An aromatic polyamide-imide hollow fiber gas separation membrane, a preparation method and applications

Abstract

The application discloses an aromatic polyamide-imide (PAI) hollow fiber gas separation membrane, a preparation method and application. The separation membrane is prepared by copolymerization of three kinds of aromatic dianhydride, aromatic dichloroacyl and aromatic diamine monomers. The polymer has high water vapor transmission rate and selectivity, and has excellent mechanical strength and hydrolysis stability. Meanwhile, the hollow fiber gas separation membrane is a kind of asymmetric structure including a skin layer (selective layer) and a porous layer (supporting layer). The asymmetric structure of the sparse porous layer is beneficial to the rapid passing of the gas, and the dense skin layer increases the selective permeability of the gas.

Description

Technical Field

[0001] This invention relates to an aromatic polyamide-imide (PAI) hollow fiber gas separation membrane, its preparation method, and its application, belonging to the fields of polymer materials and gas separation membranes. Background Technology

[0002] In real life and industrial production, the removal of water vapor through polymer barrier materials or membranes is of great significance. Applications include natural gas drying, coal drying, protective clothing, packaging materials, roofing membranes, and humidity control in enclosed spaces (air conditioning in buildings, aviation, and aerospace). For example, coal-fired power plants generate large amounts of flue gas by burning coal, primarily containing N2, O2, CO2, and water vapor, but also substances such as nitric oxide (NO). x Pollutants such as sulfur dioxide (SO2) and fly ash are present in the flue gas. Due to the gas cleaning process, the temperature of the flue gas decreases, and the gas stream becomes saturated with water vapor, which easily leads to condensation of water vapor in the equipment, causing corrosion problems. To prevent condensation, the flue gas stream needs to be reheated, resulting in additional energy consumption and costs. Membrane technology can dehumidify at room temperature, eliminating the need for reheating and saving resources and costs. (Journal of Membrane Science 313(2008)263–276); During natural gas transportation, water vapor in the natural gas may condense, forming hydrates that clog pipelines and equipment. Furthermore, the presence of acidic impurities H2S and CO2 exacerbates corrosion of pipelines and equipment. Therefore, natural gas needs to be dehumidified before transportation (Angew. Chem. Int. Ed. 2016, 55, 13754–13758); Removing water vapor from humid air is an energy-intensive process, and heating, ventilation, and air conditioning (HVAC) systems are essential in our daily lives. However, the energy consumption is enormous, and the global demand for HVAC is constantly increasing. In the United States, residential and commercial buildings consume over 76% of total electricity and approximately 35% of total energy for HVAC (Journal of Membrane Science, 621, 2021, 119006, 0376-7388). Furthermore, over 90% of current air cooling and dehumidification relies on vapor compression systems using synthetic materials and refrigerants such as hydrofluorocarbons (HFCs), both of which are greenhouse gases. The high energy consumption of current HVAC systems and their adverse environmental impact urgently necessitate the development of next-generation HVAC technologies.

[0003] Membrane-based air dehumidification is characterized by low energy consumption, simple operation, and small footprint. It is an isothermal system that separates water vapor from the air without requiring energy-intensive subcooling and reheating steps. Polymer membranes are the preferred choice for air dehumidification because they are inexpensive, defect-free, easy to scale up, and have excellent mechanical properties. The selected membranes typically have hydrophilic portions to enhance water solubility and promote preferential water permeation.

[0004] Currently, most gas separation membranes used for air dehumidification are made of polymer materials. These polymer membranes generally cannot simultaneously possess high selectivity and permeability; high-permeability polymer membranes often have low selectivity. To manufacture gas separation membranes with both high selectivity and high permeability, polymers are typically fabricated into hollow fiber gas separation membranes. These membranes feature an asymmetric structure consisting of a skin layer (selective layer) and a porous layer (support layer). Their advantage lies in reducing the thickness of the permeable gas through the membrane, thereby reducing permeation resistance and achieving high gas permeability. Simultaneously, the dense skin layer also enhances the membrane's selectivity; this structure combines the selectivity and permeability of polymer membranes. Moreover, compared to other membrane structures, hollow fiber membranes improve gas separation efficiency and reduce costs because their large specific surface area provides a wider range of gas transport (Chemosphere, 303, Part 1, 2022, 134959, 0045-6535).

[0005] Many polymers can be used as selective membranes or barrier membranes for transporting water vapor in gas separation. Aromatic polyimides, in particular, formed by the condensation polymerization of aromatic dianhydrides and diamine monomers, possess excellent heat resistance and mechanical strength due to the presence of aromatic ring structures in their molecular backbone. They also exhibit good chemical stability and excellent solvent resistance, making them suitable for fabricating self-supporting asymmetric hollow fiber membranes with high permeability (Angew. Chem. Int. Ed. 2020, 59, 14877–14883). Hollow fiber gas separation membranes made of polyimides not only have excellent permeability but also good chemical stability, high heat resistance, and good mechanical properties. They are commonly used for the separation of various gas pairs (such as H2 / N2, N2 / O2, CO2 / N2, CO2 / CH4, etc.) to remove moisture from air, hydrocarbon feed gases, and alcohols, exhibiting excellent dehumidification performance.

