An asymmetric hollow fiber gas separation membrane, its preparation method and application

Abstract

This invention provides an asymmetric hollow fiber gas separation membrane made of an amphiphilic block copolymer, comprising an internal porous layer and an outer dense layer; the pores inside the porous layer are formed by hydrophilic blocks, and the dense layer is formed by hydrophobic blocks. This invention also provides a method for preparing the asymmetric hollow fiber gas separation membrane, using the amphiphilic block copolymer as raw material to prepare nascent hollow fibers. The nascent hollow fibers are first immersed in a good solvent containing hydrophilic blocks, causing the hydrophilic blocks to swell and form pores. After washing away the good solvent from the hydrophilic blocks, the hollow fibers are then allowed to fully contact only the outer surface with the good solvent from the hydrophobic blocks, promoting the hydrophobic blocks on the surface of the hollow fibers to fill the pores and form a dense layer. The asymmetric hollow fiber gas separation membrane of this invention exhibits excellent gas separation performance and high mechanical strength. The preparation method of this invention does not use solvents on a large scale, is environmentally friendly and convenient, and can be used for large-scale industrial production of asymmetric hollow fiber membranes.

Description

Technical Field

[0001] This invention belongs to the field of porous material gas separation membrane technology, specifically relating to asymmetric hollow fiber gas separation membranes and methods for preparing asymmetric hollow fiber gas separation membranes. Background Technology

[0002] In recent years, the application of separation membranes in gas separation and gas emission control has been increasing. Currently, separation membranes are widely used for the separation of various gases, such as O2 / N2 separation for oxygen enrichment; CO2 / CH4 separation for natural gas or biogas purification; H2 / CO separation for adjusting syngas ratios; and CO2 / N2 separation to reduce targeted CO2 emissions into the atmosphere. Efficient CO2 separation is of great significance for energy purification and low-carbon environmental protection. Traditional CO2 separation technologies include adsorption, chemical absorption, physical absorption, cryogenic separation, and membrane separation. Membrane separation offers advantages such as low separation cost and low energy consumption; compared to other methods, membrane separation can reduce separation costs by up to 90%, thus it is widely used for CO2 separation. Hollow fiber membranes, due to their high packing density, simple operation, easy cleaning, and fast permeation rate, are widely used as gas separation membranes.

[0003] In the prior art, there are also reports on methods for preparing asymmetric hollow fiber membranes by melt co-extrusion. For example, patent document CN113226525A discloses a method for obtaining a double-layer asymmetric hollow fiber membrane by co-extruding two thermoplastic polyolefin polymers with different properties through a single screw extruder. This method does not generate a large amount of organic wastewater. However, the use of two different materials to prepare hollow fiber membranes by co-extrusion can lead to a large difference in stability between the two membrane layers. At the same time, the spinneret is a key component in the preparation of multilayer hollow fiber spinning. Installing three independent concentric annular holes in such a small space and making the membrane solution flow in the channel places higher demands on the design and process of the spinneret. There are also reports disclosing methods for preparing asymmetric hollow fiber membranes with higher mechanical properties. For example, patent document CN113750817A discloses a method for preparing asymmetric hollow fiber membranes with higher mechanical strength. This method involves in-situ heat treatment of a polyamide precursor hollow fiber membrane containing hydroxyl groups at the ortho position. Utilizing the principle of molecular rearrangement and skin densification on the precursor surface at high temperatures, an asymmetric hollow fiber membrane with a dense skin is obtained. Although the hollow fiber membranes prepared by this method have high mechanical strength, large-scale membrane preparation still relies on toxic solvents, which is detrimental to sustainable development and environmental protection. Furthermore, the high cost of raw material synthesis makes large-scale preparation difficult.

[0004] Therefore, it is necessary to develop a new method for preparing asymmetric hollow fiber membranes to solve the problem that the existing preparation process conditions are harsh and not conducive to large-scale industrial production. Summary of the Invention

[0005] The primary objective of this invention is to provide an asymmetric hollow fiber gas separation membrane that simultaneously possesses good gas permeation rate, gas selectivity, mechanical strength, and flexibility.

[0006] Another objective of this invention is to provide a method for preparing the asymmetric hollow fiber gas separation membrane, which requires only a small amount of solvent, is environmentally friendly, has low cost, and is suitable for large-scale industrial application.

[0007] Another object of the present invention is to provide the application of the aforementioned asymmetric hollow fiber gas separation membrane.

[0008] The above-mentioned objective of the present invention is achieved through the following technical solution: First, an asymmetric hollow fiber gas separation membrane is provided, which is made of an amphiphilic block copolymer; it includes an inner porous layer and an outer dense layer; the pores inside the porous layer are formed by hydrophilic blocks in the amphiphilic block copolymer, and the dense layer is formed by filling the surface pores with hydrophobic blocks of the amphiphilic block copolymer.

[0009] In this invention, the amphiphilic block copolymer is composed of hydrophobic block A and hydrophilic block B (AB, ABA), wherein the hydrophobic block A can be selected from any one of polysulfone (PSF), polyethersulfone (PES), and polystyrene (PS), and the hydrophilic block B can be selected from any one of polyethylene glycol (PEG), poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). The total molecular weight of the amphiphilic block copolymer is 50,000-500,000 Daltons.

