An asymmetric polyethersulfone filter membrane for virus removal and its preparation method

Abstract

This invention provides an asymmetric polyethersulfone filter membrane for virus removal and its preparation method. The filter membrane comprises a main body, one side of which is a first porous outer surface, and the other side of which is a second porous outer surface. The average pore size of the first porous outer surface is 150-450 nm, and its pore area ratio is relatively small, ranging from 0.10% to 2%. The average pore size of the second porous outer surface is 10-40 nm, and its pore area ratio is relatively large, ranging from 2.1% to 10%. The main body includes a pre-filtration layer and a separation layer for virus interception. One side of the pre-filtration layer is the first porous outer surface, and one side of the separation layer is the second porous outer surface. The other side of the pre-filtration layer and the other side of the separation layer are transitioned by continuous fibers. This polyethersulfone filter membrane is prepared using only one casting solution, integrally molded, and does not require composite processing, making the preparation process relatively simple. Simultaneously, this filter membrane has a strong interception effect on small viruses with a particle size of 20 nm and above. Furthermore, the filter membrane has high mechanical strength, is easy to process, and meets the needs of practical applications.

Description

Technical Field

[0001] This invention relates to the field of membrane materials technology, and more specifically to an asymmetric polyethersulfone filter membrane for virus removal and its preparation method. Background Technology

[0002] In recent years, in addition to plasma fractionation preparations derived from human blood, there is also a need to improve the safety of viruses in biopharmaceuticals. Therefore, pharmaceutical manufacturers have been researching the introduction of virus removal / inactivation processes into the manufacturing process. Among them, the virus removal method using virus-removing membranes is an effective method that can reduce the virus without denaturing useful proteins.

[0003] In the field of plasma fractionation formulations, there are numerous cases of human infection caused by parvovirus B19; in the field of biopharmaceuticals, there have also been cases of mouse parvovirus contaminating Chinese hamster ovary (CHO) cells. This is because parvoviruses lack an envelope, making them physicochemically stable and resistant to the heating, low pH, and chemical treatments commonly used in drug manufacturing processes as inactivation steps. Therefore, there is an increasing demand for methods that utilize the removal of viral membranes to eliminate parvoviruses, as these methods differ from inactivation.

[0004] For example, Chinese patent CN1759924B (applied by EMD Millipore) discloses a multilayer composite ultrafiltration membrane, which (as shown in the attached) Figure 10 The membrane comprises at least one first porous membrane layer having a first side and an equivalent second side, and at least one second porous membrane layer having an equivalent first side and a second side, wherein the first layer and the second layer are superimposed and have a porosity transition region from the equivalent first side of the second layer to the equivalent second side of the first layer, wherein at least one of the layers is an asymmetric ultrafiltration membrane; the membrane structure thus formed has a strong retention effect on parvoviruses and can achieve a high protein yield, meeting the needs of practical applications.

[0005] However, this composite ultrafiltration membrane requires at least two different casting solutions to be prepared, and the composite process involves casting two solutions (e.g., with a single mold coating machine) together. Figure 11The casting thickness of the first polymer solution is adjusted to a suitable thickness, and the casting thickness of the second polymer solution is adjusted to a final layer thickness of 15 micrometers or about 10% of the total membrane thickness. The formation conditions are selected so that the first solution is rapidly heated above its turbidity point on the casting drum before immersion in a water bath at 55°C, while the second solution has not yet reached its turbidity point. This allows the first polymer solution to form a microporous layer and the second polymer solution to form an ultrafiltration layer. The preparation of multiple casting solutions is relatively cumbersome, the composite process is complex, and the economic cost is high, which to some extent limits the development of virus removal membranes. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an asymmetric polyethersulfone filter membrane for virus removal and its preparation method. This polyethersulfone filter membrane is prepared using only one casting solution, is integrally molded, does not require composite processing, and has a relatively simple preparation process. Furthermore, the resulting polyethersulfone filter membrane exhibits strong virus retention and possesses high mechanical strength, meeting the needs of practical applications.

[0007] To achieve the above objectives, the present invention provides the following technical solution: an asymmetric polyethersulfone filter membrane for virus removal, comprising a body having a non-directional tortuous pathway, one side surface of the body being a first porous outer surface, and the other side surface of the body being a second porous outer surface, wherein the average pore size of the first porous outer surface is 150-450 nm, and the average pore size of the second porous outer surface is 10-40 nm;

[0008] The pore area ratio on the first porous outer surface is 0.10%-2%, and the pore area ratio on the second porous outer surface is 2.1%-10%. The main body includes a pre-filter layer and a separation layer for intercepting viruses. One side of the pre-filter layer is the first porous outer surface, and one side of the separation layer is the second porous outer surface. The other side of the pre-filter layer and the other side of the separation layer are transitioned by continuous fibers. For colloidal gold with a particle size of 20 nm, the LRV of the filter membrane is not less than 4.

[0009] In the membrane body structure of the polyethersulfone filter membrane provided by the present invention, it can be clearly seen that the pore sizes on the two outer surfaces of the filter membrane are different, with a certain gap; the pore size on one of the outer surfaces is larger, and the outer surface with larger pore size is referred to as the first porous outer surface in the present invention, that is, the first porous outer surface is the macropore surface of the filter membrane, and the average pore size of the first porous outer surface is 150-450nm. Preferably, the average pore size of the first porous outer surface is 200-400nm. The presence of the macropore surface is beneficial to improving the overall filtration speed of the membrane, resulting in a shorter fluid filtration time and lower time cost.

[0010] The pores on the other outer surface of the filter membrane are smaller in diameter. This outer surface with smaller pore diameter is referred to as the second porous outer surface in this invention. The second porous outer surface is the pore surface of the filter membrane, with an average pore size of 10-40 nm. Preferably, the average pore size of the second porous outer surface is 15-35 nm. The presence of the pore surface helps improve the filtration accuracy of the membrane, ensuring that the polyethersulfone filter membrane also has a high retention capacity for parvoviruses. In this invention, the average pore sizes of the first and second porous outer surfaces are different and have a certain gap, indicating that the polyethersulfone filter membrane is an asymmetric membrane. This ensures that the membrane as a whole has a fast filtration speed, a large dirt-holding capacity, and a long service life, while also ensuring a strong capture capacity for parvoviruses (especially parvoviruses with a particle size of about 20 nm), meeting the needs of practical applications.