[0006] For gas separation membranes prepared by copolymerizing different monomers to form polyimides, CN113731198A discloses a method for preparing a highly selective polyimide gas separation membrane. First, a diamine monomer 6FDAP containing both trifluoromethyl and hydroxyl groups is synthesized through a two-step organic synthesis. Then, three polyimides are synthesized by chemical imidization with different dianhydrides. It is noted that this gas separation membrane not only has excellent thermal stability but also high selectivity for CO2 / CH4. CN112275147B discloses a self-polymerizing microporous polyimide gas separation membrane, indicating that it has good thermal stability and mechanical properties and high selectivity for O2 / N2. CN110433672B discloses a non-coplanar, sterically hindered polyimide gas separation membrane, indicating that it combines high permeability and high selectivity with good film-forming properties. However, these disclosures do not fabricate hollow fiber structures for the polymer gas separation membranes, and the manufacturing processes are complex, making them unsuitable for large-scale applications.

[0007] For dehumidification membranes, water resistance and hot water resistance are crucial properties, affecting their overall performance and lifespan. Most gas separation membranes used for dehumidification often exhibit poor water and hot water resistance. Although traditional polyimide membranes have good thermal stability, their easily hydrolyzed imide ring structure makes them prone to hydrolysis after immersion in high-temperature water, resulting in significant performance loss and poor hot water resistance.

[0008] To synthesize a hollow fiber gas separation membrane with excellent performance for dehumidification to meet practical applications in daily life and industry, this invention uses at least two or more different aromatic monomers to copolymerize and form aromatic polyamide-imide (PAI) to prepare an asymmetric gas separation membrane. By controlling the copolymerization of monomers with different functional group structures, a gas separation membrane with high permeability and high selectivity is produced. This gas separation membrane also exhibits excellent mechanical properties and hydrolytic stability. Summary of the Invention

[0009] The present invention aims to provide an aromatic polyamide-imide (PAI) hollow fiber gas separation membrane, its preparation method, and its application. The invention utilizes a fluorinated aromatic dianhydride and an aromatic diacyl chloride, copolymerizing these two monomers with different aromatic diamine monomers via an amide-imide condensation reaction to obtain an aromatic polyamide-imide with good permeability, selectivity, excellent mechanical properties, and hydrolytic stability. This polyamide-imide is then applied to hollow fiber gas separation membranes to improve the polymer's dehumidification performance.

[0010] The hollow fiber gas separation membrane in the present invention has an asymmetric structure including a skin layer (selective layer) and a porous layer (support layer). The porous layer with such an asymmetric structure facilitates the rapid passage of gas, while the dense skin layer increases the selective permeability of the gas. At the same time, the aromatic polyamide-imide in the present invention has an amide bond and a benzene ring in its main chain, having strong structural stability. The fluorine-containing functional group on the polymer main chain has hydrophobicity, achieving good water resistance stability. Moreover, by introducing an amide bond into the polymer structure, the amide bond can form hydrogen bonds with strong interaction forces with water molecules, enabling the rapid adsorption of water vapor through the membrane. Meanwhile, the presence of the amide bond also enhances the mechanical properties and hydrolysis resistance stability of the polymer.

[0011] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0012] The aromatic polyamide-imide hollow fiber gas separation membrane of the present invention, the hollow fiber gas separation membrane is made of aromatic polyamide-imide, and the structural general formula of the aromatic polyamide-imide is as follows:

[0013]

[0014] R1 is the aromatic unit structure of aromatic diamine, R2 is the aromatic unit structure of aromatic dianhydride, and R3 is the aromatic unit structure of aromatic diacyl chloride; where X and Y are the molar percentages of the R2 and R3 parts in the polymer respectively, X + Y = 100, 0 < X < 100, 0 < Y < 100. n represents the degree of polymerization, and n is a positive integer from 10 to 200. The weight average molecular weight of the aromatic polyamide-imide is between 5000 and 800000.

[0015] Further, X and Y are the molar percentages of the R2 and R3 parts in the polymer respectively, 0 < X < 100, and X is preferably 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 99. 0 < Y < 100, and Y is preferably 99, 95, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45, 40, 35, 30, 25, 20, 15 or 1.

[0016] Further, n is 10, 15, 20, 25, 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 110, 120, 130, 140, 150, 160, 170, 180, 190 or 200.

[0017] Further, the weight-average molecular weight of the aromatic polyamide is 5000, 6000, 7000, 8000, 9000, 10000, 20000, 30000, 40000, 50000, 60000, 70000, 80000, 90000, 100000, 200000, 300000, 400000, 500000, 600000, 700000, or 800000.

[0018] Furthermore, R1 represents one or more of the following structures:

[0019]

[0020] The R1 structure is characterized by a diamine monomer with an aromatic ring structure. This aromatic ring structure enhances the mechanical strength of the polymer. Furthermore, by altering the functional group structure on the aromatic ring, the overall properties of the polymer can be further controlled. For example, introducing halogen functional groups (such as fluorinated substituents) into the polyimide backbone or side chains can increase the free volume, thereby improving gas solubility and permeability, and also increasing the solubility of the polyimide. Due to the high bond energy of the CF bond, polyimide polymers containing fluorinated groups have higher glass transition temperatures, as well as higher heat resistance and tensile strength.