[0010] In a preferred embodiment of the present invention, the hydrophobic block A is PSF, and the hydrophilic block B is PEG. This combination of PSF blocks with superior mechanical properties ensures the high strength of the hollow fiber matrix; simultaneously, the highly flexible PEG segments can move freely, thus ensuring the extensibility of the hollow fiber membrane.

[0011] In a preferred embodiment of the present invention, the thickness of the dense layer of the asymmetric hollow fiber gas separation membrane is 0.5-12 μm, preferably 5-10 μm, and more preferably 6-7 μm.

[0012] In a preferred embodiment of the present invention, the dense layer pore size distribution of the asymmetric hollow fiber gas separation membrane is less than 0.5 nm.

[0013] In a preferred embodiment of the present invention, the porous layer of the asymmetric hollow fiber gas separation membrane has a porosity of 10%-60% and a pore size range of 15-20 nm.

[0014] In a preferred embodiment of the present invention, the CO2 permeation rate of the asymmetric hollow fiber gas separation membrane is higher than 20 GPU; more preferably higher than 30 GPU; and even more preferably higher than 40 GPU.

[0015] In a preferred embodiment of the present invention, the CO2 / N2 gas selectivity of the asymmetric hollow fiber gas separation membrane is higher than 10, more preferably higher than 12, and even more preferably higher than 15.

[0016] The asymmetric hollow fiber gas separation membrane described in this invention not only has excellent gas separation performance, but also high mechanical strength, can withstand high pressure, and still maintains a relatively good structure under 1 MPa gas pressure.

[0017] Based on this, the present invention also provides a method for preparing the asymmetric hollow fiber gas separation membrane, comprising: preparing nascent hollow fibers using an amphiphilic block copolymer containing hydrophobic blocks A and hydrophilic blocks B as raw materials; first immersing the nascent hollow fibers in a good solvent containing hydrophilic blocks B to treat them, causing the hydrophilic blocks B to swell and form channels; after washing away the good solvent containing the hydrophilic blocks B, allowing only the outer surface of the hollow fibers to fully contact the good solvent containing the hydrophobic blocks A, promoting the movement of the hydrophobic blocks A on the surface of the hollow fibers, filling the pores on the surface, and forming a dense layer.

[0018] In the preferred preparation method of the present invention, the interaction parameter between the good solvent of the hydrophilic block B and the hydrophilic block B is less than 0.5, more preferably less than 0.4 and greater than 0.3, and most preferably between 0.34 and 0.36.

[0019] In the preferred preparation method of the present invention, the interaction parameter between the good solvent of the hydrophobic block A and the hydrophobic block A is less than 0.5, more preferably greater than 0.4, and most preferably between 0.41 and 0.46.

[0020] In the preparation method described in this invention, the selection of a good solvent for hydrophilic block B and a good solvent for hydrophobic block A needs to be determined based on the specific solubility parameters of the polymerized blocks.

[0021] In one embodiment of the present invention, the hydrophilic block B and the hydrophobic block A are PEG and PSF, respectively. The good solvent for the hydrophilic block B can be selected from a mixed solvent composed of n-propanol and a first polar solvent, wherein the first polar solvent is selected from any one of acetone, tetrahydrofuran, or toluene, and the mass ratio of the first polar solvent is controlled to not exceed 50%, so that the interaction parameter of this mixed solvent relative to the PEG block is less than 0.5, or even lower. The good solvent for the hydrophobic block A can be selected from a mixture of a second polar solvent and water or an alcohol, wherein the second polar solvent is selected from any one of acetone, toluene, or xylene, and the weight ratio of the second polar solvent is controlled to be 5% to 70%, so that the interaction parameter of this mixed solvent relative to the PSF block is less than 0.5, but greater than 0.4.

[0022] Through experiments, the inventors discovered that when the hydrophobic block A is PSF, if the content of a second polar solvent such as acetone in the good solvent of hydrophobic block A is too high, it will cause the PSF block to be too mobile (the interaction parameter between the good solvent of hydrophobic block A and PSF is less than 0.4), leading to excessive collapse of the hollow fiber structure. Therefore, in a further preferred embodiment, when the second polar solvent is acetone, the content of acetone as the second polar solvent in the good solvent of hydrophobic block A is controlled to be 50-70 wt%. More preferably, the good solvent of hydrophobic block A is a mixed solution of acetone and water with an acetone content of 60-70 wt%.

[0023] In another embodiment of the present invention, the hydrophobic block A and the hydrophilic block B are PS and P2VP, respectively. The good solvent for the hydrophilic block B can be selected from a mixed solvent containing ethanol, and the mass ratio of ethanol is controlled to be more than 80% so that the interaction parameter of such mixed solvent relative to the PS block is less than 0.5, or even lower. The good solvent for the hydrophobic block A can be selected from a mixture of a second polar solvent and water or an alcohol. The second polar solvent is selected from any one of acetone, toluene or xylene, and the weight ratio of the second polar solvent is controlled to be 5% to 70% so that the interaction parameter of such mixed solvent relative to the P2VP block is less than 0.5, but greater than 0.4.

