A method for the complete degradation of polycarbonate plastics in polyether solvents

Abstract

This invention belongs to the field of polymer materials, specifically a method for the complete degradation of polycarbonate plastics in polyether solvents. This invention enables the efficient and selective degradation of various types of polycarbonate plastics to obtain corresponding monomers and their derivatives under oil bath heating or microwave assistance, with or without an alkaline catalyst. This method features a simple reaction system, short reaction time, simple operation, and environmental friendliness.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, specifically relating to a method for degrading polycarbonate plastics. Background Technology

[0002] Plastic products are durable, inexpensive, and portable, and are used in all aspects of production and daily life. However, due to their good durability, they are difficult to degrade. As a result, a total of 6.3 billion tons of waste plastic have accumulated in the environment globally, and it is estimated that 12 billion tons of plastic waste will be generated between 2020 and 2050. Plastic waste not only causes environmental pollution but also affects human health. Therefore, to reduce the harm of plastics, recycling and reuse are necessary. Plastic recycling methods can be divided into five categories: melt remolding, mechanical recycling, energy utilization, biodegradation, and chemical degradation. Compared to other recycling methods, biodegradation and chemical degradation can theoretically achieve the complete transformation of plastics into corresponding monomers or related high-value products, and have therefore received widespread attention. In comparison, biodegradation has specificity, while chemical degradation has good universality, and is therefore considered a more ideal and superior method of plastic recycling and reuse.

[0003] Polybisphenol A (PBA) carbonate, an engineering plastic, possesses advantages such as high impact resistance and electrical insulation, and is widely used in industries such as electrical appliances and medical devices, with its production increasing to 5 million tons annually. Waste PBA carbonate slowly releases bisphenol A (BPA) into the natural environment, causing pollution. Therefore, the chemical recycling and reuse of PBA carbonate is crucial. Currently, the main strategies for the chemical recycling and reuse of PBA carbonate include pyrolysis, hydrolysis, aminolysis, and alcoholysis. Existing literature reports that using an alcoholysis strategy, with ethanolamine as a nucleophile, PBA carbonate can be degraded to BPA in 99% yield in dimethyl sulfoxide solvent (Green Chem., 2023, 25, 952-959.). Meanwhile, methods for the degradation of polybisphenol A carbonate using a hydrolysis strategy under microwave assistance have been reported, yielding bisphenol A in 80% yield using a 5% sodium hydroxide aqueous solution at 160°C (J. Hazard. Mater. 2012, 241-242, 137-145.). All of the above degradation methods require the addition of small molecule compounds and strong bases, limiting their industrial application prospects. Therefore, there is an urgent need to develop a new method suitable for industrial-scale degradation of plastics into monomers that does not require the addition of additional small molecule compounds, solvents, or strong base catalysts. This invention achieves the efficient conversion of polycarbonate plastics into corresponding monomers and high-value derivatives in polyether solvents under oil bath heating or microwave assistance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for the complete degradation of polycarbonate plastics that has a short reaction time, simple conditions, and easy operation.

[0005] The method for the complete degradation of polycarbonate plastics provided by this invention involves reacting in a polyether solvent, under oil bath heating or microwave assistance, at a temperature of 50–250°C, in a sealed environment for 1 minute to 48 hours. Polyether solvents, represented by polyethylene glycol, are used to degrade polycarbonate plastics with or without a catalyst, yielding corresponding polymer monomers (such as bisphenol A) molecules or their derivatives.

[0006] In this invention, the polyether solvent is selected from polyethylene glycol, polyethylene glycol monomethyl ether, polyethylene glycol dimethyl ether, polypropylene glycol, polypropylene glycol monomethyl ether, and polytetrahydrofuran, and its amount is 0.2 mL to 10 mL. Preferably, the polyether is a viscous liquid with an average molecular weight of 200-800.

[0007] In this invention, under oil bath heating conditions, the preferred reaction temperature is 50-150°C, and the preferred reaction time is 5 minutes to 24 hours.

[0008] In this invention, under microwave assistance, the preferred microwave power is 10-850W, the reaction temperature is 50-250℃, and the reaction time is 1 minute to 3 hours.

[0009] In this invention, the catalyst is selected from sodium sulfate, potassium sulfate, magnesium sulfate, barium hydroxide octahydrate, barium hydroxide, potassium hydroxide, sodium hydroxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, potassium ethoxide, calcium acetate, zinc acetate, sodium acetate, potassium acetate, ammonium acetate, sodium formate, potassium formate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, sodium lactate, potassium lactate, calcium lactate, magnesium lactate, and zinc lactate.

