A trifunctional bio-based epoxy resin monomer, bio-based epoxy resin, and methods of preparation and rework

Abstract

The present application relates to the technical field of bio-based epoxy resin, and provides a trifunctional bio-based epoxy resin monomer, a bio-based epoxy resin and a preparation method and a reshaping method.The bio-based epoxy resin monomer provided by the present application has a rigid benzene ring structure in the structure, which helps to improve the thermal stability and mechanical properties of the epoxy resin, and also contains a dynamic covalent Schiff base bond, so that the epoxy resin has good surface damage repair function and reshaping function; and the bio-based epoxy resin monomer has trifunctionality, which can improve the crosslinking density of the epoxy resin.The bio-based epoxy resin monomer provided by the present application is prepared based on proto-catechuic aldehyde, has the advantages of green and non-toxic, simple synthesis method compared with commercial epoxy resin, and can reduce the consumption and dependence on petroleum chemical products.

Description

Technical Field

[0001] This invention relates to the field of bio-based epoxy resin technology, and more particularly to a trifunctional bio-based epoxy resin monomer, a bio-based epoxy resin, and its preparation and remodeling methods. Background Technology

[0002] Epoxy resin is a general term for a class of high molecular polymers containing two or more epoxy groups in their molecules. Compared with most thermosetting materials, epoxy resin has the advantages of excellent dimensional stability, high modulus, high strength, and good heat resistance and chemical resistance. It is widely used in coatings, adhesives, composite materials, electronic packaging and other fields.

[0003] Currently, common epoxy resins are mainly petroleum-based products such as bisphenol A diglycidyl ether (BPA). However, petrochemical raw materials are non-renewable and have limited storage, which is detrimental to the long-term development and application of epoxy resins.

[0004] Bio-based materials have been widely used in epoxy resin research in recent years due to their significant advantages such as environmental friendliness and biodegradability. However, current bio-based epoxy resins suffer from poor thermal stability and mechanical properties, which hinders their further widespread application. Summary of the Invention

[0005] In view of this, the present invention provides a trifunctional bio-based epoxy resin monomer, a bio-based epoxy resin, and a preparation method and a remolding method. The bio-based epoxy resin provided by the present invention has good thermal stability and mechanical properties, and also has self-healing properties. Furthermore, it is green and non-toxic, reducing the consumption of petroleum resources.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] A trifunctional bio-based epoxy resin monomer, with the structural formula shown in Formula I:

[0008]

[0009] This invention also provides a method for preparing the trifunctional bio-based epoxy resin monomer described in the above-mentioned scheme, comprising the following steps:

[0010] Vanillin amine hydrochloride, a strong base-weak acid salt, an alcohol solvent, and protocatechuic aldehyde were mixed and subjected to a condensation reaction to obtain a bisphenol monomer; the structure of the bisphenol monomer is shown in Formula II.

[0011]

[0012] The bisphenol monomer, catalyst, and epichlorohydrin are mixed and subjected to an epoxidation reaction. The resulting epoxidation reaction solution is then mixed with sodium hydroxide and benzene solvent to carry out a ring-closing reaction, thereby obtaining a trifunctional bio-based epoxy resin monomer with the structure shown in Formula I.

[0013] Preferably, the strong base weak acid salt includes one or more of potassium carbonate and sodium carbonate; the molar ratio of vanillinamine hydrochloride to the strong base weak acid salt is 1:1 to 1.5; the molar ratio of vanillinamine hydrochloride to protocatechuic aldehyde is 1:1 to 1.5.

[0014] The condensation reaction is carried out at a temperature of 60–100°C for 2–7 hours.

[0015] Preferably, the molar ratio of the bisphenol monomer to the catalyst is 1:0.001 to 0.1; the molar ratio of the bisphenol monomer to epichlorohydrin is 1:1 to 30; and the molar ratio of the bisphenol monomer to sodium hydroxide is 1:0.1 to 0.7.

[0016] Preferably, the catalyst is one or more of a quaternary ammonium salt and pyridine; the sodium hydroxide is used in the form of an aqueous solution of sodium hydroxide, the mass concentration of which is 20% to 45%.

