A method for recovering bisphenol a from epoxy resin degradation products

Abstract

The present application belongs to the technical field of polymer material recycling and resource utilization, and particularly relates to a method for recovering bisphenol A from epoxy resin degradation products. The present application mainly solves the problems of low catalyst efficiency, difficulty in separating and recycling the degradation product epoxy oligomer in the current epoxy resin acidolysis technology, and the problems of complicated process, high energy consumption, unsatisfactory yield of degradation product bisphenol A, and inability to handle glass fiber reinforced epoxy resin based composites due to alkali corrosion in the alkaliolysis technology. In the present application, the bisphenol A type epoxy resin waste is degraded into epoxy oligomer by a chemical recovery method; then the epoxy oligomer is mixed with an inorganic alkali catalyst, a cocatalyst, a solvent and a nitrate salt in a certain proportion to react, and bisphenol A is obtained after separation and purification after the reaction is completed. The present application has the advantages of high catalyst efficiency, mild reaction conditions, simple and efficient process, easy separation of product, high yield, significant economic benefit, and wide application range.

Description

Technical Field

[0001] This invention belongs to the field of polymer material recycling and resource utilization technology, specifically relating to a method for recovering bisphenol A from epoxy resin degradation products. Background Technology

[0002] Epoxy resin (EP), as an important thermosetting resin, is widely used in coatings, electronic packaging, aerospace, and wind turbine blades due to its excellent mechanical properties, adhesion, chemical stability, and electrical insulation. Among them, bisphenol A (BPA) type epoxy resins synthesized from BPA and carbon fiber / glass fiber reinforced composites (CFRP / GFRP) based on BPA dominate the global epoxy resin market due to their outstanding comprehensive performance. However, the large-scale production, use, and disposal of these materials have generated a large amount of waste epoxy resin and its composites. These materials, due to their high crosslinking density and strong chemical stability, are extremely difficult to degrade naturally, especially CFRP / GFRP, which not only causes serious resource waste but also brings significant environmental pressure. Therefore, how to achieve efficient and high-value chemical recycling and resource recycling has become a major challenge for the circular economy and sustainable development of polymer materials.

[0003] Currently, the resource recovery of waste epoxy resins and their composites mainly relies on chemical recycling. This involves completely or incompletely breaking the cross-linked C-C bonds in the resin, converting it into small-molecule chemicals or oligomers. BPA, as an important chemical raw material, is considered one of the most economically viable resource recovery pathways due to its efficient recycling. Industrially, BPA primarily originates from non-renewable petrochemical resources. Besides its use in epoxy resin synthesis, it is widely applied in the production of various polymers such as polycarbonate, phenolic resin, and unsaturated polyester resin. It is also a key intermediate in the preparation of fine chemicals such as flame retardants, plasticizers, and antioxidants, holding an irreplaceable position in the electronics, automotive, and medical device industries. The chemical recycling of epoxy resins and their composites mainly depends on acid hydrolysis and alkaline hydrolysis technologies, both of which have significant limitations. In the acid hydrolysis pathway, Lewis acids or Brønsted acids are often used as catalysts to selectively break the C-C bonds in the resin network under mild conditions. However, limited by catalyst efficiency, the degradation products are mainly complex epoxy oligomers that are difficult to separate and purify, resulting in low reuse value and economic viability. In the alkaline hydrolysis pathway, inorganic or organic strong bases are typically used to completely degrade the resin under harsh conditions such as high temperature and pressure, aiming to directly recover BPA. However, this process easily leads to further decomposition of BPA into byproducts such as phenol and p-isopropylphenol, resulting in unsatisfactory yields of the target product. Crucially, the strong alkaline medium severely corrodes reinforcements such as glass fibers, making this technology unsuitable for the large stock of GFRP and greatly limiting its industrial application. Furthermore, the products of other chemical recovery methods such as hydrolysis and oxidative degradation are still mainly epoxy oligomers, and efficient processes for the targeted conversion of these oligomers into BPA have not yet been developed.

