An epoxy resin monomer based on furan containing imine bonds, its preparation method and its application

Abstract

This invention relates to an epoxy resin monomer based on furan containing imine bonds, its preparation method, and its applications, belonging to the field of epoxy resin technology. The furan-based epoxy resin monomer introduces a five-membered ring containing oxygen into its molecular chain. The oxygen atom provides an activation site for hydrogen bonding, strengthening the non-covalent bonds between molecular chains. When subjected to external impact, the non-covalent bonds break first, absorbing part of the impact energy, thus improving the material's toughness. The introduction of dynamic imine bonds into the monomer endows the epoxy resin with recyclability. The resin product obtained after curing this epoxy resin monomer is reprocessable and biodegradable.

Description

Technical Field

[0001] This invention relates to an epoxy resin monomer based on furan containing imine bonds, its preparation method, and its application, belonging to the field of epoxy resin technology. Background Technology

[0002] Epoxy resins possess excellent mechanical properties, high-temperature resistance, corrosion resistance, adhesion, and electrical insulation, making them widely used in the automotive, construction, electronics, and aerospace industries. They are currently the most widely used thermosetting resin. However, the vast majority of epoxy resin raw materials used today are derived from petroleum, which is unsustainable. Bio-based epoxy resins, using renewable resources as primary raw materials, can reduce dependence on petrochemical products. Simultaneously, they can reduce environmental pollution during the production of petroleum-based raw materials, representing an important development direction for polymer materials with significant practical value and broad development prospects.

[0003] In addition, due to the highly cross-linked three-dimensional network structure formed during the curing process, cured epoxy resin is infusible, insoluble, and difficult to degrade. Common post-treatment methods for epoxy resin include crushing, incineration, and solvent recovery, all of which cause environmental pollution and are energy-intensive, making them environmentally unfriendly. To obtain biodegradable and recyclable epoxy resins, current research focuses on introducing degradable functional groups into the resin, enabling the cured resin to easily degrade into smaller molecules. This allows for recycling and reduces energy consumption. Especially for carbon fiber composites, the high-value-added carbon fibers can be recovered after resin degradation, reducing usage costs and contributing to environmental protection and ecological balance.

[0004] In recent years, with the continuous increase in petroleum resource consumption, climate change, and increasingly prominent environmental pollution problems, the development and application of renewable bio-based raw materials to prepare degradable and recyclable polymer materials has become a research hotspot. The recycling of renewable resources can greatly alleviate energy and environmental pressures. Currently, there are no reports on the preparation of degradable and recyclable epoxy resin monomers based on biomass raw materials. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an epoxy resin monomer based on furan containing imine bonds, its preparation method and its application.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows.

[0007] An epoxy resin monomer based on furan containing imine bonds, with the general structural formula as shown in formula I, II, or III:

[0008]

[0009] Where R1 is

[0010] R2 is Or -CH2CH2-.

[0011] A method for preparing an epoxy resin monomer based on furan containing imine bonds, the method comprising the following steps:

[0012] (1) Dissolve amine compounds and aldehyde compounds separately in solvents to obtain amine compound solutions and aldehyde compound solutions. Add the amine chemical solution dropwise to the aldehyde compound solution and stir at 30-50°C for 8-12 hours. After cooling, filter and wash and dry the precipitate to obtain a primary amine-terminated or hydroxyl-terminated intermediate. Among them, one of the amine compound and aldehyde compound is a compound containing a furan structure.

[0013] (2) Epichlorohydrin was added to a mixed solvent of ethylene glycol and water, heated to reflux, and the intermediate was added in batches. The reaction temperature was controlled at 60-80°C. After the addition was completed, the reaction was continued to be heated and stirred. When the mixture became viscous and could not be stirred, acetone was added to dissolve it, and the reaction was continued at 70±5°C for 5-6 hours to obtain the reaction material.