[0010] In this invention, the amount of catalyst used is 0-25 mol% (preferably 1-15 mol%) of the substrate, and the amount of substrate is calculated by dividing the total mass of the polymer by the molar mass of the polymer repeating unit.

[0011] In this invention, the polycarbonate plastic includes two main categories: aromatic polycarbonate and aliphatic polycarbonate, such as polybisphenol A carbonate, polypropylene carbonate, 1,3-propanediol polycarbonate, polyvinyl alcohol carbonate, polytrimethylene carbonate, polybutylene carbonate, and polypropylene glycol carbonate.

[0012] In this invention, after the reaction is complete, an appropriate amount of water is added to the reaction system, and the mixture is extracted with ethyl acetate. The organic layers are combined and dried with anhydrous magnesium sulfate. Taking polybisphenol A carbonate as an example, crude bisphenol A is obtained after removing the solvent under reduced pressure. Further purification using column chromatography (eluent: petroleum ether / ethyl acetate) or recrystallization techniques yields the corresponding polymer monomers or related high-value derivative compounds.

[0013] This invention enables the chemical degradation of polycarbonate into monomers of the corresponding polymer in a polyether solvent, under oil bath heating or microwave assistance, with or without a catalyst. Furthermore, compared to conditions without a catalyst, the catalyst increases the nucleophilicity of the polyether, thus promoting the chemical degradation of the polycarbonate.

[0014] This invention is the first to innovatively adopt a strategy of polymer (polyether) degradation of polymer (polycarbonate), which is environmentally friendly and has a simple reaction system.

[0015] Compared with existing technologies, the advantages of this invention are:

[0016] (1) The method of this invention achieves mild, rapid and efficient degradation of polycarbonate under catalyst-free conditions for the first time;

[0017] (2) This invention is the first to achieve mild, rapid and efficient chemical degradation of polycarbonate polymers in polyether solvents;

[0018] (3) This invention can be directly applied to degrading common commercially available plastic products whose main component is polybisphenol A carbonate, such as medical ointment jars, DVDs, water cups, goggles, polycarbonate sheets, and car headlight covers. Therefore, it has great practicality. Attached Figure Description

[0019] Figure 1 The image shows the 1H NMR spectrum of bisphenol A, the degradation product of polybisphenol A carbonate, in the example.

[0020] Figure 2 The image shows the 1H NMR spectrum of propylene carbonate, a degradation product of polypropylene carbonate, in the examples. Detailed Implementation

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0022] All materials involved in the following implementations are available from commercial sources.

[0023] The method for detecting degradation products in this invention is: nuclear magnetic resonance hydrogen spectroscopy.

[0024] The method for calculating the yield of degradation products of the present invention is as follows:

[0025]

[0026]

[0027] Example 1: Degradation of polybisphenol A carbonate under microwave-assisted, catalyst-assisted conditions

[0028]

[0029] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate, 0.01 mmol of catalyst, and 3 mL of PEG were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The microwave power was set to 50 W, and the reaction was carried out at 170 °C for 1 hour. After cooling to room temperature, an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried with anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation to remove the solvent. Bisphenol A was purified by column chromatography and the product was dried under vacuum. Figure 1 The 1H NMR spectrum of the degradation product bisphenol A.

[0030] Cat. <![CDATA[Ba(OH)2·8H2O]]> NaOH <![CDATA[ t Good]]> <![CDATA[KH2PO4]]> <![CDATA[NaH2PO4]]> <![CDATA[Na2CO3]]> <![CDATA[K3PO4]]> Yield 99％ 92％ 97％ 98％ 97％ 99％ 90％ Cat. <![CDATA[CH3COOZn]]> EtONa <![CDATA[NaHCO3]]> <![CDATA[Cs2CO3]]> <![CDATA[K2CO3]]> KOH <![CDATA[ t Full]]> Yield 99％ 88％ 99％ 99％ 94％ 98％ 98％ Cat. Zinc lactate Sodium lactate <![CDATA[KHCO3]]> <![CDATA[Na2CO3]]> MeONa <![CDATA[Na2HPO4]]> none Yield 90％ 91％ 99％ 99％ 90％ 98％ 77％

[0031] In the following examples where a catalyst is required, potassium hydroxide is used as the catalyst.

