A method for preparing and recycling high-performance degradable epoxy resin

Abstract

The present invention discloses a preparation method and degradation recovery method of a high-performance degradable and recyclable epoxy resin, which belongs to the field of epoxy resin technology. A high-performance degradable and recyclable epoxy resin is prepared from the following raw materials: p-aminophenol, vanillin, epichlorohydrin, bisphenol A epoxy resin, a curing agent, a catalyst, tetrabutylammonium bromide, and a sodium hydroxide solution. The high-performance degradable and recyclable vanillin-based epoxy resin provided by the present invention has strong reaction activity, low curing temperature, and an initial curing temperature below 100°C; good heat resistance, and a glass transition temperature of up to 159°C; excellent electrical insulation performance and mechanical properties, a dielectric loss factor of only 0.34, and a tensile strength of up to 76MPa; degradation can be achieved under the conditions of 100°C within 25h; the degraded solution and the crushed epoxy resin can be hot-pressed and recycled, and the electrical breakdown strength recovery rate can reach up to 98%; it has surface self-repairing ability, and scratches disappear when kept at 180°C for 60-180min.

Description

Technical Field

[0001] The present invention relates to the technical field of epoxy resins, and in particular to a method for preparing a high-performance degradable and recyclable epoxy resin and a degradation and recycling method. Background Art

[0002] Epoxy resin (EP) is a three-dimensional cross-linked polymer material with excellent bonding strength, thermal stability, mechanical properties, weather resistance and electrical insulation properties. It is widely used in electrical applications such as composite insulation materials, electronic component packaging, dry-type reactors and dry-type transformers. Currently, more than 90% of epoxy resins on the market are bisphenol A diglycidyl ether (DGEBA), which is a petroleum-based compound. While consuming a large amount of petrochemical resources, it also causes large carbon emissions and environmental pollution. With the intensification of the global energy crisis and the deterioration of the environment, the development of bio-based epoxy resins that can replace or partially replace DGEBA using environmentally friendly and renewable resources as raw materials has become one of the important ways to achieve environmental protection of epoxy electrical equipment.

[0003] Bio-based epoxy resins are thermosetting epoxy resins produced through epoxidation using renewable resources as raw materials. Researchers at home and abroad are currently conducting extensive research on the synthesis and application of bio-based epoxy resins, including rosin, vanillin, itaconic acid, and isosorbide. Some bio-based epoxy resins produced are comparable to traditional bisphenol A epoxy resins in terms of thermal insulation properties. However, the three-dimensional cross-linked network formed after curing is insoluble and infusible, making it difficult to efficiently degrade and recycle. This results in a waste of retired equipment resources and causes serious environmental pollution.

[0004] Vanillin, also known as vanillin, chemically known as 3-methoxy-4-hydroxybenzaldehyde, is an organic compound extracted from the vanilla bean of the Rutaceae family. It is an important broad-spectrum, high-end spice, one of the world's largest spices by production as of 2019, and one of the most widely used food flavoring agents, earning it the title of "King of Food Flavors." Vanillin occurs as white to slightly yellowish crystals or a crystalline powder, is slightly sweet, and is soluble in hot water, glycerin, and alcohol. It is insoluble in cold water and vegetable oils, is easily oxidized in air, and discolors easily when exposed to alkaline substances. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-performance biodegradable and recyclable epoxy resin preparation and degradation and recycling method, so as to provide a bio-based epoxy resin with a wide range of material sources, performance comparable to traditional bisphenol A epoxy resin, but can be degraded and recycled, so as to reduce resource waste and environmental pollution problems caused by traditional epoxy resins.

[0006] To achieve the above objectives, the present invention provides a method for preparing a high-performance degradable and recyclable epoxy resin and a degradation and recycling method. The high-performance degradable and recyclable epoxy resin is prepared from the following raw materials:

[0007] p-Aminophenol, vanillin, epichlorohydrin, bisphenol A epoxy resin, curing agent, catalyst, tetrabutylammonium bromide, sodium hydroxide solution.