[0014] (3) After cooling the reactants to room temperature, add acetone to dissolve them, add sodium hydroxide solution while stirring, and add phase transfer catalyst. Control the reaction temperature to 30±3℃ and react for 1 to 2 hours. After the reaction is completed, extract, separate the organic phase, filter, and evaporate the solvent under reduced pressure to obtain an epoxy resin monomer based on furan containing imine bonds.

[0015] Preferably, in step (1), the amine compound is one or more selected from 2,5-furandimethylamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, m-phenylenediamine, isofluranedione diamine, 4,4'-diaminodicyclohexylmethane, 1,4-cyclohexanediamine, methylcyclohexanediamine, p-hydroxyaniline, and 4-hydroxy-3-aminotetrahydrofuran; and the aldehyde compound is one or more selected from 2,5-furandicarboxaldehyde, 5-hydroxyfurfural, p-hydroxybenzaldehyde, and p-phenylenedialdehyde. More preferably, the amine compound is 2,5-furandimethylamine, p-phenylenediamine, or 1,4-cyclohexanediamine.

[0016] Preferably, in step (1), the solvent is one or more of methanol, ethanol and ethylene glycol.

[0017] Preferably, in step (2), the volume ratio of ethylene glycol to water is 90-95:5-10.

[0018] Preferably, in step (2), the time interval between each addition of the intermediate is 20 to 40 minutes.

[0019] Preferably, in step (2), the molar ratio of epichlorohydrin to the primary amine group or hydroxyl group in the intermediate is 1:1.

[0020] Preferably, in step (3), the phase transfer catalyst is one or more of benzyltriethylammonium chloride, tetramethylammonium chloride, benzyltriethylammonium chloride, methyltrioctylammonium chloride, and dodecyltrimethylammonium chloride.

[0021] Preferably, when the aldehyde compound is 2,5-furandicarboxaldehyde, the general structural formula of the intermediate is:

[0022] Preferably, when the aldehyde compound is 5-hydroxyfurfural, the general structural formula of the intermediate is:

[0023] Preferably, when the aldehyde compound is 5-hydroxyfurfural and the amine compound is p-hydroxyaniline, the general structural formula of the intermediate is:

[0024] Preferably, when the aldehyde compound is p-hydroxybenzaldehyde and the amine compound is 4-hydroxy-3-aminotetrahydrofuran, the general structural formula of the intermediate is:

[0025] An application of an epoxy resin monomer based on furan containing imine bonds involves mixing the monomer with a curing agent and heating to cure it, thereby obtaining an epoxy resin cured product containing furan rings and imine bonds.

[0026] Preferably, the curing agent is an amine curing agent, an acid anhydride curing agent, or an imidazole curing agent. More preferably, the amine curing agent is one or more selected from m-phenylenediamine, diaminodiphenylmethane, 4,4-diaminodiphenyl sulfone, 3,3-diaminodiphenyl sulfone, isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, and 4,4'-diaminodicyclohexylmethane. The acid anhydride curing agent is one or more selected from phthalic anhydride, trimellitic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and nadic anhydride. The imidazole curing agent is one or more selected from 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

[0027] Preferably, the epoxy resin cured product containing furan rings and imine bonds is added to a mixture of hydrochloric acid solution and organic amine solvent, and stirred at 50-80°C for more than 24 hours. The imine bonds are broken and the resin is degraded. The degradation products can be recycled and reused for the re-curing of epoxy resin.

[0028] Preferably, the epoxy resin curing material containing furan rings and imine bonds is pulverized and ground into powder, and then kept at 180-200°C and 5-7 MPa pressure for 10-20 minutes for secondary molding.

[0029] Beneficial effects

[0030] (1) The present invention is based on an epoxy resin monomer with a furan ring. A five-membered ring containing oxygen is introduced into the molecular chain. The oxygen atom provides an action site for hydrogen bonding, which strengthens the non-covalent bond interaction between molecular chains. When subjected to external force impact, the non-covalent bond is broken first to absorb part of the impact energy, thus improving the toughness of the material.

[0031] (2) The present invention introduces dynamic imine bonds into furan monomers. Imine bonds are a typical dynamic covalent bond. Under heating conditions, reversible exchange reactions can occur between imine bonds, giving furan-based epoxy resins a recyclable function.

