A recyclable epoxy resin monomer and a preparation method and application thereof

Abstract

The application provides an epoxy resin monomer capable of closed-loop recycling, and a preparation method and application thereof. The epoxy resin monomer provided by the application has an acetal structure, the acetal structure is formed by reaction of a dialdehyde compound and a dihydroxy compound or a trihydroxy compound, an epoxy group is connected to the acetal structure through an ether bond, and the epoxy resin monomer contains a difunctional or tetrafunctional epoxy group. The cured product of the epoxy resin monomer provided by the application can break the acetal structure in the network under acidic degradation conditions, and the degradation product is a dialdehyde compound or a diketone compound and a well-defined polyhydric alcohol, so that controllable degradation and closed-loop recycling of the material are realized.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a closed-loop recyclable epoxy resin monomer, its preparation method, and its application. Background Technology

[0002] Epoxy resin, as an important thermosetting polymer material, is widely used in composite materials, electronic packaging, coatings, adhesives, and other fields due to its excellent mechanical properties, adhesive properties, electrical insulation properties, chemical corrosion resistance, and good processability. However, traditional epoxy resins form a highly cross-linked three-dimensional network structure after curing, resulting in insoluble and infusible properties. While this characteristic endows the material with excellent performance, it also creates a fundamental problem that makes it difficult to recycle and reuse after its service life. Currently, the vast majority of waste epoxy resin materials are disposed of through landfill or incineration, which not only wastes raw materials derived from petroleum resources but also brings severe environmental pressure.

[0003] To address this challenge, researchers are dedicated to developing recyclable epoxy resin systems. Existing technological approaches primarily include physical recycling, energy recovery, and chemical recycling. Physical recycling, such as mechanical crushing for use as filler, typically leads to a significant decline in material properties, making high-value reuse difficult. Energy recovery methods, such as incineration, do not achieve material cycling. Chemical recycling, particularly based on dynamic covalent chemistry, is considered a promising direction for the recycling of thermosetting resins. The core of chemical recycling is the introduction of dynamic covalent bonds into the resin network that can undergo reversible breakage / recombination reactions under specific external stimuli (such as heat, light, acid, and alkali), thereby degrading the originally permanent cross-linked network under specific conditions.

[0004] Currently, there are numerous research reports on recyclable epoxy resins based on dynamic covalent bonds, such as introducing hydrolyzable ester bonds, exchangeable carboxylic acid ester bonds, disulfide bonds, and imine bonds into the resin network. However, many existing designs produce degradation products that are oligomers or mixtures with broad molecular weight distributions, rather than well-defined, pure monomers or raw materials. These complex degradation products are difficult to directly separate and purify, and cannot be directly used to resynthesize equivalent original resins without complex conversion processes. Essentially, this is a form of "downgraded recycling," rather than true monomer-level "closed-loop recycling." Summary of the Invention

[0005] To solve all or part of the above-mentioned technical problems, the present invention provides the following technical solutions: A first aspect of the present invention provides a closed-loop recyclable epoxy resin monomer, the structure of which is shown in formulas I-a, I-b, I-c, I-d, II-a, II-b, II-c, or II-d: R1 and R3 are independently selected from any one of H, CH3, and CH2CH3, and R2 is selected from... Any one of them; R4 is selected from Any one of them, R 5a R 5b R 5c R 5d Independent selection Any one of them.

[0006] In some embodiments, the recyclable epoxy resin monomer is any one of the following structural compounds: .

[0007] The epoxy resin monomers with difunctional and tetrafunctional epoxy groups provided by this invention both possess two acetal structures. These acetal structures are formed by the reaction of aldehyde compounds with dihydroxy or trihydroxy compounds, with the epoxy groups bonded to the acetal structures via ether bonds. After curing, these epoxy resin monomers exhibit the excellent comprehensive properties of epoxy resins, demonstrating good thermal stability and mechanical properties, fully meeting the processing and usage requirements of thermosetting resins. Furthermore, they can undergo selective and complete degradation under relatively mild acidic conditions, with the degradation products being dialdehyde compounds or diketone compounds and polyols, which can be precisely separated. The dialdehyde compounds obtained from the degradation are the same as those required in the epoxy monomer preparation method and can be directly used to resynthesize the same resin. Moreover, the polyols obtained from the degradation have well-defined structures, achieving controllable degradation and "closed-loop recovery."

[0008] A second aspect of the present invention provides a method for preparing a closed-loop recyclable epoxy resin monomer, comprising: A first reaction is carried out on a first mixed reaction system containing a dialdehyde compound, a dihydroxy compound, or a trihydroxy compound to obtain an acetal polyol intermediate. A second reaction is carried out on a second mixed reaction system containing the acetal polyol intermediate, epichlorohydrin, and hydroxide to obtain a ring-closed recyclable epoxy resin monomer.

[0009] In some embodiments, the dialdehyde compound includes one or more combinations of terephthalaldehyde, isophthalaldehyde, o-phthalaldehyde, 2,5-furandialdehyde, ethylene glycol, and glutaraldehyde.

[0010] In some embodiments, the dihydroxy compound includes 1,4-cyclohexanediol and / or 1,6-hexanediol.

[0011] In some embodiments, the trihydroxy compound includes one or more combinations of 2-hydroxymethyl-1,3-propanediol, 1,1,1-tris(hydroxymethyl)ethane, and 1,1,1-tris(hydroxymethyl)propane.

[0012] In some embodiments, the hydroxide includes sodium hydroxide and / or potassium hydroxide. The hydroxide can be prepared as a 5%–50% (w / w) hydroxide solution before being added to the reaction system.

[0013] In some embodiments, the mass ratio of the dialdehyde compound to the dihydroxy compound or trihydroxy compound is 1:2~4.

[0014] In some embodiments, the mass ratio of epichlorohydrin to acetal polyol intermediate is 1 to 30:1.

[0015] In some embodiments, the mass ratio of sodium hydroxide to acetal polyol intermediate is 1:1 to 20.

