A method of recycling mixed plastics

Abstract

The embodiment of the present application provides a recycling method of mixed plastics, comprising the following steps: reacting mixed plastics to obtain a recycling product; the mixed plastics comprise ester plastics and polyvinyl chloride, and the mass ratio of the ester plastics to the polyvinyl chloride is 1:(0.1-10); the temperature of the reaction is 180-350 DEG C, and the time of the reaction is 3-52 h. The above steps are used to recycle the mixed plastics, and the mixed plastics comprising ester plastics and PVC are used as raw materials. When the reaction is carried out, the chlorine element (Cl) in the PVC is removed in the form of HCl through heat dechlorination treatment, HCl is used as an acid catalyst and / or depolymerization agent to participate in the reaction, the ester plastics are converted into chlorinated derivatives and / or depolymerized into corresponding monomers; and then the PVC after dechlorination and not containing a toxicizing agent is converted into corresponding products. In this way, the recycling of the mixed plastics comprising ester plastics and PVC is realized, and the ester plastics and the PVC in the mixed plastics are both recycled into high-value recycling products with high efficiency.

Description

Technical Field

[0001] This application relates to the field of organic intermediate synthesis technology, and in particular to a method for recycling mixed plastics. Background Technology

[0002] Since their commercialization, plastics have played a vital role in human production and daily life. However, the massive production and disposal of plastics, along with inadequate end-of-life management practices, have caused serious environmental problems and resource waste. Therefore, the recycling of waste plastics through physical / mechanical, chemical, or biological methods has received widespread attention from academia and industry. For example, polyethylene terephthalate (PET) is one of the most commonly used thermoplastic polymers in the packaging and textile industries. Besides the simple physical / mechanical method of recovering its raw polymer, it can also be depolymerized into monomers and repolymerized into polymers through chemical or biological recycling methods. However, these processes typically require clean, single-component raw materials to ensure good recycled polymer performance and a high number of recycling cycles. In reality, however, plastic waste is usually a complex mixture containing various polymer components, plastic additives, and other contaminants. For example, PET and polyvinyl chloride (PVC) plastics, with similar densities, are often difficult to completely separate using simple methods. Furthermore, due to differences in melting points and thermal stability, contamination from other plastics significantly limits the quality of recycled materials. Furthermore, PVC readily generates chlorine-containing inorganic or organic compounds during processing, leading to problems such as product quality degradation, catalyst poisoning, and reactor corrosion. While these adverse effects can be mitigated by adding absorbents, this also results in the waste of chlorine and an equivalent amount of absorbent. Therefore, designing a highly efficient recycling system to recover mixed plastics into high-value chemicals has become a pressing technical problem for those skilled in the art. Summary of the Invention

[0003] The purpose of this application is to provide a method for recycling mixed plastics, realizing the recycling of mixed plastics and transforming them into high-value recycled products. The specific technical solution is as follows:

[0004] This application provides a method for recycling mixed plastics, comprising the following steps: reacting the mixed plastics to obtain recycled products; wherein the mixed plastics include ester plastics and polyvinyl chloride (PVC), the mass ratio of ester plastics to PVC is 1:(0.1-10); the reaction temperature is 180-350℃, and the reaction time is 3-52h.

[0005] The above steps provide a novel pathway for the co-conversion of ester plastics and PVC. This pathway uses a mixed plastic comprising ester plastics and PVC as raw materials. During the reaction, chlorine (Cl) in the PVC is first removed as HCl through thermal dechlorination. HCl acts as an acid catalyst and / or depolymerizing agent, converting the ester plastic into chlorinated derivatives and / or depolymerizing them into corresponding monomers. Then, the dechlorinated PVC, free of poisonous agents, is converted back into the corresponding products. This achieves the recycling of mixed plastics including ester plastics and PVC, efficiently recovering both ester plastics and PVC into high-value recyclables (chemicals). Furthermore, during the reaction, the HCl generated by PVC converts and / or depolymerizes the ester plastics, acting as an acid catalyst and / or depolymerizing agent, thus improving the conversion rate of the ester plastics and the yield of the recycled products. The recycling method of this application uses readily available raw materials, has a simple process, and can be widely applied in industrial production.

[0006] In this application, the above-mentioned thermal dechlorination treatment is a thermal dechlorination treatment known in the art. Specifically, thermal dechlorination treatment refers to the process in which chlorine in PVC is removed in the form of HCl at a reaction temperature during the recycling of mixed plastics.

