Method for recovering a polymer material by alcoholysis

Abstract

The application provides a method for recovering high molecular material by alcoholysis, which comprises the following steps: alcoholysis of high molecular material and methanol under the action of a catalyst to obtain small molecular organic compounds; wherein the high molecular material is polyester material and / or polycarbonate material; and the catalyst is carbon dioxide gas. The method of the application uses carbon dioxide gas as the catalyst, which is cheap, easy to obtain, non-toxic and harmless, and can effectively catalyze the degradation of polyester material and polycarbonate material, so that the high molecular material is 100% alcoholized into small molecular organic compounds. In the method of the application, carbon dioxide gas is discharged after alcoholysis, and there is no problem of catalyst residue.

Description

Technical Field

[0001] This invention relates to the field of polymer material recycling, and in particular to a method for the alcoholysis recycling of polymer materials. Background Technology

[0002] Polyesters and polycarbonates are common polymer materials in people's daily lives and production, and are widely used in packaging manufacturing, biomedicine and other fields. For example: polylactic acid (PLA): a polymer polyester material; polyethylene terephthalate (PET): a polymer polyester material; polybisphenol A carbonate (BPAPC): a polymer polycarbonate material.

[0003] With global population growth and social progress, the demand for these polymer materials is increasing daily. However, the disposal of waste polymer materials poses a challenge to global sustainable development. Methods such as landfilling and incineration cause significant pollution to the ecosystem. Therefore, new methods for handling waste polymer materials are needed.

[0004] Compared to traditional methods such as landfilling and incineration, chemically degrading polymeric materials into smaller organic molecules is an effective approach. For example, polylactic acid (PLA) undergoes alcoholysis in methanol to produce lactate esters; polyethylene terephthalate (PET) undergoes alcoholysis in methanol to produce dimethyl terephthalate and ethylene glycol; and polybisphenol A carbonate (BPAPC) undergoes alcoholysis in methanol to produce bisphenol A and dimethyl carbonate. These smaller organic molecules have higher value than waste polymeric materials, and they can be reused as raw materials to synthesize other organic compounds or polymeric materials. Therefore, the alcoholysis of polyesters and polycarbonates is not only significant for environmental protection and reducing waste pollution of the ecosystem, but the degraded small organic molecules also have higher economic value.

[0005] Although some literature reports catalytic alcoholysis methods for polyester and polycarbonate materials, the catalysts used in these methods are all solid or liquid catalytic systems, and some methods also require the addition of external solvents. The applicant's research group has also reported the use of Lewis acid-base pairs, such as sodium ascorbate, as catalysts for the alcoholysis recovery of polylactic acid (GreenChemistry 2022, 24, 9282-9289). While these systems provide some new pathways for the recovery of polymer materials, catalyst preparation, catalyst activity, post-reaction catalyst separation, and catalyst residues in the products are all issues that researchers need to consider. Summary of the Invention

[0006] In view of this, the present invention provides a method for the alcoholysis and recovery of polymer materials. The method of the present invention can not only effectively degrade polyester and polycarbonate materials, but also avoids the problem of catalyst residue.

[0007] This invention provides a method for the alcoholysis and recovery of polymer materials, comprising the following steps:

[0008] Polymer materials and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain small molecule organic compounds;

[0009] in,

[0010] The polymer material is a polyester material and / or a polycarbonate material;

[0011] The catalyst is carbon dioxide gas.

[0012] Preferably, the polyester material comprises polylactic acid and / or polyethylene terephthalate;

[0013] The polycarbonate material includes poly(bisphenol A carbonate).

[0014] Preferably, the alcoholysis reaction is carried out at a temperature of 140–200°C for a time of 4–12 hours.

[0015] Preferably, it includes the following steps:

[0016] Polylactic acid and methanol are subjected to an alcoholysis reaction in the presence of a catalyst to obtain methyl lactate;

[0017] or

[0018] Poly(ethylene terephthalate) and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain dimethyl terephthalate and ethylene glycol;

[0019] or

[0020] Poly(bisphenol A carbonate) and methanol were subjected to alcoholysis reaction in the presence of a catalyst to obtain bisphenol A and dimethyl carbonate.

[0021] Preferably, the relationship between the amount of polymeric material and methanol is as follows:

[0022] The number of moles of methanol is greater than the number of moles of ester / carbonate bonds in the polymer material.

