Green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin

Abstract

The invention discloses a green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin, and belongs to the field of degradation and recovery of traditional epoxy resin materials. The preparation method comprises the following steps: cutting the completely cured aromatic amine / glycidyl ether epoxy resin, putting the completely cured aromatic amine / glycidyl ether epoxy resin and a nitric acid solution into a closed hydrothermal reaction kettle, putting the reaction kettle into a drying oven, heating to a set temperature from room temperature, and preserving heat at the set temperature. By adopting the method, the epoxy resin can be highly degraded, no organic solvent or metal catalyst participates in the degradation method and system, and the temperature of the degradation process is far lower than the temperature of thermal cracking and supercritical degradation. Therefore, the degradation method disclosed by the invention has the characteristics of high efficiency, environmental protection and low energy consumption, and a feasible technical scheme is provided for degradation of the amine cured glycidyl ether epoxy resin.

Description

Technical Field

[0001] The invention belongs to the field of degradation and recycling of traditional epoxy resin materials, and particularly relates to a green and efficient degradation method for aromatic amine / glycidyl ether epoxy resins. Background Art

[0002] Epoxy resin, with its strong cohesive force, forms a compact molecular structure, resulting in exceptional mechanical properties that surpass those of other resins. It is widely used in numerous fields, including engineering, aerospace, and coatings, and holds a key position, playing an indispensable role in driving the rapid development of industrial technology.

[0003] After curing, epoxy resin forms a highly cross-linked three-dimensional network structure. While this network structure imparts outstanding properties such as heat resistance and high mechanical strength, it also contributes to its insoluble and infusible properties. This makes it difficult to degrade naturally, leading to a large amount of waste becoming municipal waste. Although research on intrinsically degradable epoxy resins has flourished in recent years, they lack cost advantages and remain deficient in balancing performance and degradability. Completely replacing traditional epoxy resins with degradable epoxy resins remains unrealistic. Furthermore, the majority of epoxy resins consumed and discarded in the market are still non-degradable traditional epoxy resins such as glycidyl ethers and glycidyl esters. Therefore, realistically speaking, research on the degradation of general-purpose epoxy resins remains a crucial topic.

[0004] Although literature reports that complete degradation of epoxy resin can be achieved through high-temperature cracking and supercritical fluid technology, the thermal cracking method requires high temperature and is prone to leakage, fire, carbon deposition, low thermal efficiency, and short equipment life. The supercritical fluid method requires high-pressure equipment and requires large equipment investment.

[0005] The Chinese patent document "Epoxy Resin Degradation Method, Epoxy Resin Degradation Solvent System, and Recovery Method" (Publication No.: CN114479177B) discloses a solvent system for epoxy resin degradation, comprising 30%-70% by weight of N,N-dimethylformamide (DMF) and 30%-70% by weight of ethylene glycol (EG). Heating this solvent system to 120-150°C solves the degradation and recovery issues of anhydride-cured bisphenol A diglycidyl ether epoxy resin, avoiding the soil contamination associated with traditional landfill methods. However, this method involves an organic solvent system, and the solvent recovery process increases the technical complexity and cost of the recovery process.

[0006] A Chinese patent application, "A Method for Recycling Epoxy Resin-Based Materials" (Publication No. CN103627026A), discloses a method for recycling epoxy resin-based materials. This method utilizes high-temperature steam to thermally crack the epoxy resin-based materials. The addition of an appropriate alkaline compound catalyst promotes the cracking process, resulting in a thermal cracking product. This method overcomes the shortcomings of solvent decomposition, such as environmental pollution and expensive solvents. However, it requires the introduction of steam at 150-600°C into the reactor, placing high demands on equipment and consuming high temperatures.

[0007] In view of the above-mentioned shortcomings, the present invention proposes a hydrothermal reaction process for aromatic amine / glycidyl ether epoxy resin without organic solvent and catalyst system, which realizes green, efficient and low-energy degradation of epoxy resin.

