Efficient method for pretreating, degrading and recycling thermosetting epoxy resin based on mixed reaction type solvothermal method

Abstract

The invention provides an efficient method for pretreating, degrading and recycling thermosetting epoxy resin based on a mixed reaction type solvothermal method. The efficient method comprises the following steps: S1, providing cured epoxy resin; s2, adding the cured epoxy resin into double solvents for pre-soaking so as to provide a pre-treated sample; the double solvent is selected from halogenated alkane and aliphatic amine; and S3, carrying out reflux on the pretreated sample in a low-temperature interval, cooling to room temperature, carrying out first suction filtration to obtain a first filtrate, mixing the first filtrate with water to separate out a precipitate or form a dispersion liquid, carrying out second suction filtration on the precipitate, further separating the dispersion liquid, and recovering to obtain the epoxy resin degradation micromolecules or oligomers. According to the present invention, the halogenated alkane-aliphatic amine mixed reaction type double solvents with different proportions are subjected to pre-soaking and low-temperature interval reflux, and the obtained mixture and the original solvent molecule have the synergistic effect, such that the thermosetting epoxy resin can be efficiently degraded, the environmental protection is achieved, and the cost is low.

Description

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 resin has excellent physical and mechanical properties, electrical insulation properties, chemical corrosion resistance, heat resistance and bonding properties, and has been widely used in mechanical electronics, aerospace, transportation, construction, chemical and chemical industries and other industrial fields. The excellent performance of epoxy resins comes 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, the above-mentioned material performance characteristics also mean that it is difficult to degrade, resulting in great difficulties in the recycling and reuse of waste epoxy resins. The environmental pollution and waste of resources 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 recycling and reusing 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, and used as raw materials for the preparation of some specific products or low-value applications such as filling materials. Although this technical process is relatively mature, it is essentially just a "solid waste transfer" and has not fundamentally achieved the 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 causes new environmental problems. For example, Dow Global Technologies Co., Ltd. in the United States uses a mechanical method to convert waste resin into toughened 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 monomers or its low molecular polymers by heating or chemical reaction, thereby realizing complex component separation and recycling. However, the types of resins that can be treated by a specific solvent or medium are limited, and the amount of solvent used is large, and some solvents are only used as loosening agents and evaporate and lose, which is not only costly, but also creates new pressure on the environment; in addition, the dissolution rate is slow, the processable object is single (that is, only a certain type of epoxy resin can be processed), 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. Summary of the invention

[0006] In view of the shortcomings of the prior art mentioned above, the purpose of the present invention is to provide an efficient method for pretreatment, degradation and recovery of thermosetting epoxy resins based on a mixed reaction type solvent thermal method and a preparation method thereof, wherein the cured epoxy resins obtained under various standard curing conditions are subjected to pre-immersion and reflux in a low temperature range (e.g., ≤150°C) through a mixed reaction type double solvent, so as 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 and recycling of waste epoxy resins in the prior art.

[0007] To achieve the above objectives and other related objectives, the present invention is achieved through the following technical solutions.

[0008] On the one hand, 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:

[0009] S1: providing cured epoxy resin;

[0010] 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;

[0011] 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.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] In order to achieve low energy consumption, environmental protection and high efficiency of curing 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 thermosetting epoxy resin pretreatment degradation recovery of efficient method. Compared with the existing waste epoxy resin recovery and recycling mechanical method and solution method, the present invention adopts different proportions of halogenated alkane-aliphatic amine mixed reaction type double solvent under pre-immersion and low temperature range reflux (for example, ≤150°C), the resulting mixture and the original solvent molecules synergistically, not only can be degraded with high efficiency, but also green and environmentally friendly, low cost, can greatly promote the development of the recycling economy of waste epoxy resin. 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 applicability, and solves the singleness of the current degradation recovery epoxy resin technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1Shown are infrared spectra of dichloromethane, diethylenetriamine, and the heating reaction of dichloromethane and diethylenetriamine.

[0015] Figure 2 It is a schematic diagram showing the pretreatment and degradation results of the bisphenol A diglycidyl ether epoxy resin cured in Example 1 of the present invention.

[0016] Figure 3 Shown are 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 in Example 1 of the present invention.

[0017] Figure 4 Shown are thermogravimetric and heat flow curves of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin and recycled bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention.

[0018] Figure 5 Shown are differential scanning calorimetry curves of bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin and recycled bisphenol A diglycidyl ether epoxy resin according to Example 1 of the present invention.

