A method for preparing a porous PET membrane, its product, and a method for degrading PET products.

Abstract

This invention discloses a method for preparing a porous PET membrane, its product, and a method for degrading PET products. The method involves physically mixing the PET product to be recycled with a thermodynamically compatible amorphous component, followed by melt pressing to obtain a blend membrane with a thickness of 1 μm to 1 mm. The thermodynamically compatible amorphous component in the blend membrane is then extracted using Soxhlet extraction to obtain the porous PET membrane. The porous PET membrane prepared by this method has interconnected continuous nanopores and low crystallinity, which facilitates the infiltration and bulk degradation by bio-enzymes, significantly improving the energy efficiency of bio-enzymatic degradation of PET products and effectively reducing energy consumption and recycling losses during the bio-enzymatic degradation process.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials technology, and particularly relates to a method for preparing a porous PET membrane and its product, as well as a method for degrading PET products. Background Technology

[0002] Polyethylene terephthalate (PET) is widely used in food packaging and textiles due to its excellent physicochemical properties, such as thermal stability, mechanical properties, chemical resistance, and safety. However, PET products cannot be effectively degraded in nature, thus becoming a significant source of plastic pollution. How to quickly and effectively recycle and reuse PET products is currently a key concern.

[0003] Enzymatic degradation is a low-energy-consumption, high-yield PET recycling strategy that has attracted widespread attention in recent years. PET-degrading enzymes act on the lactone bonds in the PET molecular chain, causing PET to break down and depolymerize. The recovered terephthalic acid (TPA) monomer can then be used as a monomer to synthesize PET, achieving recycling. To date, experts in enzyme structural biology have discovered and extracted dozens of PET-degrading enzymes and improved their degradation efficiency by genetically modifying them. Currently, the most active PET-degrading enzyme can achieve near-complete degradation of amorphous PET within 3.3 hours.

[0004] Besides increasing the activity of PET degrading enzymes, structural modification of PET products is another way to improve the efficiency of PET bio-enzymatic degradation. PET products are usually solid sheets. If PET products are placed directly into bio-enzymes for degradation, the enzymes can only act on the surface of the PET sheet to achieve surface degradation. Only after the surface layer is degraded can the enzymes penetrate to the inner surface layer for further degradation. This results in the degradation rate being limited by the low-energy characteristics of the PET product surface (making it difficult to adhere to other materials). Some researchers have improved the bio-enzymatic degradation efficiency by grinding / ball milling PET products. The underlying mechanism is to increase the contact area between the enzyme and the PET substrate and prolong the interaction time. However, grinding / ball milling leads to an increase in the crystallinity of the PET product (which is detrimental to degradation), and the significant reduction in the size of the PET substrate does not destroy the dense internal structure. Therefore, the degradation efficiency is still affected by the low-energy characteristics of the PET surface. How to transform the bio-enzymatic degradation of PET products from surface degradation to bulk degradation is the key to significantly improving the degradation rate of PET products and is also one of our goals for structural modification of PET products.

[0005] Furthermore, the degradation of highly crystalline PET products is a significant challenge. Although currently reported bioenzymes can degrade amorphous and low-crystalline PET products in a short time, their ability to degrade PET products with a crystallinity higher than 20% is very limited, or even nonexistent. Therefore, effectively reducing the crystallinity of PET degradation substrates is another objective of our structural modification of PET products. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for preparing porous PET membranes, as well as a method for the degradation of PET products.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a porous PET membrane, specifically:

[0009] At temperatures above 250°C, PET products are physically mixed with thermodynamically compatible amorphous components to obtain blends.

[0010] The blend is melt-pressed at a temperature above 250°C, then transferred to a temperature above 180°C for crystallization for at least 1 minute, and finally cooled naturally at room temperature to obtain a fully crystalline blend film.

[0011] A thermodynamically compatible amorphous solvent that does not dissolve PET was used to fully extract and dry the fully crystalline blend film to obtain a porous PET film after structural modification pretreatment.

[0012] Preferably, the physical mixing involves adding the PET product and the thermodynamically compatible amorphous component to a co-solvent, dissolving them fully at a temperature above room temperature, and then removing the solvent.

[0013] Preferably, the physical mixing involves adding PET products and thermodynamically compatible amorphous components into a mixing device to melt-mix the blended components.

[0014] Preferably, the thermodynamically compatible amorphous component includes at least one of polyarylate PAR and polyetherimide PEI.