[0016] In some embodiments, the temperature of the first reaction is 60~140°C.

[0017] In some embodiments, the reaction time for the first reaction is 0.5 h to 72 h.

[0018] In some embodiments, the temperature of the second reaction is 10~100°C.

[0019] In some embodiments, the second reaction takes 0.5 h to 72 h.

[0020] In some embodiments, the first mixed reaction system further includes a first catalyst, which comprises one or more of the following: p-toluenesulfonic acid, citric acid, oxalic acid, methanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, hydrogen-form Y zeolite, hydrogen-form Beta zeolite, H-mordenite, phosphotungstic acid, silyloidal molybdenum acid, cesium phosphotungstate, ammonium phosphotungstate, alumina, titanium dioxide, zirconium oxide, tungsten oxide, sulfonic acid-type polystyrene resin, perfluorosulfonic acid resin, acidified montmorillonite, acidified kaolin, acidified bentonite, aluminum phosphate, boron phosphate, sulfonated activated carbon, sulfonated graphene, titanium sulfate, tin sulfate, ferric sulfate, zirconium nitrate, aluminum chloride, ferric chloride, titanium tetrachloride, zinc chloride, trimethylaluminum, scandium trifluoromethanesulfonate, tin tetrachloride, iodine, and boron tribromide.

[0021] In some embodiments, the second mixed reaction system further includes a second catalyst, which includes one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, hexadecyltrimethylammonium bromide, or tetraethylammonium bromide.

[0022] In some embodiments, the first mixed reaction system further includes a first organic solvent, which includes one or more combinations of toluene, benzene, petroleum ether, ethyl acetate, n-hexane, cyclohexane, acetone, butanone, ethanol, and methanol. The first organic solvent can dissolve the reactants and carry away the water generated in the reaction via an azeotropic reaction.

[0023] In some embodiments, the second mixed reaction system further includes a second organic solvent, which includes one or more combinations of toluene, benzene, xylene, dichloromethane, chloroform, petroleum ether, n-hexane, cyclohexane, ethyl acetate, and nitrile. The second organic solvent is used to dilute the mixed system after the second reaction and is easily washed with water.

[0024] In some embodiments, the mass ratio of the first catalyst to the dialdehyde compound is 1:5 to 100.

[0025] In some embodiments, the mass ratio of the second catalyst to the acetal polyol intermediate is 1:5~100.

[0026] In some embodiments, the mass ratio of the first organic solvent to the dialdehyde compound is 1 to 20:1.

[0027] In some embodiments, the mass ratio of the second organic solvent to the dialdehyde compound is 1 to 20:1.

[0028] In some embodiments, the preparation method specifically includes: after the first reaction, directly adding the second catalyst, epichlorohydrin, and hydroxide to the reaction product containing the acetal polyol intermediate to carry out the second reaction. The epoxy resin monomer provided by this invention can be prepared by a one-pot, two-step method, meaning that no processing is required after the first reaction; the second reaction can be carried out directly by adding the second catalyst, epichlorohydrin, and sodium hydroxide, thereby simplifying the synthesis steps. This is because the acetalization conversion rate of the first reaction is high, and the reactants can react completely under strict stoichiometry. The dehydrating agent added during acetalization can act as a solvent during the epoxidation in the second reaction, and the first catalyst added during acetalization can be completely neutralized by the second catalyst added during epoxidation.

[0029] A second aspect of the present invention provides a closed-loop recyclable epoxy resin monomer, which is prepared by the method for preparing a closed-loop recyclable epoxy resin monomer as described in any of the technical solutions.

[0030] The present invention provides a simple preparation process that is easy to operate, has good controllability, is easy to implement, and is suitable for large-scale industrial production. The epoxy resin monomers obtained can be applied to biodegradable plastics, coatings, adhesives, aerospace and other fields.

[0031] A third aspect of the present invention provides an epoxy resin cured product obtained by curing and crosslinking a closed-loop recyclable epoxy resin monomer as described in any of the technical solutions.

[0032] In some embodiments, the epoxy resin monomer is mixed with a curing agent and then cured and crosslinked to obtain the cured epoxy resin. The epoxy resin monomer is compatible with a variety of curing agents, such as dicyandiamide, tetrahydrophthalic anhydride, 405 mercaptan, isophorone diamine, ethylenediamine, diethylenetriamine, diaminodiphenylmethane, isophthalamide, polyamide 650, polyamide 651, phenolic amine, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, 2-ethyl-4-methylimidazole, tetraethylenepentamine, triethylenetetraamine, pentanediamine, etc., but is not limited to these.

[0033] A fourth aspect of the present invention provides a closed-loop recycling method for epoxy resin cured products, comprising: An epoxy resin cured product is obtained by curing and crosslinking epoxy resin monomers, wherein the epoxy resin monomers include the closed-loop recyclable epoxy resin monomers described in any of the technical solutions. The epoxy resin cured product is degraded using an acidic degradation solution and then post-treated to obtain a dialdehyde compound or a diketone compound and a polyol.

[0034] In some embodiments, the degradation temperature is above 25°C, preferably 60~120°C.

[0035] In some embodiments, the degradation time is 0.5h to 72h, preferably 4h to 24h.

[0036] In some embodiments, the method specifically includes: immersing the epoxy resin cured product in an acidic degradation solution and soaking it at a preset temperature for a preset time to completely degrade and dissolve the resin matrix in the degradation solution; concentrating the obtained degradation solution and extracting it multiple times with an extractant under heating and stirring conditions; concentrating and purifying the extracted organic phase to recover dialdehyde compounds or diketone compounds; adding excess sodium bicarbonate to the extracted aqueous phase to neutralize it, precipitating the polyol, then removing the aqueous phase, dissolving the organic matter with a solvent, filtering to remove inorganic salts, and finally removing the solvent to recover the polyol.

[0037] For example, a typical degradation product of an epoxy resin cured product is as follows: Figure 1 As shown.