[0011] As is well known, the pore size, number, and shape of membrane pores have a significant impact on membrane filtration accuracy (retention efficiency), membrane flow rate, and other properties. Generally, in asymmetric filter membranes, the pore area ratio (pore area / corresponding membrane area) of the macropore surface is greater than that of the micropore surface (when the number of pores is basically the same, the larger the pore size, the greater the pore area ratio). However, the polyethersulfone filter membrane of this invention is the opposite. The pore area ratio of its macropore surface (first porous outer surface) is smaller than that of its micropore surface (second porous outer surface), and both outer surfaces have suitable pore area ratios. This not only allows the polyethersulfone filter membrane to have a higher flow rate, facilitating rapid fluid passage through the porous membrane and shortening filtration time, but also provides greater mechanical strength, high tensile strength, high industrial value, and long service life.

[0012] Furthermore, by observing the main structure of the membrane, it was found that the entire filter membrane of the present invention is mainly divided into two regions in the thickness direction. One region is a pre-filtration layer containing a first porous outer surface, whose internal pores have relatively large pore sizes and are mainly used to intercept large particulate impurities in the fluid. The pre-filtration layer has a large dirt holding capacity and a fast flow rate; and it can provide support and protection for the separation layer. The other region is a separation layer containing a second porous outer surface, whose internal pores have relatively small pore sizes and are mainly used to intercept fine particulate impurities, such as small viruses in proteins, ensuring that the filter membrane also has a high capture capacity for viruses. Therefore, this polyethersulfone filter membrane is particularly suitable for use as a virus removal membrane.

[0013] Furthermore, the other side of the pre-filtration layer (the side of the pre-filtration layer facing away from the first porous outer surface) and the other side of the separation layer (the side of the separation layer facing away from the second porous outer surface) transition with continuous fibers. It can be understood that "continuous" means that essentially all the fibers are integrally connected to each other, as if formed in one piece, without the use of additional adhesives or the like to connect them. Unless torn by external force, the network of fibers cannot be separated from each other. Simultaneously, the continuous network of fibers is also interconnected with the first porous outer surface and the second porous surface. In this invention, the polyethersulfone filter membrane is made of uniform material throughout, meaning the entire membrane is made of polyethersulfone material without any material variation. This proves that the polyethersulfone filter membrane is integrally formed without undergoing processes such as "composite bonding."

[0014] The viruses intercepted in this invention are mainly various viruses with a particle size of 20 nm and above (e.g., mouse parvovirus, whose particle size is around 20 nm); by using a colloid with a particle size of 20 nm as the interception agent,

[0015] After retention testing, it was found that its LRV was not less than 4, indicating that the polyethersulfone filter membrane has a very high virus retention rate and plays a sufficient role in retaining viral impurities, meeting the needs of practical applications. In addition, the test method for viral impurities can also refer to patents CN105980037B-Virus Removal Membrane, CN101816898B-Ultrafiltration Membrane and its Preparation Method, CN1759924B-Ultrafiltration Membrane and its Preparation Method, etc.

[0016] In this invention, an asymmetric membrane should be understood as a membrane in which the pre-filtration layer and the separation layer are both composed of the same material, the two layers are combined into a single structure, and are formed directly during the membrane preparation process; in the transition from the pre-filtration layer to the separation layer, there is only a change in the membrane structure; in contrast, there is, for example, a composite membrane, which has a multi-layer structure, in which a dense layer serving as the separation layer is coated onto a porous, often microporous, support layer or support membrane in a separate process step, and the materials constituting the support layer and the separation layer in the composite membrane are often different;

[0017] The average pore size of a membrane surface can be measured by characterizing the membrane structure using a scanning electron microscope (SEM), followed by measurement using computer software (such as Matlab, NIS-Elements, etc.) or manually, and then performing corresponding calculations. During membrane fabrication, in the direction perpendicular to the membrane thickness (if the membrane is a flat sheet, this direction is planar; if the membrane is a hollow fiber membrane, this direction is perpendicular to the radius), its characteristics, such as pore size distribution, are roughly uniform and consistent. Therefore, the average pore size of a certain area on the corresponding plane can reflect the overall average pore size on that plane. In actual measurement, the membrane surface can be characterized using an electron microscope to obtain the corresponding SEM image. Since the pores on the membrane surface are roughly uniform, a certain area, such as 1 μm, can be selected. 2 (1μm x 1μm) or 25μm 2 (5μm by 5μm), the specific area size depends on the actual situation. Then, use appropriate computer software or manual measurement to determine the diameter of all holes on this area, and then calculate to obtain the average pore diameter of the surface. Of course, those skilled in the art can also obtain the above parameters through other measurement methods. The above measurement methods are for reference only.

[0018] As a further improvement of the present invention, the first porous outer surface has a plurality of circular first holes; the second porous outer surface has a plurality of circular second holes; the difference between the hole area ratio on the second outer surface and the hole area ratio on the first outer surface is greater than 1.5%.

[0019] In the membrane structure of the polyethersulfone filter membrane provided by this invention, it can be clearly seen that a certain number of first pores with a certain pore size exist on the first porous outer surface of the membrane. It is well known that the pore size, number, and shape of the membrane pores have a significant impact on the membrane's filtration accuracy (retention efficiency), membrane flow rate, and other properties. In this invention, the first pores on the first porous outer surface are circular pores; some are circular, and some are elliptical. Simultaneously, it can also be seen that a certain number of second pores with a certain pore size exist on the second porous outer surface of the membrane. In this invention, the second pores on the second porous outer surface are also circular pores; some are circular, and some are elliptical. The two pores are elliptical; the round pores of the first and second pores are more likely to trap viruses; in addition, the difference between the pore area ratio of the second pore on the second outer surface and the pore area ratio of the first pore on the first outer surface (the value obtained by subtracting the pore area ratio of the first pore from the pore area ratio of the second outer surface) is greater than 1.5%, that is, there are more second pores on the small pore surface (the second porous outer surface) and fewer first pores on the large pore surface (the first porous outer surface). This difference in pore area ratio further ensures that the membrane as a whole has high tensile strength and elongation at break, making it suitable for various processing; and it also makes the filter membrane have a large flux, enabling it to filter various fluids quickly and efficiently.

