A polysulfone-based moisture-permeable hollow fiber membrane and a method for producing the same

Abstract

The present application relates to the technical field of moisture-permeable membrane materials, and provides a polysulfone moisture-permeable hollow fiber membrane, the average pore size of a first surface is not greater than 100 nm, and the average pore size of a second surface is not less than 0.25 μm; the content of sulfonic acid groups on the first surface is greater than the content of sulfonic acid groups on the second surface, and the difference between the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface is not less than 1X10 ‑3 -4; the water conversion efficiency of the hollow fiber membrane is 40% to 70%, and the water vapor permeation rate of the hollow fiber membrane is 0.5 to 3 g / min. The structure of the polysulfone moisture-permeable hollow fiber membrane provided by the present application shows high water conversion efficiency and water vapor permeation rate, and also has good tensile strength, so that it has a long service life.

Description

Technical Field

[0001] This invention relates to the field of moisture-permeable membrane materials technology, and in particular to a polysulfone-based moisture-permeable hollow fiber membrane and its preparation method. Background Technology

[0002] Polysulfone polymers are excellent membrane materials. Hollow fiber membranes made from polysulfone polymers exhibit high pressure resistance, heat resistance, and oxidation resistance, as well as better biocompatibility than other membrane materials, and also possess a certain degree of hydrophilicity. Among them, polysulfone polymer microporous membranes are widely used in industrial, pharmaceutical, and medical fields.

[0003] Hollow fiber membranes are fibrous in shape and are self-supporting asymmetric membranes, with the dense layer located on the outer or inner surface of the fibers. Hollow fiber membranes are an important type of separation membrane, including hollow fiber ultrafiltration membranes, hollow fiber microfiltration membranes, hollow fiber reverse osmosis membranes, and hollow fiber gas separation membranes. They are mainly used in water purification, pharmaceutical purification, and humidification.

[0004] Hollow fiber gas separation membranes include moisture-permeable hollow fiber membranes, which are mainly used in humidifiers. They generally have good hydrophilicity and selective permeability, separating water vapor in the air from other gas components. Water vapor is transferred from the side with high humidity to the side with low humidity through the membrane.

[0005] Currently, there are many structural types of breathable hollow fiber membranes on the market. For example, Kuraray Co., Ltd.'s patent JP7122202B2, published on August 19, 2022, provides a water vapor separation membrane and a method for manufacturing the water vapor separation membrane. The membrane prepared is a porous hollow fiber water vapor separation membrane containing a hydrophilic resin (vinylpyrrolidone-based resin). The average pore size of the inner circumferential surface of this membrane is smaller than that of the outer circumferential surface; the absorption peak from the hydrophilic resin in the infrared absorption spectrum of the inner circumferential surface... The strength of the inner surface is greater than that of the outer surface, meaning the hydrophilicity of the inner surface is greater than that of the outer surface. Water vapor diffuses from the inner surface (small pores) to the outer surface (large pores). Because the hydrophilicity of the inner surface is greater than that of the outer surface, and the average pore size of the inner surface is extremely small (3-10 nm), the instantaneous amount of water vapor entering is small, thus reducing the water vapor permeation rate. The water vapor permeation rate of this membrane is 6.8-22.3 mg / min / m, thereby reducing the water conversion efficiency of the membrane.

[0006] The patent CN113926316A published by Jiangsu Julan Nanotechnology Co., Ltd. on January 14, 2022 provides a leak-proof and humidifying composite hollow fiber membrane, its preparation method and its application. The membrane prepared by the patent includes an outer hydrophilic layer and an inner hydrophobic layer attached to the inner surface of the outer hydrophilic layer. That is, the area near the outer surface (including the outer surface) is hydrophilic and the area near the inner surface (including the inner surface) is hydrophobic. The pore size of the membrane structure decreases from the outer surface to the inner surface. Because the inner surface of the membrane is a hydrophobic layer with a small pore size (0.005-0.07μm), water vapor is prone to capillary condensation near the inner surface, causing it to condense into water. According to the instruction manual, the design of the inner hydrophobic layer is not conducive to the permeation of water molecules, which can easily cause the condensed water to block the inner surface, reducing the diffusion channels of water vapor and thus greatly reducing the water vapor permeation rate. In addition, the hydrophobic coating on the inner surface of the membrane is prone to separation from the inner surface as the membrane is used for a longer period of time, which affects the various properties of the membrane and makes it unable to meet the requirements of practical applications.

[0007] Therefore, preparing a moisture-permeable hollow fiber membrane with high water conversion efficiency and water vapor permeation rate is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address the aforementioned problems, this invention aims to provide a polysulfone-based moisture-permeable hollow fiber membrane and its preparation method. This hollow fiber membrane exhibits high water conversion efficiency and water vapor permeation rate, thereby improving humidification performance.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] This application provides a polysulfone-based moisture-permeable hollow fiber membrane, comprising a main body, one side of which is a first surface in contact with a dry gas, and the other side is a second surface in contact with moisture. The main body has non-directional tortuous pathways. The average pore size of the first surface is not greater than 100 nm, and the average pore size of the second surface is not less than 0.25 μm. The content of sulfonic acid groups on the first surface is greater than the content of sulfonic acid groups on the second surface, and the difference between the content of sulfonic acid groups on the first surface and the second surface is not less than 1 x 10⁻⁶. -3 ;

[0011] The content P0 of the sulfonic acid groups is calculated by the following formula:

[0012] S0 is the infrared absorption spectrum of the first and second surfaces measured using a Fourier transform infrared spectrometer with infrared attenuated total internal reflection. The infrared spectrum at 1023 cm⁻¹... -1Nearby peak area; S1 is the infrared absorption spectrum of the first and second surfaces measured using an FTIR Fourier transform infrared spectrometer with infrared attenuated total internal reflection, and the peak area at 1578 cm⁻¹ is shown in the infrared spectrum. -1 The peak area in the vicinity; the water conversion efficiency of the hollow fiber membrane is 40%-70%, and the water vapor permeation rate of the hollow fiber membrane is 0.5-3 g / min.

[0013] It should be noted that in this application, the second surface (macropore surface) is in contact with humid air, allowing water vapor to enter the hollow fiber membrane through the second surface and diffuse towards the first surface (micropore surface). The first surface is in contact with dry air, and the water that diffused to the first surface is carried away by the dry air. The content of sulfonic acid groups on the surface of the hollow fiber membrane is one of the main factors determining the surface hydrophilicity of the hollow fiber membrane; that is, the greater the content of sulfonic acid groups on the surface of the hollow fiber membrane, the greater the hydrophilicity. In this application, the content of sulfonic acid groups on the first surface is greater than that on the second surface, meaning that the hydrophilicity of the first surface is greater than that of the second surface. The change in hydrophilicity is one of the driving forces for water vapor movement; water vapor moves from areas of weak hydrophilicity to areas of strong hydrophilicity. Therefore, water vapor on the second surface moves towards the first surface.

[0014] The humidifying film of this application is used in a humidifier. During the humidification process, the temperature of the second surface is greater than that of the first surface. Under the action of the temperature difference, water vapor is further promoted to move from the second surface to the first surface. The second surface of this application has a suitable average pore size and a high content of sulfonic acid groups, which increases the amount of water vapor that instantaneously enters the second surface. The higher temperature of the second surface accelerates the movement of water vapor. Simultaneously, the difference in hydrophilicity between the first and second surfaces increases the driving force for water vapor to move towards the first surface, thus increasing the water vapor permeation rate. The first surface has a suitable average pore size, causing capillary condensation of water vapor near the first surface, resulting in liquid water. This creates a concentration difference with the water concentration on the first surface, allowing water to diffuse from a high concentration to a low concentration. The concentration difference and the high hydrophilicity of the first surface further increase the driving force for water diffusion, promoting water movement towards the first surface. This results in a hollow fiber membrane with a high water vapor permeation rate and high water conversion efficiency. Specifically, the water vapor permeation rate of the hollow fiber membrane is 0.5-3 g / min, and the water conversion efficiency is 40%-70%. It also has a low air throughput, giving the hollow fiber membrane a good humidification effect.

[0015] Furthermore, when the sulfonic acid group content is too high, the heat resistance of the membrane will be significantly reduced. Since the second outer surface of this application is exposed to high temperatures for a long time, and the membrane pores on the second outer surface are relatively large, its pressure resistance is more easily affected by the sulfonic acid group content. Therefore, the sulfonic acid group content on the second outer surface needs to be low to ensure water conversion efficiency while giving it a longer service life.

[0016] In this application, the content of sulfonic acid groups on the first and second surfaces of the hollow fiber membrane can be obtained in the following way. Taking the content of sulfonic acid groups P0 on the first surface as an example, a section of hollow fiber membrane is cut, flattened, and a 1mm sample is taken. 2 The membrane is 1mm by 1mm, with the specific area determined based on the actual situation. Different regions of the hollow fiber membrane are cut into 1mm pieces. 2 A 1mm x 1mm sample was taken. Taking a membrane sample taken from the middle region of a hollow fiber membrane as an example, the infrared absorption spectrum of the first surface was measured using an FTIR Fourier transform infrared spectrometer with infrared attenuation total internal reflection. The sulfonic acid group content P0 of the membrane sample taken from the middle region of the hollow fiber membrane was [value missing] at 1023 cm⁻¹ in the infrared absorption spectrum. -1 The nearby peak area is 1578 cm² -1 The ratio between the nearby peak areas, and the content P0 of sulfonic acid groups in the membrane samples taken from other areas of the hollow fiber membrane were also obtained by the above method. The content P0 of sulfonic acid groups on the first surface of the hollow fiber membrane was taken as the average value of the content P0 of sulfonic acid groups in five samples.

