Method for efficiently depolymerizing polyester at room temperature and normal pressure and application thereof

Abstract

The invention discloses a high-efficiency polyester depolymerization method at room temperature and normal pressure, which does not need a metal-based Lewis acid catalyst, and realizes high-efficiency depolymerization-closed-loop recovery (recovery of monomer carboxylic acid compounds and alcohol compounds) of various polyesters and different depolymerization recovery modes-appreciation conversion (hydrolysis, methanol hydrolysis and glycolysis) of the same polyester at room temperature and normal pressure. And carrying out thiolysis, ammonia / aminolysis and asymmetric amine alcoholysis). The method includes a pre-activation step that increases the ester carbonyl reactivity in the polyester. The efficient polyester depolymerization recovery rate is gt; the method can be applied to closed-loop recovery of various polyester plastic wastes, the polyester plastic wastes are efficiently depolymerized into monomers, the monomers can be re-polymerized into high-performance polyester plastics, regeneration cycle of the plastic wastes is realized, and the various polyester plastic wastes are converted into high-added-value chemicals; the method is lower in energy consumption, free of metal-based pollution, higher in efficiency and wider in range.

Description

Technical Field

[0001] The invention belongs to the technical field of polyesters, and in particular relates to a method for efficiently depolymerizing polyester at room temperature and pressure and application thereof. Background Art

[0002] Polyester is the largest plastic produced in the world today, second only to polyolefins, mainly including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), polybutylene terephthalate-adipate-butylene terephthalate (PBAT), polybutylene succinate (PBS), polylactic acid (PLA). Polyester has the advantages of low permeability, low weight, and high stain resistance. [2] , widely used in textiles (fibers, carpets, clothing), packaging (disposable beverage bottles, films), materials (boards, sheets) and building materials. [3] Despite strong plastic recycling programs in many countries around the world, single-use plastics dominate plastic use, microplastics are prevalent on land, and plastic accumulation rates in the oceans are high. [4,5] Polyethylene terephthalate (PET) is the world's largest polyester with the largest production and usage, with an annual output of more than 2600 million tons. [1] , is also the most recycled plastic among polyester plastics, but no country in the world has a PET recycling rate of more than 60%, and most countries have an average recycling rate of 30%. The reason is that PET recycling mainly uses thermomechanical technology, and only the purest and cleanest sorted waste plastics are re-melted and reprocessed. In general, less than 15% of PET bottles find a second life, usually in low-load virgin materials or fibers. [3,6] .

[0003] Currently, most industrial polyester recycling technologies rely mainly on mechanical methods for recycling, which is low-cost, simple to operate, and has the potential for large-scale application. However, due to the breakage of molecular chains during the remelting process and the presence of contaminants (such as other plastics, adhesives, and debris) during the recycling process, the optical, thermal, and mechanical properties of the recycled polymer are poor compared to the original polyester, and can only be used for downgrading. Although mechanical recycling extends the service life of polyester waste plastics, it cannot effectively degrade waste plastics. Although mechanical methods for recycling polyester have found industrial uses, people are working to develop more effective methods for chemically recycling polyester. [7]Unlike mechanical recycling, chemical recycling usually focuses on converting polyester into its monomeric acid compounds and their derivatives and alcohol compounds, such as terephthalic acid and ethylene glycol, dimethyl terephthalate and ethylene glycol, or dihydroxy (2-ethyl) terephthalate (BHET). Chemical recycling / upcycling methods can both produce high-value-added chemicals from plastic waste and regenerate monomers for the circular economy. Importantly, chemical recycling can effectively degrade polyester waste plastics that cannot be recycled through thermo-mechanical recycling.

[0004] Polyester is a highly symmetrical saturated linear polymer containing polar ester groups. The polymerization reaction brings good crystallization properties and excellent resistance to organic solvents, while also reducing the reactivity of the ester group in polyester plastics. At present, most industrial chemical recycling of polyester is mainly achieved through the reaction of nucleophilic reagents and ester carbonyl groups. It can generally be divided into hydrolysis, methanolysis [8] , glycolysis [9] , thiolysis, asymmetric amine / alcoholysis, ammonia / aminelysis

[10] . At room temperature and pressure, it is extremely difficult to depolymerize polyester. High temperature, Lewis catalyst and base are usually required to improve the depolymerization efficiency of ester carbonyl and nucleophilic reagent. High temperature is conducive to improving the reactivity of ester carbonyl and the solubility of polyester in organic solvents or water. At the same time, high temperature (80℃-220℃) is also conducive to the transformation of polyester from glassy state to highly elastic state, which is conducive to the separation and purification of products. But inevitably, high temperature will consume a lot of energy. Base is used to enhance the nucleophilicity of nucleophilic reagent. Commonly used bases include sodium / potassium hydroxide, potassium carbonate, potassium acetate, potassium phosphate, potassium / sodium alcohol and 1,5,7-Triazabicyclo[4.4.0]dec-5-ene(TBD). Lewis acid is used to improve the reactivity of ester carbonyl. Commonly used Lewis acid includes metal acetate, oxide, hydroxide, carbonate, sulfate and halide. The ones with excellent catalytic performance are usually composed of transition metal zinc and manganese. These metal-based catalysts are inevitably not so environmentally friendly, which will cause the metal elements to flow and remain in the soil, water and atmosphere, and ultimately harm the environment and humans.