[0017] Preferably, the epoxidation reaction is carried out at a temperature of 50–100°C for 2–7 hours; the ring-closing reaction is carried out at a temperature of 50–100°C for 2–7 hours.

[0018] The present invention also provides a bio-based epoxy resin, the raw materials for which include epoxy resin monomer, curing agent and curing catalyst, wherein the epoxy resin monomer is the trifunctional bio-based epoxy resin monomer described in the above scheme or the trifunctional bio-based epoxy resin monomer prepared by the preparation method described in the above scheme; the curing agent includes one or more of amino-containing curing agents, disulfide-containing curing agents, and amino-siloxane-silicon-containing curing agents; the curing catalyst includes one or more of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), imidazole, 2-ethyl-4-methylimidazolium and 4-dimethylaminopyridine.

[0019] Preferably, the amino-containing curing agent is 4,4'-diaminodiphenylmethane and / or hexamethylenediamine; the disulfide-containing curing agent is one or two of 4,4'-diaminodiphenyl disulfide and 3,3'-dithiodipropionic acid; and the amino-siloxane-silicon bond-containing curing agent is one or two of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and bis(4-aminophenoxy)dimethylsilane.

[0020] This invention also provides a method for preparing the bio-based epoxy resin described above, comprising the following steps:

[0021] A trifunctional bio-based epoxy resin monomer, a curing agent, and a curing catalyst are mixed and cured to obtain the cured epoxy resin. The curing process includes a first curing and a second curing, wherein the temperature of the first curing is 60–120°C and the time is 4–12 h, and the temperature of the second curing is 120–160°C and the time is 2–12 h.

[0022] This invention also provides a method for remolding bio-based epoxy resin, comprising the following steps:

[0023] The bio-based epoxy resin is pulverized and then hot-pressed and reshaped; the hot-pressing and reshaping temperature is 160-200℃, the pressure is 1-20MPa, and the time is 0.1-2h; the bio-based epoxy resin is the bio-based epoxy resin described in the above scheme or the bio-based epoxy resin prepared by the preparation method described in the above scheme.

[0024] This invention provides a trifunctional bio-based epoxy resin monomer, with the structural formula shown in Formula I. The bio-based epoxy resin monomer provided by this invention contains a rigid benzene ring structure, which helps improve the thermal stability and mechanical properties of the epoxy resin. Simultaneously, the monomer structure contains dynamic covalent Schiff base bonds, giving the epoxy resin good surface damage repair capabilities. Furthermore, the bio-based epoxy resin provided by this invention has trifunctionality, which can increase the degree of crosslinking of the epoxy resin, forming a more complex and dense crosslinked network structure, thereby improving the mechanical properties of the epoxy resin. The bio-based epoxy resin provided by this invention is prepared based on protocatechuic aldehyde, which is derived from the roots, stems, and leaves of plants. It is widely available, green, non-toxic, and a renewable bio-based material, which can reduce the consumption and dependence on petrochemical products and promote the sustainable development of the epoxy resin industry.

[0025] The present invention also provides a method for preparing the trifunctional bio-based epoxy resin monomer described in the above scheme. The preparation method provided by the present invention has simple steps and high yield. Attached Figure Description

[0026] Figure 1 The image shows the 1H NMR spectrum of the bisphenol monomer synthesized in Example 1.

[0027] Figure 2 The infrared spectrum of the bisphenol monomer synthesized in Example 1 is shown below.

[0028] Figure 3 The mass spectrum of the bisphenol monomer synthesized in Example 1 is shown below.

[0029] Figure 4 The 1H NMR spectrum of the trifunctional bio-based epoxy resin monomer synthesized in Example 2;

[0030] Figure 5The infrared spectrum of the bio-based epoxy resin obtained after curing in Example 3;

[0031] Figure 6 A diagram showing the hot-press remodeling of bio-based epoxy resin;

[0032] Figure 7 Stress-strain curves of bio-based epoxy resins;

[0033] Figure 8 The images show the self-healing properties of bio-based epoxy resin, with a scale bar of 75 μm. Detailed Implementation

[0034] This invention provides a trifunctional bio-based epoxy resin monomer with the structural formula shown in Formula I:

[0035]

[0036] This invention also provides a method for preparing the trifunctional bio-based epoxy resin monomer described in the above-mentioned scheme, comprising the following steps:

[0037] Vanillin amine hydrochloride, a strong base-weak acid salt, an alcohol solvent, and protocatechuic aldehyde were mixed and subjected to a condensation reaction to obtain a bisphenol monomer; the structure of the bisphenol monomer is shown in Formula II.

