Efficient method for pretreatment, degradation, and recovery of thermosetting epoxy resin based on mixed reaction-type solvothermal method

Abstract

The present invention provides an efficient method for pretreatment, degradation, and recovery of a thermosetting epoxy resin based on a mixed reaction-type solvothermal method, the efficient method comprising the following steps: S1: providing a cured epoxy resin; S2: adding the cured epoxy resin into dual solvents for pre-soaking to provide a pretreated sample, the dual solvents being selected from a halogenated alkane and an aliphatic amine; and S3: refluxing the pretreated sample in a low temperature interval, cooling to room temperature, carrying out first suction filtration to then obtain a first filtrate, mixing the first filtrate with water to precipitate out a precipitate or form a dispersion liquid, carrying out second suction filtration on the precipitate, and further separating the dispersion liquid and then performing recovery to obtain small molecules or oligomers into which the epoxy resin has degraded. In the present invention, the halogenated alkane-aliphatic amine mixed reaction-type dual solvents in different proportions are utilized for refluxing in the pre-soaking and low-temperature interval, and under the synergistic effect of the mixture obtained thereby and the original solvent molecules, not only can the thermosetting epoxy resin be degraded efficiently, but the process is also environmentally friendly and low in cost.

Description

An efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction-type solvothermal method Technical Field

[0001] The invention belongs to the technical field of epoxy resin recovery, and in particular relates to a high-efficiency method for pre-treatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method. Background Art

[0002] Epoxy resins have excellent physical and mechanical properties, electrical insulation properties, chemical corrosion resistance, heat resistance, and adhesive properties, and have been widely used in industrial fields such as machinery and electronics, aerospace, transportation, construction, and chemical engineering. The excellent performance of epoxy resins stems from the epoxy groups contained in their own molecular structure and the insoluble, infusible, three-dimensional network molecular structure formed after curing and cross-linking. However, these material performance characteristics also mean that they are difficult to degrade, making the recycling and reuse of waste epoxy resins difficult. The environmental pollution and resource waste caused by waste epoxy resins have become serious environmental, social, and economic problems in my country and even the world. Therefore, key technologies for the high-value recycling of waste epoxy resins need to be broken through.

[0003] At present, the technical paths for the recycling and reuse of waste epoxy resin are as follows:

[0004] 1) Mechanical method: The waste epoxy resin is mechanically crushed and ground into powder of a certain particle size, which is used as raw materials for the preparation of certain specific products or as filler materials for low-value applications. Although this technical process is relatively mature, it is essentially just a "solid waste transfer" and does not fundamentally achieve high-value recycling of waste epoxy resin. At the same time, the crushing and grinding process produces a large amount of dust, and the processing equipment is severely worn, which not only increases the cost of mechanical recycling, but also creates new environmental problems. For example, Dow Global Technologies Co., Ltd. in the United States uses a mechanical method to convert waste resin into toughening fillers. Although it is 100% efficient and fully converted, it only targets fiber-reinforced resin waste.

[0005] 2) Solution method: Depending on the reaction solvent or medium, chemical solution method recovery mainly includes alcoholysis, alkaline hydrolysis, hydrolysis, hydrogenolysis, etc. Under mild conditions, the thermosetting epoxy resin matrix is ​​decomposed into raw material monomers or its low molecular weight polymers by heating or chemical reaction, thereby realizing complex component separation and recycling. However, the types of resins that can be processed by a specific solvent or medium are limited, and the amount of solvent used is large, and part of the solvent is only used as a loosening agent and evaporates and loses, which is not only costly but also puts new pressure on the environment; in addition, the dissolution rate is slow, the processable object is single (i.e., it can only process a certain type of epoxy resin), the energy consumption is large, and the material requirements of the processing device equipment are high. Therefore, it is necessary to further improve the technical solutions for the recovery and recycling of waste epoxy resins to meet the needs of the circular economy.

[0006] Summary of the Invention

[0007] In view of the shortcomings of the prior art described above, the object of the present invention is to provide an efficient method for the pretreatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method and a preparation method thereof. The cured epoxy resin obtained under various standard curing conditions is subjected to pre-soaking and reflux in a mixed reaction type two-solvent range (for example, ≤150°C) to achieve the breaking of the main molecular bonds of most of the cured epoxy resins and achieve a degradation rate of approximately 100%, thereby solving the problems existing in the technical paths for the recovery, treatment and reuse of waste epoxy resins in the prior art.

[0008] To achieve the above-mentioned purpose and other related purposes, the present invention is achieved through the following technical solutions.