[0017] It is understandable that the 1023 cm⁻¹ in the infrared absorption spectrum... -1 The peaks near the sulfonic acid group refer to the symmetric stretching vibration peaks of the sulfonic acid group O=S=O in the sulfonic acid group. Therefore, the sulfonic acid group peaks in the infrared absorption spectrum are used to characterize the content of sulfonic acid groups on the surface of the hollow fiber membrane. The peak at 1578 cm⁻¹ in the infrared absorption spectrum... -1 The nearby absorption peak is the vibrational absorption peak of the sulfone benzene ring skeleton. As the casting solution separates into phases, the vibrational peak of the benzene ring skeleton remains essentially unchanged; therefore, this peak is used as the internal standard peak. Thus, 1023 cm⁻¹ -1 The nearby peak area is 1578 cm² -1 The ratio of the peak areas in the vicinity can, to some extent, characterize the content of sulfonic acid groups P0 on the surface of the hollow fiber membrane.

[0018] In this application, the difference in sulfonic acid groups between the first surface and the second surface is not less than 1 x 10. -3 A suitable difference in hydrophilicity between the first and second surfaces increases the driving force for water vapor to move from the second surface to the first surface, thereby increasing the permeation rate of water vapor and the water conversion efficiency within the hollow fiber membrane. If the difference in sulfonic acid groups between the first and second surfaces is too small, i.e., the difference in hydrophilicity between the first and second surfaces is small, the driving force for water vapor diffusion to the first surface is reduced, thus decreasing the permeation rate of water vapor and the water conversion efficiency.

[0019] The second surface of this application has a suitable average pore size, allowing a large amount of water vapor to instantaneously enter the membrane. Simultaneously, the second surface has suitable pressure resistance, ensuring the hollow fiber membrane possesses appropriate mechanical strength. If the average pore size of the second surface is too small, the water vapor throughput is reduced, thus affecting the water conversion efficiency.

[0020] The first surface of this application has a suitable average pore size, which increases the speed at which water enters the hollow fiber membrane cavity and effectively reduces the gas throughput; at the same time, it increases the diffusion rate of water vapor to the first surface. If the average pore size of the first surface is too large, the water liquefied by water vapor will re-vaporize into water vapor or will not be liquefied into water, reducing the diffusion rate of water vapor to the first surface and thus reducing the water conversion efficiency.

[0021] In this application, non-directional tortuous pathways refer to irregularly oriented groove structures and / or discretely distributed pore structures, and all non-directional tortuous pathways are interconnected. The average pore size of the membrane surface in this application can be measured by characterizing the membrane structure using a scanning electron microscope, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then performing corresponding calculations. During the membrane fabrication process, in the direction perpendicular to the membrane thickness (if the membrane is a flat sheet, this direction is planar; if the membrane is a hollow fiber membrane, this direction is perpendicular to the radius), its various characteristics, such as pore size distribution, are roughly uniform and basically consistent. Therefore, the average pore size of a portion of the corresponding plane can be used to reflect the overall average pore size of that plane. In actual measurement, the membrane surface can be characterized first using an electron microscope to obtain the corresponding SEM image, and a certain area, such as 1 μm, can be selected. 2 (1μm x 1μm) or 25μm 2 (5μm by 5μm), the specific area size depends on the actual situation. Then, use appropriate computer software or manual measurement to determine the diameter of all holes on this area, and then calculate to obtain the average pore diameter of the surface. Of course, those skilled in the art can also obtain the above parameters through other measurement methods. The above measurement methods are for reference only.

[0022] Preferably, the average pore size W1 of the first surface is 5-80 nm, and the average pore size W2 of the second surface is 0.25-2 μm; the difference between the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface is 5 x 10⁻⁶. -3 -5X10 -2 .

[0023] In this application, the second surface has a suitable average pore size, enabling the hollow fiber membrane to possess appropriate mechanical strength and a suitable amount of water vapor instantaneously entering the membrane. When the average pore size of the second surface is too large, its mechanical strength decreases. When the membrane is subjected to high pressure, the pores near the second surface are prone to collapse, causing membrane deformation or breakage, thus affecting membrane performance. Simultaneously, an excessive amount of water vapor instantaneously entering the hollow fiber membrane through the second surface prevents timely diffusion towards the first surface, easily causing pore blockage and reducing the water permeation rate and water conversion efficiency of the hollow fiber membrane. Furthermore, it increases the amount of gas entering the hollow fiber membrane through the second surface, thereby increasing the amount of gas permeating the hollow fiber membrane. Conversely, a small average pore size on the second surface reduces the water vapor throughput, thus affecting water conversion efficiency. The hollow fiber membrane prepared in this application has a suitable average pore size on its second surface, ensuring sufficient water vapor throughput while reducing gas throughput, and simultaneously meeting the mechanical strength requirements of the second surface, resulting in a membrane with high overall tensile strength.

[0024] In this application, the first surface has a suitable average pore size to ensure that water diffused to the vicinity of the first surface is promptly removed, thereby increasing the water conversion efficiency of the hollow fiber membrane. If the average pore size of the first surface is too large, the gas throughput increases, and the amount of gas occupying the flow channels within the membrane increases, thus reducing the water vapor throughput and consequently reducing the water conversion efficiency of the hollow fiber membrane, while also reducing the mechanical strength of the membrane. If the average pore size of the first surface is too small, water is prone to accumulate in the first surface area and cannot be discharged in time. The accumulated water is prone to flow back into the membrane, reducing the water conversion efficiency.

[0025] In this application, the content of sulfonic acid groups on the first surface and the second surface have a suitable difference, resulting in a suitable difference in hydrophilicity between the two surfaces. This increases the driving force for water vapor to move from the second surface to the first surface, thereby increasing the water vapor permeation rate and water conversion efficiency of the hollow fiber membrane. If the difference between the content of sulfonic acid groups on the first and second surfaces is too large, the water vapor permeation rate to the first surface will be too high, preventing water vapor from diffusing to the first surface in a timely manner. This can easily cause blockage of the flow channels within the hollow fiber membrane, reducing the water conversion efficiency. Conversely, if the difference between the content of sulfonic acid groups on the first and second surfaces is too small, the driving force for water vapor to move from the second surface to the first surface will be reduced, thus decreasing the water conversion efficiency.

[0026] In this application, both the first and second surfaces have suitable average pore sizes, and the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface have a suitable difference, which makes the hollow fiber membrane have a high water vapor permeation rate, water conversion efficiency and mechanical strength, while the hollow fiber membrane has a low gas throughput.

[0027] Preferably, the content P1 of sulfonic acid groups on the first surface is 2 x 10⁻⁶. -3 -8X10 -2 The content of sulfonic acid groups on the second surface, P2, is 2 x 10. -4 -7X10 -3 .

[0028] In this application, the second surface has a suitable content of sulfonic acid groups, i.e., the second surface has suitable hydrophilicity, which allows for a suitable instantaneous water vapor ingress rate, ensuring the water vapor permeation rate and water conversion efficiency of the membrane. If the content of sulfonic acid groups on the second surface is too high, i.e., the second surface has excessive hydrophilicity, the instantaneous water vapor ingress rate on the second surface will be too high, clogging the flow channels and causing water vapor backflow, reducing the water vapor permeation rate and water conversion efficiency of the hollow fiber membrane. At the same time, excessive sulfonic acid group content can easily make the second surface brittle, reducing its mechanical strength. If the content of sulfonic acid groups on the second surface is too low, i.e., the second surface has insufficient hydrophilicity, the instantaneous water vapor ingress rate on the second surface will be reduced, reducing the driving force for water vapor to flow to the first surface; at the same time, the flux of water vapor in the hollow fiber membrane will be reduced, thereby reducing the water conversion efficiency of the hollow fiber membrane.

[0029] In this application, the content of sulfonic acid groups on the first surface is appropriate, that is, the first surface has appropriate hydrophilicity, thereby enabling it to have an appropriate water diffusion rate. If the content of sulfonic acid groups on the first surface is too high, the rate at which water vapor diffuses to the first surface will be too high, while the average pore size of the first surface will be relatively small. Water condensed from the water vapor cannot diffuse to the outside of the first surface in time, which can easily cause blockage of the flow channels near the first surface, forming concentration polarization. At the same time, if the content of sulfonic acid groups is too high, the first surface will become brittle, reducing its mechanical strength, and thus reducing the mechanical strength of the hollow fiber membrane. In addition, excessive hydrophilicity will cause water to accumulate on the first surface, making it difficult to diffuse outward, thus reducing the water conversion efficiency of the hollow fiber membrane. If the content of sulfonic acid groups on the first surface is too low, the hydrophilicity of the first surface will be reduced, reducing the driving force for water vapor to diffuse from the second surface to the first surface, thereby reducing the water vapor permeation rate and water conversion efficiency of the hollow fiber membrane.