[0008] Preferably, the catalyst is 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, the curing agent is 2-methylhexahydrophthalic anhydride, the bisphenol A epoxy resin is E-51 bisphenol A epoxy resin, and the mass fraction of the sodium hydroxide solution is 20%.

[0009] Preferably, the molar ratio of p-aminophenol:vanillin:epichlorohydrin is 1:1:10.

[0010] A method for preparing the high-performance biodegradable and recyclable epoxy resin as described above comprises the following steps:

[0011] S1. Vanillin and p-aminophenol were dissolved in deionized water and anhydrous ethanol, respectively, and then poured into a round-bottom flask equipped with a condenser. The mixture was reacted under certain conditions, and then vacuum filtered. After completion, the mixture was washed three times with anhydrous ethanol and dried to obtain a purified yellow powder, which is a vanillin-based diphenol monomer. The reaction formula is:

[0012] S2. Place a round-bottom flask equipped with a condenser reflux and magnetic stirring device in an oil bath, then add the vanillin-based diphenol monomer and epichlorohydrin obtained in step S1 to the round-bottom flask, start stirring, and add tetrabutylammonium bromide after all components are dissolved. Then, raise the system to a certain temperature and maintain it for a certain period of time.

[0013] S3. Slowly dropwise add 20% by mass of sodium hydroxide to the reaction system, cool the reaction system to the desired temperature, and react for a certain period of time. Then, vacuum filter the resulting product, dilute it with petroleum ether, and wash it with distilled water. Extract it three times, remove excess epichlorohydrin and petroleum ether using a rotary evaporator, and vacuum dry it overnight. The resulting white solid is a vanillin-based epoxy monomer, and the reaction formula is:

[0014]

[0015] S4. At 110° C., evenly mix E-51 bisphenol A epoxy resin and the vanillin-based epoxy monomer obtained in step S3, then add a curing agent. After all components are melted and mixed evenly, add a catalyst, mix evenly again, place in a vacuum oven for degassing, and cure in a stepwise curing manner of 100° C. / 2 h + 130° C. / 5 h.

[0016] Preferably, in step S1, 1 mol of vanillin is dissolved in 4 L of deionized water, and 1 mol of p-aminophenol is dissolved in 2 L of anhydrous ethanol; the certain condition refers to stirring under reflux at 50° C.-60° C. for 2-3 hours; and drying in a vacuum drying oven at 50° C.-65° C. overnight.

[0017] Preferably, in step S2, the amount of tetrabutylammonium bromide added is 10% of the mass of the vanillin diphenol monomer, and the system is raised to a certain temperature and maintained for a certain time, which means raising the system to 80°C-90°C and reacting for 1.5-3 hours; in step S4, the molar ratio of bisphenol A epoxy resin: the prepared vanillin epoxy resin is 1:1.

[0018] Preferably, in step S3, slowly adding 20% sodium hydroxide by mass means that the addition is completed within 0.5 h, the amount of 20% sodium hydroxide is twice the mass of the vanillin diphenol monomer, and reducing the temperature to the required temperature and reacting for a certain time means reducing the temperature to room temperature and reacting for 3-5 h; the amount of petroleum ether added is 20 times the mass of the vanillin diphenol monomer; and vacuum drying is drying in a vacuum drying oven at 50°C-70°C overnight.

[0019] A degradation method for the high-performance biodegradable and recyclable epoxy resin as described above is achieved by placing the epoxy resin in a degradation liquid, wherein the mass ratio of epoxy resin to degradation liquid is 1:20, and the degradation liquid is n-hexylamine.