[0009] In one aspect, the present invention provides an efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method, comprising the following steps:

[0010] S1: providing cured epoxy resin;

[0011] S2: adding the cured epoxy resin to a dual solvent for pre-soaking to provide a pretreated sample; the dual solvent is selected from a halogenated alkane and an aliphatic amine;

[0012] S3: reflux the pretreated sample in a low temperature range, cool it to room temperature, obtain a first filtrate after the first filtration, mix the first filtrate with water to precipitate, filter the precipitate for a second time, further separate the dispersion and recover the epoxy resin degradation small molecules or oligomers.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] In order to achieve low energy consumption, environmental protection and high efficiency of solidified epoxy resin recycled raw material recovery and degradation treatment, the purpose of the present invention is to provide a thermosetting epoxy resin based on a mixed reaction type solvent thermal method for the pretreatment degradation and recovery of thermosetting epoxy resins. Compared with the existing mechanical method and solution method for recycling and reusing waste epoxy resins, the present invention adopts a mixed reaction type double solvent of halogenated alkanes and aliphatic amines in different proportions under pre-soaking and low temperature range reflux (for example, ≤150°C). The resulting mixture and the original solvent molecules work together to not only achieve high efficiency degradation, but also green and environmentally friendly, low cost, and can greatly promote the development of the recycling economy of waste epoxy resins. In addition, the present invention can process a variety of low cross-linking degree and high cross-linking degree epoxy resins of different types, has a wider range of applicability, and solves the singleness of the current degradation and recovery of epoxy resin technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG1 shows infrared spectra of dichloromethane, diethylenetriamine, and the reaction of dichloromethane and diethylenetriamine by heating.

[0016] FIG2 is a schematic diagram showing the pretreatment and degradation results of the cured bisphenol A diglycidyl ether epoxy resin in Example 1 of the present invention.

[0017] FIG3 shows infrared spectra of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin, bisphenol A diglycidyl ether epoxy resin degradation residue and recovered bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention.

[0018] FIG4 shows thermogravimetric and heat flow curves of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin, and recovered bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention.

[0019] FIG5 shows differential scanning calorimetry curves of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin, and recovered bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention.

[0020] FIG6 shows the cured bisphenol A diglycidyl ether epoxy resin and the recovered bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention. 13 C-NMR spectrum.

[0021] FIG7 shows the extracted ion chromatogram and base peak ion chromatogram of bisphenol A diglycidyl ether epoxy resin recovered in negative ion mode at m / z 537.284 in Example 1 of the present invention.

[0022] FIG8 shows the infrared spectra of diethylenetriamine in Example 1 of the present invention and the recovered diethylenetriamine.

[0023] FIG9 shows infrared spectra of bisphenol F diglycidyl ether, cured bisphenol F diglycidyl ether epoxy resin, bisphenol F diglycidyl ether epoxy resin degradation residue, and recovered bisphenol F diglycidyl ether epoxy resin according to Example 2 of the present invention.

[0024] FIG10 shows differential scanning calorimetry curves of bisphenol F diglycidyl ether, cured bisphenol F diglycidyl ether epoxy resin, and recovered bisphenol F diglycidyl ether epoxy resin according to Example 2 of the present invention.

[0025] Figure 11 shows the curing of bisphenol F diglycidyl ether epoxy resin and recovered bisphenol A diglycidyl ether epoxy resin according to Example 2 of the present invention. 13 C-NMR spectrum.

[0026] Figure 12 shows the infrared spectra of tris(4-hydroxyphenyl)methane triglycidyl ether, cured tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin, tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin degradation residue and recovered tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin in Example 3 of the present invention.

[0027] FIG. 13 is a schematic diagram showing the pretreatment and degradation results of the trimethylolpropane triglycidyl ether epoxy resin cured in Example 4.

[0028] FIG14 shows the infrared spectra of trimethylolpropane triglycidyl ether and trimethylolpropane triglycidyl ether epoxy resin cured with acid anhydride in Example 4.

[0029] FIG15 shows the infrared spectrum of tetrahydrophthalic acid diglycidyl ester and tetrahydrophthalic acid diglycidyl ester epoxy resin cured with acid anhydride in Example 5.

[0030] FIG16 shows the infrared spectrum of diglycidyl tetrahydrophthalate and amine-cured diglycidyl tetrahydrophthalate epoxy resin in Example 6.

[0031] FIG17 is a schematic diagram showing the pretreatment and degradation results of commercial E51 ( FIG17 a ) and E44 ( FIG17 b ) epoxy resins cured in Examples 7 and 8.

