Method for preparing high-performance epoxy resin by using eutectic aromatic amine as curing agent

Abstract

The invention discloses a preparation method of high-performance epoxy resin by using eutectic aromatic amine as a curing agent, and belongs to the technical field of high-performance epoxy resin. The high-performance epoxy resin is prepared from a eutectic aromatic amine curing agent and a polyfunctional epoxy resin monomer. Aromatic amine eutectic systems with different molecular configurations are designed and constructed by utilizing hydrogen bond interaction and pi-pi stacking effect among aromatic amine molecules. The formation of the eutectic system significantly reduces the melting point of the traditional aromatic amine curing agent, and improves the processability of the epoxy resin. Meanwhile, the residual stress of the eutectic aromatic amine cured epoxy resin is lower than that of a single aromatic amine cured system, so that the material is endowed with more excellent mechanical properties. According to the eutectic aromatic amine design strategy provided by the invention, the forming process of the epoxy resin is effectively improved, and a new method is provided for structure screening of a high-melting-point curing agent and performance optimization of the epoxy resin.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and specifically to a preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent. Background Art

[0002] Epoxy resins have shown broad application prospects in high-end manufacturing fields such as aerospace, wind power blades, and high-performance coatings due to their excellent mechanical properties, chemical stability, and adhesion properties. Among them, epoxy resin systems with aromatic amines as curing agents have attracted much attention due to their outstanding mechanical properties and thermal stability. However, the high melting point of aromatic amine curing agents requires that their miscibility with epoxy monomers must be carried out at a relatively high temperature, which easily causes premature cross-linking reactions between aromatic amines and epoxy resin monomers, resulting in a sharp increase in the viscosity of the system, thereby narrowing the processing window of the material and deteriorating the process controllability, seriously restricting its further large-scale application in fields such as high-performance fiber-reinforced composites. In addition, the high reactivity of single aromatic amine curing agents causes large residual stresses in the cured epoxy resins, reducing the mechanical properties of the materials. Therefore, the design and development of new aromatic amine curing agents with both low melting points and excellent curing properties have become the research focus in the field of high-performance epoxy resins.

[0003] In traditional processes, methods such as adding diluents are usually used to reduce the viscosity of epoxy resin prepreg solutions. However, this method has obvious limitations: on the one hand, diluents can only limit the reduction of the system viscosity and cannot fundamentally change the rheological properties of epoxy resin prepreg solutions; on the other hand, excessive use of diluents will lead to a decline in the properties of the cured materials. Eutectics provide a new idea for solving this technical problem. A eutectic is composed of two or more components that do not undergo chemical reactions at the molecular level but inhibit the crystallization process through intermolecular interactions (such as hydrogen bonds, π-π stacking, etc.), thereby reducing the melting point of the mixture to be lower than that of any single component. By introducing eutectic curing agents into the epoxy resin system, dual optimization effects can be achieved: (1) significantly reducing the melting temperature of the curing agent, reducing the risk of premature cross-linking reactions between the curing agent and epoxy monomers, and effectively extending the operation window period; (2) avoiding the use of diluents, while improving the processing performance, ensuring that the cured product has good mechanical and thermal properties.

[0004] Starting from commercial raw materials, this invention designs and constructs an aromatic amine eutectic system with different molecular configurations by utilizing the hydrogen bond interaction and π-π stacking effect between aromatic amine molecules. The formation of the eutectic system not only significantly reduces the melting point of traditional aromatic amine curing agents, improving the processing performance of epoxy resins, but also makes the residual stress of the cured epoxy resin lower than that of a single aromatic amine curing system, thereby endowing the material with more excellent mechanical properties. The eutectic aromatic amine design strategy proposed in this invention effectively improves the molding process of epoxy resins and provides a new method for the structural screening of high-melting-point curing agents and the performance optimization of epoxy resins. Summary of the Invention

[0005] The purpose of this invention is to overcome the problem that epoxy resin materials using aromatic amines as curing agents are difficult to have both good molding processes and high performance, and provides a preparation method of high-performance epoxy resins using eutectic aromatic amines as curing agents. Its main principle is: by utilizing the hydrogen bond interaction and π-π stacking effect between aromatic amine molecules, the crystallization ability of the system is inhibited, thereby reducing the melting point of the system to achieve the purpose of improving the processing performance of epoxy resins. At the same time, by changing the molecular configuration and ratio of the eutectic aromatic amine components, the reaction kinetics and stress relaxation behavior between the epoxy resin monomer and the curing agent are balanced, thereby realizing the optimization of the comprehensive performance of epoxy resins.