[0030] The first and second surfaces of this application have appropriate sulfonic acid group contents so that the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface have an appropriate difference, so as to increase the driving force of water vapor from the second surface to the first surface, thereby increasing the water vapor permeation rate and water conversion efficiency of the hollow fiber membrane; at the same time, the membrane has appropriate thermal stability to improve the service life of the membrane.

[0031] Preferably, the porosity M1 of the first surface is not greater than 5%, and the sulfonation index of the first surface is N1, satisfying the following conditions: N1 is 2 x 10 -3-9X10 -2 ;

[0032] The pore area ratio M2 of the second surface is not less than 10%, and the sulfonation index of the second surface is N2, satisfying the following conditions: N2 is 2 x 10 -4 -8X10 -3 .

[0033] In this application, the first surface possesses a suitable sulfonation index under appropriate pore area ratio and sulfonated group content. The sulfonation index reflects the density of sulfonic acid groups in the solid portion of the first surface. A higher sulfonation index indicates a higher density of sulfonic acid groups and greater hydrophilicity; it also provides suitable compressive strength. If the sulfonation index of the first surface is too high, the density of sulfonic acid groups is excessive, resulting in excessive hydrophilicity. This causes water to easily accumulate on the first surface and is difficult to diffuse into the inner cavity of the hollow fiber membrane. Furthermore, an excessively high sulfonation index can reduce the compressive strength of the first surface, making it brittle and reducing the membrane's service life. Conversely, if the sulfonation index of the first surface is too low, the density of sulfonic acid groups is insufficient, resulting in lower hydrophilicity. This reduces the driving force for water vapor, decreasing the water vapor permeation rate and water conversion efficiency.

[0034] In this application, the second surface, with a suitable pore area ratio and a suitable sulfonic acid group content, possesses an appropriate density of sulfonic acid groups, resulting in suitable hydrophilicity. Combined with a suitable average pore size, this leads to a suitable water vapor permeation rate and water conversion efficiency. Simultaneously, the appropriate density of sulfonic acid groups on the second surface ensures suitable thermal stability and pressure resistance of the membrane. If the sulfonation index N1 of the second surface is too high, the density of sulfonic acid groups is also high, resulting in greater hydrophilicity and increased instantaneous water vapor ingress. Furthermore, water vapor tends to accumulate on the second surface and is less likely to diffuse to the first surface, reducing the water vapor permeation rate and water conversion efficiency. Additionally, excessive density of sulfonic acid groups also reduces the pressure resistance of the second surface. Conversely, if the sulfonation index N1 is too high, the density of sulfonic acid groups is low, resulting in lower hydrophilicity and reduced instantaneous water vapor throughput, thus affecting the membrane's water conversion efficiency.

[0035] In this application, the surface porosity is first determined by characterizing the membrane structure using a scanning electron microscope. Then, an area (e.g., 2cm x 2cm) is measured from the SEM image, and the area of ​​each pore is measured. The total area of ​​all pores within that area is calculated, and the porosity percentage is calculated using the formula (total pore area / area of ​​the defined area) x 100%. The area of ​​each pore is measured by treating each pore as a true circle.

[0036] Preferably, the ratio of the sulfonation index N1 of the first surface to the sulfonation index N2 of the second surface is 2-30.

[0037] In this application, the sulfonation index N1 of the first surface and the sulfonation index N2 of the second surface have a suitable ratio, ensuring a suitable ratio between the density of sulfonic acid groups on the first and second surfaces. This results in a suitable ratio between the amount of water vapor entering the second surface and the amount flowing out of the first surface, thereby achieving a suitable water vapor permeation rate and water conversion efficiency within the membrane. If the ratio of the sulfonation index N1 of the first surface to the sulfonation index N2 of the second surface is too large, the driving force of poor hydrophilicity of water vapor is too strong, leading to an excessively high water vapor permeation rate. This can easily cause water vapor to fail to diffuse to the first surface in a timely manner, resulting in blockage inside the hollow fiber membrane and reducing the water vapor permeation rate and water conversion efficiency. Conversely, if the ratio of the sulfonation index N1 of the first surface to the sulfonation index N2 of the second surface is too small, the driving force for water vapor diffusion is reduced, thereby decreasing the water vapor permeation rate and water conversion efficiency.

[0038] Preferably, the main body includes a support layer and a condensation layer, one side of the support layer is a second surface, one side of the condensation layer is a first surface, and the other side of the support layer and the other side of the condensation layer are connected by continuous fibers; the content of sulfonic acid groups in the condensation layer increases in a gradient from the region near the support layer to the region near the first surface.

[0039] In this application, the condensation layer is the region where water vapor transforms from gas to liquid. The support layer is the region where water vapor permeates into the hollow fiber membrane and diffuses in the form of gas. The term "continuous fiber transition" can be understood as the fibers between the condensation layer and the support layer being "integrated," existing as a continuous whole without additional adhesive bonding. Unless torn by external force, the continuous fibers cannot be separated from each other. Within the condensation layer, the content of sulfonic acid groups increases gradually along the thickness direction from the region near the support layer towards the first surface. The lower the content of sulfonic acid groups, the lower the hydrophilicity. Therefore, the hydrophilicity decreases gradually from the first surface to the second surface along the membrane thickness direction. This means that water within the condensation layer, driven by the hydrophilicity gradient, flows towards the more hydrophilic first surface, thereby increasing the water diffusion rate and consequently increasing the water vapor permeation rate and water conversion efficiency.

[0040] Preferably, the membrane pore size of the main body decreases gradually from one side of the second surface to the side closer to the first surface, while the sulfonic acid group content increases gradually.

[0041] The gradient Z of the sulfonic acid group content is 2 x 10. -5 -8X10 -4 The gradient W of the membrane pore size variation is 1-10 nm / μm.

[0042] In this application, the content of sulfonic acid groups increases gradually from the first surface to the second surface along the film thickness direction. As stated above, the hydrophilicity also increases gradually from the second surface to the first surface along the film thickness direction. This means that water vapor within the hollow fiber membrane flows towards the more hydrophilic first surface due to the hydrophilicity gradient. The appropriate gradient of sulfonic acid group content in this application provides a suitable hydrophilic driving force for water vapor within the membrane, promoting the diffusion of water vapor from the second surface to the first surface at a suitable permeation rate.

[0043] The average pore size in the film thickness direction of this application is based on the formula... The calculations show that Z is the average pore size gradient in nm / μm; P2 is the average pore size of the second surface in nm; P1 is the average pore size of the first surface in nm; and D is the thickness of the hollow fiber membrane in μm. The average pore size in the membrane thickness direction varies in a gradient range of 1-10 nm / μm. Preferably, the average pore size gradient is 2-8 nm / μm. This suitable average pore size gradient range makes the hollow parts formed by the pores in the hollow fiber membrane more uniformly distributed in the gradient change, thus giving the hollow fiber membrane a greater overall tensile strength. Meanwhile, as the average pore size of the hollow fiber membrane varies gradually within a suitable range, it achieves a suitable porosity, which is beneficial to increasing water conversion efficiency and thus enhancing the humidification effect of the membrane. Simultaneously, a suitable gradient in the average pore size variation results in a suitable change in the membrane's solid area. The solid portion of the membrane serves as a carrier for sulfonic acid groups. Therefore, a suitable gradient in the pore size variation of the hollow fiber membrane ensures a suitable gradient in the content of sulfonic acid groups.

[0044] If the gradient of sulfonic acid group content is too large, water vapor diffuses towards the first surface at a high rate. Simultaneously, the closer to the first surface, the smaller the average pore size, which easily leads to pore blockage in the area near the first surface, reducing the water conversion efficiency of the hollow fiber membrane. Conversely, if the gradient of sulfonic acid group content is too small, it reduces the driving force for water vapor diffusion. Furthermore, the closer to the first surface, the larger the average pore size, which easily leads to an increase in gas throughput. In this application, the gradient of sulfonic acid group content is determined according to the formula... The calculations show that W represents the gradient of sulfonic acid group content; W2 represents the content of sulfonic acid groups on the second surface; W1 represents the content of sulfonic acid groups on the first surface; and D represents the thickness of the hollow fiber membrane.

[0045] Preferably, the first water contact angle of the first surface is 45-75°, and the first water contact angle of the second surface is 8-35° larger than the first water contact angle of the first surface. More preferably, the first water contact angle of the second surface is less than 90°.

[0046] In this application, the first water contact angle along the thickness direction of the membrane from the first surface to the outer surface exhibits a gradient increase. Since the water contact angle of the membrane surface is related to its hydrophilicity (i.e., the larger the first water contact angle, the worse the hydrophilicity; the smaller the first water contact angle, the better the hydrophilicity), the hydrophilicity along the thickness direction from the first surface to the outer surface exhibits a gradient decrease. This means that water within the hollow fiber membrane flows towards the more hydrophilic first surface due to the hydrophilicity gradient. When the difference in the first contact angles between the first and second surfaces is large, the water contact angle on the first surface is too small, making it easier for water to be stored on the first surface and less likely to diffuse outwards, thus reducing the humidification effect of the hollow fiber membrane. When the difference in the first contact angles between the first and second surfaces is small, the driving force for water movement within the flow channel decreases, reducing the water conversion efficiency and consequently reducing the humidification effect of the hollow fiber membrane. A contact angle tester was used to test the first water contact angles of the first and second surfaces of the obtained hollow fiber membrane.