[0020] As a further improvement of the present invention, the pre-filter layer includes a skin region and a pre-filter region, the skin region being located on the side of the pre-filter layer away from the separation layer, one side of the skin region including a first porous outer surface, and the thickness of the skin region being 0.3-3.2 μm.

[0021] In the main structure of the filter membrane of this invention, we found that there is a region within the pre-filtration layer with a small number of pores and a very low porosity. This region is called the skin layer, and it is located on the side of the pre-filtration layer facing away from the separation layer. The most significant characteristic of the skin layer is its small number of pores and low porosity. The surface of this skin layer facing away from the separation layer is the first porous outer surface. Although the average pore size of the first pores on the first porous outer surface is still relatively large, the pore area ratio of the first pores on the first porous outer surface is still smaller than that of the second pores on the second porous outer surface. The presence of the skin layer helps to improve the tensile strength of the membrane and provides support and protection for the separation layer, making the membrane more pressure-resistant, less prone to breakage, and with a longer service life. Furthermore, measurements show that the thickness of the skin layer is 0.3-3.2 μm, which is relatively small. This thickness not only improves the membrane's support strength but also does not affect the overall filtration speed or dirt holding capacity of the membrane.

[0022] As a further improvement of the present invention, the filter membrane has an average pore size of 15-25 nm, a thickness of 50-150 μm, and a porosity of 70-85%.

[0023] The average pore size of the filter membrane was tested using a PMI pore size analyzer. The test results showed that the average PMI pore size of the filter membrane of this invention was 15-25 nm. Furthermore, the synergistic effect of the tortuous pathway of the membrane structure and the certain thickness of the membrane ensured that the polyethersulfone filter membrane had a strong retention effect on nanoscale small viruses (even mouse parvovirus with a particle size of 20 nm), which could meet the needs of practical applications and was suitable for use as a virus membrane.

[0024] The membrane thickness can be determined by characterizing the membrane structure using a scanning electron microscope, followed by calculation using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement. Of course, those skilled in the art can also obtain the above parameters using other measurement methods, which are for reference only. When the membrane thickness is too small, its mechanical strength will be low; simultaneously, due to the short filtration time, effective filtration will be impossible. When the membrane thickness is too large, the filtration time will be too long, resulting in excessive time costs. The polyethersulfone filter membrane of this invention has a thickness of 50-150 μm, ensuring that the polyethersulfone filter membrane not only has high mechanical strength but also enables effective filtration with high filtration efficiency, short filtration time, and low time costs.

[0025] When the membrane porosity is too high, it leads to low tensile strength, poor mechanical properties, and low industrial practical value, failing to meet market demands. Conversely, when the membrane porosity is too low, it affects the membrane flow rate, resulting in slower filtration speed, longer filtration time, and higher time costs. Furthermore, it results in low dirt-holding capacity and a short service life, requiring frequent membrane replacements and significantly increasing economic costs. The porous membrane in this invention has a porosity of 70-85%, giving it not only good tensile strength but also a fast filtration speed, high flow rate, and high dirt-holding capacity, enabling it to trap a large number of impurity particles, resulting in a long service life and lower economic costs.

[0026] As a further improvement of the present invention, the average pore size variation gradient of the filter membrane is 1.5-6μm / 1μm; the ratio of the average pore size of the first porous outer surface to the average pore size of the second porous outer surface is 7-23.

[0027] In this invention, the pore size of the filter membrane varies gradually with thickness, decreasing from a large pore surface to a small pore surface. The ratio of the average pore size of the two outer surfaces can be called the asymmetry factor. The smaller the value (closer to 1), the stronger the symmetry of the two outer surfaces of the filter membrane; the larger the value, the greater the asymmetry of the two outer surfaces of the filter membrane. Measurements show that the ratio of the average pore size of the first porous outer surface to that of the second porous outer surface is 7-23, preferably 10-20. This indicates that the two outer surfaces of the polyethersulfone filter membrane of this invention are asymmetrical, but the asymmetry is not significant. This asymmetrical structure not only ensures that the filter membrane has a large flux and a long service life, but also ensures that the filter membrane has a high virus rejection efficiency, meeting the actual application requirements.

[0028] Since the pore size of the polyethersulfone filter membrane varies with the membrane thickness gradient, this invention uses the magnitude of the average pore size change gradient to reflect the rate of change of the membrane pore size with thickness. The larger the value, the faster the pore size changes; the smaller the value, the smaller the pore size changes. This value can be obtained by (average pore size of the first porous outer surface - average pore size of the second porous outer surface) / thickness, so the unit is μm (representing pore size) / 1μm (representing thickness). In this invention, the average pore size change gradient of the filter membrane is 1.5-6μm / 1μm, which is relatively small. This indicates that the membrane pore size of this invention changes with thickness in a small gradient, and the membrane pore size will not change too quickly, nor will there be excessively large pores (if there are excessively large pores, the filter membrane will not be pressure resistant, and under pressure, the filter membrane will easily break, resulting in a short service life). This ensures both efficient virus interception and a fast flux, as well as a large dirt holding capacity. In addition, the pre-filtration layer of the filter membrane can also provide support and protection for the separation layer, improving the overall mechanical strength of the membrane.

[0029] As a further improvement of the present invention, the pre-filter layer includes a first fiber forming a porous structure, the first fiber being a sheet-like structure; the separation layer includes a second fiber forming a porous structure, the second fiber being a strip-like structure.

[0030] In the membrane structure of the PES filter membrane provided by this invention, it can be clearly seen that the fiber structure changes with the membrane thickness. The first fiber in the pre-filtration layer is a sheet-like structure, while the second fiber in the separation layer is a strip-like structure. The pre-filtration layer formed by the sheet-like first fiber is more stable and pressure-resistant, and can provide a certain support and protection for the separation layer. Moreover, the sheet-like fiber structure distribution can help fluid diffusion and improve the interception effect of the pores. The separation layer formed by the strip-like second fiber has a suitable porosity and pore distribution, which further makes the membrane as a whole have a high flow rate and a high virus interception efficiency.