[0015] Preferably, the mass ratio of the PET product to the thermodynamically compatible amorphous component is (0.01:100) to (100:0.01).

[0016] Preferably, the crystallinity of the PET product is higher than 20%.

[0017] Secondly, the present invention provides a porous PET film with nanoscale slit pores, which is prepared by the above method.

[0018] Thirdly, this invention provides a method for degrading PET products, specifically:

[0019] The PET products to be recycled are used to prepare a PET porous membrane using the method described above. The PET porous membrane is then used as an enzyme degradation substrate, and PET hydrolase is added for degradation.

[0020] Preferably, the degradation solvent is a glycine buffer solution.

[0021] Preferably, the PET hydrolase used is FAST-PETase-N212A / N277A enzyme, the degradation temperature is 50℃, and the pH is 9.

[0022] The beneficial effects of this invention are at least as follows:

[0023] This invention successfully prepares a porous PET membrane with a unique structure by physically mixing PET products to be recycled with thermodynamically compatible amorphous components, followed by a series of processes including melt pressing, crystallization, and extraction. This membrane possesses nanoscale slit pores with lengths ranging from 100 to 200 nm and widths from 1 to 100 nm, and the pore size can be controlled by adjusting the crystallization temperature. This nanoscale slit pore structure provides more entry channels for bioenzymes, enabling them to rapidly penetrate the interior of the PET membrane. This effectively overcomes the limitation of traditional PET products where bioenzymes can only perform surface degradation, greatly promoting the bulk degradation of the PET membrane by bioenzymes and significantly increasing the degradation rate.

[0024] The special structure of the porous PET membrane of this invention provides more contact interfaces and attachment points for enzyme molecules, increasing the number of sites that enzymes can attack per unit time, thereby achieving bulk degradation of the PET membrane and effectively improving the degradation rate of biological enzymes.

[0025] The PET porosimetry pretreatment used in this invention can reduce the crystallinity of PET and make it easier for biological enzymes to enter the crystal region, thereby effectively improving the degradation efficiency.

[0026] The PET porous membrane of this invention can be prepared using only common melt mixing equipment or simple solution treatment, making industrial preparation simple and highly processable. Attached Figure Description

[0027] Figure 1 Scanning electron microscope (SEM) images of the PET porous membranes prepared in Examples 1 and 2, where (a) is Example 1 and (b) is Example 2.

[0028] Figure 2 Crystallinity data for PET film products prepared in Comparative Examples 1 and 2 and Examples 1 and 2.

[0029] Figure 3 The enzymatic degradation rate data are for the PET film products prepared in Comparative Examples 1 and 2 and Examples 1 and 2.

[0030] Figure 4 The degradation rate data are for the PET film products prepared in Comparative Examples 1 and 2 and Examples 1 and 2 after degradation. Detailed Implementation

[0031] The embodiments and examples of the present invention will be described in detail below. However, those skilled in the art will understand that the following embodiments and examples are for illustrative purposes only and should not be considered as limiting the scope of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0032] It should be noted that:

[0033] Unless otherwise specified, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0034] Unless otherwise specified, all the technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0035] Unless otherwise stated, the technical and scientific terms used herein have the same meanings as those familiar to those skilled in the art. Furthermore, any methods or materials similar to or equivalent to those described herein may also be used in this invention.

[0036] As can be seen from the background art, in order to change the bioenzymatic degradation of PET products from surface degradation to bulk degradation, the present invention proposes a porous PET membrane and its products, as well as a method for degrading PET products.

[0037] This invention prepares a porous PET membrane as a substrate for enzymatic degradation by blending and extracting thermodynamically compatible amorphous components from recycled PET products. The enzymes can degrade the substrate bulk through the continuous nanopores in the porous PET membrane, significantly improving degradation efficiency. Furthermore, the crystallinity of the porous PET membrane is significantly reduced compared to unmodified PET products, and its crystalline structure is more conducive to enzyme infiltration. Therefore, this invention provides a method for the rapid and efficient recycling of PET products using porous PET membranes, which holds promise for large-scale degradation and reprocessing of PET products.

[0038] Therefore, on the one hand, at least one embodiment provides a method for preparing a porous PET membrane, specifically:

[0039] At temperatures above 250°C, PET products are physically mixed with thermodynamically compatible amorphous components to obtain blends.