[0047] When the first water contact angle of the first surface is small, the first surface has high hydrophilicity, causing water to accumulate in the area near the first surface of the membrane, thereby reducing the water diffusion rate. When the first water contact angle of the first surface is too large, the hydrophilicity in the area near the first surface is low, resulting in a decrease in the water flow velocity in the flow channel near the first surface, thereby reducing the water diffusion rate. The first surface of this application has a suitable first water contact angle, allowing water in the hollow fiber membrane to flow to the first surface at a suitable flow rate, and preventing water accumulation on the first surface, thereby increasing the humidification effect of the membrane.

[0048] When the water contact angle of the second surface is too large, the hydrophobicity near the second surface is greater, reducing the amount of water vapor entering the second surface area. When the water contact angle of the second surface is small, the hydrophilicity near the second surface area is greater, which is not conducive to the diffusion of water vapor to the first surface, thus reducing the water vapor throughput. The second surface of this application has a suitable first water contact angle, allowing water vapor to pass through the second surface in a timely manner, effectively preventing water vapor accumulation in the second surface area, and helping to improve the water conversion efficiency of the hollow fiber membrane. Preferably, the first water contact angle of the second surface is less than 90°, making the second surface hydrophilic to promote water vapor passage; if the first water contact angle of the second surface is greater than 90°, the second surface is hydrophobic, greatly reducing the amount of water vapor entering, thereby reducing the membrane's water vapor permeation rate and water conversion efficiency.

[0049] Preferably, the thickness of the condensation layer is 5-25 μm, and the thickness of the condensation layer accounts for 5%-20% of the thickness of the hollow fiber membrane.

[0050] In this application, the percentage of the condensation layer thickness to the hollow fiber membrane thickness determines the water conversion efficiency and gas throughput. When the percentage is too large, the condensation layer is thicker, slowing the diffusion rate of condensed water within the hollow fiber membrane, thus reducing the water vapor throughput. When the percentage is too small, the condensation layer is thinner. While this accelerates the diffusion rate of condensed water within the hollow fiber membrane, the increased water flow velocity in the channels reduces the gas-blocking effect, increasing the gas throughput. Therefore, a suitable condensation layer thickness and its percentage within the hollow fiber membrane thickness help improve water conversion efficiency while effectively preventing gas permeation. The thickness in this application can be determined by characterizing the membrane structure using a scanning electron microscope, followed by calculation using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement.

[0051] Preferably, the support layer has a macroporous region and a porous region, one side of the macroporous region is a second surface, and one side of the porous region is close to the condensation layer, and the macroporous region and the porous region are connected by continuous fibers; the average pore size of the macroporous region is 1.2-3.2 times the average pore size of the porous region.

[0052] The support layer in this application has various structures, including but not limited to the following. The first type: The support layer contains macroporous and porous regions. One side of the macroporous region is the second surface, and the other side of the porous region is close to the condensation layer. The presence of the macroporous region increases the amount of water vapor that instantaneously enters the membrane. The average pore size of the macroporous region is a suitable multiple of the average pore size of the porous region, ensuring that the amount of water vapor entering the membrane from the macroporous region flows to the condensation layer in a timely manner, thus ensuring the unobstructed flow channels within the support layer. Simultaneously, water vapor enters the porous region at a suitable flow rate, and under the influence of the concentration difference, it is driven to flow towards the first surface. This gives the hollow fiber membrane a large water vapor permeation rate and water conversion efficiency, while also providing suitable mechanical strength. If the multiplier is large, the amount of water vapor entering the porous region instantaneously is large, and the small pores in the porous region cannot allow a large amount of water vapor to pass through in time, which easily leads to concentration polarization and causes water vapor backflow; if the multiplier is small, the driving force for water vapor to flow to the first surface is low, reducing the flow rate of water vapor; the second type: the support layer includes a protection zone and a porous region, with the second surface on one side of the protection zone and the porous region on the other side close to the condensation layer. The average pore size of the porous region is larger than the average pore size of the protection zone, and the average pore size of the protection zone is larger than the average pore size of the condensation layer; the third type: the support layer has an accumulation zone for water vapor accumulation, and the average pore size of the accumulation zone is larger than the average pore size of the second surface.

[0053] Preferably, the average pore size of the macroporous region is 0.5-2.5 μm, the thickness of the macroporous region is 5-20 μm, and the thickness of the macroporous region accounts for 5%-15% of the thickness of the support layer; the macroporous region has fibers forming a porous structure, and the average diameter of the fibers is 0.1-0.4 μm.

[0054] In this application, the macroporous region has a suitable average pore size and thickness to increase the amount of water vapor that instantaneously enters the hollow fiber membrane, while simultaneously ensuring that the second surface has suitable pressure resistance. If the average pore size is too large, the instantaneous water vapor inflow will be excessive, easily leading to concentration polarization near the second surface, thus significantly reducing water conversion efficiency and membrane mechanical strength. If the average pore size is too small, the instantaneous water vapor inflow will be reduced, thereby decreasing the water vapor diffusion rate and reducing water conversion efficiency. If the macroporous region is too thick, the water vapor inflow will be increased, making it difficult for water vapor to flow to the first surface in time, causing channel blockage, backflow, and reducing membrane mechanical strength. If the macroporous region is too thin, the water vapor inflow will be reduced, thereby reducing the driving force for water vapor to flow to the porous region and reducing the water vapor flow velocity.

[0055] The thickness of the macropore region is appropriately proportioned to the thickness of the support layer, ensuring the membrane has suitable water vapor flow rate and mechanical strength. If the proportion is too large, the mechanical strength of the membrane decreases, and the increased water vapor flux prevents it from diffusing to the first surface in time, clogging the flow channels within the membrane and thus reducing water conversion efficiency. If the proportion is too small, the instantaneous inflow of water vapor decreases, thereby reducing the water vapor flux.

[0056] The fibers in the macroporous region have a suitable average diameter, giving the macroporous region appropriate mechanical strength, pore size, and porosity. When the average fiber diameter is large, the average pore size of the porous structure in the macroporous region decreases, leading to more frequent collisions between water vapor molecules and the membrane pore walls, increasing the mass transfer resistance of water vapor. Simultaneously, the porosity of the macroporous region decreases, reducing the porosity of the hollow fibers, and thus reducing the water vapor throughput rate and volume. Conversely, when the average fiber diameter is small, its mechanical strength decreases, thus reducing the mechanical strength of the hollow fiber membrane. At the same time, it increases the average pore size and porosity of the macroporous region, reducing the mass transfer resistance of water vapor, increasing the instantaneous water vapor throughput, and consequently increasing the concentration polarization of water vapor inside and outside the membrane. This causes water vapor to diffuse backward, reducing the water vapor throughput of the hollow fiber membrane.

[0057] Preferably, the average pore size of the porous region is 0.3-1 μm; the thickness of the porous region is 80-105 μm, and the thickness of the porous region accounts for 85%-95% of the thickness of the support layer.

[0058] The porous region of this application has a suitable average pore size, allowing water vapor to pass smoothly through and increasing the water vapor permeation rate. If the average pore size of the porous region is too large, it will reduce the tensile strength of the hollow fiber membrane and increase the water vapor permeation rate within the porous region, causing a large amount of water vapor to flow towards the condensation layer. This can easily lead to a large amount of water vapor accumulating in the condensation layer, blocking the pores, causing water vapor to diffuse backward, and reducing the water conversion efficiency of the hollow fiber membrane. Conversely, if the average pore size of the porous region is too small, it will reduce the water vapor flow rate, thereby reducing the amount of water vapor passing through the hollow fiber membrane.

[0059] The porous region has a suitable thickness, and the ratio between the thickness of the porous region and the thickness of the support layer is appropriate. When the porous region is thicker, its percentage in the support layer is larger, which increases the porosity of the hollow fiber membrane and reduces the tensile strength of the membrane. When the porous region is thinner, its percentage in the support layer is smaller, which reduces the porosity of the hollow fiber membrane, decreases the rate at which water vapor permeates through the hollow fiber membrane, and thus reduces the amount of water vapor that can permeate.

[0060] Preferably, the average pore size of the porous region first increases and then decreases from the region near the large pore region to the region near the condensation layer; the region where the average pore size of the porous region increases is the pore size increase region, and the region where the average pore size of the porous region decreases is the pore size decrease region. The thickness of the pore size increase region is 55-75 μm, and the ratio of the thickness of the pore size increase region to the thickness of the pore size decrease region is 1.5-3.5.