[0032] (3) This invention utilizes 2,5-furandicarboxylic acid and its derivatives obtained from the conversion of sugars in regenerated plant resources. The resulting furan epoxy resin, prepared using a green synthesis process, can effectively replace petroleum-based bisphenol A products, thereby significantly reducing the hazards posed by petrochemicals. Developing high-performance epoxy resins based on such renewable resources is of great significance for alleviating environmental pollution and reducing energy consumption from petroleum resources.

[0033] (4) The present invention introduces the above three structures at the same time, and obtains a high-performance epoxy resin monomer based on biomass raw materials with good comprehensive performance. Attached Figure Description

[0034] Figure 1 This is the tensile stress-strain curve from Example 6. Detailed Implementation

[0035] The present invention will be further described in detail below with reference to specific embodiments.

[0036] Example 1

[0037] p-Phenylenediamine (10.81 g, 0.1 mol) and 2,5-furandicarboxaldehyde (6.20 g, 0.05 mol) were dissolved in 100 mL of ethanol to obtain p-Phenylenediamine solution and furandicarboxaldehyde solution, respectively. The p-Phenylenediamine solution was slowly added dropwise to the furandicarboxaldehyde solution, and the reaction was stirred at 50 °C for 8 h. After cooling, the precipitate was obtained by filtration. The precipitate was washed and then dried under vacuum to obtain an amino-terminated intermediate containing an imine bond.

[0038] A mixture of epichlorohydrin (46.26 g, 0.5 mol) and 200 ml of ethylene glycol and water (ethylene glycol to water volume ratio 90:10) was added to a 500 ml three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, constant-pressure dropping funnel, and dry nitrogen gas. Then, 1.14 g, 0.005 mol of benzyltriethylammonium chloride was added. The mixture was heated to 60 °C, and an intermediate (15.22 g, 0.05 mol) was added dropwise in portions (every 30 min at intervals) through the constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 70 °C for 6 h. The reaction progress was monitored using a thin-layer chromatography (TCL) silica gel plate, and the degree of reaction was determined based on the TCL markings.

[0039] 60g of 30% sodium hydroxide (dissolved in 70g of water) was slowly added dropwise using a constant-pressure dropping funnel. The temperature was lowered to 50℃. After the addition was complete, the reaction was stopped approximately 1 hour later when the reaction of the first group of substances in the system was confirmed to be complete by TCL.

[0040] After filtering the reaction product, it was extracted with toluene in small amounts several times, and the supernatant was collected and dried with anhydrous magnesium sulfate. After filtration, the product was evaporated to dryness at 50°C to obtain a dark brown oily product. The crude yield was calculated to be 91%. The epoxy value was tested to be 0.72.

[0041] Infrared spectroscopy analysis revealed that the final product was at 1640 cm⁻¹. -1 There is an imine bond vibration peak at 912 cm⁻¹. -1 There is a stretching vibration peak of epoxy groups at this location.

[0042] The structural formula of the final product is:

[0043]

[0044] The product was mixed with the curing agent 4,4′-diaminodiphenylmethane and heated and stirred at 50°C for 30 min. The mixture was poured into a mold, degassed, and then cured at 100°C for 1 h, 140°C for 1 h, and 180°C for 1 h to obtain the biodegradable and recyclable polymer containing dynamic imine bonds. Tensile strength was tested on samples. The test results are shown in Table 1.

[0045] Example 2

[0046] 1,4-cyclohexanediamine (11.42 g, 0.1 mol) and furanyl dicarboxaldehyde (6.20 g, 0.05 mol) were dissolved in 100 mL of ethanol to obtain 1,4-cyclohexanediamine solution and furanyl dicarboxaldehyde solution, respectively. The 1,4-cyclohexanediamine solution was slowly added dropwise to the furanyl dicarboxaldehyde solution, and the reaction was stirred at 50 °C for 11 h. After cooling, the precipitate was obtained by filtration. The precipitate was washed and then dried under vacuum to obtain an amino-terminated intermediate containing an imine bond.

