A sulfone-based polymer hollow fiber ultrafiltration membrane, a preparation method and application thereof, and an assembly with the ultrafiltration membrane

Abstract

The application provides a sulfone polymer hollow fiber ultrafiltration membrane and a preparation method and application thereof and an assembly with the ultrafiltration membrane, and the sulfone polymer hollow fiber ultrafiltration membrane has a specific structure with values of the SEM average pore size of an outflow surface, the SEM average pore size of an inflow surface, the ratio of the SEM average pore size of the outflow surface to the SEM average pore size of the inflow surface, the overall pore size of the ultrafiltration membrane and the porosity of the specific range, and still has a good overall membrane flux, meanwhile, the effects of excellent pressure resistance of the outflow surface of the membrane, excellent mechanical strength of the overall membrane and reduction of the risk of pollution of the outflow surface are achieved, further, the sulfone polymer hollow fiber ultrafiltration membrane prepared has excellent adhesive force between the membrane filaments when the membrane is processed into an assembly, the quality and the preparation success rate of the hollow fiber assembly are improved, and the biological ultrafiltration under harsh conditions can be met.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, and more specifically to a sulfone polymer hollow fiber ultrafiltration membrane, its preparation method and application, and a component incorporating the ultrafiltration membrane. Background Technology

[0002] The biopharmaceutical industry is closely related to life and health and has always occupied an important position in national economic development. Because biopharmaceutical manufacturing is inseparable from ultrafiltration (including clarification filtration, product concentration, pyrogen removal, small molecule impurity removal, desalination, and buffer exchange), ultrafiltration membranes play a crucial role in the development of the biopharmaceutical industry.

[0003] Ultrafiltration membranes are a type of membrane manufactured using organic polymers as raw materials through specific processes. Based on the type of polymer, polymer ultrafiltration membranes can be further subdivided into cellulose-based polymer ultrafiltration membranes, polyethylene-based polymer ultrafiltration membranes, polyamide-based polymer ultrafiltration membranes, sulfone-based polymer ultrafiltration membranes, etc.; based on membrane geometry, they are classified into plate ultrafiltration membranes (flat-sheet ultrafiltration membranes) and hollow fiber ultrafiltration membranes, etc. Hollow fiber ultrafiltration membranes, in particular, are widely used for the separation and purification of various biomolecules due to their advantages such as minimal damage to biomolecules and excellent separation performance. Especially sulfone-based polymer hollow fiber ultrafiltration membranes, compared to other polymer hollow fiber ultrafiltration membranes, have better high-temperature resistance and biocompatibility, making them more favored in biopharmaceutical ultrafiltration processes.

[0004] Existing technologies disclose numerous sulfone polymer hollow fiber ultrafiltration membranes, most of which feature an inner inlet surface skin and an outer surface with open macropores. Specifically, the inner inlet surface has very small pore sizes and low pore density, while the outer surface has large pore sizes and high pore density. This membrane structure allows the substances to be intercepted to be primarily blocked at or near the inner inlet surface, while simultaneously exhibiting low filtration resistance and high flux. This achieves a balance between ultrafiltration membrane retention efficiency and flux (this is almost universally recognized as the ideal inner and outer inlet / outlet surface structure in the ultrafiltration membrane industry); for example, publication number CN16847. Chinese Patent No. 27A (application filed by Asahi Kasei Medical Co., Ltd.) discloses a hollow fiber plasma purification membrane in a plasma purification membrane and plasma purification system. The membrane is prepared from aromatic polysulfone and polyvinylpyrrolidone and has a sponge structure. In this structure, the pore size continuously decreases from the outer liquid surface of the membrane to the inner liquid surface. The outer liquid surface has circular or elliptical pores with an average pore size of 1 μm or more (the membrane pores on the outer liquid surface are larger), and the porosity of the outer liquid surface of the membrane is 10% or more, thereby exhibiting excellent permeability and classification performance.

[0005] However, continuous research has revealed that ultrafiltration with this type of membrane pore structure also has certain drawbacks. Due to the large number and size of pores at the liquid outlet of the ultrafiltration membrane, the pressure resistance of the liquid outlet is easily reduced (and even the overall mechanical strength of the membrane fibers is reduced). When the liquid outlet is subjected to external forces, the membrane pores are prone to collapse or deformation, which greatly increases the difficulty of manufacturing the membrane fibers into membrane modules. For example, some membrane fibers have poor mechanical strength and can only be manufactured into membrane modules by applying adhesive to each individual membrane fiber, which consumes a lot of manpower and resources. Therefore, there is an urgent need to develop a hollow fiber ultrafiltration membrane with high flux and high pressure resistance at the liquid outlet as well as high overall mechanical strength. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a sulfone polymer hollow fiber ultrafiltration membrane, its preparation method and application, and a component incorporating the ultrafiltration membrane. The ultrafiltration membrane has a relatively small pore density at the outlet liquid surface, but by controlling the structure of the outlet liquid surface to have a suitable pore size, the inlet liquid surface and outlet liquid surface to have an appropriate ratio of pore density to pore size, and the membrane as a whole to have a suitable porosity and pore size, a good overall flux of the membrane is achieved, while the pressure resistance of the outlet liquid surface and the overall mechanical strength of the membrane are both improved.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a sulfone polymer hollow fiber ultrafiltration membrane, comprising a main body, one side of which is an inner liquid inlet surface facing the inner cavity, and the other side of which is an outer liquid outlet surface. The main body has a non-directional tortuous pathway, and the outer liquid outlet surface includes a plurality of first pores. The SEM average pore size of the first pores is 50 nm-1000 nm, and the pore density of the outer liquid outlet surface is 20 pores / 25 μm. 2 -200 pieces / 25μm 2 The inner liquid inlet surface includes a plurality of second pores, the ratio of the SEM average pore diameter of the second pores to the SEM average pore diameter of the first pores is 1:2-10; the ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid inlet surface is 0.8-15; the overall porosity of the ultrafiltration membrane is 30%-80%.

[0008] The ultrafiltration membrane of this invention is prepared from sulfone polymers, which possess excellent mechanical properties, thermal stability, biocompatibility, and ease of phase separation and pore formation. Those skilled in the art, when developing biological ultrafiltration membranes, generally desire membrane structures with small and few pores on the inlet surface and large and significantly more pores on the outlet surface than on the inlet surface. Such a membrane structure facilitates the capture of substances to be intercepted primarily at and near the inlet surface, while simultaneously exhibiting low filtration resistance and high flux, thus achieving a balance between ultrafiltration membrane retention efficiency and flux. Similarly, those skilled in the art generally believe that if the number of pores on the outlet surface is too small—that is, similar to (especially less than) the number of pores on the inlet surface—it will significantly affect the overall flux of the ultrafiltration membrane, leading to excessively low overall flux and consequently impacting filtration efficiency. However, the inventors of this invention, through continuous research, have discovered that even with a small number of pores on the outlet surface, a specific ultrafiltration membrane structure can still achieve a good overall flux and high filtration efficiency. Firstly, the specific membrane structure mentioned above refers to pores with suitable pore sizes on both the inlet and outlet liquid surfaces. The average SEM pore size of the first pore on the outlet liquid surface is controlled to be 50-1000 nm, and the ratio of the average SEM pore size of the second pore on the inlet liquid surface to the pore size of the first pore on the outlet liquid surface is controlled to be 1:2-10. That is, both the first and second pores have suitable pore sizes, and the pore size of the first pore is larger than that of the second pore, with a suitable ratio between the pore sizes of the second and first pores. This ensures that the substances to be intercepted are captured on the inlet liquid surface while also ensuring adequate flow. The specific membrane structure mentioned above refers to an ultrafiltration membrane with an overall porosity of 30%-80%. Overall porosity primarily reflects the overall structural characteristics of the membrane, meaning the ultrafiltration membrane described in this invention has a relatively large number of pores. Furthermore, the ultrafiltration membrane described in this invention refers to a membrane with a porosity of 1kD-750kD. Preferably, the ultrafiltration membrane described in this invention is a membrane with a porosity of 1kD-100kD, and more preferably, the ultrafiltration membrane described in this invention is a membrane with a porosity of 5kD-100kD. This means the pore size of the membrane is relatively small. In other words, the ultrafiltration membrane of this invention has a suitable number of pores and a suitable pore size, which is beneficial for ensuring the flux requirement. Based on the membrane structure containing the specific pore size of the first pore, the ratio of the pore size of the second pore to the pore size of the first pore, and the overall pore number and size characteristics of the membrane, the pore density at the external liquid surface is controlled to be 20 pores / 25μm. 2 -200 pieces / 25μm 2The ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid outlet surface is 0.8-15. This means that even when the number of pores on the outer liquid outlet surface is slightly more or even less than the number of pores on the inner liquid inlet surface, the membrane still maintains good overall flux. However, the number of pores on the outer liquid outlet surface cannot be too low, as this would prevent the flux from meeting filtration requirements and thus affect filtration efficiency. Therefore, in this invention, the pore density of the outer liquid outlet surface is set to 20 pores / 25μm. 2 -200 pieces / 25μm 2 The ratio of the pore density of the inner liquid surface to the pore density of the outer liquid surface is 0.8-15. With the support of the above-mentioned specific membrane structure, a good overall membrane flux is still obtained. This overcomes the technical bias of the prior art and is therefore innovative.

[0009] Because the pore density of the outgoing liquid surface in this invention is relatively small, meaning the number of first pores on the outgoing liquid surface is relatively low, this, combined with the certain pore size of the first pores, results in higher pressure resistance of the outgoing liquid surface, thereby improving the overall mechanical strength of the membrane. Simultaneously, it reduces membrane fouling on the outgoing liquid surface. This is because if the pore density on the outgoing liquid surface is greater than 200 pores / 25μm... 2 When there are a relatively large number of pores on the outgoing liquid surface, the pressure resistance of the outgoing liquid surface will decrease. Under normal operating pressure, the ultrafiltration membrane will collapse due to insufficient pressure resistance, failing to meet practical requirements. At the same time, if the membrane is in a non-clean environment before being prepared into a hollow fiber membrane module, various small particles in the air can easily enter the membrane fibers through the membrane pores on the outgoing liquid surface, thereby increasing the probability of membrane fiber contamination. This will cause membrane pore blockage, reduce membrane flux, and affect the cleanliness of subsequent products.

