Aromatic polyamide hollow fiber gas separation membrane, method of making and use

Abstract

The application discloses an aromatic polyamide hollow fiber gas separation membrane, a preparation method and application. The separation membrane is made of a polymer which is copolymerized by two kinds of aromatic diacyl chloride and aromatic diamine monomers. The polymer has high water vapor transmission rate and selectivity, and also has good mechanical strength and hydrolysis stability. Meanwhile, the hollow fiber gas separation membrane is a kind of asymmetric structure which includes 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 (PA) 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] Air dehumidification technology has wide applications in modern industrial production, medical and health care, and daily life. For example, in industrial production, pneumatic valves, power sources for automated instruments, and protective gases in chemical and pharmaceutical product packaging lines should all be dry air to prevent water vapor from condensing at low temperatures and causing production accidents. In daily life, places such as libraries and museums also need to control the humidity of the air within a certain range. Excessive humidity in the cabins of naval ships can cause discomfort and induce diseases, and it also affects the preservation of materials and the operation of instruments. High humidity environments can lead to a decrease in the accuracy of precision electronic devices, seriously affect the use of ammunition, and even cause major accidents. Traditional dehumidification methods include cooling dehumidification, solid adsorbent dehumidification, and rotary wheel dehumidification, but traditional methods have disadvantages such as low dehumidification efficiency, complex equipment, and secondary pollution (Commun Chem 5,65(2022)). Compared with traditional dehumidification technologies, membrane-based gas dehumidification technology has received increasing attention in recent years due to its significant technical and economic advantages, such as simple installation, convenient operation, low energy consumption and process costs, environmental friendliness, and large capacity of waterless products (Fuel, 285, 2021, 119161, 0016-2361).

[0003] Gas separation membranes are commonly used in various gas separation methods. Gas separation membrane materials can be classified into polymer materials, inorganic materials, and organic-inorganic hybrid materials. Among them, polymer materials are often used to make gas separation membranes due to their advantages such as good chemical stability, thermal stability, strong processability, and low manufacturing cost. However, polymer membranes are often subject to the mutual constraints of permeability and selectivity, and both cannot be achieved simultaneously. In order to prepare gas separation membranes with both high selectivity and high permeability, polymer membranes are often made into hollow fiber gas separation membranes. These gas separation membranes are asymmetrical structures composed of a porous layer (support layer) and a skin layer (selective layer). By reducing the thickness of the permeating gas through the skin layer, the permeation resistance is reduced, thereby increasing the gas permeability (Polymers 2021, 13(13), 2211). Furthermore, compared to other membrane structures (plate and frame, spiral winding, etc.), hollow fiber structures offer the highest surface area to volume ratio, and productivity can be maximized due to the thin separation layer (Fibers and Polymers 2020, Vol.21, No.5, 944-953).

[0004] Gas separation membranes are commonly used in hollow fiber gas separation membrane modules. These modules are constructed by bundling a large number of hollow fiber membranes into a hollow fiber bundle and fixing at least one end of the bundle with a thermosetting resin (such as epoxy resin) or thermoplastic resin, leaving the hollow fiber membrane open at that end. One or more of these hollow fiber membrane elements are then inserted into a container having at least one mixed gas inlet, one permeable gas outlet, and one impermeable gas outlet, separating the internal transfer space of the hollow fiber membrane from its external transfer space. In the hollow fiber gas separation membrane module, a mixed gas is introduced into the space that contacts the internal or external space of the hollow fiber membrane. When the gas flows into contact with the hollow fiber membrane, the permeable gases in the mixed gas selectively permeate through the membrane and are recovered through the permeable gas outlet, while the gases that are excluded from permeability are recovered through the impermeable gas outlet, thus achieving gas separation.

[0005] Polyamides possess excellent comprehensive properties, including mechanical properties, heat resistance, wear resistance, high chemical stability, and self-lubricating properties. They also have a low coefficient of friction, some flame retardancy, and are easy to process. They are suitable for reinforcement and modification with glass fiber and other fillers to improve performance and expand application range. Polyamides are diverse and widely used in manufacturing industries such as machinery, chemical equipment, aerospace equipment, and metallurgical equipment. Among them, aromatic polyamides (PA) are high-performance materials with high thermal and mechanical stability and excellent film-forming ability. Because the aromatic polyamide molecule contains a benzene ring in its main chain, membranes prepared from it have excellent pressure resistance and thermal stability. At the same time, this material has outstanding properties such as good chemical stability and resistance to organic solvents. These fundamental properties provide great potential for its application in the membrane field (Membrane Science and Technology 36.05(2016):124-131).