[0032] FIG18 is a schematic diagram showing the pretreatment and degradation results of the bisphenol A diglycidyl ether epoxy resin cured in Comparative Example 1 and Comparative Example 2 using diethylenetriamine alone ( FIG18 a ) and dichloromethane alone ( FIG18 b ). DETAILED DESCRIPTION

[0033] Below, with appropriate reference to the accompanying drawings, a detailed description is provided of an embodiment of the present application's efficient method for pretreatment, degradation, and recovery of thermosetting epoxy resins based on a mixed reaction-type solvent thermal method. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0034] The present invention addresses the problems existing in the current technical approaches for the recycling and reuse of waste epoxy resins, and invents an efficient method for the pretreatment, degradation, and recovery of thermosetting epoxy resins based on a mixed reaction-type solvent thermal method. Specifically, by reacting a mixed reaction-type dual solvent of a halogenated alkane and an aliphatic amine in different proportions under pre-soaking and reflux in a low-temperature range (e.g., ≤150°C), the resulting mixture and the original solvent molecules synergistically act to further increase the degradation or bond breaking selectivity and enhance the nucleophilicity, thereby achieving multi-selective and efficient degradation of the cured epoxy resin. On the other hand, the dual solvent is fully utilized in this degradation process, both acting as degradation reactants, thereby avoiding evaporation and loss waste. The main solvent component can also be greenly recovered by distillation, and the small molecules or oligomer degradation products obtained by degradation can also be further recycled. This method is applicable to a variety of low-crosslinked and highly crosslinked cured epoxy resins. The epoxy resins studied are broad and most commonly used, including typical epoxy resins such as bisphenol A epoxy resin, bisphenol F epoxy resin, polyphenol glycidyl ether epoxy resin, aliphatic glycidyl ether epoxy resin, glycidyl ester epoxy resin, and glycidyl amine epoxy resin. This inventive method can achieve a degradation rate of up to approximately 100% for the most common epoxy resin cured products. Based on this, this application has been completed.

[0035] The present invention provides an efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method, comprising the following steps:

[0036] S1: providing cured epoxy resin;

[0037] S2: adding the cured epoxy resin to a dual solvent for pre-soaking to provide a pretreated sample; the dual solvent is selected from a halogenated alkane and an aliphatic amine;

[0038] S3: reflux the pretreated sample in a low temperature range to efficiently degrade the thermosetting epoxy resin, cool it to room temperature, and obtain a first filtrate after the first filtration. The first filtrate is mixed with water to precipitate or form a dispersion. The precipitate is filtered for a second time, and the dispersion is further separated and recovered to obtain epoxy resin degraded small molecules or oligomers.

[0039] In the efficient method for pretreatment, degradation, and recovery of thermosetting epoxy resins provided by the present invention, step S1 is to provide a cured epoxy resin. In some embodiments, the method for preparing the cured epoxy resin comprises: mixing and stirring an epoxy resin monomer and a curing agent, and curing the mixture at room temperature or under heating to obtain a cured epoxy resin; wherein the curing agent is selected from an anhydride curing agent and / or an amine curing agent. In a specific embodiment, a certain amount of epoxy resin monomer and curing agent are weighed into a beaker, stirred for a period of time, poured into a mold, vacuumed to remove the internal air, and cured under certain curing conditions to obtain a cured epoxy resin.

[0040] In step S1 of the present invention, in some embodiments, the epoxy resin monomer can be a combination of one or more of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, tris(4-hydroxyphenyl)methane triglycidyl ether, trimethylolpropane triglycidyl ether, and tetrahydrophthalic acid diglycidyl ether.

[0041] In step S1 of the present invention, in some embodiments, the anhydride curing agent can be a combination of one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenylsuccinic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride or trimellitic anhydride.

[0042] In step S1 of the present invention, in some embodiments, the amine curing agent is selected from one or more combinations of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, meta-phenylenediamine, meta-phenylenediamine, diaminodiphenylmethane, bis(4-amino-3-methylcyclohexyl)methane or bis(4-aminocyclohexyl)methane.

[0043] In some embodiments, step S1 of the present invention may further include a phenolic accelerator, also known as a phenolic epoxy resin curing accelerator. In a specific embodiment, a certain amount of epoxy resin monomer, curing agent, and phenolic accelerator are weighed in a beaker, stirred for a period of time, poured into a mold, and vacuumed to remove the internal air. The mold is then cured under certain curing conditions to obtain a cured epoxy resin.

[0044] In step S1 of the present invention, in some embodiments, the phenolic accelerator is selected from one or more combinations of phenol, o-cresol, m-cresol, resorcinol, tris(dimethylaminomethyl)phenol or nonylphenol.

[0045] In step S1 of the present invention, the amount of monomer used is for providing a cured product, and its amount can be increased as needed. In some embodiments, the amount of the epoxy resin monomer used is ≥ 20 g. In specific embodiments, the amount of the epoxy resin monomer used can also be, for example, 20-50 g, 20-30 g, 30-40 g, or 40-50 g.

[0046] In step S1 of the present invention, in some embodiments, the amount of the curing agent is 10% to 70% of the amount of the epoxy resin monomer. In specific embodiments, the amount of the curing agent is 10% to 30%, 30% to 50%, or 50% to 70% of the amount of the epoxy resin monomer.