[0010] Furthermore, since membrane fibers are typically bonded together using colloids when fabricating membrane modules, the hollow fiber ultrafiltration membrane prepared in this invention uses sulfone polymers as raw materials. To ensure protein yield, these polymers have high hydrophilicity, with surface energies generally not less than 60 mN / m. Commonly used polymers PP and PE have surface energies of around 30 mN / m, while colloids typically have surface energies below 50 mN / m. Because colloids exhibit better adhesion when bonded to polymers with higher surface energies than to polymers with lower surface energies, the membrane fibers exhibit relatively good adhesion when using sulfone polymers as raw materials to prepare hollow fiber membranes and subsequently process them into hollow fiber modules. Simultaneously, the inventors of this application unexpectedly discovered a pore density of 20 pores / 25 μm at the liquid surface. 2 -200 pieces / 25μm 2The synergistic effect of the SEM average pore size of the first pore on the outgoing liquid surface being 50-1000 nm can maintain strong adhesion between membrane fibers, while preventing excessive clogging of membrane pores or even the inner cavity of membrane fibers by colloids, thus avoiding waste of membrane fibers. During the research process, the inventors of this application discovered that when the pore density on the outgoing liquid surface is less than 20 pores / 25 μm... 2 When the average SEM pore size of the first pore at the liquid outlet is less than 50 nm, insufficient adhesion between membrane fibers leads to detachment, affecting the strength of the membrane fibers in the hollow fiber module and thus the filtration efficiency. Simultaneously, when the pore density at the liquid outlet is higher than 200 pores / 25 μm... 2 If the average pore size of the first pore at the liquid surface is greater than 1000 nm by SEM, the amount of colloid entering the pore will be too large. Although it can increase the bonding strength between membrane fibers, it will block the membrane pores too much or even further block the inside of the membrane fibers, which will not meet the liquid feed requirements of the ultrafiltration process. Usually, the blocked inner cavity area needs to be cut and the membrane fibers resealed, resulting in waste of membrane fibers.

[0011] In summary, the inventors of this application, through technical means of controlling the SEM average pore size of the membrane's outgoing liquid surface, the ratio of the SEM average pore size of the incoming liquid surface to the SEM average pore size of the outgoing liquid surface, and the overall porosity and pore size of the ultrafiltration membrane, have achieved the goal of ensuring the flux of the ultrafiltration membrane even with a relatively low pore density (fewer pores) on the outgoing liquid surface. This overcomes the technical bias of low membrane flux when the number of pores on the outgoing liquid surface is too small. At the same time, the lower pore density on the outgoing liquid surface results in excellent pressure resistance, improved overall mechanical strength of the membrane, and reduced risk of fouling of the outgoing liquid surface. Furthermore, the synergistic effect of the specific outgoing liquid surface pore density and the SEM average pore size of the first pore results in strong adhesion between the membrane fibers of the prepared hollow fiber module, thereby improving the strength of the membrane fibers in the prepared hollow fiber module, increasing filtration efficiency, and meeting the needs of practical applications.

[0012] During membrane fabrication, in the direction perpendicular to the membrane thickness (if the membrane is a flat sheet, this direction is planar; if it is a hollow fiber membrane, this direction is perpendicular to the radius), its characteristics, such as pore size, are roughly uniform and consistent. Therefore, the overall pore size on a given plane can be reflected by the pore size in a specific region of that plane. The pore density on the outer liquid surface and the inner liquid surface of the ultrafiltration membrane can be characterized using scanning electron microscopy, followed by measurement and calculation using computer software (such as Matlab, NIS-Elements, etc.) or manually. When measuring the pore density on the outer and inner liquid surfaces of the ultrafiltration membrane, the outer and inner liquid surfaces can first be characterized using a microscope (for hollow fiber membranes, the outer liquid surface should be magnified at a level that clearly identifies the shape of as many pores as possible, such as 5000x, 10000x, 20000x, etc.) to obtain the corresponding SEM images. Since the pore size on the outer and inner liquid surfaces is roughly uniform, a certain area, such as 400 μm, is selected. 2 (20μm x 20μm), 225μm 2 (15μm x 15μm), 100μm 2 (10μm x 10μm), 25μm 2 (5μm x 5μm), 1μm 2 (1μm multiplied by 1μm), the specific area size depends on the actual situation, then count the number of holes on the selected area, calculate the pore density on the selected area, conduct several tests (preferably more than 10 times, the specific number depends on the situation), take the average value, and that is the pore density value of the outer liquid surface and the inner liquid surface. The average SEM pore size of the first hole on the outgoing liquid surface is also determined using a scanning electron microscope. The outgoing liquid surface of the hollow fiber membrane is photographed at a magnification (e.g., 5000x, 10000x, 20000x) to clearly identify the shape of as many pores as possible, obtaining the corresponding SEM image. The pores formed on the outgoing liquid surface are circular, elliptical, or nearly elliptical in shape. Using appropriate computer software or manually, the longest line segment connecting two points on the outer periphery of the hole is measured as the major axis. Then, the longest line segment connecting two points on the outer periphery of the hole perpendicularly to the major axis is measured as the average SEM pore size of the first hole. Several tests are performed (preferably more than 10 times, the specific number depending on the situation), and the average value is calculated as the average SEM pore size of the first hole described in this invention. The average SEM pore size of the second hole on the ingoing liquid surface is also determined using the same testing method as the average SEM pore size of the first hole on the outgoing liquid surface. Of course, those skilled in the art can obtain the above parameters through other measurement methods; the above measurement methods are for reference only.

[0013] The non-directional tortuous pathways of the present invention refer to randomly oriented groove structures and / or discretely distributed hole structures, and each non-directional tortuous pathway is interconnected.

[0014] The aforementioned "several holes" refers to two or more holes.

[0015] The pore density refers to the number of pores within a certain area, for example, 1 μm. 2 (1μm×1μm), 4μm 2 (2μm×2μm), 9μm 2 (3μm×3μm), 16μm 2 (4μm×4μm), 25μm 2 (5μm×5μm)... The number of pores within the area.

[0016] Commonly used methods for testing porosity include mercury intrusion porosimetry, density method, and wet-dry film weighing method. Of course, those skilled in the art can also obtain the above parameters through other testing methods. The above testing methods are for reference only.

[0017] As a further improvement of the present invention, the SEM average pore size of the second hole is 3nm-450nm; the pore density of the inner liquid inlet surface is 30 pores / 25μm. 2 -800 pieces / 25μm 2 ; and / or, the ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid outlet surface is 1.1-10.

[0018] In biological ultrafiltration, most substances to be intercepted are captured at or near the inlet liquid surface. Therefore, the SEM average pore size of the second pore has a significant impact on the overall retention efficiency of the membrane. In this invention, the SEM average pore size of the second pore is controlled to be 3nm-450nm, preferably 5nm-300nm, and more preferably 8nm-200nm. This pore size is suitable for the sufficient capture of biomacromolecules. In practical applications, the pore size of the second pore can be adjusted according to different needs to ensure retention efficiency. Since the ultrafiltration membrane of this invention is an internal pressure filtration system, it is necessary to control the number of pores on the inlet liquid surface. Through research, the pore density of the second pores on the inlet liquid surface is controlled to be 30 pores / 25μm. 2 -800 pieces / 25μm 2With the second pore on the inner liquid inlet surface having a suitable pore size, the inner liquid inlet surface has a suitable surface pore area ratio. On the one hand, this ensures that the inner liquid inlet surface has good pressure resistance, and can guarantee the stability of the second pore during long-term internal pressure filtration, making it less prone to collapse or deformation. On the other hand, it minimizes the impact of the relatively dense inner liquid inlet surface on the overall membrane flux, preventing the overall membrane flux from being too low. Based on the second pore with a preferred pore size and number on the inner liquid inlet surface, we further adjust the ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid inlet surface to 1.1-10. That is, we want the number of first pores on the outer liquid inlet surface to be less than the number of second pores on the inner liquid inlet surface. This further ensures the pressure resistance of the outer liquid inlet surface of the membrane, thereby making the membrane as a whole have higher pressure resistance. At the same time, it further reduces the possibility of ultrafiltration membrane fouling and reduces various problems caused by adhesive clogging of membrane pores during the assembly of membrane fibers into modules.

[0019] As a further improvement of the present invention, the surface energy of the liquid surface outside the ultrafiltration membrane is not less than 60mN / m, preferably 65mN / m-90mN / m; the roughness of the liquid surface outside the ultrafiltration membrane is 3μm-50μm, preferably 5μm-35μm;

[0020] The average SEM pore size of the first pore is 80nm-400nm, and the pore density at the outer liquid surface is 25 pores / 25μm. 2 -150 pieces / 25μm 2 .

[0021] As is well known, the hydrophilicity and hydrophobicity of ultrafiltration membranes have a significant impact on the yield of protein products. Generally, the better the hydrophilicity of the membrane, the higher the yield of protein products. Therefore, in this invention, the ultrafiltration membrane also needs to be relatively hydrophilic. Through research, it has been found that when the surface energy of the outer liquid surface of the ultrafiltration membrane is controlled to be no less than 60 mN / m, preferably 65 mN / m-90 mN / m, it has good hydrophilicity, thereby ensuring the product yield. However, in this invention, we also do not want the outer liquid surface to be too hydrophilic (especially when protein products are basically captured by the inner liquid surface during concentration and purification). If the outer liquid surface is too hydrophilic, on the one hand, it may aggravate membrane fouling. Increased hydrophilicity can easily lead to increased interaction forces between the outer liquid surface and contaminants, thereby increasing the adsorption of contaminants on the membrane surface. On the other hand, it will make it easier for colloids to penetrate into the interior of the ultrafiltration membrane, increasing the colloid blockage of the membrane pore structure, resulting in low membrane flux and low dirt holding capacity.

[0022] Based on the appropriate surface energy of the liquid surface outside the membrane, the roughness of the liquid surface is further adjusted to 3μm-50μm. The lower roughness and smoother surface of the liquid surface help reduce the area for contaminant particles to adhere, while weakening the interaction force between contaminants and the membrane surface, effectively reducing the accumulation of contaminants on the membrane surface and improving the membrane's antifouling performance. At the same time, it allows a certain amount of colloid to penetrate into the membrane, ensuring adhesion, without causing membrane pore blockage or increasing processing difficulty, and allowing the membrane fibers to be firmly bonded together by the colloid phase.

[0023] Based on the appropriate surface energy and roughness of the outgoing liquid surface, the membrane pore structure on the outgoing liquid surface is further controlled. The average SEM pore size of the first pore is further optimized to be 80-400 nm, and the pore density of the outgoing liquid surface is 25 pores / 25 μm. 2 -150 pieces / 25μm 2 These features work synergistically to give the outgoing liquid surface excellent pressure resistance, as well as better membrane fiber bonding strength and lower membrane fouling.

[0024] The surface energy was measured using a dyne pen; the roughness was measured using a super depth-of-field 3D microscope; of course, those skilled in the art can also obtain the above parameters through other testing methods, and the above testing methods are for reference only.

[0025] As a further improvement of the present invention, in the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore size of the main body of the ultrafiltration membrane first increases and then decreases; the main body includes a macroporous region, the nearest average distance A from the macroporous region to the outer liquid outlet surface is not less than 15 μm; and the nearest average distance B from the macroporous region to the inner liquid inlet surface is not less than 15 μm, and the overall porosity of the ultrafiltration membrane is 35%-70%.