[0006] The specific technical content of this invention is as follows:

[0007] 1. A high-performance epoxy resin using eutectic aromatic amines as curing agents is prepared by forming a prepolymer solution C from eutectic aromatic amine curing agent A and epoxy monomer B, followed by curing and cooling, where:

[0008] The eutectic aromatic amine curing agent A is prepared from aromatic amine monomers a1 and a2 containing hydrogen bond donors and acceptors in a molar ratio of 1:1 to 10;

[0009] The aromatic amine a1 containing hydrogen bond donors and acceptors includes one or more of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine;

[0010] The structural formula of o-phenylenediamine is:

[0011] The structural formula of m-phenylenediamine is:

[0012] The structural formula of p-phenylenediamine is:

[0013] The aromatic amine a2 containing hydrogen bond donors and acceptors includes one or more of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, and 4,4'-dithiobis(aniline);

[0014] The structural formula of 4,4'-diaminodiphenylmethane is as follows:

[0015] The structural formula of 4,4'-diaminodiphenyl ether is as follows:

[0016] The structural formula of 3,4'-diaminodiphenyl ether is as follows:

[0017] The structural formula of 4,4'-diaminodiphenyl sulfone is as follows:

[0018] The structural formula of 3,3'-diaminodiphenyl sulfone is as follows:

[0019] The structural formula of 4,4'-dithiobisbenzenamine is as follows:

[0020] The epoxy monomer B is a polyfunctional epoxy monomer, including one or more of diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate, bis(2,3-epoxypropyl) terephthalate, and triglycidyl p-aminophenol;

[0021] The structural formula of diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate is as follows:

[0022] The structural formula of bis(2,3-epoxypropyl) terephthalate is as follows:

[0023] The structural formula of triglycidyl p-aminophenol is as follows:

[0024] 2. A preparation method of a high-performance epoxy resin using a eutectic aromatic amine as a curing agent, comprising the following steps:

[0025] (1) Mix the hydrogen bond donor-acceptor aromatic amine monomer a1 and the aromatic amine monomer a2 in a molar ratio of 1:1 to 10, and heat to 100-180 °C and melt thoroughly for 1-5 h to obtain the eutectic aromatic amine curing agent A;

[0026] (2) Mix the eutectic aromatic amine curing agent A and the epoxy monomer B evenly and then heat to 30-90 °C to obtain the resin prepreg solution C;

[0027] (3) After the prepreg solution C is defoamed under vacuum, it is cast, and the curing conditions are: curing at 70-90 °C for 1-4 h, curing at 100-120 °C for 1-4 h, and curing at 160-180 °C for 0-3 h.

[0028] Beneficial effects

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] 1. By utilizing the hydrogen bond interaction and π-π stacking effect between aromatic amine molecules, the eutectic aromatic amine is prepared by a one-step melting method, which reduces the melting point of traditional aromatic amine by 30-125 °C. At the same time, compared with the non-eutectic prepreg system, the introduction of the eutectic aromatic amine reduces the viscosity of the epoxy resin prepreg by 60-95%, effectively improving the processing performance of the material.

[0031] 2. By changing the proportion of the eutectic aromatic amine components, the reaction kinetics and stress relaxation behavior between the epoxy resin monomer and the curing agent are balanced, thereby optimizing the comprehensive performance of the epoxy resin. The tensile strength of the epoxy resin is ≥110 MPa, the Young's modulus is ≥3.8 GPa, and the glass transition temperature (T g ) ≥170 °C.

