Recyclable epoxy resin monomer and preparation method thereof

Abstract

The invention discloses a recyclable epoxy resin monomer and a preparation method thereof. The recyclable epoxy resin monomer comprises a bisphenol A skeleton and a structure containing an epoxy functional group, the structure containing the epoxy functional group can react with various curing agents, so that cured recyclable epoxy resin is generated; the bisphenol A type skeleton can be obtained by degrading traditional anhydride cured bisphenol A type epoxy resin. According to the invention, degradation can be carried out under certain conditions, the bisphenol A type skeleton raw material can be recovered again, and sustainable circulation is realized; the recyclable epoxy resin disclosed by the invention is wide in raw material source, has excellent physical and chemical properties including high strength, good weather resistance and excellent adhesion, is environment-friendly in an application process, and can reduce waste generation and resource consumption.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials and recycling thereof, and in particular to a recyclable epoxy resin monomer and a preparation method thereof. Background Art

[0002] With the widespread application of polymer materials in the fields of electronics, electrical engineering, construction, aerospace, etc., traditional epoxy resin has become one of the important materials due to its excellent mechanical properties and chemical resistance. However, the irreversible structure of epoxy resin after curing makes it difficult to recycle its waste, which is usually disposed of by landfill or incineration, which wastes resources and pollutes the environment. Therefore, it is of great practical significance to develop a recyclable epoxy resin to reduce the impact of industrial waste on the environment.

[0003] The research on recyclable epoxy resin in the prior art mainly focuses on the development of new epoxy resins with reversible chemical bonds, which dissociate and reassemble under the stimulation of temperature, light and pH value, so as to realize the reprocessing and degradation recycling of epoxy resins. For example, the prior art proposes a method of preparing epoxy resin using disulfide bonds and boron ester bonds, but this method cannot solve the recycling problem of bisphenol A epoxy resin on the market. Summary of the invention

[0004] In view of the above problems, the present invention aims to provide a recyclable epoxy resin monomer and a preparation method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] In one aspect, a recyclable epoxy resin monomer is provided, and the general structural formula of the recyclable epoxy resin monomer is as follows:

[0007]

[0008] In the formula: R represents a structure containing an epoxy functional group; n is greater than or equal to 0.

[0009] Preferably, in the general structural formula (1), R is selected from any one of the following structural formulas:

[0010]

[0011] On the other hand, a method for preparing the above-mentioned recyclable epoxy resin monomer is also provided, comprising the following steps:

[0012] S1: Obtain intermediate I, the general structural formula of intermediate I is as follows:

[0013]

[0014] S2: Intermediate II is prepared by the intermediate I. The general structural formula of the intermediate II is as follows:

[0015]

[0016] Wherein: X represents a structure containing a double bond, a hydroxyl group or a phenolic hydroxyl group; when X is a structure containing a double bond, the intermediate II is called intermediate II-1; when X is a structure containing a hydroxyl group or a phenolic hydroxyl group, the intermediate II is called intermediate II-2;

[0017] S3: The intermediate II-1 is treated with solvent S 4 Dissolve, then add 4 equivalents of sodium bicarbonate or more, and epoxidize the double bond with 2 to 6 equivalents of epoxidation reagent O; after the reaction is completed, quench the excess epoxidation reagent O; then extract, dry the organic layer and remove the solvent S 4 , obtaining the recyclable epoxy resin monomer;

[0018] The intermediate II-2 is dissolved with excess epichlorohydrin, and 0.05 equivalent of phase transfer catalyst C is added. 3 ; Add 2 to 6 equivalents of 10 to 50 wt% NaOH solution at 50 to 100° C., and continue the reaction for 6 to 12 hours after the addition is completed; after the reaction is completed, extract with deionized water to neutrality, dry the organic layer and remove the solvent to obtain the recyclable epoxy resin monomer.

[0019] Preferably, in the general structural formula (4), X is selected from any one of the following structural formulas:

[0020]

[0021] Preferably, in step S1, when n of the intermediate I is greater than or equal to 0, the intermediate I is obtained by degrading anhydride-cured bisphenol A epoxy resin;

[0022] When n of the intermediate I is 0, the intermediate I can also be prepared by the following steps:

[0023] Dissolve bisphenol A and 2.0 to 2.5 equivalents of glycidol in solvent S at a ratio of 1 g / 1 to 20 mL. 1 and add 0.05 to 1 equivalent of catalyst C 1 , reflux reaction for 6 to 10 hours; after the reaction is completed, purification is carried out to obtain the intermediate I.