[0026] In the sulfone polymer hollow fiber ultrafiltration membrane main structure provided by this invention, it can be clearly seen that in the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore size of the main body first increases and then decreases. This changing membrane pore structure results in a large pore region in the main membrane structure. The large pore region can be considered as the area with the largest pore size inside the membrane. The ratio of the SEM average pore size of the large pore region to the SEM average pore size of the first pore is not less than 1.5. The presence of the large pore region can further increase the overall flux of the membrane, making the ultrafiltration membrane prepared by this invention have a better overall flux. At the same time, since the large pore region is the area with larger pores inside the membrane, if the large pore region is too close to the inner liquid inlet surface or the outer liquid outlet surface, it is easy to cause the first pore and the second pore to become larger. The collapse and deformation of the membrane significantly affect the stability of retention efficiency and flux. Furthermore, when the macropore region is too close to the outlet liquid surface, it increases the risk of excessive colloid infiltration into the membrane fibers. Therefore, through research, this invention ensures that the closest average distance A from the macropore region to the outlet liquid surface and the closest average distance B to the inner inlet liquid surface are both no less than 15 μm. This means the macropore region is not too close to either the inner or outer outlet liquid surfaces. Combined with the overall membrane porosity of 35%-70%, the resulting ultrafiltration membrane exhibits superior overall flux, while maintaining essentially no change in the pressure resistance of the inner and outer liquid surfaces. The overall mechanical strength of the membrane remains high, and excessive colloid infiltration into the membrane fiber lumen prevents blockage and compromising the difficulty of fabricating the membrane module.

[0027] In this invention, the location of the macropore region is determined by using a scanning electron microscope (SEM) to characterize the morphology of the entire membrane cross-section, for example, obtaining an SEM image of the entire membrane at a magnification of 400, 500, or 700. The region L with the largest membrane pores is then identified. Multiple SEM images of the membrane cross-section at magnifications of 10,000, 15,000, or 20,000 are then continuously photographed within region L. The pore diameters of the multiple SEM images of region L at various magnifications are measured by selecting multiple pores on the same plane, measuring their diameters, and calculating the average value. The maximum value obtained is the maximum value of the macropore region of the membrane. The pore size is then determined. Next, the membrane cross-section between the plane with the largest pore size and the outlet liquid surface is continuously photographed to obtain multiple electron microscope images of the membrane cross-section at magnifications of 10000, 15000, or 20000. Then, the average pore size of the corresponding plane region is measured progressively from the plane with the largest pore size towards the outlet liquid surface until the average pore size is 0.75 times the average value of the largest pore size. The plane with this average pore size is defined as interface P1 of the macropore region near the outlet liquid surface. The same method is used to determine interface P2 of the macropore region near the inlet liquid surface. The region between interface P1 and interface P2 is called the macropore region. The average distance between interface P1 and the outlet liquid surface is called the closest average distance A from the macropore region to the outlet liquid surface, and the average distance between interface P2 and the inlet liquid surface is called the closest average distance B from the macropore region to the inlet liquid surface. The SEM average pore size of the macropore region is obtained by characterizing the area between interface P1 and interface P2 using a scanning electron microscope at a certain magnification, such as 2000x, 5000x, or 10000x. Points at different locations (preferably more than 10 points) are uniformly selected as measurement objects. The corresponding SEM pore sizes are measured using appropriate computer software (such as Matlab, NIS-Elements, etc.) or manually, and then the average value is calculated. The nearest average distance A and nearest average distance B are measured on the cross-sectional SEM image of the membrane by measuring the distances from multiple interfaces P1 / P2 to the external liquid surface / internal liquid surface using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then calculating their average values.

[0028] As a further improvement of the present invention, the thickness of the macropore region is 40-120 μm; the ratio of the thickness of the macropore region to the overall thickness of the membrane is 0.25-0.6; and / or, the ratio of the SEM average pore diameter of the macropore region to the SEM average pore diameter of the first pore is 3-20.

[0029] The macropore region is the area with larger pores inside the membrane and is one of the important factors affecting the overall membrane flux. The SEM average pore size of the macropore region of the membrane prepared by this invention is 3-20 times larger than that of the first pore (e.g., 3 times, 5 times, 8 times, 10 times, 12 times, etc.). This can improve the overall membrane flux. At the same time, the fluid velocity is relatively stable when the fluid enters or exits the macropore region, which can avoid damage to the cross-sectional fibers forming the membrane pore structure due to drastic changes in flow velocity. The inventors of this application unexpectedly discovered that when the ratio of the SEM average pore size of the macropore region to the SEM average pore size of the first pore is slightly larger, the thickness of the macropore region can be relatively thick (e.g., the ratio of the thickness of the macropore region to the thickness of the overall membrane is greater than 0.25). This further improves the overall membrane flux by increasing the thickness of the macropore region. We were pleasantly surprised to find that, with the SEM average pore size of the large pore area being slightly larger than that of the first pore, and the synergistic effect of the thicker large pore area, neither the first nor the second pore collapsed or deformed. Both the inlet and outlet liquid surfaces had good pressure resistance and were able to maintain stable retention efficiency and throughput. If the ratio of the SEM average pore size of the macroporous region to the SEM average pore size of the first pore exceeds 20, although it can improve the overall flux of the membrane, it will bring the risk of membrane structural instability. If the thickness of the macroporous region is greater than 120 μm or the thickness of the macroporous region accounts for more than 60% of the overall membrane thickness, that is, when the thickness of the macroporous region is too large or the thickness of the macroporous region accounts for too much of the overall membrane thickness, the first and second pores of the prepared ultrafiltration membrane will collapse and deform, which will affect the membrane's retention efficiency and flux stability. If the ratio of the SEM average pore size of the macroporous region to the SEM average pore size of the first pore is too small, it will not further improve the overall flux of the membrane. If the thickness of the macroporous region is too thin or the ratio of the thickness of the macroporous region to the overall membrane thickness is too low, it will also have limited effect on increasing the overall flux of the ultrafiltration membrane (because the presence of the macroporous region can increase the fluid flow area, thereby increasing the fluid flux of the macroporous region and thus increasing the overall flux of the membrane, especially for internal pressure ultrafiltration membranes, where the fluid flows from the inner liquid inlet to the outer liquid outlet, the presence of the macroporous region can reduce flow resistance). Therefore, under the synergistic effect of the SEM average pore size ratio of the macroporous region being 3-20, when the membrane thickness of the macroporous region is relatively thick or the thickness of the macroporous region accounts for a large proportion of the overall membrane thickness, the obtained ultrafiltration membrane not only has excellent and stable overall membrane flux, but also maintains the pressure resistance of the outer liquid surface and the inner liquid surface of the membrane, as well as the overall mechanical strength of the membrane.

[0030] In this invention, parameters such as the thickness of the large pore area can be obtained by characterizing the morphology of the membrane cross-section structure using a scanning electron microscope, and then by repeatedly measuring the distance between interface P1 and interface P2 using computer software (such as Matlab, NIS-Elements, etc.) or manually, and calculating the average value. Of course, those skilled in the art can also obtain the above parameters through other testing methods. The above testing methods are for reference only (the thickness of the small pore area and other parameters mentioned below can also be obtained using this method).

[0031] As a further improvement of the present invention, the nearest average distance A from the macropore region to the outer liquid surface is 20μm-60μm, and the ratio of this distance A to the film thickness is 0.1-0.5; and / or, the ratio of the nearest average distance A from the macropore region to the outer liquid surface to the nearest average distance B from the macropore region to the inner liquid surface is 0.6-2.5.

[0032] Because the macropore region is the area with larger pores inside the membrane, the distance between the macropore region and the outlet liquid surface cannot be too close. Otherwise, it can easily lead to damage to the first pore, thereby affecting the membrane retention efficiency and flux stability, as well as the pressure resistance of the outlet liquid surface and the overall mechanical strength of the membrane. At the same time, excessive colloids will enter the membrane fibers, clogging the membrane pores and affecting the cleanliness of subsequent products. Therefore, preferably, the closest average distance A from the macropore region to the outlet liquid surface is 20-60 μm, that is, the macropore region is not too close to the outlet liquid surface. The resulting ultrafiltration membrane has excellent overall flux, stable pressure resistance at the outlet liquid surface, excellent overall mechanical strength of the membrane, and controls the appropriate amount of colloids entering the membrane fibers to reduce the difficulty of membrane module preparation while avoiding excessive membrane fouling caused by pore clogging.

[0033] Furthermore, if the ratio of the closest average distance A from the macropore region to the outlet liquid surface to the membrane thickness is too large, i.e., the distance between the macropore region and the outlet liquid surface is too far, although it can ensure that the first pore will not collapse or deform, the colloid will have difficulty entering the membrane fibers and will not be able to achieve the bonding force required when the membrane fibers are made into a module, increasing the difficulty of membrane module preparation. At the same time, if the ratio of the closest average distance A from the macropore region to the outlet liquid surface to the membrane thickness is too low, i.e., the macropore region is too close to the outlet liquid surface, it will cause the first pore to collapse and deform, which will significantly affect the retention efficiency and flux stability. It will also easily lead to excessive colloid entering the membrane fibers and clogging the membrane pores, increasing product contamination. Therefore, by adjusting the ratio of distance A to membrane thickness to 0.1-0.5, the obtained ultrafiltration membrane has better overall membrane flux, membrane outlet liquid surface pressure resistance, and overall membrane mechanical strength, and is also easier to manufacture into membrane modules.

[0034] Furthermore, by adjusting the ratio of the closest average distance A from the macropore region to the outgoing liquid surface to the closest average distance B from the macropore region to the ingoing liquid surface to 0.6-2.5, the macropore region is neither particularly close to the outgoing liquid surface nor particularly close to the ingoing liquid surface. In other words, the macropore region is located in a relatively middle position of the membrane, which can play a certain buffering role. That is, the distance from the ingoing liquid surface to the macropore region interface P2 is similar to the distance from the macropore region interface P1 to the outgoing liquid surface. This can optimize the pressure distribution, reduce the deformation or damage of membrane fibers caused by uneven pressure, and thus improve the overall mechanical strength of the membrane. Therefore, the nearest average distance A from the macropore region to the outer liquid surface is 20μm-60μm, and the ratio of this distance A to the membrane thickness is 0.1-0.5. At the same time, under the synergistic effect of the ratio of the nearest average distance A from the macropore region to the outer liquid surface and the nearest average distance B from the macropore region to the inner liquid surface being 0.6-2.5, the obtained ultrafiltration membrane has the advantages of better overall membrane flux, pressure resistance of the outer liquid surface, overall mechanical strength of the membrane, easy fabrication of the prepared membrane fibers into membrane modules, excellent adhesion between membrane fibers, and optimized fluid distribution.

[0035] As a further improvement of the present invention, the macroporous region has a first cross-sectional fiber forming a porous structure, the SEM average diameter of the first cross-sectional fiber being 20nm-180nm; and / or, the ratio of the SEM average pore diameter of the macroporous region to the SEM average diameter of the first cross-sectional fiber is 5-30.