[0019] Figure 6 The curing of bisphenol A diglycidyl ether epoxy resin and the recovered bisphenol A diglycidyl ether epoxy resin in Example 1 of the present invention are shown. 13 C-NMR spectrum.

[0020] Figure 7 Shown are the extracted ion chromatogram and base peak ion chromatogram at m / z 537.284 of bisphenol A diglycidyl ether epoxy resin recovered in negative ion mode in Example 1 of the present invention.

[0021] Figure 8 Shown is the infrared spectrum of diethylenetriamine in Example 1 of the present invention and the recovered diethylenetriamine.

[0022] Fig. 9 Shown are 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.

[0023] Fig.10 The 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 are shown.

[0024] Fig.11The curing of bisphenol F diglycidyl ether epoxy resin and the recycled bisphenol A diglycidyl ether epoxy resin according to Example 2 of the present invention are shown. 13 C-NMR spectrum.

[0025] Fig.12 Shown are infrared spectra of tri(4-hydroxyphenyl)methane triglycidyl ether, cured tri(4-hydroxyphenyl)methane triglycidyl ether epoxy resin, tri(4-hydroxyphenyl)methane triglycidyl ether epoxy resin degradation residue and recovered tri(4-hydroxyphenyl)methane triglycidyl ether epoxy resin of Example 3 of the present invention.

[0026] Fig.13 Shown is a schematic diagram of the pretreatment and degradation results of trimethylolpropane triglycidyl ether epoxy resin cured in Example 4.

[0027] Fig.14 The infrared spectrum of trimethylolpropane triglycidyl ether and trimethylolpropane triglycidyl ether epoxy resin cured with trimethylolpropane triglycidyl ether and acid anhydride in Example 4 is shown.

[0028] Fig.15 Shown is the infrared spectrum of tetrahydrophthalic acid diglycidyl ester and tetrahydrophthalic acid diglycidyl ester epoxy resin cured by acid anhydride in Example 5.

[0029] Fig.16 The infrared spectrum of diglycidyl tetrahydrophthalate and amine-cured diglycidyl tetrahydrophthalate epoxy resin in Example 6 is shown.

[0030] Fig.17 Commercial E51 (shown as cured Example 7 and Example 8) Fig.17 a) and E44( Fig.17 b) Schematic diagram of epoxy resin pretreatment and degradation results.

[0031] Fig.18 The bisphenol A diglycidyl ether epoxy resin cured in Comparative Examples 1 and 2 was cured using diethylenetriamine ( Fig.18 a) and dichloromethane alone ( Fig.18 b) Schematic diagram of pretreatment and degradation results. DETAILED DESCRIPTION

[0032] Hereinafter, the implementation method of the efficient method for pretreatment degradation and recovery of thermosetting epoxy resin based on mixed reaction type solvent thermal method of the present application is specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0033] The present invention aims at the problems existing in the current technical paths for recycling and reusing waste epoxy resins, and invents an efficient method for pre-treatment, degradation and recycling of thermosetting epoxy resins based on a mixed reaction type solvent thermal method. Specifically, through the reaction of different proportions of halogenated alkane-aliphatic amine mixed reaction type double solvents under pre-immersion and reflux in a low temperature range (for example, ≤150°C), the resulting mixture and the original solvent molecules can, under the synergistic effect, further increase the degradation or bond breaking selectivity and enhance the nucleophilicity, so as to achieve multi-selective and efficient degradation of the cured epoxy resin. On the other hand, the double solvent is fully utilized in this degradation process, and both are used as degradation reactants to avoid evaporation loss and waste. The main solvent components can also be greenly recycled 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 high-crosslinked cured epoxy resins. The epoxy resins studied are extensive and most commonly used, and the typical epoxy resins included are 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. The inventive method can achieve a degradation rate of the most common epoxy resin cured products above, up to approximately 100%. On this basis, this application is completed.

[0034] 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:

[0035] S1: providing cured epoxy resin;

[0036] 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;

[0037] 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. Mix the first filtrate with water to precipitate or form a dispersion, filter the precipitate for a second time, and further separate the dispersion to recover the epoxy resin degraded small molecules or oligomers.

[0038] In the efficient method for pretreatment, degradation and recycling of thermosetting epoxy resin provided by the present invention, step S1 is to provide a cured epoxy resin. In some embodiments, the preparation method of the cured epoxy resin includes: mixing and stirring an epoxy resin monomer and a curing agent, and obtaining a cured epoxy resin after curing at room temperature or heating; wherein the curing agent is selected from anhydride curing agents and / or amine curing agents. In a specific embodiment, a certain amount of epoxy resin monomer and curing agent are weighed in 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.