[0023] Preferably, it includes the following steps:

[0024] Polymer materials and methanol are added to a reaction vessel, which is then sealed. Carbon dioxide gas is then introduced into the reaction vessel. The reaction vessel is heated to carry out an alcoholysis reaction. After the reaction is completed, the temperature is lowered and the carbon dioxide gas in the reaction vessel is released to obtain small molecule organic compounds.

[0025] Preferably, when carbon dioxide gas is introduced into the reactor, the pressure of the carbon dioxide gas inside the reactor is controlled to be 1-4 MPa.

[0026] Preferably, the molar ratio of ester bonds to methanol in the polyester material is 1:25;

[0027] The polycarbonate material has a carbon bond to methanol molar ratio of 1:50.

[0028] Preferably, the reaction vessel is a stainless steel reaction vessel with a volume of 25 mL.

[0029] The method for recovering polymer materials by alcoholysis provided by this invention uses carbon dioxide gas as a catalyst, which is inexpensive, readily available, non-toxic, and harmless. It can effectively catalyze the degradation of polyester and polycarbonate materials, resulting in 100% alcoholysis of these polymers into small-molecule organic compounds. Furthermore, this method requires no external solvents besides the alcohol feedstock, effectively reducing costs and improving environmental friendliness. Moreover, in this method, carbon dioxide gas is discharged after alcoholysis, eliminating any catalyst residue (catalyst residue would lead to impure products, requiring post-processing to separate the catalyst from the organic products; however, improper post-processing would not affect product purity). It should be noted that carbon dioxide in this invention acts as a catalyst; carbon dioxide itself does not convert into the products. This is fundamentally different from reactions where carbon dioxide is used as a reactant to convert into compounds.

[0030] Experimental results show that the method of the present invention can effectively alcoholyze polyester and polycarbonate materials, with an alcoholysis conversion rate of 100%. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0032] Figure 1 This is a characterization diagram of the process of polylactic acid being alcoholyzed in methanol to produce methyl lactate in Example 1;

[0033] Figure 2 This is a characterization diagram of the process of converting poly(bisphenol A carbonate) to bisphenol A via alcoholysis in Example 7. Detailed Implementation

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0035] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0036] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0037] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0038] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it indicates that the units for the left and right endpoints are the same. For example, 1-4MPa means that the units for the left endpoint "1" and the right endpoint "4" are both MPa.

[0039] This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0040] This invention provides a method for the alcoholysis and recovery of polymer materials, comprising the following steps:

[0041] Polymer materials and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain small molecule organic compounds;

[0042] in,

[0043] The polymer material is a polyester material and / or a polycarbonate material;

[0044] The catalyst is carbon dioxide gas.

[0045] In this invention, the polymeric material is a polyester material and / or a polycarbonate material. Preferably, the polyester material includes polylactic acid and / or polyethylene terephthalate, but is not limited thereto. Preferably, the polycarbonate material includes poly(bisphenol A carbonate), but is not limited thereto. In this invention, the aforementioned polymeric material can be a commercially available resin, a polymeric material product, or a waste polymeric material product. Specifically: for polylactic acid, it can be a commercially available resin (not limited to a specific resin type), or an article made of polylactic acid material (e.g., 3D printing materials or fast food beverage cup lids, but not limited thereto). For polyethylene terephthalate, it can be a commercially available resin (not limited to a specific resin type), or an article made of polyethylene terephthalate material (e.g., mineral water bottles or supermarket fruit packaging boxes, but not limited thereto). The poly(bisphenol A carbonate) can be a commercially available resin (not limited to any particular resin type) or an article made of poly(bisphenol A carbonate) material (such as the base of a DVD or the lens of goggles, but not limited to these). For polymeric material articles or waste polymeric material articles, it is preferable to wash, dry, and cut them into pieces beforehand before adding them to the system for reaction.

[0046] In this invention, the source of methanol is not particularly limited; it can be a commercially available product.

[0047] In this invention, the preferred ratio of the polymer material to methanol is: the molar number of methanol > the molar number of ester bonds / carbonate bonds in the polymer material. For polyester materials, the preferred molar ratio of ester bonds to methanol is 1:25. For polycarbonate materials, the preferred molar ratio of carbonate bonds (i.e., CO3 groups) to methanol is 1:50. The ratio of the above two types of polymer materials (polyester materials and polycarbonate materials) to methanol is not limited to the above values, as long as the molar number of methanol > the molar number of ester bonds / carbonate bonds in the polymer material.