[0038] The dialdehyde compounds obtained from degradation can be recycled for the preparation of the epoxy resin monomers described in this invention. The polyols obtained from degradation have well-defined structures and can be used to prepare polyurethane, epoxy resin toughening accelerators, photocurable monomers, etc., thus realizing the effective utilization of degradation products.

[0039] In some embodiments, the acidic degradation solution includes an organic solvent, water, and an acidic catalyst.

[0040] In some embodiments, the organic solvent in the acidic degradation solution includes one or more of acetone, DMF, DMSO, dioxane, tetrahydrofuran, and acetonitrile.

[0041] In some embodiments, the mass ratio of the organic solvent to water is 1:5 to 100.

[0042] In some embodiments, the acidic catalyst includes one or more of the following: p-toluenesulfonic acid, citric acid, oxalic acid, methanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, hydrogen-form Y zeolite, hydrogen-form Beta zeolite, H-mordenite, phosphotungstic acid, silylomiculitic acid, cesium phosphotungstate, ammonium phosphotungstate, alumina, titanium dioxide, zirconium oxide, tungsten oxide, sulfonated polystyrene resin, perfluorosulfonated resin, acidified montmorillonite, acidified kaolin, acidified bentonite, aluminum phosphate, boron phosphate, sulfonated activated carbon, sulfonated graphene, titanium sulfate, tin sulfate, ferric sulfate, zirconium nitrate, aluminum chloride, ferric chloride, titanium tetrachloride, zinc chloride, trimethylaluminum, scandium trifluoromethanesulfonate, tin tetrachloride, iodine, and boron tribromide.

[0043] In some embodiments, the mass ratio of the acidic catalyst to the total mass of the organic solvent and water is 1:5 to 100.

[0044] In some embodiments, the extractant includes one or more combinations of toluene, benzene, xylene, chloroform, carbon tetrachloride, petroleum ether, ethyl acetate, isopropyl acetate, n-butyl acetate, n-hexane, and cyclohexane.

[0045] In some embodiments, the amount of extractant used satisfies the following condition: the mass ratio of extractant to epoxy resin cured product is 1 to 20:1.

[0046] In some embodiments, the organic compound is dissolved using one or more of the following: acetone, DMF, DMSO, dioxane, tetrahydrofuran water, acetonitrile, methanol, and ethanol. The solvent is then removed by filtration, and the polyol is recovered.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects: (1) The epoxy resin monomers with difunctional or tetrafunctional epoxy groups provided by the present invention all have two acetal structures. The acetal structure is formed by the reaction of aldehyde compounds with dihydroxy or trihydroxy compounds, and the epoxy groups are attached to the acetal structure by ether bonds. The cured product formed by the epoxy resin monomer can break the acetal structure in the network under acidic conditions and degrade into dialdehyde compounds or diketone compounds and polyols. The degradation products are stable and have clear structures. The dialdehyde compounds or diketone compounds and polyols have large differences in properties and are easy to separate. The dialdehyde compounds can be recycled to synthesize the same resin monomers. The polyols with clear structures can be used to prepare polyurethane, epoxy resin toughening accelerators, photocurable monomers, etc., so as to realize the effective utilization of degradation products.

[0048] (2) The method for synthesizing epoxy resin monomers provided by the present invention is simple. It can be directly synthesized in a one-pot two-step method. That is, after the first reaction is completed, the second reaction can be carried out directly without any treatment. It is easy to operate, has good controllability, and is easy to implement. It is especially suitable for large-scale industrial production. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram of the degradation products of an example structure of an epoxy resin cured product. Figure 2 This is the 1H NMR spectrum of the epoxy resin monomer synthesized in Example 4; Figure 3 The non-isothermal DSC curve of epoxy resin cured product A-4 obtained in Example 41; Figure 4 This is the uniaxial tensile stress-strain curve of epoxy resin cured product A-4 obtained in Example 41; Figure 5 This is a graph showing the impact strength data of the unnotched simply supported beam of epoxy resin cured product A-4 obtained in Example 41. Detailed Implementation

[0051] The invention will be more fully understood through the following detailed description, which should be read in conjunction with the accompanying drawings. Detailed embodiments of the invention are disclosed herein; however, it should be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as intended to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0052] In addition, unless otherwise specified, all raw materials used in the following embodiments can be purchased from the market or other sources, and all production and testing equipment used are known in the art, as are the testing methods used.

[0053] In the following examples, the proton nuclear magnetic resonance spectrum... 1 ¹H-NMR was measured using a Bruker 400AVANCE III spectrometer at 400 MHz, using deuterated dimethyl sulfoxide (DMSO).

[0054] In the following examples, non-isothermal scanning calorimetry (DSC) was performed using a Mettler Star 3 DSC system under a nitrogen atmosphere at a flow rate of 10 mL / min. - The heating rate is ¹.

[0055] In the following examples, uniaxial tensile testing was performed on the cured epoxy resin using a universal testing machine (UTM4000, Sunstest), at a range of 10 mm min. - ¹ The stretching rate is carried out.

[0056] In the following embodiments, the impact fracture test was performed on the cured epoxy resin using a digital pendulum impact testing machine (AISRY, Guangdong, China), with a support span of 60 mm and an impact velocity of 2.9 m / s.

[0057] Example 1 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of terephthalaldehyde, 134 g of trimethylolpropane, 1 g of p-toluenesulfonic acid, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120°C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0058] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 6 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes; then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then wait for the reaction solution to cool.

[0059] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0060] The epoxy resin monomer obtained in this embodiment has the following structural formula I-1, with a yield of 92%.

[0061] Formula (I-1) Example 2 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of terephthalaldehyde, 60 g of trimethylolethane, 67 g of trimethylolpropane, 0.5 g of citric acid, and 220 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0062] (2) Add 450 g of 45 wt.% NaOH aqueous solution and 8 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes; then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then wait for the reaction solution to cool.