[0024] In another embodiment of the present invention, the hydrophobic block A and the hydrophilic block B are PS and PDMAEMA, respectively. The good solvent for the hydrophilic block B can be selected from a mixed solvent containing ethanol, and the mass ratio of ethanol is controlled to be more than 80%, so that the interaction parameter of such mixed solvent relative to the PS block is less than 0.5, or even lower. The good solvent for the hydrophobic block A can be selected from a mixture of a second polar solvent and water or an alcohol. The second polar solvent is selected from any one of acetone, toluene, or xylene, and the weight ratio of the second polar solvent is controlled to be 5% to 70%, so that the interaction parameter of such mixed solvent relative to the PDMAEMA block is less than 0.5, but greater than 0.4.

[0025] In the preparation method described in this invention, there are various methods for preparing nascent hollow fibers. For example, the solid amphiphilic block copolymer can be melt-spun into nascent hollow fibers, or a thinner nascent hollow fiber membrane can be prepared by further increasing the stretching process after melt spinning.

[0026] In the preferred preparation method of the present invention, the nascent hollow fibers are immersed in a good solvent of hydrophilic block B for treatment at 55-70°C for 0.5-5 hours; more preferably, they are immersed at 65-70°C for 1-3 hours.

[0027] In the preferred preparation method of the present invention, the good solvent for washing away the hydrophilic block B is to soak the hollow fiber in a long-chain alkane solvent at room temperature for 0.5-3 h; more preferably, it is to soak at room temperature for 1-2 h.

[0028] In a further preferred preparation method of the present invention, the hollow fiber is further dried after the good solvent of the hydrophilic block B is washed away.

[0029] In the preferred preparation method of this invention, the hollow fiber is allowed to fully contact only its outer surface with the good solvent of the hydrophobic block A, which is achieved by contacting it fully at room temperature for 0.5-3 hours; more preferably, by contacting it fully at room temperature for 0.5-1 hours. This full contact can be achieved in various ways, such as coating, soaking, spraying, misting, or steam treatment.

[0030] Furthermore, the present invention also provides the application of the aforementioned asymmetric hollow fiber gas separation membrane in CO2 / N2 separation or CO2 / CH4 separation.

[0031] This invention proposes a simple method for preparing asymmetric hollow fiber gas separation membranes using a single raw material, utilizing the affinity between amphiphilic block copolymers and solvents. Only the amphiphilic block copolymer is required; no other auxiliary components need to be added. The hollow fibers are sequentially treated under mild conditions using a good solvent for the hydrophilic blocks and a good solvent for the hydrophobic blocks of the amphiphilic block copolymer. This causes the hydrophilic blocks throughout the hollow fiber to swell and form pores. Then, the surface hydrophobic blocks are activated and fill the already formed pores, achieving pore closure and ultimately forming a dense layer on the surface of the hollow fiber. Throughout the process, the overall porosity of the hollow fiber membrane and the thickness of the dense layer can be adjusted by regulating the degree of swelling of the hydrophilic blocks and the degree of pore closure of the hydrophobic blocks, thereby controlling the gas separation performance of the hollow fiber and achieving good gas permeation rate and gas selectivity. Compared with other existing methods, this method not only uses simple raw materials and requires no auxiliary components, but also uses good solvents for both hydrophilic and hydrophobic blocks that can be reused. It is an environmentally friendly and convenient membrane preparation method that can be used for large-scale industrial production of asymmetric hollow fiber membranes. Attached Figure Description

[0032] Figure 1 This is a SEM image of the outer surface of the block copolymer hollow fiber membrane obtained in Example 2.

[0033] Figure 2 This is a SEM image of the inner surface of the block copolymer hollow fiber membrane obtained in Example 2.

[0034] Figure 3 This is a low-magnification SEM image of the cross-section of the block copolymer hollow fiber membrane obtained in Example 2.

[0035] Figure 4 This is a high-magnification SEM image of the cross-section of the block copolymer hollow fiber membrane obtained in Example 2.

[0036] Figure 5 This is a cross-sectional SEM image of the block polymer hollow fiber membrane obtained in Comparative Example 4.

[0037] Figure 6 This is a SEM image of the outer surface of the block copolymer hollow fiber membrane obtained in Comparative Example 5.

[0038] Figure 7 This is a SEM image of the inner surface of the block copolymer hollow fiber membrane obtained in Comparative Example 5.

[0039] Figure 8 This is a low-magnification SEM image of the cross-section of the block copolymer hollow fiber membrane obtained in Comparative Example 5.

[0040] Figure 9 This is a high-magnification SEM image of the cross-section of the block copolymer hollow fiber membrane obtained in Comparative Example 5.

[0041] Figure 10 This demonstrates the change in porosity of asymmetric hollow fiber membranes with acetone solution concentration and treatment time when closed-cell treatment is performed using PSF block solvent (acetone solution) in the method of the present invention.