[0006] For gas separation membranes prepared by copolymerizing polyamides from different monomers, CN105381725B discloses a polyethylene glycol-functionalized montmorillonite / polyether copolyamide mixed matrix membrane for gas separation, noting that the polyethylene glycol-functionalized montmorillonite / polyether copolyamide mixed matrix membrane not only possesses excellent mechanical properties but also exhibits high permeation flux and separation factor. CN110548419A discloses a polyamide VOCs-retaining polymer separation membrane for nitrogen / VOCs separation applications. WO2019131786(A1) discloses a gas separation membrane comprising a porous support membrane containing aromatic polyamide and a separation functional layer for forming a gas separation element, noting that this gas separation element can separate mixed gases at low cost and has good heat resistance. However, none of these disclosures pertain to gas separation membranes used for air dehumidification, and none mention water vapor permeation rate and selectivity. Furthermore, none of these disclosed gas separation membranes are fabricated as asymmetric hollow fiber gas separation membranes.

[0007] Water resistance and hot water resistance are crucial performance characteristics of dehumidification membranes. However, gas separation membranes that selectively permeate water-containing gases often exhibit poor water and hot water resistance. For example, polyimide gas separation membranes, due to their easily hydrolyzed imide ring structure, are prone to hydrolysis and breakage in humid environments, failing to meet the requirements for long-term stable use. CN102872725A discloses a ZrO2 membrane for CO2 capture with high hydrothermal stability and points out that this ZrO2 membrane has good water stability. However, this gas separation membrane is an inorganic membrane, and inorganic membranes generally have high manufacturing costs and complex manufacturing processes. Therefore, finding a low-cost polymer material with excellent hydrolytic stability to meet the requirements for long-term stable use of gas separation dehumidification membranes is of great importance.

[0008] To meet the practical requirements of industrial and domestic applications, a hollow fiber gas separation membrane for dehumidification is synthesized, possessing properties such as high permeability, high selectivity, good water resistance, and excellent mechanical properties. This invention prepares an asymmetric membrane by copolymerizing at least two or more different aromatic monomers to form aromatic polyamide (PA), thus producing a gas separation membrane with high permeability and high selectivity. Simultaneously, this gas separation membrane exhibits practical-grade mechanical strength and excellent water and hot water resistance. Summary of the Invention

[0009] The purpose of this invention is to use two aromatic diacyl chlorides with different structures to copolymerize with different aromatic diamine monomers via amide condensation reaction, thereby obtaining aromatic polyamides with high permeability and high selectivity. These polyamides are then applied to hollow fiber gas separation membranes to improve the polymer's air dehumidification performance.

[0010] The present invention provides an aromatic polyamide hollow fiber gas separation membrane, a preparation method thereof, and an application thereof. 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 of this asymmetric structure facilitates the rapid passage of gas, while the dense skin layer increases the selective permeability of the gas. The aromatic polyamide in the present invention has an amide bond in the main chain, and the amide bond can form a hydrogen bond with a strong interaction force with water molecules, so that water vapor can be rapidly adsorbed and permeated through the membrane. At the same time, the amide bond is a very stable structure and is difficult to hydrolyze under normal circumstances. The main chain of the aromatic polyamide contains a large number of aromatic rings, and the close packing of the aromatic rings can significantly reduce the permeability of other gases in the air, thereby achieving efficient separation of water vapor and air. At the same time, the rigid benzene ring main chain also endows the aromatic polyamide with excellent thermal stability, chemical stability and mechanical strength.

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

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

[0013]

[0014] Ar1 is an aromatic unit structure forming an aromatic diamine, and Ar2 and Ar3 are aromatic unit structures forming an aromatic diacid dichloride respectively. Among them, X and Y are the molar percentages of the Ar2 and Ar3 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 of 10 - 200. The weight average molecular weight of the aromatic polyamide is between 5000 and 800000.

[0015] Further, X and Y are the molar percentages of the Ar2 and Ar3 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] Ar1 represents one or more of the following structures:

[0019]

[0020] The Ar1 structure is characterized by having a diamine monomer with an aromatic structure. This aromatic ring structure can enhance the mechanical strength of the polymer. At the same time, the hydrophilicity and hydrophobicity of the polymer can be further regulated by changing the structure of the functional groups on the aromatic ring.