[0063] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0064] The epoxy resin monomer obtained in this embodiment has the following structural formula I-2, with a yield of 94%.

[0065] Formula (I-2) Example 3 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of terephthalaldehyde, 120 g of trimethylolethane, 0.8 g of oxalic acid and 200 g of xylene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 140 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0066] (2) Add 500 g of 30 wt.% NaOH aqueous solution and 8 g of benzyltriethylammonium chloride to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then allow the reaction solution to cool.

[0067] (3) After the reaction solution is cooled, 200 g of xylene is added for dilution, and the solution is washed five times with deionized water. Finally, xylene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0068] The epoxy resin monomer obtained in this embodiment has the following structural formula I-3, with a yield of 94%. Formula (I-3) Example 4 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of isophthalaldehyde, 134 g of trimethylolpropane, 1.2 g of methanesulfonic acid and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 7 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0069] (2) Add 300 g of 50 wt.% NaOH aqueous solution and 10 g of hexadecyltrimethylammonium bromide to the reaction product of step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 300 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 35 °C for 7 hours.

[0070] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0071] The epoxy resin monomer obtained in this embodiment has the following structural formula I-4, with a yield of 93%.

[0072] Formula (I-4) Figure 2This is the 1H NMR spectrum of the epoxy resin monomer synthesized in Example 4. Figure 3 This is the carbon NMR spectrum of the epoxy resin monomer synthesized in Example 4. Figure 4 This is the time-of-flight mass spectrum of the epoxy resin monomer synthesized in Example 4.

[0073] Example 5 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of isophthalaldehyde, 60 g of trimethylolethane, 67 g of trimethylolpropane, 2 g of sulfuric acid, and 200 g of ethyl acetate to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0074] (2) Add 450 g of 40 wt.% NaOH aqueous solution and 10 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 25 °C for 24 hours, and then allow the reaction solution to cool.

[0075] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0076] The epoxy resin monomer obtained in this embodiment has the following structural formula I-5, with a yield of 94%. Formula (I-5) Example 6 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of isophthalaldehyde, 120 g of trimethylolethane, 3 g of hydrochloric acid and 250 g of petroleum ether to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0077] (2) Add 800 g of 20 wt.% NaOH aqueous solution and 8 g of tetraethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 45 °C for 6 hours, and then allow the reaction solution to cool.

[0078] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, petroleum ether and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0079] The epoxy resin monomer obtained in this embodiment has the following structural formula I-6, with a yield of 94%. Formula (I-6) Example 7 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,4-cyclohexanedione, 134 g of trimethylolpropane, 1.2 g of phosphoric acid, and 180 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0080] (2) Add 250 g of 40 wt.% NaOH aqueous solution and 20 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 35 °C for 10 hours, and then allow the reaction solution to cool.

[0081] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain the target product, acetal epoxy resin.

[0082] The epoxy resin monomer obtained in this embodiment has the following structural formula I-7, with a yield of 90%.

[0083] Formula (I-7) Example 8 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,4-cyclohexanedione, 60 g of trimethylolethane, 67 g of trimethylolpropane, 4 g of hydrogen-form Y zeolite, and 200 g of cyclohexane to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 80 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0084] (2) Add 350 g of 40 wt.% NaOH aqueous solution and 30 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 450 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 25 °C for 24 hours, and then allow the reaction solution to cool.

[0085] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, cyclohexane, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0086] The epoxy resin monomer obtained in this embodiment has the following structural formula I-8, with a yield of 91%.

[0087] Formula (I-8) Example 9 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,4-cyclohexanedione, 120 g of tris(hydroxymethyl)ethane, 5 g of hydrogen-form Beta zeolite, and 250 g of n-hexane to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 70 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0088] (2) Add 300 g of 50 wt.% NaOH aqueous solution and 9 g of tetraethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 300 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0089] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene, n-hexane and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0090] The epoxy resin monomer obtained in this embodiment has the following structural formula I-6, with a yield of 94%.

[0091] Formula (I-9) Example 10 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of o-phthalaldehyde, 134 g of trimethylolpropane, 1 g of H-mordenite, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0092] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 6 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0093] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0094] The epoxy resin monomer obtained in this embodiment has the following structural formula I-1, with a yield of 92%.

[0095] Formula (I-10) Example 11 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of o-phthalaldehyde, 60 g of trimethylolethane, 67 g of trimethylolpropane, 0.5 g of phosphotungstic acid, and 220 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0096] (2) Add 450 g of 45 wt.% NaOH aqueous solution and 8 g of tetrabutylammonium bromide to the mixture, heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then wait for the reaction solution to cool down.

[0097] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0098] The epoxy resin monomer obtained in this embodiment has the following structural formula I-11, with a yield of 94%.

[0099] Formula (I-11) Example 12 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of o-phthalaldehyde, 120 g of trimethylolethane, 0.8 g of silicomolybdic acid and 200 g of xylene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 140 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0100] (2) Add 500 g of 30 wt.% NaOH aqueous solution and 8 g of benzyltriethylammonium chloride to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then allow the reaction solution to cool.

[0101] (3) After the reaction solution is cooled, 200 g of xylene is added for dilution, and the solution is washed five times with deionized water. Finally, xylene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0102] The epoxy resin monomer obtained in this embodiment has the following structural formula I-12, with a yield of 94%.

[0103] Formula (I-12) Example 13 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,3-cyclohexanedione, 134 g of trimethylolpropane, 1.2 g of cesium phosphotungstate, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 7 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0104] (2) Add 300 g of 50 wt.% NaOH aqueous solution and 10 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 300 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 35 °C for 7 hours, and then allow the reaction solution to cool.

[0105] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0106] The epoxy resin monomer obtained in this embodiment has the following structural formula I-13, with a yield of 93%.

[0107] Formula (I-13) Example 14 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,3-cyclohexanedione, 60 g of trimethylolethane, 67 g of trimethylolpropane, 2 g of ammonium phosphotungstate, and 200 g of ethyl acetate to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0108] (2) Add 450 g of 40 wt.% NaOH aqueous solution and 10 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 25 °C for 24 hours, and then allow the reaction solution to cool.