[0040] The blend is melt-pressed at a temperature above 250°C, then transferred to a temperature above 180°C for crystallization for at least 1 minute, and finally cooled naturally at room temperature to obtain a fully crystalline blend film.

[0041] A thermodynamically compatible amorphous solvent that does not dissolve PET was used to fully extract and dry the fully crystalline blend film to obtain a porous PET film after structural modification pretreatment.

[0042] In one embodiment, the physical mixing involves adding the PET product and the thermodynamically compatible amorphous component to a co-solvent, dissolving them fully at a temperature above room temperature, and then removing the solvent.

[0043] In one embodiment, the physical mixing involves adding PET products and thermodynamically compatible amorphous components to a mixing equipment to melt-mix the blended components.

[0044] According to the present invention, after the thermodynamically compatible amorphous component is blended with the PET product, the amorphous component is removed through subsequent melt pressing, crystallization, and extraction steps, leaving corresponding spaces in the PET matrix and forming interconnected continuous nanopores. These nanopores provide channels for bioenzymes to rapidly penetrate into the interior of the PET film, making it possible for bioenzymatic degradation to change from traditional surface degradation to bulk degradation, greatly increasing the contact opportunities between bioenzymes and PET molecular chains, thereby improving the degradation rate. Simultaneously, the presence of the thermodynamically compatible amorphous component can interfere with the orderly arrangement of PET molecular chains during crystallization. During crystallization, the amorphous component occupies a certain space, hindering the formation of a tight and regular crystal structure in the PET molecular chains, resulting in a significant reduction in the crystallinity of the final prepared porous PET film. Finally, during melt blending or solution blending, the thermodynamically compatible amorphous component also plays a certain plasticizing or lubricating role. They can improve the melt flowability of the PET product, making the blend easier to handle during melt pressing and other processing, and contributing to the formation of a uniform film structure. In a preferred embodiment, the thermodynamically compatible amorphous component includes at least one of polyarylate PAR and polyetherimide PEI; the mass ratio of the PET product to the thermodynamically compatible amorphous component is (0.01:100) to (100:0.01).

[0045] According to the present invention, the problem of the difficulty in degrading PET products in nature is addressed, with the degradation of highly crystalline PET products (crystallinity higher than 20%) being a major challenge. While highly crystalline PET products are the focus of this invention in addressing their enzymatic degradation, the method of this invention is also applicable to PET products with other crystallinity ranges.

[0046] On the other hand, at least one embodiment provides a porous PET membrane prepared using the above-described method. This porous PET membrane is a thin film with a thickness of 1 μm to 1 mm, and has several interconnected continuous pores with a length of 100 to 200 nm and a width of 1 to 100 nm. The pore size can be controlled by changing the crystallization temperature. Simultaneously, the crystallinity of this porous PET membrane is less than 10%. These structural features allow biological enzymes to rapidly infiltrate the porous PET membrane and achieve bulk degradation of the porous PET membrane.

[0047] In another aspect, at least one embodiment provides a method for degrading PET products, specifically:

[0048] The PET products to be recycled are used to prepare a PET porous membrane using the method described above. The PET porous membrane is then used as an enzyme degradation substrate, and PET hydrolase is added for degradation.

[0049] A method for pretreating PET products by modifying their porous structure before enzymatic degradation effectively improves the energy efficiency of enzymatic degradation, thereby reducing energy consumption and recycling losses during the process. The nanoscale slit-pore structure of the porous PET membrane provides more entry channels for enzymes, allowing them to rapidly penetrate the membrane. This effectively overcomes the limitation of traditional PET products where enzymes can only perform surface degradation, greatly promoting the bulk degradation of the PET membrane and significantly increasing the degradation rate. This special structure creates more contact interfaces and attachment points for enzyme molecules. Compared to solid sheet-like ordinary PET products, the number of sites that enzymes can attack per unit time is significantly increased. Enzyme molecules can more fully contact the PET molecular chains and act on lactone bonds, causing PET chain breakage and depolymerization, thus achieving more efficient degradation. This characteristic enables the porous PET membrane of this invention to exhibit superior performance during enzymatic degradation, achieving a higher degree of degradation in a shorter time and effectively improving the recycling efficiency of PET products. Nanoscale slit pores significantly reduce the crystallinity of PET, lowering it to below 10%. Lower crystallinity means a looser arrangement of PET molecular chains, and the crystal structure is more conducive to the wetting of bio-enzymes. Bio-enzymes can more easily enter the crystalline regions and interact with the PET molecular chains, thereby effectively improving degradation efficiency. This is of great significance for solving the problem of the difficulty in degrading highly crystalline PET products, enabling highly crystalline PET products (crystallinity above 20%) that were previously difficult to degrade by bio-enzymes to achieve efficient degradation, thus broadening the application scope of bio-enzymatic degradation of PET products.