[0004] Therefore, developing a novel and efficient chemical recycling method that overcomes the shortcomings of existing acidolysis and alkaline hydrolysis technologies is crucial. This method aims to first efficiently and selectively convert epoxy resins and their composites into epoxy oligomers under relatively mild conditions, and then, through appropriate technical means, further efficiently and in high yield convert the oligomers into easily separable high-value chemical BPA. This pathway has significant scientific and engineering implications for achieving closed-loop recycling of thermosetting polymers. Summary of the Invention

[0005] To address the problems of low catalyst efficiency and difficult-to-separate, high-value epoxy oligomers in existing acid hydrolysis technologies, and the easy decomposition of BPA into byproducts, unsatisfactory yield, and inapplicability to the large stock of GFRP in alkaline hydrolysis technologies, this invention provides a method for first depolymerizing epoxy resin and its composites into epoxy oligomers, and then further converting them into high-yield BPA. This method can overcome the defects of the aforementioned acid hydrolysis and alkaline hydrolysis technologies, and has significant economic benefits.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for recovering bisphenol A from epoxy resin degradation products, characterized by the following steps: Step 1, degrading bisphenol A type epoxy resin waste through chemical recovery to obtain epoxy resin degradation products - epoxy oligomers; Step 2, mixing epoxy oligomers, inorganic base catalysts, co-catalysts, solvents and nitrates in a certain proportion for reaction, and separating and purifying the products after the reaction to obtain bisphenol A.

[0008] Currently, the chemical recycling of waste epoxy resins and their composites mainly relies on acid hydrolysis and alkaline hydrolysis, but both have significant limitations. Acid hydrolysis, using Lewis or Brønsted acids as catalysts, offers mild reaction conditions, but insufficient catalyst efficiency results in degradation products that are mostly complex, difficult-to-separate, low-value-added epoxy oligomers, leading to poor economic viability. Alkaline hydrolysis requires harsh conditions such as high temperature and pressure to achieve complete resin degradation with the help of strong alkalis, which not only easily causes further decomposition of the target product BPA, resulting in unsatisfactory yields, but also severely corrodes glass fibers, making it unsuitable for the large quantities of GFRP and greatly limiting its industrial applications. BPA, as an important chemical raw material, is widely used in the synthesis of epoxy resins, polycarbonates, and other polymer materials and various fine chemicals, holding an irreplaceable position in many fields. Its efficient recycling is the most economical resource recovery path in the chemical recycling of epoxy resins. Furthermore, other methods such as hydrolysis and oxidative degradation still mainly produce oligomers, and efficient processes for their targeted conversion into BPA have not yet been mastered, further highlighting the need for the development of new recycling technologies. Based on this, the present invention proposes a stepwise conversion strategy: first, under mild conditions, waste epoxy resin and its composites are selectively converted into epoxy oligomers; then, by constructing a high-performance reaction system, the epoxy oligomers are further efficiently converted into easily separable high-value chemical BPA. This method can simultaneously overcome the shortcomings of the aforementioned acid hydrolysis and alkaline hydrolysis technologies, and has both good economic efficiency and applicability.

[0009] Furthermore, the bisphenol A type epoxy resin waste in step 1 includes pure epoxy resin and carbon fiber or glass fiber reinforced composite materials based thereon. Bisphenol A type epoxy resin and carbon fiber / glass fiber reinforced composite materials based thereon dominate the global epoxy resin market, with a market share exceeding 90%.

[0010] Furthermore, the chemical recovery method in step 1 includes hydrolysis, alcoholysis, aminolysis, acetylation, oxidative degradation, supercritical / subcritical fluid degradation, Lewis acid catalytic degradation, oxidation / acid hydrolysis, oxidation / alkali hydrolysis, or pyrolysis. This chemical recovery method efficiently converts epoxy resin into epoxy oligomers that retain the basic bisphenol A skeleton by selectively breaking the CN / COC bonds in the epoxy resin. This process not only avoids raw material waste and secondary pollution, realizing the recycling of solid waste, but also lays the foundation for the subsequent high-value utilization of the product.