[0048] In this invention, the catalyst is carbon dioxide gas. During the reaction process, the pressure of the carbon dioxide gas is preferably controlled to be 1–4 MPa, specifically 1 MPa, 2 MPa, 3 MPa, or 4 MPa.

[0049] In this invention, the preferred temperature for the alcoholysis reaction is 140–200°C, specifically 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, or 200°C. The preferred reaction time is 4–12 hours, specifically 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, or 12 hours. Through the above alcoholysis reaction, the polymer material is degraded into small-molecule organic compounds.

[0050] In this invention, different small-molecule organic compounds can be obtained from different polymer materials after alcoholysis.

[0051] Specifically, the correspondence between raw materials and products is as follows:

[0052] Polylactic acid and methanol are subjected to an alcoholysis reaction in the presence of a catalyst to obtain methyl lactate;

[0053] or

[0054] Poly(ethylene terephthalate) and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain dimethyl terephthalate and ethylene glycol;

[0055] or

[0056] Poly(bisphenol A carbonate) and methanol were subjected to alcoholysis reaction in the presence of a catalyst to obtain bisphenol A and dimethyl carbonate.

[0057] The reaction routes for the three reactions described above are as follows:

[0058]

[0059] Specifically, for the first reaction (i.e., the alcoholysis reaction of polylactic acid with methanol), the reaction temperature is more preferably 140°C. For the second reaction (i.e., the alcoholysis reaction of polyethylene terephthalate with methanol), the reaction temperature is more preferably 200°C. For the third reaction (i.e., the alcoholysis reaction of poly(bisphenol A carbonate) with methanol), the reaction temperature is more preferably 140°C.

[0060] In this invention, the method described above preferably includes the following steps: adding polymer materials and methanol into a reaction vessel, then sealing the reaction vessel, and then introducing carbon dioxide gas into the reaction vessel; heating the reaction vessel to carry out an alcoholysis reaction, and after the reaction is completed, cooling down and releasing the carbon dioxide gas in the reaction vessel to obtain small molecule organic compounds.

[0061] in,

[0062] The reactor is preferably a stainless steel reactor, more preferably a 25 mL stainless steel reactor. After adding the reactants, the reactor is sealed, and then carbon dioxide gas is introduced into the reactor. The pressure of the carbon dioxide gas is preferably 1–4 MPa, specifically 1 MPa, 2 MPa, 3 MPa, or 4 MPa. After introducing the carbon dioxide gas, the reactor is heated to allow the reaction system to undergo an alcoholysis reaction. The reaction conditions are the same as described above and will not be repeated here. After the reaction is complete, the temperature is lowered, preferably to room temperature. Then, the carbon dioxide gas in the reactor is slowly released, thereby obtaining small molecule organic compounds.

[0063] The method for recovering polymer materials by alcoholysis provided by this invention uses carbon dioxide gas as a catalyst, which is inexpensive, readily available, non-toxic, and harmless. It can effectively catalyze the degradation of polyester and polycarbonate materials, resulting in 100% alcoholysis of these polymers into small-molecule organic compounds. Furthermore, this method requires no external solvents besides the alcohol feedstock, effectively reducing costs and improving environmental friendliness. Moreover, in this method, carbon dioxide gas is discharged after alcoholysis, eliminating any catalyst residue (catalyst residue would lead to impure products, requiring post-processing to separate the catalyst from the organic products; however, improper post-processing would not affect product purity). It should be noted that carbon dioxide in this invention acts as a catalyst; carbon dioxide itself does not convert into the products. This is fundamentally different from reactions where carbon dioxide is used as a reactant to convert into compounds.

[0064] Experimental results show that the method of the present invention can effectively alcoholyze polyester and polycarbonate materials, with an alcoholysis conversion rate of 100%.

[0065] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0066] Example 1

[0067] Polylactic acid resin (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (1 MPa) was then introduced into the reaction vessel. The reaction vessel was heated at 140°C on a heater for a certain period of time for alcoholysis. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the reaction vessel, yielding a small molecule organic compound.

[0068] After opening the reactor, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polylactic acid to methyl lactate in this solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0069] After 4 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 27%.

[0070] After 6 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 89%.

[0071] After 8 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 100%.