[0024] Preferably, the degradation of anhydride-cured bisphenol A epoxy resin specifically comprises the following steps:

[0025] The anhydride-cured bisphenol A epoxy resin is placed in solvent S dand add catalyst C d , reflux reaction for 6 to 24 hours; after the reaction is completed, dissolve and precipitate, separate and obtain the intermediate I; when adding materials, add 10 to 100 mL of solvent S per gram of anhydride-cured bisphenol A epoxy resin d and 0.1-5g catalyst C d .

[0026] Preferably, the solvent S 1 is ethanol or methanol, the catalyst C 1 is triethylamine or pyridine; the solvent S d is an alcohol solvent, the catalyst C d It is an alkaline inorganic salt.

[0027] Preferably, in step S2, the intermediate II is prepared by the following steps:

[0028] Dissolve intermediate I in solvent S at a ratio of 1 g / 1 to 20 mL. 2 Then add 2 to 10 equivalents of aldehyde raw materials containing double bonds, hydroxyl groups or phenolic hydroxyl groups and 0.1 equivalent of catalyst C 2 and solvent S 2 An equal amount of dehydrating agent D was added to a water separator for reflux and water separation for 3 to 10 hours. After the reaction was completed, the system was concentrated using a rotary evaporator to obtain a crude product.

[0029] The crude product was treated with solvent S 3 Dilution followed by extraction to remove catalyst C 2 , then extracted with deionized water to neutrality, dried and removed solvent S 3 , to obtain the intermediate II.

[0030] Preferably, the solvent S 2 is N,N-dimethylformamide or dimethyl sulfoxide, the catalyst C 2 is any one of p-toluenesulfonic acid, sulfuric acid, and methanesulfonic acid; the dehydrating agent D is any one of petroleum ether, cyclohexane, and molecular sieves; the solvent S 3 It is any one of ethyl acetate, petroleum ether, toluene, dichloromethane and chloroform.

[0031] Preferably, in step S3, the solvent S 4 is dichloromethane or toluene; the epoxidation reagent O is m-chloroperoxybenzoic acid or peroxyacetic acid; the phase transfer catalyst C 3 It is tetrabutylammonium bromide or benzyltriethylammonium chloride.

[0032] The beneficial effects of the present invention are:

[0033] 1. Enhanced recyclability: The present invention introduces acetal reversible bonds to enable the epoxy resin to be chemically degraded under specific conditions, thereby achieving reversible depolymerization and reorganization of the epoxy resin structure, facilitating the recovery and reuse of bisphenol A derivatives, and significantly improving the recyclability of the epoxy resin.

[0034] 2. Efficient resource recycling: The present invention can realize the recycling of bisphenol A-based epoxy resin, reduce the dependence on non-renewable resources, and recover the bisphenol A derivative structure therein through chemical degradation technology, thereby realizing efficient recycling of resources and meeting the requirements of sustainable development.

[0035] 3. Environmental protection: Compared with traditional landfill and incineration treatment methods, the present invention reduces the pollution of industrial waste to the environment through chemical recovery methods, reduces the environmental burden of epoxy resin waste, and helps to achieve the goal of green environmental protection.

[0036] 4. Wide applicability: The recycling method of the present invention is not only applicable to the epoxy resin system of the present invention, but also to the anhydride-cured epoxy resin on the market, thereby realizing the conversion of traditional epoxy resins that are difficult to recycle, making them recyclable and sustainable, and further expanding the application scope of the technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. 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 creative labor.

[0038] Figure 1 1H NMR spectrum of the recyclable epoxy resin monomer of Example 1;

[0039] Figure 2 This is the 13C NMR spectrum of the recyclable epoxy resin monomer of Example 1;

[0040] Figure 3 This is the MS-TOF spectrum of the recyclable epoxy resin monomer in Example 1. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those generally understood by those of ordinary skill in the art to which this application belongs. The words "including" or "comprising" and the like used in the disclosure of the present invention mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0042] In one aspect, the present invention provides a recyclable epoxy resin monomer, the general structural formula of the recyclable epoxy resin monomer is as follows:

[0043]

[0044] In the formula: R represents a structure containing an epoxy functional group; n is greater than or equal to 0.