[0007] In some embodiments of this application, the reaction is carried out under solvent-free conditions, i.e., no solvent (such as ionic liquid or molten salt) is added to the mixed plastics, and the mixed plastics are placed in a sealed container for the reaction. The reaction temperature is 250-350°C, and the reaction time is 10-48 hours. When the mixed plastics are reacted under solvent-free conditions, controlling the reaction temperature and time within the above ranges is beneficial for the removal of chlorine from the PVC in the form of HCl. In this way, HCl acts as an acid catalyst and / or depolymerization agent to promote the conversion of ester plastics into chlorinated derivatives and / or depolymerization into the corresponding monomers. After dechlorination treatment, the PVC also forms PVC without poisonous agents (such as HCl) and is thus converted into the corresponding products. Therefore, it is beneficial to efficiently recover both the ester plastics and PVC in the mixed plastics into high-value chemicals.

[0008] In this application, as shown in reaction formula (1), PVC (weight average molecular weight 10) is used. 4 -10 6 When placed in a sealed container, the Cl in PVC is released as HCl at a temperature of 250-350℃. Specifically, at about 250℃, the Cl in PVC begins to be released as HCl, and when heated to about 350℃, the Cl in PVC can be almost completely released. The released HCl can be used as a depolymerizing agent and acid catalyst for ester plastics. The remaining part of PVC is converted into dehydrochlorinated polyvinyl chloride (DHPVC), and the mass content of chlorine in the remaining part is less than 3% and the mass content of oxygen is less than 5%.

[0009]

[0010] In some embodiments of this application, the reaction is carried out in a reaction medium, which is an ionic liquid, with a mass ratio of ionic liquid to ester plastics of 1:(0.05-1); the reaction temperature is 180-230°C, and the reaction time is 3-52 h. In some embodiments, the reaction time is 6-52 h. In some embodiments, the reaction time is 6-12 h. Using an ionic liquid as the reaction medium is beneficial for lowering the reaction temperature, and the recycling process of the mixed plastics does not need to be carried out in a sealed container. The ionic liquid not only serves as a good mass and heat transfer medium for the plastic reaction system, but also as a chloride ion buffer system. HCl generated from the thermal dechlorination of PVC is stored in the reaction system for the depolymerization and catalysis of the ester plastics, thereby improving the conversion rate of the ester plastics and the yield of the corresponding chemicals. Controlling the mass ratio of ionic liquid to ester plastics within the above range is beneficial for the efficient recycling of both ester plastics and PVC into high-value chemicals. Furthermore, it is beneficial for improving the conversion rate of ester plastics and PVC, as well as the yield of the recycled products.

[0011] In some embodiments of this application, the ionic liquid is selected from any one of tetrabutylphosphine chloride (Bu4PCl), 1-ethyl-3-methylimidazolium chloride (EmimCl), tetrabutylammonium chloride (Bu4NCl), and 1-ethyl-3-methylimidazolium tetrafluoroborate (EmimBF4). In some embodiments, the ionic liquid is selected from Bu4PCl or EmimCl. In some embodiments, the ionic liquid is selected from Bu4PCl. Taking Bu4PCl as an example, each gram of ionic liquid can absorb approximately 0.09 g of HCl gas and buffer approximately 0.06 g of HCl gas.

[0012] In this application, after PVC is placed in an ionic liquid and reacted at 100-180°C for 0.4-48 hours, the Cl content in the PVC is determined using X-ray fluorescence spectrometry (XRF). The residual Cl content in the PVC is 5-50%, indicating that Cl can be released from the PVC in a relatively high amount. In some embodiments, 2-5g of PVC is placed in 29-31g of the ionic liquid Bu4PCl and reacted at 100-180°C for 0.5-48 hours. The Cl content in the PVC is then determined using XRF, and the residual Cl content is 5.5-15.2%. In some embodiments, 2-4g of PVC is placed in 29-31g of the ionic liquid EmimCl and reacted at 100-180°C for 0.4-0.6 hours. The Cl content in the PVC is then determined using XRF, and the residual Cl content is 37.6-48.2%.

[0013] In some embodiments of this application, the reaction is carried out in a reaction medium, which is a molten salt, with a mass ratio of molten salt to ester plastics of 1:(0.01-0.2); the reaction temperature is 200-350°C, and the reaction time is 10-24 hours. Using a molten salt as the reaction medium is beneficial for the release of HCl from PVC and for the activation and conversion of HCl. Controlling the mass ratio of molten salt to ester plastics within the above range is beneficial for the efficient recovery of both ester plastics and PVC into high-value chemicals. Furthermore, it helps to improve the conversion rate of ester plastics and PVC, as well as the yield of the recovered products.