[0036] The aforementioned macroporous region has a first cross-sectional fiber that forms a porous structure. If the SEM average diameter of the first cross-sectional fiber is too small, it cannot support the pores in the macroporous region. Furthermore, an excessively small SEM average diameter of the first cross-sectional fiber makes it prone to breakage during ultrafiltration, leading to the connection of two or more pores to form larger pores, or even finger-shaped pores. This causes significant velocity changes when the fluid passes through the macroporous region, further damaging other first cross-sectional fibers and reducing the overall mechanical strength of the membrane. Changes in fluid velocity in the macroporous region can also cause the collapse of pores in the outlet liquid surface, affecting its pressure resistance. Conversely, if the SEM average diameter of the first cross-sectional fiber is too large, it reduces the overall porosity of the membrane, affecting filtration efficiency. Therefore, by adjusting the SEM average diameter of the first cross-sectional fiber to 20-180 nm, this first cross-sectional fiber can support the pores in the macroporous region, further improving the pressure resistance of the outlet liquid surface and the overall mechanical strength of the membrane. Furthermore, by studying the ratio of the average SEM pore size of the macroporous region to the average SEM pore size of the first cross-section fiber to 5-30, and through the synergistic effect of the appropriate average SEM diameter of the first cross-section fiber in the macroporous region, the macroporous region has a suitable porosity, which in turn makes the membrane as a whole have better flux. At the same time, even when ultrafiltration is performed under a certain operating pressure, the obtained ultrafiltration membrane still has excellent overall mechanical strength.

[0037] The average diameter of the fibers in the first cross-section can be measured by using a scanning electron microscope to characterize the morphology of the membrane cross-section in the macropore region, followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement, and then performing corresponding calculations. For example, first, the membrane cross-section in the macropore region is characterized using an electron microscope to obtain the corresponding SEM image. The specific area size depends on the actual situation. Then, the diameter of the fibers in the first cross-section on this area is measured using appropriate computer software or manually (preferably more than 10 times, the specific number of times depends on the situation). Then, the average diameter of the fibers on the first cross-section is calculated. 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. (The average diameter of the fibers in the second cross-section can also be tested using a similar method.)

[0038] As a further improvement of the present invention, in the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore size of the main body of the ultrafiltration membrane first increases, then decreases, and then increases again. The main body includes a small pore region located between the large pore region and the outer liquid outlet surface. The closest average distance C from the small pore region to the outer liquid outlet surface is not less than 2 μm. The overall porosity of the ultrafiltration membrane is 40%-65%.

[0039] In the sulfone polymer hollow fiber ultrafiltration membrane main structure provided by the present invention, it can be further clearly seen that in the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore size of the main body first increases, then decreases, and then increases again. This changing membrane pore structure results in a small pore region between the macropore region and the outer liquid outlet surface. The small pore region can be considered as a region with relatively small pore size inside the membrane. The SEM average pore size of the small pore region is less than 0.5 times the SEM average pore size of the macropore region. The existence of the small pore region can play a supporting role for the macropore region, making the macropore region of the ultrafiltration membrane prepared by the present invention less prone to collapse or deformation, thereby ensuring a more stable flux and retention efficiency of the ultrafiltration membrane as a whole, while also ensuring the overall mechanical strength of the ultrafiltration membrane.

[0040] Since the pore area is the region with smaller pores inside the membrane, if the pore area is too close to the outlet liquid surface, contaminants from the outlet liquid surface can easily enter the pore area in a non-clean environment, causing pore blockage. This can then affect the penetration of colloids into the membrane fibers during membrane module assembly, resulting in insufficient adhesion between the membrane fibers and affecting the quality of the hollow fiber module. Therefore, through research, the closest average distance C from the pore area to the outlet liquid surface in this invention is not less than 2μm, meaning the pore area is not too close to the outlet liquid surface. Combined with the overall membrane porosity of 40%-65%, the resulting ultrafiltration membrane has better overall membrane mechanical strength, suitable adhesion when the membrane fibers are prepared into membrane modules, and can still maintain a relatively good overall membrane flux.

[0041] The location of the pore region is determined in this invention by using a scanning electron microscope to characterize the morphology of a cross-section near the liquid outlet, for example, obtaining a scanning electron microscope image of the membrane section at magnifications of 1000, 2000, or 3000. This identifies the region S with the smallest membrane pore size between the macropore region and the liquid outlet. Then, region S is continuously photographed, for example, obtaining multiple membrane cross-sectional images at magnifications of 10000, 15000, or 20000. The pore size of the multiple magnification membrane cross-sectional images obtained for region S is measured by selecting multiple pores on the same plane, measuring their pore size, and calculating the average value. The minimum value obtained is then determined. The minimum pore size of the membrane pore region is defined as follows: Then, the membrane cross-section between the plane with the minimum pore size and the outlet liquid surface is continuously photographed to obtain multiple electron microscope images of the membrane cross-section at magnifications of 10000, 15000, or 20000. Next, the average pore size of the corresponding plane region is measured progressively from the plane with the minimum pore size towards the outlet liquid surface until the average pore size is 1.2 times the average minimum pore size of the membrane pore region. The plane with this average pore size is defined as interface P3 of the membrane pore region near the outlet liquid surface. The same method is used to determine interface P4 of the membrane pore region near the macropore region. The area between interface P3 and interface P4 is called the pore region. The average distance between interface P3 and the outlet liquid surface is called the closest average distance C from the pore region to the outlet liquid surface. The average SEM pore size of the pore region is obtained by characterizing the area between interface P3 and interface P4 using a scanning electron microscope at a certain magnification, such as 2000x, 5000x, or 10000x. Points at different locations (preferably more than 10 points) are uniformly selected as measurement objects. The corresponding SEM pore sizes are measured using appropriate computer software (such as Matlab, NIS-Elements, etc.) or manually, and then the average value is calculated. The nearest average distance C is measured by measuring the distance from interface P3 to the outer liquid surface of multiple pore regions on the cross-sectional SEM image of the membrane using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then calculating the average value.

[0042] As a further improvement of the present invention, the thickness of the pore region is 5μm-30μm; the ratio of the thickness of the pore region to the overall thickness of the membrane is 0.05-0.15; and / or, the ratio of the thickness of the pore region to the thickness of the macropore region is 0.1-0.4.

[0043] As is generally believed, the pore region is the area inside the membrane with smaller pores. The presence of the pore region will lead to a decrease in the overall membrane flux. If the thickness of the pore region is too large, the overall membrane flux will drop sharply. If the thickness of the pore region is too small, it cannot guarantee the support of the macropore region. Therefore, by adjusting the thickness of the pore region to 5μm-30μm, the ultrafiltration membrane obtained within this thickness range can not only guarantee the support of the macropore region, preventing the pores in the macropore region from collapsing and deforming, thus ensuring better mechanical strength, stable overall flux and retention efficiency of the membrane, but also ensure that the overall membrane flux does not drop sharply due to the presence of the pore region.

[0044] Furthermore, by controlling the ratio of the thickness of the pore region to the overall membrane thickness within the range of 0.05-0.15, the overall mechanical strength of the ultrafiltration membrane can be improved, the overall stable flux and retention efficiency stability of the membrane can be maintained, and the obtained ultrafiltration membrane can be further guaranteed to have a suitable overall membrane flux.

[0045] Furthermore, by controlling the ratio of the thickness of the micropore region to the thickness of the macropore region within the range of 0.1-0.4, it can be ensured that the micropore region of the obtained ultrafiltration membrane plays a supporting role for the macropore region, while the overall flux of the ultrafiltration membrane is not substantially affected. Therefore, under the synergistic effect of the micropore region thickness within a reasonable range, the ratio of the micropore region thickness to the overall membrane thickness within a reasonable range, and the thickness of the micropore region to the macropore region within a reasonable range, the prepared ultrafiltration membrane has a stable membrane structure and excellent mechanical strength, thereby ensuring better stable flux and retention efficiency, while the obtained ultrafiltration membrane still has a suitable overall membrane flux.

[0046] As a further improvement of the present invention, the SEM average pore size of the small pore region is 0.1-0.4 times the SEM average pore size of the large pore region, and / or, the small pore region has a second cross-sectional fiber forming a porous structure, and the SEM average diameter of the second cross-sectional fiber is 10nm-150nm.

[0047] This invention adjusts the SEM average pore size of the small-pore region to 0.1-0.4 times that of the large-pore region. This means the average pore size of the small-pore region is relatively smaller than that of the large-pore region, providing better support for the large-pore region. Simultaneously, at this SEM average pore size ratio, the colloid can enter the membrane fibers in an appropriate amount, ensuring the adhesion between the membrane fibers when preparing the hollow fiber membrane module without causing excessive pore blockage and internal membrane contamination. When the ratio of the average SEM pore size of the small-pore region to that of the large-pore region is within a reasonable range, the fluid flow from the large-pore region to the small-pore region is relatively stable, preventing damage to the cross-sectional fibers in the small-pore region and resulting in a membrane with superior mechanical strength. Furthermore, through the synergistic effect of the SEM average diameter of the second cross-section fiber being 10nm-150nm, when the SEM average diameter of the second cross-section fiber is within a suitable ratio range, the mechanical strength of the small pore region can be well guaranteed, thereby better supporting the large pore region. This results in the ultrafiltration membrane having excellent mechanical strength, stable flux and retention efficiency, while also facilitating the preparation of high-quality hollow fiber membrane modules.

[0048] As a further improvement of the present invention, the nearest average distance C from the small orifice area to the liquid surface is 4μm-20μm; the ratio of this distance C to the film thickness is 0.04-0.1; and / or, the ratio of the nearest average distance C from the small orifice area to the liquid surface to the nearest average distance A from the large orifice area to the liquid surface is 1:2-15.

[0049] By adjusting the closest average distance C from the pore area to the outlet liquid surface to 4μm-20μm, the pore area is relatively close to the outlet liquid surface, but not too close. If the pore area is too close to the outlet liquid surface, small particulate pollutants in the air in the non-clean environment can easily enter the pore area and clog the membrane pores, affecting the penetration of colloids and increasing the difficulty of membrane module preparation. If the pore area is too far from the outlet liquid surface, the effect of further improving the pressure resistance of the outlet liquid surface is weakened. Therefore, setting the closest average distance C from the pore area to the outlet liquid surface within a reasonable range can make the obtained ultrafiltration membrane have better pressure resistance of the outlet liquid surface, further improving the overall mechanical strength of the membrane, and at the same time, it can prepare high-quality hollow fiber membrane modules.

[0050] Furthermore, by adjusting the ratio of the nearest average distance C from the orifice region to the liquid surface to the membrane thickness to 0.04-0.1, not only can the membrane fibers have excellent adhesion when the membrane is prepared into a membrane module, but the overall mechanical strength of the membrane can also be improved.

[0051] Furthermore, by controlling the ratio of the closest average distance C from the small orifice area to the outer liquid surface to the closest average distance A from the large orifice area to the outer liquid surface within a synergistic effect of 1:2-15, the overall mechanical strength of the membrane, the pressure resistance of the outer liquid surface, and the ease of fabrication into hollow fiber membrane modules can be improved, while still maintaining good overall membrane flux.

