, and epoxy resin in a preset mass ratio. During the preparation of the composite material, there is no need for on-site resin system preparation, avoiding gelation and waste problems caused by delayed mixing. This achieves the goals of simplifying construction, saving costs, and reducing waste, making it suitable for continuous production scenarios such as winding. The composite material product possesses excellent mechanical properties.
[0065] To more clearly explain the technical solutions provided by the exemplary embodiments of this disclosure, a specific example of the preparation method of the curing agent provided by the exemplary embodiments of this disclosure is given.
[0066] Diethylene glycol, boric acid, diol, and solvent in a first preset mass ratio of (3.8–6.3):(2.2–3.9):(1.5–2.7):(2.7–5.5) are reacted at 85–100°C for 20–40 min, and water is removed by azeotropic distillation. Then the temperature is raised to 105–115°C until no more water can be collected from the reaction, thus obtaining the first reaction system.
[0067] The temperature of the first reaction system is cooled to 85-100°C. A second preset mass ratio of dicarboxylic acid and dimethylethanolamine of (2.1-4.0):(2.2-3.9) is added to the first reaction system and heated and stirred. At the same time, water is removed by azeotropic distillation. Then, the temperature is increased to 105-115°C at a first preset heating rate until no water generated by the reaction can be collected, thus obtaining the first reaction system.
[0068] After cooling the second reaction system to 20-30°C, it is then heated to 105-115°C at the second preset heating rate for vacuum distillation until no distillate is produced, thus obtaining the pre-cured agent.
[0069] The pre-curing agent is placed in a vacuum oven and dried at 50–70°C to obtain the curing agent.
[0070] The above-mentioned curing agent is used in the preparation of the resin composition: 90-95 parts by weight of epoxy resin, 0.5-1 parts by weight of accelerator and 4.5-9 parts by weight of the above-mentioned curing agent are mixed to obtain the resin composition.
[0071] The above resin composition is used to prepare composite materials: the above resin composition is heated to 50°C and stirred for 30 minutes until the resin composition is uniform, thereby obtaining a latent fast-curing resin system suitable for carbon fiber winding. The carbon fiber and the latent fast-curing resin system suitable for carbon fiber winding are then wound by wet winding to prepare composite materials.
[0072] Following the preparation methods described in the specific examples above, the content of each component was adjusted to prepare composite materials in Examples 1-12. The composite materials prepared in Examples 1-12 were then subjected to storage hardening time and gel time tests, as well as NOL tensile and lamellar shear tests according to GBT1458-2023 standard, as detailed in Table 1.
[0073] Table 1
[0074]
[0075]
[0076] Table 1 (continued)
[0077]
[0078]
[0079] As can be seen from Table 1, when the curing agent prepared by the exemplary embodiment of this disclosure is used to prepare composite materials, the resulting composite materials have good storage stability and high high-temperature gelation rate, and the resulting composite materials have high tensile strength and interlaminar shear strength.
[0080] The above-described contents can be implemented individually or in various combinations, and all such variations are within the scope of this disclosure.
[0081] Finally, it should be noted that in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.
[0082] The above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit it. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this disclosure.
Claims
1. A method for preparing a curing agent, characterized in that, The preparation method includes: Diethylene glycol, boric acid, diol and solvent in a first preset mass ratio are reacted under a first preset condition to obtain a first reaction system; The first reaction system, a dicarboxylic acid and dimethylethanolamine in a second preset mass ratio are reacted and dehydrated under a second preset condition to obtain a second reaction system; The solvent in the second reaction system is removed and dried to obtain a curing agent.
2. The method for preparing the curing agent according to claim 1, characterized in that, The first reaction system is obtained by reacting diethylene glycol, boric acid, diol and solvent in a first preset mass ratio under first preset conditions, including: The diethylene glycol, boric acid, diol and solvent in the first preset mass ratio are reacted at a temperature of 85-100°C for 20-40 minutes and water is removed by azeotropic distillation. Then the temperature is raised to 105-115°C until no water generated by the reaction can be collected, thus obtaining the first reaction system. The first preset mass ratio is (3.8~6.3):(2.2~3.9):(1.5~2.7):(2.7~5.5).
3. The method for preparing the curing agent according to claim 1 or 2, characterized in that, The diol includes at least one of ethylene glycol and neopentyl glycol; The solvent includes toluene.
4. The method for preparing the curing agent according to claim 1, characterized in that, The process of reacting the first reaction system, a dicarboxylic acid and dimethylethanolamine in a second preset mass ratio, under second preset conditions and removing water to obtain a second reaction system includes: The temperature of the first reaction system is cooled to 85-100°C. The dicarboxylic acid and dimethylethanolamine in the second preset mass ratio are added to the first reaction system and heated and stirred. At the same time, water is removed by azeotropic distillation. Then, the temperature is raised to 105-115°C at the first preset heating rate until no water generated by the reaction can be collected, and the second reaction system is obtained. The second preset mass ratio is (2.1~4.0):(2.2~3.9).
5. The method for preparing the curing agent according to claim 1 or 4, characterized in that, The dicarboxylic acid includes at least one of oxalic acid and adipic acid.
6. The method for preparing the curing agent according to claim 1, characterized in that, The step of removing the solvent from the second reaction system and drying it to obtain a curing agent includes: After cooling the second reaction system to 20-30°C, it is then heated to 105-115°C at the second preset heating rate for vacuum distillation until no distillate is produced, thus obtaining the pre-curing agent. The pre-curing agent is placed in a vacuum oven and dried at 50–70°C to obtain the curing agent.
7. A curing agent, characterized in that, The curing agent is prepared by the method for preparing the curing agent according to any one of claims 1 to 6; The curing agent includes amine borate esters.
8. A resin composition, characterized in that, The resin composition comprises: 90-95 parts by weight of epoxy resin, 0.5-1 parts by weight of accelerator, and 4.5-9 parts by weight of curing agent as described in claim 7.
9. The resin composition according to claim 8, characterized in that, The epoxy resin includes at least one of 128 epoxy resin or TDE-85 epoxy resin; The promoter includes at least one of substituted urea, imidazole, or modified imidazole.
10. A composite material, characterized in that, The composite material is prepared by winding the resin composition of claim 8 or 9 with carbon fiber.