[0020] A method for recycling the high-performance biodegradable epoxy resin as described above can be performed by a chemical recycling method or a physical recycling method. The steps of the chemical recycling method are as follows:

[0021] The prepared vanillin-based epoxy resin was dissolved in the degradation solution, and the system was placed in a rotary evaporator. After the solution became viscous, the system was transferred to a mold, vacuum-heated, and continuously hot-pressed at 180°C and 10 MPa for 6 hours. The system was then cooled naturally and demolded when it cooled to room temperature to obtain the recovered vanillin-based epoxy resin.

[0022] The physical recovery method is as follows: the vanillin-based epoxy resin is crushed into particles with a diameter of 1-5 mm using a grinder, placed in two steel plate molds coated with release oil, hot pressed on a flat plate vulcanizer at 200°C and 20 MPa for 4 hours, and formed after cooling to room temperature, and demolded to obtain a recycled sample.

[0023] Therefore, the present invention provides a method for preparing a high-performance biodegradable and recyclable epoxy resin and a method for degradation and recycling, and its specific technical effects are as follows:

[0024] (1) The high-performance, biodegradable, and recyclable vanillin-based epoxy resin provided by the present invention has strong reactivity, a low curing temperature, and an initial curing temperature below 100°C; good heat resistance, with a glass transition temperature as high as 159°C; excellent electrical insulation and mechanical properties, a dielectric loss factor of only 0.34, and a maximum tensile strength of up to 76 MPa;

[0025] (2) The high-performance, biodegradable and recyclable vanillin-based epoxy resin provided by the present invention can be degraded at 100°C within 25 hours; the degraded solution and crushed epoxy resin can be hot-pressed and recycled, with a maximum electrical breakdown strength recovery rate of 98%;

[0026] (3) The high-performance, biodegradable and recyclable vanillin-based epoxy resin provided by the present invention is prepared by preparing a vanillin-based glassy epoxy resin containing an intrinsic imine bond, so that the vanillin-based epoxy resin has surface self-repairing ability. When kept at 180°C for 3 hours, the scratches disappear, and the best scratches disappear in 60 minutes.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0029] Figure 1 This is the synthesis process of the epoxy resin of the present invention;

[0030] Figure 2 The curing temperature curves of the epoxy resin prepared in the present invention and the commercially available bisphenol A epoxy resin are shown in FIG. 1 , wherein part (a) is the curing temperature curve of Van-0, part (b) is the curing temperature curve of Van-0.25, part (c) is the curing temperature curve of Van-0.5, part (d) is the curing temperature curve of Van-0.75, and part (f) is the curing temperature curve of Van-1. Ti is the starting curing temperature, Tp is the peak curing temperature, and Te is the ending curing temperature.

[0031] Figure 3 DMA curves of the epoxy resin prepared in the present invention and commercially available bisphenol A epoxy resin;

[0032] Figure 4 The mechanical property curves of the epoxy resin prepared by the present invention and the commercially available bisphenol A epoxy resin are shown below:

[0033] Figure 5 The TGA curves of the epoxy resin prepared by the present invention and the commercially available bisphenol A epoxy resin are shown below:

[0034] Figure 6 The electrical performance curves of the epoxy resin prepared by the present invention and the commercially available bisphenol A epoxy resin are shown below:

[0035] Figure 7 These are degradation images of the epoxy resin prepared in the present invention and commercially available bisphenol A epoxy resin, where Part A shows the epoxy resin immediately after being added to n-hexylamine, and Part B shows the epoxy resin after 25 hours of degradation.

[0036] Figure 8 Degradation curves of the epoxy resin prepared by the present invention and commercially available bisphenol A epoxy resin;

[0037] Figure 9 The recovery performance curves of the epoxy resin prepared by the present invention and the commercially available bisphenol A epoxy resin are shown below:

[0038] Figure 10 Figure 3 shows the self-healing process of the epoxy resin prepared in the present invention and commercially available bisphenol A epoxy resin. Part (a) shows the scratches on Van-0 at different times, part (b) shows the scratches on Van-0.25 at different times, part (c) shows the scratches on Van-0.5 at different times, part (d) shows the scratches on Van-0.75 at different times, and part (e) shows the scratches on Van-1 at different times. DETAILED DESCRIPTION

[0039] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0040] In order to make the purpose, technical solutions and advantages of the present application clearer, more thorough and more complete, the technical solutions of the present invention are clearly and completely described below through the accompanying drawings and Examples. The following detailed description is an explanation of the embodiments and is intended to provide further details of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as those generally understood by those skilled in the art to which the application belongs.