[0021] Ar2 and Ar3 are each independently selected from one or more of the following structures:

[0022]

[0023] The method for preparing the hollow fiber gas separation membrane as described above includes the following steps:

[0024] (1) Under nitrogen atmosphere and ice bath conditions, N,N-dimethylacetamide (DMAc) was added to the aromatic diamine monomer. After complete dissolution, two aromatic dichlorides with different Ar2 and Ar3 structures were added in three batches. After complete dissolution, propylene oxide was added and the reaction was carried out to obtain the reaction solution.

[0025] (2) The reaction solution was precipitated in methanol solution to obtain fibrous polymer. After washing, the obtained polymer was vacuum dried to remove excess solvent and obtain dried fibrous polymer.

[0026] (3) Dissolve the dried fibrous polymer in N,N-dimethylacetamide (DMAc) solvent to obtain a polyamide solution;

[0027] (4) The polyamide solution is filtered and then extruded through a hollow fiber membrane spinning nozzle, and the extruded hollow fiber body is passed through a nitrogen atmosphere. Then it is impregnated in a condensation bath containing an aqueous ethanol solution to form wet fibers. The wet fibers are impregnated in ethanol, then impregnated in isooctane, dried, and then heat-treated at 200-300°C to obtain the hollow fiber gas separation membrane.

[0028] Further, in step (1), the aromatic diamine monomer and the two aromatic dichlorides with different Ar2 and Ar3 structures are used in the same molar amount, and the molar amount of propylene oxide is 10 times that of the aromatic diamine monomer.

[0029] Furthermore, in step (1), the reaction time is 12 hours.

[0030] Furthermore, in step (2), the vacuum drying temperature is 120°C and the vacuum drying time is 12 hours.

[0031] Furthermore, in step (3), the concentration of the polyamide solution is 5 wt%.

[0032] Furthermore, in step (4), all the hollow fiber membranes obtained have an outer diameter of about 450 μm, an inner diameter of about 300 μm, and a membrane thickness of about 55 μm.

[0033] The application of the aromatic polyamide hollow fiber gas separation membrane as described above or the hollow fiber separation membrane prepared by the method described above, wherein the separation membrane is used for dehumidification; preferably, the separation membrane is used for gas dehumidification; more preferably, the separation membrane is used for air dehumidification.

[0034] 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.

[0035] Preparation of a polyamide solution with a polymer concentration of 5 wt%.

[0036] (1) Under nitrogen atmosphere and ice bath conditions, N,N-dimethylacetamide (DMAc) solvent was added to a three-necked round-bottom flask containing aromatic diamine monomers. After complete dissolution, two aromatic binary chlorides with different Ar2 and Ar3 structures were added in three batches. After complete dissolution, propylene oxide was added and the reaction was carried out for 12 hours to obtain a viscous reaction solution.

[0037] (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.

[0038] (3) The dried fibrous polymer was dissolved in N,N-dimethylacetamide (DMAc) solvent to obtain a 5 wt% polyamide solution. The concentrations of the aromatic diamine monomer and the two aromatic dichlorides with different Ar2 and Ar3 structures in the N,N-dimethylacetamide (DMAc) solvent were 5 wt%. The molar amounts of the aromatic diamine monomer and the two aromatic dichlorides with different Ar2 and Ar3 structures were the same, and the molar amount of propylene oxide was 10 times that of the monomer.

[0039] Production of asymmetric hollow fiber membranes

[0040] The prepared polyamide solution was filtered through a 380-mesh metal mesh and extruded through a hollow fiber membrane spinning nozzle (1000 μm circular pore size, 200 μm circular pore width, 400 μm central pore diameter). The extruded hollow fiber body was then passed through a nitrogen gas gap to form a dense skin. 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.

[0041] The beneficial results of this invention are:

[0042] (1) Synthesizing aromatic polyamide polymers via polycondensation reaction;

[0043] (2) The obtained aromatic polyamide polymer is well soluble in polar solvents, and the gas separation membrane exhibits good water stability and mechanical properties. After being treated with hot water at 100°C for 360 hours, the elongation at break of the hollow fiber membrane remains at 95% or greater than before the hot water treatment. The tensile strength of the hollow fiber membrane is 17.9 MPa or greater, and the elongation at break is 11% or greater.