[0109] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain the epoxy resin monomer.

[0110] The epoxy resin monomer obtained in this embodiment has the following structural formula I-14, with a yield of 94%.

[0111] Formula (I-14) Example 15 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,3-cyclohexanedione, 120 g of trimethylolethane, 3 g of alumina, and 250 g of petroleum ether to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0112] (2) Add 800 g of 20 wt.% NaOH aqueous solution and 8 g of tetraethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 45 °C for 6 hours, and then allow the reaction solution to cool.

[0113] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, petroleum ether and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0114] The epoxy resin monomer obtained in this embodiment has the following structural formula I-15, with a yield of 94%.

[0115] Formula (I-15) Example 16 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,2-cyclohexanedione, 134 g of trimethylolpropane, 1.2 g of titanium dioxide, and 180 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0116] (2) Add 250 g of 40 wt.% NaOH aqueous solution and 20 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 35 °C for 10 hours, and then allow the reaction solution to cool.

[0117] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0118] The epoxy resin monomer obtained in this embodiment has the following structural formula I-16, with a yield of 90%.

[0119] Formula (I-16) Example 17 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,2-cyclohexanedione, 60 g of trimethylolethane, 67 g of trimethylolpropane, 4 g of zirconium oxide, and 200 g of cyclohexane to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 80 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0120] (2) Add 350 g of 40 wt.% NaOH aqueous solution and 30 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 450 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 25 °C for 24 hours, and then allow the reaction solution to cool.

[0121] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, cyclohexane, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0122] The epoxy resin monomer obtained in this embodiment has the following structural formula I-17, with a yield of 91%.

[0123] Formula (I-17) Example 18 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,2-cyclohexanedione, 120 g of trimethylolethane, 5 g of tungsten oxide, and 250 g of n-hexane to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 70 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0124] (2) Add 300 g of 50 wt.% NaOH aqueous solution and 9 g of tetraethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 300 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0125] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene, n-hexane and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0126] The epoxy resin monomer obtained in this embodiment has the following structural formula I-18, with a yield of 94%.

[0127] Formula (I-18) Example 19 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 62 g of 2,5-dicarboxyfuran, 134 g of trimethylolpropane, 1 g of sulfonic acid polystyrene resin and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0128] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 6 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0129] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0130] The epoxy resin monomer obtained in this embodiment has the following structural formula I-19, with a yield of 92%.

[0131] Formula (I-19) Example 20 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 62 g of 2,5-dicarboxyfuran, 60 g of trimethylolethane, 67 g of trimethylolpropane, 0.5 g of perfluorosulfonic acid resin, and 220 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0132] (2) Add 450 g of 45 wt.% NaOH aqueous solution and 8 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then allow the reaction solution to cool.

[0133] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0134] The epoxy resin monomer obtained in this embodiment has the following structural formula I-20, with a yield of 94%.

[0135] Formula (I-20) Example 21 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 62 g of 2,5-dicarboxyfuran, 120 g of trimethylolethane, 0.8 g of acidified montmorillonite, and 200 g of xylene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 140 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0136] (2) Add 500 g of 30 wt.% NaOH aqueous solution and 8 g of benzyltriethylammonium chloride to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 40 °C for 10 hours, and then allow the reaction solution to cool.

[0137] (3) After the reaction solution is cooled, 200 g of xylene is added for dilution, and the solution is washed five times with deionized water. Finally, xylene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0138] The epoxy resin monomer obtained in this embodiment has the following structural formula I-21, with a yield of 94%.

[0139] Formula (I-21) Example 22 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 29 g of glyoxal, 134 g of trimethylolpropane, 1.2 g of acidified kaolin, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 50 °C for 7 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0140] (2) Add 300 g of 50 wt.% NaOH aqueous solution and 10 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 300 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 35 °C for 7 hours, and then allow the reaction solution to cool.

[0141] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0142] The epoxy resin monomer obtained in this embodiment has the following structural formula I-22, with a yield of 93%.

[0143] Formula (I-22) Example 23 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 29 g of glyoxal, 60 g of trimethylolethane, 67 g of trimethylolpropane, 2 g of acidified bentonite, and 200 g of ethyl acetate to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 50 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0144] (2) Add 450 g of 40 wt.% NaOH aqueous solution and 10 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 25 °C for 24 hours, and then allow the reaction solution to cool.

[0145] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0146] The epoxy resin monomer obtained in this embodiment has the following structural formula I-23, with a yield of 94%.

[0147] Formula (I-23) Example 24 This embodiment provides a difunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 29 g of glyoxal, 120 g of trimethylolethane, 3 g of aluminum phosphate, and 250 g of petroleum ether to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 50 °C for 6 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0148] (2) Add 800 g of 20 wt.% NaOH aqueous solution and 8 g of tetraethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 400 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 45 °C for 6 hours, and then allow the reaction solution to cool.

[0149] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, petroleum ether and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0150] The epoxy resin monomer obtained in this embodiment has the following structural formula I-24, with a yield of 94%.

[0151] Formula (I-24) Example 25 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of terephthalaldehyde, 288 g of 1,4-cyclohexanediethanol, 1 g of boron phosphate, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0152] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 6 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0153] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0154] The epoxy resin monomer obtained in this embodiment has the following structural formula II-1, with a yield of 92%.

[0155] Equation (II-1) Example 26 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of isophthalaldehyde, 288 g of 1,4-cyclohexanediethanol, 5 g of sulfonated activated carbon and 300 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0156] (2) Add 800 g of 30 wt.% NaOH aqueous solution and 5 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 350 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 30 °C for 18 hours, and then allow the reaction solution to cool.

[0157] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0158] The epoxy resin monomer obtained in this embodiment has the following structural formula II-2, with a yield of 89%.