[0038]

[0039] The bisphenol monomer, catalyst, and epichlorohydrin are mixed and subjected to an epoxidation reaction. The resulting epoxidation reaction solution is then mixed with sodium hydroxide and benzene solvent to carry out a ring-closing reaction, thereby obtaining a trifunctional bio-based epoxy resin monomer with the structure shown in Formula I.

[0040] This invention involves a condensation reaction of vanillinamine hydrochloride, a strong base-weak acid salt, an alcohol solvent, and protocatechuic aldehyde to obtain a bisphenol monomer (PCA-AM). The reaction formula for the condensation reaction in this invention is as follows:

[0041]

[0042] In this invention, the strong base-weak acid salt includes one or more of potassium carbonate and sodium carbonate; the molar ratio of vanillinamine hydrochloride to the strong base-weak acid salt is preferably 1:1 to 1.5, specifically 1:1.05; the molar ratio of vanillinamine hydrochloride to protocatechuic aldehyde is preferably 1:1 to 1.5, specifically 1:1.05; the alcohol solvent is preferably methanol. Protocatechuic aldehyde is derived from the roots, stems, and leaves of plants, has a wide range of sources, and chemically possesses a rigid aromatic ring structure and aldehyde group. Through condensation reaction with amino groups, bisphenol monomers containing dynamic covalent bonds are synthesized, resulting in epoxy resins with better self-healing or remodeling properties.

[0043] In this invention, the temperature of the condensation reaction is preferably 60–100°C, specifically 60°C, 70°C, 80°C, 90°C, or 100°C. In a specific embodiment of this invention, the condensation reaction is preferably carried out under reflux conditions, and the reaction time is preferably 2–7 hours, specifically 3 hours, 4 hours, 5 hours, or 6 hours. Under the above conditions, this invention promotes the efficient conduction of the condensation reaction.

[0044] In a specific embodiment of the present invention, vanillin amine hydrochloride and protocatechuic aldehyde are preferably dissolved in an alcohol solvent to obtain vanillin amine hydrochloride solution and protocatechuic aldehyde solution, respectively. Potassium carbonate is added to the vanillin amine hydrochloride solution, and after stirring at 50°C for 30 min, the protocatechuic aldehyde solution is added dropwise to the system. After the addition is complete, a condensation reaction is carried out under reflux conditions. The concentration of vanillin amine hydrochloride in the vanillin amine hydrochloride solution is preferably 2 mol / L, and the concentration of protocatechuic aldehyde in the protocatechuic aldehyde solution is preferably 3 mol / L.

[0045] After the condensation reaction is completed, the present invention preferably filters the obtained reaction solution, washes the obtained solid product with methanol and dries it to obtain the bisphenol monomer.

[0046] After obtaining the bisphenol monomer, the present invention mixes the bisphenol monomer, catalyst and epichlorohydrin to carry out an epoxidation reaction, and mixes the obtained epoxidation reaction solution with sodium hydroxide and benzene solvent to carry out a ring-closing reaction to obtain a trifunctional bio-based epoxy resin monomer with the structure shown in Formula I.

[0047] In this invention, the reaction processes of the epoxidation reaction and the ring-closing reaction are collectively represented as follows:

[0048]

[0049] In this invention, the molar ratio of the bisphenol monomer to the catalyst is preferably 1:0.001 to 0.1, specifically 1:0.02, 1:0.03, 1:0.04, 1:0.06, or 1:0.08; the catalyst is preferably one or more of a quaternary ammonium salt and pyridine; the quaternary ammonium salt preferably includes one or more of tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium iodide, and hexadecyltrimethylammonium bromide. The above-mentioned catalyst in this invention can promote the reaction, accelerate the reaction rate, and improve selectivity.