[0042] Figure 11 This demonstrates the changes in CO2 permeation rate and CO2 / N2 gas selectivity of asymmetric hollow fiber membranes with varying acetone solution concentration and treatment time when using PSF block solvent (acetone solution) for closed-cell treatment in the method of this invention. Detailed Implementation

[0043] This invention provides a method for preparing asymmetric hollow fiber gas separation membranes, based on selective swelling, selective pore closure, and melt spinning, comprising: 1) Using amphiphilic block copolymers as film-forming materials, nascent hollow fibers are prepared from polymers by melt spinning; The amphiphilic block copolymer is composed of hydrophobic block A and hydrophilic block B (AB, ABA), wherein the hydrophobic block A is selected from any one of polysulfone (PSF), polyethersulfone (PES), and polystyrene (PS), and the hydrophilic block B is selected from any one of polyethylene glycol (PEG), poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). The total molecular weight of the amphiphilic block copolymer is 50,000-500,000 Daltons. In a preferred embodiment, hydrophobic block A is PSF and hydrophilic block B is PEG, or hydrophobic block A is PS and hydrophilic block B is P2VP, or hydrophobic block A is PS and hydrophilic block B is PDMAEMA. In a further preferred embodiment, the amphiphilic block copolymer has a molecular weight of PSF. 70 -PEG 20 PSF 65 -PEG 30 PSF 55 -PEG 40 PES 78 -PEG 19 PS 55 -P2VP 18.5 PS 55 -PDMAEMA 20 PS 60 -P4VP 15 PSF 30 -PEG 25 -PSF 30 PSF 25 -PEG 35 -PSF 25 The unit is kilodaltons.

[0044] The melt spinning process specifically involves melting an amphiphilic block copolymer and then using a single-screw or twin-screw extruder to produce thicker hollow fibers through a spinneret. The melting temperature is 100-210℃, preferably 170-180℃. The spinneret size can range from 0.5 / 0.28 / 0.15mm to 1.4 / 0.9 / 0.6mm, and the film thickness exiting the spinneret can range from 80 to 300μm.

[0045] 2) Immerse the hollow fiber obtained in 1) in a good solvent (selective solvent) of hydrophilic block B, and treat it in a water bath at 55-70℃ for 0.5-5h, so that the hydrophilic block B swells under the action of the solvent to form a pore structure; after the treatment, put it into a cleaning solvent and immerse it for 0.5-3h to clean off the residual selective solvent on the surface, and dry it to obtain a hollow fiber with a porous structure with continuous open pores. The selective solvent of the hydrophilic block B is a mixed solvent composed of n-propanol and a first polar solvent, wherein the proportion of the first polar solvent in the mixed solvent is 0-50 wt%; more preferably, the proportion of the first polar solvent in the mixed solvent is 10-25 wt%; the first polar solvent is further selected from any one of acetone, tetrahydrofuran, or toluene, namely a mixed solvent of n-propanol and acetone, a mixed solvent of n-propanol and tetrahydrofuran, or a mixed solvent of n-propanol and toluene; most preferably, a mixed solvent of n-propanol and acetone containing 20 wt% acetone, a mixed solution of n-propanol containing 20 wt% tetrahydrofuran, or a mixed solution of n-propanol containing 10 wt% toluene.

[0046] The cleaning solvent is a long-chain alkane solvent, which may be selected from any one or a mixture of two or more of n-pentane, n-hexane, n-heptane, n-octane, n-nonane or n-decane; preferably n-heptane.

[0047] 3) Allow only the outer surface of the hollow fiber obtained in 2) to fully contact the closed-pore solvent (i.e., the good solvent of the hydrophobic block A). For example, after sealing both ends of the hollow fiber, immerse it in the closed-pore solvent at room temperature for 0.5-3 hours to allow the hydrophobic block A to move and fill the pores previously formed on the surface of the hollow fiber membrane, thereby creating closed pores on the membrane surface and forming a dense separation layer. Finally, a hollow fiber membrane with an ultra-thin dense layer on the surface and a porous layer inside is obtained.

[0048] The closed-cell solvent is a good solvent for hydrophobic block A, and can be a mixture of a second polar solvent and water or an alcohol. The second polar solvent can be selected from any one of acetone, toluene, xylene or a mixture thereof as a diluent, preferably acetone; more preferably, acetone accounts for 50-99 wt% of the closed-cell solvent; the most preferred closed-cell solvent is a mixed solution of acetone and water, wherein the acetone content is 60-70 wt%.

[0049] The asymmetric hollow fiber gas separation membrane provided by this invention is made from a single material. Compared with the asymmetric hollow fiber membranes prepared by using multiple raw materials through co-extrusion or surface coating in the prior art, it has more ideal performance, including good gas separation performance and mechanical properties.