[0011] Furthermore, in step 1, the reaction temperature is 60–300℃ and the reaction time is 0.5–24 h; in step 2, the reaction temperature is 80–160℃ and the reaction time is 0.5–12 h. Within this reaction temperature and time range, the efficient conversion of bisphenol A type epoxy resin waste into epoxy oligomers and epoxy oligomers into BPA can be achieved. This avoids incomplete reactions due to insufficient conditions and prevents side reactions and BPA decomposition caused by excessive conditions.

[0012] Furthermore, the structure of the epoxy oligomer in step 1 is as follows: ;where R 1 and R 2 Each independently is an alkyl group, , , , , , , , , , , , , , , Or H. The high proportion of BPA structure in this epoxy oligomer provides the most economical path to achieve its low-cost conversion into high-value BPA.

[0013] Furthermore, in step 2, the inorganic base catalyst is one or a mixture of several of the following: hydroxides, amino compounds, imino compounds, metal alkyl / aryl compounds, metal oxides, quaternary ammonium bases, alkoxides, carbonates, bicarbonates, phosphates, silicates, acetates, and borates. These inorganic base catalysts can efficiently break the COC bonds in epoxy oligomers, thereby converting low-value epoxy oligomers into structurally well-defined and easily separable BPA.

[0014] Furthermore, in step 2, the co-catalyst is one or a mixture of several of the following: sodium phenolate, potassium phenolate, sodium o-cresol, potassium o-cresol, sodium o-phenylphenolate, sodium p-chlorophenolate, sodium o-nitrophenolate, sodium catechol, and sodium α-naphthol. The introduction of the co-catalyst can significantly accelerate the degradation reaction without affecting the structural integrity and yield of BPA, enabling it to be completed in a short time.

[0015] Furthermore, in step 2, the solvent is one or a mixture of several hydrocarbons, amides, ethers, or alcohols in any proportion. This solvent not only allows the reaction to proceed under mild conditions but also avoids the problem of bisphenol A disodium salt, a degradation product, generating quinone byproducts due to air oxidation, which is present in existing alkaline hydrolysis processes. It eliminates the need for inert gas protection, simplifying the process and achieving efficient preservation of the BPA structure.

[0016] Furthermore, in step 2, the nitrate is one or a mixture of several of the following in any proportion: ammonium nitrate, potassium nitrate, strontium nitrate, barium nitrate, copper nitrate, silver nitrate, ferric nitrate, nickel nitrate, calcium nitrate, sodium nitrate, magnesium nitrate, aluminum nitrate, zinc nitrate, chromium nitrate, and cerium ammonium nitrate. The introduction of the nitrate can significantly accelerate the reaction rate and shorten the reaction time without affecting the structural integrity and yield of BPA.

[0017] Furthermore, in step 2, the mass ratio of epoxy oligomer, inorganic base catalyst, co-catalyst, solvent, and nitrate is 1:1–4:0.03–0.3:3–8:0–0.4. Within this ratio range, the epoxy resin degradation product—epoxy oligomer—can efficiently generate BPA with minimal side reactions and easy product separation, achieving optimal overall benefits.

[0018] Furthermore, the separation and purification in step 2 includes: acidifying the reaction solution and filtering it, then washing and drying the resulting solid to obtain bisphenol A.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) The stepwise conversion strategy proposed in this invention has milder reaction conditions and lower energy consumption. It can not only effectively avoid the decomposition of BPA under harsh conditions and the occurrence of side reactions, but also significantly increase the reaction rate due to the significant decrease in crosslinking density of epoxy oligomers, resulting in significant economic benefits.

[0021] (2) The step-by-step conversion strategy proposed in this invention realizes the high-value recycling of epoxy resin degradation products. The obtained BPA can be used as a recycled raw material to be put back into production, which significantly reduces the dependence of the polymer materials and fine chemicals fields on petrochemical-derived native BPA and forms a closed loop of "material-raw material-material".