[0014] In some embodiments of this application, the molten salt is selected from either a NaCl-KCl-ZnCl2 mixture or a NaCl-KCl-MgCl2 mixture. Further, the mass ratio of NaCl, KCl, and ZnCl2 in the NaCl-KCl-ZnCl2 mixture is 1:(0.8-1.5):(2-4), and the mass ratio of NaCl, KCl, and MgCl2 in the NaCl-KCl-MgCl2 mixture is 1:(0.8-1.5):(2-4). It should be noted that the NaCl-KCl-ZnCl2 mixture is obtained by directly mixing NaCl, KCl, and ZnCl2, and the NaCl-KCl-MgCl2 mixture is obtained by directly mixing NaCl, KCl, and MgCl2.

[0015] In some embodiments of this application, a catalyst may be added during the reaction, with a catalyst-to-ester plastic mass ratio of 1:(2-56). The catalyst is an acid catalyst, comprising any one of Lewis acid catalysts, proton acid catalysts, and solid acid catalysts. The Lewis acid is selected from any one of ZnCl2, FeCl3, AlCl3, and Sc(OTf)3. The proton acid catalyst is selected from H2SO4. The solid acid catalyst is selected from H-ZSM-5 molecular sieve. In some embodiments, the catalyst is ZnCl2. In some embodiments, the catalyst is FeCl3. In some embodiments, the catalyst is H2SO4. The addition of the above-mentioned types and amounts of catalysts is beneficial to improving the conversion rate of PVC and ester plastics, as well as the yield of recycled products.

[0016] In some embodiments of this application, the size of the ester plastic is 0.1-3 mm. Controlling the size of the ester plastic within this range, resulting in a smaller size, facilitates more complete depolymerization and / or conversion of the ester plastic, thereby accelerating the generation rate of recycled products while achieving the conversion of the ester plastic into its corresponding chemicals.

[0017] This application does not impose any particular restrictions on the size of the PVC, as long as it can achieve the purpose of this application. For example, a PVC size of 0.1-3 mm is beneficial for the removal of chlorine during the thermal dechlorination process and for accelerating the generation rate of recycled products.

[0018] In this application, size refers to average particle size, and more specifically, average particle size refers to the average diameter of the mixed plastic particles or powder.

[0019] In some embodiments of this application, ester plastics include ester polymers selected from at least one of polyethylene terephthalate (PET), polybutylene terephthalate, polylactic acid, polycaprolactone, polyglycolic acid, polyhydroxyalkanoates, polybutylene succinate, polybutylene adipate, polyhexyl adipate, polycarbonate, and polyurethane; wherein the polyhydroxyalkanoate is selected from at least one of poly-β-hydroxybutyrate, polyhydroxyvalerate, polyhydroxyhexanoate, and polyhydroxyoctanoate.

[0020] In some embodiments of this application, the ester-based plastics further include ester additives, including diphthalate. This application does not impose any particular limitation on the type of diphthalate, as long as it achieves the purpose of this application. For example, diphthalates include dibutyl phthalate, diisobutyl phthalate, benzyl butyl phthalate, di(2-ethylhexyl) phthalate, etc.

[0021] In this application, recycled products refer to chemicals corresponding to ester plastics and chemicals corresponding to PVC obtained by converting and / or depolymerizing mixed plastics using the recycling method of this application.

[0022] In some embodiments of this application, the recovered product is selected from at least one of terephthalic acid (TPA), dichloroethane (EDC), dichlorobutane, dichloroethanol terephthalate, phthalic acid, dichlorobutanol phthalate, hydrogen chloride (HCl), and dehydrochlorinated polyvinyl chloride (DHPVC).

[0023] In this application, conversion rate refers to the percentage of mixed plastics (ester plastics and PVC) converted, wherein the conversion rate of ester plastics = (ester plastics that have undergone depolymerization / amount of ester plastics fed) × 100%, and the conversion rate of PVC = (PVCs that have undergone dehydrochlorination / amount of PVC fed) × 100%. Yield refers to the percentage of various recycled products generated by the recycling method of this application, calculated based on the amount of a specific reactant fed. For example, when the ester plastic is PET, the TPA yield = (TPA generated from the depolymerization reaction / total amount of TPA monomers in the fed PET) × 100%, the dichloroethanol terephthalate yield = (dichloroethanol terephthalate generated from the depolymerization reaction / total amount of TPA monomers in the fed PET) × 100%, and the EDC yield = (EDC generated from the depolymerization reaction / total amount of ethylene glycol monomers in the fed PET) × 100%.