[0021] Furthermore, R2 represents one or more of the following structures:

[0022]

[0023] Furthermore, R3 represents one or more of the following structures:

[0024]

[0025] The preparation method of the aromatic polyamide-imide hollow fiber gas separation membrane as described above includes the following steps:

[0026] (1) Under nitrogen atmosphere and ice bath conditions, add polar solvent to the reaction vessel containing aromatic diamine monomer. After complete dissolution, add aromatic dianhydride monomer in three batches, then add aromatic diacyl chloride monomer. React in cold bath, then add acetic anhydride and trimethylpyridine to catalyze the reaction, and then react at room temperature to obtain the reaction solution.

[0027] (2) The reaction solution was precipitated in methanol solution to obtain fibrous polymer. After washing with methanol, the obtained polymer was vacuum dried to remove excess solvent and obtain dried fibrous polymer.

[0028] (3) Dissolve the dried fibrous polymer in a polar solvent to obtain a polyamide-imide solution;

[0029] (4) The prepared polyamide-imide solution is filtered and extruded through a hollow fiber membrane spinning nozzle. The extruded hollow fiber body is then passed through a nitrogen gas gap to form a skin layer. After that, it is placed in a coagulation bath containing an aqueous ethanol solution to impregnate it into wet fibers. The wet fibers are impregnated in an ethanol solution for solvent removal treatment, and then impregnated in isooctane, dried, and finally heat-treated to obtain a hollow fiber membrane.

[0030] Further, in step (1), the cold bath reaction time is 24 hours, and the reheating time is 2 hours. Preferably, in step (1), the molar amount of the aromatic diamine monomer is the same as the sum of the molar amounts of the aromatic dianhydride monomer and the aromatic diacyl chloride monomer, the molar amount of trimethylpyridine is one times the amount of the diamine monomer, and the molar amount of acetic anhydride is five times the amount of the diamine monomer. Preferably, in step (1), the polar solvent is one or more of NMP, DMF, DMAc, and DMSO. Preferably, in step (1), the concentrations of the aromatic diamine monomer, the aromatic dianhydride monomer, and the aromatic diacyl chloride monomer in the polar solvent in the reaction system are all 15 wt%.

[0031] Furthermore, in step (2), the vacuum drying temperature is 120°C and the vacuum drying time is 12 hours.

[0032] Further, in step (3), the polyamide-imide solution is 15 wt%.

[0033] Further, in step (4), the ethanol concentration in the aqueous ethanol solution is 75-85 wt%; preferably, the wet fiber is immersed in the ethanol solution for 2 hours at 45°C for solvent removal treatment, and then immersed in isooctane for 2.5 hours at 65°C. After completion, it is dried at 120°C for 12 hours, and finally heat-treated at 250°C for 2 hours; preferably, the hollow fiber gas separation membrane has an outer diameter of about 450 μm, an inner diameter of about 300 μm, and a membrane thickness of about 55 μm.

[0034] Application of an aromatic polyamide-imide hollow fiber gas separation membrane as described above, wherein the separation membrane is used for dehumidification; preferably, the separation membrane is used for gas dehumidification; preferably, the separation membrane is used for air dehumidification.

[0035] The production and performance of the hollow fiber gas separation membrane of the present invention will be described in detail below. However, it should be understood that the present invention is by no means limited to these embodiments.

[0036] Preparation of a polyamide-imide solution with a polymer concentration of 15 wt%:

[0037] (1) Under nitrogen atmosphere and ice bath conditions, add polar solvent to a three-necked round-bottom flask containing aromatic diamine monomer. After complete dissolution, add dianhydride in three batches. Weigh out acyl chloride and slowly sprinkle it into the system. After reacting in a cold bath for 12 hours, add acetic anhydride and trimethylpyridine to catalyze the rapid reaction. Continue to react at room temperature for 24 hours. After the reaction is completed, a viscous reaction solution is obtained.

[0038] (2) The viscous reaction solution was precipitated in methanol solution to obtain fibrous polymer. After washing with methanol three times, the obtained polymer was vacuum dried at 120°C for 12 hours to remove excess solvent and obtain dry fibrous polymer.

[0039] (3) The dried fibrous polymer was dissolved in a polar solvent to obtain a 15 wt% polyamide solution. Wherein: the concentration of aromatic diamine monomer, aromatic dianhydride monomer, and aromatic diacyl chloride monomer in the polar solvent in the reaction system is 15 wt%, the molar amount of aromatic diamine monomer is the same as the sum of the molar amounts of the two aromatic dianhydride monomers and the aromatic diacyl chloride monomer, the molar amount of trimethylpyridine is one time the amount of diamine monomer, and the molar amount of acetic anhydride is five times the amount of diamine monomer.