[0047] In step S1 of the present invention, in some embodiments, the amount of the phenolic accelerator is 0% to 1.5% of the amount of the epoxy resin monomer. In specific embodiments, the amount of the phenolic accelerator is 0% to 1.5%, 0% to 0.1%, 0.1% to 0.5%, 0.5% to 1%, 1% to 3%, or 3% to 5%, etc., of the amount of the epoxy resin monomer.

[0048] In step S1 of the present invention, the stirring time is generally not limited. In some embodiments, the stirring time is, for example, ≥ 5 minutes. In specific embodiments, the stirring time can be, for example, 5 to 10 minutes, 10 to 15 minutes, or 15 to 20 minutes.

[0049] In step S1 of the present invention, the curing temperature can be, for example, room temperature, 100°C to 150°C, 100°C to 120°C, or 120°C to 150°C. All room temperatures mentioned in this application are known in the art, for example, 20°C to 25°C.

[0050] In step S1 of the present invention, the curing time is ≥ 0.5 h, for example, 0.5 to 2 h, 2 to 10 h, 2 to 4 h, 4 to 6 h, 6 to 8 h, or 8 to 10 h.

[0051] In the efficient method for pretreatment, degradation, and recovery of thermosetting epoxy resins provided herein, step S2 involves pre-soaking the cured epoxy resin in a dual solvent to provide a pretreated sample. The dual solvent is selected from halogenated alkanes and aliphatic amines. In a specific embodiment, a predetermined amount of cured epoxy resin is weighed into a round-bottom flask, and the dual solvent is added in a predetermined proportion. The sample is then sealed in a cool, dry environment and stored for a period of time for pre-soaking.

[0052] In step S2 of the present invention, in some embodiments, the halogenated alkane is selected from one or more combinations of dichloromethane, dichloroethane, dichloropropane, chloroform and trichloroethane.

[0053] In step S2 of the present invention, in some embodiments, the aliphatic amine is selected from one or more combinations of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, bis(4-amino-3-methylcyclohexyl)methane or bis(4-aminocyclohexyl)methane.

[0054] In step S2 of the present invention, the amount of the cured epoxy resin can be increased as needed. In some embodiments, the amount of the cured epoxy resin is ≥ 2 g. Preferably, the amount of the cured epoxy resin is 2 g to 5 g.

[0055] In step S2 of the present invention, in some embodiments, the mass ratio of the cured epoxy resin to the dual solvent is 2-5:10-20. In specific embodiments, the mass ratio of the cured epoxy resin to the dual solvent can be, for example, 2-3:10-20, 3-5:10-20, etc.

[0056] In step S2 of the present invention, the mass ratio of the halogenated alkane to the aliphatic amine in the dual solvent is ≤ 1. Preferably, the mass ratio of the halogenated alkane to the aliphatic amine is 0.05 to 1. Alternatively, the mass ratio of the halogenated alkane to the aliphatic amine can be, for example, 0.05 to 0.1, 0.1 to 0.3, 0.3 to 0.5, 0.5 to 0.8, or 0.8 to 1. Figure 1 shows infrared spectra before and after the dual solvent reaction.

[0057] In step S2 of the present invention, the pre-soaking time is generally not limited. In some embodiments, the pre-soaking time is, for example, ≥ 0.5 h.

[0058] In the efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin provided by the present invention, step S3 is to reflux the pretreated sample in a low temperature range to efficiently degrade the thermosetting epoxy resin, cool it to room temperature, and filter it for the first time to obtain a first filtrate. The first filtrate is mixed with water to precipitate or form a dispersion. The precipitate is filtered for a second time, and the dispersion is further separated and recovered to obtain epoxy resin degraded small molecules or oligomers. The epoxy resin degraded small molecules or oligomers are recyclable.

[0059] In step S3 of the present invention, the temperature in the low temperature range is ≤ 150° C. Preferably, the temperature in the low temperature range is 100° C. to 150° C. Optionally, the temperature in the low temperature range is, for example, 100° C. to 120° C., or 120° C. to 150° C.

[0060] In step S3 of the present invention, the reflux time is ≤70 mins. Preferably, the reflux time is 30 mins to 70 mins.

[0061] In step S3 of the present invention, the second filtrate after suction filtration is distilled to recover the main solvent component. Specifically, the collected filtrate is subjected to atmospheric distillation at a certain temperature for a period of time to recover the main solvent component. The recovered main solvent component mainly includes aliphatic amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, bis(4-amino-3-methylcyclohexyl)methane, or bis(4-aminocyclohexyl)methane. The temperature is 100-150°C, and the atmospheric distillation time is 2-8 hours.

[0062] In step S3 of the present invention, the epoxy resin degradation small molecules or oligomers are recovered after filtration, wherein the molecular weight of the epoxy resin degradation small molecules is ≤500 and the molecular weight of the oligomers is ≤1500.