[0045] In a specific embodiment, in the general structural formula (1), R is selected from any one of the following structural formulas:

[0046]

[0047] It should be noted that the R groups in the above embodiments are only part of the R groups listed in the present invention, and other structures containing epoxy functional groups in the prior art may also be applicable to the present invention.

[0048] When the present invention is used, the R group on the recyclable epoxy resin monomer reacts with the curing agent to prepare a cured recyclable epoxy resin, thereby providing a recyclable epoxy resin.

[0049] On the other hand, the present invention also provides a method for preparing the above-mentioned recyclable epoxy resin monomer, comprising the following steps:

[0050] S1: Obtain intermediate I, the general structural formula of intermediate I is as follows:

[0051]

[0052] In a specific embodiment, when n of the intermediate I is greater than or equal to 0, the intermediate I is obtained by degrading anhydride-cured bisphenol A epoxy resin;

[0053] When n of the intermediate I is 0, the intermediate I can also be prepared by the following steps:

[0054] Dissolve bisphenol A and 2.0 to 2.5 equivalents of glycidol in solvent S at a ratio of 1 g / 1 to 20 mL. 1and add 0.05 to 1 equivalent of catalyst C 1 , reflux reaction for 6 to 10 hours; after the reaction is completed, purification is carried out to obtain the intermediate I.

[0055] It should be noted that the ratio of 1 g / 1-20 mL refers to the addition of 1-20 mL of solvent S per gram of the total weight of bisphenol A and glycidol. 1 ; Equivalent refers to the equivalent between the first substance in the step, and in the above embodiment, it is the equivalent between bisphenol A. The same applies to the subsequent steps.

[0056] In the above embodiment, the reaction process of bisphenol A and glycidol is as follows:

[0057]

[0058] In a specific embodiment, the solvent S 1 is ethanol or methanol, the catalyst C 1 It should be noted that the solvent S 1 Mainly for dissolving bisphenol A and glycidol, in addition to the preferred solvents of this embodiment, other solvents in the prior art that can achieve this purpose can also be applied to the present invention.

[0059] In the above embodiment, when the intermediate I is obtained by degrading the anhydride-cured bisphenol A epoxy resin, the specific value of n in the intermediate I is determined according to the degree of polymerization of the monomers in the degraded epoxy resin.

[0060] In a specific embodiment, the degradation of anhydride-cured bisphenol A epoxy resin specifically comprises the following steps:

[0061] The anhydride-cured bisphenol A epoxy resin is placed in solvent S d and add catalyst C d , reflux reaction for 6 to 24 hours; after the reaction is completed, dissolve and precipitate, separate and obtain the intermediate I; when adding materials, add 10 to 100 mL of solvent S per gram of anhydride-cured bisphenol A epoxy resin d and 0.1-5g catalyst C d .

[0062] In a specific embodiment, the solvent S d is an alcohol solvent, the catalyst C d It is an alkaline inorganic salt; optionally, the alcohol solvent is any one of ethanol, methanol, n-butanol, and n-hexanol, and the alkaline inorganic salt is potassium carbonate or potassium phosphate.

[0063] It should be noted that the solvent S dThere are two main functions. One is to act as an alcoholysis agent to break the ester bond; the other is to dissolve the degradation product for post-processing. In addition to the preferred solvent in this embodiment, other solvents in the prior art that can achieve this purpose can also be applied to the present invention.

[0064] S2: Intermediate II is prepared by the intermediate I. The general structural formula of the intermediate II is as follows:

[0065]

[0066] Wherein: X represents a structure containing a double bond, a hydroxyl group or a phenolic hydroxyl group; when X is a structure containing a double bond, the intermediate II is called intermediate II-1; when X is a structure containing a hydroxyl group or a phenolic hydroxyl group, the intermediate II is called intermediate II-2;

[0067] In a specific embodiment, in the general structural formula (4), X is selected from any one of the following structural formulas:

[0068]

[0069] In the above embodiment, when X is X 1 ~X 3 When the corresponding product is intermediate II-1, the R group in the final recyclable epoxy resin monomer corresponds to R 1 ~R 3 ; When X is X 4 When the corresponding product is intermediate Ⅱ-2, the R group in the final recyclable epoxy resin monomer corresponds to R 4 It should be noted that the X groups in the above embodiments are only part of the X groups listed in the present invention, and other structures containing double bonds, hydroxyl groups or phenolic hydroxyl groups in the prior art may also be applicable to the present invention.