[0041] The instruments, equipment, reagents and materials used in the examples were obtained from commercial sources.

[0042] Example 1

[0043] The steps for synthesizing vanillin epoxy monomer are as follows:

[0044] (1) Dissolve 15.2 g of vanillin (0.1 mol) and 10.9 g of p-aminophenol (0.1 mol) in 400 mL of deionized water and 200 mL of anhydrous ethanol, respectively, and pour into a round-bottom flask equipped with a condenser. The mixed solution is refluxed and stirred at 50°C for 2 h, vacuum filtered at room temperature, and finally washed three times with anhydrous ethanol. Dry overnight in a vacuum drying oven at 60°C to obtain a purified yellow powder, which is vanillin-based diphenol monomer (DV). According to the formula: Yield = actual mass of product obtained / mass of product that should be obtained after complete reaction × 100%, the yield is calculated to be 90%.

[0045] (2) A 500 mL round-bottom flask equipped with a reflux and magnetic stirring device was placed in an oil bath, and 24.3 g of DV (0.1 mol) and 92 g (1 mol) of epichlorohydrin were added. After stirring and dissolving, 2.43 g of tetrabutylammonium bromide (10% of the mass of DV) was added. The reaction temperature was gradually raised from room temperature to 85°C, and stirring was maintained for 2 h. Subsequently, 50 g of a 20% sodium hydroxide solution was added dropwise to the mixture over 0.5 h, stirring was maintained, and the temperature of the reaction system was cooled to room temperature, and stirring was continued for 4 h. The resulting product was vacuum filtered, diluted with 480 g of petroleum ether, washed with distilled water, and extracted three times. The excess epichlorohydrin and petroleum ether were removed using a rotary evaporator. Finally, the product was vacuum dried at 60°C overnight to obtain a white solid, which was vanillin-based epoxy monomer (EDV). According to the formula: yield = actual product mass obtained / product mass obtained after complete reaction × 100%, the yield was calculated to be 60%.

[0046] Example 2

[0047] A curable epoxy resin (Van-1) with a 100% biodegradable and recyclable vanillin content was prepared as follows:

[0048] Start stirring, melt and mix 10 g of EDV and 4.5 g of 2-methylhexahydrophthalic anhydride (MHHPA) at 110° C., then add 0.29 g of 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole and mix evenly to obtain a prepolymer. Then, pour the mixture into a mold (with a specification of 10 mm × 10 mm × 1 mm) in a conventional manner and cure it at 100° C. / 2 h + 130° C. / 5 h. After curing, cool the mixture naturally to room temperature to obtain a biodegradable and recyclable cured epoxy resin Van-1 with a vanillin content of 100%.

[0049] Example 3

[0050] A curable epoxy resin (Van-0.75) with a biodegradable and recyclable vanillin content of 75% was prepared as follows:

[0051] With stirring started, 9 g of EDV, 2.8 g of E-51 bisphenol A epoxy resin (DG EBA), 5.4 g of MHHPA, and 0.35 g of 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole were mixed and stirred at 110° C. to obtain a prepolymer. The prepolymer was then poured into a mold (10 mm × 10 mm × 1 mm) and cured at 100° C. for 2 h followed by 130° C. for 5 h. After the curing was completed, the prepolymer was naturally cooled to room temperature to obtain a biodegradable and recyclable cured epoxy resin Van-0.75 having a vanillin content of 75%. The preparation reaction formula is shown in FIG. Figure 1 .