[0008] The disclosure of the above background technology content is only used to assist in understanding the inventive concept and technical solution of the present invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above content has been disclosed on the filing date of this patent application, the above background technology should not be used to evaluate the novelty and creativity of this application. Summary of the Invention

[0009] The present invention provides an environmentally friendly and efficient degradation method for aromatic amine / glycidyl ether epoxy resins. By employing a hydrothermal degradation method without an organic solvent or catalyst system, the present invention addresses the difficulties associated with degradation of aromatic amine / glycidyl ether epoxy resins, including low degradation efficiency, secondary pollution, and high costs. This provides a reliable technical route for the degradation and recovery of general-purpose epoxy resins.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0011] A green and efficient degradation method for aromatic amine / glycidyl ether epoxy resin comprises the following steps:

[0012] (1) taking a fully cured aromatic amine / glycidyl ether epoxy resin, placing it and a nitric acid solution into a hydrothermal reactor, placing the reactor in an oven, heating it from room temperature to a set temperature, and keeping it at the set temperature to hydrothermally degrade the epoxy resin;

[0013] (2) After the hydrothermal degradation is completed, the hydrothermal kettle is cooled to room temperature, the mixture in the kettle is poured out, filtered, and the filter residue and filtrate are collected separately; the filter residue is washed, dried, collected, and weighed, and the degradation rate is calculated; the filtrate is subjected to extraction treatment, and the upper organic layer is taken and rotary evaporated to obtain the liquid product, which is placed in a vacuum drying oven for drying and structural characterization is performed to confirm the components of the degradation product.

[0014] Furthermore, the mass of the fully cured aromatic amine / glycidyl ether epoxy resin described in step (1) is 0.1 g.

[0015] Furthermore, the amine curing agent in step (1) includes one or more of diaminodiphenyl sulfone (DDS) or diaminodiphenylmethane (DDM).

[0016] Furthermore, the aromatic amine / glycidyl ether epoxy resin in step (1) includes one or more of bisphenol A epoxy resin and bisphenol F epoxy resin.

[0017] Furthermore, the concentration of the nitric acid solution in step (1) is 2-3 mol / L.

[0018] Furthermore, the amount of the nitric acid solution is 12-15 mL.

[0019] Furthermore, the set temperature in step (1) is 130-150°C.

[0020] Furthermore, the holding time in step (1) is 7-9 hours.

[0021] Furthermore, the filtrate in step (2) is extracted with ethyl acetate.

[0022] Furthermore, the degradation product components described in step (2) are mainly organic chemical intermediates of trinitrophenol and N,N-dimethylformamide.

[0023] Technical principle of the present invention:

[0024] The role of the hydrothermal environment: Under hydrothermal conditions, the physical and chemical properties of water undergo significant changes. The dielectric constant of water decreases, and its ionic product increases, enhancing its solubility for ionic compounds and increasing its affinity for organic matter. This unique water environment promotes the diffusion and uniform distribution of nitric acid throughout the system, increasing the contact between nitric acid and epoxy resin molecular chains and creating favorable conditions for the degradation reaction. Furthermore, the energy provided by high temperature and high pressure breaks the chemical bonds in the epoxy resin's crosslinked network, reducing the activation energy of the reaction and accelerating the degradation reaction.

[0025] The dual action mechanism of nitric acid: Nitric acid plays a dual role of strong oxidizing and acidic properties in the degradation process. From the perspective of oxidation, nitric acid can oxidatively break CC bonds, CO bonds, etc. in the epoxy resin molecular chain, and gradually decompose the macromolecular chain into small molecular fragments. Its oxidation preferentially occurs in the parts with high electron cloud density and relatively weak chemical bonds, resulting in the gradual disintegration of the cross-linked network. From the perspective of acidity, the H +It catalyzes the hydrolysis of ether bonds and carbon-nitrogen bonds in the epoxy resin molecular chain. This hydrolysis breaks the molecular chain, generating small molecules such as alcohols and amines, which further promote the degradation of the epoxy resin. These two effects work synergistically and mutually promote each other, achieving efficient degradation of the epoxy resin.