[0032] In summary, the present invention solves the problem that epoxy resins cured with aromatic amines are difficult to have both good molding processes and high performance, broadens the application of eutectics in the low-melting-point modification of aromatic amine curing agents, and provides a new method for the design of high-performance epoxy resin curing agents. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Melting point curve of the eutectic aromatic amine provided for Example 1;

[0034] Figure 2 Tensile stress-strain curve of the epoxy resin provided for Example 1;

[0035] Figure 3 Glass transition temperature curve of the epoxy resin provided for Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solutions of the present invention are clearly and completely described through specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. In each embodiment, the melting point of the aromatic amine is measured by a differential scanning calorimeter (DSC) with a heating rate of 5 °C / min; the viscosity of the epoxy resin prepreg at 25 °C is measured by a multi-functional viscometer; the tensile properties of the material are tested according to the standard of GB / T 1040.2-2022; the glass transition temperature (T g ) of the material is measured by a dynamic mechanical thermal analyzer (DMA) in a three-point bending mode with a frequency of 1 Hz and a heating rate of 5 °C / min.

[0037] Example 1

[0038] In this embodiment, triglycidyl p-aminophenol was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and o-phenylenediamine and 4,4'-diaminodiphenylmethane were purchased from Beijing Innochem Reagent Co., Ltd.

[0039] This embodiment includes a preparation method of eutectic aromatic amine and epoxy resin, which is as follows:

[0040] (1) Under the condition of 100°C to 120°C, 3 g of o-phenylenediamine and 7 g of 4,4'-diaminodiphenylmethane were blended until a uniform and transparent liquid was formed, and then cooled to room temperature for standby.

[0041] (2) 10 g of the eutectic aromatic amine obtained in (1) and 26 g of triglycidyl p-aminophenol were blended under the condition of 60 - 70°C to obtain a uniform and transparent epoxy resin prepreg solution, and then placed in an oven at 30 - 40°C for defoaming treatment.

[0042] (3) The epoxy resin prepreg solution obtained in (2) was poured into a metal mold and cured under a curing process of 80°C / 2 h + 120°C / 2 h + 160°C / 3 h, and the epoxy resin was obtained after cooling.

[0043] Example 2

[0044] In this embodiment, triglycidyl p-aminophenol was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and p-phenylenediamine and 4,4'-diaminodiphenylmethane were purchased from Beijing Innochem Reagent Co., Ltd.

[0045] This embodiment includes a preparation method of eutectic aromatic amine and epoxy resin, which is as follows:

[0046] (1) Under the condition of 100°C to 140°C, 2 g of p-phenylenediamine and 8 g of 4,4'-diaminodiphenylmethane were blended until a uniform and transparent liquid was formed, and then cooled to room temperature for standby.

[0047] (2) 10 g of the eutectic aromatic amine obtained in (1) and 20 g of triglycidyl p-aminophenol were blended under the condition of 65 - 75°C to obtain a uniform and transparent epoxy resin prepreg solution, and then placed in an oven at 30 - 40°C for defoaming treatment.

[0048] (3) The epoxy resin prepreg solution obtained in (2) was poured into a metal mold and cured under a curing process of 80°C / 2 h + 120°C / 2 h + 160°C / 3 h, and the epoxy resin was obtained after cooling.

[0049] Example 3

[0050] In this embodiment, triglycidyl p-aminophenol was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and m-phenylenediamine and 4,4'-dithiobis(aniline) were purchased from Beijing Innochem Reagent Co., Ltd.

[0051] This embodiment includes a preparation method of eutectic aromatic amine and epoxy resin, which is as follows:

[0052] (1) Under the condition of 100°C to 120°C, 6 g of m-phenylenediamine and 4 g of 4,4'-dithiobis(aniline) were blended until a uniform and transparent liquid was formed, and then cooled to room temperature for standby.