[0005] There are many disadvantages in the existing technology. For example, the polyester recycled by the existing mechanical recycling technology has poor optical, thermal and mechanical properties compared with the original polyester due to the breakage of the molecular chain during the remelting process and the presence of pollutants (such as other plastics, adhesives and debris) during the recycling process. The recycled polymer can only be used for degradation. Although mechanical recycling prolongs the service life of polyester waste plastics, it cannot effectively degrade waste plastics. For example, the existing chemical recycling technology often requires high temperature to increase the reactivity of ester carbonyl and the solubility of polyester in organic solvents or water. At the same time, high temperature (80℃-220℃) is also conducive to the transformation of polyester from glassy state to highly elastic state, which is conducive to the separation and purification of products. But inevitably, a lot of energy will be consumed at high temperature. For example, the existing chemical recycling technology often requires Lewis acid catalysts to increase the reactivity of ester carbonyl. Commonly used Lewis acids include metal acetates, oxides, hydroxides, carbonates, sulfates and halides. Those with excellent catalytic performance are usually composed of transition metals zinc and manganese. These catalysts, which are mainly based on metals, are inevitably not so environmentally friendly, causing metal elements to flow and remain in the soil, water and atmosphere, ultimately harming the environment and humans. For example, existing chemical recycling technologies focus on developing efficient catalysts and more stringent and harsh conditions to improve the depolymerization efficiency of PET. Efficient catalysts are often not so cheap, and metal-based catalysts also pollute the environment. Strict and harsh reaction conditions require a lot of energy and sophisticated instruments and equipment, and require a lot of upfront costs, which limits its industrial application. For example, the efficiency of existing chemical recycling technologies in depolymerizing and recycling polyester plastics under room temperature without metal-based Lewis acid catalysts is extremely low, and it is impossible to achieve efficient depolymerization and recycling of polyester plastics under room temperature and atmospheric pressure without metal-based Lewis acid catalysis. For example, existing chemical recycling technologies are mainly focused on alkaline hydrolysis and alcoholysis (methanolysis and glycolysis) of PET bottles. There are few recycling strategies for PET (resins, plates, sheets, films, fibers and other types of real plastics) and other polyester types. The reason is that a slight change in the polymer monomer structure will cause a huge change in the physical properties of the polymer, which requires the use of different catalytic systems to achieve the degradation of different polyesters, resulting in no universal strategy to achieve efficient depolymerization and recycling of polyesters. In the prior art, polyester degradation is mainly based on alkaline hydrolysis, methanolysis and glycolysis of PET, and there are few reports on other types of polyester.

[0006] Therefore, it is particularly necessary to develop a low-energy, metal-free Lewis acid-catalyzed efficient depolymerization of polyester, which is conducive to the efficient recycling of polyester and can provide a general and feasible strategy for the efficient depolymerization of other polyester plastics. Summary of the invention

[0007] In order to solve the deficiencies in the prior art, the present invention aims to propose a method for efficient depolymerization of polyester and its application, including proposing to develop a method for efficient depolymerization of polyester at room temperature and normal pressure, avoiding the use of excessively high temperature to cause a large amount of energy loss; developing a method for efficient depolymerization of polyester catalyzed by metal-free Lewis acid, avoiding the use of metal to pollute the environment; developing a simple and universal method to achieve efficient depolymerization and recovery of different product types of resins and real plastics of the same polyester; developing a simple and universal method to achieve different depolymerization and recovery methods for the same polyester (including but not limited to hydrolysis, methanolysis, glycolysis, thiollysis, ammonia / aminelysis, asymmetric amine alcoholysis); developing a simple and universal strategy to achieve efficient depolymerization and recovery of a variety of polyesters, scaling up the reaction scale from milligram to kilogram to achieve efficient depolymerization and recovery of kilogram-level polyester under mild conditions, and exploring its industrial application.

[0008] The present invention proposes a method for efficient depolymerization of polyester at room temperature and normal pressure, which is carried out at room temperature and normal pressure without metal-based Lewis acid catalysis, and realizes different depolymerization recovery modes - value-added conversion of the same polyester and efficient depolymerization - closed-loop recovery of multiple polyesters; the method comprises: step 1. preactivation step: the polyester is dissolved in a solvent with good solubility for the polyester, and preactivated to form a polyester-solvent complex.

[0009] The method further comprises step 2: the polyester-solvent complex is subjected to hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis under the catalysis of metal-free Lewis acid at room temperature and atmospheric pressure.

[0010] The “solvent having good solubility for the polyester” includes but is not limited to fluorine-containing solvents and mixed solvents of fluorine-containing solvents and other solvents.

[0011] The polyester resin and real plastic include but are not limited to PET resin, packaging bottles, plates, sheets, films, fibers, etc.

[0012] Among them, the various polyesters include but are not limited to polyester PET (polyethylene terephthalate), PTT (polypropylene terephthalate), PBT (polybutylene terephthalate), PEN (polyethylene naphthalate), PBAT (polybutylene terephthalate-adipate-terephthalate), PBS (polybutylene succinate), PLA (polylactic acid) and the like.

[0013] The polyester efficient depolymerization method proposed by the present invention is carried out at room temperature and mild conditions without metal-based Lewis acid catalysis, and realizes efficient depolymerization and recovery of the same polyester and / or multiple polyesters in a universal method.