[0052] Example 4

[0053] A curable epoxy resin (Van-0.5) with a 50% biodegradable and recyclable vanillin content was prepared as follows:

[0054] At 110°C, 7g EDV, 6.6g DGEBA, 6.3g MHHPA, and 0.4g 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole were mixed and stirred uniformly to obtain a prepolymer, which was then poured into a mold (with specifications of 10mm×10mm×1mm) as usual and cured using a process of 100°C / 2h+130°C / 5h. After curing, the mixture was naturally cooled to room temperature to obtain a biodegradable and recyclable cured epoxy resin Van-0.5 with a vanillin content of 50%.

[0055] Example 5

[0056] A curable epoxy resin (Van-0.25) with a biodegradable and recyclable vanillin content of 25% was prepared as follows:

[0057] At 110°C, 3g EDV, 8.5g DGEBA, 5.4g MHHPA, and 0.33g 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole were mixed and stirred uniformly to obtain a prepolymer, which was then poured into a mold (with specifications of 10mm×10mm×1mm) as usual and cured using a process of 100°C / 2h+130°C / 5h. After curing, the mixture was naturally cooled to room temperature to obtain a biodegradable and recyclable cured epoxy resin Van-0.25 with a vanillin content of 25%.

[0058] Comparative Example 1

[0059] Preparation of traditional bisphenol A epoxy resin (Van-0) is as follows:

[0060] At 110°C, 10g of DGEBA, 4.7g of MHHPA, and 0.3g of 2,4,6-tris(dimethylaminomethyl)phenol were mixed and stirred uniformly to obtain a prepolymer, which was then poured into a mold in a conventional manner and cured using a process of 100°C / 2h+130°C / 5h. After curing, the mixture was naturally cooled to room temperature to obtain a commercially available bisphenol A epoxy resin Van-0.

[0061] Effect Example 1

[0062] The curing kinetics, thermal stability, dynamic mechanical properties, electrical properties, and self-repairing properties of the epoxy resins prepared in Examples 1 to 5 and Comparative Example 1 were investigated as follows:

[0063] DSC test: DSC3500 was used to study the curing kinetics. 5 mg of sample was placed in an aluminum crucible with a nitrogen flow rate of 20 mL / min, a starting temperature of 25°C, and an ending temperature of 250°C. To determine the optimal curing process for different blending systems, the heating rates were set to 5 K / min, 10 K / min, 15 K / min, and 20 K / min, and the curing curves of different resin blending systems were recorded to study the curing kinetics. The curing temperature curves are shown in Figure 2. Figure 2 , where part (a) is the curing temperature curve of Van-0, part (b) is the curing temperature curve of Van-0.25, part (c) is the curing temperature curve of Van-0.5, part (d) is the curing temperature curve of Van-0.75, and part (f) is the curing temperature curve of Van-1, Ti is the starting curing temperature, Tp is the peak curing temperature, and Te is the ending curing temperature.

[0064] Thermogravimetric analysis (TGA): A 2 mm diameter disc sample was placed in an aluminum crucible using TGA4000 and tested in a nitrogen atmosphere at a heating rate of 10 K / min. The test temperature range was 30-800 °C to determine the thermal stability of the sample. The results are shown in Figure 5 .

[0065] Dynamic mechanical analysis (DMA): A dynamic thermomechanical analyzer (TA Q800, USA) was used in single cantilever mode, with a heating rate of 5°C / min, a test temperature range of 30°C-250°C, and a frequency of 10 Hz. Figure 3 .

[0066] Mechanical performance test: A universal tensile testing machine was used to perform tensile bending tests at load rates of 5 mm / min and 2 mm / min. The results are shown in the table below. Figure 4

[0067] Electrical performance test: (1) Use power frequency test transformer to conduct power frequency breakdown voltage test, use spherical electrode to clamp the square sample with size of 15mm*15mm*1mm to conduct voltage boost test in dimethyl silicone oil, the voltage boost rate is constant at 2kV / s. Figure 6 .