[0053] (2) 10 g of the eutectic aromatic amine obtained in (1) and 26 g of triglycidyl p-aminophenol were blended under the condition of 30 - 40°C to obtain a uniform and transparent epoxy resin pre-preg solution, and then placed in an oven at 30 - 40°C for defoaming treatment.

[0054] (3) The epoxy resin pre-preg solution obtained in (2) was poured into a metal mold and cured under the curing process of 80°C / 2 h + 120°C / 2 h + 160°C / 3 h, and the epoxy resin was obtained after cooling.

[0055] Example 4

[0056] In this embodiment, diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and m-phenylenediamine and 3,3'-diaminodiphenyl sulfone were purchased from Beijing Innochem Reagent Co., Ltd.

[0057] This embodiment includes a preparation method of eutectic aromatic amine and epoxy resin, which is as follows:

[0058] (1) Under the condition of 120°C to 170°C, 5 g of m-phenylenediamine and 3 g of 3,3'-diaminodiphenyl sulfone were blended until a uniform and transparent liquid was formed, and then cooled to room temperature for standby.

[0059] (2) 8 g of the eutectic aromatic amine obtained in (1) and 23 g of diglycidyl 4,5-epoxycyclohexane-1,2-dicarboxylate were blended under the condition of 40 - 50°C to obtain a uniform and transparent epoxy resin pre-preg solution, and then placed in an oven at 30 - 40°C for defoaming treatment.

[0060] (3) The epoxy resin pre-preg solution obtained in (2) was poured into a metal mold and cured under the curing process of 80°C / 2 h + 120°C / 2 h + 180°C / 2 h, and the epoxy resin was obtained after cooling.

[0061] Example 5

[0062] In this example, bis(2,3-epoxypropyl) terephthalate was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and o-phenylenediamine and 4,4'-diaminodiphenyl ether were purchased from Beijing InnoChem Reagent Co., Ltd.

[0063] This example includes a preparation method of eutectic aromatic amine and epoxy resin, which is as follows:

[0064] (1) Under the condition of 160 °C to 180 °C, 5 g of o-phenylenediamine and 1 g of 4,4'-diaminodiphenyl ether were blended until a homogeneous and transparent liquid was formed, and then cooled to room temperature for standby.

[0065] (2) 6 g of the eutectic aromatic amine obtained in (1) and 20 g of bis(2,3-epoxypropyl) terephthalate were blended under the condition of 80 - 100 °C to obtain a homogeneous and transparent epoxy resin pre-preg solution, and then it was placed in an oven at 30 - 40 °C for defoaming treatment.

[0066] (3) The epoxy resin pre-preg solution obtained in (2) was poured into a metal mold and cured under the curing process of 80 °C / 2 h + 120 °C / 2 h + 180 °C / 2 h, and the epoxy resin was obtained after cooling.

[0067] Comparative Example 1

[0068] In this comparative example, triglycidyl p-aminophenol was selected as the epoxy monomer, and o-phenylenediamine and 4,4'-diaminodiphenylmethane were used as the curing agents. Triglycidyl p-aminophenol was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and o-phenylenediamine and 4,4'-diaminodiphenylmethane were purchased from Beijing InnoChem Reagent Co., Ltd.

[0069] The epoxy resin was prepared in this comparative example according to the following method:

[0070] (1) 3 g of o-phenylenediamine, 7 g of 4,4'-diaminodiphenylmethane and 26 g of triglycidyl p-aminophenol were blended under the condition of 95 - 105 °C to obtain a homogeneous and transparent epoxy resin pre-preg solution, and then it was placed in an oven at 30 - 40 °C for defoaming treatment.

[0071] (2) The epoxy resin pre-preg solution obtained in (1) was poured into a metal mold and cured under the curing process of 80 °C / 2 h + 120 °C / 2 h + 160 °C / 3 h, and the epoxy resin was obtained after cooling.

[0072] Comparative Example 2

[0073] In this comparative example, triglycidyl p-aminophenol was selected as the epoxy monomer, and p-phenylenediamine and 4,4'-diaminodiphenylmethane were used as curing agents. Triglycidyl p-aminophenol was purchased from Tianjin Jindong Chemical Composite Materials Co., Ltd., and p-phenylenediamine and 4,4'-diaminodiphenylmethane were purchased from Beijing Innochem Reagent Co., Ltd.