[0044] (3) The water vapor permeation rate (P^H2O) of the hollow fiber membrane is 5.85 x 10⁻⁶. -3 cm 3 (STP) / cm 2 ·(STP) / cm 2 The permeability is approximately cmHg, and the water vapor to nitrogen permeation rate ratio (P^H2O / P^N2) is approximately 500. The helium permeation rate (P^He) of the porous layer (support layer) of this membrane is 5.5 x 10⁻⁶. -3 cm 3 (STP) / cm 2 With a moisture permeability of approximately 0.25 sec·cmHg, it exhibits excellent water vapor permeability and selectivity, meeting the practical requirements for dehumidification applications. Attached Figure Description

[0045] Figure 1 The gas permeation rate diagram is shown for the polyamide hollow fiber gas separation membrane prepared in Example 1.

[0046] Figure 2The tensile strength and elongation at break of the polyamide hollow fiber gas separation membrane prepared in Example 2 are shown in the figure.

[0047] Figure 3 Thermogravimetric analysis curve of the polyamide hollow fiber gas separation membrane prepared in Example 1. Detailed Implementation

[0048] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. The following embodiments are further illustrations of the present 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.

[0049] The performance testing method for the hollow fiber membrane in the following embodiments of the present invention is as follows:

[0050] Determination of water vapor permeation performance of hollow fiber membranes

[0051] 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.

[0052] Determination of nitrogen permeation performance of hollow fiber membranes

[0053] 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. Nitrogen gas was introduced at a fixed pressure, and the permeation rate was measured. The permeation rate of each gas was calculated by measuring the volume of permeated nitrogen gas, the input pressure, and the effective membrane area. This measurement was performed at 50°C.

[0054] Determination of helium permeation performance of porous layers in hollow fiber membranes

[0055] Multiple hollow fiber membranes were plasma-treated using a plasma treatment device. A portion of the membranes was removed every five minutes to obtain hollow fiber membranes treated for different durations. Then, a pencil-shaped assembly with an effective length of 10 mm was fabricated using the aforementioned method to measure the gas permeation of the hollow fiber membranes. Pure nitrogen or pure helium was introduced into the pencil-shaped assembly at a fixed volume and pressure to measure the volume of fluid permeated. The permeation rates of nitrogen and helium were calculated using the measured permeate volume, input pressure, and effective membrane area. Since the ratio of the gas permeation rates of helium and nitrogen after 30 minutes of plasma treatment of the hollow fiber membrane (P0) is significantly higher than that after 30 minutes of plasma treatment... He / P^ N2 The helium permeation rate (P0) is not greater than 1.2, therefore, after treating the hollow fiber membrane for 20 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.

[0056] Determination of tensile strength and elongation at break of hollow fiber membranes

[0057] 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.

[0058] Measurement of rotational viscosity

[0059] The rotational viscosity of the polyamide solution was measured at 100°C using a rotational viscometer (rotor shear rate: 1.75 / s).

[0060] Determination of water resistance and hot water resistance of hollow fiber membranes

[0061] 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 100°C for 360 hours as a hot water treatment. After the hot water treatment, the 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 (%).

[0062] Example 1

[0063] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.064 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 16.2416 g of isophthaloyl chloride (IPC) in the second batch, and 4.0604 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 989 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 91%. The molar ratio of TPC to IPC in the reaction system was 6:4.

[0064] (2) At room temperature, the above polymer is dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of this solution is 5 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 500,000, and the degree of polymerization n is 10-100. Hollow fiber membranes are produced using this polyamide solution. The specific production method is as follows: the prepared polyamide solution is filtered through a 380-mesh metal wire mesh, extruded through a hollow fiber membrane spinning nozzle (1000 μm circular pore diameter, 200 μm circular pore width, 400 μm central pore diameter), and then the extruded hollow fiber body is passed through a nitrogen gas gap to form a dense skin layer. Afterwards, it is placed in a coagulation bath containing an aqueous ethanol solution with a concentration of 75-85 wt% to impregnate it into wet fibers. The wet fibers were immersed in an ethanol solution at 45°C for 2 hours to remove the solvent, followed by immersion in isooctane at 65°C for 2.5 hours to displace the solvent. Afterward, 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 aromatic polyamide backbone contains a rigid, all-aromatic ring structure, with tightly packed molecular chains exhibiting good compressibility, effectively isolating gases with large gas dynamic diameters. Therefore, Figure 1As the kinetic diameter of various gases increases, the permeability of this membrane decreases sequentially. In particular, its permeability to N2 and CH4, which have larger kinetic diameters, is far lower than its permeability to water vapor, enabling highly efficient air dehumidification and natural gas dehumidification applications. Simultaneously, this aromatic polyamide hollow fiber membrane also exhibits excellent thermal stability, such as... Figure 3 As shown, the aromatic polyamide hollow fiber membrane only begins to degrade at around 400°C as the temperature increases, enabling its application under high-temperature conditions.