[0050] In this invention, the molar ratio of the bisphenol monomer to epichlorohydrin is preferably 1:10 to 30, specifically 1:10, 1:15, 1:20, 1:25, or 1:30; the molar ratio of the bisphenol monomer to sodium hydroxide is preferably 1:0.1 to 0.7, specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, or 1:0.7; the sodium hydroxide is used in the form of an aqueous solution, the mass concentration of which is preferably 20% to 45%, specifically 40%; the sodium hydroxide solution is preferably added dropwise. The benzene solvent is preferably toluene, and the molar ratio of the bisphenol monomer to toluene is preferably 1:10 to 20.

[0051] In this invention, the temperature of the epoxidation reaction is preferably 50-100°C, specifically 80°C, and the time is preferably 2-7 hours, specifically 6 hours. After the epoxidation reaction is completed, the resulting reaction solution is preferably distilled under reduced pressure to remove excess epichlorohydrin from the system, and then benzene solvent and sodium hydroxide aqueous solution are added to carry out the ring-closing reaction.

[0052] In this invention, the temperature of the closed-loop reaction is preferably 50-100°C, specifically 90°C, and the time of the closed-loop reaction is preferably 2-7 hours, specifically 3 hours, 4 hours, 5 hours or 6 hours.

[0053] After the closed-loop reaction is completed, the present invention preferably cools the obtained reaction solution to room temperature, then washes it with deionized water until neutral, and then dries and purifies the washed solution by vacuum distillation and column chromatography to obtain the trifunctional bio-based epoxy resin monomer; the eluent used for column chromatography purification is preferably petroleum ether.

[0054] The present invention also provides a bio-based epoxy resin, the raw materials for which include epoxy resin monomer, curing agent and curing catalyst, wherein the epoxy resin monomer is the trifunctional bio-based epoxy resin monomer described in the above scheme or the trifunctional bio-based epoxy resin monomer prepared by the preparation method described in the above scheme; the curing agent includes one or more of amino-containing curing agents, disulfide bond-containing curing agents, and amino-siloxane-silicon bond-containing curing agents.

[0055] In this invention, the amino-containing curing agent is preferably 4,4'-diaminodiphenylmethane and / or hexamethylenediamine; the disulfide-containing curing agent is preferably one or two of 4,4'-diaminodiphenyl disulfide and 3,3'-dithiodipropionic acid; and the amino-siloxane-silicon bond-containing curing agent is preferably one or two of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and bis(4-aminophenoxy)dimethylsilane.

[0056] In this invention, the molar ratio of the trifunctional bio-based epoxy resin monomer and the curing agent is preferably 1:0.5 to 2, and more specifically, it can be 1:0.75.

[0057] In this invention, the curing catalyst comprises one or more of 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), imidazole, 2-ethyl-4-methylimidazolium, and 4-dimethylaminopyridine, more preferably TBD; the molar ratio of the trifunctional bio-based epoxy resin monomer to the curing catalyst is preferably 1:0.01 to 0.1. Taking TBD as an example, the working principle of the curing agent catalyst in this invention is explained as follows: In the presence of an alcohol group, the secondary amine hydrogen ions on TBD can combine with silicon or oxygen atoms in the siloxane, causing a change in the electron cloud distribution of the silicon-oxygen bond, weakening the bond strength, making it easier for the bond to break and recombine, thereby promoting the dynamic exchange reaction.

[0058] This invention also provides a method for preparing the bio-based epoxy resin described above, comprising the following steps:

[0059] The trifunctional bio-based epoxy resin monomer, curing agent and curing catalyst are mixed and cured to obtain the epoxy resin cured product.

[0060] In this invention, the curing includes sequentially performing a first curing and a second curing. The temperature of the first curing is 60-120°C and the time is 4-12 hours. The temperature of the second curing is 120-160°C and the time is 2-12 hours.

[0061] In this invention, the trifunctional bio-based epoxy resin monomer, curing agent and curing catalyst are first stirred and mixed evenly, then degassed under vacuum, and then poured into a mold for curing.