[0047] A mixture of epichlorohydrin (46.26 g, 0.5 mol) and 100 mL of ethylene glycol and water (ethylene glycol to water volume ratio 90:10) was added to a 500 mL three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, constant-pressure dropping funnel, and dry nitrogen gas. Then, 1.14 g, 0.005 mol of benzyltriethylammonium chloride was added. The mixture was heated to 60 °C, and then 15.82 g, 0.05 mol of the intermediate and 100 mL of anhydrous ethanol were added slowly dropwise through the constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 70 °C for 6 h. The reaction progress was monitored using a thin-layer chromatography (TCL) silica gel plate, and the degree of reaction was determined based on the TCL markings.

[0048] 60g of sodium hydroxide (30g NaOH dissolved in 70g water) with a mass fraction of 30% was slowly added dropwise using a constant pressure dropping funnel. The temperature was lowered to 50℃. After the addition was completed, the reaction was stopped approximately 1 hour later when the reaction of the first group of substances in the system was confirmed to be complete by TCL.

[0049] After filtering the reaction product, it was extracted with toluene in small amounts several times, and the supernatant was collected and dried with anhydrous magnesium sulfate. After filtration, the product was evaporated to dryness at 50°C to obtain a dark brown oily product. The crude yield was calculated to be 91%. The epoxy value was tested to be 0.69.

[0050] Infrared spectroscopy analysis revealed that the final product was at 1640 cm⁻¹. -1 There is an imine bond vibration peak at 912 cm⁻¹. -1 There is a stretching vibration peak of epoxy groups at this location.

[0051] The structural formula of the final product is:

[0052]

[0053] The product was mixed with the curing agent 4,4′-diaminodiphenylmethane and heated and stirred at 50°C for 30 min. The mixture was poured into a mold, degassed, and then cured at 100°C for 1 h, 140°C for 1 h, and 180°C for 1 h to obtain the biodegradable and recyclable polymer containing dynamic imine bonds. Tensile strength was tested on a sample. The test results are shown in Table 1.

[0054] Example 3

[0055] Methylcyclohexanediamine (12.82 g, 0.1 mol) and 5-hydroxyfurfural (11.21 g, 0.1 mol) were dissolved in 100 ml of ethanol to obtain methylcyclohexanediamine solution and 5-hydroxyfurfural solution, respectively. The methylcyclohexanediamine solution was slowly added dropwise to the 5-hydroxyfurfural solution, and the reaction was stirred at 30 °C for 10 h. After cooling, the precipitate was obtained by filtration. The precipitate was washed and then dried under vacuum to obtain an imine bond-containing intermediate with one hydroxyl group and the other amino group.

[0056] A mixture of epichlorohydrin (74.02 g, 0.8 mol) and 200 mL of ethylene glycol and water (ethylene glycol to water volume ratio 90:10) was added to a 500 mL three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, constant-pressure dropping funnel, and dry nitrogen gas. Then, 2.28 g, 0.01 mol of benzyltriethylammonium chloride was added. The mixture was heated to 60 °C, and then 22.23 g, 0.1 mol of the intermediate and 200 mL of anhydrous ethanol were added slowly dropwise through the constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 70 °C for 6 h. The reaction progress was monitored using a thin-layer chromatography (TCL) silica gel plate, and the degree of reaction was determined based on the spotting pattern on the plate.

[0057] 60g of sodium hydroxide (30g NaOH dissolved in 70g water) with a mass fraction of 30% was slowly added dropwise using a constant pressure dropping funnel. The temperature was lowered to 50℃. After the addition was completed, the reaction was stopped approximately 1 hour later when the reaction of the first group of substances in the system was confirmed to be complete by TCL.

[0058] After filtering the reaction product, it was extracted with toluene in small amounts several times, and the supernatant was collected and dried with anhydrous magnesium sulfate. After filtration, the product was evaporated to dryness at 50°C to obtain a dark brown oily product. The crude yield was calculated to be 90%. The epoxy value was tested to be 0.73.