[0039] 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.

[0040] 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, benzophenonetetracarboxylic anhydride or trimellitic anhydride.

[0041] 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.

[0042] In step S1 of the present invention, in some embodiments, a phenolic accelerator may also be included, and the phenolic accelerator is also called 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, vacuumed to remove the internal air, and cured under certain curing conditions to obtain a cured epoxy resin.

[0043] 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.

[0044] In step S1 of the present invention, the amount of monomer is for the step of providing a cured product, and its amount can be increased as needed. In some embodiments, the amount of epoxy resin monomer is ≥ 20g. In a specific embodiment, the amount of epoxy resin monomer can also be, for example, 20-50g, 20-30g, 30-40g, or 40-50g.

[0045] 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.

[0046] 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.

[0047] In step S1 of the present invention, the stirring time is usually 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.

[0048] In step S1 of the present invention, the curing temperature may 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 the present application are room temperatures known in the art, for example, 20°C to 25°C.

[0049] 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.

[0050] In the efficient method for pretreatment, degradation and recycling of thermosetting epoxy resin provided by the present invention, step S2 is to add the cured epoxy resin into a double solvent for pre-soaking to provide a pre-treated sample. The double solvent is selected from halogenated alkanes and aliphatic amines. In a specific embodiment, a certain amount of cured epoxy resin is weighed in a round-bottom flask, and then the double solvent is added in a certain proportion, and the mixture is sealed in a cool and dry environment and stored for a period of time for pre-soaking.

[0051] In step S2 of the present invention, in some embodiments, the halogenated alkane is selected from a combination of one or more of dichloromethane, dichloroethane, dichloropropane, chloroform and trichloroethane.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] In step S2 of the present invention, in the dual solvent, the mass ratio of the halogenated alkane to the aliphatic amine is ≤1. Preferably, the mass ratio of the halogenated alkane to the aliphatic amine is 0.05 to 1. Optionally, 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 This is the infrared spectrum before and after the double solvent reaction.

[0056] In step S2 of the present invention, the pre-soaking time is usually not limited. In some embodiments, the pre-soaking time is, for example, ≥ 0.5 h.

[0057] 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, the thermosetting epoxy resin is efficiently degraded, cooled to room temperature, and a first filtrate is obtained after the first suction filtration, the first filtrate is mixed with water to precipitate or form a dispersion, the precipitate is subjected to a second suction filtration, and the dispersion is further separated and recovered to obtain epoxy resin degradation small molecules or oligomers. Among them, the epoxy resin degradation small molecules or oligomers are renewable.

[0058] In step S3 of the present invention, the temperature of the low temperature interval is ≤150° C. Preferably, the temperature of the low temperature interval is 100° C. to 150° C. Optionally, the temperature of the low temperature interval is, for example, 100° C. to 120° C., or 120° C. to 150° C.

[0059] In step S3 of the present invention, the reflux time is ≤70 minutes, preferably, the reflux time is 30 minutes to 70 minutes.

[0060] 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 obtain the recovered main solvent component. Among them, 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 2-8h.

[0061] In step S3 of the present invention, the epoxy resin degradation small molecules or oligomers are recovered after suction filtration, wherein the molecular weight of the epoxy resin degradation small molecules is ≤500, and the molecular weight of the oligomer is ≤1500.

[0062] The following is a description of the implementation of the present invention by means of specific embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0063] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

[0064] When the embodiments give 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 can 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 grasp of the prior art by those skilled in the art and the record 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 can also be used to realize the present invention.

[0065] Example 1

[0066] In this embodiment, a highly efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resin based on a mixed reaction type solvent thermal method is provided, and the steps are as follows:

[0067] S1: Weigh 20g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether of methyltetrahydrophthalic anhydride curing agent and 1% of the mass of bisphenol A diglycidyl ether of tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, cure at 120°C for 2h and at 150°C for 4h to obtain a cured bisphenol A diglycidyl ether epoxy resin.

[0068] 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 and dry environment for 48 hours for pre-soaking.

[0069] S3: The pretreated sample is refluxed at 130°C for 50 minutes, cooled to room temperature and filtered to obtain the undegraded epoxy resin residue, which is 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 is dropped into water and mixed with water to precipitate, and filtered to obtain the recovered epoxy resin, which is placed in a 60°C oven for drying and weighed to obtain 0.9551g of recovered bisphenol A diglycidyl ether epoxy resin; the filtrate is collected and distilled at a certain temperature (130°C) for a period of time (6h) under normal pressure to obtain recovered diethylenetriamine.