[0052] Furthermore, under the overall synergistic effect of the small-pore region and the large-pore region, the overall flow rate of the membrane is relatively stable, which is conducive to protecting the integrity of the internal cross-sectional fibers of the membrane. This protects the internal pores of the membrane from collapse or deformation, resulting in a membrane with stable flux and retention efficiency. At the same time, the overall synergistic effect of the small-pore region and the large-pore region can further improve the overall mechanical strength of the membrane, the pressure resistance of the inlet and outlet liquid surfaces, and the overall flux of the membrane. It is also easier to prepare membrane modules.

[0053] As a further improvement of the present invention, the initial water flux of the ultrafiltration membrane is 0.5 LMH / psi-300 LMH / psi, preferably 1 LMH / psi-250 LMH / psi; the water flux of the ultrafiltration membrane after 10 complete uses is more than 70% of the initial water flux; the tensile strength of the ultrafiltration membrane is 100 cN-350 cN, preferably 160 cN-280 cN, and the elongation at break is not less than 15%, preferably 20%-150%; the membrane thickness is 90 μm-200 μm.

[0054] Permeation flux, also known as permeation rate or simply flux, refers to the amount of substance that passes through a unit membrane area per unit time under a certain operating pressure during membrane separation. The magnitude of the flux reflects the filtration speed; a higher flux indicates a faster filtration rate. In this invention, the sulfone polymer hollow fiber ultrafiltration membrane has a water flux of 0.5 LMH / psi to 300 LMH / psi, which meets the requirements of practical applications. This indicates that the ultrafiltration membrane has a relatively fast filtration speed, ensuring retention efficiency while allowing fluid to pass through the ultrafiltration membrane quickly, resulting in relatively low time costs and high economic benefits. Meanwhile, after 10 complete uses (one complete use refers to the material to be filtered being separated and purified once by the hollow fiber membrane module, and then the hollow fiber membrane module is cleaned and regenerated using a cleaning solution; the water flux after one complete use is measured; correspondingly, 10 separations, purifications, and cleanings constitute 10 complete uses), the water flux of the ultrafiltration membrane is more than 70% of the initial water flux. This shows that the ultrafiltration membrane prepared by this invention has good antifouling performance and regeneration effect, and has a long service life.

[0055] After mechanical strength testing, the tensile strength of the ultrafiltration membrane prepared by this invention is 100cN-350cN, preferably 160cN-280cN, and the elongation at break is not less than 15%, preferably 20%-150%. It has excellent mechanical properties and high industrial practical value. This also shows that the pressure resistance of the ultrafiltration membrane at both the inner liquid inlet and outer liquid outlet is high, and it can withstand the operating pressure and changes in operating pressure during the ultrafiltration process for a long time. It can also work normally for a long time under relatively high pressure.

[0056] Each sample was stretched at a constant speed (50 mm / min, 30 mm between upper and lower clamps) using a tensile testing machine at room temperature until it broke. The tensile strength and elongation at break were measured. The process was repeated three times, and the average value was taken. The average value is the final tensile strength and elongation at break value.

[0057] As a further improvement of the present invention, the ultrafiltration membrane is sponge-like. Compared with the finger-like structure, the sponge-like hollow fiber ultrafiltration membrane has better pressure resistance, overall membrane mechanical strength, and tensile strength (the finger-like hollow fiber membrane has disadvantages such as easy breakage of internal fibers leading to the collapse of the entire membrane filament, poor pore size control which may affect the filtration progress, and high requirements for the diameter of the supporting pore structure fibers).

[0058] A second aspect of the present invention provides a method for preparing a sulfone polymer hollow fiber ultrafiltration membrane as described above, comprising the following steps:

[0059] Step 1: Preparation of casting solution and core solution:

[0060] The casting solution comprises a sulfone polymer, a first organic solvent, a hydrophilic additive, and a non-solvent; the solid content of the sulfone polymer in the casting solution is 15%-25%, and the viscosity of the casting solution is 10,000-100,000 cps;

[0061] The core fluid comprises a second organic solvent and water, wherein the mass content of the second organic solvent in the core fluid is 0-40%;

[0062] Step 2: Spinning: The casting solution and core solution obtained in Step 1 are extruded together from the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface. The temperature of the casting solution is 20-40℃.

[0063] Step 3: Rapid Preliminary Phase Separation: The molded product obtained in Step 2 is immersed in the first coagulation bath for rapid phase separation treatment. The phase separation time is 0.1-1.2s. The temperature of the first coagulation bath is 5-50℃ higher than that of the casting solution to form a film. The first coagulation bath contains water and a third organic solvent, and the mass content of the third organic solvent is greater than 50%.

[0064] Step 4: Complete phase separation: Immerse the green film obtained in Step 3 into the second coagulation bath for complete phase separation treatment, wherein the phase separation time is 30-80s, and the temperature of the second coagulation bath is not lower than the temperature of the casting solution; wherein the second coagulation bath contains water and a fourth organic solvent, and the mass content of the fourth organic solvent is not greater than 30%.

[0065] Step 5: Cleaning and drying: The raw membrane obtained in step 4 is cleaned with pure water and then dried to obtain a sulfone polymer hollow fiber ultrafiltration membrane.

[0066] As a further improvement of the present invention, the sulfone polymer is at least one of bisphenol A polysulfone, polyethersulfone, polyphenylene sulfone, and sulfonated polyethersulfone; the first organic solvent, the second organic solvent, the third organic solvent, and the fourth organic solvent are all at least one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; the hydrophilic additive is at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol; and the non-solvent is at least one of water, isopropanol, glycerol, and butanediol.

[0067] As a further improvement of the present invention, the temperature of the first coagulation bath is 5-15°C higher than that of the casting solution, and / or the temperature of the second coagulation bath is 30-50°C higher than that of the casting solution.

[0068] As a further improvement of the present invention, the mass content of the non-solvent in the casting solution is 1%-10%; and / or, the mass content of the third organic solvent in the first coagulation bath is 55%-95%; and / or, the mass content of the fourth organic solvent in the second coagulation bath is 0-25%.

[0069] As a further improvement of the present invention, the temperature of the first coagulation bath is 30-50°C higher than the temperature of the casting solution; and / or, the temperature of the second coagulation bath is 10-45°C lower than the temperature of the first coagulation bath; and / or, during the complete phase separation in step four, the film is stretched with a stretching rate of 1%-5%.

[0070] In preparing the sulfone polymer hollow fiber ultrafiltration membrane of the present invention, a casting solution is first prepared. The casting solution includes a sulfone polymer as a membrane-forming substance, a first organic solvent for dissolving the sulfone polymer, a hydrophilic additive, and a non-solvent. The hydrophilic additive is at least one of polyethylene glycol, polyvinylpyrrolidone, and polyvinyl alcohol. The addition of the hydrophilic additive and the non-solvent can effectively control the viscosity of the casting solution system and effectively improve the stability of membrane flux. By adjusting the ratio of the sulfone polymer, the first organic solvent, the hydrophilic additive, and the non-solvent, the casting solution has a suitable viscosity. The viscosity of the casting solution has a significant impact on the final filter membrane structure and performance, such as affecting the pore size, thickness, and flow rate of the filter membrane. This ensures that the final sulfone polymer hollow fiber ultrafiltration membrane has a suitable thickness, an ideal membrane pore structure, and a suitable pore size, and can be effectively used in biofiltration. The hollow fiber ultrafiltration membrane of the present invention uses a liquid composed of a second organic solvent and water as the inner core during extrusion. By reasonably controlling the mass content of the second organic solvent in the core liquid, it is possible to ensure that the pressure inside the hollow fiber ultrafiltration membrane cavity is balanced with the external pressure, thereby stabilizing the cavity of the hollow fiber ultrafiltration membrane and making the overall wall thickness of the membrane basically the same. Furthermore, under the combined action of other conditions such as the coagulation bath, by controlling the changes in the membrane phase separation process, a sulfone polymer hollow fiber ultrafiltration membrane with ideal molecular weight cutoff and ideal pore size distribution can be manufactured.

[0071] The second step is to extrude the prepared casting solution and core solution together from the spinneret. The casting solution forms a molded product with an inner liquid inlet surface and an outer liquid outlet surface in the nozzle, namely a hollow fiber membrane. The extruded hollow fiber membrane has an inner liquid inlet surface facing the inner cavity and an outer liquid outlet surface opposite to the cavity.

[0072] In step three, rapid preliminary phase separation involves directly immersing the molded product obtained in step two into the first coagulation bath for rapid phase separation. The phase separation time is 0.1-1.2 s. Within such a short time, the phase separation of the membrane can only occur at and near the membrane's outer liquid surface. Furthermore, under the combined synergistic effect of the sulfone polymer solid content being 15%-25%, the first coagulation bath temperature being 5-50°C higher than the casting solution temperature, and the third organic solvent content in the first coagulation bath being greater than 50%, the phase separation rate in the first coagulation bath is relatively slow. Therefore, under the synergistic effect of the relatively slow phase separation rate and the extremely short phase separation time in the first coagulation bath, a structure with fewer pores and relatively larger pore sizes on the outer liquid surface is prepared. Meanwhile, because the inner liquid inlet surface is in direct contact with the core liquid, the mass content of the second organic solvent in the core liquid is lower than that of the third organic solvent in the first coagulation bath. Under the combined effect of the specific solid content and viscosity system of the casting liquid, the obtained ultrafiltration membrane has a suitable pore density of the inner liquid inlet surface and the SEM average pore size of the second pore. This ensures that the ratio of the SEM average pore size of the second pore on the inner liquid inlet surface to the SEM average pore size of the first pore on the outer liquid surface, and the ratio of the pore density of the inner liquid inlet surface to the outer liquid inlet surface, are both within the ideal range.

[0073] Meanwhile, the biofilm after rapid initial phase separation is immersed in the second coagulation bath for slow phase separation, with a phase separation time of 30-80 seconds. The temperature of the second coagulation bath is not lower than the temperature of the casting solution. The mass content of the fourth organic solvent is lower than that of the third organic solvent in the first coagulation bath. As a result, the phase separation rate is slower than that of the rapid initial phase separation process. In addition, the structure with fewer pores formed on the liquid surface during the rapid initial phase separation step further slows down the phase separation rate, thereby forming the macroporous region of the sulfone polymer hollow fiber ultrafiltration membrane of the present invention.

[0074] Preferably, in our study, we also found that when the temperature of the second coagulation bath is 10-45°C lower than that of the first coagulation bath, and due to factors such as the content of the fourth organic solvent in the second coagulation bath being much lower than that of the third organic solvent in the first coagulation bath, and the temperature difference between the second and first coagulation baths and the casting liquid, the phase separation rate of the membrane changes during the phase separation process, forming a small pore area in the macropore area and the outer liquid surface.