[0063] The following describes the implementation of the present invention through specific embodiments. People skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0064] Before further describing the specific embodiments of the present invention, it should be understood that the scope of the present invention is not limited to the specific embodiments described below. It should also be understood that the terminology used in the examples is intended to describe specific embodiments and is not intended to limit the scope of the present invention. The experimental procedures in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0065] When the embodiments provide numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the understanding of the prior art by those skilled in the art and the description of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention may also be used to implement the present invention.

[0066] Example 1

[0067] In this embodiment, a highly efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method is provided, and the steps are as follows:

[0068] S1: Weigh 20 g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of bisphenol A diglycidyl ether as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120°C for 2 h and at 150°C for 4 h to obtain a cured bisphenol A diglycidyl ether epoxy resin.

[0069] S2: Weigh 2 g of cured bisphenol A diglycidyl ether epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 h for pre-soaking.

[0070] S3: The pretreated sample was refluxed at 130°C for 50 minutes, cooled to room temperature and filtered to obtain the undegraded epoxy resin residue, which was placed in a 60°C oven for drying and weighed to obtain 0.0087g of cured bisphenol A diglycidyl ether epoxy resin degradation residue, with a degradation rate of up to 99.56%; at the same time, the filtrate was dropped into water and mixed with water to precipitate, and filtered to obtain the recovered epoxy resin, which was placed in a 60°C oven for drying and weighed to obtain 0.9551g of recovered bisphenol A diglycidyl ether epoxy resin; the filtrate was collected and distilled at a certain temperature (130°C) for a period of time (6h) to obtain recovered diethylenetriamine.

[0071] From the schematic diagram of FIG2 , it can be seen that the residue of bisphenol A diglycidyl ether epoxy resin after degradation by mixed reaction type solvent thermal method is less, and the spectrum of recovered bisphenol A diglycidyl ether epoxy resin measured by infrared spectroscopy ( FIG3 ) shows that the main chain skeleton of bisphenol A diglycidyl ether epoxy resin is not destroyed after degradation, and at 1731 cm -1 The C=O peak intensity of the ester group at the position of bisphenol A diglycidyl ether epoxy resin decreased significantly, indicating that the ester bond of the bisphenol A diglycidyl ether epoxy resin was cleaved. The thermogravimetric curve (Figure 4) and the measured glass transition temperature (Figure 5) show that the recovered bisphenol A diglycidyl ether epoxy resin is composed of small molecules or oligomers. The above conclusion is confirmed by elemental analysis (Table 1) and 13 This was further confirmed by C-NMR (Figure 6). After degradation, no ester groups were present at 173 ppm. This indicates that the degradation reaction in the mixed reaction solvent thermal method is primarily achieved by breaking down the ester groups. The extracted ion chromatogram and base peak ion chromatogram of the recovered bisphenol A diglycidyl ether epoxy resin at m / z 537.284 measured by liquid chromatography-mass spectrometry (Figure 7) show a significant decrease in molecular weight, further demonstrating that the mixed reaction solvent thermal method effectively degrades the polymer into small molecules or oligomers. The infrared spectrum of the recovered solvent is compared with the originally purchased diethylenetriamine (Figure 8). The peak patterns are essentially the same, indicating that the recovered solvent is primarily composed of diethylenetriamine.

[0072] Table 1 Elemental analysis of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin and recovered bisphenol A diglycidyl ether epoxy resin Example 1

[0073] Example 2

[0074] In this embodiment, an effective solution for efficient solvent thermal degradation and recovery of various epoxy resins cured with thermosetting anhydrides and amines based on dual-solvent room temperature pretreatment is provided. The steps are as follows:

[0075] S1: Weigh 20 g of bisphenol F diglycidyl ether, 70% of the mass of bisphenol F diglycidyl ether as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of bisphenol F diglycidyl ether as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120° C. for 2 h and at 150° C. for 4 h to obtain a cured bisphenol F diglycidyl ether epoxy resin.

[0076] S2: Weigh 2 g of cured bisphenol F diglycidyl ether epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 h for pre-soaking.

[0077] S3: The pretreated sample was refluxed at 130°C for 50 minutes, cooled to room temperature and filtered to obtain the undegraded epoxy resin residue, which was placed in a 60°C oven for drying and weighed to obtain 0.0573g of cured bisphenol F diglycidyl ether epoxy resin degradation residue, with a degradation rate of up to 97.14%; at the same time, the filtrate was dropped into water and mixed with water to precipitate, and filtered to obtain the recovered epoxy resin, which was placed in a 60°C oven for drying and weighed to obtain 1.0643g of recovered bisphenol F diglycidyl ether epoxy resin; the filtrate was collected and distilled at a certain temperature (130°C) for a period of time (6h) to obtain recovered diethylenetriamine.