[0040] Production of asymmetric hollow fiber membranes:

[0041] The prepared polyamide-imide solution was filtered through a 380-mesh metal mesh and extruded through a hollow fiber membrane spinning nozzle (spinning nozzle specifications: 1000 μm circular aperture, 200 μm circular slit width, 400 μm central hole diameter). The extruded hollow fiber body was then passed through a nitrogen gas gap to form a dense skin layer; the height of the gap affected the thickness of the skin layer. It was then placed in a coagulation bath containing a 75-85 wt% aqueous ethanol solution to impregnate it into wet fibers. The wet fibers were then impregnated in the ethanol solution at 45°C for 2 hours for solvent removal, followed by impregnation in isooctane at 65°C for 2.5 hours to displace the solvent. After completion, the fibers were dried at 120°C for 12 hours and finally heat-treated at 250°C for 2 hours to obtain a hollow fiber membrane with an outer diameter of approximately 450 μm, an inner diameter of approximately 300 μm, and a membrane thickness of approximately 55 μm.

[0042] The beneficial results of this invention are:

[0043] (1) Synthesizing aromatic polyamide-imide polymers via polycondensation reaction;

[0044] (2) The obtained aromatic polyamide-imide polymer is readily soluble in polar solvents, and the gas separation membrane exhibits good hot water resistance and mechanical properties. After treatment in hot water at 80°C for 120 hours, the elongation at break of the hollow fiber membrane remains at least 95% or higher than before the hot water treatment. The tensile strength of the hollow fiber membrane is 17.5 MPa or higher, and the elongation at break is 10% or higher.

[0045] (3) Water vapor permeation rate of hollow fiber membrane (P^ H2O ) is 2.7 x 10 -3 cm 3 (STP) / cm 2 ·(STP) / cm 2 The ratio of water vapor to nitrogen permeation rate (P^) is approximately cmHg. H2O / P^ N2 The value is around 300, where the helium permeation rate (P^) of the porous layer (support layer) of this membrane is... He The value is 3.1 x l0. -3 cm 3 (STP) / cm 2 With a moisture permeability of approximately 0.5 sec·cmHg, it exhibits excellent water vapor permeability and selectivity, meeting the practical requirements for dehumidification applications. Attached Figure Description

[0046] Figure 1 The gas permeation rate diagram is shown for the polyamide-imide hollow fiber gas separation membrane prepared in Example 1.

[0047] Figure 2 The tensile strength and elongation at break of the polyamide-imide hollow fiber gas separation membrane prepared in Example 1 are shown in the figure.

[0048] Figure 3 Thermogravimetric analysis curve of the polyamide-imide hollow fiber gas separation membrane prepared in Example 1. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following examples are further illustrations of the invention, but not limitations on its scope. The scope of protection of the present invention should include all the contents of the claims, and those skilled in the art can fully implement all the contents of the claims of the present invention through the following description of the embodiments.

[0050] The performance testing method for the hollow fiber membrane in the following embodiments of the present invention is as follows:

[0051] Determination of water vapor permeation performance of hollow fiber membranes

[0052] A permeability evaluation element with an effective length of 20 mm was fabricated using approximately 15 hollow fiber membranes, a stainless steel tube, and an epoxy resin-based adhesive. This element was inserted into a stainless steel container to form a pencil-shaped membrane module. Nitrogen gas with a water vapor content of 1500 ppm was introduced at a fixed rate into the exterior of the hollow fibers of the pencil-shaped module. When a cutoff gas (argon) was introduced at a fixed rate into the permeable side, water vapor separation was achieved, and the water vapor content of the impermeable and permeable gases was measured using a dew point meter. The water vapor permeation rate of this membrane was calculated by measuring the water vapor content (water vapor partial pressure), the input gas rate, and the effective membrane area. This measurement was performed at 50°C.

[0053] Determination of the permeability of hollow fiber membranes to methane, nitrogen, oxygen, hydrogen, and carbon dioxide:

[0054] A permeation performance evaluation element with an effective length of 10 mm was fabricated using approximately 20 fiber membranes, a stainless steel tube, and an epoxy resin-based adhesive. This element was inserted into a stainless steel container to form a pencil-shaped membrane assembly. Methane, nitrogen, oxygen, hydrogen, and carbon dioxide were introduced at fixed pressures, and their permeation rates were measured. The permeation rates of each gas were calculated by measuring the volume of permeated methane, nitrogen, oxygen, hydrogen, and carbon dioxide, the input pressure, and the effective membrane area. This measurement was performed at 50°C.

[0055] Determination of helium permeation performance of porous layers in hollow fiber membranes:

[0056] Multiple hollow fiber membranes were uniformly arranged in a plasma treatment device and subjected to oxygen plasma treatment at an operating voltage of 20V. During plasma treatment, some hollow fiber membranes were removed every 5 minutes to obtain hollow fiber membranes with different treatment times. A pencil-shaped membrane module with an effective length of approximately 10 mm was fabricated according to the above method for gas permeation measurement. Pure nitrogen or pure helium was introduced into the module at a constant volume and pressure, and the permeate fluid volume of each was measured. The permeation rates of nitrogen and helium were calculated by using the measured permeate fluid volume, input pressure, and effective membrane area. The ratio of the helium and nitrogen permeation rates of the hollow fiber membrane after 30 minutes of plasma treatment (P^) is used to determine the permeation rate. He / P^ N2 The helium permeation rate (P0) is not greater than 1.2, therefore, after treating the hollow fiber membrane for 30 minutes, this helium permeation rate (P0) is... He The helium permeation rate of the porous layer of the membrane used in this invention was measured at 50°C.