[0061] In this application, the average pore size of the porous region first increases and then decreases from the region near the large pore area towards the region near the condensation layer. Water vapor enters the porous region from the large pore area and flows in a laminar manner. As the pore size increases, the water vapor flow rate gradually increases, increasing the water vapor throughput. As the pore size decreases, the water vapor flow rate gradually decreases, ensuring a suitable flow velocity into the condensation layer and preventing excessive water vapor flow rate from clogging the pores and reducing water conversion efficiency. The pore size-increasing region in this application has an appropriate thickness to improve water vapor flux and permeation rate. The thickness of the pore size-increasing region is in a suitable ratio to the thickness of the pore size-decreasing region, ensuring smooth water vapor flow within the membrane while maintaining a high permeation rate and water conversion efficiency.

[0062] Preferably, the distance between the maximum pore size in the porous region and the first surface is 30-50 μm, and the average pore size at the maximum pore size is 0.4-1.5 μm.

[0063] In this application, the maximum pore size has a suitable average pore size, which is beneficial for increasing the flow rate of water vapor and also helps to concentrate water vapor, preventing excessive flow velocity of water vapor into the condensation layer and thus avoiding blockage of the condensation layer's pores. This results in better water conversion efficiency for the hollow fiber membrane, while also increasing the water vapor transit time and thus increasing time costs. Furthermore, the maximum pore size within the porous region has a suitable distance from the first surface to ensure a sufficiently long path, guaranteeing smooth and unobstructed pore flow.

[0064] Preferably, the hollow fiber membrane has a porosity of 50%-85%, a thickness of 70-150 μm, and an air permeability of no more than 0.7 L / min / m. 2 @80KPa, the tensile strength of the hollow fiber membrane is 4-9MPa, and the elongation at break of the hollow fiber membrane is 40%-120%.

[0065] In this application, the key indicators for evaluating the mechanical strength of hollow fiber membranes are their tensile strength and elongation at break. Under certain conditions, the greater the tensile strength of the hollow fiber membrane, the better its mechanical strength. Tensile strength refers to the membrane's ability to withstand parallel tensile forces. The hollow fiber membranes in this application have a tensile strength of 4-9 MPa and an elongation at break of 40%-120%, indicating that they possess high tensile strength and elongation at break, as well as good pressure resistance. Their mechanical properties are good, their industrial applicability is high, and they fully meet market demands. Under suitable thickness and porosity, the hollow fiber membranes in this application exhibit suitable water vapor permeation rates, water conversion efficiency, and air permeability, with the air permeability not exceeding 0.7 L / min / m. 2 @80KPa indicates that the air passage of the hollow fiber membrane is relatively small.

[0066] This application provides a method for preparing a polysulfone-based moisture-permeable hollow fiber membrane, comprising the following steps:

[0067] S1: Preparation of casting solution and core solution; the casting solution comprises the following components by weight: 10-30 parts of polysulfone polymer, 5-15 parts of hydrophilic additive, 50-75 parts of first organic solvent, and 1-5 parts of sulfonated polyether sulfone; wherein the weight-average molecular weight of the sulfonated polyether sulfone is 20,000-130,000; the degree of sulfonation of the sulfonated polyether sulfone is 5%-35%; the viscosity of the casting solution is 2 x 10⁻⁶. 4 -6X10 4 cps; The core fluid includes a second organic solvent and a non-solvent, wherein the non-solvent is water and its content is 60%-100%;

[0068] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0069] S3: The molded article is initially stretched, wherein the stretching ratio is 1.1-3 times;

[0070] S4: Pre-phase separation, the molded product is pre-phase separated by a constant temperature and humidity device with uniform air blowing, the air humidity in the constant temperature and humidity device is 80%-100%, and the pre-phase separation time is 1-5s.

[0071] S5: Place the pre-separated molded product into a coagulation bath for further phase separation to form a biofilm;

[0072] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0073] Preferably, before preparing the casting solution, the sulfonated polyether sulfone is pretreated by placing it in a drying oven at 50-60°C for 4-8 hours to ensure that the water content of the sulfonated polyether sulfone is not higher than 5%; in step S3, the temperature of the pre-phase separation is 40-60°C; and the air velocity in the pre-phase separation is 0.2-0.8 m / s.

[0074] Preferably, in step S4, the temperature of the coagulation bath is 40-60°C, the re-phase separation time is 20-60s, the coagulation bath is a mixture of water and a third organic solvent, and the water content in the coagulation bath is 50%-95%.

[0075] Preferably, the hydrophilic additive is at least one of polyethylene glycol, polyvinylpyrrolidone, polyethyleneimine, and polyvinyl alcohol; the first organic solvent, the second organic solvent, and the third organic solvent are all at least one of dimethyl sulfoxide, dimethylformamide, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone; and the polysulfone polymer is at least one of polyethersulfone, polysulfone, and polyarylsulfone.

[0076] Before preparing the casting solution, the sulfonated polyethersulfone is dried to reduce its water content, facilitating its diffusion into the core liquid. The casting solution includes a polysulfone polymer, a hydrophilic additive, a first organic solvent, and the sulfonated polyethersulfone. Adding a small amount of sulfonated polyethersulfone to the casting solution further increases the hydrophilicity of the membrane. However, excessively high sulfonated polyethersulfone content can reduce the mechanical strength and brittleness during film formation, thereby decreasing the tensile strength of the hollow fiber membrane. Since the sulfonated polyethersulfone added to the casting solution is water-soluble, according to the principle of "like dissolves like," it gradually migrates into the core liquid, resulting in a higher sulfonated polyethersulfone content on the first surface than on the second surface. The sulfonated polyethersulfone has a suitable weight-average molecular weight, giving it appropriate diffusion capabilities. The degree of sulfonation of sulfonated polyethersulfone represents the amount of sulfonic acid groups grafted onto the polyethersulfone. If the sulfonated polyethersulfone itself has a low degree of sulfonation, the content of sulfonic acid groups in the casting solution will be low, thereby reducing the hydrophilicity of the hollow fiber membrane. If the sulfonated polyethersulfone itself has a high degree of sulfonation, the content of sulfonic acid groups in the casting solution will be high, which will reduce the mechanical strength and brittleness during the film formation process, thereby reducing the tensile strength of the hollow fiber membrane. Therefore, the sulfonated polyethersulfone in the casting solution in this application has a suitable content.

[0077] In addition, the viscosity of the casting solution can be adjusted by adding sulfonated polyethersulfone. In this application, the casting solution has a suitable viscosity, which makes the hollow fiber membrane easier to form, gives the hollow fiber membrane a suitable porosity, and allows the sulfonic acid groups to have a suitable diffusion rate, thereby ensuring a suitable distribution of sulfonic acid groups within the membrane. When the viscosity of the casting solution is high, the diffusion rate of non-solvents into the casting solution is slower, and the phase separation rate also slows down accordingly, increasing the average pore size of the second surface; at the same time, it reduces the diffusion rate of sulfonated polyethersulfone, thereby reducing the content of sulfonic acid groups on the first surface.

[0078] This application employs an appropriate stretching ratio to initially stretch the molded article. Appropriate stretching causes the sulfonated polyethersulfone / polyethersulfone molecular chains to align along the stretching direction, resulting in a more ordered molecular chain arrangement and improved axial strength of the hollow fiber. This effectively avoids the addition of sulfonated polyethersulfone reducing the mechanical strength of the prepared hollow fiber membrane. If the initial stretching ratio is too high, the average pore size of the second surface is easily reduced, thus decreasing the water conversion efficiency of the hollow fiber membrane. Conversely, if the initial stretching ratio is too low, the orientation of the sulfonated polyethersulfone / polyethersulfone molecular chains along the stretching direction is less pronounced, making the hollow fiber membrane more susceptible to mechanical strength reduction due to the addition of sulfonated polyethersulfone.

[0079] During the pre-phase separation process, the constant temperature and humidity device maintains a suitable humidity level. The molded product passes through this device, and the airflow enhances the exchange capacity for phase separation, resulting in a large pore region with a suitable pore structure near the second surface of the prepared hollow fiber membrane. Furthermore, the suitable phase separation time ensures that the large pore region has a suitable thickness. The core liquid has a suitable non-solvent content, enabling rapid phase separation. This results in a suitable pore structure with smaller pores on the first surface. Because the smaller pore structure on the first surface hinders the flow rate of the core liquid, the core liquid gradually accumulates, causing the pore structure to gradually increase in size from the first surface towards the interior of the membrane.

[0080] The green membrane is placed in a coagulation bath with a suitable water content for complete phase separation. As the flow rate of the coagulation bath gradually decreases from the second surface, the coagulation bath gradually accumulates, and the pore structure within the membrane gradually enlarges. As the amount of coagulated bath increases, the flow rate of the coagulation bath accelerates, causing the pore structure to gradually decrease towards the first surface. A suitable viscosity of the casting solution ensures an appropriate diffusion rate for the sulfonic acid groups, resulting in a suitable distribution of sulfonic acid groups within the membrane. Stretching the formed green membrane at a stretching rate of 3-12 m / min effectively prevents pore shrinkage caused by phase separation, serving a shaping function. At a suitable stretching rate, the pore size within the same layer is relatively uniform. A stretching ratio of 1-5 times effectively avoids fiber breakage due to excessive stretching efficiency or poor stretching effect due to insufficient stretching ratio. Finally, the membrane is washed in water and then dried to obtain the hollow fiber membrane.