[0070] Depend on Figure 2 The schematic diagram shows that there is less residue after the bisphenol A diglycidyl ether epoxy resin is degraded by the mixed reaction type solvent thermal method, and the spectrum of the recovered bisphenol A diglycidyl ether epoxy resin is measured by infrared spectroscopy ( Figure 3 ), it can be seen from the figure that the main chain skeleton of bisphenol A diglycidyl ether epoxy resin is not destroyed after degradation, but at 1731cm -1 The C=O peak intensity of the ester group at the position decreased significantly, indicating that the ester bond of bisphenol A diglycidyl ether epoxy resin was cleaved. Figure 4 ) and the measured glass transition temperature ( Figure 5 ) It can be seen that the recycled bisphenol A diglycidyl ether epoxy resin is composed of small molecules or oligomers. The above conclusions are confirmed by elemental analysis (Table 1) and 13 C-NMR( Figure 6 ) was further confirmed. After degradation, there was no ester group at 173ppm. This shows that the degradation reaction of the mixed reaction type solvothermal method is mainly achieved by breaking the ester group. 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) showed a significant decrease in molecular weight, further indicating that the mixed reaction type solvent thermal method effectively degrades the polymer into small molecules or oligomers. The infrared spectrum of the recovered solvent was compared with the originally purchased diethylenetriamine ( Figure 8 ), it can be seen from the figure that the peak shapes are basically consistent, indicating that the recovered solvent is mainly composed of diethylenetriamine.

[0071] Table 1 Elemental analysis of Example 1 bisphenol A diglycidyl ether, cured bisphenol A diglycidyl ether epoxy resin and recovered bisphenol A diglycidyl ether epoxy resin

[0072]

[0073] Example 2

[0074] In this embodiment, an effective scheme for achieving efficient solvent thermal degradation and recovery of various epoxy resins cured by thermosetting anhydrides and amines based on dual solvent room temperature pretreatment is as follows:

[0075] S1: Weigh 20g of bisphenol F diglycidyl ether, 70% of the mass of bisphenol F diglycidyl ether of methyltetrahydrophthalic anhydride curing agent and 1% of the mass of bisphenol F diglycidyl ether of tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, cure at 120°C for 2h and at 150°C for 4h 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 and dry environment for 48 hours for pre-soaking.

[0077] S3: The pretreated sample is refluxed at 130°C for 50 minutes, cooled to room temperature and filtered to obtain the undegraded epoxy resin residue, which is 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 is dropped into water and mixed with water to precipitate, and filtered to obtain the recovered epoxy resin, which is placed in a 60°C oven for drying and weighed to obtain 1.0643g of recovered bisphenol F diglycidyl ether epoxy resin; the filtrate is collected and distilled at a certain temperature (130°C) for a period of time (6h) under normal pressure 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 ( Fig. 9), the main chain skeleton of bisphenol F diglycidyl ether epoxy resin was not destroyed after degradation, but at 1730cm -1 The C=O peak intensity of the ester group at the position of bisphenol F diglycidyl ether epoxy resin was significantly reduced, indicating that the ester bond of bisphenol F diglycidyl ether epoxy resin was cleaved. Fig.10 ) It can be seen that the recovered bisphenol F diglycidyl ether epoxy resin is composed of small molecules or oligomers. The above conclusion is 13 C-NMR( Fig.11 ) was further confirmed. After degradation, there was no ester group at 173 ppm. This shows that the degradation reaction of the mixed reaction type solvothermal method is mainly achieved by breaking the ester group.

[0079] Example 3

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

[0081] S1: Weigh 20g of tri(4-hydroxyphenyl)methane triglycidyl ether, 70% of the mass of tri(4-hydroxyphenyl)methane triglycidyl ether by methyltetrahydrophthalic anhydride curing agent and 1% of the mass of tri(4-hydroxyphenyl)methane triglycidyl ether by tri(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, cure at 120°C for 2h and at 150°C for 4h to obtain a cured tri(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 and dry environment for 48 hours for pre-soaking.