[0057] Determination of tensile strength and elongation at break of hollow fiber membranes:

[0058] The test was conducted using a tensile testing machine. The effective length of the sample was 20 mm, and the tensile rate was 10 mm / min.

[0059] Measurement of rotational viscosity:

[0060] The rotational viscosity of the polyamide-imide solution was measured at 100°C using a rotational viscometer (rotor shear rate: 1.75 / s).

[0061] Hollow fiber membrane hydrolysis stability test:

[0062] Hollow fiber membranes with known elongation at break were used as samples. These membranes were sealed in a stainless steel container filled with ion-exchanged water. The container was then sealed and placed in an oven at 80°C for 120 hours as a hot water treatment. After the hot water treatment, the hollow fiber membranes were removed from the container and dried in an oven at 120°C. The elongation at break of the dried hollow fiber membranes was measured according to the tensile testing method described above. Water resistance and hot water resistance are expressed as elongation at break retention (%).

[0063] Example 1

[0064] (1) Under nitrogen atmosphere and ice bath conditions, add 100 ml of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) to a three-necked round-bottom flask containing 32.023 g of TFDB. N,N-Dimethylacetamide (DMAc) was completely dissolved and then added in three batches with 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC). The first batch consisted of 16.1815 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA), the second batch consisted of 10.151 g of terephthaloyl chloride (TPC), and the third batch consisted of 6.0305 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA). Finally, the remaining 115 ml of N,N-dimethylacetamide (DMAc) was added. After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the fibrous solid polymer was filtered and then filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%. The molar ratio of 6FDA and TPC in the reaction system was 5:5.

[0065] (2) At room temperature, the above polymer is dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution is 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity is 1860 poise, the weight-average molecular weight of the polyamide solution is between 50,000 and 500,000, and the degree of polymerization n is 10-100. Hollow fiber membranes are produced using this polyamide-imide solution through the aforementioned asymmetric hollow fiber membrane production method. The specific production method is as follows: the prepared polyamide-imide solution is filtered through a metal wire mesh (380 mesh), extruded through a hollow fiber membrane spinning nozzle (spinning nozzle specifications: 1000 μm circular aperture, 200 μm circular slit width, 400 μm central hole diameter), and then the extruded hollow fiber body is passed through a nitrogen gas gap to form a dense skin layer. The height of the gas gap affects the thickness of the skin layer. The fibers were then placed in a coagulation bath containing an aqueous ethanol solution with a concentration of 75-85 wt% to impregnate them into wet fibers. The wet fibers were then impregnated in the ethanol solution at 45°C for 2 hours for solvent removal, followed by impregnation in isooctane at 65°C for 2.5 hours to displace the solvent. After this process, the fibers were dried at 120°C for 12 hours, and finally heat-treated at 250°C for 2 hours to obtain a hollow fiber membrane with an outer diameter of approximately 450 μm, an inner diameter of approximately 300 μm, and a membrane thickness of approximately 55 μm. The gas permeability and mechanical properties of this hollow fiber membrane were measured using the aforementioned method. The results are shown in Table 1. Figure 1 As shown, the benzene rings in the main chain of this aromatic polyamide-imide are tightly packed, resulting in a small free volume within the molecular chain, which isolates gases with larger gas dynamic diameters. Therefore, Figure 1 As the kinetic diameter of various gases increases, the permeability of the membrane decreases sequentially, especially for N2 and CH4, which have relatively large kinetic diameters; therefore, it exhibits very low permeability, achieving a highly efficient air dehumidification effect. Simultaneously, the mechanical properties of this aromatic polyamide-imide hollow fiber membrane were tested, and the test results are as follows: Figure 2 As shown, the aromatic polyamide-imide hollow fiber membrane exhibits a tensile strength of 17.5 MPa and an elongation at break of 10%, demonstrating excellent mechanical properties that meet the requirements of practical applications. Furthermore, this aromatic polyamide-imide hollow fiber membrane also possesses excellent thermal stability, such as... Figure 3 As shown, the aromatic polyamide hollow fiber membrane only begins to degrade at around 410°C as the temperature increases, enabling its application under high-temperature conditions.

[0066] Example 2

[0067] (1) Under nitrogen atmosphere and ice bath conditions, add 100 ml of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) to a three-necked round-bottom flask containing 32.023 g of TFDB. N,N-Dimethylacetamide (DMAc) was completely dissolved and then added in three batches with 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC). The first batch consisted of 17.3855 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA), the second batch consisted of 8.121 g of terephthaloyl chloride (TPC), and the third batch consisted of 9.2645 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA). Finally, the remaining 115 ml of N,N-dimethylacetamide (DMAc) was added. After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the fibrous solid polymer was filtered and then filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%. The molar ratio of 6FDA to TPC in the reaction system was 6:4.