[0031] As a further improvement of the present invention, the average diameter of the first fiber is greater than the average diameter of the second fiber, and the average diameter of the second fiber is 30-75 nm.

[0032] In this invention, the average diameter of the first fiber is larger than that of the second fiber. This is because the pores in the pre-filtration layer are relatively large, and the pores formed by the coarser first fiber are more stable and less prone to collapse or shrinkage, thus ensuring stable fluid flow rate. Furthermore, the average diameter of the second fiber is 30-75 nm, ensuring the stability of the pores within the separation layer and effectively retaining small viral impurities. This structure, with its varying thicknesses of the first and second fibers, helps ensure the membrane as a whole has high mechanical strength and filtration stability, enabling long-term, high-efficiency filtration. Therefore, this PES filter membrane is particularly suitable for use in the field of virus removal.

[0033] The thickness of the fiber cross section can be considered as the diameter of the fiber. In this invention, the average diameter of the second fiber can be calculated by using a scanning electron microscope to characterize the morphology of the filter membrane cross section structure, and then using computer software (such as Matlab, NIS-Elements, etc.) or manual measurement to calculate the average value. Of course, it is understood that those skilled in the art can also obtain the above parameters through other measurement methods.

[0034] As a further improvement of the present invention, the average pore size of the PMI in the pre-filter layer is 50-200 nm, and the porosity is 75-93%; the thickness of the pre-filter layer accounts for 70%-90% of the membrane thickness.

[0035] Compared to the separation layer, the pre-filter layer has larger pore sizes and a higher overall porosity. Testing revealed that the average PMI pore size of the pre-filter layer is 50-200 nm (preferably 60-180 nm), ensuring a high flow rate and sufficient interception of large particles (large-diameter viruses) without affecting the subsequent retention of smaller viruses. It also lacks excessively large pores, providing support and protection for the separation layer, allowing for prolonged and efficient virus capture. Furthermore, it makes the membrane pressure-resistant, less prone to rupture under pressure, and has a long service life. The pre-filter layer accounts for 70%-90% of the overall membrane thickness, indicating that a large portion of the membrane is pre-filtered. The combined effect of large pore size and high porosity (75-93% porosity of the pre-filter layer) ensures high overall membrane flux, fast filtration speed, low time cost, high dirt-holding capacity, and long service life.

[0036] In this invention, the PMI average pore size, porosity, thickness, and other parameters of the pre-filter layer can be obtained by first tearing the polyethersulfone filter membrane into a separation layer and a pre-filter layer, and then testing the corresponding parameters of the pre-filter layer; or by characterizing the morphology of the membrane cross-section structure using a scanning electron microscope, and then calculating the parameters using computer software (such as Matlab, NIS-Elements, etc.) or manually; of course, those skilled in the art can also obtain the above parameters through other measurement methods, and the above measurement methods are for reference only.

[0037] As a further improvement of the present invention, the average pore size of the separation layer is 15-25 nm, the porosity is 60-80%, and the thickness of the separation layer is 2-20 μm.

[0038] Compared to the pre-filter layer, the separation layer has smaller pore size, with an average pore size (PMI average pore size) of 15-25nm. This ensures that the polyethersulfone filter membrane has a high retention efficiency for fine impurities (especially small viruses with a particle size of 20nm), meeting the needs of practical applications and making it particularly suitable for use in the field of virus removal.

[0039] The separation layer has a thickness of 2-20μm, which ensures both impurity removal efficiency and high overall membrane flux, resulting in fast filtration speed and low time cost. At the same time, the porosity of the separation layer is 60-80%, indicating that it can effectively retain small viruses and further improve the membrane's lifespan.

[0040] In this invention, the average pore size, porosity, thickness, and other parameters of the separation layer can be obtained by first tearing the polyethersulfone filter membrane into a separation layer and a pre-filtration layer, and then testing the corresponding parameters of the separation layer; or by characterizing the morphology of the membrane cross-section structure using a scanning electron microscope, and then calculating the parameters using computer software (such as Matlab, NIS-Elements, etc.) or manually; in addition, the thickness of the separation layer can also be tested by using 20nm colloidal gold as an impurity particle for retention, and the length of the 20nm colloidal gold retention area in the filter membrane is the thickness of the separation layer. For specific testing methods, please refer to Chinese Patent CN105980037B - Membrane for Removing Viruses; of course, those skilled in the art can also obtain the above parameters through other measurement methods, and the above measurement methods are for reference only.

[0041] As a further improvement of the present invention, the pre-filter layer further includes a transition zone located on the side of the pre-filter layer near the separation layer. The continuous fiber forms a porous structure in the transition zone, and the continuous fiber gradually changes from a sheet-like structure to a strip-like structure. The side of the continuous fiber near the separation layer is continuous with the side of the second fiber near the pre-filter layer.

[0042] As a further improvement of the present invention, the average pore size of the transition region is 60-170 nm, the porosity is 75%-82%, and the thickness of the transition region is 4-20 μm.

[0043] In this invention, the pore size and fiber structure of the polyethersulfone filter membrane gradually change with thickness, rather than abruptly. This ensures that the membrane as a whole has high mechanical strength and high tensile strength, meeting the requirements of practical applications. A transition zone exists on the side of the pre-filtration layer near the separation layer. The continuous fibers in the transition zone form a porous structure, ensuring pores of suitable size and excellent porosity. In the direction from the pre-filtration layer towards the separation layer, the continuous fibers gradually change from a sheet-like structure to a strip-like structure. Simultaneously, the side of the continuous fibers near the separation layer is continuous with the side of the second fiber near the pre-filtration layer; "continuous" means that essentially all of them are continuous. The fibers (continuous fibers and second fibers) are integrally interconnected, forming a single unit without the need for additional adhesives. Unless torn by external force, the network of fibers cannot be separated. This demonstrates the uniformity of the material throughout the polyethersulfone filter membrane; the entire membrane is made of polyethersulfone material, integrally formed, with no material variation. The average pore size of the transition zone is 60-170 nm, and the porosity is 75%-82%. The thickness of the transition zone is 4-20 μm. These three factors combined further ensure the filter membrane has a high capture capacity for various viruses, a large flux, fast filtration speed, and high economic efficiency.