[0075] After phase separation, the resulting green membrane is washed and dried in water to obtain a sulfone polymer hollow fiber ultrafiltration membrane. Preferably, the completely phase-separated green membrane can be subjected to a stretching treatment, which refers to a slight stretching of 1%-5% on the green membrane. After stretching, the mechanical strength of the green membrane is improved, resulting in better pressure resistance of the ultrafiltration membrane. At the same time, the stretching ratio is small, so it has little or no effect on the pore size of the membrane, ensuring that the final membrane still has a suitable pore size and excellent retention efficiency.

[0076] A third aspect of the present invention provides a sulfone polymer hollow fiber ultrafiltration membrane module comprising the above-mentioned sulfone polymer hollow fiber ultrafiltration membrane and a cylindrical shell; the ultrafiltration membrane is located inside the cylindrical shell, and the ultrafiltration membranes are bonded together by a colloid; the inner diameter of the ultrafiltration membrane is 0.4-2.0 mm.

[0077] The main process of preparing hollow fiber membrane into hollow fiber membrane module includes: (1) arranging multiple hollow fiber membrane filaments in parallel to form a membrane filament bundle with flush ends; (2) sealing the membrane filament pores with a plugging agent; (3) loading the membrane filament bundle with the sealed membrane filament pores into the shell; (4) injecting potting compound into both ends of the membrane filament bundle to form sealed ends; (5) after potting, curing at room temperature for a certain period of time to ensure that the potting compound is completely cured; (6) after curing, cutting off the parts of the membrane filament bundle with plugging agent at both ends to make the membrane filament pores open and form the final hollow fiber module. As can be seen from the above preparation process, the sealing process has a significant impact on the quality of the prepared hollow fiber membrane module. Through continuous research, we have found that when using sulfone polymers as the material for hollow fiber ultrafiltration membranes, their surface energy is not less than 60 mN / m, while the surface energy of colloids is usually below 50 mN / m. Because the surface energy of colloids is lower than that of sulfone polymers, it is beneficial for the adhesion between the hollow fiber membrane fibers made of sulfone polymers, and it also facilitates the relatively easy entry of colloids into the membrane fiber interior. Simultaneously, by controlling the pore density at the outlet liquid surface to 20 pores / 25 μm... 2 -200 pieces / 25μm 2 When hollow fiber ultrafiltration membranes with an average SEM pore size of 50nm-1000nm in the first pore are used to form modules, colloids can partially penetrate into the membrane fibers, but will not excessively enter the membrane fibers and block the pores or even the membrane cavity. If the colloids severely block the membrane pores or the membrane cavity, it will cause blockage of the inlet. The portion of the membrane fibers blocked by the colloids in the pores or membrane cavity must be cut off and the membrane fibers resealed, resulting in waste of membrane fibers. That is, under the synergistic effect of the average SEM pore size of the first pore and the pore density of the outflow liquid surface, the adhesion between the membrane fibers is ensured, while improving the quality and success rate of hollow fiber membrane module preparation, reducing unnecessary waste, and also reducing membrane fouling, making it suitable for the filtration of biomacromolecules.

[0078] A fourth aspect of the invention provides an application of a sulfone polymer hollow fiber ultrafiltration membrane, said ultrafiltration membrane being used in a tangential flow manner for: (a) purification, concentration, and dialysis of vaccines or viral vectors; (b) concentration and dialysis of proteins; (c) clarification filtration of cells and bacteria in fermentation broth; (d) recovery and dialysis of cells and bacterial cells; (e) nucleic acid concentration; (f) preparation of pyrogen-free buffer solutions; (g) small molecule antibiotic extraction and purification to remove macromolecular impurities; (h) pyrogen removal from small molecule active substances / small molecule antibiotics; and (i) antibody concentration.

[0079] Compared with the prior art, the present invention has the following beneficial technical effects:

[0080] 1. This invention scientifically controls the range of SEM average pore size of the outer liquid surface, the ratio of the SEM average pore size of the inner liquid surface to the SEM average pore size of the outer liquid surface, and the overall pore size and porosity of the ultrafiltration membrane in a sulfone polymer hollow fiber ultrafiltration membrane. The resulting ultrafiltration membrane maintains its flux even when the outer liquid surface porosity is low, overcoming the technical bias of low membrane flux when the outer liquid surface porosity is low. At the same time, it achieves excellent pressure resistance of the outer liquid surface, excellent overall mechanical strength of the membrane, and reduces the risk of fouling of the outer liquid surface, making it more suitable for the needs of biological ultrafiltration.

[0081] 2. This invention scientifically controls the range of SEM average pore size and pore density of the sulfone polymer hollow fiber ultrafiltration membrane at the liquid surface, so that when the membrane fibers are used to prepare hollow fiber membrane modules, the membrane fibers have excellent adhesion between them, while reducing the contamination of the membrane fibers by colloids, improving the quality and success rate of hollow fiber module preparation, and meeting the requirements of bio-ultrafiltration under harsh conditions.

[0082] 3. The sulfone polymer hollow fiber ultrafiltration membrane of the present invention is integrally formed by casting liquid, which has the advantages of simple preparation method, better cost, green and environmentally friendly, and suitable for industrial production. Attached Figure Description

[0083] Figure 1 This is a scanning electron microscope (SEM) schematic diagram of the liquid surface outside the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, with a magnification of 5000×.

[0084] Figure 2 This is a scanning electron microscope (SEM) schematic diagram of the liquid surface outside the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, with a magnification of 10000×.

[0085] Figure 3 This is a scanning electron microscope (SEM) schematic diagram of the liquid inlet surface inside the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, with a magnification of 20000×.

[0086] Figure 4 This is a scanning electron microscope (SEM) schematic diagram of the liquid inlet surface of the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, with a magnification of 50000×.

[0087] Figure 5 This is a scanning electron microscope (SEM) schematic diagram of the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, with a magnification of 500×.

[0088] Figure 6This is a scanning electron microscope (SEM) schematic diagram of the sulfone polymer hollow fiber ultrafiltration membrane prepared in Example 3, near the liquid surface, with a magnification of 2000×.

[0089] Figure 7 A schematic diagram of the testing apparatus for measuring interception efficiency and water flux. Detailed Implementation

[0090] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0091] Example 1

[0092] A method for preparing a sulfone polymer hollow fiber ultrafiltration membrane includes the following steps:

[0093] Step 1: Preparation of casting solution and core solution

[0094] The casting solution comprises the following components by weight: 25 parts bisphenol A polysulfone, 60 parts dimethyl sulfoxide, 15 parts polyethylene glycol, and 3 parts water. Its temperature is 25°C, its solid content is 24.30%, and its viscosity is 95,000 cps.

[0095] The core fluid comprises dimethyl sulfoxide and water, wherein the mass content of dimethyl sulfoxide in the core fluid is 5%;

[0096] Step 2: The casting solution and core solution are extruded together at the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface;

[0097] Step 3: First, perform preliminary phase separation on the molded product by immersing it in a first coagulation bath at 50°C for 0.2 seconds.

[0098] A biofilm is formed; wherein the first coagulation bath comprises dimethyl sulfoxide and water, and the mass content of dimethyl sulfoxide in the first coagulation bath is 60%;

[0099] Step 4: Immerse the obtained green film in a second coagulation bath at 30°C for 35 seconds to separate the phases, and then stretch it by 2%. The second coagulation bath includes dimethyl sulfoxide and water, and the mass content of dimethyl sulfoxide in the second coagulation bath is 5%.

[0100] Step 5: Wash the membrane obtained in Step 4 with pure water and then dry it to obtain a 5kD bisphenol A polysulfone hollow fiber ultrafiltration membrane, which has a membrane pore structure that first increases, then decreases and then increases again in the direction from the inner liquid inlet surface to the outer liquid outlet surface, that is, it has the structure of macropore region and micropore region described in this invention.

[0101] Example 2

[0102] A method for preparing a sulfone polymer hollow fiber ultrafiltration membrane includes the following steps:

[0103] Step 1: Preparation of casting solution and core solution

[0104] The casting solution comprises the following components by weight: 25 parts polyethersulfone, 55 parts dimethylacetamide, 20 parts polyethylene glycol, and 8 parts water. Its temperature is 40°C, its solid content is 23.10%, and its viscosity is 93,000 cps.

[0105] The core fluid comprises dimethylacetamide and water, wherein the mass content of dimethylacetamide in the core fluid is 8%;

[0106] Step 2: The casting solution and core solution are extruded together at the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface;

[0107] Step 3: First, perform preliminary phase separation on the molded product by immersing it in a first coagulation bath at 75°C for 0.4 seconds.

[0108] A biofilm is formed; wherein the first coagulation bath comprises dimethylacetamide and water, and the mass content of dimethylacetamide in the first coagulation bath is 75%;

[0109] Step 4: Immerse the obtained green film in a second coagulation bath at 50°C for 50 seconds to separate the phases, and then stretch it by 3%. The second coagulation bath includes dimethylacetamide and water, and the mass content of dimethylacetamide in the second coagulation bath is 10%.

[0110] Step 5: Wash the membrane obtained in Step 4 with pure water and then dry it to obtain a 10kD polyethersulfone hollow fiber ultrafiltration membrane, which has a membrane pore structure that first increases, then decreases and then increases again in the direction from the inner liquid inlet surface to the outer liquid outlet surface, that is, it has the structure of macropore region and micropore region described in this invention.

[0111] Example 3

[0112] A method for preparing a sulfone polymer hollow fiber ultrafiltration membrane includes the following steps:

[0113] Step 1: Preparation of casting solution and core solution

[0114] The casting solution comprises the following components by weight: 20 parts polyethersulfone, 50 parts dimethylformamide, 18 parts polyvinylpyrrolidone, and 5 parts water. Its temperature is 20°C, its solid content is 21.50%, and its viscosity is 82,000 cps.

[0115] The core fluid comprises dimethylformamide and water, wherein the mass content of dimethylformamide in the core fluid is 15%;

[0116] Step 2: The casting solution and core solution are extruded together at the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface;

[0117] Step 3: First, perform preliminary phase separation on the molded product by immersing it in a first coagulation bath at 60°C for 0.8 seconds.

[0118] A biofilm is formed; wherein the first coagulation bath comprises dimethylformamide and water, and the mass content of dimethylformamide in the first coagulation bath is 80%;

[0119] Step 4: Immerse the obtained green film in a second coagulation bath at 30°C for 55 seconds to separate the phases, and then stretch it by 3%. The second coagulation bath includes dimethylformamide and water, and the mass content of dimethylformamide in the second coagulation bath is 15%.

[0120] Step 5: Wash the membrane obtained in Step 4 with pure water and then dry it to obtain a 50kD polyethersulfone hollow fiber ultrafiltration membrane, which has a membrane pore structure that first increases, then decreases and then increases again in the direction from the inner liquid inlet surface to the outer liquid outlet surface, that is, it has the structure of macropore region and micropore region described in this invention.