[0081] The present application provides the following beneficial effects: the hollow fiber membrane exhibits high water conversion efficiency, water vapor permeation rate, and mechanical strength, thus extending its service life. The preparation method provided by this invention allows for the convenient, rapid, and effective preparation of the aforementioned hollow fiber membrane. Attached Figure Description

[0082] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application.

[0083] Figure 1 The image shows a scanning electron microscope (SEM) image of the first surface of the hollow fiber membrane prepared in Example 3, with a magnification of 5000×.

[0084] Figure 2 The image shows a scanning electron microscope (SEM) image of the second surface of the hollow fiber membrane prepared in Example 3, with a magnification of 5000×.

[0085] Figure 3 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 3, with a magnification of 500×.

[0086] Figure 4 The infrared absorption spectrum of the first surface of the hollow fiber membrane prepared in Example 3;

[0087] Figure 5 The infrared absorption spectrum near the second surface in the cross-section of the hollow fiber membrane prepared in Example 3;

[0088] Figure 6 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 3, near the first surface, with a magnification of 10000×.

[0089] Figure 7 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 3, near the second surface, with a magnification of 10000×.

[0090] Figure 8 The image shown is a scanning electron microscope (SEM) image of the cross-section of the hollow fiber membrane prepared in Example 3, near the center, with a magnification of 10000×. Detailed Implementation

[0091] To more clearly illustrate the overall concept of this application, detailed descriptions are provided below using examples. Unless otherwise specified, the raw materials and equipment used in the preparation of the hollow fiber membranes in the following examples are commercially available. Specifically, a Hitachi S-5500 scanning electron microscope was used to characterize the structural morphology of the filter membrane.

[0092] Example 1

[0093] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyethersulfone is pretreated by placing the sulfonated polyethersulfone in a drying oven at 55°C for 6.5 hours; the casting solution comprises the following components by weight: 18 parts polyethersulfone, 13 parts polyethylene glycol, 65 parts dimethyl sulfoxide, and 3.4 parts sulfonated polyethersulfone; the weight-average molecular weight of the sulfonated polyethersulfone is 70,000; the degree of sulfonation of the sulfonated polyethersulfone is 21%; the viscosity of the casting solution is 3.5 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylformamide and water at a concentration of 87%.

[0094] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0095] S3: The molded article is initially stretched, with a stretching ratio of 1.4 times;

[0096] S4: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 92%, the pre-phase separation time is 4.5s, the pre-phase separation temperature is 55℃, and the air flow velocity in the pre-phase separation is 0.4m / s.

[0097] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a green film; the temperature of the coagulation bath is 48°C, the phase separation time is 35s, the coagulation bath is a mixture of water and dimethylacetamide, and the water content in the coagulation bath is 93%.

[0098] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0099] Example 2

[0100] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyethersulfone is pretreated by placing it in a drying oven at 54°C for 5.5 hours; The casting solution comprises the following components by weight: 14 parts polysulfone, 8 parts polyvinylpyrrolidone, 71 parts dimethylformamide, and 1 part sulfonated polyethersulfone; The weight-average molecular weight of the sulfonated polyethersulfone is 45,000; The degree of sulfonation of the sulfonated polyethersulfone is 5%; The viscosity of the casting solution is 2 x 10⁻⁶. 4 CPS; The core fluid consists of dimethyl sulfoxide and 93% water;

[0101] S2: Spinning, where casting solution and core solution are simultaneously extruded from a spinning nozzle to form a molded product with a first surface and a second surface;

[0102] S3: The molded article is initially stretched, with a stretching ratio of 2.3 times;

[0103] S4: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 90%, the pre-phase separation time is 3s, the pre-phase separation temperature is 40℃, and the air flow velocity in the pre-phase separation is 0.2m / s.

[0104] S5: The pre-separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 42℃, the phase separation time is 55s, the coagulation bath is a mixture of water and N-ethylpyrrolidone, and the water content in the coagulation bath is 90%.

[0105] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0106] Example 3

[0107] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyethersulfone is pretreated by placing the sulfonated polyethersulfone in a drying oven at 60°C for 4.5 hours; The casting solution comprises the following components by weight: 16 parts polyarylsulfone, 6 parts polyethyleneimine, 55 parts dimethylacetamide, and 2.2 parts sulfonated polyethersulfone; The weight-average molecular weight of the sulfonated polyethersulfone is 55,000; The degree of sulfonation of the sulfonated polyethersulfone is 15%; The viscosity of the casting solution is 3 x 10⁻⁶. 4 cps; the core fluid consists of N-methylpyrrolidone and 77% water;

[0108] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0109] S3: The molded article is initially stretched, with a stretching ratio of 1.7 times;

[0110] S4: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 100%, the pre-phase separation time is 2.5s, the pre-phase separation temperature is 45℃, and the air flow velocity in the pre-phase separation is 0.75m / s.

[0111] S5: The pre-separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 55℃, the phase separation time is 20s, the coagulation bath is a mixture of water and N-ethylpyrrolidone, and the water content in the coagulation bath is 70%.

[0112] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0113] Example 4

[0114] S1: Preparation of casting solution and core solution; Before preparing the casting solution, sulfonated polyethersulfone is pretreated by placing it in a drying oven at 51°C for 7.5 hours; The casting solution comprises the following components by weight: 12 parts polyarylsulfone, 5 parts polyvinyl alcohol, 74 parts N-ethylpyrrolidone, and 2.8 parts sulfonated polyethersulfone; The weight-average molecular weight of the sulfonated polyethersulfone is 25,000; The degree of sulfonation of the sulfonated polyethersulfone is 17%; The viscosity of the casting solution is 4.5 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylacetamide and 72% water.

[0115] S2: Spinning, where casting solution and core solution are simultaneously extruded from a spinning nozzle to form a molded product with a first surface and a second surface;

[0116] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 2.5 times;

[0117] S4: Pre-phase separation. The molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 98%, the pre-phase separation time is 1.5s, the pre-phase separation temperature is 57℃, and the air flow velocity in the pre-phase separation is 0.3m / s.

[0118] S5: The pre-separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 58℃, the phase separation time is 25s, the coagulation bath is a mixture of water and dimethyl sulfoxide, and the water content in the coagulation bath is 85%.

[0119] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0120] Example 5

[0121] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyether sulfone is pretreated by placing it in a drying oven at 56°C for 6 hours; the casting solution comprises the following components by weight: 28 parts polysulfone, 10 parts polyethyleneimine, 53 parts dimethyl sulfoxide, and 1.6 parts sulfonated polyether sulfone; wherein the weight-average molecular weight of the sulfonated polyether sulfone is 125,000; the degree of sulfonation of the sulfonated polyether sulfone is 13%; the viscosity of the casting solution is 2.5 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylacetamide and 67% water.

[0122] S2: Spinning, where casting solution and core solution are simultaneously extruded from a spinning nozzle to form a molded product with a first surface and a second surface;

[0123] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 1.2 times;

[0124] S4: Pre-phase separation, the molded product is pre-phase separated by passing it through a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 95%, the pre-phase separation time is 4s, the pre-phase separation temperature is 43℃, and the air flow velocity in the pre-phase separation is 0.5m / s.

[0125] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a green film; the temperature of the coagulation bath is 46℃, the phase separation time is 30s, the coagulation bath is a mixture of water and dimethyl sulfoxide, and the water content in the coagulation bath is 75%.

[0126] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0127] Example 6

[0128] S1: Preparation of casting solution and core solution; Before preparing the casting solution, sulfonated polyethersulfone is pretreated by placing it in a drying oven at 53°C for 5 hours; The casting solution comprises the following components by weight: 22 parts polyethersulfone, 7 parts polyvinyl alcohol, 60 parts dimethylformamide, and 4.6 parts sulfonated polyethersulfone; The weight-average molecular weight of sulfonated polyethersulfone is 95,000; The degree of sulfonation of sulfonated polyethersulfone is 34%; The viscosity of the casting solution is 4 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylacetamide and 82% water.

[0129] S2: Spinning, where casting solution and core solution are simultaneously extruded from a spinning nozzle to form a molded product with a first surface and a second surface;

[0130] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 2.7 times;

[0131] S4: Pre-phase separation. The molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 89%, the pre-phase separation time is 3.5s, the pre-phase separation temperature is 58℃, and the air velocity in the pre-phase separation is 0.6m / s.

[0132] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 53°C, the phase separation time is 45s, the coagulation bath is a mixture of water and dimethyl sulfoxide, and the water content in the coagulation bath is 60%.

[0133] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0134] Example 7

[0135] S1: Preparation of casting solution and core solution; Before preparing the casting solution, sulfonated polyethersulfone is pretreated by placing it in a drying oven at 58°C for 7 hours; The casting solution comprises the following components by weight: 26 parts polyarylsulfone, 12 parts polyvinylpyrrolidone, 58 parts dimethylformamide, and 4 parts sulfonated polyethersulfone; The weight-average molecular weight of the sulfonated polyethersulfone is 110,000; The degree of sulfonation of the sulfonated polyethersulfone is 29%; The viscosity of the casting solution is 5 x 10⁻⁶. 4 CPS; The core fluid consists of N-methylpyrrolidone and 98% water;

[0136] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0137] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 2.1 times;

[0138] S4: Pre-phase separation, the molded product is pre-phase separated by passing it through a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 86%, the pre-phase separation time is 2s, the pre-phase separation temperature is 41℃, and the air flow velocity in the pre-phase separation is 0.7m / s.