[0074] The epoxy resin was prepared by the following method in this comparative example:

[0075] (1) 1 g of o-phenylenediamine, 8 g of 4,4'-diaminodiphenylmethane and 20 g of triglycidyl p-aminophenol were blended at 100 - 140 °C to obtain a uniformly transparent epoxy resin pre-preg solution, which was then placed in an oven at 30 - 40 °C for defoaming treatment.

[0076] (2) The epoxy resin pre-preg solution obtained in (1) was poured into a metal mold and cured under a curing process of 80 °C / 2 h + 120 °C / 2 h + 160 °C / 3 h, and the epoxy resin was obtained after cooling.

[0077] Performance table of Examples 1 - 5 and Comparative Examples 1 - 2

[0078]

[0079] As can be seen from the above table, due to the use of the eutectic curing agent strategy, the melting points of the curing agents in Examples 1 and 2 were significantly lower than those in Comparative Examples 1 and 2. In addition, the high melting point and fast reaction rate of the non-eutectic system led to a significant increase in the viscosity of the pre-preg solution in Comparative Examples 1 and 2, preventing the molecular chains from fully relaxing, forming local residual stress and non-uniform crosslinked networks, resulting in a significant decrease in the tensile strength and Young's modulus of the epoxy resin material.

Claims

1. A method for preparing a high-performance epoxy resin using a eutectic aromatic amine as a curing agent, characterized in that: The high-performance epoxy resin is prepared by forming a prepolymer solution C from a eutectic aromatic amine curing agent A and an epoxy monomer B, followed by curing and cooling, where: The eutectic aromatic amine curing agent A is obtained by mixing an aromatic amine monomer a1 containing a hydrogen bond donor-acceptor and an aromatic amine monomer a2 in a molar ratio of 1:1 to 10, and heating to 100 to 180 °C for 1 to 5 h to fully melt. Its melting point is 30 to 90 °C, which is significantly reduced by 30 to 125 °C compared to the melting points of the aromatic amine monomer a1 and the aromatic amine monomer a2; The prepolymer solution C is obtained by uniformly mixing the eutectic aromatic amine curing agent A and the epoxy monomer B and heating to 30 to 90 °C. Its viscosity at 25 °C is 1 to 6 Pa·s, which is reduced by 60% to 95% compared to the non-eutectic prepolymer solution system.

2. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, wherein: The aromatic amine monomer a1 in the eutectic aromatic amine curing agent A is one or more of o-phenylenediamine, m-phenylenediamine, and p-phenylenediamine.

3. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, characterized in that: The aromatic amine monomer a2 in the eutectic aromatic amine curing agent A is one or more of 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, and 4,4'-dithiobisbenzenamine.

4. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, characterized in that: The epoxy monomer B is one or more of 4,5-epoxycyclohexane-1,2-dicarboxylic acid diglycidyl ester, 1,4-benzenedicarboxylic acid bis(2,3-epoxypropyl) ester, and triglycidyl p-aminophenol.

5. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, characterized in that: Based on 100 parts by weight of the epoxy monomer B, the aromatic amine monomer a1 is 5 to 50 parts by weight, preferably 10 to 25 parts by weight; the aromatic amine monomer a2 is 5 to 60 parts by weight, preferably 5 to 40 parts by weight.

6. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, characterized in that: The curing conditions of the prepolymer solution C are: curing at 70 to 90 °C for 1 to 4 h, curing at 100 to 120 °C for 1 to 4 h, and curing at 160 to 180 °C for 0 to 3 h.

7. The preparation method of a high-performance epoxy resin using eutectic aromatic amine as a curing agent according to claim 1, characterized in that: The tensile strength of the epoxy resin is ≥110 MPa, the Young's modulus is ≥3.8 GPa, and the glass transition temperature (T g ) is ≥170 °C.

Images