[0050] Regarding the gas separation performance of the membrane, since the dense layer of the asymmetric hollow fiber membrane of this invention is formed by hydrophobic blocks in an amphiphilic block copolymer filling the surface pores, compared with the surface coating and co-extrusion methods in the prior art, the dense layer is composed of smaller polymer blocks, and its thickness and porosity are easier to control to achieve the ideal state. Through extensive screening experiments, the inventors discovered that when using a good solvent with hydrophobic blocks for pore-closure treatment, the interaction parameters between the hydrophobic blocks and the pore-closure solvent must be within a specific range to obtain a good pore-closure effect. This results in a thinner dense layer forming on the surface of the hollow fiber membrane, significantly improving gas permeability while maintaining essentially unchanged gas selectivity. Taking a hollow fiber membrane prepared from polysulfone / polyethylene glycol as an example, after screening more than 30 existing solvents, the inventors found that acetone solution is the best choice for pore-closure. Using an acetone solution with an interaction parameter between the polysulfone block and the acetone block of 0.4 to 0.5 for pore-closure treatment forms a thinner dense layer on the surface of the original permeable porous membrane than other solvent treatments. Based on this, the concentration of the acetone solution and the treatment time both affect the performance of the asymmetric hollow fiber membrane gas separation membrane after closed-pore treatment. Experiments have shown that, for example... Figure 10 , Figure 11 As shown, if the treatment time remains constant at 0.5 h, and the acetone concentration increases from 50% to 70%, the membrane porosity decreases from 43.2% to 41.4%, the CO2 permeation flux decreases from 42.4 GPU to 37.5 GPU, and the gas selectivity increases from 11.6 to 12.5. Although some pores on the membrane surface close, the hollow fiber membrane still retains a large number of pore structures. If the treatment time remains constant at 1 h, and the acetone concentration increases from 50% to 70%, the membrane porosity decreases from 42.5% to 38.5%, the CO2 permeation flux decreases from 38 GPU to 22.3 GPU, and the gas selectivity increases from 12.4 to 15.2. If the acetone solution concentration remains constant at 70%, and the treatment time increases from 0.5 h to 1 h, the membrane porosity decreases from 42.1% to 38.6%, indicating that increasing the pore closure time reduces the number of pores on the membrane surface and increases the thickness of the dense layer.

[0051] Regarding the mechanical properties of the membrane, since the raw material of the asymmetric hollow fiber gas separation membrane of this invention is a single substance, it not only avoids the problem of poor bonding force between two or more materials in hollow fiber membranes prepared by surface coating and co-extrusion methods in the prior art, but also verifies through experiments that after simple room temperature immersion treatment with a hydrophobic block solvent using the method of this invention, the overall tensile strength and elongation at break of the membrane are quite ideal. Taking the hollow fiber membrane prepared by polysulfone / polyethylene glycol as an example, the tensile strength can reach 10±1 MPa.

[0052] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0053] Example 1 Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 h, and then transferred to n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 50 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.46), treated at room temperature for 0.5 h, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0054] The asymmetric block copolymer hollow fiber membrane prepared in this embodiment has a dense layer thickness of 6.8 μm, a membrane porosity of 43.2%, and some pores on the membrane surface are closed, but a large number of pore structures still exist in the inner layer; the CO2 permeation rate is 42.4 GPU, and the CO2 / N2 gas selectivity is 11.6.

[0055] Example 2 Add 30g of PSF 70 -PEG 20Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 50 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.46), treated at room temperature for 1 hour, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0056] Figure 1 , Figure 2 , Figure 3 , Figure 4 The figures show SEM images of the outer and inner surfaces of the asymmetric hollow fiber membrane prepared in this embodiment at the same magnification, and cross-sectional SEM images at different magnifications. As can be seen from the figures, the outer surface of the polysulfone / polyethylene glycol hollow fiber membrane after the closed-cell treatment is relatively dense, with some cross-sections forming a dense layer structure. Most of the membrane still retains a good open-cell structure with small pore sizes and high porosity. The wall thickness of the polysulfone / polyethylene glycol asymmetric hollow fiber membrane after the closed-cell treatment is approximately 247 μm, which is smaller than that of the hollow fiber membrane treated with PEG solvent swelling for opening pores but not with PSF solvent for closing pores.

[0057] Example 3 Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 60 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.44), treated at room temperature for 0.5 hours, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0058] Compared with Example 1, this embodiment uses a polysulfone solvent with a lower interaction parameter with polysulfone as a pore-closing agent. Under the same treatment time, the porosity of the membrane is slightly increased. Some pores on the membrane surface are closed, but a large number of pore structures still exist in the inner layer. The thickness of the dense layer of the prepared asymmetric block copolymer hollow fiber membrane is 5.6 μm, the CO2 permeation rate is 43.2 GPU, and the CO2 / N2 gas selectivity is 11.8.

[0059] Example 4 Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 60 wt% acetone (the interaction parameter between the solvent and polysulfone is approximately 0.44), treated at room temperature for 1 hour, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0060] Compared with Example 2, this embodiment uses a polysulfone solvent with a lower interaction parameter with polysulfone as the pore-closing agent, and the treatment time is the same, resulting in a slight decrease in membrane porosity. Compared with Example 3, the same polysulfone solvent is used as the pore-closing agent, but the treatment time is longer, resulting in a significant decrease in membrane porosity. Some pores on the membrane surface are closed, but a large number of pore structures still exist in the inner layer. The thickness of the dense layer of the prepared asymmetric block copolymer hollow fiber membrane is 7.8 μm, the CO2 permeation rate is 34.2 GPU, and the CO2 / CH4 gas selectivity is 13.2.

[0061] Example 5 Add 30g of PSF 70 -PEG 20Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 70 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.41), treated at room temperature for 0.5 hours, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0062] Compared with Example 1, this embodiment uses a polysulfone solvent with a lower interaction parameter with polysulfone as a pore-closing agent. The treatment time is the same, and the porosity of the membrane is significantly reduced. Some pores on the membrane surface are closed, but a large number of pore structures still exist in the inner layer. The thickness of the dense layer of the prepared asymmetric block copolymer hollow fiber membrane is 6.1 μm, the membrane porosity is 41%~42%, the CO2 permeation rate is 37.5 GPU, and the CO2 / N2 gas selectivity is 12.5.