[0139] S5: The pre-separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 51℃, the phase separation time is 40s, the coagulation bath is a mixture of water and N-ethylpyrrolidone, and the water content in the coagulation bath is 55%.

[0140] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0141] Example 8

[0142] S1: Preparation of casting solution and core solution; Before preparing the casting solution, sulfonated polyethersulfone is pretreated by placing it in a drying oven at 52°C for 8 hours; the casting solution comprises the following components by weight: 20 parts polysulfone, 14 parts polyethylene glycol, 75 parts N-ethylpyrrolidone, and 3.6 parts sulfonated polyethersulfone; the weight-average molecular weight of the sulfonated polyethersulfone is 85,000; the degree of sulfonation of the sulfonated polyethersulfone is 25%; the viscosity of the casting solution is 5.5 x 10⁻⁶. 4 cps; the core fluid consists of N-methylpyrrolidone and 62% water;

[0143] S2: Spinning, where casting solution and core solution are simultaneously extruded from a spinning nozzle to form a molded product with a first surface and a second surface;

[0144] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 2.9 times;

[0145] S4: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 82%, the pre-phase separation time is 1.2s, the pre-phase separation temperature is 59℃, and the air flow velocity in the pre-phase separation is 0.8m / s.

[0146] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a green film; the temperature of the coagulation bath is 45℃, the phase separation time is 60s, the coagulation bath is a mixture of water and dimethylacetamide, and the water content in the coagulation bath is 80%.

[0147] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0148] Comparative Example 1

[0149] S1: Preparation of casting solution and core solution; the casting solution comprises the following components by weight: 18 parts polyethersulfone, 13 parts polyethylene glycol, and 65 parts dimethyl sulfoxide; the viscosity of the casting solution is 3.5 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylformamide and water at a concentration of 87%.

[0150] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0151] S3: The molded article is initially stretched, with a stretching ratio of 1.4 times;

[0152] S4: Pre-phase separation. The molded product undergoes pre-phase separation in a constant temperature and humidity device with uniform airflow. The air humidity in the constant temperature and humidity device is 86%, the pre-phase separation time is 4.5s, the pre-phase separation temperature is 55℃, and the air velocity in the pre-phase separation is 0.4m / s.

[0153] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 48°C, the phase separation time is 35s, the coagulation bath is a mixture of water and dimethylacetamide, and the water content in the coagulation bath is 87%.

[0154] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0155] Compared with Example 1, Comparative Example 1 did not add sulfonated polyethersulfone to the casting solution, which reduced the hydrophilicity of the hollow fiber membrane, greatly reduced the water vapor permeation rate of the hollow fiber membrane, and thus reduced the water conversion efficiency of the hollow fiber membrane.

[0156] Comparative Example 2

[0157] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyethersulfone is pretreated by placing the sulfonated polyethersulfone in a drying oven at 55°C for 6.5 hours; the casting solution comprises the following components by weight: 18 parts polyethersulfone, 13 parts polyethylene glycol, 65 parts dimethyl sulfoxide, and 3.4 parts sulfonated polyethersulfone, the weight-average molecular weight of the sulfonated polyethersulfone is 200,000; the degree of sulfonation of the sulfonated polyethersulfone is 21%; the viscosity of the casting solution is 8 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylformamide and 40% water.

[0158] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0159] S3: Perform preliminary stretching on the molded product, with a stretching ratio of 1.4 times;

[0160] S4: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 92%, the pre-phase separation time is 4.5s, the pre-phase separation temperature is 55℃, and the air flow velocity in the pre-phase separation is 0.4m / s.

[0161] S5: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 48°C, the phase separation time is 35s, the coagulation bath is a mixture of water and dimethylacetamide, and the water content in the coagulation bath is 84%.

[0162] S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0163] Compared with Example 1, Comparative Example 2 increased the viscosity of the casting solution, which greatly reduced the diffusion ability of sulfonic acid groups during the phase separation process. As a result, the content of sulfonic acid groups on the first and second surfaces of the prepared hollow fiber membrane was basically the same, thus reducing the water vapor permeation rate of the hollow fiber membrane and consequently reducing the water conversion efficiency of the hollow fiber membrane.

[0164] Comparative Example 3

[0165] S1: Preparation of casting solution and core solution; Before preparing the casting solution, the sulfonated polyethersulfone is pretreated by placing the sulfonated polyethersulfone in a drying oven at 55°C for 6.5 hours; the casting solution comprises the following components by weight: 18 parts polyethersulfone, 13 parts polyethylene glycol, 65 parts dimethyl sulfoxide, and 3.4 parts sulfonated polyethersulfone; the weight-average molecular weight of the sulfonated polyethersulfone is 70,000; the degree of sulfonation of the sulfonated polyethersulfone is 21%; the viscosity of the casting solution is 3.5 x 10⁻⁶. 4 CPS; The core fluid consists of dimethylformamide and 30% water;

[0166] S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface;

[0167] S3: Pre-phase separation, the molded product is subjected to pre-phase separation in a constant temperature and humidity device with uniform air blowing. The air humidity in the constant temperature and humidity device is 100%, the pre-phase separation time is 4.5s, the pre-phase separation temperature is 55℃, and the air flow velocity in the pre-phase separation is 0.4m / s.

[0168] S4: The pre-phase separated molded product is placed in a coagulation bath for further phase separation to form a film; the temperature of the coagulation bath is 48°C, the phase separation time is 35s, the coagulation bath is a mixture of water and dimethylacetamide, and the water content in the coagulation bath is 93%.

[0169] S5: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

[0170] Compared with Example 1, Comparative Example 3 reduced the water content in the core fluid, thereby reducing the ability of sulfonic acid groups to diffuse to the first surface. This resulted in the content of sulfonic acid groups on the second surface being greater than that on the first surface, and the hydrophilicity of the second surface being greater than that of the first surface. The pore size of the second surface was smaller than the average pore size of the first surface. In addition, Comparative Example 3 did not undergo preliminary stretching, thus greatly reducing the water vapor throughput of the hollow fiber membrane, thereby reducing the water vapor permeation rate and water conversion efficiency of the hollow fiber membrane, and also reducing the mechanical strength of the hollow fiber membrane.

[0171] Performance Experiment

[0172] Structural characterization

[0173] The hollow fiber membranes obtained in each embodiment and comparative example were characterized by longitudinal section, first surface, and second surface morphology. Measurements were also performed on the thickness, average pore size, and fiber diameter of each layer in the main body, as well as the porosity and thickness of the hollow fiber membrane. The measurement data are shown in Tables 1-5. The morphology characterization results for Examples 1-8 are shown in... Figures 1-8 .

[0174] Table 1 Characterization of the first surface structure of hollow fiber membranes in each example

[0175]

[0176] Table 2 Characterization of the second surface structure of hollow fiber membranes in each example

[0177]

[0178] Table 3 Characterization of each example membrane structure

[0179]

[0180] As can be seen from Table 3, the membrane structures prepared in Examples 3-6 all have macroporous regions in the support layer, while the membrane structures prepared in Examples 1-2 and 7-8 do not have macroporous regions in the support layer.

[0181] Furthermore, the membrane structure prepared in Example 7 has an aggregated region in the support layer, wherein the average pore size of the aggregated region is 0.63 μm, the thickness is 49 μm, and the average fiber diameter is 133 nm, while the membrane structures prepared in Examples 1-6 and 8 do not have aggregated regions in the support layer; the membrane structure prepared in Example 8 has a protected zone in the support layer, wherein the average pore size of the protected zone is 158 nm, the thickness is 4 μm, and the average fiber diameter is 141 nm, while the membrane structures prepared in Examples 1-7 do not have a protected zone in the support layer.

[0182] Table 4 Characterization of porous regions in the support layer for each example

[0183]

[0184]

[0185] As can be seen from Table 4, the membrane structures prepared in Examples 3-6 all have porous regions in the support layer, while the membrane structures prepared in Examples 1-2 and 7-8 do not have porous regions in the support layer.

[0186] In addition, for the membranes prepared in Examples 1-2, the average pore size and the distribution of sulfonic acid groups were measured along the membrane thickness direction from the second surface to the first surface; the membranes prepared in Examples 3-8 were not measured. Specifically, the pore size gradient of Example 1 was 1.35 nm / μm, and the sulfonic acid group gradient was 5.8 × 10⁻⁶. -5 In Example 2, the pore size variation gradient was 1.1 nm / μm, and the sulfonic acid group variation gradient was 2.3 x 10⁻⁶. -4 .

[0187] Performance testing

[0188] The tensile strength and elongation of the hollow fiber membranes obtained in each example were tested using a tensile testing machine.

[0189] The water conversion efficiency of the hollow fiber membranes obtained in each example was tested.