[0070] In a specific embodiment, the intermediate II is prepared by the following steps:

[0071] Dissolve intermediate I in solvent S at a ratio of 1 g / 1 to 20 mL. 2 Then add 2 to 10 equivalents of aldehyde raw materials containing double bonds, hydroxyl groups or phenolic hydroxyl groups and 0.1 equivalent of catalyst C 2 and solvent S 2 An equal amount of dehydrating agent D was added to a water separator for reflux and water separation for 3 to 10 hours. After the reaction was completed, the system was concentrated using a rotary evaporator to obtain a crude product.

[0072] The crude product was treated with solvent S 3 Dilution followed by extraction to remove catalyst C 2 , then extracted with deionized water to neutrality, dried and removed solvent S 3 , to obtain the intermediate II.

[0073] In the above example, the reaction process for preparing intermediate II is as follows:

[0074]

[0075] In a specific embodiment, the solvent S 2 is N,N-dimethylformamide or dimethyl sulfoxide, the catalyst C 2 is any one of p-toluenesulfonic acid, sulfuric acid, and methanesulfonic acid; the dehydrating agent D is any one of petroleum ether, cyclohexane, and molecular sieves; the solvent S 3 It is any one of ethyl acetate, petroleum ether, toluene, dichloromethane and chloroform.

[0076] It should be noted that the solvent S 2 Mainly to dissolve intermediate Ⅰ, solvent S 3 Mainly for diluting the crude product, in addition to the preferred solvent of this embodiment, other solvents in the prior art that can achieve this purpose can also be applied to the present invention.

[0077] S3: The intermediate II-1 is treated with solvent S 4 Dissolve, then add 4 equivalents of sodium bicarbonate or more, and epoxidize the double bond with 2 to 6 equivalents of epoxidation reagent O; after the reaction is completed, quench the excess epoxidation reagent O; then extract, dry the organic layer and remove the solvent S 4 , obtaining the recyclable epoxy resin monomer;

[0078] The intermediate II-2 is dissolved with excess epichlorohydrin, and 0.05 equivalent of phase transfer catalyst C is added. 3 ; Add 2 to 6 equivalents of 10 to 50 wt% NaOH solution at 50 to 100° C., and continue the reaction for 6 to 12 hours after the addition is completed; after the reaction is completed, extract with deionized water to neutrality, dry the organic layer and remove the solvent to obtain the recyclable epoxy resin monomer.

[0079] In the above embodiment, the reaction process of preparing the recyclable epoxy resin monomer using intermediate II-1 is as follows:

[0080]

[0081] The reaction process of preparing the recyclable epoxy resin monomer using intermediate II-2 is as follows:

[0082]

[0083] In a specific embodiment, the solvent S 4is dichloromethane or toluene; the epoxidation reagent O is m-chloroperoxybenzoic acid or peroxyacetic acid; the phase transfer catalyst C 3 It is tetrabutylammonium bromide or benzyltriethylammonium chloride.

[0084] It should be noted that the solvent S 4 Mainly for dissolving intermediate II-1, in addition to the preferred solvents of this embodiment, other solvents in the prior art that can achieve this purpose can also be applied to the present invention.

[0085] Example 1

[0086] A recyclable epoxy resin monomer is prepared by the following steps:

[0087] (1) Synthesis of intermediate I (n=0)

[0088] Bisphenol A (100 g, 1 eq) and glycidol (75 g, 2.3 eq) were dissolved in 500 mL of ethanol, and triethylamine (4.4 g, 0.1 eq) was added, and the mixture was refluxed for 8 h. After the reaction was completed, ethanol and triethylamine in the system were removed by a rotary evaporator. Subsequently, the crude product was further purified by a chromatography column to obtain intermediate I (n=0) with a yield of 76%.