[0078] Similar to the characterization results of bisphenol A diglycidyl ether epoxy resin, the infrared spectrum of the recovered bisphenol F diglycidyl ether epoxy resin (Figure 9) shows that the main chain skeleton of the bisphenol F diglycidyl ether epoxy resin is not destroyed after degradation, and the main chain skeleton of the bisphenol F diglycidyl ether epoxy resin at 1730 cm -1 The C=O peak intensity of the ester group at the position of bisphenol F diglycidyl ether epoxy resin decreased significantly, indicating that the ester bond of bisphenol F diglycidyl ether epoxy resin was cleaved. The measured glass transition temperature (Figure 10) shows that the recycled bisphenol F diglycidyl ether epoxy resin is composed of small molecules or oligomers. The above conclusion is 13 This was further confirmed by C-NMR (Figure 11). After degradation, no ester groups were found at 173 ppm. This indicates that the degradation reaction in the mixed reaction-type solvothermal method is mainly achieved by cleaving the ester groups.

[0079] Example 3

[0080] In this embodiment, an effective solution for efficient solvent thermal degradation and recovery of various epoxy resins cured with thermosetting anhydrides and amines based on dual-solvent room temperature pretreatment is provided. The steps are as follows:

[0081] S1: Weigh 20 g of tris(4-hydroxyphenyl)methane triglycidyl ether, 70% of the mass of tris(4-hydroxyphenyl)methane triglycidyl ether by weight of methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of tris(4-hydroxyphenyl)methane triglycidyl ether by weight of tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120° C. for 2 h and at 150° C. for 4 h to obtain a cured tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin.

[0082] S2: Weigh 2 g of cured tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 h for pre-soaking.

[0083] S3: The pretreated sample was refluxed at 150° C. for 70 minutes, cooled to room temperature and filtered to obtain the undegraded epoxy resin residue. The residue was placed in a 60° C. oven for drying and weighed to obtain 0.0888 g of cured tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin degradation residue, with a degradation rate of up to 95.56%. At the same time, the filtrate was dropped into water and mixed with water to precipitate, and filtered to obtain a recovered epoxy resin. The residue was placed in a 60° C. oven for drying and weighed to obtain 0.5276 g of recovered tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin. The filtrate was collected and distilled at a certain temperature (130° C.) for a period of time (6 hours) to obtain recovered diethylenetriamine.

[0084] From the infrared spectrum of the recovered tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin (Figure 12), it can be seen that the main chain skeleton of the tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin is not destroyed after degradation, and the main chain skeleton of the tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin is not destroyed. -1 The C=O peak intensity of the ester group at α-Hydroxyphenylmethane triglycidyl ether epoxy resin decreased significantly, indicating that the ester bond of tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin was cleaved. This shows that the mixed reaction type solvothermal method degrades the polymer into small molecules or oligomers.

[0085] Example 4

[0086] In this embodiment, an effective solution for efficient solvent thermal degradation and recovery of various epoxy resins cured with thermosetting anhydrides and amines based on dual-solvent room temperature pretreatment is provided. The steps are as follows:

[0087] S1: Weigh 20 g of trimethylolpropane triglycidyl ether, 70% of the mass of trimethylolpropane triglycidyl ether as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of trimethylolpropane triglycidyl ether as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120° C. for 2 h and at 150° C. for 4 h to obtain a cured trimethylolpropane triglycidyl ether epoxy resin.

[0088] S2: Weigh 2 g of cured trimethylolpropane triglycidyl ether epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 h for pre-soaking.

[0089] S3: The pretreated sample was refluxed at 150° C. for 70 minutes, then cooled to room temperature and filtered. There was very little filtration residue, that is, the undegraded epoxy resin was close to zero, and the degradation rate was as high as approximately 100%.

[0090] As can be seen from the schematic diagram of Figure 13, there is substantially no residue after the cured trimethylolpropane triglycidyl ether epoxy resin is degraded by the mixed reaction type solvent thermal method. The spectrum of the cured trimethylolpropane triglycidyl ether epoxy resin was measured by infrared spectroscopy (Figure 14). As can be seen from the figure, the cured trimethylolpropane triglycidyl ether epoxy resin has a peak at 1729 cm -1 The C=O peak intensity in the ester group at is higher, indicating that the cured trimethylolpropane triglycidyl ether epoxy resin contains ester bonds.

[0091] Example 5

[0092] In this embodiment, an effective solution for efficient solvent thermal degradation and recovery of various epoxy resins cured with thermosetting anhydrides and amines based on dual-solvent room temperature pretreatment is provided. The steps are as follows:

[0093] S1: Weigh 20 g of diglycidyl tetrahydrophthalate, 70% of the mass of diglycidyl tetrahydrophthalate as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of diglycidyl tetrahydrophthalate as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120° C. for 2 h and at 150° C. for 4 h to obtain a cured diglycidyl tetrahydrophthalate epoxy resin.