[0159] (II-2) Example 27 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of o-phthalaldehyde, 288 g of 1,4-cyclohexanediethanol, 10 g of sulfonated graphene, and 200 g of petroleum ether to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0160] (2) Add 800 g of 20 wt.% NaOH aqueous solution and 10 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 450 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 20 °C for 24 hours, and then allow the reaction solution to cool.

[0161] (3) After the reaction solution is cooled, 200 g of petroleum ether is added for dilution, and the solution is washed five times with deionized water. Finally, the petroleum ether and excess epichlorohydrin are removed by vacuum distillation to obtain the epoxy resin monomer.

[0162] The epoxy resin monomer obtained in this embodiment has the following structural formula II-3, with a yield of 89%.

[0163] (II-3) Example 28 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,4-cyclohexanedione, 288 g of 1,4-cyclohexanediethanol, 10 g of titanium sulfate, and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0164] (2) Add 1000 g of 10 wt.% NaOH aqueous solution and 40 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0165] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0166] The epoxy resin monomer obtained in this embodiment has the following structural formula II-4, with a yield of 89%.

[0167] (II-4) Example 29 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,3-cyclohexanedione, 288 g of 1,4-cyclohexanediethanol, 20 g of tin sulfate, and 200 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0168] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 25 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0169] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0170] The epoxy resin monomer obtained in this embodiment has the following structural formula II-5, with a yield of 89%.

[0171] (II-5) Example 30 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,2-cyclohexanedione, 288 g of 1,4-cyclohexanediethanol, 20 g of ferric sulfate and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0172] (2) Add 400 g of 30 wt.% NaOH aqueous solution and 25 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 250 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0173] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0174] The epoxy resin monomer obtained in this embodiment has the following structural formula II-6, with a yield of 89%.

[0175] (II-6) Example 31 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (2) Add 62 g of 2,5-dicarboxyfuran, 288 g of 1,4-cyclohexanediethanol, 20 g of zirconium nitrate, and 200 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0176] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 25 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0177] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0178] The epoxy resin monomer obtained in this embodiment has the following structural formula II-7, with a yield of 89%.

[0179] (II-7) Example 32 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 29 g of glyoxal, 288 g of 1,4-cyclohexanediethanol, 5 g of aluminum chloride, and 300 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 50 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0180] (2) Add 800 g of 30 wt.% NaOH aqueous solution and 5 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 350 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 30 °C for 18 hours, and then allow the reaction solution to cool.

[0181] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0182] The epoxy resin monomer obtained in this embodiment has the following structural formula II-8, with a yield of 89%.

[0183] (II-8) Example 33 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of terephthalaldehyde, 236 g of 1,6-hexanediol, 1 g of ferric chloride and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0184] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 6 g of tetrabutylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 278 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 8 hours, and then allow the reaction solution to cool.

[0185] (3) After the reaction solution is cooled, 200 g of toluene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0186] The epoxy resin monomer obtained in this embodiment has the following structural formula II-9, with a yield of 92%.

[0187] Equation (II-9) Example 34 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of isophthalaldehyde, 236 g of 1,6-hexanediol, 5 g of titanium tetrachloride, and 300 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 120 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0188] (2) Add 800 g of 30 wt.% NaOH aqueous solution and 5 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 350 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 30 °C for 18 hours, and then allow the reaction solution to cool.

[0189] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0190] The epoxy resin monomer obtained in this embodiment has the following structural formula II-10, with a yield of 89%.

[0191] (II-10) Example 35 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 67 g of o-phthalaldehyde, 236 g of 1,6-hexanediol, 10 g of zinc chloride, and 200 g of petroleum ether to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0192] (2) Add 800 g of 20 wt.% NaOH aqueous solution and 10 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 450 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 20 °C for 24 hours, and then allow the reaction solution to cool.

[0193] (3) After the reaction solution is cooled, 200 g of petroleum ether is added for dilution, and the solution is washed five times with deionized water. Finally, the petroleum ether and excess epichlorohydrin are removed by vacuum distillation to obtain the epoxy resin monomer.

[0194] The epoxy resin monomer obtained in this embodiment has the following structural formula II-11, with a yield of 89%.

[0195] (II-11) Example 36 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,4-cyclohexanedione, 236 g of 1,6-hexanediol, 10 g of trimethylaluminum and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 90 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0196] (2) Add 1000 g of 10 wt.% NaOH aqueous solution and 40 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0197] (3) After the reaction solution is cooled, 200 g of ethyl acetate is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0198] The epoxy resin monomer obtained in this embodiment has the following structural formula II-12, with a yield of 89%.

[0199] (II-12) Example 37 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,3-cyclohexanedione, 236 g of 1,6-hexanediol, 20 g of scandium trifluoromethanesulfonate, and 200 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0200] (2) Add 400 g of 50 wt.% NaOH aqueous solution and 25 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0201] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0202] The epoxy resin monomer obtained in this embodiment has the following structural formula II-13, with a yield of 89%.

[0203] (II-13) Example 38 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 56 g of 1,2-cyclohexanedione, 236 g of 1,6-hexanediol, 20 g of tin tetrachloride and 200 g of toluene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0204] (2) Add 400 g of 30 wt.% NaOH aqueous solution and 25 g of tetrabutylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 250 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0205] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0206] The epoxy resin monomer obtained in this embodiment has the following structural formula II-14, with a yield of 89%.

[0207] (II-14) Example 39 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 62 g of 2,5-dicarboxyfuran, 236 g of 1,6-hexanediol, 20 g of iodine and 200 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 100 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0208] ( ) Add 400 g of 50 wt.% NaOH aqueous solution and 25 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1). Heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 550 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 50 °C for 24 hours, and then allow the reaction solution to cool.

[0209] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, toluene, ethyl acetate and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0210] The epoxy resin monomer obtained in this embodiment has the following structural formula II-15, with a yield of 89%.