[0068] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1850 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 550,000, and the degree of polymerization n was 10-110. The remaining experimental and application steps were the same as in Example 1.

[0069] Example 3

[0070] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC) were added in three batches. The first batch consisted of 19.8002 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 4.0604 g of terephthaloyl chloride (TPC), and the third batch consisted of 15.7398 g of terephthaloyl chloride (TPC). 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washes, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of 6FDA to TPC in the reaction system was 8:2.

[0071] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration was calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1850 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 650,000, and the degree of polymerization n was 10-135. The remaining experimental and application steps were the same as in Example 1.

[0072] Comparative Example 1

[0073] (1) Under a nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After dissolution, 44.424 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%.

[0074] (2) At room temperature, the above polymer is dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution is 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity is 1880 poise, the weight-average molecular weight of the polyamide solution is between 50,000 and 400,000, and the degree of polymerization n is 10-90. Hollow fiber membranes are produced using this polyamide-imide solution through the aforementioned asymmetric hollow fiber membrane production method. The specific production method is as follows: the prepared polyamide-imide solution is filtered through a metal wire mesh (380 mesh), extruded through a hollow fiber membrane spinning nozzle (spinning nozzle specifications: 1000 μm circular aperture, 200 μm circular slit width, 400 μm central hole diameter), and then the extruded hollow fiber body is passed through a nitrogen gas gap to form a dense skin layer. The height of the gas gap affects the thickness of the skin layer. The fibers were then placed in a coagulation bath containing an aqueous ethanol solution with a concentration of 75-85 wt% to impregnate them into wet fibers. The wet fibers were then impregnated in the ethanol solution at 45°C for 2 hours for solvent removal, followed by impregnation in isooctane at 65°C for 2.5 hours to displace the solvent. After this process, the fibers were dried at 120°C for 12 hours, and finally heat-treated at 250°C for 2 hours to obtain a hollow fiber membrane with an outer diameter of approximately 450 μm, an inner diameter of approximately 300 μm, and a membrane thickness of approximately 55 μm. The gas permeability and mechanical properties of this hollow fiber membrane were measured using the aforementioned method. The results are shown in Table 1.

[0075] Comparative Example 2

[0076] (1) Under a nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 20.302 g of terephthaloyl chloride (TPC) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%.

[0077] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1840 poise, the weight-average molecular weight of the polyamide solution was between 80,000 and 750,000, and the degree of polymerization n was 15-160. The remaining experimental and application steps were the same as those in Comparative Example 1.

[0078] Example 4

[0079] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N-methylpyrrolidone (NMP) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC) were added in three batches. The first batch consisted of 16.1815 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 10.151 g of terephthaloyl chloride (TPC), the third batch consisted of 6.0305 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), and the last batch consisted of 115 ml of N-methylpyrrolidone (NMP). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued for 24 hours at room temperature to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of 6FDA to TPC in the reaction system was 5:5.

[0080] (2) At room temperature, the above polymer was dissolved in N-methylpyrrolidone (NMP) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1850 poise, the weight-average molecular weight of the polyamide solution was between 60,000 and 550,000, and the degree of polymerization n was 10-110. The remaining experimental and application steps were the same as in Example 1.

[0081] Example 5

[0082] (1) Under nitrogen atmosphere and ice bath conditions, add 100 ml of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) to a three-necked round-bottom flask containing 32.023 g of TFDB. N-methylpyrrolidone (NMP) was completely dissolved and then added in three batches with 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC). The first batch consisted of 17.3855 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 8.121 g of terephthaloyl chloride (TPC), and the third batch consisted of 9.2645 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA). Finally, the remaining 115 ml of N-methylpyrrolidone (NMP) was added. After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the fibrous solid polymer was filtered and then filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%. The molar ratio of 6FDA to TPC in the reaction system was 6:4.

[0083] (2) At room temperature, the above polymer was dissolved in N-methylpyrrolidone (NMP) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration was calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1860 poise, the weight-average molecular weight of the polyamide solution was between 65,000 and 600,000, and the degree of polymerization n was 15-120. The remaining experimental and application steps were the same as in Example 1.

[0084] Example 6

[0085] (1) Under nitrogen atmosphere and ice bath conditions, add 100 ml of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) to a three-necked round-bottom flask containing 32.023 g of TFDB. N-methylpyrrolidone (NMP) was completely dissolved and then added in three batches with 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and terephthaloyl chloride (TPC). The first batch consisted of 19.8002 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 4.0604 g of terephthaloyl chloride (TPC), and the third batch consisted of 15.7398 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA). Finally, the remaining 115 ml of N-methylpyrrolidone (NMP) was added. After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the fibrous solid polymer was filtered and then filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%. The molar ratio of 6FDA to TPC in the reaction system was 8:2.

[0086] (2) At room temperature, the above polymer was dissolved in N-methylpyrrolidone (NMP) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1860 poise, the weight-average molecular weight of the polyamide solution was between 70,000 and 650,000, and the degree of polymerization n was 15-130. The remaining experimental and application steps were the same as in Example 1.