[0065] Example 2

[0066] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.064 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 12.1812 g of isophthaloyl chloride (IPC) in the second batch, and 8.1208 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 989 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 86%. The molar ratio of TPC to IPC in the reaction system was 7:3.

[0067] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of this solution was 5 wt% (polymer concentration calculation method: the mass of the polymer divided by the total mass of the polymer and solvent), the rotational viscosity was 1873 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. The mechanical properties of the aromatic polyamide hollow fiber membrane with TPC:IPC = 7:3 were tested, and the test results are as follows: Figure 2 As shown, the aromatic polyamide hollow fiber membrane has a tensile strength of 17.9 MPa and an elongation at break of 11%, exhibiting good mechanical properties that meet the requirements of practical applications.

[0068] Example 3

[0069] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.064 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 8.1208 g of isophthaloyl chloride (IPC) in the second batch, and 12.1812 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 989 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 84%. The molar ratio of TPC to IPC in the reaction system was 8:2.

[0070] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 1892 poise, the weight-average molecular weight of the polyamide solution was between 100,000 and 700,000, and the degree of polymerization n was 20-180. The remaining experimental and application steps were the same as in Example 1.

[0071] Comparative Example 1

[0072] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.064 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 40.604 g of terephthaloyl chloride (TPC) was added, followed by the remaining 989 ml of N,N-dimethylacetamide (DMAc). After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 89%.

[0073] (2) At room temperature, the above polymer is dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of this solution is 5 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 1902 poise, the weight-average molecular weight of the polyamide solution is between 150,000 and 800,000, and the degree of polymerization n is 30-200. Hollow fiber membranes are produced using this polyamide solution. The specific production method is as follows: the prepared polyamide solution is filtered through a 380-mesh metal wire mesh, extruded through a hollow fiber membrane spinning nozzle (1000 μm circular pore diameter, 200 μm circular pore width, 400 μm central pore diameter), and then the extruded hollow fiber body is passed through a nitrogen gas gap to form a dense skin layer. Afterwards, it is placed in a coagulation bath containing an aqueous ethanol solution with a concentration of 75-85 wt% to impregnate it into wet fibers. The wet fibers were immersed in an ethanol solution at 45°C for 2 hours to remove the solvent, followed by immersion in isooctane at 65°C for 2.5 hours to displace the solvent. Afterward, 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.

[0074] Comparative Example 2

[0075] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.064 g of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFDB). After complete dissolution, 40.604 g of isophthaloyl chloride (IPC) was added, followed by the remaining 989 ml of N,N-dimethylacetamide (DMAc). After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 90%.

[0076] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 1910 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 400,000, and the degree of polymerization n was 10-100. The remaining experimental and application steps were the same as those in Comparative Example 1.

[0077] Example 4

[0078] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 30.43 g of 3,5-diaminobenzoic acid (DABA). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 16.2416 g of isophthaloyl chloride (IPC) in the second batch, and 4.0604 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 420 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 3000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the polymer was filtered and the resulting fibrous solid polymer was filtered. The polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 89%. The molar ratio of TPC to IPC in the reaction system was 6:4.

[0079] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 1846 poise, the weight-average molecular weight of the polyamide solution was between 80,000 and 450,000, and the degree of polymerization n was 80-150. The remaining experimental and application steps were the same as in Example 1.

[0080] Example 5

[0081] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 30.43 g of 3,5-diaminobenzoic acid (DABA). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 12.1812 g of isophthaloyl chloride (IPC) in the second batch, and 8.1208 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 420 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 3000 ml of methanol to obtain a fibrous polymer. After three precipitation and washing, the polymer was filtered and the resulting fibrous solid polymer was filtered. The polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 86%. The molar ratio of TPC to IPC in the reaction system was 7:3.