[0014] The polyester efficient depolymerization method of the present invention comprises a preactivation step, that is, the reaction activity of the ester carbonyl group in the polyester is improved by preactivation, so that the polyester can be more easily hydrolyzed, methanolyzed, glycolyzed, thiolyzed, ammonia / aminelyzed, and asymmetric amine alcoholyzed under the catalysis of metal-free Lewis acid at room temperature and normal pressure.

[0015] In the present invention, the efficient depolymerization-closed loop recovery of various polyesters includes the recovery of monomer carboxylic acid compounds and alcohol compounds.

[0016] In a specific embodiment, the pre-activation step is: dissolving the polyester by selecting a solvent that has good solubility for the polyester, and after the polyester is completely dissolved in the solvent, the solvent and the polyester form a polyester-solvent complex. The ester carbonyl reaction activity in the polyester-solvent complex is enhanced.

[0017] Specifically, the pre-activation step is: firstly, completely dissolving the polyester in a solvent having good solubility for the polyester, and after the polyester is completely dissolved in the solvent, the solvent and the polyester form a polyester-solvent complex.

[0018] Specifically, the polyester efficient depolymerization method of the present invention comprises the following steps:

[0019] 1. Pre-activation of polyester and fluorine-containing solvent or mixed solvent of fluorine-containing solvent and other solvent to form polyester-solvent complex.

[0020] 2. The polyester-solvent complex undergoes hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis under the catalysis of metal-free Lewis acid at room temperature and atmospheric pressure.

[0021] In a specific embodiment, the solvent having good solubility for the polyester is a fluorine-containing solvent such as trifluoroacetic acid TFA, trifluoromethanesulfonic acid, pentafluoropropionic acid, and a mixed solvent of a fluorine-containing solvent and other solvents.

[0022] More preferably, the solvent having good solubility for the polyester is TFA.

[0023] The polyester efficient depolymerization recovery rate of the method of the present invention is >95%, preferably >97%, and more preferably >99%.

[0024] The present invention also provides products prepared according to the polyester efficient depolymerization method, including but not limited to hydrolysis products, methanolysis products, glycolysis products, thiolysis products, asymmetric amine alcoholysis products, ammonolysis products, and amination products of different polyesters.

[0025] The present invention also proposes an application, that is, the application of different polyester products obtained by the polyester efficient depolymerization method. The application includes the application of hydrolysis products of different polyesters, including but not limited to carboxylic acid compounds and alcohol compounds, in the recycling of polyester plastics; the application of methanolysis and glycolysis products of different polyesters in re-synthesizing polyesters with superior performance and as organic synthesis intermediates for synthesizing high value-added chemicals; the application of thiolysis products of different polyesters as organic synthesis intermediates for synthesizing high value-added chemicals; the application of asymmetric amine alcoholysis products of different polyesters in synthesizing high value-added asymmetric polyester amine alcoholysis derivatives; the application of aminolysis and aminolysis products of different polyesters in re-synthesizing polyurethanes with superior performance and as organic synthesis intermediates for synthesizing high value-added chemicals.

[0026] The method for efficient depolymerization (closed-loop recovery and value-added conversion) of polyester at room temperature and normal pressure proposed by the present invention has a polyester efficient depolymerization recovery rate of >95%, and can be applied to the closed-loop recovery of various polyester plastic wastes, efficiently depolymerizing polyester plastic wastes into their monomers, which can be repolymerized into high-performance polyester plastics, thereby realizing the recycling of plastic wastes and converting various polyester plastic wastes into their high-value-added chemicals.

[0027] In the prior art, ester functional groups can achieve efficient hydrolysis, alcohol exchange and amine exchange reactions at room temperature without Lewis acid catalysts, but it is very difficult to depolymerize polyester without metal-based Lewis acid catalysts at room temperature. Unlike monomers, PET is a highly symmetrical saturated linear polymer with stronger intermolecular interactions, which reduces the solubility of polyester in water and organic solvents and the reactivity of ester carbonyl groups. These intermolecular interactions generated by high polymerization are the fundamental reason why polyester is difficult to depolymerize without metal-based Lewis acid catalysts at room temperature. The present invention innovatively proposes to first break or weaken the intermolecular interactions in high molecular weight polyesters by physical methods, which is equivalent to "pre-activating" high molecular weight polyesters. The "pre-activation" strategy increases the reactivity of ester carbonyl groups in polyesters, which makes it easier to achieve hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis of polyesters without metal-based Lewis acid catalysis at room temperature.

[0028] Preferably, the present invention first dissolves the polyester by selecting a solvent (for example, trifluoroacetic acid - TFA) with good solubility for the polyester. After the polyester is completely dissolved in TFA, the solvent TFA forms a complex with the polyester, and the reactivity of the ester carbonyl group in the polyester-TFA complex is improved. The polyester-TFA complex can achieve hydrolysis, methanolysis, glycolysis, thiollysis, ammonia / aminelysis, and asymmetric amine alcoholysis at room temperature without a metal-based Lewis acid catalyst.

[0029] Furthermore, in the method of the present invention, other fluorine-containing solvents and mixed solvents of fluorine-containing solvents and other solvents can be used as solvents to replace the solvent TFA to achieve "pre-activation" of the polyester.

[0030] The innovation of the present invention lies in that the fundamental problem of polyester being difficult to depolymerize under metal-free Lewis acid catalysis at room temperature and atmospheric pressure is solved through a pre-activation strategy, namely, the solubility of polyester in water and organic solvents and the reactivity of ester carbonyl groups are reduced due to the intermolecular forces generated by the high degree of polymerization reaction. The reactivity of ester carbonyl groups in polyesters is improved through the "pre-activation" strategy, and the hydrolysis, methanolysis, glycolysis, thiollysis, ammonia / aminelysis and asymmetric amine alcoholysis of various polyesters under metal-free Lewis acid catalysis at room temperature and atmospheric pressure are achieved.