[0089] (2) Synthesis of intermediate II (X=X 1 )

[0090] In a single-necked flask, intermediate I (80g, n=0) was dissolved in 300mL N,N-dimethylformamide, tetrahydrobenzaldehyde (187g, 8eq) and p-toluenesulfonic acid (3.7g, 0.1eq) were added, and 300mL cyclohexane was added as a dehydrating agent. Finally, a water separator was added and refluxed for 8h. After the reaction was completed, cyclohexane, tetrahydrobenzaldehyde and N,N-dimethylformamide were removed by a rotary evaporator to concentrate the system. Ethyl acetate was added to the concentrate, extracted twice with sodium bicarbonate aqueous solution, and then extracted with water until the water layer was neutral. After drying the organic layer with anhydrous sodium sulfate, the solvent was removed. The crude product was further purified by a chromatography column to obtain intermediate II (X=X 1 ), yield 81%.

[0091] (3) Synthesis of recyclable epoxy resin monomer (R = R 1 )

[0092] Intermediate II (X=X 1) was dissolved in 500mL toluene and sodium bicarbonate (48g, 4eq) was added. The reaction was stirred in an ice-water bath with a mechanical stirrer, and 75wt% m-chloroperoxybenzoic acid (82g, 2.5eq) was added in batches. After the addition was completed, the reaction was continued at room temperature for 8h. A saturated solution of sodium sulfite was added and stirred for 1h to terminate the reaction. The organic phase was then extracted with 1wt% sodium hydroxide solution, water and saturated sodium chloride. Dry with sodium sulfate. Further purification was performed by chromatography to obtain a recyclable epoxy resin monomer (denoted as ReDGEBA, R=R 1 ), yield 62%.

[0093] The recyclable epoxy resin monomer was tested, and the 1H NMR spectrum was as follows: Figure 1 As shown, the 13C NMR spectrum is as follows Figure 2 As shown, the MS-TOF spectrum is as follows Figure 3 shown.

[0094] Figure 1 Chemical shifts of hydrogen atoms in: 1H NMR (400MHz, DMSO) δ7.09 (d, J = 8.6 Hz, 4H), 6.83 (d, J = 8.5 Hz, 4H), 4.67 (dddd, J = 27.7, 23.5, 4.5, 2.0 Hz, 2H), 4.35 (dd, J = 11.4, 4.8 Hz, 2H), 4.22–4.04 (m, 1H), 3.93 (dd, J = 4.8, 2.3 Hz ,5H),3.75(ddt,J=8.2,5.4,2.8Hz,2H),3.62(dtd,J=10.0,5.3,3.0Hz,1H),3.06(dd,J=8. 5,4.1Hz,4H),2.14–1.85(m,4H),1.57(s,7H),1.06(dddq,J=41.0,17.7,11.7,5.5Hz,2H). from Figure 1 It can be seen that each peak of the ionic liquid has its own identity, indicating that the synthesized product is successful.

[0095] Figure 2 Chemical shift of each carbon atom in: 13 C NMR(101MHz,DMSO)δ156.05,142.88,127.42,113.84,107.13–105.54(m),73.68,68.13(d),66.43(d),51.65(d) ,50.73,50.04,41.18,36.71–35.47(m),34.52–32.79(m),30.71,25.45(d),23.99,22.59,21.23(d),18.74(d). from Figure 2It can be seen that each peak has a clear identity, indicating that the product was successfully synthesized.

[0096] from Figure 3 It can be seen that the charge-to-mass ratio is the summed ion peak of the target molecular weight, indicating that the product was successfully synthesized.

[0097] Example 2

[0098] A recyclable epoxy resin monomer is prepared by the following steps:

[0099] (1) Synthesis of intermediate I (n=0)

[0100] Bisphenol A (100 g, 1 eq) and glycidol (75 g, 2.3 eq) were dissolved in 500 mL of ethanol, and triethylamine (4.4 g, 0.1 eq) was added, and the mixture was refluxed for 8 h. After the reaction was completed, ethanol and triethylamine in the system were removed by a rotary evaporator. Subsequently, the crude product was further purified by a chromatography column to obtain intermediate I (n=0) with a yield of 76%.

[0101] (2) Synthesis of intermediate II (X=X 4 )

[0102] In a single-necked flask, intermediate I (80g, n=0) was dissolved in 300mL N,N-dimethylformamide, p-hydroxybenzaldehyde (205g, 8eq) and p-toluenesulfonic acid (0.1eq, 3.7g) were added, and 300mL cyclohexane was added as a dehydrating agent. Finally, a water separator was added and refluxed for 8h. After the reaction was completed, cyclohexane and N,N-dimethylformamide were removed by a rotary evaporator to concentrate the system. Ethyl acetate was added to the concentrate, extracted twice with sodium bicarbonate solution, and then extracted with water until the water layer was neutral. After drying the organic layer with anhydrous sodium sulfate, the solvent was removed. The crude product was further purified by a chromatography column to remove hydroxybenzaldehyde to obtain intermediate II (X=X 4 ), yield 72%.