[0026] Advantages of organic solvent-free and catalyst-free systems: Traditional epoxy resin degradation methods often use organic solvents and catalysts. Organic solvents have safety hazards such as volatile pollution, flammability and explosiveness, which increase the difficulty and cost of subsequent product separation and treatment; catalysts may introduce impurities, affecting the purity and recycling value of the degradation products. This method abandons organic solvents and catalysts, uses water as the medium and nitric acid as the reactant, and simplifies the reaction system. Water, as a green and environmentally friendly solvent, is widely available, low-cost, and does not produce secondary pollution; nitric acid acts as both an oxidant and a catalyst in the reaction process, initiating and accelerating the degradation reaction through its own chemical properties. There is no need to add additional catalysts, which reduces costs and improves the economy and environmental friendliness of the method. At the same time, the organic solvent-free system makes the product separation process simpler, reduces the separation steps and energy consumption, and further improves the efficiency and feasibility of the entire degradation and recovery process.

[0027] Compared with the existing technology, the present invention has shown significant progress and unique advantages, which are specifically reflected in the following two aspects:

[0028] (1) The present invention utilizes hydrothermal reaction conditions to achieve efficient degradation of the target epoxy resin. The degradation reaction operation and post-processing are simple, and the degradation efficiency is high, reaching a degradation rate of up to 100%. Characterization confirms that the degradation products are primarily organic chemical intermediates such as trinitrophenol and N,N-dimethylformamide. Compared to high-temperature thermal cracking and supercritical processes, the present invention has the advantages of low energy consumption and small equipment investment.

[0029] (2) The present invention avoids the use of large amounts of toxic and volatile organic compounds or toxic catalysts, and only uses a relatively low concentration of 2-3 mol / L nitric acid aqueous solution as the solvent system, which simplifies post-processing and reduces pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of the structure of the aromatic amine / glycidyl ether epoxy resins mainly involved;

[0031] Figure 2 DSC curves of DDS-cured bisphenol A epoxy resin (E51) and DDM-cured bisphenol A epoxy resin (E51) specimens;

[0032] Figure 3 The infrared curves of DDS, bisphenol A epoxy resin (E51) and DDS-cured bisphenol A epoxy resin (E51) after degradation;

[0033] Figure 4 The infrared curves of DDM, bisphenol A epoxy resin (E51) and DDM-cured bisphenol A epoxy resin (E51) specimens after degradation;

[0034] Figure 5 The degradation of DDS-cured bisphenol A epoxy resin (E51) under different conditions;

[0035] Figure 6 The figure is a bar graph showing the degradation rate of bisphenol A epoxy resin (E51) or bisphenol F epoxy resin cured by DDS or DDM under different conditions;

[0036] Figure 7 The structural formula and degradation of diaminodiphenylmethane (DDS) / bisphenol A epoxy resin. DETAILED DESCRIPTION

[0037] The present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be emphasized that the following description is merely illustrative and is not intended to limit the scope of the present invention and its application. The advantages and all changes that can be thought of by relevant technical personnel in the field are included in the present invention, and the present invention covers all modifications, substitutions, equivalent methods and schemes made within the concept and scope of the present invention as defined by the claims. The preparation process, reaction conditions, reagents, experimental methods, etc. for implementing the present invention, except for the contents specifically involved below, are all common knowledge and common sense in the art, and the present invention has no specific limiting contents. In order for the public to better understand the present invention, some specific details are described in detail here. For those skilled in the art, the present invention can be fully understood without these details.

[0038] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein like reference numerals refer to like parts unless otherwise specifically specified.

[0039] Example 1

[0040] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / E51-1. A 0.1 g sample of DDS / E51-1 was placed in a sealed hydrothermal reactor with 15 ml of 2 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the mixture was maintained at this temperature for 9 h for hydrothermal degradation.

[0041] Example 2

[0042] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / E51-2. A 0.1 g sample of DDS / E51-2 was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the mixture was maintained at this temperature for 9 h for hydrothermal degradation.