[0211] (II-15) Example 40 This embodiment provides a tetrafunctional epoxy resin monomer and its preparation method, specifically including the following steps: (1) Add 29 g of glyoxal, 236 g of 1,6-hexanediol, 5 g of boron tribromide and 300 g of benzene to a 3-liter round-bottom flask equipped with a thermometer and a water separator. React at 50 °C for 10 hours. After the reaction is completed, cool to room temperature to obtain an acetal polyol intermediate.

[0212] (2) Add 800 g of 30 wt.% NaOH aqueous solution and 5 g of hexadecyltrimethylammonium bromide to the reaction product obtained in step (1), heat the mixture to 50 °C and stir vigorously for 30 minutes. Then, slowly add 350 g of epichlorohydrin dropwise over 30 minutes through a constant pressure dropping funnel. After the addition is complete, continue the reaction at 30 °C for 18 hours, and then allow the reaction solution to cool.

[0213] (3) After the reaction solution is cooled, 200 g of benzene is added for dilution, and the solution is washed five times with deionized water. Finally, benzene and excess epichlorohydrin are removed by vacuum distillation to obtain epoxy resin monomer.

[0214] The epoxy resin monomer obtained in this embodiment has the following structural formula II-16, with a yield of 89%.

[0215] (II-16) The present invention also uses the acetal epoxy resin obtained in the above embodiments to be cured with the currently mainstream curing agent. Its components and contents are shown in Table 1. The number of "parts" referred to in Table 1 refers to parts by mass.

[0216] Table 1. Components and content of acetal epoxy resin cured products The relevant properties of the obtained epoxy resin cured product were tested, and the test methods are as follows: Differential scanning calorimetry (DSC): A Mettler-Toledo Star3 DSC (Mettler-Toledo, USA) was used in a nitrogen atmosphere at a rate of 50 mL / min. -1 The flow rate was [value], and the heating rate was 10 °C / min from 25 to 200 °C. -1 Record the DSC curve to measure the glass transition temperature.

[0217] Uniaxial tensile test: A general-purpose testing machine UTM4000 (Shenzhen Sansi Zongheng Technology Co., Ltd., China) was used. The gauge length of the specimen was 40 mm, and the specimen dimensions were 80 mm (length) × 7 mm (width) × 0.2 mm (thickness). The test was conducted at 10 mm min. -1 Tests were conducted at various speeds.

[0218] Unnotched simply supported beam impact test: Unnotched simply supported beam impact fracture tests were conducted on cured epoxy resin specimens using a 5J digital display pendulum impact testing machine (AISRY, Guangdong, China). The test used a support span of 60 mm, an impact velocity of 2.9 m / s, and each sample was repeated 5 times.

[0219] The test results are shown in Table 2: Table 2. Relevant properties of cured products based on epoxy resin monomers from Examples 1-40 Example 41 Example 41 provides an epoxy resin cured product based on the epoxy resin monomer of Example 4, specifically comprising the following steps: Weighing 20 grams of the epoxy resin prepared in Example 4 (epoxy value 0.413) and 3.5157 grams of IPDA (isophorone diamine), controlling the molar ratio of epoxy groups to amino groups to be 2:1. After preliminary mixing of the two components, the mixture is placed in a vacuum degassing machine for high-vacuum centrifugation degassing. After degassing, the mixture is poured into a stainless steel mold, or compressed and molded using a flat vulcanizing machine under a pressure of 10 MPa. Subsequently, the molded mixture is cured at 140 °C for 6 hours. Finally, the sample is slowly cooled to ambient temperature to obtain the epoxy resin cured product.

[0220] Figure 3 The image shows the DSC non-isothermal curve of epoxy resin cured product A-4 obtained in Example 41, which has a glass transition temperature of 118°C. Figure 4 The figure shows the uniaxial tensile stress-strain curve of epoxy resin cured product A-4 obtained in Example 41, with a tensile strength of 72 MPa and an elongation at break of 17%. Figure 5 This is a graph showing the impact strength data of the unnotched simply supported beam of epoxy resin cured product A-4 obtained in Example 41, with an unnotched pendulum impact strength of 58 kJ / m. -2 .

[0221] As can be seen from Table 1 and Example 41, the acetal epoxy resin cured product provided by the present invention has excellent thermal properties, mechanical properties and impact resistance due to its structural design.

[0222] Examples 42 to 65 Examples 42-65 describe the degradation of some epoxy resin cured products in Table 1 to recover terephthalaldehyde and polyols, specifically including the following steps: 20 g of cured epoxy resin was immersed in 100 g of acidic degradation solution at a preset temperature for a preset time to ensure complete degradation and dissolution of the resin matrix in the degradation solution. The degradation solution was concentrated and extracted multiple times with 200 g of extractant under heating and stirring conditions. The organic phase obtained from the extraction was concentrated and purified to recover terephthalaldehyde. Excess sodium bicarbonate was added to the aqueous phase to neutralize it, causing the polyol to precipitate. After removing the aqueous phase, the organic matter was dissolved in 50 g of acetone, filtered to remove inorganic salts, and finally the acetone was removed to recover the polyol.

[0223] Thanks to the epoxy resin molecular structure design of this invention, its cured network can be completely degraded into substances with well-defined structures, significantly different properties, easy separation, and stability under acidic degradation solutions, thus achieving "closed-loop recycling." This solves the problems of existing epoxy resin networks where the degradation products have unclear structures, similar properties that make separation difficult, and the tendency for side reactions to occur during separation.

[0224] The only differences between Examples 42 to 65 are the epoxy resin cured products, the acidic degradation solution used, the degradation temperature and time, and the extractant, as shown in Table 3.

[0225] Table 3. Acidic degradation solution, degradation temperature and time, and extractant used in Examples 42-65 In summary, the epoxy resin monomer provided by this invention possesses excellent mechanical properties and heat resistance, along with high glass transition temperature and heat distortion temperature. Furthermore, its cured product can be completely degraded under acidic conditions into dialdehyde compounds, diketone compounds, and structurally defined polyhydroxy compounds. This epoxy resin monomer can be applied in biodegradable plastics, coatings, adhesives, and aerospace fields, demonstrating economic practicality and promising industrial application prospects. The preparation method of the epoxy resin monomer provided by this invention is simple and easy to industrialize.