[0103] (3) Synthesis of recyclable epoxy resin monomer (R = R 4 )

[0104] The intermediate II-2 (20 g, X = X 4 ) was dissolved with excess epichlorohydrin (50eq), and tetrabutylammonium bromide (0.05eq) was added and mixed. 4 equivalents of 20wt% NaOH solution were added dropwise at 80°C. After the addition was completed, the reaction was continued for 8h. After the reaction was completed, deionized water was used to extract to neutrality, the organic layer was dried and the solvent was removed to obtain a recyclable epoxy resin monomer (R=R 4 ).

[0105] Example 3

[0106] A recyclable epoxy resin is prepared by the following steps:

[0107] In a flask, the recyclable epoxy resin monomer (R = R 1 ), 3-isobutylglutaric anhydride and N,N-dimethylbenzylamine were dissolved in dichloromethane and mixed thoroughly. After mixing evenly, the dichloromethane in the bottle was removed using a rotary evaporator at 60°C. The resulting flowable resin was then poured into a polytetrafluoroethylene mold and degassed in a vacuum oven at 80°C. The mold was then moved into a blast oven and cured at 100°C for 2h, then at 130°C for 2h, and finally at 160°C for 6h. A recyclable epoxy resin was obtained, denoted as ReDGEBA-BuGA.

[0108] Example 4

[0109] A method for recovering recyclable epoxy resin comprises the following steps:

[0110] (1) Degradation: 1.5 g potassium carbonate and 25 mL n-hexanol were added into a 100 mL single-necked flask with an air condenser, and 2.0 g ReDGEBA-BuGA recyclable epoxy resin was added into the system for reflux reaction for 6 h.

[0111] (2) Filtration: Use diatomaceous earth as a filter aid to assist in filtering out potassium carbonate in the system. Finally, use a small amount of methanol to rinse the filter cake.

[0112] (3) Extraction: The filtrate is extracted with water to wash the aqueous layer until the aqueous layer is neutral. The organic layer is removed by rotary evaporation to obtain a mixed degradation product.

[0113] (4) Rough separation: Flash column chromatography is used for rough separation. The spin-dried product is dissolved in a mixed solution of dichloromethane and a small amount of methanol, and silica gel powder with a mass twice that of the product to be separated is added and mixed, and the product is spin-dried again to allow the product to adhere to the silica gel powder. Subsequently, the column is loaded with 4 times the mass of silica gel powder, and the above product-silica gel powder mixture is added, and negative pressure is maintained. First, elute with 70 mL of dichloromethane to obtain a low-polarity phase; then, the residue is eluted with 70 mL of methanol. The above two products of different polarities are spin-dried, and the yield of the low-polarity phase (anhydride derivative) is 0.8 g, and the yield of the high-polarity phase is 1.8 g.

[0114] (5) Acid hydrolysis: The crude product of the high polar phase obtained in the previous step was dissolved in 30 mL of ethanol, and 0.55 g of p-toluenesulfonic acid monohydrate and 1 mL of water were added, and the mixture was reacted in an oil bath at 80° C. for 48 h. The reaction was quenched with potassium carbonate and the mixture was spin-dried to obtain an acid hydrolysis reaction mixture.

[0115] (6) Extraction: Dissolve the above acid hydrolysis reaction mixture with 70 mL of 10% ethanol in dichloromethane solution, and add 10 mL of water. Stir evenly and separate the liquids, then extract twice with water. The organic layer is spin-dried to obtain a crude product of intermediate I.

[0116] (7) Acetalization: Dissolve the crude product obtained in the previous step with 10 mL of N,N-dimethylformamide. Add 10 wt% of p-toluenesulfonic acid, 3 times the mass of tetrahydrobenzaldehyde and 60 mL of cyclohexane to the crude product, and reflux and dehydrate in an oil bath at 130°C for 6 h. After the reaction is completed, remove DMF, cyclohexane and excess THBA on a rotary evaporator. Then, add 50 mL of ethyl acetate to dissolve the system, extract twice with sodium bicarbonate aqueous solution, and then extract with water until the water layer is neutral. Subsequently, remove the ethyl acetate in the organic layer to obtain intermediate II (X=X 1 ) crude product. Subsequently, it was purified by column chromatography to obtain a refined intermediate II (X=X 1 ), yield 60%.