[0062] In this invention, taking 1,3-bis(3-aminopropyl)tetramethyldisiloxane (Bas) as the curing agent as an example, the structure of the bio-based epoxy resin obtained after curing is shown in Formula III:

[0063]

[0064] This invention also provides a method for remolding bio-based epoxy resin, comprising the following steps:

[0065] The bio-based epoxy resin is pulverized and then hot-pressed and reshaped; the bio-based epoxy resin is the bio-based epoxy resin described in the above scheme or the bio-based epoxy resin prepared by the preparation method described in the above scheme.

[0066] In this invention, the temperature of the hot pressing and reshaping is 160-200°C, specifically 200°C; the pressure is 1-20 MPa, specifically 5 MPa, 8 MPa, 10 MPa, 15 MPa or 20 MPa; and the time is 0.1-2 h, specifically 0.5 h, 1 h, 1.5 h or 2 h.

[0067] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0068] Example 1

[0069] In a three-necked round-bottom flask equipped with a thermometer and a reflux condenser, at a temperature of 50°C, vanillinamine hydrochloride (37.93 g, 0.2 mol) was dissolved in 100 mL of methanol under magnetic stirring, and solid K₂CO₃ (27.64 g, 0.21 mmol) was added. The mixture was stirred at 50°C for 30 min. Protocatechuic aldehyde (29 g, 0.21 mol) was dissolved in 70 mL of methanol and then added dropwise to the reaction system. The entire mixture was refluxed for 4 h. After the reaction was complete, a yellow powder was obtained by filtration, washed three times with methanol, and dried overnight to obtain the bisphenol monomer (PCA-AM).

[0070] The 1H NMR spectrum of the obtained bisphenol monomer is as follows: Figure 1 As shown, the infrared spectrum is as follows Figure 2 As shown, the mass spectrometry is as follows Figure 3 As shown; according to Figure 1 It can be seen that the appearance of the signal peak at position f represents the successful synthesis of the imine bond; according to Figure 2 It can be seen that: 3200cm -1 The peak at 1645 cm⁻¹ is attributed to the characteristic absorption peak of hydroxyl groups. -1 The characteristic peak representing the imine bond indicates the successful synthesis of the bisphenol monomer; according to Figure 3 As can be seen, the relative molecular mass of the bisphenol monomer is consistent with the expected molecular weight. These results indicate that the bisphenol monomer prepared in this embodiment possesses the target structure.

[0071] Example 2

[0072] In a three-necked flask equipped with a mechanical stirrer and a condenser, 20 g of the bisphenol monomer prepared in Example 1, 160 mL of epichlorohydrin (equivalent to 2 mol of epichlorohydrin), and 2 g of tetrabutylammonium bromide catalyst (equivalent to 0.0062 mol of tetrabutylammonium bromide) were added and thoroughly mixed. The temperature was raised to 80 °C and the reaction was continued for 6 h. Heating was stopped, and excess epichlorohydrin in the system was removed by vacuum distillation. After the epichlorohydrin was completely removed, 100 mL of toluene (equivalent to 0.95 mol of toluene) and 4.8 g of sodium hydroxide aqueous solution (40% by mass) were added to the reaction system, and the mixture was heated to 90 °C and the reaction was continued for 3 h. After the reaction was completed, the system was cooled to room temperature and the reaction solution was washed repeatedly with deionized water until neutral. The washed product was then subjected to vacuum distillation to remove toluene and water, and then purified by drying and column chromatography to obtain a reddish-brown viscous liquid, which is the trifunctional bio-based epoxy resin monomer (PCA-AM-EP) with the structure shown in Formula I.

[0073] The 1H NMR spectrum of the obtained trifunctional bio-based epoxy resin monomer is as follows: Figure 4 As shown; according to Figure 4 It can be seen that the position of 7-7.6 ppm is the hydrogen resonance peak in the benzene ring structure. The successful synthesis of PCA-AM-EP can be confirmed by the analysis of 1H NMR.