[0031] The beneficial effects of the present invention include achieving efficient depolymerization and recovery of polyester under mild conditions at room temperature; achieving efficient depolymerization and recovery of polyester catalyzed by metal-free Lewis acid (recovery efficiency>95%); achieving efficient depolymerization and recovery of resins and real plastics of the same polyester; achieving different depolymerization and recovery methods (hydrolysis, methanolysis, glycolysis, thiollysis, ammonia / aminelysis, asymmetric amine alcoholysis) of the same polyester (taking PET as an example); achieving efficient depolymerization and recovery of multiple polyesters; achieving scale-up of the reaction from mg level to kilogram level to achieve efficient depolymerization and recovery of kilogram-level polyester under mild conditions, thus preparing for its industrial application.

[0032] Compared with the currently reported high-temperature metal-based Lewis acid-catalyzed polyester industrial depolymerization method, the method of the present invention has lower energy consumption, no metal-based pollution, higher efficiency and wider scope; it lays a foundation for the subsequent development of greener and more efficient polyester plastic waste recycling industrialization and high value-added productization of polyester plastic waste, can solve the pollution, recycling and conversion problems of polyester plastic waste, avoid polyester waste being abandoned in the environment and naturally degraded into microplastics to cause "white pollution", and ultimately endanger the environment and normal human life, and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 A summary diagram of closed-loop recycling and value-added conversion of polyester at room temperature and pressure

[0035] Figure 2 Infrared absorption spectra of PET and PET-TFA complex DETAILED DESCRIPTION

[0036] The invention is further described in detail with reference to the following specific embodiments and drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the contents specifically mentioned below, are common knowledge and common common sense in the art and are not particularly limited by the present invention.

[0037] The present invention proposes a method for efficient depolymerization of polyester at room temperature and pressure, which does not require a metal-based Lewis acid catalyst, and realizes efficient depolymerization-closed-loop recovery (monomer carboxylic acid compound and alcohol compound recovery) of various polyesters and different depolymerization recovery methods-value-added conversion (hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, asymmetric amine alcoholysis) of the same polyester at room temperature and pressure. The method includes a pre-activation step that improves the ester carbonyl reaction activity in the polyester. The polyester efficient depolymerization recovery rate of the present invention is greater than 95%, and can be applied to the closed-loop recovery of various polyester plastic wastes, efficiently depolymerizing polyester plastic wastes into their monomers, and the monomers can be repolymerized into high-performance polyester plastics, realizing the recycling of plastic wastes, and converting various polyester plastic wastes into their high-value-added chemicals; the method of the present invention has lower energy consumption, no metal-based pollution, higher efficiency, and wider range; it lays a foundation for the subsequent development of greener and more efficient polyester plastic waste recycling industrialization and high-value-added productization of polyester plastic wastes, and has broad application prospects.

[0038] In the present invention, Figure 1 As shown, the polyester is first cut and then dissolved in a fluorinated solvent to form a polyester-fluorinated solvent complex. The polyester-fluorinated solvent complex is directly subjected to hydrolysis, methanolysis, glycolysis, thiollysis, ammonia / aminelysis, and asymmetric amine alcoholysis to generate corresponding hydrolysis products, methanolysis products, glycolysis products, thiollysis products, ammonia / aminelysis products, and asymmetric amine alcoholysis products, which can be used to regenerate high-performance polyesters and polyurethanes and as an organic synthon to synthesize high-value-added chemicals.

[0039] Example 1

[0040] Example 1 - General steps for alkaline hydrolysis of polyester: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, then react the polyester-fluorine-containing solvent polymer with an aqueous hydroxide solution at room temperature and pressure for 6 hours to form carboxylate compounds and alcohol compounds, and acidify the carboxylate compounds to obtain carboxylic acid compounds.

[0041] The polyester alkaline water decomposition efficiency is >95%.

[0042]

[0043] A: PET resin was used as a template substrate to explore the degradation law of polyester. 50 mg of PET resin particles were stirred with TFA at room temperature for 36 hours (it took 36 hours for all the PET resin particles to dissolve in TFA). After the PET resin particles and TFA formed a PET-TFA complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 hours. More than 95% of the PET resin particles underwent alkaline hydrolysis, and the recovery rate of monomer terephthalic acid (TPA) was 98%.

[0044] B: Using PET resin as a template substrate to explore the degradation law of polyester, 50 mg of PET resin particles were stirred with CF3SO3H at room temperature for 20 h (it takes 20 h for all PET resin particles to dissolve in CF3SO3H). After the PET resin particles and CF3SO3H formed a PET-CF3SO3H complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 h. More than 95% of the PET resin particles were hydrolyzed with alkaline, and the recovery rate of monomer terephthalic acid (TPA) was 96%

[0045] C: 50 mg PET bottles were stirred with TFA at room temperature for 3 h (it takes 3 h for the PET bottles to be completely dissolved in TFA). After the PET bottles and TFA formed a PET-TFA complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 h. More than 95% of the PET bottles underwent alkaline hydrolysis, and the recovery rate of monomer terephthalic acid (TPA) was 98%.