[0068] (2) Leakage current test was conducted on MS2621VS tester. Five cylindrical specimens with a diameter of 50 mm and a height of 30 mm were prepared. Each surface was polished smooth and flat. The specimens were immersed in 0.1 wt% NaCl solution and boiled at 100°C for 100 h ± 0.5 h. The test voltage was 12 kV, the heating rate was 2 kV / s, and the withstand voltage time was 1 min. The results are shown in the figure. Figure 6 .

[0069] (3) The dielectric loss factor test was performed on the YG9100 fully automatic anti-interference precision dielectric loss tester. The test voltage was 1.5-3kV. The results are shown in Figure 6 .

[0070] Self-repair test: Scratch the sample lightly with a knife, the width of the scratch is about 30-40μm, put it in a drying oven at 180℃ / 3h, and observe the changes of the sample scratch with an optical microscope every 30min. Figure 10 , where (a) is the scratch photos of Van-0 at different times, (b) is the scratch photos of Van-0.25 at different times, (c) is the scratch photos of Van-0.5 at different times, (d) is the scratch photos of Van-0.75 at different times, and (e) is the scratch photos of Van-1 at different times.

[0071] Effect Example 2

[0072] The degradation properties of the epoxy resins prepared in Examples 2 to 5 and Comparative Example 1 were investigated as follows:

[0073] Take 2g of epoxy resin, add 40g of n-hexylamine, observe at the 25th hour after adding n-hexylamine, repeat 3 times, the results are shown in Figure 7 Part A is a photo of the epoxy resin just added to n-hexylamine, and part B is a photo of the epoxy resin after 25 hours of degradation.

[0074] The epoxy resin with n-hexylamine added was taken out every 0.5 h, the surface liquid was absorbed with filter paper and then weighed. The remaining mass percentage was calculated according to the formula: remaining mass percentage = mass of epoxy resin obtained / 2g × 100%. The remaining mass percentage was plotted against the time after the addition of n-hexylamine. The results are shown in the figure. Figure 8 .

[0075] Effect Example 3

[0076] The recycling performance of the epoxy resins prepared in Examples 2 to 5 was investigated as follows:

[0077] The recovery effect is expressed by electrical breakdown strength. First, the initial breakdown strength is measured. After physical / chemical recovery, the post-recovery breakdown strength is measured. The recovery rate is characterized by the ratio of the post-recovery breakdown strength to the initial breakdown strength. Figure 9 .

[0078] Result Analysis

[0079] Depend on Figure 2 It can be seen that the epoxy resins prepared in Examples 2 to 5 of the present invention all have curing onset temperatures below 100°C, and both peak and final curing temperatures are lower than those of the conventional epoxy resin (Comparative Example 1), demonstrating strong reactivity. Overall, Van-1 requires the lowest curing temperature, with a final curing temperature of only 115°C.

[0080] Depend on Figure 3 As can be seen, all epoxy resins in the examples of the present invention have glass transition temperatures above 110°C, demonstrating a certain degree of heat resistance at high temperatures, which demonstrates good tolerance for applications under high-temperature conditions. Specifically, the epoxy resins prepared in Examples 4 (Van-0.5) and 5 (Van-0.25) both have glass transition temperatures higher than that of the conventional bisphenol A epoxy resin (Comparative Example 1).

[0081] Depend on Figure 4 It can be seen that the mechanical properties of the epoxy resins prepared in Examples 2 to 5 of the present invention are comparable to those of the conventional bisphenol A epoxy resin (Comparative Example 1), indicating that the epoxy resins prepared in Examples 2 to 5 of the present invention have better mechanical properties. Among them, Van-0.25 has the best mechanical properties, while Van-0.75 and Van-1 have relatively poor mechanical properties.