[0072] The above results are as follows Figure 1 As shown, Figure 1Four 1H NMR spectra (300MHz, deuterated chloroform as solvent, 4.0–5.5ppm range) characterized the alcoholysis of polylactic acid (PLA) in methanol to produce methyl lactate. The red hydrogen peaks represent the characteristic peaks of the reactants and products. Detections at 4 and 6 hours of reaction revealed that PLA could degrade into a methyl lactate "dimer." This dimer was completely converted into methyl lactate over time.

[0073] Example 2

[0074] The 3D printing material made of polylactic acid was washed with distilled water, dried, and cut into pieces. This sample (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (1 MPa) was then introduced into the reaction vessel. The reaction vessel was heated at 140°C on a heater for a certain time to undergo alcoholysis. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding small molecule organic compounds.

[0075] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polylactic acid to methyl lactate in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0076] After 6 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 55%.

[0077] After 12 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 100%.

[0078] Example 3

[0079] The polylactic acid (PLA) beverage cup lids used in fast food restaurants were washed with distilled water, dried, and cut into pieces with scissors. The sample (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (1 MPa) was then introduced into the reaction vessel. The reaction vessel was heated at 140°C on a heater for a certain time to undergo alcoholysis. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding small-molecule organic compounds.

[0080] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polylactic acid to methyl lactate in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0081] After 6 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 98%.

[0082] After 8 hours of reaction, the conversion rate of polylactic acid to methyl lactate was 100%.

[0083] Example 4

[0084] Poly(ethylene terephthalate) resin (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 200°C for 6 hours. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding a small molecule organic compound.

[0085] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polyethylene terephthalate (PET) to dimethyl terephthalate in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results were as follows: the conversion rate of PET to dimethyl terephthalate was 100%.

[0086] Example 5

[0087] A mineral water bottle made of polyethylene terephthalate was washed with distilled water, dried, and cut into pieces with scissors. The sample (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 200°C for 6 hours. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding a small molecule organic compound.

[0088] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polyethylene terephthalate (PET) to dimethyl terephthalate in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results were as follows: the conversion rate of PET to dimethyl terephthalate was 100%.

[0089] Example 6

[0090] Supermarket fruit packaging boxes made of polyethylene terephthalate were washed with distilled water, dried, and cut into pieces with scissors. The sample (containing 4 mmol of ester bonds) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 200°C for 6 hours. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding small-molecule organic compounds.

[0091] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of polyethylene terephthalate (PET) to dimethyl terephthalate in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results were as follows: the conversion rate of PET to dimethyl terephthalate was 100%.

[0092] Example 7

[0093] Poly(bisphenol A carbonate) resin (containing 2 mmol of carbonate bonds, i.e., CO3 groups) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 140°C on a heater for a certain period of time. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the reaction vessel, yielding a small molecule organic compound.

[0094] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of poly(bisphenol A carbonate) to bisphenol A in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0095] After 6 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 89%.

[0096] After 12 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 100%.

[0097] Among them, the detailed results are as follows Figure 2 As shown, Figure 2 Six 1H NMR spectra (300MHz, deuterated chloroform as solvent, 6.5–7.5 ppm range) characterized the alcoholysis of poly(bisphenol A carbonate) to bisphenol A. The red hydrogen peaks are characteristic peaks of the reactants and products.

[0098] Example 8

[0099] DVD disc substrates made of poly(bisphenol A carbonate) were washed with distilled water, dried, and cut into pieces. The sample (containing 2 mmol of carbonate bonds, i.e., CO3 groups) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 140°C on a heater for a certain time. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding small-molecule organic compounds.

[0100] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of poly(bisphenol A carbonate) to bisphenol A in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0101] After 6 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 71%.

[0102] After 12 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 100%.

[0103] Example 9

[0104] The lenses of the poly(bisphenol A carbonate) goggles were washed with distilled water, dried, and cut into pieces with scissors. The sample (containing 2 mmol of carbonate bonds, i.e., CO3 groups) and methanol (100 mmol) were added to a reaction vessel, which was then sealed. Carbon dioxide gas (4 MPa) was then introduced into the reaction vessel. The reaction vessel was heated to 140°C on a heater for a certain time. After the reaction was complete, the reaction vessel was cooled to room temperature, and then the carbon dioxide gas was slowly released from the vessel, yielding a small molecule organic compound.