[0046] D: 50 mg of PET polyester fiber and TFA were stirred at room temperature for 1 hour (it takes 1 hour for the PET polyester fiber to be completely dissolved in TFA). After the PET polyester fiber and TFA formed a PET-TFA complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 hours. More than 95% of the PET polyester fiber underwent alkaline hydrolysis, and the recovery rate of monomer terephthalic acid (TPA) was 95%.

[0047] E: 50 mg of PBT resin and TFA were stirred at room temperature for 48 h (it took 48 h for the PBT resin to be completely dissolved in TFA). After the PBT resin and TFA formed a PBT-TFA complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 h. More than 95% of the PBT resin underwent alkaline hydrolysis, and the recovery rate of monomer terephthalic acid (TPA) was 95%.

[0048] F: 50 mg of PEN resin and TFA were stirred at room temperature for 48 h (it took 48 h for the PEN resin to be completely dissolved in TFA). After the PEN resin and TFA formed a PEN-TFA complex, NaOH (aq.) was added and the reaction was continued at room temperature for 6 h. More than 95% of the PEN resin underwent alkaline hydrolysis. The recovery rate of monomer p-naphthalene dicarboxylic acid (TPA) was 96%.

[0049] Product Identification:

[0050] PET hydrolysis product terephthalic acid: white solid. 1 H NMR (400MHz, DMSO-d6), δ13.31 (s, 2H), 8.04 (s, 4H). 13 C NMR (101MHz, DMSO-d6) δ166.7, 134.5, 129.5. Ethylene glycol: colorless liquid. 1 H NMR (400MHz, DMSO-d6), δ4.66 (s, 2H), 3.40 (s, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 62.9.

[0051] PBT hydrolysis product terephthalic acid: white solid. 1 H NMR (400MHz, DMSO-d6), δ13.31 (s, 2H), 8.04 (s, 4H). 13 C NMR (101MHz, DMSO-d6) δ166.7, 134.5, 129.5. Butanediol: colorless liquid 1 H NMR (500MHz, D2O): δ3.72–3.68(m,4H),1.69–1.65(m,4H). 13 C NMR (126 MHz, D2O) δ 61.7, 28.0.

[0052] PEN hydrolysis product naphthalene dicarboxylic acid: white solid. 1 H NMR(500MHz, DMSO-d6), δ13.24(s,2H),8.66(s,2H),8.19,(d,J=8.5Hz,2H),8.04,(d,J=8.5Hz,2H), 13 C NMR (126MHz, DMSO-d6) δ167.2, 134.2, 130.2, 130.1, 129.7, 125, 9. Ethylene glycol: colorless liquid. 1 H NMR (400MHz, DMSO-d6), δ4.66 (s, 2H), 3.40 (s, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 62.9.

[0053] Example 2

[0054] Example 2 - General steps for the methanolysis of polyester: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, and then react the polyester-fluorine-containing solvent polymer with methanol at room temperature and atmospheric pressure without / without organic base activation for 6 hours to form carboxylic acid derivatives and alcohol compounds.

[0055]

[0056] A: 50 mg of PET resin particles were stirred with TFA at room temperature for 36 hours (it takes 36 hours for all PET resin particles to dissolve in TFA). After the PET resin particles and TFA form a PET-TFA complex, methanol and TBD were added, and the reaction was continued at room temperature for 6 hours. More than 60% of the PET resin particles underwent methanolysis.

[0057] B: 50 mg of PET resin powder was stirred with TFA at room temperature for 12 h (it took 12 h for all the PET resin powder to dissolve in TFA). After the PET resin powder and TFA formed a PET-TFA complex, methanol and TBD were added and the reaction was continued at room temperature for 6 h. More than 64% of the PET resin powder underwent methanolysis.

[0058] C: 50 mg of PET film was stirred with TFA at room temperature for 1 hour (it takes 1 hour for the PET film to be completely dissolved in TFA). After the PET film and TFA formed a PET-TFA complex, methanol and TBD were added and the reaction was continued at room temperature for 6 hours. More than 70% of the PET film underwent methanolysis.

[0059] D: 50 mg of PBT resin was stirred with TFA at room temperature for 48 h (it takes 48 h for the PBT resin to be completely dissolved in TFA). After the PBT resin and TFA formed a PBT-TFA complex, methanol and TBD were added and the reaction was continued at room temperature for 6 h. More than 50% of the PBT resin underwent methanolysis.

[0060] PET methanolysis product: white solid. 1 H NMR (400MHz, CDCl3), δ8.10 (s, 4H), 3.95 (s, 6H). 13 CNMR (101MHz,CDCl3)δ166.5,134.1,129.7,52.6. Ethylene glycol: colorless liquid. 1 H NMR (400MHz, DMSO-d6), δ4.66 (s, 2H), 3.40 (s, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 62.9.

[0061] PBT methanolysis product: white solid.1 H NMR (400MHz, CDCl3), δ8.10 (s, 4H), 3.95 (s, 6H). 13 CNMR (101MHz,CDCl3)δ166.5,134.1,129.7,52.6.Butanediol: colorless liquid 1 H NMR (500MHz, D2O): δ3.72–3.68(m,4H),1.69–1.65(m,4H). 13 C NMR (126 MHz, D2O) δ 61.7, 28.0.