[0226] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0227] All aspects, embodiments, features, and examples of this invention should be considered illustrative and used to explain and illustrate the invention, but not to limit the invention. The scope of the invention is defined only by the claims.

[0228] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims.

Claims

1. A closed-loop recyclable epoxy resin monomer, characterized in that, Its structure is shown in equations I-a, I-b, I-c, I-d, II-a, II-b, II-c, or II-d: ; ; R1 and R3 are independently selected from any one of H, CH3, and CH2CH3, and R2 is selected from... Any one of them; R4 is selected from Any one of them, R 5a R 5b R 5c R 5d Independent selection Any one of them.

2. A method for preparing a closed-loop recyclable epoxy resin monomer, characterized in that, include: A first reaction is carried out on a first mixed reaction system containing a dialdehyde compound, a dihydroxy compound, or a trihydroxy compound to obtain an acetal polyol intermediate. A second reaction is carried out on a second mixed reaction system containing the acetal polyol intermediate, epichlorohydrin, and hydroxide to obtain a ring-closed recyclable epoxy resin monomer.

3. The method for preparing the closed-loop recyclable epoxy resin monomer according to claim 2, characterized in that: The dialdehyde compounds include one or more combinations of terephthalaldehyde, isophthalaldehyde, o-phthalaldehyde, 2,5-furandialdehyde, ethylene glycol, and glutaraldehyde; And / or, the dihydroxy compound includes 1,4-cyclohexanediol and / or 1,6-hexanediol; And / or, the trihydroxy compound includes one or more combinations of 2-hydroxymethyl-1,3-propanediol, 1,1,1-tris(hydroxymethyl)ethane, and 1,1,1-tris(hydroxymethyl)propane; And / or, the hydroxide includes sodium hydroxide and / or potassium hydroxide; And / or, the mass ratio of the dialdehyde compound to the dihydroxy compound or trihydroxy compound is 1:2~4; And / or, the mass ratio of epichlorohydrin to acetal polyol intermediate is 1~30:1; And / or, the mass ratio of the sodium hydroxide to the acetal polyol intermediate is 1:1 to 20.

4. The method for preparing the closed-loop recyclable epoxy resin monomer according to claim 2 or 3, characterized in that: The temperature of the first reaction is 60~140℃; and / or the time of the first reaction is 0.5h~72h; And / or, the temperature of the second reaction is 10~100℃; and / or, the time of the second reaction is 0.5h~72h.

5. The method for preparing the closed-loop recyclable epoxy resin monomer according to claim 2 or 3, characterized in that: The first mixed reaction system further includes a first catalyst, which comprises one or more of the following: p-toluenesulfonic acid, citric acid, oxalic acid, methanesulfonic acid, sulfuric acid, hydrochloric acid, phosphoric acid, hydrogen-form Y zeolite, hydrogen-form Beta zeolite, H-mordenite, phosphotungstic acid, silyloidal molybdenum acid, cesium phosphotungstate, ammonium phosphotungstate, alumina, titanium dioxide, zirconium oxide, tungsten oxide, sulfonated polystyrene resin, perfluorosulfonated resin, acidified montmorillonite, acidified kaolin, acidified bentonite, aluminum phosphate, boron phosphate, sulfonated activated carbon, sulfonated graphene, titanium sulfate, tin sulfate, ferric sulfate, zirconium nitrate, aluminum chloride, ferric chloride, titanium tetrachloride, zinc chloride, trimethylaluminum, scandium trifluoromethanesulfonate, tin tetrachloride, iodine, and boron tribromide. And / or, the second mixed reaction system further includes a second catalyst, the second catalyst comprising one or more of tetrabutylammonium bromide, benzyltriethylammonium chloride, hexadecyltrimethylammonium bromide or tetraethylammonium bromide; And / or, the first mixed reaction system further includes a first organic solvent, the first organic solvent including one or more combinations of toluene, benzene, petroleum ether, ethyl acetate, n-hexane, cyclohexane, acetone, butanone, ethanol, and methanol; And / or, the second mixed reaction system further includes a second organic solvent, which includes one or more combinations of toluene, benzene, xylene, dichloromethane, chloroform, petroleum ether, n-hexane, cyclohexane, ethyl acetate, and nitrile.

6. The method for preparing the closed-loop recyclable epoxy resin monomer according to claim 5, characterized in that: The mass ratio of the first catalyst to the dialdehyde compound is 1:5~100; And / or, the mass ratio of the second catalyst to the acetal polyol intermediate is 1:5~100; And / or, the mass ratio of the first organic solvent to the dialdehyde compound is 1~20:1; And / or, the mass ratio of the second organic solvent to the dialdehyde compound is 1~20:1; And / or, the preparation method specifically includes: after the first reaction is completed, directly adding the second catalyst, epichlorohydrin and hydroxide to the reaction product containing the acetal polyol intermediate to carry out the second reaction.

7. A closed-loop recyclable epoxy resin monomer, characterized in that, It is prepared by the method for preparing the closed-loop recyclable epoxy resin monomer according to any one of claims 2-6.

8. A cured epoxy resin product, characterized in that, It is obtained by curing and crosslinking the recyclable epoxy resin monomer as described in claim 1 or 7.

9. A closed-loop recycling method for epoxy resin cured products, characterized in that, include: An epoxy resin curing product is obtained by curing and crosslinking epoxy resin monomers, wherein the epoxy resin monomers include the closed-loop recyclable epoxy resin monomers as described in claim 1 or 7. The epoxy resin cured product is degraded using an acidic degradation solution and then post-treated to obtain dialdehyde compounds or diketone compounds and polyols.

10. The method according to claim 9, characterized in that, The degradation temperature is above 25°C, and / or the degradation time is 4 h to 24 h.

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