[0087] Example 7

[0088] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and isophthaloyl chloride (IPC) were added in three batches. The first batch consisted of 16.1815 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 10.151 g of isophthaloyl chloride (IPC), and the third batch consisted of 6.0305 g of DMAc. 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washes, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of 6FDA to IPC in the reaction system was 5:5.

[0089] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1850 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 500,000, and the degree of polymerization n was 10-100. The remaining experimental and application steps were the same as in Example 1.

[0090] Example 8

[0091] (1) Under nitrogen atmosphere and ice bath conditions, add 100 ml of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB) to a three-necked round-bottom flask containing 32.023 g of TFDB. N,N-Dimethylacetamide (DMAc) was completely dissolved and then added in three batches with 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) and isophthaloyl chloride (IPC). The first batch consisted of 17.3855 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA), the second batch consisted of 8.121 g of isophthaloyl chloride (IPC), and the third batch consisted of 9.2645 g of 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA). Finally, the remaining 115 ml of N,N-dimethylacetamide (DMAc) was added. After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the fibrous solid polymer was filtered and then filtered again. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 96%. The molar ratio of 6FDA to IPC in the reaction system was 6:4.

[0092] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration was calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1860 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 600,000, and the degree of polymerization n was 10-120. The remaining experimental and application steps were the same as in Example 1.

[0093] Example 9

[0094] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA) and isophthaloyl chloride (IPC) were added in three batches. The first batch consisted of 19.8002 g of 2,2'-bis(3,4-dicarboxylic acid) hexafluoropropane dianhydride (6FDA), the second batch consisted of 4.0604 g of terephthaloyl chloride (TPC), and the third batch consisted of 15.7398 g of terephthaloyl chloride (TPC). 2,2'-bis(3,4-dicarboxylic acid)hexafluoropropane dianhydride (6FDA) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washes, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of 6FDA to IPC in the reaction system was 8:2.

[0095] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1870 poise, the weight-average molecular weight of the polyamide solution was between 80,000 and 600,000, and the degree of polymerization n was 15-130. The remaining experimental and application steps were the same as in Example 1.

[0096] Example 10

[0097] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and terephthaloyl chloride (TPC) were added in three batches. The first batch consisted of 13.1305 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), the second batch consisted of 10.151 g of terephthaloyl chloride (TPC), and the third batch consisted of 2.9795 g of terephthaloyl chloride (TPC). 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) was added, followed by the remaining 115 ml of N,N-dimethylacetamide (DMAc). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washes, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of BTDA to TPC in the reaction system was 5:5.

[0098] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration is calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1850 poise, the weight-average molecular weight of the polyamide solution was between 75,000 and 650,000, and the degree of polymerization n was 15-130. The remaining experimental and application steps were the same as in Example 1.

[0099] Example 11

[0100] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and terephthaloyl chloride (TPC) were added in three batches. The first batch consisted of 13.72725 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), the second batch consisted of 8.121 g of terephthaloyl chloride (TPC), and the third batch consisted of 5.60625 g of terephthaloyl chloride (TPC). Finally, 115 ml of N,N-dimethylacetamide (DMAc) was added to 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued at room temperature for another 24 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washes, the polymer was filtered, and the resulting fibrous solid polymer was also filtered. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of BTDA to TPC in the reaction system was 6:4.

[0101] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The polymer concentration of the solution was 15 wt% (polymer concentration was calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1860 poise, the weight-average molecular weight of the polyamide solution was between 85,000 and 750,000, and the degree of polymerization n was 20-160. The remaining experimental and application steps were the same as in Example 1.

[0102] Example 12

[0103] (1) Under nitrogen atmosphere and ice bath conditions, 100 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 32.023 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA) and terephthaloyl chloride (TPC) were added in three batches. The first batch consisted of 14.91925 g of 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), the second batch consisted of 4.0604 g of terephthaloyl chloride (TPC), and the third batch consisted of 10.85885 g of terephthaloyl chloride (TPC). Finally, 115 ml of N,N-dimethylacetamide (DMAc) was added to 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA). After reacting for 12 hours, 47 ml of acetic anhydride and 12 ml of trimethylpyridine were added, and the reaction was continued for 24 hours at room temperature to obtain a viscous reaction solution. The viscous reaction solution was poured into 1000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the resulting fibrous solid polymer was filtered again. The obtained polymer was dried in a vacuum drying oven at 120°C for 12 hours and then weighed, with a yield of 96%. The molar ratio of BTDA to TPC in the reaction system was 8:2.

[0104] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide-imide solution. The degree of polymerization of this solution was 15 wt% (polymer concentration was calculated by dividing the mass of the polymer by the total mass of the polymer and solvent), the rotational viscosity was 1880 poise, the weight-average molecular weight of the polyamide solution was between 10,000 and 800,000, and the degree of polymerization n was between 20 and 200. The remaining experimental and application steps were the same as in Example 1.