[0022] (3) The present invention can efficiently convert epoxy oligomers obtained by various chemical recycling methods, and has high versatility and raw material adaptability.

[0023] (4) The inorganic base catalyst, co-catalyst, solvent and nitrate used in this invention are all commercially available and some can be recycled. The process is economical and environmentally friendly, and does not damage the mechanical properties of the recycled fibers. The fibers can be directly reused. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a digital photograph of the carbon fiber recovered in Example 1.

[0026] Figure 2 This is a SEM image of the carbon fiber recovered in Example 1.

[0027] Figure 3 This is a digital photograph of the epoxy oligomer obtained from the chemical recycling and degradation of bisphenol A type epoxy resin waste in Example 1.

[0028] Figure 4 This is a digital photograph of bisphenol A, the product obtained after reaction and separation of the epoxy oligomer in Example 1.

[0029] Figure 5 The product (a) obtained after acidification and solvent removal of the reaction solution following the epoxy oligomer reaction in Example 1, and the bisphenol A standard (b) are compared. 1 H NMR spectrum.

[0030] Figure 6 The product (a) obtained after reaction and separation of the epoxy oligomer in Example 1 and the bisphenol A standard (b) 1 H NMR spectrum.

[0031] Figure 7 The product (a) obtained after reaction and separation of the epoxy oligomer in Example 1 and the bisphenol A standard (b) 13 C10 NMR spectrum.

[0032] Figure 8 This is a digital photograph of the glass fiber recovered in Example 2.

[0033] Figure 9 This is an SEM image of the glass fiber recovered in Example 2. Detailed Implementation

[0034] To gain a deeper understanding of this invention, we will provide a comprehensive and detailed description. However, this invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a full understanding of the disclosure of this invention.

[0035] Example 1

[0036] Carbon fiber reinforced epoxy resin composite material was placed in a dodecylbenzene sulfonic acid aqueous solution and subjected to hydrolysis at 190℃ for 24 h. After the reaction, epoxy oligomers and carbon fibers were separated. Figure 1-3 Subsequently, 4.0 g of sodium carbonate, 0.15 g of sodium phenolate, 5.0 g of N,N-dimethylformamide, and 0.12 g of potassium nitrate were sequentially added to the reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomer was added, and the reaction was carried out at 120 °C for 4 h. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The obtained solid was washed with water and dried to obtain bisphenol A. The characterization results of the product are as follows: Figure 4-7 As shown. Among them, Figure 4 A digital photograph of the product. Figure 5 of 1 ¹H NMR spectroscopy confirmed that the product was bisphenol A, and no decomposition products (such as phenol, p-isopropylphenol, etc.) were detected. The product (a) obtained after reaction and separation of the epoxy oligomer and the bisphenol A standard (b) were compared. 1 H NMR spectrum ( Figure 6 )and 13 C NMR spectrum ( Figure 7 The results showed a high degree of agreement, further confirming that the product was bisphenol A. The above spectral results demonstrate that this method successfully achieved the complete conversion of epoxy oligomers to bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 92%.

[0037] Example 2

[0038] Glass fiber reinforced epoxy resin composite material was placed in nitric acid solution and subjected to oxidative degradation reaction at 90℃ for 6 hours. After the reaction, epoxy oligomers and glass fibers were separated. Figure 8-9 Subsequently, 2.0 g of zinc oxide, 0.03 g of potassium o-cresol, 5.0 g of ethanol, and 0.2 g of ammonium nitrate were sequentially added to the reactor and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomer was added, and the reaction was carried out at 100 °C for 6 h. After the reaction was completed, the reactor was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomer was completely converted, and the yield of bisphenol A was 90%.

[0039] Example 3

[0040] Carbon fiber reinforced epoxy resin composite material was placed in n-propanol and subjected to supercritical fluid degradation at 300℃ for 0.5 h. After the reaction, epoxy oligomers and carbon fibers were separated. Subsequently, 2.5 g of sodium methoxide, 0.15 g of sodium o-phenylphenolate, 3.0 g of toluene, and 0.2 g of strontium nitrate were added sequentially to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomer was added to the system, and the reaction was carried out at 120℃ for 4 h. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The obtained solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 93%.