[0094] S2: Weigh 2 g of cured tetrahydrophthalic acid diglycidyl ester epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 hours for pre-soaking.

[0095] S3: The pretreated sample was refluxed at 150° C. for 70 minutes, then cooled to room temperature and filtered. There was almost no residue after filtration, that is, the undegraded epoxy resin was almost zero, and the degradation rate was as high as approximately 100%.

[0096] The spectrum of the cured tetrahydrophthalic acid diglycidyl ester epoxy resin was measured by infrared spectroscopy (Figure 15). It can be seen from the figure that the cured tetrahydrophthalic acid diglycidyl ester epoxy resin has a peak at 1726 cm -1 The C=O peak intensity in the ester group at is higher, indicating that the cured tetrahydrophthalic acid diglycidyl ester epoxy resin contains ester bonds.

[0097] Example 6

[0098] In this embodiment, an effective solution for efficient solvent thermal degradation and recovery of various epoxy resins cured with thermosetting anhydrides and amines based on dual-solvent room temperature pretreatment is provided. The steps are as follows:

[0099] S1: Weigh 20 g of diglycidyl tetrahydrophthalate and 12% of the mass of diethylenetriamine curing agent in a beaker, stir for a while, pour into a mold, vacuum to remove the internal air, gel at 25°C for 30 minutes and cure at 120°C for 2 hours to obtain a cured diglycidyl tetrahydrophthalate epoxy resin.

[0100] S2: Weigh 2 g of cured tetrahydrophthalic acid diglycidyl ester epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 hours for pre-soaking.

[0101] S3: The pretreated sample was refluxed at 130° C. for 50 minutes, cooled to room temperature, and filtered. There was almost no residue after filtration, that is, the undegraded epoxy resin was close to zero, and the degradation rate was as high as approximately 100%.

[0102] The spectrum of tetrahydrophthalic acid diglycidyl ester epoxy resin cured by diethylenetriamine was measured by infrared spectroscopy (Figure 16). It can be seen from the figure that the cured tetrahydrophthalic acid diglycidyl ester epoxy resin has a peak at 1722 cm -1 The C=O peak intensity in the ester group at is higher, indicating that the diethylenetriamine-cured tetrahydrophthalic acid diglycidyl ester epoxy resin contains ester bonds.

[0103] Example 7

[0104] In this embodiment, a highly efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method is provided, and the steps are as follows:

[0105] S1: Weigh 20 g of E51 resin (Phoenix brand) and 25 g of commercially available modified methyltetrahydrophthalic anhydride in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 80°C for 2 h as recommended in the product instructions to obtain cured commercial E51 epoxy resin.

[0106] S2: Weigh 2 g of cured commercial E51 epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a cool, dry environment for 48 h for pre-soaking.

[0107] S3: The pretreated sample was refluxed at 130°C for 50 min, cooled to room temperature, and filtered. The filtered residue was the undegraded epoxy resin. After drying in a 60°C oven, only 0.0007 g of undegraded residue of cured commercial E51 epoxy resin was weighed, with a degradation rate of up to 99.97% (Figure 17a).

[0108] Example 8

[0109] In this embodiment, a highly efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method is provided, and the steps are as follows:

[0110] S1: Weigh 20 g of E44 resin (Phoenix brand) and 25 g of commercially available modified methyltetrahydrophthalic anhydride in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 80°C for 2 h as recommended in the product instructions to obtain cured commercial E44 epoxy resin.

[0111] S2: Weigh 2 g of cured commercial E44 epoxy resin in a round-bottom flask, then add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool, dry environment for 48 h for pre-soaking.

[0112] S3: The pretreated sample was refluxed at 130°C for 50 minutes, cooled to room temperature, and filtered. The filtered residue was the undegraded epoxy resin. After drying in a 60°C oven, only 0.0002 g of undegraded residue of cured commercial E44 epoxy resin was weighed, with a degradation rate of up to 99.99% (Figure 17b).

[0113] Comparative Example 1

[0114] In this embodiment, a comparative experiment was conducted with an efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method. The steps are as follows:

[0115] S1: Weigh 20 g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of bisphenol A diglycidyl ether as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120°C for 2 h and at 150°C for 4 h to obtain a cured bisphenol A diglycidyl ether epoxy resin.

[0116] S2: 2 g of cured bisphenol A diglycidyl ether epoxy resin was weighed in a round-bottom flask, 11 g of dichloromethane was added separately, and the mixture was sealed and stored in a cool and dry environment for 48 h for pre-soaking.