[0059] Infrared spectroscopy analysis revealed that the final product was at 1640 cm⁻¹. -1 There is an imine bond vibration peak at 912 cm⁻¹. -1 There is a stretching vibration peak of epoxy groups at this location.

[0060] The structural formula of the final product is:

[0061]

[0062] The product was mixed with the curing agent methylhexahydrophthalic anhydride and heated and stirred at 50°C for 30 min. The mixture was poured into a mold, degassed, and then cured at 100°C for 1 h, 140°C for 1 h, and 180°C for 1 h to obtain the biodegradable and recyclable polymer containing dynamic imine bonds. Tensile strength was tested on a sample. The test results are shown in Table 1.

[0063] Example 4

[0064] 10.9 g (0.1 mol) of p-hydroxyaniline and 11.21 g (0.1 mol) of 5-hydroxyfurfural were dissolved in 100 mL of ethanol to obtain p-hydroxyaniline solution and 5-hydroxyfurfural solution respectively. The p-hydroxyaniline solution was slowly added dropwise to the 5-hydroxyfurfural solution and the reaction was stirred at 30 °C for 12 h. After cooling, the precipitate was obtained by filtration. The precipitate was washed and then dried under vacuum to obtain an intermediate with hydroxyl-terminated imine bonds.

[0065] A mixture of epichlorohydrin (46.26 g, 0.5 mol) and 200 ml of ethylene glycol and water (ethylene glycol to water volume ratio 90:10) was added to a 500 ml three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, constant-pressure dropping funnel, and dry nitrogen gas. Then, 2.28 g, 0.01 mol of benzyltriethylammonium chloride was added. The mixture was heated to 60 °C, and then 20.32 g, 0.1 mol of the intermediate and 200 ml of anhydrous ethanol were added slowly dropwise through the constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 70 °C for 5 hours. The reaction progress was monitored using a thin-layer chromatography (TCL) silica gel plate, and the degree of reaction was determined based on the TCL markings.

[0066] 60g of sodium hydroxide (30g NaOH dissolved in 70g water) with a mass fraction of 30% was slowly added dropwise using a constant pressure dropping funnel. The temperature was lowered to 50℃. After the addition was completed, the reaction was stopped 1 hour later by TCL to confirm that the first group of substances in the system had reacted completely.

[0067] After filtering the reaction product, it was extracted with toluene in small amounts several times, and the supernatant was collected and dried with anhydrous magnesium sulfate. After filtration, the product was evaporated to dryness at 50°C to obtain a dark brown oily product. The crude yield was calculated to be 92%. The epoxy value was tested to be 0.58.

[0068] Infrared spectroscopy analysis revealed that the final product was at 1640 cm⁻¹. -1 There is an imine bond vibration peak at 912 cm⁻¹. -1 There is a stretching vibration peak of epoxy groups at this location.

[0069] The structural formula of the final product is:

[0070]

[0071] The product was mixed with the curing agent methylhexahydrophthalic anhydride and heated and stirred at 50°C for 30 min. The mixture was poured into a mold, degassed, and then cured at 100°C for 1 h, 140°C for 1 h, and 180°C for 1 h to obtain the biodegradable and recyclable polymer containing dynamic imine bonds. Tensile strength was tested on a sample. The test results are shown in Table 1.

[0072] Example 5

[0073] p-hydroxybenzaldehyde (12.21 g, 0.1 mol) and 4-hydroxy-3-aminotetrahydrofuran (10.31 g, 0.1 mol) were dissolved in 100 mL of ethanol to obtain p-hydroxybenzaldehyde and 4-hydroxy-3-aminotetrahydrofuran solutions. The 4-hydroxy-3-aminotetrahydrofuran solution was slowly added dropwise to the p-hydroxybenzaldehyde solution, and the reaction was stirred at 50 °C for 8 h. After cooling, the precipitate was obtained by filtration. The precipitate was washed and then dried under vacuum to obtain a hydroxyl-terminated intermediate containing an imine bond.