[0117] Example 5

[0118] Different from Example 1, the intermediate I of this example has n greater than 0 and is recovered from E51 epoxy resin (MHHPA-E51) cured with methylhexahydrophthalic anhydride; the intermediate II of this example (X=X 1 ) is obtained by recovering the intermediate Ⅰ and subjecting it to acetalization.

[0119] In this embodiment, the recovery of intermediate I specifically includes the following steps:

[0120] (1) Dehydration: 1.5 g potassium carbonate and 25 mL n-hexanol were added to a 100 mL single-necked flask with an air condenser, and 2.0 g MHHPA-E51 epoxy resin was added to the system for reflux reaction for 6 h.

[0121] (2) Filtration: Diatomaceous earth is used as a filter aid to assist in filtering out potassium carbonate; a small amount of methanol is used to elute the filter cake.

[0122] (3) Extraction: The filtrate was extracted with water and washed until the water layer was neutral. The organic layer was removed by rotary evaporation to obtain a mixed degradation product.

[0123] (4) Rough separation: Flash column chromatography is used for rough separation. The spin-dried product is dissolved in a mixed solution of dichloromethane and a small amount of methanol, and silica gel powder twice the mass of the product to be separated is added and mixed, and the product is spin-dried again to allow the product to adhere to the silica gel powder. Subsequently, the column is filled with four times the mass of silica gel powder, and the above product-silica gel powder mixture is added, and negative pressure is maintained. First, 70 mL of dichloromethane is used for elution to obtain a low-polarity phase; then, 70 mL of methanol is used to elute the residue. The above two products of different polarities are spin-dried, and the yield of the low-polarity phase is 1.26 g, and the high-polarity phase is 1.31 g. The high-polarity phase is the intermediate I.

[0124] In this embodiment, the acetalization of intermediate I to obtain intermediate II specifically includes the following steps:

[0125] Dissolve the intermediate I obtained in the previous step with 10 mL of N,N-dimethylformamide. Add 10 wt% of p-toluenesulfonic acid, three times the mass of tetrahydrobenzaldehyde and 10 mL of cyclohexane to the intermediate I, and reflux and dehydrate for 6 hours in an oil bath at 130°C. After the reaction is completed, remove DMF, cyclohexane and excess THBA on a rotary evaporator. Then, add 50 mL of ethyl acetate to dissolve the system, extract twice with sodium bicarbonate aqueous solution, and then extract with water until the water layer is neutral. Subsequently, remove the ethyl acetate in the organic layer to obtain intermediate II (X=X 1 ) crude product. Subsequently, it was purified by column chromatography to obtain a refined intermediate II (X=X 1 ) crude product, yield 45%.

[0126] In summary, the present invention introduces acetal bonds to enable epoxy resin to depolymerize under specific conditions, recover and reuse bisphenol A derivatives, and achieve the effect of sustainable resource utilization. In addition, bisphenol A derivatives can also be obtained from traditional anhydride-cured epoxy resins, converting difficult-to-recycle resins into easily recyclable and sustainable resins. Compared with the prior art, the present invention has significant progress.

[0127] The above description is only a representative embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the profession, without departing from the scope of the technical solution of the present invention, uses the above-disclosed technical contents to make some changes or modifications to the embodiments are equivalent embodiments of the present invention. However, any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A recyclable epoxy resin monomer, characterized in that: The general structural formula of the recyclable epoxy resin monomer is as follows: In the formula: R represents a structure containing an epoxy functional group; n is greater than or equal to 0.