[0063] Example 6 Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C, and the resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35). The mixture was treated in a 65°C water bath for 1 hour, followed by treatment in n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 70 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.41) and treated at room temperature for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0064] Compared with Examples 2 and 4, this embodiment uses a polysulfone solvent with a lower interaction parameter with polysulfone as the pore-closing agent, and with the same treatment time, the membrane porosity is significantly reduced. Compared with Example 5, the same polysulfone solvent is used as the pore-closing agent, but the treatment time is longer, and the membrane porosity is significantly reduced. Some pores on the membrane surface are closed, but a large number of pore structures still exist in the inner layer. The thickness of the dense layer of the prepared asymmetric block copolymer hollow fiber membrane is 9.7 μm, the membrane porosity is 38.6%, the CO2 permeation rate is 22.3 GPU, and the CO2 / CH4 gas selectivity is 15.2.

[0065] Example 7 30g of PS 55 -P2VP 18.5 Block copolymers were added to a twin-screw extruder and melted at 180 / 190°C. The melt was then extruded through a spinneret at 180°C, and the resulting hollow fibers were immersed in ethanol (the interaction parameter between this mixed solvent and poly(2-vinylpyridine) is less than 0.5), treated in a 70°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 70 wt% acetone (the interaction parameter between this mixed solvent and PS is less than 0.5), treated at room temperature for 1 hour, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0066] Example 8 30g of PS 55 -PDMAEMA 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C, and the resulting hollow fibers were immersed in ethanol (the interaction parameter between this mixed solvent and PDMAEMA is less than 0.5), treated in a 70°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 70 wt% acetone (the interaction parameter between this mixed solvent and PS is less than 0.5), treated at room temperature for 1 hour, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0067] Comparative Example 1 Hollow fiber membranes were prepared according to the method described in Example 1, and pore-closure treatment was performed using pure acetone solvent. The specific procedure is as follows: Add 30g of PSF 70 -PEG20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C, and the resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone. The mixture was treated in a 65°C water bath for 1 h, followed by treatment in n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in pure acetone (the interaction parameter between this solvent and polysulfone is 0.34) and treated at room temperature for 1 min. The fiber structure ruptured, and the hollow shape could not be maintained.

[0068] Compared with Example 1, although both examples used acetone solution as a pore-closing agent, the interaction parameter between the pure acetone solution and polysulfone was too small, resulting in excessive affinity for polysulfone. The membrane structure ruptured after only 1 minute of pore-closing treatment, making it impossible to complete the preparation of the asymmetric hollow fiber membrane.

[0069] Comparative Example 2 Hollow fiber membranes were prepared according to the method described in Example 1, with the pore-closure treatment time increased. The specific method is as follows: Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone and treated in a 65°C water bath for 1 h, followed by treatment in n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 50 wt% acetone and treated at room temperature for 5 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0070] The asymmetric block copolymer hollow fiber membrane prepared in this comparative example had surface defects due to excessively long pore-closure treatment time, and the membrane could not maintain a good hollow structure.

[0071] Comparative Example 3 Hollow fiber membranes were prepared according to the method described in Example 1, and closed-cell treatment was performed using other solvents with an interaction parameter greater than 0.5 with polysulfone. The specific scheme is as follows: Add 30g of PSF 70 -PEG 20Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C, and the resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone. The mixture was treated in a 65°C water bath for 1 h, followed by treatment in n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the hollow fibers were then sealed with hot melt adhesive, and the sealed fibers were immersed in a mixed solvent of ethanol and water containing 50 wt% ethanol (the solubility parameter of this mixed solvent with PSF was greater than 0.5). The mixture was treated at room temperature for 5 h, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain a hollow fiber membrane.

[0072] The block copolymer hollow fiber membrane prepared in this comparative example did not form a continuous dense layer on the surface of the hollow fiber membrane even after 5 h of treatment because a solvent with an excessively high interaction parameter with PSF was used for pore-closure treatment. The CO2 permeation rate was 22500 GPU and the CO2 / N2 gas selectivity was 1.2.

[0073] Comparative Example 4 Hollow fiber membranes were prepared according to the method described in Example 1, and pore-closure treatment was performed using other solvents (with an interaction parameter with PSF of less than 0.5). The specific scheme is as follows: 50 kg of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone, treated in a 65°C water bath for 1 min, and then transferred to n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the hollow fibers were then sealed with hot melt adhesive, and the sealed hollow fibers were immersed in a mixed solvent of toluene and water containing 50 wt% toluene (the solubility parameter of this mixed solvent with PSF was 0.34). The mixture was treated at room temperature for 0.5 h, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain a hollow fiber membrane.

[0074] Figure 5 The cross-section of the asymmetric hollow fiber membrane prepared for this comparative example shows that the membrane cannot maintain a good structure and the fibers break.

[0075] Comparative Example 5 Hollow fiber membranes were prepared according to the method described in Example 1, without any pore-closure treatment. The specific method is as follows: Add 30 g of PSF 70 -PEG 20The block copolymer was added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone, and treated in a water bath at 65°C for 1 hour. Afterward, they were transferred to n-heptane for another 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain a hollow fiber membrane.