[0044] As a further improvement of the present invention, the polyethersulfone filter membrane has a tensile strength of 6-12 MPa and an elongation at break of 8-30%; the flux of the polyethersulfone filter membrane is greater than 600 L*h. -1 *m -2 @30psi; the protein yield of the polyethersulfone filter membrane is not less than 98%.

[0045] The tensile strength and elongation at break are important indicators for evaluating the mechanical strength of filter membranes. Under certain conditions, the greater the tensile strength of the filter membrane, the better its mechanical strength. Tensile strength refers to the membrane's ability to withstand parallel tensile forces. During testing under certain conditions, the membrane sample is subjected to a tensile load until it breaks. Based on the maximum tensile load at the point of failure and the change in the membrane sample's dimensions (length), the tensile strength and elongation at break can be calculated. Both tensile strength and elongation at break can be measured using a universal tensile testing machine. The testing method for tensile strength is well-known in the field; for example, ASTM D790 or ISO 178 details the procedure for tensile strength testing. The filter membrane of this invention has a tensile strength of 6-12 MPa and an elongation at break of 8-30%, indicating that the filter membrane of this invention has high tensile strength and elongation at break, good mechanical properties, high industrial practical value, and fully meets market demands.

[0046] Permeation flux, also known as permeation rate or simply flux, refers to the amount of substance that passes through a unit area of ​​membrane per unit time under a certain operating pressure during the separation process. The magnitude of the flux reflects the filtration speed; a higher flux indicates a faster filtration speed. In this invention, the polyethersulfone membrane has a flux greater than 600 L / h. -1 *m -2 @30psi indicates a relatively high flux, meaning the filter membrane has a fast filtration speed. While ensuring retention efficiency, the fluid can pass through the filter membrane quickly, resulting in lower time costs and higher economic benefits.

[0047] Furthermore, the protein yield of the polyethersulfone filter membrane is not less than 98%, indicating that the effective substance protein in the fluid is not easily adsorbed onto the membrane. On the one hand, it will not clog the membrane pores, ensuring that the filter membrane still has a long service life. On the other hand, it ensures that the content of the effective substance protein in the fluid changes very little, and the protein is basically not lost, thus ensuring economic benefits. The test method for protein yield can refer to patents CN105980037B-Virus Removal Membrane, CN101816898B-Ultrafiltration Membrane and its Preparation Method, CN1759924B-Ultrafiltration Membrane and its Preparation Method, etc.

[0048] On the other hand, the present invention also provides a method for preparing an asymmetric polyethersulfone filter membrane for virus removal, comprising the following steps:

[0049] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 15-30 parts polyethersulfone; 50-80 parts organic solvent; 3-10 parts hydrophilic additive; the viscosity of the casting solution is at least greater than 8000 cps;

[0050] S2: Immerse the liquid film along with the carrier into the curing liquid for at least 20 seconds. The curing liquid penetrates into the interior of the liquid film and gradually diffuses inward, thereby solidifying to form a separation layer and a pre-filter layer. The cloud point of the casting liquid is at least 5°C higher than the temperature of the coagulation bath, and the cloud point of the casting liquid is greater than 25°C.

[0051] As a further improvement of the present invention, the organic solvent is at least one selected from butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone; the hydrophilic additive includes a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid, and 3-aminothiophene-2-carboxamide in a mass ratio of 4:1:1; and the thickness of the liquid film is at least greater than 200 μm.

[0052] As a further improvement of the present invention, the coagulation bath includes water, the temperature of the coagulation bath is 20-50°C, and the cloud point temperature of the casting solution is 30-60°C.

[0053] In preparing the polyethersulfone filter membrane of this invention, a casting solution is first prepared. The casting solution includes the film-forming substance polyethersulfone (PES), an organic solvent (used to solvent the polyethersulfone material), and a hydrophilic additive. The hydrophilic additive includes a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid, and 3-aminothiophene-2-carboxamide. The addition of polyvinylpyrrolidone effectively controls the viscosity of the system, inhibits the formation of macropores during phase separation, and effectively improves the stability of membrane flux. The synergistic effect of these three substances effectively improves the hydrophilicity of the filter membrane surface (thereby increasing protein yield and extending the filter membrane's lifespan), and optimizes the membrane pore structure, facilitating the acquisition of an ideal membrane structure. The viscosity of the casting solution affects the structure and performance of the final filter membrane. Significant effects, such as on the pore size, thickness, and flow rate of the filter membrane; this viscosity setting ensures that the final filter membrane has a suitable thickness and achieves an ideal pore size; the viscosity of the casting solution can be directly obtained using a viscometer; the viscosity of the casting solution in this invention is relatively high, greater than 8000 cps (but the viscosity should not be too high, not exceeding 15000 cps), and the higher the viscosity, the slower the phase separation rate; such viscosity is beneficial for forming a membrane structure with large pore surface area and low pore area ratio, and small pore surface area and high pore area ratio; then the casting solution is cast onto a carrier to form a liquid film; the casting solution of this invention can be cast manually (e.g., by hand pouring, casting, or spreading on a casting surface) or automatically (e.g., by pouring or additional casting on a moving bed); various devices known in the art can be used for casting. Casting equipment includes, for example, mechanical coaters, which include a coating knife, a doctor blade, or a spray / pressurization system. Various casting speeds are known in the art and are suitable, such as casting speeds of about 1-5 feet per minute (fpm), depending on the specific circumstances. Preferably, the thickness of the liquid film is at least greater than 200 μm. This is to ensure that the thickness of the film after formation is greater than 30 μm, so that the film as a whole has high mechanical strength, is suitable for various industrial processing, and has high industrial practical value. However, the larger thickness of the liquid film also requires a longer phase separation time, resulting in a skin structure, that is, a lower pore area ratio of the macropore surface of the film.