2. The recyclable epoxy resin monomer according to claim 1, characterized in that: In the general structural formula (1), R is selected from any one of the following structural formulas:

3. The method for preparing a recyclable epoxy resin monomer according to claim 1 or 2, characterized in that: The following steps are involved: S1: Obtain intermediate I, the general structural formula of intermediate I is as follows: S2: Intermediate II is prepared by the intermediate I. The general structural formula of the intermediate II is as follows: Wherein: X represents a structure containing a double bond, a hydroxyl group or a phenolic hydroxyl group; when X is a structure containing a double bond, the intermediate II is called intermediate II-1; when X is a structure containing a hydroxyl group or a phenolic hydroxyl group, the intermediate II is called intermediate II-2; S3: dissolving the intermediate II-1 with solvent S4, then adding 4 equivalents or more of sodium bicarbonate, and epoxidizing the double bond with 2 to 6 equivalents of epoxidation reagent O; after the reaction is completed, quenching the excess epoxidation reagent O; then extracting, drying the organic layer and removing the solvent S4 to obtain the recyclable epoxy resin monomer; The intermediate II-2 is dissolved with excess epichlorohydrin, and 0.05 equivalent of phase transfer catalyst C3 is added; 2 to 6 equivalents of 10 to 50 wt% NaOH solution are added dropwise at 50 to 100° C., and the reaction is continued for 6 to 12 hours after the addition is completed; after the reaction is completed, deionized water is used to extract to neutrality, the organic layer is dried and the solvent is removed to obtain the recyclable epoxy resin monomer.

4. The method for preparing a recyclable epoxy resin monomer according to claim 3, characterized in that: In the general structural formula (4), X is selected from any one of the following structural formulas:

5. The method for preparing a recyclable epoxy resin monomer according to claim 3, characterized in that: In step S1, when n of the intermediate I is greater than or equal to 0, the intermediate I is obtained by degrading anhydride-cured bisphenol A epoxy resin; When n of the intermediate I is 0, the intermediate I can also be prepared by the following steps: Bisphenol A and 2.0 to 2.5 equivalents of glycidol are dissolved in solvent S1 at a ratio of 1 g / 1 to 20 mL, and 0.05 to 1 equivalent of catalyst C1 is added, and reflux reaction is carried out for 6 to 10 hours; after the reaction is completed, purification is carried out to obtain the intermediate I.

6. The method for preparing a recyclable epoxy resin monomer according to claim 5, characterized in that: Degrading anhydride-cured bisphenol A epoxy resin specifically comprises the following steps: The anhydride-cured bisphenol A epoxy resin is placed in solvent S d and add catalyst C d , reflux reaction for 6 to 24 hours; after the reaction is completed, dissolve and precipitate, separate and obtain the intermediate I; when adding materials, add 10 to 100 mL of solvent S per gram of anhydride-cured bisphenol A epoxy resin d and 0.1-5g catalyst C d .

7. The method for preparing a recyclable epoxy resin monomer according to claim 6, characterized in that: The solvent S1 is ethanol or methanol, the catalyst C1 is triethylamine or pyridine; the solvent S d is an alcohol solvent, the catalyst C d It is an alkaline inorganic salt.

8. The method for preparing a recyclable epoxy resin monomer according to claim 3, characterized in that: In step S2, the intermediate II is prepared by the following steps: Dissolve the intermediate I in the solvent S2 at a ratio of 1 g / 1-20 mL, then add 2-10 equivalents of an aldehyde raw material containing a double bond, a hydroxyl group or a phenolic hydroxyl group, 0.1 equivalent of a catalyst C2 and a dehydrating agent D equal to the solvent S2, add a water separator to reflux and separate water for 3-10 hours, and after the reaction is completed, use a rotary evaporator to concentrate the system to obtain a crude product; The crude product is diluted with solvent S3, then extracted to remove catalyst C2, and then extracted with deionized water until neutral, dried and solvent S3 is removed to obtain the intermediate II.

9. The method for preparing a recyclable epoxy resin monomer according to claim 8, characterized in that: The solvent S2 is N,N-dimethylformamide or dimethyl sulfoxide, the catalyst C2 is any one of p-toluenesulfonic acid, sulfuric acid, and methanesulfonic acid; the dehydrating agent D is any one of petroleum ether, cyclohexane, and molecular sieves; the solvent S3 is any one of ethyl acetate, petroleum ether, toluene, dichloromethane, and chloroform.

10. The method for preparing a recyclable epoxy resin monomer according to claim 3, characterized in that: In step S3, the solvent S4 is dichloromethane or toluene; the epoxidation reagent O is m-chloroperoxybenzoic acid or peroxyacetic acid; and the phase transfer catalyst C3 is tetrabutylammonium bromide or benzyltriethylammonium chloride.

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