[0117] S3: The pretreated sample was refluxed at 130°C for 50 minutes, cooled to room temperature and filtered. The filtered residue was the undegraded epoxy resin. After drying in a 60°C oven, 2.3189 g of cured bisphenol A diglycidyl ether epoxy resin degradation residue was obtained by weighing, which did not show any degradation effect (Figure 18a).

[0118] Comparative Example 2

[0119] In this embodiment, a comparative experiment was conducted with an efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method. The steps are as follows:

[0120] S1: Weigh 20 g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether as a methyltetrahydrophthalic anhydride curing agent, and 1% of the mass of bisphenol A diglycidyl ether as a tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, vacuum to remove internal air, and cure at 120°C for 2 h and at 150°C for 4 h to obtain a cured bisphenol A diglycidyl ether epoxy resin.

[0121] S2: 2 g of cured bisphenol A diglycidyl ether epoxy resin was weighed in a round-bottom flask, and 11 g of diethylenetriamine was added separately. The mixture was sealed and stored in a cool and dry environment for 48 h for pre-soaking.

[0122] S3: The pretreated sample was refluxed at 130°C for 50 minutes, cooled to room temperature and filtered. The filtered residue was the undegraded epoxy resin. After drying in a 60°C oven, 2.7575 g of cured bisphenol A diglycidyl ether epoxy resin degradation residue was obtained by weighing, which showed no degradation effect (Figure 18b).

[0123] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. An efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method, characterized in that: The steps include: S1: providing cured epoxy resin; S2: adding the cured epoxy resin into a dual solvent for pre-immersion to provide a pre-treated sample; the dual solvent is selected from halogenated alkanes and aliphatic amines; S3: reflux the pretreated sample in a low temperature range, cool it to room temperature, obtain a first filtrate after the first filtration, mix the first filtrate with water to precipitate or form a dispersion, filter the precipitate for a second time, further separate the dispersion and recover the epoxy resin degradation small molecules or oligomers.

2. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S1, the preparation method of the cured epoxy resin includes: mixing and stirring the epoxy resin monomer and the curing agent, and curing at room temperature or by heating to obtain the cured epoxy resin; wherein the curing agent is selected from anhydride curing agent and / or amine curing agent.

3. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method as claimed in claim 2, characterized in that: The epoxy resin monomer is selected from one or more combinations of bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, tris(4-hydroxyphenyl)methane triglycidyl ether, trimethylolpropane triglycidyl ether, and tetrahydrophthalic acid diglycidyl ether; And / or, the acid anhydride curing agent is selected from a combination of one or more of phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylnadic anhydride, dodecenylsuccinic anhydride, pyromellitic anhydride, benzophenone tetracarboxylic anhydride or trimellitic anhydride; And / or, the amine curing agent is selected from one or more combinations of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, meta-phenylenediamine, meta-phenylenediamine, diaminodiphenylmethane, bis(4-amino-3-methylcyclohexyl)methane or bis(4-aminocyclohexyl)methane; And / or, further comprising a phenolic accelerator, the epoxy resin monomer, the curing agent and the phenolic accelerator are mixed and stirred; And / or, the epoxy resin monomer is used in an amount of ≥20 g; And / or, the amount of the curing agent is 10% to 70% of the amount of the epoxy resin monomer.

4. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method as claimed in claim 3, characterized in that: The phenolic accelerator is selected from one or more combinations of phenol, o-cresol, m-cresol, resorcinol, tris(dimethylaminomethyl)phenol or nonylphenol; And / or, the amount of the phenolic accelerator is 0% to 1.5% of the amount of the epoxy resin monomer.

5. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method as claimed in claim 2, characterized in that: In step S1, the curing temperature is between room temperature and 200°C; And / or, in step S1, the curing time is ≥0.5h.

6. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S2, the halogenated alkane is selected from a combination of one or more of dichloromethane, dichloroethane, dichloropropane, trichloromethane and trichloroethane; And / or, in step S2, the aliphatic amine is selected from one or more combinations of ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, diethylaminopropylamine, bis(4-amino-3-methylcyclohexyl)methane or bis(4-aminocyclohexyl)methane.

7. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S2, the amount of cured epoxy resin used is ≥ 2 g; And / or, in step S2, the mass ratio of the cured epoxy resin to the dual solvent is 2-5:10-20.

8. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S2, the mass ratio of the halogenated alkane to the aliphatic amine is ≤1.

9. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S3, the temperature in the low temperature range is ≤150°C; and the reflux time is ≤70min.

10. The efficient method for pretreatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method according to claim 1, characterized in that: In step S3, after the first filtration, there is no filter residue or a certain amount of filter residue is obtained; when there is filter residue, the filter residue is undegraded solidified epoxy resin; And / or, a second filtrate is obtained after the second suction filtration, and the second filtrate is distilled to recover the main solvent component.

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