[0054] Next, the liquid membrane, along with the carrier, is immersed in the curing solution for at least 20 seconds. The phase separation curing time is preferably 30-70 seconds. A suitable phase separation curing time, combined with the casting solution system, is beneficial for obtaining a filter membrane with an ideal pore size. The curing solution penetrates the interior of the liquid membrane and gradually diffuses inward, eventually solidifying to form a separation layer and a pre-filtration layer. The curing solution contains water; preferably, it may also include a weak solvent, such as pentanol, hexanol, heptanol, octanol, hexane, propane, heptane, and octane. The presence of a weak solvent is more conducive to obtaining an ideal membrane structure, and the overall phase separation rate will be relatively slower, thus forming a skin structure. The key point of this invention in preparing the filter membrane is that the cloud point of the casting solution is at least 5°C higher than the coagulation bath temperature, and the cloud point of the casting solution is greater than 25°C (cloud point of the casting solution: when solids first appear). (The point of precipitation); the preferred coagulation bath temperature is 20-50℃; the cloud point temperature of the casting solution is 30-60℃; in this invention, the cloud point temperature of the casting solution is relatively high, the overall phase separation rate of the casting solution is slowed down, the phase separation is delayed, so a skin forms; the influencing factors of phase separation caused by non-solvents are weakened, while the phase separation factors caused by thermodynamic temperature changes are increased, resulting in a lower pore size ratio at the bottom and improved strength; through this preparation method, the polyethersulfone filter membrane of this invention is prepared by only one casting solution, integrally molded, without the need for composites, and the preparation process is relatively simple; at the same time, the polyethersulfone filter membrane has a strong retention effect on viruses and a high protein yield; and the filter membrane has high mechanical strength, meeting the needs of practical applications; therefore, this polyethersulfone filter membrane is particularly suitable for use as a virus removal membrane.

[0055] The beneficial effects of this invention are as follows: The asymmetric polyethersulfone filter membrane for virus removal comprises a main body with non-directional tortuous pathways within it. One side surface of the main body is a first porous outer surface, which is a macroporous surface with an average pore size of 150-450 nm and a pore area ratio of 0.10%-2%. The other side surface of the main body is a second porous outer surface, which is a microporous surface with an average pore size of 10-40 nm and a pore area ratio of 2.1%-10%. This membrane structure, with its macroporous surface and microporous surface ratio, ensures that the filter membrane not only has high flux and effectively and rapidly filters, but also maintains high tensile strength and high stability. The outer body comprises a pre-filtration layer and a separation layer for virus interception. One side of the pre-filtration layer is a first porous outer surface, and one side of the separation layer is a second porous outer surface. The other side of the pre-filtration layer and the other side of the separation layer are transitioned by continuous fibers. This polyethersulfone filter membrane is integrally prepared using only one casting solution, without the need for composites, making the preparation process relatively simple. Simultaneously, the prepared polyethersulfone filter membrane exhibits strong interception of parvoviruses and achieves a high protein yield, meeting the needs of practical applications. It is particularly suitable for the field of virus removal. Furthermore, this invention provides a method for preparing this filter membrane, which is convenient, rapid, effective, simple to operate, environmentally friendly, and suitable for large-scale promotion. Attached Figure Description

[0056] Figure 1 The image shows a scanning electron microscope (SEM) image of the first outer surface of the PES filter membrane prepared in Example 1, with a magnification of 1000×.

[0057] Figure 2 The image shown is a further magnified scanning electron microscope (SEM) image of the first outer surface of the PES filter membrane prepared in Example 1, with a magnification of 5000×.

[0058] Figure 3 The image shows a scanning electron microscope (SEM) image of the second outer surface of the PES filter membrane prepared in Example 1, with a magnification of 10K×.

[0059] Figure 4 The image shows a further magnified scanning electron microscope (SEM) image of the second outer surface of the PES filter membrane prepared in Example 1, with a magnification of 20K×.

[0060] Figure 5 The image shows a scanning electron microscope (SEM) image of the longitudinal section of the PES filter membrane prepared in Example 1, with a magnification of 500×.

[0061] Figure 6 The image shows a scanning electron microscope (SEM) image of the longitudinal section of the PES filter membrane prepared in Example 1, near the second outer surface, with a magnification of 20K×.

[0062] Figure 7 The image shows a scanning electron microscope (SEM) image of the longitudinal section of the PES filter membrane prepared in Example 1, near the first outer surface, with a magnification of 10K×.

[0063] Figure 8 This is a schematic diagram of the polyethersulfone filter membrane flux testing device of the present invention;

[0064] Figure 9 This is a schematic diagram of the testing apparatus used for testing the retention efficiency of colloidal gold in the polyethersulfone filter membrane of the present invention;

[0065] Figure 10 Scanning electron microscope (SEM) image of the cross-section of the multilayer composite ultrafiltration membrane prepared for patent CN1759924B;

[0066] Figure 11 A schematic diagram of the composite device used to prepare a multilayer composite ultrafiltration membrane for patent CN1759924B. Detailed Implementation

[0067] To more clearly illustrate the overall concept of this application, detailed descriptions are provided below using embodiments. Unless otherwise specified, the raw materials and equipment used to prepare the filter membrane in the following embodiments are commercially available. Specifically, a Hitachi S-5500 scanning electron microscope was used to characterize the structural morphology of the filter membrane.

[0068] Example 1

[0069] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0070] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 23 parts polyethersulfone; 65 parts organic solvent; 6 parts hydrophilic additive; the organic solvent is dimethyl sulfoxide; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, in a mass ratio of 4:1; 1;

[0071] S2: Immerse the liquid film along with the carrier into the curing solution for 45 seconds. The curing solution penetrates into the liquid film and gradually diffuses inward, thus solidifying to form a separation layer and a pre-filter layer. The coagulation bath is water, and the coagulation bath temperature is 30℃. The cloud point temperature of the casting solution is 40℃.

[0072] Example 2

[0073] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0074] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 25 parts polyethersulfone; 68 parts organic solvent; 7 parts hydrophilic additive; the organic solvent is dimethylacetamide; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, in a mass ratio of 4:1; 1;

[0075] S2: Immerse the liquid film along with the carrier in the curing solution for 50 seconds. The curing solution penetrates into the liquid film and gradually diffuses inward, thus solidifying to form a separation layer and a pre-filter layer. The coagulation bath is water, and the coagulation bath temperature is 35℃. The cloud point temperature of the casting solution is 45℃.