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

[0084] From the infrared spectrum of the recovered tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin, it can be seen that ( Fig.12 ), the main chain skeleton of tri(4-hydroxyphenyl)methane triglycidyl ether epoxy resin was not destroyed after degradation, but at 1728cm -1 The C=O peak intensity of the ester group at the position of 0 is significantly decreased, indicating that the ester bond of tris(4-hydroxyphenyl)methane triglycidyl ether epoxy resin is cleaved, indicating 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 by thermosetting anhydrides and amines based on dual solvent room temperature pretreatment is as follows:

[0087] S1: Weigh 20g 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, evacuate to remove the internal air, and cure at 120°C for 2h and at 150°C for 4h 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 and dry environment for 48 hours 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 nearly 100%.

[0090] Depend on Fig.13 The schematic diagram shows that the cured trimethylolpropane triglycidyl ether epoxy resin is substantially free of residue after being degraded by the mixed reaction type solvent thermal method. The spectrum of the cured trimethylolpropane triglycidyl ether epoxy resin was measured by infrared spectroscopy ( Fig.14 ), it can be seen from the figure that the cured trimethylolpropane triglycidyl ether epoxy resin is at 1729cm -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 by thermosetting anhydrides and amines based on dual solvent room temperature pretreatment is as follows:

[0093] S1: Weigh 20g 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, evacuate to remove the internal air, and cure at 120°C for 2h and at 150°C for 4h 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 and 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 nearly 100%.

[0096] The spectrum of cured tetrahydrophthalic acid diglycidyl ester epoxy resin was measured by infrared spectroscopy ( Fig.15 ), it can be seen from the figure that the cured tetrahydrophthalic acid diglycidyl ester epoxy resin is at 1726cm -1 The C=O peak intensity in the ester group at is higher, indicating that the cured diglycidyl tetrahydrophthalate 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 by thermosetting anhydrides and amines based on dual solvent room temperature pretreatment is as follows:

[0099] S1: Weigh 20g of diglycidyl tetrahydrophthalate and 12% of the mass of diethylenetriamine curing agent in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, gel at 25°C for 30min and cure at 120°C for 2h 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 and dry environment for 48 hours for pre-soaking.

[0101] S3: The pretreated sample was refluxed at 130°C for 50 minutes, then 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 ( Fig.16 ), it can be seen from the figure that the cured tetrahydrophthalic acid diglycidyl ester epoxy resin is at 1722cm -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 resin 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, evacuate to remove the internal air, and cure at 80°C for 2 h as recommended in the product instructions to obtain a cured commercial E51 epoxy resin.

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

[0107] S3: The pretreated sample was refluxed at 130°C for 50 min, then cooled to room temperature and filtered. The residue obtained after filtration 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 obtained, and the degradation rate was as high as 99.97% ( Fig.17 a).

[0108] Example 8

[0109] In this embodiment, a highly efficient method for pre-treatment, degradation and recovery of thermosetting epoxy resin 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, evacuate to remove the internal air, and cure at 80°C for 2 h as recommended in the product instructions to obtain a cured commercial E44 epoxy resin.

[0111] S2: Weigh 2 g of cured commercial E44 epoxy resin in a round-bottom flask, add 1 g of dichloromethane and 10 g of diethylenetriamine in a ratio of 1:10, and store in a sealed, cool and 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, and the residue obtained after filtration 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, and the degradation rate was as high as 99.99% ( Fig.17 b).

[0113] Comparative Example 1

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

[0115] S1: Weigh 20g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether of methyltetrahydrophthalic anhydride curing agent and 1% of the mass of bisphenol A diglycidyl ether of tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, cure at 120°C for 2h and at 150°C for 4h 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 in a cool and dry environment and stored for 48 h for pre-soaking.

[0117] S3: The pretreated sample was refluxed at 130°C for 50 min, then cooled to room temperature and filtered. The residue after filtration 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, which did not have a degradation effect ( Fig.18 a).

[0118] Comparative Example 2

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

[0120] S1: Weigh 20g of bisphenol A diglycidyl ether, 70% of the mass of bisphenol A diglycidyl ether of methyltetrahydrophthalic anhydride curing agent and 1% of the mass of bisphenol A diglycidyl ether of tris(dimethylaminomethyl)phenol accelerator in a beaker, stir for a while, pour into a mold, evacuate to remove the internal air, cure at 120°C for 2h and at 150°C for 4h 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 in a cool and dry environment and stored for 48 h for pre-soaking.

[0122] S3: The pretreated sample was refluxed at 130°C for 50 min, then cooled to room temperature and filtered. The residue after filtration 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, which did not have a degradation effect ( Fig.18 b).

[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 familiar with 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 a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still 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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