[0043] Example 3

[0044] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / E51-3. A 0.1 g sample of DDS / E51-3 was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 130°C. After reaching the set temperature, the mixture was maintained at this temperature for 9 h for hydrothermal degradation.

[0045] Example 4

[0046] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / E51-4. A 0.1 g sample of DDS / E51-4 was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the mixture was maintained at this temperature for 7 h for hydrothermal degradation.

[0047] Example 5

[0048] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / E51-5. A 0.1 g sample of DDS / E51-5 was placed in a sealed hydrothermal reactor with 12 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the mixture was maintained at this temperature for 9 h for hydrothermal degradation.

[0049] Example 6

[0050] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenylmethane (DDM) and bisphenol A epoxy resin (E51, epoxy value 0.48-0.54 ep / 100 g) through programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenylmethane / bisphenol A epoxy resin. This cured resin was designated DDM / E51. A 0.1 g DDM / E51 strip was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the hydrothermal degradation reaction was carried out by maintaining the temperature for 9 h.

[0051] Example 7

[0052] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenyl sulfone (DDS) and bisphenol F epoxy resin (E51, epoxy value 0.51–0.56 eq / 100 g) via programmed temperature ramping (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenyl sulfone / bisphenol A epoxy resin. This cured resin was designated DDS / F. A 0.1 g DDS / F strip was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the resin was maintained at this temperature for 9 h for hydrothermal degradation.

[0053] Example 8

[0054] A cured epoxy resin was prepared by melt blending, casting, and reacting diaminodiphenylmethane (DDM) and bisphenol F epoxy resin (E51, epoxy value 0.51–0.56 eq / 100 g) through a temperature-programmed reaction (80°C for 2 h, 150°C for 4 h, and 180°C for 1 h). Differential scanning calorimetry (DSC) analysis revealed a curing endotherm, indicating complete curing of the diaminodiphenylmethane / bisphenol F epoxy resin. This cured resin was designated DDM / F. A 0.1 g DDM / F strip was placed in a sealed hydrothermal reactor with 15 ml of 3 mol / L aqueous nitric acid. The reactor was then transferred to an oven and heated from room temperature to 150°C. After reaching the set temperature, the resin was maintained at this temperature for 9 h for hydrothermal degradation.

[0055] The degradation rates of the epoxy resins obtained in Examples 1-8 were tested, and the results are shown in Table 1.

[0056] Table 1 Degradation rates under different parameters of Examples 1-8

[0057]

[0058]

[0059] As shown in Table 1, Examples 1-5 demonstrate that the degradation of bisphenol A epoxy resin (E51) cross-linked with diaminodiphenyl sulfone (DDS) using a 3 mol / L, 15 ml nitric acid solution in a hydrothermal reactor at 150°C for 9 hours yields the best degradation rate, reaching 100%. Examples 1 and 2 are concentration-controlled experiments; Examples 3 and 2 are temperature-controlled experiments; Examples 4 and 2 are time-controlled experiments; and Examples 5 and 2 are nitric acid dosage-controlled experiments. Examples 6-8 are experiments comparing bisphenol A epoxy resin (E51) cross-linked with diaminodiphenylmethane (DDM) and bisphenol F epoxy resin cross-linked with diaminodiphenyl sulfone (DDS) or diaminodiphenylmethane (DDM). Using a 3 mol / L, 15 ml nitric acid solution in a hydrothermal reactor at 150°C for 9 hours, the degradation rates all reached 100%.

[0060] See Figure 1 , according to the literature data, the structures of fully cured aromatic amine / glycidyl ether epoxy resins prepared in-house: diaminodiphenyl sulfone (DDS) cross-linked bisphenol A epoxy resin, diaminodiphenylmethane (DDM) cross-linked bisphenol A epoxy resin, diaminodiphenyl sulfone (DDS) cross-linked bisphenol F epoxy resin, and diaminodiphenylmethane (DDM) cross-linked bisphenol F epoxy resin.