[0024] Beneficial effects of the embodiments in this application:

[0025] This application provides a method for recycling mixed plastics, comprising the following steps: reacting the mixed plastics to obtain recycled products; the mixed plastics include ester plastics and polyvinyl chloride (PVC), with a mass ratio of ester plastics to PVC of 1:(0.1-10); the reaction temperature is 180-350℃, and the reaction time is 3-52 hours. Using the above steps to recycle mixed plastics, with ester plastics and PVC as raw materials, during the reaction, the chlorine element (Cl) in the PVC is first removed in the form of HCl through thermal dechlorination. HCl acts as an acid catalyst and / or depolymerizing agent in the reaction, converting the ester plastics into chlorinated derivatives and / or depolymerizing them into corresponding monomers; then, the PVC without toxic agents after dechlorination is converted into the corresponding products. In this way, the recycling of mixed plastics including ester plastics and PVC is achieved, efficiently recovering both the ester plastics and PVC in the mixed plastics into high-value recyclables (chemicals). Furthermore, during the above reaction process, PVC generates HCl, which converts and / or depolymerizes ester plastics, acting as an acid catalyst and / or depolymerizing agent, thereby improving the conversion rate of ester plastics and the yield of recycled products. The recycling method of this application uses readily available raw materials, has a simple process, and can be widely applied in industrial production.

[0026] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0028] Figure 1 The chromatogram of the recovered product in Example 1 is obtained by gas chromatography-mass spectrometry (GC-MS).

[0029] Figure 2 The 1H NMR spectrum of terephthalic acid, the recovered product in Example 1;

[0030] Figure 3 This is a comparison graph showing the EDC generation rate of the recovered product in Examples 4, 6, and 13. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0032] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. It should be noted that in the following embodiments and comparative examples, PVC is polymerized from vinyl chloride monomer, and PET is polymerized from two monomers: terephthalic acid and ethylene glycol.

[0033] Test methods and equipment

[0034] Qualitative and quantitative analyses of the reaction systems of each example and comparative example were performed using GC-MS, gas chromatography, and nuclear magnetic resonance spectroscopy.

[0035] Example 1

[0036]

[0037] A solvent-free reaction system was selected. 100 mg of PET (0.52 mmol TPA monomer and 0.52 mmol ethylene glycol monomer, weight average molecular weight 10) was placed in a sealed, thick-walled glass tube. 4 -10 6 ) and 150 mg PVC (0.79 mmol vinyl chloride monomer, weight average molecular weight 10) 4 -10 6The reaction was carried out at 300℃ for 5 hours to obtain the recovered product (as shown in reaction formula (2)). After the reaction, there was an irritating odor of HCl in the tube. The recovered product was dissolved in 2.0 g of dimethylformamide (DMF), and the amount of each recovered product was found to be approximately 0.04 mmol TPA, 0.05 mmol EDC and 0.17 mmol dichloroethanol terephthalate by GC-MS and gas chromatography.

[0038] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0039] Example 2

[0040]

[0041] In a reaction system containing 6g of ionic liquid Bu4PCl, 300mg of PET (1.56mmol TPA monomer and 1.56mmol ethylene glycol monomer, with a weight-average molecular weight of 10) was added. 4 -10 6 ) and 500 mg PVC (2.63 mmol vinyl chloride monomer, weight average molecular weight 10) 4 -10 6 The product was reacted at 180°C for 3 hours to obtain the recovered product (as shown in reaction formula (3)). The recovered product was dissolved in 2.0 g DMF and analyzed by GC-MS and gas chromatography to obtain the amount of each recovered product as approximately 0.02 mmol TPA and 0.02 mmol EDC.

[0042] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0043] Example 3

[0044] Except for adjusting the reaction time to 12 hours, everything else is the same as in Example 2.

[0045] Example 4

[0046] Except for adjusting the reaction temperature to 230°C and the reaction time to 6 hours, the rest is the same as in Example 2.