[0082] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 100,000 and 600,000, and the degree of polymerization n was 20-155. The remaining experimental and application steps were the same as in Example 1.

[0083] Example 6

[0084] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 30.43 g of 3,5-diaminobenzoic acid (DABA). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 8.1208 g of isophthaloyl chloride (IPC) in the second batch, and 12.1812 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 420 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 3000 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 87%. The molar ratio of TPC to IPC in the reaction system was 8:2.

[0085] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 100,000 and 550,000, and the degree of polymerization n was 20-150. The remaining experimental and application steps were the same as in Example 1.

[0086] Comparative Example 3

[0087] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 30.43 g of 3,5-diaminobenzoic acid (DABA). After complete dissolution, 40.604 g of terephthaloyl chloride (TPC) was added, followed by the remaining 420 ml of N,N-dimethylacetamide (DMAc). After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 3000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 91%.

[0088] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 100,000 and 800,000, and the degree of polymerization n was 20-200. The remaining experimental and application steps were the same as those in Comparative Example 1.

[0089] Comparative Example 4

[0090] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 30.43 g of 3,5-diaminobenzoic acid (DABA). After complete dissolution, 40.604 g of isophthaloyl chloride (IPC) was added, followed by the remaining 420 ml of N,N-dimethylacetamide (DMAc). After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 3000 ml of methanol to obtain a fibrous polymer. After three precipitation washings, the polymer was filtered, and the obtained fibrous solid polymer was filtered. The obtained polymer was dried in a vacuum drying oven at 120 °C for 12 h and then weighed. The yield was 90%.

[0091] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The polymer concentration of the solution was 5 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 1890 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 500,000, and the degree of polymerization n was 10-120. The remaining experimental and application steps were the same as those in Comparative Example 1.

[0092] Example 7

[0093] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.4034 g of 2,2',5,5'-tetrachlorobenzidine (TCB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 16.2416 g of isophthaloyl chloride (IPC) in the second batch, and 4.0604 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 1100 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 89%. The molar ratio of TPC to IPC in the reaction system was 6:4.

[0094] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The degree of polymerization of this solution was 5 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 1862 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 400,000, and the degree of polymerization n was 10-115. The remaining experimental and application steps were the same as in Example 1.

[0095] Example 8

[0096] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.4034 g of 2,2',5,5'-tetrachlorobenzidine (TCB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 12.1812 g of isophthaloyl chloride (IPC) in the second batch, and 8.1208 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 1100 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 86%. The molar ratio of TPC to IPC in the reaction system was 7:3.

[0097] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The degree of polymerization of this solution was 5 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 1871 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 450,000, and the degree of polymerization n was 10-130. The remaining experimental and application steps were the same as in Example 1.

[0098] Example 9

[0099] (1) Under nitrogen atmosphere and ice bath conditions, 1000 ml of N,N-dimethylacetamide (DMAc) was added to a three-necked round-bottom flask containing 64.4034 g of 2,2',5,5'-tetrachlorobenzidine (TCB). After complete dissolution, terephthaloyl chloride (TPC) and isophthaloyl chloride (IPC) were added in three batches: 20.302 g of terephthaloyl chloride (TPC) in the first batch, 8.1208 g of isophthaloyl chloride (IPC) in the second batch, and 12.1812 g of terephthaloyl chloride (TPC) in the third batch. Then, the remaining 1100 ml of N,N-dimethylacetamide (DMAc) was added. After complete dissolution, 140 ml of propylene oxide was added, and the reaction was carried out for 12 hours to obtain a viscous reaction solution. The viscous reaction solution was poured into 5000 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 87%. The molar ratio of TPC to IPC in the reaction system was 8:2.

[0100] (2) At room temperature, the above polymer was dissolved in N,N-dimethylacetamide (DMAc) to prepare a polyamide solution. The degree of polymerization of this solution was 5 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 1882 poise, the weight-average molecular weight of the polyamide solution was between 50,000 and 500,000, and the degree of polymerization n was 10-145. The remaining experimental and application steps were the same as in Example 1.