[0076] Example 3

[0077] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0078] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 27 parts polyethersulfone; 71 parts organic solvent; 8 parts hydrophilic additive; the organic solvent is butyl lactate; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, in a mass ratio of 4:1:1;

[0079] S2: The liquid film is immersed in the curing liquid along with the carrier for 55 seconds. The curing liquid penetrates into the interior of the liquid film and gradually diffuses inward, thereby solidifying to form a separation layer and a pre-filter layer. The coagulation bath includes water and octanol, with the octanol accounting for 8% of the total volume of the coagulation bath. The coagulation bath temperature is 37°C. The cloud point temperature of the casting solution is 51°C.

[0080] Example 4

[0081] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0082] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 29 parts polyethersulfone; 74 parts organic solvent; 9 parts hydrophilic additive; the organic solvent is ethyl acetate; the hydrophilic additive includes a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, with a mass ratio of 4:1; 1;

[0083] S2: The liquid film is immersed in the curing liquid along with the carrier for 60 seconds. The curing liquid penetrates into the liquid film and gradually diffuses inward, thus solidifying to form a separation layer and a pre-filter layer. The coagulation bath includes water and pentane, with the volume of pentane accounting for 13% of the total volume of the coagulation bath. The coagulation bath temperature is 40℃. The cloud point temperature of the casting solution is 56℃.

[0084] Example 5

[0085] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0086] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 20 parts polyethersulfone; 60 parts organic solvent; 5 parts hydrophilic additive; the organic solvent is N-ethylpyrrolidone; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, in a mass ratio of 4:1; 1;

[0087] S2: The liquid film is immersed in the curing liquid along with the carrier for 38 seconds. The curing liquid penetrates into the interior of the liquid film and gradually diffuses inward, thereby solidifying to form a separation layer and a pre-filter layer. The coagulation bath is water, and the coagulation bath temperature is 25°C. The cloud point temperature of the casting liquid is 35°C.

[0088] Example 6

[0089] A method for preparing an asymmetric polyethersulfone filter membrane for virus removal includes the following steps:

[0090] S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 18 parts polyethersulfone; 55 parts organic solvent; 4 parts hydrophilic additive; the organic solvent is caprolactam; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide, in a mass ratio of 4:1; 1;

[0091] S2: Immerse the liquid film along with the carrier into the curing solution for 32 seconds. The curing solution penetrates into the liquid film and gradually diffuses inward, thus solidifying to form a separation layer and a pre-filter layer. The coagulation bath is water, and the coagulation bath temperature is 22℃. The cloud point temperature of the casting solution is 30℃.

[0092] 1. Structural Characterization

[0093] The morphology of the nanoscale polymer filter membranes obtained in each embodiment was characterized using scanning electron microscopy, and the required data were then obtained; the specific results are shown in the table below:

[0094] Table 1:

[0095]

[0096] Table 2 - Polyethersulfone filter membrane substrate:

[0097] Thickness / μm Porosity / % PMI average pore size / nm Example 1 85 78.2 20.7 Example 2 97 76.8 21.4 Example 3 109 75.6 22.1 Example 4 125 74.4 22.9 Example 5 76 79.3 19.6 Example 6 67 80.5 18.4

[0098] Table 3 - Separation Layer and Pre-Filter Layer:

[0099]

[0100] Table 4 - Transition Zones and Cortical Zones:

[0101] Transition region thickness / μm Transition zone porosity / % Transition region PMI average pore size / nm Cortical thickness / μm Example 1 13 80.1 114 0.8 Example 2 15 78.4 133 1.3 Example 3 17 77.2 147 1.9 Example 4 19 75.7 159 2.5 Example 5 10 80.8 102 0.6 Example 6 7 81.6 93 0.4

[0102] As shown in Tables 1-4, the polyethersulfone filter membranes prepared in Examples 1-6 of this invention all have ideal membrane structures. The filter membranes are integrally formed without composite processes, making the preparation process simple. Furthermore, the polyethersulfone filter membrane is an asymmetric membrane, with the pore size varying slightly with the thickness, and there are no particularly large pores. This ensures both high efficiency in virus retention and high flux, making the polyethersulfone filter membrane suitable for use in the field of virus removal.

[0103] Performance characteristics

[0104] Membrane flux is calculated as follows:

[0105] The formula for calculating membrane flux (J) is: J = V / (T × A) where:

[0106] J -- Membrane flux unit: L*h-1*m-2

[0107] V -- Sampling volume (L); T -- Sampling time (h); A -- Effective membrane area (m2)

[0108] The operating conditions used for determining the separation performance of the polyethersulfone filter membrane in this invention are as follows: the feed solution is deionized water, the operating pressure is 30 psi, the operating temperature is 25°C, and the solution pH is 7; the flux testing device is... Figure 8 ;

[0109] Tensile strength / MPa Elongation at break / % Flux / L*h-1*m-2@30psi Example 1 7.5 19 1000 Example 2 8.9 16 880 Example 3 9.7 13 810 Example 4 10.6 10 760 Example 5 6.8 23 1140 Example 6 6.3 28 1270

[0110] As shown in the table above, the polyethersulfone filter membranes prepared in Examples 1-6 have good tensile strength and elongation at break, are suitable for various processing, and have strong industrial applicability; at the same time, they have high throughput, fast and efficient filtration speed, and high economic benefits.

[0111] In addition, virus retention testing can be performed according to the test method used in paragraph 114 of CN201010154974.7 - Ultrafiltration Membrane and its Preparation Method:

[0112] The virus used was a mouse parvovirus with a particle size of 20 nm;

[0113] After testing, it was found that the polyethersulfone filter membranes prepared in Examples 1-6 had an LRV of not less than 4 for viral impurities with a particle size of 20 nm, thus demonstrating that the polyethersulfone filter membrane of the present invention has a sufficient retention effect on viruses of 20 nm and above; and the protein yield of the polyethersulfone filter membrane is not less than 98%; therefore, the polyethersulfone filter membrane is particularly suitable for use in the field of virus removal.

[0114] Filtration accuracy test: The interception efficiency of the polyethersulfone filter membranes obtained in each example was tested; intercepted particles: colloidal gold with a particle size of 20 nm.