[0047] Example 5

[0048]

[0049] In a reaction system containing 5g of a molten salt NaCl-KCl-ZnCl2 mixture (NaCl, KCl, and ZnCl2 in a mass ratio of 1:1:3), 300mg of PET (1.56mmol TPA monomer and 1.56mmol ethylene glycol monomer, with a weight-average molecular weight of 10) was added. 4 -106 ) and 500 mg PVC (2.63 mmol vinyl chloride monomer, weight average molecular weight 10) 4 -10 6 The product was reacted at 230℃ for 12 h to obtain the recovered product (as shown in reaction formula (3)). The recovered product was dissolved in 2.0 g DMF and analyzed by GC-MS and gas chromatography to obtain the amounts of various recovered products as 0.02 mmol TPA and 0.02 mmol EDC.

[0050] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0051] Example 6

[0052]

[0053] In a reaction system containing 6g of ionic liquid Bu4PCl, 300mg of PET (1.56mmol TPA monomer and 1.56mmol ethylene glycol monomer, with a weight-average molecular weight of 10) was added. 4 -10 6 ), 500mg PVC (2.63mmol vinyl chloride monomer, weight average molecular weight is 10). 4 -10 6 ) and 100 mg of catalyst ZnCl2 were reacted at 230 °C for 6 h to obtain the recovered product (as shown in reaction formula (4)). The recovered product was dissolved in 2 g DMF, and the amount of each recovered product was approximately 1.2 mmol TPA and 1.28 mmol EDC by GC-MS and gas chromatography.

[0054] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0055] Example 7

[0056]

[0057] Except for replacing ZnCl2 with FeCl3, the process is the same as in Example 6. The reaction process is shown in reaction formula (5).

[0058] Example 8

[0059]

[0060] Except for replacing ZnCl2 with H2SO4, the process is the same as in Example 6. The reaction process is shown in reaction formula (6).

[0061] Example 9

[0062]

[0063] Except for replacing ZnCl2 with Sc(OTf)3, the rest is the same as in Example 6. The reaction process is shown in reaction formula (7).

[0064] Example 10

[0065]

[0066] Except for replacing ZnCl2 with H-ZSM-5 molecular sieve, the process is the same as in Example 6. The reaction process is shown in reaction formula (8).

[0067] Example 11

[0068]

[0069] In a reaction system containing 5g of ionic liquid Bu4PCl, 5.6g of PET (29.12mmol TPA monomer and 29.12mmol ethylene glycol monomer, with a weight-average molecular weight of 10) was added. 4 -10 6 3.5g PVC (18.41mmol vinyl chloride monomer, weight average molecular weight 10) 4 -10 6 ) and 100 mg of catalyst ZnCl2 were reacted at 230 °C for 52 h to obtain the recovered product (as shown in reaction formula (3)). The recovered product was dissolved in 2 g DMF and analyzed by GC-MS and gas chromatography to obtain the amounts of various recovered products as 28.54 mmol TPA and 27.55 mmol EDC.

[0070] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0071] Example 12

[0072]

[0073] In a reaction system containing 5g of ionic liquid Bu4PCl, 300mg of PET (1.56mmol TPA monomer and 1.56mmol ethylene glycol monomer, with a weight-average molecular weight of 10) was added. 4 -10 6 3.0g PVC (15.6mmol vinyl chloride monomer, weight average molecular weight 10) 4 -10 6) and 100 mg of catalyst ZnCl2 were reacted at 230 °C for 6 h to obtain the recovered product (as shown in reaction formula (3)). The recovered product was dissolved in 2 g DMF and analyzed by GC-MS and gas chromatography to obtain the amount of each recovered product as approximately 1.52 mmol TPA and 1.48 mmol EDC.

[0074] The PET material has a diameter of 3.0 mm, while the PVC material has a diameter of 0.1 mm.

[0075] Example 13

[0076] Except for adjusting the size of the PET to 0.1 mm, everything else is the same as in Example 6.

[0077] Comparative Examples 1 to 3

[0078] Except for adjusting the relevant reaction parameters according to Table 1, everything else is the same as in Example 2.

[0079] The test results of Examples 1-13 and Comparative Examples 1-3 are shown in Table 1 and Figure 3 As shown.

[0080] Table 1

[0081]

[0082]

[0083] Note: "\" in Table 1 indicates no corresponding parameter; the difference between Example 6 and Example 13 is that the size of PET in Example 6 is 3.0 mm and the size of PET in Example 13 is 0.1 mm.