[0076] Figure 6 , Figure 7 , Figure 8 , Figure 9 The figures show SEM images of the outer and inner surfaces of the hollow fiber membrane prepared in this embodiment, as well as cross-sectional SEM images at different magnifications. As can be seen from the figures, the polysulfone / polyethylene glycol hollow fiber membrane, after selective swelling and pore-opening treatment using PEG as a good solvent, exhibits a double continuous open-pore structure on its outer surface, lacks a dense layer in its cross-section, has high porosity, and is not an asymmetric structure.

[0077] The block copolymer hollow fiber membrane prepared in this embodiment did not form a continuous dense layer, the CO2 permeation rate was 24509 GPU, and the CO2 / N2 gas selectivity was 1.4.

[0078] Compared with Example 1, it can be seen that using the same melt spinning temperature, good solvent, and swelling time, without treatment with a pore-closing agent, a dense separation layer cannot be obtained, the gas permeation rate will increase significantly, and there will be virtually no gas selectivity.

[0079] Comparative Example 6 Hollow fiber membranes are prepared according to the method described in Example 1, reducing the pore-closure treatment time. The specific scheme is as follows: Add 30g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone (the interaction parameter between this mixed solvent and polyethylene glycol is approximately 0.35), treated in a 65°C water bath for 1 hour, and then transferred to n-heptane for 1 hour. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of acetone and water containing 50 wt% acetone (the interaction parameter between this mixed solvent and polysulfone is approximately 0.46), treated at room temperature for 20 minutes, and immediately after treatment, removed and dried at 40°C to obtain an asymmetric hollow fiber membrane.

[0080] The block copolymer hollow fiber membrane prepared in this comparative example did not form a continuous dense layer, the CO2 permeation rate was 227.5 GPU, and the CO2 / N2 gas selectivity was 6.8.

[0081] Compared with Example 1, it can be seen that when using the same melt spinning temperature, good solvent, and swelling time, and the treatment time of the pore-closing agent is less than 30 min, some pores still exist on the outer surface of the membrane, and a dense and continuous separation layer cannot be obtained. The gas permeation rate is faster and the gas selectivity is lower.

[0082] Comparative Example 7 Hollow fiber membranes were prepared according to the method described in Example 1, and pore-closure treatment was performed using other solvents (with an interaction parameter with PSF of less than 0.5). The specific scheme is as follows: Add 30 g of PSF 70 -PEG 20 Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone, treated in a 65°C water bath for 1 min, and then transferred to n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the hollow fibers were then sealed with hot melt adhesive, and the sealed hollow fibers were immersed in a mixed solvent of xylene and water containing 50 wt% xylene (the solubility parameter of this mixed solvent with PSF was less than 0.4). The mixture was treated at room temperature for 0.5 h, and immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain a hollow fiber membrane.

[0083] Compared with Example 1, it can be seen that when using the same melt spinning temperature and swelling time, but using a solvent with a very small interaction parameter with PSF (less than 0.4) for closed-cell treatment, the membrane cannot maintain a good structure, and the resulting fibers will break.

[0084] Comparative Example 8 Hollow fiber membranes were prepared according to the method described in Example 1, and pore-closure treatment was performed using other solvents (with an interaction parameter with PSF of less than 0.5). The specific scheme is as follows: Add 30 g of PSF 70 -PEG 20Block copolymers were added to a twin-screw extruder and melted at 170 / 180°C. The melt was then extruded through a spinneret at 170°C. The resulting hollow fibers were immersed in a mixed solvent of n-propanol and acetone containing 20 wt% acetone, treated in a 65°C water bath for 1 min, and then transferred to n-heptane for 1 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C. The ends of the resulting hollow fibers were then sealed with hot melt adhesive. The sealed hollow fibers were immersed in a mixed solvent of dimethyl sulfoxide (DMSO) and water containing 50 wt% DMSO (the solubility parameter of this mixed solvent with PSF is less than 0.4). The mixture was treated at room temperature for 0.5 h. Immediately after treatment, the hollow fibers were removed and dried at 40°C to obtain a hollow fiber membrane.

[0085] Compared with Example 1, it can be seen that when using the same melt spinning temperature and swelling time, but using a solvent with a very small interaction parameter with PSF (less than 0.4) for closed-cell treatment, the membrane cannot maintain a good structure, and the resulting fibers will break.

[0086] Experimental Example Asymmetric hollow fiber membranes were prepared according to the methods in Examples 1-6, and the tensile properties of the hollow fiber membranes were tested before and after selective swelling treatment with a good solvent of PEG, and after pore-closure treatment with a good solvent of PSF.

[0087] The test results show that: ① Before swelling, the dense nascent hollow fiber membrane exhibits high tensile strength (25±3 MPa). This is because the hollow fiber matrix composed of PSF with superior mechanical properties ensures the high strength of the fiber; the highly flexible PEG segments can move freely, thus ensuring the extensibility of the hollow fiber; giving the hollow fiber membrane a high elongation. ② After swelling, the tensile strength of the hollow fiber membrane is relatively low. After closing the pores, due to the presence of the dense layer, its tensile strength is restored to a certain extent, reaching about 10 MPa, which is higher than the tensile strength of hollow fiber membranes formed by methods such as NIPS. Thus, it avoids the problems of poor bonding caused by surface coating, blending extrusion and other methods in the existing technology.