[0074] A mixture of epichlorohydrin (46.26 g, 0.5 mol) and 200 mL of ethylene glycol and water (ethylene glycol to water volume ratio 90:10) was added to a 500 mL three-necked round-bottom flask equipped with a magnetic stirrer, reflux condenser, constant-pressure dropping funnel, and dry nitrogen gas. Then, 2.28 g, 0.01 mol of benzyltriethylammonium chloride was added. The mixture was heated to 60 °C, and then 20.72 g, 0.1 mol of the intermediate and 200 mL of anhydrous ethanol were added slowly dropwise through the constant-pressure dropping funnel. After the addition was complete, the reaction was continued at 70 °C for 6 h. The reaction progress was monitored using a thin-layer chromatography (TCL) silica gel plate, and the degree of reaction was determined based on the TCL markings.

[0075] 60g of sodium hydroxide (30g NaOH dissolved in 70g water) with a mass fraction of 30% was slowly added dropwise using a constant pressure dropping funnel. The temperature was lowered to 50℃. After the addition was completed, the reaction was stopped approximately 1 hour later when the reaction of the first group of substances in the system was confirmed to be complete by TCL.

[0076] After filtering the reaction product, it was extracted with toluene in small amounts several times, and the supernatant was collected and dried with anhydrous magnesium sulfate. After filtration, the product was evaporated to dryness at 50°C to obtain a dark brown oily product. The crude yield was calculated to be 92%. The epoxy value was tested to be 0.58.

[0077] Infrared spectroscopy analysis revealed that the final product was at 1640 cm⁻¹. -1 There is an imine bond vibration peak at 912 cm⁻¹. -1 There is a stretching vibration peak of epoxy groups at this location.

[0078] The structural formula of the final product is:

[0079]

[0080] The product was mixed with the curing agent methylhexahydrophthalic anhydride and heated and stirred at 60°C for 30 min. The mixture was poured into a mold, degassed, and then cured at 100°C for 1 h, 140°C for 1 h, and 180°C for 1 h to obtain the biodegradable and recyclable polymer containing dynamic imine bonds. Tensile strength was tested on a sample. The test results are shown in Table 1.

[0081] Example 5

[0082] In the degradation experiment, 1g of the polymer from Example 1 was ground into powder and placed in 16mL of tetrahydrofuran at a concentration of 0.5mol·L⁻¹. -1 The polymer was completely dissolved in the hydrolysate by stirring at 50°C in 4 mL of hydrochloric acid. Then, the polymer was subjected to neutralization, solid-liquid separation, washing, and drying to obtain the degradation products of diamine and dialdehyde.

[0083] Example 6

[0084] The cured material from Example 1 is pulverized and ground into powder, then subjected to secondary molding at 180-200℃, 5-7MPa pressure, and 10-20 minutes. Tensile strength is tested by cutting test strips. The tensile stress-strain curves for primary and secondary molding are shown below. Figure 1 As shown.

[0085] Test method:

[0086] 1. Tensile strength test

[0087] According to GB / T2567-2008 "Test Methods for Performance of Resin Castings", the tensile strength test specimen is dumbbell-shaped, and the test is conducted using the bulk casting material at a test speed of 10 mm / min.

[0088] 2. Impact strength test

[0089] According to GB / T 2571-1995 "Impact Test Method for Resin Castings", a single impact bending load is applied to the specimen using a cantilever beam impact testing machine to cause the specimen to break. The impact toughness of the material is measured by the energy absorbed per unit area when the specimen breaks. The specimen preparation is carried out in accordance with the standard.

[0090] Table 1

[0091]

[0092]

[0093] This invention utilizes 2,5-furandicarboxylic acid and its derivatives obtained from the conversion of sugars in regenerated plant resources, and develops high-performance epoxy resins based on these renewable resources, which is of great significance for alleviating environmental pollution and reducing energy consumption of petroleum resources.