[0115] Experimental equipment: Tianjin Logan KB-3 particle counter; Experimental preparation: according to... Figure 9 Assemble the experimental apparatus, ensuring it is clean, and rinse it with ultrapure water; take a 47mm diameter filter membrane and place it in the butterfly filter, ensuring the assembled filter has good airtightness.

[0116] Experimental steps:

[0117] Pour the challenge solution into the storage tank, paying attention to the venting of the butterfly filter, pressurize to 10 kPa, and use a clean bottle to collect the downstream filtrate from the butterfly filter.

[0118] Use a particle counter to test the number of particles in the filtrate and the original solution.

[0119] Interception efficiency:

[0120] In the formula:

[0121] η─── Interception efficiency, %;

[0122] n0───Number of particles in the original solution, the average of 5 counts, in units;

[0123] n1 ─── Number of particles in the filtrate, the average of 5 counts, in units.

[0124] After testing, it was found that the polyethersulfone filter membranes prepared in Examples 1-6 all had a retention efficiency of no less than 99.99% for colloidal gold with a particle size of 20 nm. This further demonstrates that the polyethersulfone filter membrane has a strong retention effect on various viruses with a particle size of 20 nm and above, meeting the needs of practical applications.

[0125] 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. An asymmetric polyethersulfone filter membrane for virus removal, comprising a body having non-directional tortuous pathways within the body, one side surface of the body being a first porous outer surface, and the other side surface of the body being a second porous outer surface, characterized in that: The average pore size of the first porous outer surface is 150-450 nm, and the average pore size of the second porous outer surface is 10-40 nm; The pore area ratio on the first porous outer surface is 0.10%-2%, and the pore area ratio on the second porous outer surface is 2.1%-10%. The main body includes a pre-filter layer and a separation layer for intercepting viruses. One side of the pre-filter layer is a first porous outer surface, and one side of the separation layer is a second porous outer surface. The other side of the pre-filter layer and the other side of the separation layer are transitioned by continuous fibers. For colloidal gold with a particle size of 20 nm, the LRV of the filter membrane is not less than 4; The filter membrane has an average pore size of 15-25 nm, a thickness of 50-150 μm, and a porosity of 70-85%. The average pore size variation gradient of the filter membrane is 1.5-6 nm / 1 μm.

2. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The first porous outer surface has a plurality of circular first holes; the second porous outer surface has a plurality of circular second holes. The difference between the porosity on the second outer surface and the porosity on the first outer surface is greater than 1.5%.

3. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The pre-filter layer includes a cortex region and a pre-filter region. The cortex region is located on the side of the pre-filter layer opposite to the separation layer. One side of the cortex region includes a first porous outer surface. The thickness of the cortex region is 0.3-3.2 μm.

4. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The ratio of the average pore diameter of the first porous outer surface to the average pore diameter of the second porous outer surface is 7-23.

5. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The pre-filtration layer includes a first fiber forming a porous structure, the first fiber being a sheet-like structure; the separation layer includes a second fiber forming a porous structure, the second fiber being a strip-like structure.

6. The asymmetric polyethersulfone filter membrane for virus removal according to claim 5, characterized in that: The average diameter of the first fiber is greater than the average diameter of the second fiber, which has an average diameter of 30-75 nm.

7. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The PMI of the pre-filter layer has an average pore size of 50-200 nm and a porosity of 75-93%; the thickness of the pre-filter layer accounts for 70%-90% of the membrane thickness.

8. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The separation layer has an average pore size of 15-25 nm, a porosity of 60-80%, and a thickness of 2-20 μm.

9. The asymmetric polyethersulfone filter membrane for virus removal according to claim 5, characterized in that: The pre-filter layer also includes a transition zone located on the side of the pre-filter layer near the separation layer. The continuous fibers form a porous structure in the transition zone, and the continuous fibers gradually change from a sheet-like structure to a strip-like structure. The side of the continuous fibers near the separation layer is continuous with the side of the second fiber near the pre-filter layer.

10. The asymmetric polyethersulfone filter membrane for virus removal according to claim 9, characterized in that: The average pore size of the transition region is 60-170 nm, and the porosity is 75%-82%; the thickness of the transition region is 4-20 μm.

11. The asymmetric polyethersulfone filter membrane for virus removal according to claim 1, characterized in that: The polyethersulfone filter membrane has a tensile strength of 6-12 MPa and an elongation at break of 8-30%. The flux of the polyethersulfone filter membrane is greater than 600 L*h -1 *m -2 @30psi; The protein yield of the polyethersulfone filter membrane is not less than 98%.

12. A method for preparing an asymmetric polyethersulfone filter membrane for virus removal according to any one of claims 1-11, characterized in that: Includes the following steps: S1: Prepare a casting solution and cast it onto a carrier to form a liquid film; the casting solution comprises the following components by weight: 15-30 parts polyethersulfone; 50-80 parts organic solvent; 3-10 parts hydrophilic additive; the viscosity of the casting solution is at least greater than 8000 cps; S2: Immerse the liquid film along with the carrier into the curing liquid for at least 20 seconds. The curing liquid penetrates into the interior of the liquid film and gradually diffuses inward, thereby solidifying to form a separation layer and a pre-filter layer. The cloud point of the casting liquid is at least 5°C higher than the temperature of the coagulation bath, and the cloud point of the casting liquid is greater than 25°C.

13. The method for preparing an asymmetric polyethersulfone filter membrane for virus removal according to claim 12, characterized in that, The organic solvent is at least one selected from butyl lactate, dimethyl sulfoxide, dimethylformamide, caprolactam, methyl acetate, ethyl acetate, N-ethylpyrrolidone, dimethylacetamide, and N-methylpyrrolidone. The hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2-[[tris(hydroxymethyl)methyl]amino]ethanesulfonic acid and 3-aminothiophene-2-carboxamide in a mass ratio of 4:1:1; The thickness of the liquid film is at least greater than 200 μm.

14. The method for preparing an asymmetric polyethersulfone filter membrane for virus removal according to claim 12, characterized in that, The coagulation bath comprises water, and the temperature of the coagulation bath is 20-50℃; the cloud point temperature of the casting solution is 30-60℃.

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