[0084] As can be seen from Examples 1-13 and Comparative Examples 1-3, when the mass ratio of ester plastics to PVC in the mixed plastic is within the range of this application, and the reaction temperature and time are within the range of this application, the mixed plastic can be converted into high-value recycled products after the reaction. However, in the comparative examples, the mass ratio of ester plastics to PVC is not within the range of this application, or the reaction temperature and time are not within the range of this application, and the mixed plastic cannot be converted into recycled products.

[0085] Figure 1 The GC-MS chromatogram of the recovered products in Example 1 is shown. As can be seen from the figure, the recovered products after the conversion of the mixed plastics in Example 1 include EDC and dichloroethanol terephthalate. Figure 2 The 1H NMR spectrum of terephthalic acid, the recovered product in Example 1, is shown.

[0086] As can be seen from Examples 1-5, under solvent-free conditions and when the reaction medium is an ionic liquid or molten salt, the mixed plastics can be converted into high-value recycled products under the conversion pathway of this application.

[0087] As can be seen from Examples 4 and 6-13, adding the catalyst of this application to the mixed plastics during the reaction process can further improve the conversion rate of PVC and ester plastics, as well as the yield of recycled products.

[0088] Figure 3 A comparative graph showing the EDC generation rate of the recovered product in Examples 4, 6, and 13 is presented. Specifically, Example 13 is curve (a), representing a PET particle size of 0.1 mm using the catalyst ZnCl2; Example 6 is curve (b), representing a PET particle size of 3.0 mm using the catalyst ZnCl2; and Example 4 is curve (c), representing a PET particle size of 3.0 mm without the use of a catalyst. The data in Table 1 and... Figure 3 As can be seen, the use of catalysts and the reduction of PET particle size can both accelerate the generation rate of EDC.

[0089] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, or article.

[0090] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0091] The above description is merely a preferred embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A method for recycling mixed plastics, comprising the following steps: The mixed plastics are reacted to obtain recycled products; The mixed plastic comprises ester plastics and polyvinyl chloride, wherein the mass ratio of the ester plastics to the polyvinyl chloride is 1:(0.1-10); in, The reaction is carried out under solvent-free conditions, at a temperature of 250-350°C, and for a time of 10-48 hours; or The reaction is carried out in a reaction medium, which is an ionic liquid, at a temperature of 180-230℃, and for a time of 3-52 hours; or The reaction is carried out in a reaction medium, which is a molten salt, at a temperature of 200-350°C, and for a time of 10-24 hours.

2. The method according to claim 1, wherein, The mass ratio of the ionic liquid to the ester plastic is 1:(0.05-1).

3. The method according to claim 2, wherein, The ionic liquid is selected from any one of tetrabutylphosphine chloride, 1-ethyl-3-methylimidazolium chloride, tetrabutylammonium chloride, and 1-ethyl-3-methylimidazolium tetrafluoroborate.

4. The method according to claim 1, wherein, The mass ratio of the molten salt to the ester plastic is 1:(0.01-0.2).

5. The method according to claim 4, wherein, The molten salt is selected from either a mixture of NaCl-KCl-ZnCl2 or a mixture of NaCl-KCl-MgCl2.

6. The method according to claim 1, wherein, A catalyst may also be added during the reaction, and the mass ratio of the catalyst to the ester plastic is 1:(2-56). The catalyst is an acid catalyst, which includes any one of Lewis acid catalysts, proton acid catalysts, and solid acid catalysts; the Lewis acid is selected from any one of ZnCl2, FeCl3, AlCl3, and Sc(OTf)3; the proton acid catalyst is selected from H2SO4; and the solid acid catalyst is selected from H-ZSM-5 molecular sieve.

7. The method according to claim 1, wherein, The size of the ester-based plastic is 0.1-3 mm.

8. The method according to claim 1, wherein, The ester-based plastics include ester polymers, which are selected from at least one of polyethylene terephthalate, polybutylene terephthalate, polylactic acid, polycaprolactone, polyglycolic acid, polyhydroxyalkanoates, polybutylene succinate, polybutylene adipate, polyhexyl adipate, polycarbonate, and polyurethane. The polyhydroxy fatty acid ester is selected from at least one of poly-β-hydroxybutyrate, polyhydroxyvalerate, polyhydroxyhexanoate, and polyhydroxyoctanoate.

9. The method according to claim 8, wherein, The ester-based plastics also include ester additives, including phthalate diesters.

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