[0062] Example 3

[0063] Example 3 - General steps for glycolysis of polyester: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, and then react the polyester-fluorine-containing solvent polymer with ethylene glycol at room temperature and atmospheric pressure in the absence of / organic base activation for 24 hours to form carboxylic acid derivatives and alcohol compounds.

[0064]

[0065] A: 50 mg of PET resin particles were stirred with TFA at room temperature for 36 hours (it takes 36 hours for all PET resin particles to dissolve in TFA). After the PET resin particles and TFA form a PET-TFA complex, ethylene glycol and TBD were added, and the reaction was continued at room temperature for 24 hours. More than 55% of the PET resin particles underwent glycolysis.

[0066] B: 50 mg of PET sheet and TFA were stirred at room temperature for 2 h (it took 2 h for the PET sheet to be completely dissolved in TFA). After the PET sheet and TFA formed a PET-TFA complex, ethylene glycol and TBD were added, and the reaction was continued at room temperature for 24 h. More than 60% of the PET sheet underwent glycolysis.

[0067] C: 50 mg of PET sheet was stirred with TFA at room temperature for 1 hour (it takes 1 hour for the PET sheet to be completely dissolved in TFA). After the PET sheet and TFA formed a PET-TFA complex, ethylene glycol and TBD were added, and the reaction was continued at room temperature for 24 hours. More than 64% of the PET sheet underwent glycolysis.

[0068] D: 50 mg of PBT resin was stirred with TFA at room temperature for 48 hours (it takes 48 hours for the PBT resin to be completely dissolved in TFA). After the PBT resin and TFA formed a PBT-TFA complex, ethylene glycol and TBD were added, and the reaction was continued at room temperature for 24 hours. More than 55% of the PBT resin underwent glycolysis.

[0069] PET glycolysis product: white solid. 1 H NMR (400MHz, DMSO-d6), δ8.12(s,4H),4.98(s,2H),4.35–4.29(m,4H),3.74–3.70(m,4H). 13 C NMR (101 MHz, DMSO-d6) δ 165.2, 133.8, 129.6, 67.1, 59.1. Ethylene glycol: colorless liquid. 1 H NMR (400MHz, DMSO-d6), δ4.66 (s, 2H), 3.40 (s, 4H). 13 CNMR (101 MHz, DMSO-d6) δ 62.9.

[0070] PBT glycolysis product: white solid. 1 H NMR (400MHz, DMSO-d6), δ8.12(s,4H),4.98(s,2H),4.35–4.29(m,4H),3.74–3.70(m,4H). 13 C NMR (101MHz, DMSO-d6) δ165.2, 133.8, 129.6, 67.1, 59.1. Butanediol: colorless liquid 1 H NMR (500MHz, D2O): δ3.72–3.68(m,4H),1.69–1.65(m,4H). 13 C NMR (126 MHz, D2O) δ 61.7, 28.0.

[0071] Example 4

[0072] Example 4 - General steps for polyester alcoholysis and thiolysis: The polyester resin and real plastic are completely dissolved in a fluorinated solvent, and the polyester and the fluorinated solvent form a polyester-fluorinated solvent polymer. Subsequently, the polyester-fluorinated solvent polymer is reacted with ethylene glycol at room temperature and atmospheric pressure in the absence of / inorganic base activation for 24 hours to form carboxylic acid derivatives and alcohol compounds.

[0073]

[0074] A: 50 mg of PET resin particles were stirred with TFA at room temperature for 36 hours (it took 36 hours for all PET resin particles to dissolve in TFA). After the PET resin particles and TFA formed a PET-TFA complex, n-butyl mercaptan and TBD were added, and the reaction was continued at room temperature for 24 hours. More than 90% of the PET resin particles underwent glycolysis.

[0075] B: 50 mg of PBT resin and TFA were stirred at room temperature for 48 hours (it took 48 hours for the PBT resin to be completely dissolved in TFA). After the PBT resin and TFA formed a PBT-TFA complex, n-butyl mercaptan and TBD were added, and the reaction was continued at room temperature for 24 hours. More than 85% of the PBT resin underwent glycolysis.

[0076] Example 5

[0077] Example 5 - General steps for aminolysis of polyester: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, and then react the polyester-fluorine-containing solvent polymer with ammonia water at room temperature and atmospheric pressure in the absence of / organic base activation for 24 hours to form carboxylic acid derivatives and alcohol compounds.

[0078]

[0079] A: 50 mg of PET resin particles were stirred with TFA at room temperature for 36 hours (it takes 36 hours for all PET resin particles to dissolve in TFA). After the PET resin particles and TFA form a PET-TFA complex, ammonia water was added and the reaction was continued at room temperature for 24 hours. More than 60% of the PET resin particles underwent aminolysis.

[0080] B: 50 mg of PET sheet and TFA were stirred at room temperature for 2 h (it takes 2 h for the PET sheet to be completely dissolved in TFA). After the PET sheet and TFA formed a PET-TFA complex, ammonia water was added and the reaction was continued at room temperature for 24 h. More than 65% of the PET sheet underwent ammonolysis.

[0081] C: 50 mg of PET sheet was stirred with TFA at room temperature for 1 hour (it takes 1 hour for the PET sheet to be completely dissolved in TFA). After the PET sheet and TFA formed a PET-TFA complex, ammonia water was added and the reaction was continued at room temperature for 24 hours. More than 69% of the PET sheet was ammonolyzed.