[0041] Example 4

[0042] Glass fiber reinforced epoxy resin composite material was placed in a vanadium pentoxide acetic acid solution and subjected to oxidative degradation at 60°C for 10 h. After the reaction, epoxy oligomers and glass fibers were separated. Subsequently, 3.0 g of sodium phosphate, 0.1 g of sodium p-chlorophenolate, 6.0 g of tetrahydrofuran, and 0.4 g of barium nitrate were added sequentially to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomer was added to the system, and the reaction was carried out at 90°C for 10 h. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 89%.

[0043] Example 5

[0044] Carbon fiber reinforced epoxy resin composite material was placed in a zinc chloride ethanol solution and hydrolyzed at 210°C for 3 hours. After the reaction, epoxy oligomers and carbon fibers were separated. Subsequently, 3.5 g of tetramethylammonium hydroxide, 0.08 g of sodium o-nitrophenolate, 5.5 g of cyclohexane, and 0.18 g of copper nitrate were added sequentially to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomer was added to the system, and the reaction was carried out at 160°C for 4 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The obtained solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 95%.

[0045] Example 6

[0046] Pure epoxy resin was placed in acetic acid and subjected to acetylation at 280°C for 2 hours. After the reaction, epoxy oligomers were obtained. Subsequently, 1.5 g of strontium hydroxide, 0.2 g of sodium catechol, 4.0 g of ethylene glycol, and 0.3 g of sodium nitrate were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers was added, and the reaction was carried out at 80°C for 12 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 94%.

[0047] Example 7

[0048] Pure epoxy resin was placed in ethanolamine and subjected to aminolysis at 180°C for 15 h. After the reaction, epoxy oligomers were separated. Subsequently, 3.5 g of potassium acetate, 0.25 g of sodium α-naphthol, 7.0 g of propylene glycol methyl ether, and 0.12 g of ferric nitrate were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers was added, and the reaction was carried out at 130°C for 9 h. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 91%.

[0049] Example 8

[0050] Pure epoxy resin was placed in an aluminum nitrate N,N-dimethylacetamide solution and subjected to oxidative degradation at 160°C for 5 hours. After the reaction, epoxy oligomers were separated. Subsequently, 2.8 g of potassium tert-butoxide, 0.05 g of potassium phenolate, 4.5 g of cyclohexanol, and 0.08 g of nickel nitrate were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers was added, and the reaction was carried out at 100°C for 8 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 88%.

[0051] Example 9

[0052] Pure epoxy resin was placed in an aqueous solution of zinc chloride and hydrolyzed at 220°C for 9 hours. After the reaction, epoxy oligomers were obtained. Subsequently, 1.0 g of lithium hydroxide, 0.3 g of sodium phenolate, 6.5 g of ethylene glycol monobutyl ether, and 0.15 g of zinc nitrate were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers was added, and the reaction was carried out at 150°C for 0.5 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 99%.

[0053] Comparative Example 1

[0054] Pure epoxy resin was placed in an aqueous solution of zinc chloride and hydrolyzed at 220°C for 9 hours. After the reaction, epoxy oligomers were obtained. Subsequently, 1.0 g of lithium hydroxide and 6.5 g of ethylene glycol monobutyl ether were added sequentially to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers were added, and the mixture was reacted at 150°C for 5 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 95%.

[0055] Comparative Example 2

[0056] Pure epoxy resin was placed in an aqueous solution of zinc chloride and hydrolyzed at 220°C for 9 hours. After the reaction, epoxy oligomers were obtained. Subsequently, 1.0 g of lithium hydroxide, 6.5 g of ethylene glycol monobutyl ether, and 0.15 g of zinc nitrate were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers were added, and the reaction was carried out at 150°C for 3 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 97%.