[0121] Example 4

[0122] A method for preparing a sulfone polymer hollow fiber ultrafiltration membrane includes the following steps:

[0123] Step 1: Preparation of casting solution and core solution

[0124] The casting solution comprises the following components by weight: 18 parts polyethersulfone, 50 parts N-methylpyrrolidone, 22 parts polyvinyl alcohol, and 4 parts water. Its temperature is 25°C, its solid content is 19.15%, and its viscosity is 46,000 cps.

[0125] The core fluid comprises N-methylpyrrolidone and water, wherein the mass content of N-methylpyrrolidone in the core fluid is 20%;

[0126] Step 2: The casting solution and core solution are extruded together at the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface;

[0127] Step 3: First, perform preliminary phase separation on the molded product by immersing it in a first coagulation bath at 55°C for 1.0 seconds.

[0128] A biofilm is formed; wherein the first coagulation bath comprises N-methylpyrrolidone and water, and the mass content of N-methylpyrrolidone in the first coagulation bath is 90%;

[0129] Step 4: Immerse the obtained green film in a second coagulation bath at 35°C for 65 seconds to separate the phases and perform 5% stretching. The second coagulation bath includes N-methylpyrrolidone and water, and the mass content of N-methylpyrrolidone in the second coagulation bath is 20%.

[0130] Step 5: Wash the membrane obtained in Step 4 with pure water and then dry it to obtain a 100kD polyethersulfone hollow fiber ultrafiltration membrane, which has a membrane pore structure that first increases, then decreases and then increases again in the direction from the inner liquid inlet surface to the outer liquid outlet surface, that is, it has the structure of macropore region and micropore region described in this invention.

[0131] The structure, overall porosity, overall tensile strength, overall elongation at break, surface energy of the liquid surface outside the membrane, and roughness of the liquid surface outside the membrane were characterized for the ultrafiltration membranes prepared in Examples 1-4. The specific results are shown below:

[0132] Table 1 - Overall characteristics of ultrafiltration membranes

[0133] Overall membrane thickness / μm 110 140 130 150 Overall membrane porosity / % 46.34 53.48 62.90 58.72 Overall tensile strength of the membrane / cN 162 186 170 219 Overall elongation at break of the membrane / % 36 72 57 100

[0134] Table 2 - Characteristics of External Liquid Level and Internal Liquid Level

[0135]

[0136]

[0137] Table 3 - Characteristics of Macroporous Zones

[0138]

[0139]

[0140] Table 4 - Characteristics of the small hole region

[0141]

[0142] Characterization of retention efficiency

[0143] The retention efficiency test method is as follows:

[0144] Step 1: According to Figure 7 The hollow fiber membrane module, pressure gauge, peristaltic pump, feed container (containing the retained substance), valve and receiving bottle are connected in sequence to form a circulation system;

[0145] Step 2: Turn on the peristaltic pump and set it to 6000 seconds. -1 Adjust the pump speed according to the shear rate to fill the pipeline with liquid and remove air from the pipeline;

[0146] Step 3: Adjust the reflux valve to bring the pressure gauge reading between 8-16 psi. When the trapped substance is about to drip out, start the stopwatch. After 10 minutes, take a sample and measure its absorbance on a UV spectrophotometer, recording it as A. 透过 The absorbance of the original solution containing the retained substance is denoted as A. 原液 Its retention efficiency = 1 - A 透过 / A 原液， The detailed results are shown in Table 5 below:

[0147] Table 5 - Retention efficiency of ultrafiltration membranes

[0148]

[0149] The results above show that the sulfone polymer hollow fiber ultrafiltration membranes prepared in Examples 1-4 have excellent retention efficiency.

[0150] Characterization of water flux

[0151] The method for testing water flux is as follows:

[0152] Step 1: According to Figure 7 The hollow fiber membrane module, pressure gauge, peristaltic pump, feed container (containing purified water), valve and receiving bottle are connected in sequence to form a circulation system;

[0153] Step 2: Adjust the transmembrane pressure to 5 psi. After the permeate flow rate stabilizes for 3 minutes, collect the permeate in a beaker and start the stopwatch at the same time. Stop collecting the permeate after 1 minute, weigh and record the data. Repeat 3 times to calculate the average value. At the same time, measure the water temperature and convert it to the value of LMH / psi at 25℃ according to the viscosity coefficient. This value is the water flux of the membrane fiber. The results are shown in Table 6.

[0154] Table 6 - Water Flux of Ultrafiltration Membranes

[0155]

[0156] The results above show that the sulfone polymer hollow fiber ultrafiltration membranes prepared in Examples 1-4 all have excellent initial water flux, and the water flux after 10 complete uses is more than 80% of the initial water flux, indicating good membrane stability and durability.

[0157] Example 5

[0158] A 50 kDa polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method in Example 3. The difference was that the phase separation time in the first coagulation bath in step three was 1.1 s, and the mass content of dimethylformamide in the first coagulation bath was 70%; and there was no stretching operation in step four. The final polyethersulfone hollow fiber ultrafiltration membrane still had a structure with macroporous and microporous regions, and its pore density at the liquid outlet was 178 pores / 25 μm. 2 The pore density of the inner liquid inlet surface is 161 pores / 25μm. 2The ratio of the pore density of the inlet liquid surface to the pore density of the outlet liquid surface in Example 5 is 0.90. Compared with Example 3, the pressure resistance of the outlet liquid surface in Example 5 is relatively low, and its tensile strength is 153cN. In addition, the amount of colloid entering the membrane fiber during the assembly of the membrane fiber into the module is relatively large, resulting in a slightly lower overall membrane flux. Its initial water flux is 34.62LMH / psi. At the same time, when the hollow fiber membrane module is prepared, the amount of colloid entering the membrane fiber is slightly larger, but it does not completely block the inside of the membrane fiber.

[0159] Example 6

[0160] A 50 kD polyphenylsulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method of Example 3. The difference was that the composition of the casting solution in step one included the following components by mass: 22 parts polyphenylsulfone, 50 parts dimethylformamide, 30 parts polyvinylpyrrolidone, and 5 parts water. The temperature was 20°C, the solid content was 20.56%, and the viscosity was 79,000 cps. In step four, there was no stretching operation. The final polyphenylsulfone hollow fiber ultrafiltration membrane still had a structure with macropore and micropore regions. Its surface energy at the liquid surface was 95 mN / m. Compared with Example 3, the membrane fibers in Example 6 were more likely to have colloids enter the interior of the membrane fibers during the assembly process, resulting in a slightly lower overall membrane flux. Its initial water flux was 33.71 LMH / psi. At the same time, when preparing the hollow fiber membrane module, the amount of colloids entering the interior of the membrane fibers was slightly more, but it did not completely block the interior of the membrane fibers.

[0161] Example 7

[0162] A 50 kDa polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method in Example 3. The difference was that the phase separation time in the first coagulation bath in step three was 0.5 s, the mass content of dimethylformamide in the first coagulation bath was 85%, and there was no stretching operation in step four. The final polyethersulfone hollow fiber ultrafiltration membrane still had a structure with macroporous and microporous regions, and its pore density at the liquid outlet was 22 pores / 25 μm. 2 Compared to Example 3, the membrane prepared in Example 7 has a relatively smaller number of outflow pores and a slightly lower overall membrane flux, with an initial water flux of 32.85 LMH / psi. In addition, when it is prepared as a hollow fiber membrane module, the adhesion between the membrane fibers is slightly lower.

[0163] Example 8

[0164] A 50 kD polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method of Example 3. The difference is that the temperature of the first coagulation bath in step three is 35°C, and the temperature of the second coagulation bath in step four is 65°C. The mass content of dimethylformamide in the second coagulation bath is 35%, and there is no stretching. The resulting polyethersulfone hollow fiber ultrafiltration membrane only has a macroporous structure. The distance A from the macroporous region to the liquid surface is 34 μm, and the thickness of the macroporous region is 63 μm. Compared with Example 3, the overall structure of the membrane in Example 8 does not contain a microporous region, and its mechanical strength is slightly worse. Its tensile strength is 153 cN.

[0165] Example 9

[0166] A 50 kD polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method of Example 3. The difference is that the mass content of dimethylformamide in the first coagulation bath in step three is 85%, the temperature is 25°C, and the temperature of the second coagulation bath in step four is 55°C and there is no stretching. The resulting polyethersulfone hollow fiber ultrafiltration membrane only has a macroporous structure. The distance A from the macroporous region to the liquid surface is 17 μm, and the thickness of the macroporous region is 80 μm. Compared with Example 3, the membrane prepared in Example 9 has a thicker macroporous region, and the distance A from the macroporous region to the liquid surface is relatively closer. The pressure resistance of the membrane at the liquid surface is relatively lower, resulting in a slightly lower overall mechanical strength of the membrane. Its tensile strength is 135 cN.

[0167] Example 10

[0168] A 50 kD polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method of Example 3. The difference was that the temperature of the first coagulation bath in step three was 35°C, and the temperature of the second coagulation bath in step four was 35°C. The organic solvent in the second coagulation bath was a mixed solvent of dimethylformamide (50% by mass) and dimethylacetamide (50% by mass), with a mass content of 5% organic solvent. There was no stretching, and the final polyethersulfone hollow fiber ultrafiltration membrane had a structure without macroporous or microporous regions. Compared with Example 3, the membrane structure of Example 10 did not contain macroporous or microporous regions. The overall flux and overall mechanical strength of the membrane were relatively low. Its initial water flux was 28.32 LMH / psi, and its tensile strength was 121 cN.

[0169] Example 11

[0170] Three sulfone polymer hollow fiber ultrafiltration membranes prepared in Examples 1-10 were used to prepare hollow fiber membrane modules. The membrane fibers were bonded together with epoxy resin and then installed in a cylindrical shell. The hollow fiber membrane modules obtained by using the sulfone polymer hollow fiber ultrafiltration membranes prepared in Examples 1-4 have better adhesion and water flux between the membrane fibers.

[0171] Comparative Example 1

[0172] A 50 kDa polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method in Example 3. The difference was that the casting solution in step one consisted of the following components by mass: 18 parts polyethersulfone, 50 parts dimethylformamide, 30 parts polyvinylpyrrolidone, and 4 parts water. The temperature was 20°C, the solid content was 17.64%, and the viscosity was 39,000 cps. The first coagulation bath in step three lasted 2 seconds, and the dimethylformamide content in the second coagulation bath in step four was 25% by mass. No stretching was performed. The final polyethersulfone hollow fiber ultrafiltration membrane had a pore density of 245 pores / 25 μm at the outlet liquid surface. 2 The pore density of the inner liquid inlet surface is 183 pores / 25μm. 2 This means that the number of holes on the outer liquid surface is much greater than the number of holes on the inner liquid surface, resulting in very low pressure resistance on the outer liquid surface. Consequently, the overall mechanical strength of the membrane is low, with a tensile strength of 86cN, which does not meet the requirements of practical applications. At the same time, too much colloid will enter the membrane fiber, blocking the entire membrane fiber and the liquid inlet, making it impossible to successfully prepare a usable hollow fiber membrane module.