[0190] A homemade hollow fiber component was used, with humid air entering through the wet in end and dry air through the dry in end. Digital display thermometers and hygrometers were used to monitor the humidification effect at both the dry out and wet out ends. Different humidification data were obtained by varying the gas flow rates at the dry in and wet in ends. Different humidification data were also obtained by increasing the dry flow pressure by adding a one-way pressure relief valve at the dry out end. Calculation results: Where: D—density of dry gas or wet vapor, unit (g / m³) 3 K1, K2—constants; T—temperature at the dry-in end, dry-out end, wet-in end, or wet-out end of the hollow fiber membrane, in °C; T1—temperature constant, in °C. —Humidity of the dry in end, dry out end, wet in end, or wet out end of the hollow fiber membrane, in %RH.

[0191] V = Q * H Where: V—volume of dry or moist gas, unit (m³) 3 Q—volume flow rate of dry or wet gas, in units of (m³ / s). 3 / h), H—gas flow rate time, in hours.

[0192] m = ρ * v where m—water content at the dry out end or wet in end of the hollow fiber membrane, in g; ρ—density of dry gas or wet vapor, in g / m³. 3 v—volume of dry or moist gas, unit (m³) 3 ).

[0193] In the formula, ω is the water conversion efficiency, m1 is the water content at the dry out end of the hollow fiber membrane (in g), and m2 is the water content at the wet in end of the hollow fiber membrane (in g).

[0194] The air permeability of the hollow fiber membranes obtained in each example was tested using a gas flow meter.

[0195] Table 5 Hollow Fiber Membrane Performance Tests

[0196]

[0197] The above description is merely an embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of this application should be included within the scope of the claims of this application.

Claims

1. A polysulfone-based moisture-permeable hollow fiber membrane, comprising a main body, wherein one side of the main body is a first surface in contact with a dry gas, and the other side is a second surface in contact with moisture, characterized in that, The body has a non-directional tortuous path, the average pore size of the first surface is not greater than 100 nm, and the average pore size of the second surface is not less than 0.25 μm; The content of sulfonic acid groups on the first surface is greater than the content of sulfonic acid groups on the second surface, and the difference between the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface is not less than 1 x 10⁻⁶. -3 ; The content P0 of the sulfonic acid groups is calculated by the following formula: S0 is the infrared absorption spectrum of the first and second surfaces measured using a Fourier transform infrared spectrometer with infrared attenuated total internal reflection. The infrared spectrum at 1023 cm⁻¹... -1 Nearby peak area; S1 is an infrared absorption spectrum of the first and second surfaces measured using a Fourier transform infrared spectrometer with infrared attenuated total internal reflection. The infrared spectrum at 1578 cm⁻¹... -1 Nearby peak area; The hollow fiber membrane has a water conversion efficiency of 40%-70% and a water vapor permeation rate of 0.5-3 g / min.

2. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that... The average pore size of the first surface is 5-80 nm, and the average pore size of the second surface is 0.25-2 μm; the difference between the content of sulfonic acid groups on the first surface and the content of sulfonic acid groups on the second surface is 5 x 10⁻⁶. -3 -5X10 -2 .

3. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that, The content of sulfonic acid groups on the first surface, P1, is 2 x 10. -3 -8X10 -2 The content of sulfonic acid groups on the second surface, P2, is 2 x 10. -4 -7X10 -3 .

4. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that, The porosity M1 of the first surface is not greater than 5%, the sulfonation index of the first surface is N1, and the following conditions are met: N1 is 2 x 10 -3 -9X10 -2 ; The pore area ratio M2 of the second surface is not less than 10%, and the sulfonation index of the second surface is N2, satisfying the following conditions: N2 is 2 x 10 -4 -8X10 -3 .

5. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 4, characterized in that, The ratio of the sulfonation index N1 of the first surface to the sulfonation index N2 of the second surface is 2-30.

6. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that, The main body includes a support layer and a condensation layer. One side of the support layer is a second surface, and one side of the condensation layer is a first surface. The other side of the support layer and the other side of the condensation layer are connected by continuous fibers. The content of sulfonic acid groups in the condensation layer increases in a gradient from the region near the support layer to the region near the first surface.

7. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 6, characterized in that, The membrane pore size of the main body decreases gradually from one side of the second surface to the side closer to the first surface, while the sulfonic acid group content increases gradually. The gradient Z of the sulfonic acid group content is 2 x 10. -5 -8X10 -4 ; The gradient W of the membrane pore size variation is 1-10 nm / μm.

8. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that, The first water contact angle of the first surface is 45-75°, and the first water contact angle of the second surface is 8-35° larger than that of the first surface.

9. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 6, characterized in that, The thickness of the condensation layer is 5-25 μm, and the thickness of the condensation layer accounts for 5%-20% of the thickness of the hollow fiber membrane.

10. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 6, characterized in that, The support layer has a macroporous region and a porous region. One side of the macroporous region is a second surface, and the other side of the porous region is close to the condensation layer. The macroporous region and the porous region are connected by continuous fibers. The average pore size of the macroporous region is 1.2-3.2 times that of the average pore size of the porous region.

11. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 10, characterized in that, The average pore size of the macroporous region is 0.5-2.5 μm, the thickness of the macroporous region is 5-20 μm, and the thickness of the macroporous region accounts for 5%-15% of the thickness of the support layer; the macroporous region has fibers forming a porous structure, and the average diameter of the fibers is 0.1-0.4 μm.

12. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 10, characterized in that, The average pore size of the porous region is 0.3-1 μm; the thickness of the porous region is 80-105 μm, and the thickness of the porous region accounts for 85%-95% of the thickness of the support layer.

13. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 10, characterized in that, The average pore size of the porous region first increases and then decreases from the region closer to the large pore region to the region closer to the condensation layer. The region in which the average pore size of the porous region increases is called the pore size increase region, and the region in which the average pore size of the porous region decreases is called the pore size decrease region. The thickness of the pore size increase region is 55-75 μm, and the ratio of the thickness of the pore size increase region to the thickness of the pore size decrease region is 1.5-3.

5.

14. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 10, characterized in that, The distance between the maximum pore size in the porous region and the first surface is 30-50 μm, and the average pore size at the maximum pore size is 0.4-1.5 μm.

15. The polysulfone-based moisture-permeable hollow fiber membrane according to claim 1, characterized in that, The hollow fiber membrane has a porosity of 50%-85%, a thickness of 70-150 μm, and an air permeability of no more than 0.7 L / min / m. 2 @80KPa, the tensile strength of the hollow fiber membrane is 4-9MPa, and the elongation at break of the hollow fiber membrane is 40%-120%.

16. The method for preparing a polysulfone-based moisture-permeable hollow fiber membrane according to any one of claims 1-15, characterized in that, Includes the following steps: S1: Preparation of casting solution and core solution; The casting solution comprises the following components by weight: 10-30 parts of polysulfone polymer, 5-15 parts of hydrophilic additive, 50-75 parts of first organic solvent and 1-5 parts of sulfonated polyethersulfone. The sulfonated polyether sulfone has a weight-average molecular weight of 20,000-130,000 and a degree of sulfonation of 5%-35%. The viscosity of the casting solution is 2 x 10⁻⁶. 4 -6X10 4 cps; The core fluid includes a second organic solvent and a non-solvent, wherein the non-solvent is water and its content is 60%-100%; S2: Spinning, the casting solution and the core solution are simultaneously extruded from the spinning nozzle to form a molded article having a first surface and a second surface; S3: The molded article is initially stretched, wherein the stretching ratio is 1.1-3 times; S4: Pre-phase separation, the molded product is pre-phase separated by a constant temperature and humidity device with uniform air blowing, the air humidity in the constant temperature and humidity device is 80%-100%, and the pre-phase separation time is 1-5s. S5: Place the pre-separated molded product into a coagulation bath for further phase separation to form a biofilm; S6: The raw film is stretched, washed in water, and finally dried to obtain a hollow fiber membrane.

17. The method for preparing a polysulfone-based moisture-permeable hollow fiber membrane according to claim 16, characterized in that, Before preparing the casting solution, the sulfonated polyether sulfone is pretreated by placing it in a drying oven at 50-60°C for 4-8 hours to ensure that the water content of the sulfonated polyether sulfone is not higher than 5%. In step S3, the temperature of the pre-phase separation is 40-60℃; the air velocity in the pre-phase separation is 0.2-0.8m / s.

18. The method for preparing a polysulfone-based moisture-permeable hollow fiber membrane according to claim 16, characterized in that, In step S4, the temperature of the coagulation bath is 40-60℃, the re-phase separation time is 20-60s, the coagulation bath is a mixture of water and a third organic solvent, and the water content in the coagulation bath is 50%-95%.

19. The method for preparing a polysulfone-based moisture-permeable hollow fiber membrane according to claim 16, characterized in that, The hydrophilic additive is at least one of polyethylene glycol, polyvinylpyrrolidone, polyethyleneimine, and polyvinyl alcohol; The first organic solvent, the second organic solvent, and the third organic solvent are all at least one of dimethyl sulfoxide, dimethylformamide, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone; The polysulfone polymer is at least one of polyethersulfone, polysulfone, and polyarylsulfone.

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