[0032] Example 2: Degradation of polybisphenol A carbonate with potassium hydroxide as a catalyst under oil bath heating conditions

[0033]

[0034] In a sealed tube, polybisphenol A carbonate (0.2 mmol), KOH (0.03 mmol), and PEG (3 mL) were added sequentially. The tube was sealed and placed in an oil bath. The reaction was carried out at 140 °C for 24 hours. After cooling to room temperature, an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried under reduced pressure to remove the solvent. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0035] Example 3: Degradation of medical drug containers using potassium hydroxide as a catalyst under microwave conditions

[0036]

[0037] Medical canisters containing polycarbonate purchased from the market were shredded. In a microwave reaction tube, the shredded medical canister (1 mmol), KOH (0.05 mmol), and PEG (3 mL) were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 170°C for 1 hour. After cooling to room temperature, an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. Bisphenol A was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0038] Example 4: Degradation of polybisphenol A carbonate in PEG 400 solvent under microwave conditions

[0039]

[0040] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 3 mL of PEG 400 were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 1 hour, cooled to room temperature, and a suitable amount of water was added. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. The solvent was removed, and the product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0041] Example 5: Degradation of polypropylene carbonate under microwave conditions using potassium hydroxide as a catalyst

[0042]

[0043] In a microwave-safe reaction tube, polypropylene carbonate (1 mmol), KOH (0.05 mmol), and PEG (3 mL) were added sequentially. The tube was then sealed and placed in a microwave reactor. The reaction was carried out at 170°C for 1 hour, cooled to room temperature, and purified to obtain propylene carbonate. The product was dried under vacuum. The calculated yield of propylene carbonate was 80%. Figure 2 The 1H NMR spectrum of the degradation product propylene carbonate is shown.

[0044] Example 6: Rapid degradation of polypropylene carbonate under microwave-assisted, catalyst-free conditions

[0045]

[0046] In a microwave-safe reaction tube, polypropylene carbonate (0.2 mmol) and PEG (0.5 mL) were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and purified to obtain propylene carbonate. The product was dried under vacuum. The calculated yield of propylene carbonate was 27%. Figure 2 The 1H NMR spectrum of the degradation product propylene carbonate is shown.

[0047] Example 7: Rapid degradation of polybisphenol A carbonate under microwave-assisted, catalyst-free conditions

[0048]

[0049] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 3 mL of PEG were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried under reduced pressure to remove the solvent. The resulting product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0050] Example 8: Degradation of polybisphenol A carbonate under microwave-assisted, catalyst-free conditions

[0051]

[0052] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 0.5 mL of PEG were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 1 hour, cooled to room temperature, and a suitable amount of water was added. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried under reduced pressure to remove the solvent. The resulting product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0053] Example 9: Degradation of polybisphenol A carbonate under microwave-assisted, catalyst-free conditions

[0054]

[0055] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 0.5 mL of PEG 200 were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 10 minutes, cooled to room temperature, and a suitable amount of water was added. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried under reduced pressure to remove the solvent. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0056] Example 10: Degradation of polybisphenol A carbonate in polypropylene glycol solvent

[0057]

[0058] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 0.5 mL of PPG were added sequentially. The tube was sealed and placed in a microwave reactor. The reaction was carried out at 200 °C for 1 hour. After cooling to room temperature, a suitable amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried under reduced pressure to remove the solvent. The solvent was removed by distillation under reduced pressure, and the product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 65%.

[0059] Example 11: Degradation of polybisphenol A carbonate under microwave-assisted, catalyst-free conditions

[0060]

[0061] In a microwave-safe reaction tube, 0.2 mmol of polybisphenol A carbonate and 0.5 mL of PEG were added sequentially. The tube was sealed and placed in a microwave reactor. The microwave power was set to 500 W, and the reaction was carried out at 200°C for 5 minutes. After cooling to room temperature, an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. The solvent was removed, and the product was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0062] Example 12: Rapid degradation of goggles under microwave-assisted, catalyst-free conditions

[0063]

[0064] The goggles purchased from the market were shredded. In a microwave reaction tube, the shredded goggles (0.2 mmol) and PEG (0.5 mL) were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. Bisphenol A was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0065] Example 13: Rapid degradation of a water cup under microwave-assisted, catalyst-free conditions

[0066]

[0067] The water cup purchased from the market was shredded. In a microwave reaction tube, the shredded water cup (0.2 mmol) and PEG (0.5 mL) were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried. The solvent was removed by vacuum distillation, and the product was purified by column chromatography to obtain bisphenol A. The product was then dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0068] Example 14: Rapid degradation of medical drug containers under microwave-assisted, catalyst-free conditions

[0069]

[0070] Medical canisters purchased from the market were shredded. In a microwave reaction tube, 0.2 mmol of the shredded medical canister and 0.5 mL of PEG were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. Bisphenol A was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0071] Example 15: Rapid degradation of DVD discs under microwave-assisted, catalyst-free conditions

[0072]

[0073] DVDs purchased from the market were shredded. In a microwave reaction tube, 0.2 mmol of the shredded DVD and 0.5 mL of PEG were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. Bisphenol A was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 87%.