[0082] D: 50 mg of PBT resin and TFA were stirred at room temperature for 48 hours (it takes 48 hours for the PBT resin to be completely dissolved in TFA). After the PBT resin and TFA formed a PBT-TFA complex, ammonia water was added and the reaction was continued at room temperature for 24 hours. More than 60% of the PBT resin was aminolyzed.

[0083] PET ammoniolysis product: white solid. 1 H NMR (500MHz, DMSO-d6), δ8.07(s,2H),7.93(s,4H),7.49,(s,2H). 13C NMR (126MHz, DMSO-d6), δ167.3, 136, 6, 127.4. Ethylene glycol: colorless liquid. 1 H NMR (400MHz, DMSO-d6), δ4.66 (s, 2H), 3.40 (s, 4H). 13 C NMR (101 MHz, DMSO-d6) δ 62.9.

[0084] PBT ammoniolysis product: white solid. 1 H NMR (500MHz, DMSO-d6), δ8.07(s,2H),7.93(s,4H),7.49,(s,2H). 13 C NMR (126MHz, DMSO-d6), δ167.3, 136, 6, 127.4. Butanediol: colorless liquid 1 H NMR (500MHz, D2O): δ3.72–3.68(m,4H),1.69–1.65(m,4H). 13 C NMR (126 MHz, D2O) δ 61.7, 28.0.

[0085] Example 6

[0086] Example 6 - General steps for polyester decomposition: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, and then react the polyester-fluorine-containing solvent polymer with amines at room temperature and atmospheric pressure without / without organic base activation for 24 hours to form carboxylic acid derivatives and alcohol compounds.

[0087]

[0088] A: 50 mg of PET bottles were stirred with TFA at room temperature for 3 hours (it takes 3 hours for all PET bottles to dissolve in TFA). After the PET bottles and TFA form a PET-TFA complex, n-propylamine was added and the reaction was continued at room temperature for 24 hours. More than 95% of the PET bottles underwent n-propylamine hydrolysis.

[0089] B: 50 mg of PTT fiber and TFA were stirred at room temperature for 1 hour (it takes 1 hour for the PTT fiber to be completely dissolved in TFA). After the PTT fiber and TFA formed a PTT-TFA complex, n-propylamine was added and the reaction was continued at room temperature for 24 hours. More than 95% of the PET fiber underwent n-propylamine hydrolysis.

[0090] C: 50 mg of PBT polyester was stirred with TFA at room temperature for 48 hours (it takes 48 hours for the PBT polyester to be completely dissolved in TFA). After the PBT polyester and TFA formed a PBT-TFA complex, n-propylamine was added and the reaction was continued at room temperature for 24 hours. More than 95% of the PBT polyester was hydrolyzed by n-propylamine.

[0091] D: 50 mg of PET resin and TFA were stirred at room temperature for 36 hours (it took 36 hours for the PET resin to be completely dissolved in TFA). After the PET resin and TFA formed a PET-TFA complex, ethanolamine was added and the reaction was continued at room temperature for 24 hours. More than 95% of the PET resin underwent ethanolamine hydrolysis.

[0092] E: 50 mg of PET resin and TFA were stirred at room temperature for 36 hours (it takes 36 hours for the PET resin to be completely dissolved in TFA). After the PET resin and TFA formed a PET-TFA complex, ethylenediamine was added and the reaction was continued at room temperature for 24 hours. More than 95% of the PET resin underwent ethylenediamine decomposition.

[0093] PET, PTT, PBT, n-propylamine decomposition product: white solid. 1 H NMR (500MHz, DMSO-d6), δ8.55(t,J=5.0Hz,2H),7.90(s,4H),3.25-3.20(m,4H),1.57–1.51(m,4H),0.89(t,J=7.0Hz,6H). 13 CNMR (126MHz, DMSO-d6), δ165.5,136.8,127.0,41.0,22.4,11.5.

[0094] PET ethanolamine hydrolysis products: 1 H NMR (500MHz, DMSO-d6), δ8.54(t,J=5.5Hz,2H),7.91(s,4H),4.74(s,2H),3.52(t,J=6.0Hz,4H),3.34(t,J=5.5Hz,4H). 13 C NMR (126MHz, DMSO-d6), δ165.7, 136.7, 127.1, 59.7, 42.3.

[0095] PET ethylenediamine hydrolysis products: 1 H NMR (400MHz, D2O), δ7.92 (s, 2H), 3.76 (t, J = 6.0Hz, 4H), 3.30 (t, J = 6.0Hz, 4H). 13 C NMR (101MHz, D2O), δ170.7,136.4,127.6,39.3,37.5.

[0096] Example 7

[0097] Example 7 - General steps for asymmetric amine alcoholysis of polyester: completely dissolve the polyester resin and real plastic in a fluorine-containing solvent, wait for the polyester and the fluorine-containing solvent to form a polyester-fluorine-containing solvent polymer, and then react the polyester-fluorine-containing solvent polymer with amines and alcohols at room temperature and atmospheric pressure in the absence of / organic base activation for 24 hours to form carboxylic acid derivatives and alcohol compounds.

[0098]

[0099] A: 50 mg of PTT fiber was stirred with TFA at room temperature for 1 hour (it takes 1 hour for the PTT fiber to be completely dissolved in TFA). After the PTT fiber and TFA formed a PTT-TFA complex, n-propylamine and methanol were added, and the reaction was continued at room temperature for 24 hours. More than 90% of the PET fiber underwent asymmetric n-propylamine methanolysis.