[0074] Example 3

[0075] The preparation of bio-based epoxy resin involves three raw materials: component A, component B, and component C. Component A is the trifunctional bio-based epoxy resin monomer prepared in Example 2. Component B is the curing agent 1,3-bis(3-aminopropyl)tetramethyldisiloxane (Bas), and component C is the curing catalyst TBD. The molar ratio of component A to component B is 1:0.75, and the molar ratio of component C to component D is 1:0.05. The specific preparation process of the bio-based epoxy resin is as follows: First, component A is added to a 25mL beaker and placed at room temperature. After thorough stirring, the weighed curing agent and TBD are added and stirred for 10 minutes to ensure uniform mixing. Then, the mixture is degassed under vacuum in a vacuum oven at room temperature for 10 minutes. Afterward, the mixture is poured into a mold and cured at 60℃ for 12 hours, followed by curing at 120℃ for 4 hours to obtain the bio-based epoxy resin (PCA-AM-EP / Bas).

[0076] The infrared spectrum of the obtained bio-based epoxy resin is shown below. Figure 5 As shown, according to Figure 5 It can be seen that: in the infrared spectrum, 3200 cm⁻¹ -1 The characteristic peak at 910 cm⁻¹ belongs to the hydroxyl group in PCA-AM-EP / Bas. -1 The characteristic peak at 1270 cm⁻¹ belonging to the epoxy group in PCA-AM-EP disappears. -1The characteristic peak belonging to CN in PCA-AM-EP / Bas appeared at this location.

[0077] Example 4

[0078] The bio-based epoxy resin obtained in Example 3 was tested for its hot-pressing remolding performance, tensile properties, and self-healing properties, as detailed below.

[0079] I. Hot-press reshaping experiment

[0080] The PCA-AM-EP / Bas cured sample obtained in Example 3 was pulverized in a pulverizer to obtain broken epoxy resin, which was then hot-pressed in a hot press at a temperature of 200°C, a pressure of 10 MPa, and a time of 60 min. Figure 6 As shown, the powder of the bio-based epoxy resin cured sample was hot-pressed and reshaped at 200°C, and then re-hot-pressed into a sheet after 60 minutes. These results indicate that the present invention introduces multiple dynamic bonds into the epoxy resin and increases the content of dynamic bonds, which helps to achieve reprocessing of the bio-based epoxy resin cured sample at a lower temperature.

[0081] II. Stress-Strain Tension Test

[0082] Dumbbell-shaped cured specimens of the bio-based epoxy resin prepared in Example 3 were subjected to tensile testing at room temperature using an electronic universal testing machine. The tensile strength TS was calculated according to formula (A), in MPa:

[0083]

[0084] In formula (A): F m The maximum force recorded is N; W is the width of the narrow section of the sample, mm; t is the sample thickness, mm.

[0085] Figure 7 This is the tensile stress-strain curve of bio-based epoxy resin. (Example:) Figure 7 As shown, the bio-based epoxy resin provided by this invention has a tensile strength of 50.1 MPa and an elongation at break of 11.5%. Due to the presence of numerous rigid structures such as aromatic rings in the epoxy network, this bio-based epoxy resin exhibits high mechanical strength, and its mechanical properties are comparable to those of commercial epoxy resins, thus meeting the requirements for use as a structural material.

[0086] III. Self-repair capability

[0087] A linear scratch was made on the surface of the bio-based epoxy resin cured strip prepared in Example 3 using a blade. A self-healing experiment was then conducted at 200°C. The self-healing behavior of the bio-based epoxy resin cured strip at 200°C was observed using a polarizing microscope. The results are as follows: Figure 8As shown, the width of the scratch before repair was 19.42 μm. After repairing at 200℃ for 20 minutes, the width of the straight scratch was only 9.71 μm. After 40 minutes, the straight scratch was almost completely repaired, and after 60 minutes, it was completely repaired. Combined with... Figure 8 Using the crack width and the self-healing rate calculation formula shown in Equation (B), the self-healing rate of the bio-based epoxy resin cured specimens under different heating times was calculated, and the results are shown in Table 1:

[0088]

[0089] In equation (B), W1 is the crack width after heating, in μm; W0 is the initial crack width, in μm.

[0090] Table 1 Self-healing rate of bio-based epoxy resin cured samples after heating

[0091]

[0092] As shown in Table 1, the bio-based epoxy resin PCA-AM-EP / Bas containing dual dynamic bonds (Si-O-Si and C=N) has good self-healing properties.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A trifunctional bio-based epoxy resin monomer, characterized in that, The structural formula is shown in Formula I: Equation I.