[0082] Depend on Figure 5 It can be seen that the heat resistance of the epoxy resins prepared in Examples 2 to 5 of the present invention is comparable to that of traditional bisphenol A epoxy resins, and all have good heat resistance and a certain degree of high temperature resistance. Van-0.25 exhibits the highest heat resistance, while Van-1 has the worst heat resistance and begins thermal degradation first. The residual carbon content of the epoxy resins prepared in Examples 2 to 5 of the present invention is all higher than that of traditional bisphenol A epoxy resins, indicating that the epoxy resins prepared in Examples 2 to 5 of the present invention have a certain flame retardant effect.

[0083] Depend on Figure 6It can be seen that the breakdown strength of the epoxy resins produced in Examples of the present invention increases with decreasing vanillin bio-based content. Van-0.25 exhibits the highest breakdown strength, approaching that of conventional bisphenol A epoxy resins. The dielectric loss factors of Van-0.25 and Van-0.5 are superior to those of conventional bisphenol A epoxy resins, while Van-0.75 and Van-1 are inferior. Leakage current is comparable to that of conventional bisphenol A epoxy resins, with only minor differences, demonstrating excellent electrical performance.

[0084] Depend on Figure 7 and Figure 8 It can be seen that the epoxy resins prepared in Examples 2 to 4 of the present invention can be completely degraded after 25 hours, among which Van-0.75 degrades the fastest, degrading in 10 hours, and Van-0.25 degrades the slowest, degrading completely in 25 hours. Although Example 5 and the traditional bisphenol A epoxy resin are partially degraded, they cannot be completely degraded.

[0085] Depend on Figure 9 The recovery performance curves of the epoxy resin prepared by the present invention and the traditional bisphenol A epoxy resin show that the chemical recovery effect of the epoxy resin prepared by the present invention is generally better than the physical recovery effect. Van-1 has the best recovery effect, showing a recovery efficiency of 98%. Van-0.25 has the worst physical recovery effect.

[0086] Depend on Figure 10 It can be seen that the epoxy resins prepared in Examples 2 to 5 of the present invention all completed self-repairing under the conditions of 180°C / 3h. Among them, Van-1 had the best self-repairing performance, completing the repair in 60 minutes, followed by Van-0.75, which completed the repair in 120 minutes. The traditional bisphenol A epoxy resin still showed no self-repairing phenomenon at 180 minutes.

[0087] In summary, Van-0.25 has the best thermoelectrical properties, heat resistance, mechanical properties, and the highest glass transition temperature; Van-1 has the best recycling and self-healing properties, and Van-0.5 has the best comprehensive performance.