[0173] Comparative Example 2

[0174] A 50 kDa polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method in Example 3. The difference was that step three, which involved rapid initial phase separation, was omitted, and in step four, the mass content of dimethylformamide in the second coagulation bath was 40%, the temperature of the second coagulation bath was 100°C, and no stretching operation was performed. The final polyethersulfone hollow fiber ultrafiltration membrane had a pore density of 18 pores / 25 μm at the outlet liquid surface. 2 The average SEM pore size of the first pore is 45 nm. Its pore density and corresponding average SEM pore size are very small. The overall initial water flux of the membrane is 5.23 LMH / psi, which does not meet the requirements. Moreover, when it is processed into a hollow fiber membrane module, it is difficult for the colloid to enter the membrane fiber, resulting in insufficient adhesion and making it impossible to obtain a qualified hollow fiber membrane module.

[0175] Comparative Example 3

[0176] A 50kD polyethersulfone hollow fiber ultrafiltration membrane was prepared according to the preparation method of Example 3. The difference was that the composition of the casting solution in step one included the following components by mass: 16 parts polyethersulfone, 50 parts dimethylformamide, 30 parts polyvinylpyrrolidone, and 4 parts water. The temperature was 20°C, the solid content was 16.00%, and the viscosity was 14,000 cps. The temperature of the first coagulation bath in step three and the temperature of the second coagulation bath in step four were both 20°C. No stretching operation was performed. The SEM average pore size of the first pore on the liquid surface of the final polyethersulfone hollow fiber ultrafiltration membrane was 1100 nm, and the overall porosity of the membrane was 82%. The high porosity indicated that the number of membrane pores was too large, resulting in a low overall mechanical strength of the membrane. Its tensile strength was 74 cN. At the same time, too much colloid entered the membrane fiber interior, which blocked the entire membrane fiber interior and blocked the liquid inlet, making it impossible to successfully prepare a usable hollow fiber membrane module.

[0177] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A sulfone polymer hollow fiber ultrafiltration membrane, comprising a main body, one side of which is an inner liquid inlet surface facing the inner cavity, and the other side of which is an outer liquid outlet surface, wherein the main body has a non-directional tortuous pathway, characterized in that: The outer liquid surface includes a plurality of first holes, the average SEM pore size of the first holes is 50nm-1000nm, and the pore density of the outer liquid surface is 20 / 25μm²-200 / 25μm². The inner liquid inlet surface includes a plurality of second holes, and the ratio of the average SEM pore diameter of the second holes to the average SEM pore diameter of the first holes is 1:2-10. The ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid outlet surface is 0.8-15; The overall porosity of the ultrafiltration membrane is 30%-80%.

2. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 1, characterized in that: The average SEM pore size of the second hole is 3nm-450nm; The pore density of the inner liquid inlet surface is 30 pores / 25μm² to 800 pores / 25μm². And / or, The ratio of the pore density of the inner liquid inlet surface to the pore density of the outer liquid outlet surface is 1.1-10.

3. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 1, characterized in that: The surface energy of the ultrafiltration membrane at the liquid surface outside the membrane is not less than 60 mN / m; The surface roughness of the ultrafiltration membrane outside the liquid is 3μm-50μm; The average SEM pore size of the first pore is 80nm-400nm, and the pore density at the outer liquid surface is 25 pores / 25μm. 2 -150 pieces / 25μm 2 .

4. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 3, characterized in that: The surface energy of the outer liquid surface of the ultrafiltration membrane is 65mN / m-90mN / m.

5. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 3, characterized in that: The surface roughness of the ultrafiltration membrane outside the liquid is 5μm-35μm.

6. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 1, characterized in that: In the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore size of the main body first increases and then decreases; The main body includes a macroporous region, and the nearest average distance A from the macroporous region to the outer liquid surface is not less than 15 μm; Furthermore, the nearest average distance B from the large-aperture area to the inner liquid inlet surface is not less than 15 μm. The overall porosity of the ultrafiltration membrane is 35%-70%.

7. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 6, characterized in that: The thickness of the macroporous region is 40μm-120μm; The ratio of the thickness of the macropore region to the overall membrane thickness is 0.25-0.6; And / or, The ratio of the average SEM aperture of the large aperture area to the average SEM aperture of the first aperture is 3-20.

8. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 6, characterized in that: The nearest average distance A from the macropore region to the outer liquid surface is 20μm-60μm, and the ratio of this distance A to the film thickness is 0.1-0.

5. And / or, The ratio of the nearest average distance A from the large orifice area to the outer liquid surface to the nearest average distance B from the large orifice area to the inner liquid surface is 0.6-2.

5.

9. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 6, characterized in that: The macroporous region contains a first cross-sectional fiber that forms a porous structure, and the SEM average diameter of the first cross-sectional fiber is 20nm-180nm. And / or, The ratio of the average SEM pore size of the macropore region to the average SEM diameter of the fiber in the first cross-section is 5-30.

10. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 6, characterized in that: Along the thickness direction from the inner liquid inlet surface to the outer liquid outlet surface, the average pore diameter of the main body first increases, then decreases, and then increases again. The main body includes a small pore region located between the large pore region and the outer liquid outlet surface. The nearest average distance C from the orifice area to the outer liquid surface is not less than 2 μm; The overall porosity of the ultrafiltration membrane is 40%-65%.

11. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 10, characterized in that: The thickness of the aperture region is 5μm-30μm; The ratio of the thickness of the pore region to the overall thickness of the membrane is 0.05-0.15; And / or, The ratio of the thickness of the small hole region to the thickness of the large hole region is 0.1-0.

4.

12. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 10, characterized in that: The average SEM pore size of the small-pore region is 0.1-0.4 times the average SEM pore size of the large-pore region. And / or, The pore region contains a second cross-sectional fiber that forms a porous structure, and the SEM average diameter of the second cross-sectional fiber is 10nm-150nm.

13. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 10, characterized in that: The nearest average distance C from the orifice region to the outer liquid surface is 4μm-20μm; the ratio of this distance C to the film thickness is 0.04-0.

1. And / or, The ratio of the nearest average distance C from the small orifice area to the outer liquid surface to the nearest average distance A from the large orifice area to the outer liquid surface is 1:2-15.

14. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 1, characterized in that... : The initial water flux of the ultrafiltration membrane is 0.5 LMH / psi to 300 LMH / psi; The ultrafiltration membrane has a water flux of more than 70% of its initial water flux after 10 complete uses; The tensile strength of the ultrafiltration membrane is 100cN-350cN, and the elongation at break is not less than 15%. The thickness of the membrane is 90μm-200μm.

15. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 14, characterized in that... The initial water flux of the ultrafiltration membrane is 1 LMH / psi to 250 LMH / psi.

16. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 14, characterized in that... The tensile strength of the ultrafiltration membrane is 160 cN-280 cN.

17. The sulfone polymer hollow fiber ultrafiltration membrane according to claim 14, characterized in that... The elongation at break of the ultrafiltration membrane is 20%-150%.

18. A method for preparing a sulfone polymer hollow fiber ultrafiltration membrane as described in any one of claims 1-17, characterized in that: Includes the following steps: Step 1: Preparation of casting solution and core solution: The casting solution comprises a sulfone polymer, a first organic solvent, a hydrophilic additive, and a non-solvent; the solid content of the sulfone polymer in the casting solution is 15%-25%, and the viscosity of the casting solution is 10,000-100,000 cps; The core fluid comprises a second organic solvent and water, wherein the mass content of the second organic solvent in the core fluid is 0-40%; Step 2: Spinning: The casting solution and core solution obtained in Step 1 are extruded together from the spinneret to form a molded product with an inner liquid inlet surface and an outer liquid outlet surface. The temperature of the casting solution is 20-40℃. Step 3: Rapid Preliminary Phase Separation: The molded product obtained in Step 2 is immersed in the first coagulation bath for rapid phase separation treatment. The phase separation time is 0.1-1.2 s. The temperature of the first coagulation bath is 5-50°C higher than that of the casting solution to form a film. The first coagulation bath contains water and a third organic solvent, and the mass content of the third organic solvent is greater than 50%. Step 4: Complete Phase Separation: Immerse the green film obtained in Step 3 into the second coagulation bath for complete phase separation treatment. The phase separation time is 30-80 seconds, and the temperature of the second coagulation bath is not lower than the temperature of the casting solution. The second coagulation bath contains water and a fourth organic solvent, and the mass content of the fourth organic solvent is not greater than 30%. Step 5: Cleaning and drying: The raw membrane obtained in step 4 is cleaned with pure water and then dried to obtain a sulfone polymer hollow fiber ultrafiltration membrane.

19. The method for preparing a sulfone polymer hollow fiber ultrafiltration membrane according to claim 18, characterized in that: The sulfone polymer is at least one of bisphenol A polysulfone, polyethersulfone, polyphenylsulfone, and sulfonated polyethersulfone; The first organic solvent, the second organic solvent, the third organic solvent, and the fourth organic solvent are all at least one of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, and dimethyl sulfoxide; The hydrophilic additive is at least one of polyethylene glycol, polyvinylpyrrolidone and polyvinyl alcohol; The non-solvent is at least one of water, isopropanol, glycerol, and butanediol.

20. The method for preparing a sulfone polymer hollow fiber ultrafiltration membrane according to claim 18, characterized in that: The non-solvent content in the casting solution is 1%-10% by mass; And / or, The mass content of the third organic solvent in the first coagulation bath is 55%-95%; And / or, The mass content of the fourth organic solvent in the second coagulation bath is 0-25%.

21. The method for preparing a sulfone polymer hollow fiber ultrafiltration membrane according to claim 18, characterized in that: The temperature of the first coagulation bath is 30-50°C higher than that of the casting solution. And / or, The temperature of the second coagulation bath is 10-45°C lower than that of the first coagulation bath; And / or, In step four, when the phase separation is complete, the growing film is stretched with a stretching rate of 1%-5%.

22. A sulfone polymer hollow fiber ultrafiltration membrane module, characterized in that: It comprises the sulfone polymer hollow fiber ultrafiltration membrane and the cylindrical shell as described in any one of claims 1-17; The ultrafiltration membrane is located inside the cylindrical shell, and the ultrafiltration membrane is bonded together by a colloid. The inner diameter of the ultrafiltration membrane is 0.4-2.0 mm.

23. The application of the sulfone polymer hollow fiber ultrafiltration membrane according to any one of claims 1-17, characterized in that: The ultrafiltration membrane is used in a tangential flow manner for: (a) Purification, concentration, and dialysis of vaccines or viral vectors; (b) Protein concentration and dialysis; (c) Clarification and filtration of cells and bacteria in the fermentation broth; (d) Recovery and dialysis of cells and bacterial cells; (e) Nucleic acid concentration; (f) Preparation of pyrogen-free buffer solution; (g) Small molecule extraction and purification of antibiotics to remove macromolecular impurities; (h) Small molecule active substances / small molecule antibiotics remove pyrogens; (i) Antibody concentration.

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