2. The method for preparing the trifunctional bio-based epoxy resin monomer according to claim 1, characterized in that, Includes the following steps: Vanillin amine hydrochloride, a strong base-weak acid salt, an alcohol solvent, and protocatechuic aldehyde were mixed and subjected to a condensation reaction to obtain a bisphenol monomer; the structure of the bisphenol monomer is shown in Formula II. Formula II; The bisphenol monomer, catalyst, and epichlorohydrin are mixed and subjected to an epoxidation reaction. The resulting epoxidation reaction solution is then mixed with sodium hydroxide and benzene solvent to carry out a ring-closing reaction, thereby obtaining a trifunctional bio-based epoxy resin monomer with the structure shown in Formula I.

3. The preparation method according to claim 2, characterized in that, The strong base weak acid salt is selected from one or more of potassium carbonate and sodium carbonate; the molar ratio of vanillinamine hydrochloride to the strong base weak acid salt is 1:1 to 1.5; the molar ratio of vanillinamine hydrochloride to protocatechuic aldehyde is 1:1 to 1.

5. The condensation reaction is carried out at a temperature of 60-100℃ for 2-7 hours.

4. The preparation method according to claim 2, characterized in that, The molar ratio of bisphenol monomer to catalyst is 1:0.001~0.1; the molar ratio of bisphenol monomer to epichlorohydrin is 1:10~30; and the molar ratio of bisphenol monomer to sodium hydroxide is 1:0.1~0.

7.

5. The preparation method according to claim 2, characterized in that, The catalyst is one or more of quaternary ammonium salt and pyridine; the sodium hydroxide is used in the form of an aqueous sodium hydroxide solution with a mass concentration of 20% to 45%.

6. The preparation method according to claim 2, characterized in that, The epoxidation reaction is carried out at a temperature of 50-100℃ for 2-7 hours; the ring-closing reaction is carried out at a temperature of 50-100℃ for 2-7 hours.

7. A bio-based epoxy resin, characterized in that, The raw materials for preparation include epoxy resin monomers, curing agents, and curing catalysts. The epoxy resin monomer is the trifunctional bio-based epoxy resin monomer as described in claim 1 or the trifunctional bio-based epoxy resin monomer prepared by the preparation method described in any one of claims 2 to 6. The curing agent is selected from one or more of amino-containing curing agents, disulfide-containing curing agents, and amino-siloxane-silicon-containing curing agents. The curing catalyst is selected from one or more of 1,5,7-triazabicyclo[4.4.0]dec-5-ene, imidazole, 2-ethyl-4-methylimidazolium, and 4-dimethylaminopyridine.

8. The bio-based epoxy resin according to claim 7, characterized in that, The amino-containing curing agent is 4,4'-diaminodiphenylmethane and / or hexamethylenediamine; the disulfide-containing curing agent is one or two of 4,4'-diaminodiphenyl disulfide and 3,3'-dithiodipropionic acid; the amino-siloxane-silicon bond-containing curing agent is one or two of 1,3-bis(3-aminopropyl)tetramethyldisiloxane and bis(4-aminophenoxy)dimethylsilane.

9. The method for preparing the bio-based epoxy resin according to claim 7 or 8, characterized in that, Includes the following steps: The bio-based epoxy resin is obtained by mixing and curing a trifunctional bio-based epoxy resin monomer, a curing agent and a curing catalyst; the curing includes a first curing and a second curing in sequence, wherein the temperature of the first curing is 60~120℃ and the time is 4~12h, and the temperature of the second curing is 120~160℃ and the time is 2~12h.

10. A method for remolding bio-based epoxy resin, characterized in that, Includes the following steps: The bio-based epoxy resin is pulverized and then hot-pressed and remolded; the hot-pressing and remolding temperature is 160~200℃, the pressure is 1~20MPa, and the time is 0.1~2h; the bio-based epoxy resin is the bio-based epoxy resin according to claim 7 or 8 or the bio-based epoxy resin prepared by the preparation method according to claim 9.

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