[0050] For melt-blended systems, such as PET / PAR blends, the specific steps of this method are as follows:

[0051] Step (1). Place PET and PAR separately in a vacuum drying oven and dry at about 120°C until their weight remains constant;

[0052] Step (2). Add the dried PET and PAR to the melt mixing equipment. The mass ratio of PET to PAR is (0.01:100) ~ (100:0.01). Melt mix at a temperature above 250℃ for 5~10 minutes.

[0053] In a preferred embodiment, the mass ratio of PET to PAR is 1:1;

[0054] In a preferred embodiment, the melting and mixing temperature in step (2) is 270°C and the mixing time is 5 min;

[0055] The melt mixing equipment mentioned is a variety of commonly used industrial devices such as an internal mixer, a single-screw extruder, a twin-screw extruder, or an injection molding machine;

[0056] Step (3). Discharge the above-mentioned blend after melt mixing from the melt mixing equipment and cool it to room temperature;

[0057] Step (4). The above-cooled blend is melt-pressed at a temperature above 250°C for 2 to 10 minutes, and then transferred to a temperature above 180°C for crystallization for at least 1 minute to prepare a film with a thickness of 10 μm to 1 mm.

[0058] In a preferred embodiment, the melt compression temperature is 270°C and the compression time is 2 min;

[0059] In a preferred embodiment, the crystallization temperature is 230°C and the crystallization time is 2 hours.

[0060] Step (5). Extract the membrane obtained in step (4) using Soxhlet extraction. The extractant is a good solvent for PAR. The heating temperature is controlled so that the extractant is refluxed once every 6 to 8 minutes. The extraction time is 72 to 144 hours. After the extraction is completed, take it out and dry it overnight in a vacuum drying oven at 80°C to remove residual solvent and obtain a PET porous membrane.

[0061] In a preferred embodiment, the good solvent for the PAR is chloroform, dichloromethane, carbon tetrachloride, or acetone.

[0062] Step (6): Take 5g of the PET porous membrane obtained in step (5) as the substrate for bioenzymatic degradation, add 40μL LFAST-PETase-N212A / N277A enzyme (5μg / mL) to form an 800mL mixture, and place it in a buffer solution of 50mM glycine and pH 9.0 for degradation testing at 50℃. Determine the amount of product generated every 24 hours of degradation, and calculate the degradation rate after the degradation is completed based on the total amount of product generated.

[0063] The product yield was determined and analyzed by high performance liquid chromatography (HPLC). The analytical column was an InertSustain C18 column (4.6×250mm, 5μm), the mobile phase was methanol / phosphate (20 mM, pH 2.5), the flow rate was 1 mL / min, the detection wavelength was 254 nm, the elution conditions were 0~15 min, and the methanol linear gradient was 35%~70%.

[0064] For solution blending systems, such as PET / PEI blends, the specific steps of this method are as follows:

[0065] Step (1). Mix and dissolve PET and PEI in their co-solvent, with the mass ratio of PET to PEI being (0.01:100) ~ (100:0.01).

[0066] In a preferred embodiment, the solvent is dichloroacetic acid or a phenol / tetrachloroethane mixed solvent (volume ratio of 60 / 40).

[0067] In a preferred embodiment, the solvent used is dichloroacetic acid;

[0068] In a preferred embodiment, the mass ratio of PET to PEI is 7:3;

[0069] Step (2). Wash the above mixed solution of PET and PEI with deionized water to precipitate the mixed solute of PET / PEI;

[0070] Step (3). The PET / PEI mixed solute precipitated by washing is placed in a vacuum oven at ~80℃ for drying to obtain PET / PEI blend powder;

[0071] Step (4). The dried blended powder is melt-pressed at a temperature above 250°C for 2 to 10 minutes and then transferred to a temperature above 180°C for at least 1 minute to crystallize and prepare a film with a thickness of 10 μm to 1 mm.

[0072] In a preferred embodiment, the melt compression temperature is 270°C and the compression time is 5 min;

[0073] In a preferred embodiment, the crystallization temperature is 230°C and the crystallization time is 2 hours.