[0088] Therefore, the high-performance, biodegradable and recyclable vanillin-based epoxy resin provided by the present invention has strong reaction activity, low curing temperature, and an initial curing temperature below 100°C; good heat resistance, and a glass transition temperature of up to 159°C; excellent electrical insulation and mechanical properties, a dielectric loss factor of only 0.34, and a maximum tensile strength of up to 76 MPa; degradation can be achieved at 100°C within 25 hours; the degraded solution and crushed epoxy resin can be hot-pressed and recycled, and the electrical breakdown strength recovery rate can reach up to 98%; it has surface self-repairing ability, and scratches disappear when kept at 180°C for 3 hours, and the best scratches can disappear within 60 minutes.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-performance biodegradable and recyclable epoxy resin, characterized in that: Prepared from the following raw materials: p-Aminophenol, vanillin, epichlorohydrin, bisphenol A epoxy resin, curing agent, catalyst, tetrabutylammonium bromide, sodium hydroxide solution; The preparation method comprises the following steps: S1. Vanillin and p-aminophenol were dissolved in deionized water and anhydrous ethanol, respectively, and then poured into a round-bottom flask equipped with a condenser. The mixture was reacted under certain conditions, and then vacuum filtered. After completion, the mixture was washed three times with anhydrous ethanol and dried to obtain a purified yellow powder, which is a vanillin-based diphenol monomer. The reaction formula is: ; S2. Place a round-bottom flask equipped with a condenser reflux and magnetic stirring device in an oil bath, then add the vanillin-based diphenol monomer and epichlorohydrin obtained in step S1 to the round-bottom flask, start stirring, and add tetrabutylammonium bromide after all components are dissolved. Then, raise the system to a certain temperature and maintain it for a certain period of time. S3. Slowly dropwise add 20% by mass of sodium hydroxide to the reaction system, cool the reaction system to the desired temperature, and react for a certain period of time. Then, vacuum filter the resulting product, dilute it with petroleum ether, wash it with distilled water, and extract it three times. After removing excess epichlorohydrin and petroleum ether using a rotary evaporator, vacuum dry it overnight. The resulting white solid is a vanillin-based epoxy monomer, and the reaction formula is: ; S4. At 110° C., uniformly mix E-51 bisphenol A epoxy resin and the vanillin-based epoxy monomer obtained in step S3, then add a curing agent. After melt-mixing the components, add a catalyst, mix again, and then degas in a vacuum oven. Curing is performed in a stepwise curing process of 100° C. / 2 h + 130° C. / 5 h. In step S1, 1 mol of vanillin is dissolved in 4 L of deionized water, and 1 mol of p-aminophenol is dissolved in 2 L of anhydrous ethanol; the certain conditions refer to stirring under reflux at 50°C-60°C for 2-3 hours; and drying in a vacuum drying oven at 50°C-65°C overnight; In step S2, the amount of tetrabutylammonium bromide added is 10% of the mass of the vanillin diphenol monomer; the system is raised to a certain temperature and maintained for a certain time, which means raising the system to 80°C-90°C and reacting for 1.5-3 hours; in step S4, the content of the prepared vanillin epoxy resin is 25% of the mixture; The degradation method of the high-performance degradable and recyclable epoxy resin is achieved by placing the epoxy resin in a degradation solution, wherein the mass ratio of the epoxy resin to the degradation solution is 1:20, and the degradation solution is n-hexylamine; The recycling method of the high-performance biodegradable epoxy resin is carried out by a chemical recycling method or a physical recycling method. The steps of the chemical recycling method are as follows: The prepared vanillin-based epoxy resin was dissolved in the degradation solution, and the system was placed in a rotary evaporator. After the solution became viscous, the system was transferred to a mold, vacuum-heated, and continuously hot-pressed at 180°C and 10 MPa for 6 hours. The system was then cooled naturally and demolded when it cooled to room temperature to obtain the recovered vanillin-based epoxy resin. The physical recovery method is as follows: the vanillin-based epoxy resin is crushed into particles with a diameter of 1-5 mm using a grinder, placed in two steel plate molds coated with release oil, hot pressed on a flat plate vulcanizer at 200°C and 20 MPa for 4 hours, and formed after cooling to room temperature, and demolded to obtain a recycled sample.

2. The high-performance biodegradable and recyclable epoxy resin according to claim 1, characterized in that: The catalyst is 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole, the curing agent is 2-methylhexahydrophthalic anhydride, the bisphenol A epoxy resin is E-51 bisphenol A epoxy resin, and the mass fraction of the sodium hydroxide solution is 20%.

3. The high-performance biodegradable and recyclable epoxy resin according to claim 1, characterized in that: The molar ratio of p-aminophenol:vanillin:epichlorohydrin is 1:1:

10.

4. The high-performance biodegradable and recyclable epoxy resin according to claim 1, characterized in that: In step S3, slowly adding 20% by mass of sodium hydroxide means that the addition is completed within 0.5 hours, and the amount of 20% sodium hydroxide is twice the mass of the vanillin diphenol monomer; reducing the temperature to the required temperature and reacting for a certain time means reducing the temperature to room temperature and reacting for 3-5 hours; the amount of petroleum ether added is 20 times the mass of the vanillin diphenol monomer; and vacuum drying is drying in a vacuum drying oven at 50°C-70°C overnight.

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