[0105] Following the test method in Example 1, after opening the reaction vessel, 5 mL of dichloromethane was added to dissolve the product. The conversion rate of poly(bisphenol A carbonate) to bisphenol A in the solution was detected using 1H NMR spectroscopy (with deuterated chloroform as the solvent). The results are as follows:

[0106] After 6 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 86%.

[0107] After 12 hours of reaction, the conversion rate of poly(bisphenol A carbonate) to bisphenol A was 100%.

[0108] Comparative Example 1

[0109] The experiment was carried out according to Example 1, except that the heating temperature was adjusted from 140°C to 120°C. The results showed that after 8 hours of reaction, the conversion rate of polylactic acid to methyl lactate was only 25%.

[0110] Comparative Example 2

[0111] The procedure was carried out as described in Example 1, except that carbon dioxide gas was not introduced. The results showed that after 8 hours, no polylactic acid was converted.

[0112] Comparative Example 3

[0113] The experiment was carried out according to Example 4, except that the heating temperature was adjusted from 200°C to 170°C. The results showed that after 8 hours, the polyethylene terephthalate (PET) did not transform and remained in resin form.

[0114] Comparative Example 4

[0115] The procedure was carried out as in Example 1, except that carbon dioxide gas was not introduced. The results showed that after 8 hours, the polyethylene terephthalate (PET) did not transform and remained in resin form.

[0116] Comparative Example 5

[0117] The experiment was carried out according to Example 7, except that the heating temperature was adjusted from 140°C to 120°C. The results showed that after 8 hours, the poly(bisphenol A carbonate) did not transform and still maintained the resin morphology.

[0118] Comparative Example 6

[0119] The procedure was carried out as described in Example 7, except that carbon dioxide gas was not introduced. The results showed that the poly(bisphenol A carbonate) did not transform after 8 hours and remained in resin form.

[0120] As demonstrated in the above embodiments, the method of the present invention can effectively alcoholyze polyester and polycarbonate materials with a high alcoholysis rate. A comparison with the comparative examples shows that the alcoholysis of polyester and polycarbonate requires a certain temperature; and the presence of carbon dioxide plays a crucial catalytic role in the alcoholysis of polyester and polycarbonate.

[0121] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for the alcoholysis and recovery of polymer materials, characterized in that, Includes the following steps: Polymer materials and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain small molecule organic compounds; in, The polymer material is a polyester material and / or a polycarbonate material; The catalyst is carbon dioxide gas.

2. The method according to claim 1, characterized in that, The polyester material includes polylactic acid and / or polyethylene terephthalate; The polycarbonate material includes poly(bisphenol A carbonate).

3. The method according to claim 1, characterized in that, The alcoholysis reaction is carried out at a temperature of 140–200°C for a time of 4–12 hours.

4. The method according to claim 1, characterized in that, Includes the following steps: Polylactic acid and methanol are subjected to an alcoholysis reaction in the presence of a catalyst to obtain methyl lactate; or Poly(ethylene terephthalate) and methanol are subjected to alcoholysis reaction in the presence of a catalyst to obtain dimethyl terephthalate and ethylene glycol; or Poly(bisphenol A carbonate) and methanol were subjected to alcoholysis reaction in the presence of a catalyst to obtain bisphenol A and dimethyl carbonate.

5. The method according to claim 1, characterized in that, The relationship between the amount of polymer material and methanol is as follows: The number of moles of methanol is greater than the number of moles of ester / carbonate bonds in the polymer material.

6. The method according to any one of claims 1 to 5, characterized in that, Specifically, the following steps are included: Polymer materials and methanol are added to a reaction vessel, which is then sealed. Carbon dioxide gas is then introduced into the reaction vessel. The reaction vessel is heated to carry out an alcoholysis reaction. After the reaction is completed, the temperature is lowered and the carbon dioxide gas in the reaction vessel is released to obtain small molecule organic compounds.

7. The method according to claim 6, characterized in that, When carbon dioxide gas is introduced into the reactor, the pressure of the carbon dioxide gas inside the reactor is controlled to be 1-4 MPa.

8. The method according to claim 1, characterized in that, The molar ratio of ester bonds to methanol in the polyester material is 1:25; The polycarbonate material has a carbon bond to methanol molar ratio of 1:

50.

9. The method according to claim 6, characterized in that, The reactor is a stainless steel reactor with a volume of 25 mL.

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