Claims

1. An asymmetric hollow fiber gas separation membrane, characterized in that: Made of an amphiphilic block copolymer; comprising an inner porous layer and an outer dense layer; the pores inside the porous layer are formed by hydrophilic blocks of the amphiphilic block copolymer, and the dense layer is formed by hydrophobic blocks of the amphiphilic block copolymer filling the surface pores; the amphiphilic block copolymer is composed of hydrophobic block A and hydrophilic block B, wherein the hydrophobic block A is selected from any one of polysulfone (PSF), polyethersulfone (PES), and polystyrene (PS), and the hydrophilic block B is selected from any one of polyethylene glycol (PEG), poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), and poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA).

2. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The amphiphilic block copolymer is composed of hydrophobic block A and hydrophilic block B, wherein the hydrophobic block A is PSF and the hydrophilic block B is PEG, or the hydrophobic block A is PS and the hydrophilic block B is P2VP, or the hydrophobic block A is PS and the hydrophilic block B is PDMAEMA.

3. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The thickness of the dense layer of the asymmetric hollow fiber gas separation membrane is 0.5-12 μm.

4. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The thickness of the dense layer of the asymmetric hollow fiber gas separation membrane is 5-10 μm.

5. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The thickness of the dense layer of the asymmetric hollow fiber gas separation membrane is 6-7 μm.

6. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The dense layer pore size distribution of the asymmetric hollow fiber gas separation membrane is less than 0.5 nm.

7. The asymmetric hollow fiber gas separation membrane according to claim 1, characterized in that: The porous layer of the asymmetric hollow fiber gas separation membrane has a porosity of 10%-60% and a pore size range of 15-20 nm.

8. A method for preparing an asymmetric hollow fiber gas separation membrane, comprising: Nascent hollow fibers are prepared using an amphiphilic block copolymer containing hydrophobic block A and hydrophilic block B as raw material. The nascent hollow fibers are first immersed in a good solvent containing hydrophilic block B to treat them, causing the hydrophilic block B to swell and form channels. After washing away the good solvent containing hydrophilic block B, the hollow fibers are allowed to fully contact only the outer surface with the good solvent containing hydrophobic block A, promoting the movement of hydrophobic block A on the surface of the hollow fibers, filling the surface channels, and forming a dense layer. The interaction parameter between the good solvent containing hydrophilic block B and hydrophilic block B is less than 0.5; the interaction parameter between the good solvent containing hydrophobic block A and hydrophobic block A is less than 0.5 and greater than 0.

4.

9. The method of claim 8, characterized in that, The interaction parameter between the good solvent of the hydrophilic block B and the hydrophilic block B is less than 0.4 and greater than 0.

3.

10. The method of claim 8, characterized in that, The interaction parameter between the good solvent of the hydrophilic block B and the hydrophilic block B is between 0.34 and 0.

36.

11. The method of claim 8, characterized in that, The interaction parameter between the good solvent of the hydrophobic block A and the hydrophobic block A is between 0.41 and 0.

46.

12. The method according to any one of claims 8-11, characterized in that: The nascent hollow fibers are treated by immersing them in a good solvent of hydrophilic block B at 55-70°C for 0.5-5 hours.

13. The method according to any one of claims 8-11, characterized in that: The nascent hollow fibers are treated by immersing them in a good solvent of hydrophilic block B at 65-70°C for 1-3 hours.

14. The method according to any one of claims 8-11, characterized in that: The good solvent for washing away the hydrophilic block B is to soak the hollow fiber in a long-chain alkane solvent at room temperature for 0.5-3 hours.

15. The method according to any one of claims 8-11, characterized in that: The good solvent for washing away the hydrophilic block B is to soak the hollow fiber in a long-chain alkane solvent at room temperature for 1-2 hours.

16. The method according to any one of claims 8-11, characterized in that: Hollow fibers are treated by immersing them in a good solvent containing hydrophobic block A at room temperature for 0.5-3 hours.

17. The method according to any one of claims 8-11, characterized in that: Hollow fibers are treated by immersing them in a good solvent of hydrophobic block A at room temperature for 0.5-1 h.

18. The method according to any one of claims 8-11, characterized in that: The hydrophilic block B and hydrophobic block A are PEG and PSF, respectively. The good solvent for the hydrophilic block B is selected from a mixed solvent composed of n-propanol and a first polar solvent. The first polar solvent is selected from any one of acetone, tetrahydrofuran, or toluene, and the mass ratio of the first polar solvent is controlled to be no more than 50%. The good solvent for the hydrophobic block A is selected from a mixture of a second polar solvent and water or an alcohol. The second polar solvent is selected from any one of acetone, toluene, or xylene, and the weight ratio of the second polar solvent is controlled to be no less than 50%.

19. The method of claim 18, characterized in that: The acetone content in the good solvent of the hydrophobic block A is 50-70 wt%, and the treatment time using the good solvent of the hydrophobic block A is 0.5-3h.

20. The method of claim 18, characterized in that: The good solvent for the hydrophobic block A is a mixed solution of acetone and water with an acetone content of 60-70 wt%, and the treatment time using the mixed solution of acetone and water is 0.5-1 h.

21. The application of the asymmetric hollow fiber gas separation membrane according to any one of claims 1-7 in CO2 / N2 separation or CO2 / CH4 separation.

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