[0100] B: 50 mg of PBT polyester was stirred with TFA at room temperature for 48 hours (it takes 48 hours for the PBT polyester to be completely dissolved in TFA). After the PBT polyester and TFA formed a PBT-TFA complex, n-propylamine and methanol were added, and the reaction was continued at room temperature for 24 hours. More than 85% of the PBT polyester underwent asymmetric n-propylamine methanolysis.

[0101] C: 50 mg PET resin was stirred with TFA at room temperature for 36 hours (36 hours was required for the PET resin to be completely dissolved in TFA). After the PET resin and TFA formed a PET-TFA complex, n-propylamine and methanol were added and the reaction was continued at room temperature for 24 hours. More than 95% of the PET resin underwent asymmetric n-propylamine methanolysis.

[0102] PET, PTT, PBT, asymmetric n-propylamine methanolysis product: white solid. 1 H NMR (400MHz, DMSO-d6).δ8.65(s,1H),8.03(d,J=8.4Hz,2H),7.95(d,J=8.4H z,2H),3.88(s,3H),3,26–3.19(m,2H),1.59–1.49(m,2H),0.89(t,J=7.6Hz). 13 C NMR (101MHz, DMSO-d6).δ165.7,165.3,138.8,131.6,129.1,127.5,52.4,42.1,22.3,11.5.

[0103] Effect verification example

[0104] The various physical properties of PET-TFA complexes were investigated using PET polyester powder as a template substrate. PET was dissolved in TFA to form a PET-TFA complex. Compared with the original PET, the absorption peak of the carbonyl group in the infrared-IR of the newly formed PET-TFA complex increased from 1712.86 cm -1 Displacement to 1714.79cm -1 The blue-shifted absorption peak of the carbonyl group proves that the reactivity of the ester carbonyl group is enhanced, making it easier to react with nucleophiles at room temperature and pressure, such as Figure 2 shown.

[0105] The present invention innovatively proposes a method of "pre-activating" polyester to solve the fundamental problem that polyester is difficult to depolymerize under metal-free Lewis acid catalyst at room temperature, that is, the solubility of polyester in water and organic solvents and the reactivity of ester carbonyl groups caused by the intermolecular forces generated by the high degree of polymerization are reduced. The reactivity of ester carbonyl groups in polyesters is improved through the "pre-activation" strategy, and the hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis of various polyester resins and real plastics under metal-free Lewis acid catalysis at room temperature and atmospheric pressure are realized. In addition, the reaction scale can be enlarged to kilogram level. After the polyester hydrolysis scale is enlarged to kilogram level, it is more beneficial to the reaction. There is no inhibition of degradation reaction by amplification effect. The efficiency of kilogram-level recovery of carboxylic acid compounds reaches 97%, and another monomer alcohol compound can also be effectively recovered, which can achieve efficient recovery of two monomers of polyester.

[0106] The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention and are protected by the attached claims.

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[0116]

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Claims

1. A method for efficiently depolymerizing polyester at room temperature and pressure, characterized in that: The method is carried out at room temperature and normal pressure, without metal-based Lewis acid catalysis, and realizes different depolymerization recovery modes of the same polyester - value-added conversion and efficient depolymerization - closed-loop recovery of multiple polyesters; The method comprises: Step 1, pre-activation step: the polyester is dissolved in a solvent having good solubility for the polyester, and pre-activated to form a polyester-solvent complex; Step 2: The polyester-solvent complex is subjected to hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis under the catalysis of metal-free Lewis acid at room temperature and atmospheric pressure.

2. The polyester efficient depolymerization method according to claim 1, characterized in that: In the method, the polyester includes resins of different polyesters and real plastics.

3. The polyester efficient depolymerization method according to claim 1, characterized in that: The different depolymerization recovery methods of the same polyester - value-added conversion include hydrolysis, methanolysis, glycolysis, thiolysis, ammonia / aminelysis, and asymmetric amine alcoholysis of polyester; The highly efficient depolymerization-closed-loop recovery of the various polyesters includes the recovery of monomeric carboxylic acid compounds and alcohol compounds.

4. The polyester efficient depolymerization method according to claim 1, characterized in that: The solvent is a fluorine-containing solvent or a mixed solvent of a fluorine-containing solvent and other solvents.

5. The polyester efficient depolymerization method according to claim 1, characterized in that: The polyester has an efficient depolymerization recovery rate of >95%.

6. The product obtained by the polyester efficient depolymerization method according to any one of claims 1 to 5, characterized in that: The products include hydrolysis products, methanolysis products, glycolysis products, thiolysis products, asymmetric amine alcoholysis products, aminolysis products, and aminolysis products of different polyesters.

7. The use of the product obtained by the polyester efficient depolymerization method as claimed in claim 6, characterized in that: The hydrolysis products of different polyesters can be applied to the recycling of polyester plastics; the hydrolysis products include carboxylic acid compounds and alcohol compounds; The methanolysis and glycolysis products of the different polyesters are used to synthesize polyesters again and as organic synthesis intermediates to synthesize high value-added chemicals; The asymmetric amine alcoholysis products of different polyesters can be used to synthesize high value-added asymmetric polyester amine alcoholysis derivatives; The thiolysis products of the different polyesters are used as organic synthesis intermediates to synthesize high value-added chemicals; and / or, The aminolysis and aminolysis products of the different polyesters can be used to re-synthesize polyurethane and serve as organic synthesis intermediates to synthesize high value-added chemicals.

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