[0074] Step (5). Extract the film obtained in step (4) using Soxhlet extraction. The extractant is a good solvent for PEI. The heating temperature is controlled so that the extractant is refluxed once every 6 to 8 minutes. The extraction time is 72 to 144 hours. After the extraction is completed, take it out and dry it overnight in a vacuum drying oven at 80°C to remove residual solvent and obtain a PET porous membrane.

[0075] In a preferred embodiment, the good solvent for the PEI is methanol, ethanol, dichloromethane, chloroform, or acetone.

[0076] Step (6): Take 5g of the PET porous membrane obtained in step (5) as the substrate for bioenzymatic degradation, add 40μL LFAST-PETase-N212A / N277A enzyme (5μg / mL) to form an 800mL mixture, and place it in a buffer solution of 50mM glycine and pH 9.0 for degradation testing at 50℃. Determine the amount of product generated every 24 hours of degradation, and calculate the degradation rate after the degradation is completed based on the total amount of product generated.

[0077] The product yield was determined and analyzed by high performance liquid chromatography (HPLC). The analytical column was an InertSustain C18 column (4.6×250mm, 5μm), the mobile phase was methanol / phosphate (20mM, pH 2.5), the flow rate was 1mL / min, the detection wavelength was 254nm, the elution conditions were 0~15min, and the methanol linear gradient was 35%~70%.

[0078] The following will describe in detail some typical embodiments that embody the features and advantages of the present invention. It should be understood that the present invention can have many variations in different embodiments, all of which do not depart from the scope of the present invention. Furthermore, the descriptions and illustrations herein are for illustrative purposes only and are not intended to limit the present invention.

[0079] The PAR used in the following examples is manufactured by Unikita Corporation of Japan, model U100; the PEI is manufactured by Sigma-Aldrich Corporation of the United States, product number 700193.

[0080] Example 1

[0081] Highly crystalline PET sheets to be recycled (e.g., about 25% crystallinity) and PAR were dried overnight in a vacuum drying oven at 120°C.

[0082] Take 35g of PET flakes to be recycled and 35g of PAR and add them to the internal mixer in sequence. The internal mixer temperature is 270℃ and the rotor speed is 20rpm / min. Mix for 2min. Then increase the rotor speed to 50rpm / min and mix for 5min before discharging and cooling to room temperature.

[0083] The above-mentioned melt-blended mixture was hot-pressed in a hot press at 280°C for 2 minutes to form a 300μm film;

[0084] The hot-pressed film was transferred to 200℃ for 2 hours to crystallize completely.

[0085] The crystallized film was subjected to Soxhlet extraction using PAR as a good solvent. The heating temperature was controlled so that the extract was refluxed every 6 to 8 minutes. The extraction time was 72 to 144 hours. After the extraction was completed, the film was taken out and dried overnight in a vacuum drying oven at 80°C to remove residual solvent and obtain a PET porous membrane.

[0086] 5g of the above-mentioned porous PET membrane was used as the substrate for bioenzymatic degradation. 40μL of FAST-PETase-N212A / N277A enzyme (5μg / mL) was added to form an 800mL mixture. The mixture was placed in a buffer solution of 50mM glycine and pH 9.0 for degradation testing at 50℃. The amount of product generated every 24 hours of degradation was determined, and the degradation rate at the end of the degradation process was calculated from the total amount of product generated.

[0087] Example 2

[0088] Take 14g of highly crystalline PET sheets to be recycled (e.g., about 25% crystallinity) and 6g of PEI and add them sequentially to 250mL of co-dissolution solvent, and stir overnight at 50~80℃ until completely dissolved;

[0089] The above solution was washed with deionized water to precipitate the PET / PEI mixed solute.

[0090] The PET / PEI mixed solute precipitated after washing was placed in a vacuum oven at ~80℃ and dried to obtain PET / PEI mixed powder;

[0091] The above mixture powder was hot-pressed in a hot press at 290°C for 5 minutes to form a 300μm film;

[0092] The hot-pressed film was transferred to 220℃ for 2 hours to allow complete crystallization.

[0093] The crystallized film was subjected to Soxhlet extraction using PEI as a good solvent. The heating temperature was controlled so that the extract was refluxed every 6 to 8 minutes. The extraction time was 72 to 144 hours. After the extraction was completed, the film was taken out and dried overnight in a vacuum drying oven at 80°C to remove residual solvent and obtain a PET porous membrane.