[0105] Table 1 lists the measured results of water vapor permeation rate, water vapor to nitrogen permeation rate ratio, mechanical strength of the hollow fiber membranes, helium permeation rate of the porous layer, and hot water resistance of the hollow fiber membranes in the examples and comparative examples. For example: the water vapor permeation rate (P^) of the hollow fiber membranes in Examples 1-3 H2O ) is 3.0x10 -3 cm 3 (STP) / cm 2 ·(STP) / cm 2 • cmHg or greater, water vapor and nitrogen permeation rate ratio (P^ H2O / P^ N2 The value is 300 or greater, where the helium permeation rate (P^) of the porous layer (support layer) of this membrane is 300 or greater. He Both are 2.7xl0 -3 cm 3 (STP) / cm 2•sec·cmHg or greater, all of which are improved compared to Comparative Example 1 polyimide. Examples 1-3 form polyamide-imide through terpolymerization of 6FDA, TFDB and TPC. The addition of TPC introduces amide bonds into the polymer structure. Amide bonds have good hydrophilicity and can adsorb water vapor and quickly permeate through the membrane, thereby improving the water vapor permeation rate of the membrane. At the same time, compared with the imide ring structure, the presence of amide bonds improves the hydrolytic stability of the membrane.

[0106] The polyamide-imide (PAI) hollow fiber gas separation membrane of this invention exhibits excellent water vapor permeability and water vapor / nitrogen selectivity, along with superior mechanical strength and hot water resistance. When used in conjunction with a high-efficiency hollow fiber membrane module, this hollow fiber gas separation membrane achieves excellent dehumidification performance. Furthermore, the aromatic polyamide hollow fiber gas separation membrane of this invention utilizes widely available and low-cost monomers, making it suitable for large-scale industrial production applications.

[0107] Table 1

[0108]

[0109] Note: Units for P₂H₂O and P₂He: l⁻¹ -3 cm 3 (STP) / cm 2 •sec·cmHg; Tensile strength unit: MPa; Elongation at break unit: %; Hot water resistance is the retention rate of elongation at break after treatment with hot water at 80℃ for 120h, unit: %.

[0110] The parts of this invention not described in detail are well-known to those skilled in the art. The embodiments described above are merely preferred embodiments of the invention, and do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Various modifications and improvements to the technical solutions of this invention made by those skilled in the art without departing from the spirit of the invention should fall within the protection scope defined by the claims of this invention.

Claims

1. An aromatic polyamide-imide hollow fiber gas separation membrane, characterized in that, The hollow fiber gas separation membrane is made of aromatic polyamide-imide, and the general structural formula of the aromatic polyamide-imide is as follows: R1 is the aromatic unit structure of an aromatic diamine, R2 is the aromatic unit structure of an aromatic dianhydride, and R3 is the aromatic unit structure of an aromatic diacyl chloride; among which... X , Y These represent the molar percentages of the R2 and R3 portions in the polymer, respectively. X + Y = 100， 1≤X≤99 1 ≤Y≤99 n represents the degree of polymerization, which is a positive integer from 10 to 200, and the weight-average molecular weight of the aromatic polyamide-imide is between 5,000 and 800,000. R1 is selected from one or more of the following structures: ； R2 represents one or more of the following structures: ； R3 is selected from one or more of the following structures: 。 2. The method for preparing the aromatic polyamide-imide hollow fiber gas separation membrane according to claim 1, characterized in that, Includes the following steps: (1) Under nitrogen atmosphere and ice bath conditions, add polar solvent to the reaction vessel containing aromatic diamine monomer. After complete dissolution, add aromatic dianhydride monomer in three batches, then add aromatic diacyl chloride monomer. After cold bath reaction, add acetic anhydride and trimethylpyridine to catalyze the reaction, and then react at room temperature to obtain reaction solution. (2) The reaction solution was precipitated in methanol solution to obtain fibrous polymer. After washing with methanol, the obtained polymer was vacuum dried to remove excess solvent and obtain dried fibrous polymer. (3) Dissolve the dried fibrous polymer in a polar solvent to obtain a polyamide-imide solution; (4) The prepared polyamide-imide solution is filtered and extruded through a hollow fiber membrane spinning nozzle. The extruded hollow fiber body is then passed through a nitrogen gas gap to form a skin layer. After that, it is placed in a coagulation bath containing an aqueous ethanol solution to impregnate it into wet fiber. The wet fiber is impregnated in an ethanol solution for solvent removal treatment, and then impregnated in isooctane, dried, and finally heat-treated to obtain a hollow fiber membrane.

3. The preparation method according to claim 2, characterized in that, In step (1), the cold bath reaction time is 24 hours and the reheating time is 2 hours; in step (1), the polar solvent is one or more of NMP, DMF, DMAc and DMSO.

4. The preparation method according to claim 2, characterized in that, In step (2), the vacuum drying temperature is 120℃ and the vacuum drying time is 12 hours.

5. The preparation method according to claim 2, characterized in that, In step (3), the concentration of the polyamide-imide solution is 15 wt%.

6. The preparation method according to claim 2, characterized in that, In step (4), the ethanol concentration in the aqueous ethanol solution is 75-85 wt%.

7. The application of the aromatic polyamide-imide hollow fiber gas separation membrane as described in claim 1, characterized in that, The separation membrane is used for dehumidification.

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