[0057] Comparative Example 3

[0058] Pure epoxy resin was placed in an aqueous solution of zinc chloride and hydrolyzed at 220°C for 9 hours. After the reaction, epoxy oligomers were obtained. Subsequently, 1.0 g of lithium hydroxide, 0.3 g of sodium phenolate, and 6.5 g of ethylene glycol monobutyl ether were sequentially added to a reaction vessel and mixed thoroughly to prepare a reaction system. Then, 1.0 g of the aforementioned epoxy oligomers were added, and the reaction was carried out at 150°C for 2 hours. After the reaction was completed, the reaction vessel was allowed to cool naturally to room temperature. The reaction solution was acidified and filtered. The resulting solid was washed with water and dried to obtain bisphenol A. Under these reaction conditions, the epoxy oligomers were completely converted, and the yield of bisphenol A was 98%.

[0059] Contents not described in detail in this specification are prior art known to those skilled in the art. Although illustrative specific embodiments of the invention have been described above to facilitate understanding by those skilled in the art, it should be understood that the invention is not limited to the scope of the specific embodiments. Various modifications are readily apparent to those skilled in the art as long as they fall within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of this invention are protected.

Claims

1. A method for recovering bisphenol A from epoxy resin degradation products, characterized in that: Includes the following steps: Step 1: Degrade bisphenol A type epoxy resin waste through chemical recycling to obtain epoxy resin degradation products, namely epoxy oligomers. Step 2: The epoxy oligomer, inorganic base catalyst, co-catalyst, solvent and nitrate are mixed in a certain proportion and reacted. After the reaction is completed, the product is separated and purified to obtain bisphenol A. The structure of the epoxy oligomer is as follows: ； Among them, R 1 and R 2 Each independently is an alkyl group, , , , , , , , , , , , , , , Or H.

2. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: In step 2, the solvent is one or a mixture of several of the following in any proportion: hydrocarbons, amides, ethers, or alcohols.

3. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: In step 2, the co-catalyst is one or a mixture of several of the following: sodium phenolate, potassium phenolate, sodium o-cresol, potassium o-cresol, sodium o-phenylphenolate, sodium p-chlorophenolate, sodium o-nitrophenolate, sodium catechol, and sodium α-naphthol.

4. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: The inorganic base catalyst in step 2 is one or a mixture of several of the following: hydroxides, amino compounds, imino compounds, metal alkyl / aryl compounds, metal oxides, quaternary ammonium bases, alkoxides, carbonates, bicarbonates, phosphates, silicates, acetates, and borates.

5. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: In step 2, the nitrate is one or a mixture of several of the following in any proportion: ammonium nitrate, potassium nitrate, strontium nitrate, barium nitrate, copper nitrate, silver nitrate, iron nitrate, nickel nitrate, calcium nitrate, sodium nitrate, magnesium nitrate, aluminum nitrate, zinc nitrate, chromium nitrate, and cerium ammonium nitrate.

6. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: In step 2, the reaction temperature is 80–160°C and the reaction time is 0.5–12 h.

7. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: In step 2, the mass ratio of epoxy oligomer, inorganic base catalyst, co-catalyst, solvent and nitrate is 1:1-4:0.03-0.3:3-8:0-0.

4.

8. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: The bisphenol A type epoxy resin waste in step 1 includes pure epoxy resin and carbon fiber or glass fiber reinforced composite materials based thereon.

9. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: The chemical recovery method in step 1 is hydrolysis, alcoholysis, aminolysis, acetyllysis, oxidative degradation, supercritical / subcritical fluid degradation, Lewis acid catalytic degradation, oxidation / acid hydrolysis, oxidation / alkali hydrolysis, or pyrolysis; the reaction temperature in step 1 is 60–300℃, and the reaction time is 0.5–24h.

10. The method for recovering bisphenol A from epoxy resin degradation products according to claim 1, characterized in that: The separation and purification in step 2 includes: acidifying the reaction solution and filtering it, then washing and drying the resulting solid to obtain bisphenol A.

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