[0094] 5g of the above-mentioned porous PET membrane was used as the substrate for bioenzymatic degradation. 40μL of FAST-PETase-N212A / N277A enzyme (5μg / mL) was added to form an 800mL mixture. The mixture was placed in a buffer solution of 50mM glycine and pH 9.0 for degradation testing at 50℃. The amount of product generated every 24 hours of degradation was determined, and the degradation rate at the end of the degradation process was calculated from the total amount of product generated.

[0095] Comparative Example

[0096] Five g of highly crystalline PET sheets (e.g., approximately 25% crystallinity) were used as the substrate for bioenzymatic degradation. 40 μL of FAST-PETase-N212A / N277A enzyme (5 μg / mL) was added to form an 800 mL mixture, which was then placed in a buffer solution of 50 mM glycine and pH 9.0 for degradation testing at 50°C. The amount of product generated per 24 hours of degradation was determined, and the degradation rate at the end of degradation was calculated from the total amount of product generated. This comparative example simulates the traditional PET sheet treatment method (hot-press crystallization only), contrasting it with the PET porous membrane preparation process in the examples (including blending with thermodynamically compatible amorphous components, extraction, and other structural modification steps). This further demonstrates that the present invention, through a special porous structure modification pretreatment method, can significantly improve the bioenzymatic degradation performance of PET products.

[0097] By comparing the data of Examples 1 and 2 with those of the comparative examples during the degradation process (e.g.) Figure 1 (a) Figure 1 (b) Figure 2 , Figure 3 , Figure 4 As shown in the figure, the PET porous membrane prepared by this invention exhibits significant advantages in terms of crystallinity, enzyme degradation rate, and degradation rate after degradation. Examples 1 and 2 have better nanoscale slit pore structures ( Figure 1 Examples 1 and 2 demonstrate the ability to reduce the original crystallinity from above 20% to a lower crystallinity. Figure 2 Furthermore, their degradation rates (reflected by the degradation quality of the PET substrate within 48 hours) and the degradation rate of the PET substrate after degradation were significantly higher than those of the control group (…). Figure 3 , 4 This invention demonstrates that the crystal structure, achieved through the method of this invention, is more conducive to the wetting of biological enzymes and facilitates sufficient contact between the enzyme and the substrate, thereby achieving bulk degradation of the PET substrate and significantly improving the degradation rate and efficiency. The method of this invention, by preparing a PET porous membrane with a unique structure, effectively improves the energy efficiency of bioenzymatic degradation of PET products, reduces energy consumption and recycling losses, and provides an efficient and feasible solution for the recycling of PET products. Furthermore, the preparation process of this invention is simple, has strong industrial applicability, and possesses good application prospects and promotional value.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a porous PET membrane, characterized in that, The method includes: At temperatures above 250°C, PET products are physically mixed with thermodynamically compatible amorphous components to obtain blends. The blend is melt-pressed at a temperature above 250°C, then transferred to a temperature above 180°C for crystallization for at least 1 minute, and finally cooled naturally at room temperature to obtain a fully crystalline blend film. A thermodynamically compatible amorphous solvent that does not dissolve PET was used to fully extract and dry the fully crystalline blend film to obtain a porous PET film after structural modification pretreatment. The thermodynamically compatible amorphous component includes at least one of polyarylate PAR and polyetherimide PEI; The mass ratio of the PET product to the thermodynamically compatible amorphous component is (0.01:100) to (100:0.01).

2. The method according to claim 1, characterized in that, The physical mixing involves adding the PET product and the thermodynamically compatible amorphous component to a co-solvent, dissolving them fully at a temperature above room temperature, and then removing the solvent.

3. The method according to claim 1, characterized in that, The physical mixing involves adding PET products and thermodynamically compatible amorphous components into a mixing equipment to melt-mix the blended components.

4. The method according to any one of claims 1-3, characterized in that, The crystallinity of the PET product is higher than 20%.

5. A method for degrading PET products, characterized in that, The method includes: The PET products to be recycled are prepared into a PET porous membrane using the method described in any one of claims 1-4. The PET porous membrane is then used as an enzyme degradation substrate, and PET hydrolase is added for degradation.

6. The method according to claim 5, characterized in that, The degradation solvent used was glycine buffer.

7. The method according to claim 5, characterized in that, The PET hydrolase used is FAST-PETase-N212A / N277A enzyme, with a degradation temperature of 50℃ and pH=9.

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