[0101] Table 1 lists the measured results of water vapor permeation rate, water vapor to nitrogen permeation rate ratio, mechanical strength of the hollow fiber membrane, 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^H2O) of the hollow fiber membrane in Example 1 is 5.85 x 10⁻⁶. -3 cm 3 (STP) / cm 2 ·(STP) / cm 2The permeability is ·cmHg, the water vapor to nitrogen permeability ratio (P^H2O / P^N2) is 500, and the helium permeability (P^He) of the porous layer (support layer) is 5.5 x 10⁻⁶. -3 cm 3 (STP) / cm 2 It exhibits good mechanical properties and excellent hot water resistance. Compared to Comparative Example 1, the water vapor transmission rate of Example 1 is higher. While Comparative Example 1 only uses a binary copolymer of TPC and TFDB, which improves mechanical properties, it significantly reduces the water vapor transmission rate. This is because the polymer molecular chain packing density of the TPC-TFDB binary copolymer is high, leading to a decrease in water vapor transmission rate. Example 1, however, is a ternary copolymer of TPC, IPC, and TFDB. By increasing the amount of IPC, the polymer molecular chain packing density is further reduced, increasing the free volume of the polymer and thus improving the water vapor transmission rate.

[0102] The hollow fiber gas separation membrane of this invention exhibits good water vapor permeability and water vapor / nitrogen selectivity, as well as excellent mechanical strength and hot water resistance. When used in conjunction with hollow fiber membrane modules, this hollow fiber gas separation membrane can achieve highly efficient dehumidification. Furthermore, the aromatic polyamide hollow fiber gas separation membrane of this invention has low monomer costs, making it suitable for large-scale production applications.

[0103] Table 1

[0104]

[0105] 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 100℃ for 360h, unit: %.

[0106] 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. The application of an aromatic polyamide hollow fiber gas separation membrane in air dehumidification, characterized in that, The separation membrane is made of aromatic polyamide, and the general structural formula of the aromatic polyamide is as follows: Ar1 is the aromatic unit structure that forms aromatic diamines. 2、 Ar3 represents the aromatic unit structure that forms aromatic diacyl chlorides; in, X , Y These are Ar in the polymer 2、 The percentage of moles in the Ar3 component. X + Y =100, 1≤ X<100 ,1≤ Y <100; n represents the degree of polymerization, n is a positive integer from 10 to 200, and the weight-average molecular weight of the aromatic polyamide is between 5,000 and 800,000; Ar1 is selected from one or more of the following structures: ； ； ； Ar2 and Ar3 are each independently selected from one or more of the following structures: 。 2. The application according to claim 1, characterized in that, The hollow fiber gas separation membrane is prepared by the following method: (1) Under nitrogen atmosphere and ice bath conditions, N,N-dimethylacetamide (DMAc) was added to the aromatic diamine monomer. After complete dissolution, two aromatic diacyl chlorides with different Ar2 and Ar3 structures were added in three batches. After complete dissolution, propylene oxide was added and the reaction was carried out to obtain the reaction solution. (2) The reaction solution was precipitated in methanol solution to obtain fibrous polymer. After washing, the obtained polymer was vacuum dried to remove excess solvent and obtain dried fibrous polymer. (3) Dissolve the dried fibrous polymer in N,N-dimethylacetamide (DMAc) solvent to obtain a polyamide solution; (4) The polyamide solution is filtered and then extruded through a hollow fiber membrane spinning nozzle, and the extruded hollow fiber body is passed through a nitrogen atmosphere and then impregnated in a condensation bath containing an aqueous ethanol solution to form wet fibers. The wet fibers are impregnated in ethanol, then in isooctane, dried, and then heat-treated at 200-300°C to obtain the hollow fiber gas separation membrane.

3. The application according to claim 2, characterized in that, In step (1), the aromatic diamine monomer and the two aromatic diacyl chlorides with different Ar2 and Ar3 structures are used in the same molar amount, and the molar amount of propylene oxide is 10 times that of the aromatic diamine monomer.

4. The application according to claim 2, characterized in that, In step (1), the reaction time is 12 hours.

5. The application according to claim 2, characterized in that, In step (2), the vacuum drying temperature is 120°C and the vacuum drying time is 12 hours.

6. The application according to claim 2, characterized in that, In step (3), the concentration of the polyamide solution is 5 wt%.

7. The application according to claim 2, characterized in that, In step (4), the hollow fiber gas separation membrane has an outer diameter of 400-500 μm, an inner diameter of 300-400 μm, and a membrane thickness of 50-100 μm.

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