[0094] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. An epoxy resin monomer based on furan containing imine bonds, characterized in that: The structural formula is: 、 、 or 。 2. A method for preparing an epoxy resin monomer based on furan containing imine bonds as described in claim 1, characterized in that: The method steps include: (1) Dissolve amine compounds and aldehyde compounds in solvents to obtain amine compound solutions and aldehyde compound solutions respectively. Add the amine chemical solution dropwise to the aldehyde compound solution and stir at 30~50℃ for 8~12h. After cooling, filter and wash and dry the precipitate to obtain a primary amine-terminated or hydroxyl-terminated intermediate. (2) Add epichlorohydrin to a mixed solvent of ethylene glycol and water, heat to reflux, add the intermediate in batches, control the reaction temperature to 60~80℃, after the addition is completed, continue to heat and stir the reaction, when it becomes viscous and cannot be stirred, add acetone to dissolve, and continue to react at 70±5℃ for 5~6h to obtain the reaction material; (3) After cooling the reactants to room temperature, add acetone to dissolve them, add sodium hydroxide solution while stirring, and add phase transfer catalyst. Control the reaction temperature to 30±3℃ and react for 1~2h. After the reaction is completed, extract, separate the organic phase, filter, and evaporate the solvent under reduced pressure to obtain an epoxy resin monomer based on furan containing imine bonds. The aldehyde compound is 2,5-furandicarboxaldehyde or 5-hydroxyfurfural; the amine compound is p-phenylenediamine, methylcyclohexanediamine, p-hydroxyaniline or 1,4-cyclohexanediamine.

3. The method for preparing an epoxy resin monomer based on furan containing imine bonds as described in claim 2, characterized in that: In step (1), the solvent is one or more of methanol, ethanol and ethylene glycol.

4. The method for preparing an epoxy resin monomer based on a furan imine bond as described in claim 2, characterized in that: In step (2), the volume ratio of ethylene glycol to water is 90~95:5~10; The time interval between each addition of the intermediate is 20-40 minutes; The molar ratio of epichlorohydrin to the primary amine or hydroxyl groups in the intermediate is 1:

1.

5. The method for preparing an epoxy resin monomer based on a furan-containing imine bond as described in claim 2, characterized in that: In step (3), the phase transfer catalyst is one or more of benzyltriethylammonium chloride, tetramethylammonium chloride, benzyltriethylammonium chloride, methyltrioctylammonium chloride and dodecyltrimethylammonium chloride.

6. The application of a furan-based imine-containing epoxy resin monomer as described in claim 1, characterized in that: The monomer is mixed with a curing agent and heated to cure, resulting in an epoxy resin cured product containing furan rings and imine bonds.

7. The application of a furan-based imine-containing epoxy resin monomer as described in claim 6, characterized in that: The curing agent is an amine curing agent, an acid anhydride curing agent, or an imidazole curing agent.

8. The application of a furan-based imine-containing epoxy resin monomer as described in claim 7, characterized in that: The amine curing agent is one or more of m-phenylenediamine, diaminodiphenylmethane, 4,4-diaminodiphenyl sulfone, 3,3-diaminodiphenyl sulfone, isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, and 4,4'-diaminodicyclohexylmethane; the anhydride curing agent is one or more of phthalic anhydride, trimellitic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and nadic anhydride; the imidazole curing agent is one or more of 2-methylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, 1-cyanoethyl-2-methylimidazole, and 1-cyanoethyl-2-ethyl-4-methylimidazole.

9. The application of a furan-based imine-containing epoxy resin monomer as described in claim 7, characterized in that: The epoxy resin cured product containing furan rings and imine bonds is added to a mixture of hydrochloric acid solution and organic amine solvent, and stirred at 50~80℃ for more than 24 hours. The imine bonds are broken and the resin is degraded. The degradation products can be recycled and reused for the re-curing of epoxy resin.

10. The application of a furan-based imine-containing epoxy resin monomer as described in claim 7, characterized in that: The epoxy resin curing material containing furan rings and imine bonds is pulverized and ground into powder, and then subjected to heat and pressure holding at 180~200℃ and 5~7MPa for 10~20 minutes for secondary molding.

Images