[0074] Example 16: Rapid degradation of polycarbonate panels under microwave-assisted, catalyst-free conditions

[0075]

[0076] The purchased polycarbonate sheet was shredded. In a microwave reaction tube, 0.2 mmol of the shredded polycarbonate sheet and 0.5 mL of PEG were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were removed by vacuum distillation. Bisphenol A was purified by column chromatography and dried under vacuum. The yield of bisphenol A was calculated to be 99%.

[0077] Example 17: Rapid degradation of automotive headlight covers under microwave-assisted, catalyst-free conditions

[0078]

[0079] Samples were taken from automotive headlight covers purchased from the market. In a microwave reaction tube, 0.2 mmol of automotive headlight cover cut into pieces and 0.5 mL of PEG were added sequentially. The reaction tube was sealed and placed in a microwave reactor. The reaction was carried out at 200°C for 5 minutes, cooled to room temperature, and an appropriate amount of water was added to the reaction system. The mixture was extracted with ethyl acetate, dried over anhydrous sodium sulfate, and the combined organic layers were dried. The solvent was removed by vacuum distillation, and the product was purified by column chromatography to obtain bisphenol A. The product was then dried under vacuum. The yield of bisphenol A was calculated to be 99%.

Claims

1. A method for the complete degradation of polycarbonate plastic in a polyether solvent, characterized in that, Under microwave assistance, at a temperature of 50~250 ℃, a closed reaction is carried out for 1 minute to 48 hours, with or without a catalyst, to degrade polybisphenol A carbonate and obtain bisphenol A monomer molecules. The polyether solvent is selected from polyethylene glycol; The catalyst is selected from sodium sulfate, potassium sulfate, magnesium sulfate, barium hydroxide octahydrate, barium hydroxide, potassium hydroxide, sodium hydroxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, potassium ethoxide, calcium acetate, zinc acetate, sodium acetate, potassium acetate, ammonium acetate, sodium formate, potassium formate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, sodium lactate, potassium lactate, calcium lactate, magnesium lactate, and zinc lactate. The catalyst dosage is 0-25 mol% of the substrate. The amount of substrate is calculated by dividing the total polymer mass by the molar mass of the polymer repeating unit.

2. A method for the complete degradation of polycarbonate plastic in a polyether solvent, characterized in that, Under oil bath heating, at a temperature of 50~250 ℃, and in a closed reaction for 1 minute to 48 hours, bisphenol A carbonate is degraded to obtain bisphenol A monomer molecules under the presence of a catalyst. The polyether solvent is selected from polyethylene glycol; The catalyst is selected from sodium sulfate, potassium sulfate, magnesium sulfate, barium hydroxide octahydrate, barium hydroxide, potassium hydroxide, sodium hydroxide, zinc hydroxide, magnesium hydroxide, calcium hydroxide, potassium tert-butoxide, sodium tert-butoxide, sodium ethoxide, potassium ethoxide, calcium acetate, zinc acetate, sodium acetate, potassium acetate, ammonium acetate, sodium formate, potassium formate, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, cesium carbonate, sodium lactate, potassium lactate, calcium lactate, magnesium lactate, and zinc lactate. The catalyst dosage is 1-25 mol% of the substrate, and the amount of substrate is calculated by dividing the total polymer mass by the molar mass of the polymer repeating unit.

3. The method according to claim 1 or 2, characterized in that, The amount of polyethylene glycol used is 0.2 mL to 10 mL.

4. The method according to claim 1, characterized in that, With microwave assistance, the microwave power is 10~850 W, the reaction temperature is 50~250 ℃, and the reaction time is 1 minute~3 hours.

5. The method according to claim 2, characterized in that, Under oil bath heating conditions, the reaction temperature is 50~150 ℃, and the reaction time is 5 minutes to 24 hours.

6. The method according to claim 1 or 2, characterized in that, After the reaction was completed, an appropriate amount of water was added to the reaction system, and the mixture was extracted with ethyl acetate. The organic layers were combined and dried with anhydrous magnesium sulfate. The corresponding bisphenol A was obtained by further purification using column chromatography or recrystallization.

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