[0061] See Figure 2 It can be seen that the DDS-cured bisphenol A epoxy resin (E51) and the DDM-cured bisphenol A epoxy resin (E51) prepared according to the literature have been completely cured.

[0062] See Figure 3 It can be seen that the degraded DDS-cured bisphenol A epoxy resin (E51) specimen has a characteristic peak of ether bond at 1035 cm -1 The characteristic peak of sulfone group of DDS is 1145cm -1 The intensity is obviously weakened, and the extra 1530cm -1 and 1350cm -1 Two characteristic peaks of Ar-NO2 nitro group.

[0063] See Figure 4 It can be seen that the degraded DDM-cured bisphenol A epoxy resin (E51) specimen has a peak at 1035 cm -1 The characteristic peak of ether bond in E51 disappears; 2900cm -1 and 2825cm -1 The methylene peak in DDM disappears, and an additional peak at 1530 cm -1 and 1350cm -1 Two characteristic peaks of Ar-NO2 nitro group.

[0064] See Figure 5 The degradation of DDS-cured bisphenol A epoxy resin (E51) under different conditions can be intuitively seen. Among them, the degradation effect of DDS / E51-2 using 3 mol / L, 15 ml nitric acid aqueous solution in a hydrothermal reactor at 150°C for 9 hours was the best, reaching 100%.

[0065] See Figure 6 , it can be seen that the degradation rate bar graph of DDS or DDM cured bisphenol A epoxy resin (E51) or bisphenol F epoxy resin under different conditions.

[0066] See Figure 7 , which is the structural formula, degradation diagram and main degradation products of diaminodiphenylmethane (DDS) / bisphenol A type epoxy resin.

[0067] The above content is a further detailed description of the present invention in conjunction with specific implementation methods, and the specific implementation of the present invention should not be considered to be limited to these descriptions. For those skilled in the art of the present invention, they can make several substitutions or modifications to the described embodiments without departing from the concept of the present invention, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention.

Claims

1. A green and efficient degradation method for aromatic amine / glycidyl ether epoxy resin, characterized in that: The following steps are involved: (1) taking a fully cured aromatic amine / glycidyl ether epoxy resin, placing it and a nitric acid solution into a hydrothermal reactor, placing the reactor in an oven, heating it from room temperature to a set temperature, and keeping it at the set temperature to hydrothermally degrade the epoxy resin; (2) After the hydrothermal degradation is completed, the hydrothermal kettle is cooled to room temperature, the mixture in the kettle is poured out, filtered, and the filter residue and filtrate are collected separately; the filter residue is washed, dried, collected, and weighed, and the degradation rate is calculated; the filtrate is subjected to extraction treatment, and the upper organic layer is taken and rotary evaporated to obtain the liquid product, which is placed in a vacuum drying oven for drying and structural characterization is performed to confirm the components of the degradation product.

2. The green and efficient degradation method of an aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The mass of the fully cured aromatic amine / glycidyl ether epoxy resin described in step (1) is 0.1 g.

3. The green and efficient degradation method of an aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The amine curing agent described in step (1) includes one or more of diaminodiphenyl sulfone or diaminodiphenylmethane.

4. The green and efficient degradation method of an aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The aromatic amine / glycidyl ether epoxy resin described in step (1) includes one or more of bisphenol A epoxy resin and bisphenol F epoxy resin.

5. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The concentration of the nitric acid solution described in step (1) is 2-3 mol / L.

6. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 5, characterized in that: The amount of the nitric acid solution is 12-15 mL.

7. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The set temperature in step (1) is 130-150°C.

8. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The holding time in step (1) is 7-9 hours.

9. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The filtrate in step (2) is extracted with ethyl acetate.

10. The green and efficient degradation method of aromatic amine / glycidyl ether epoxy resin according to claim 1, characterized in that: The degradation product components described in step (2) include trinitrophenol and organic chemical intermediates of N,N-dimethylformamide.

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