CN113856495A

CN113856495A - Asymmetric polyether sulfone filter membrane for virus removal and preparation method thereof

Info

Publication number: CN113856495A
Application number: CN202111098570.5A
Authority: CN
Inventors: 贾建东; 卢红星
Original assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Current assignee: Hangzhou Cobetter Filtration Equipment Co Ltd
Priority date: 2021-09-18
Filing date: 2021-09-18
Publication date: 2021-12-31

Abstract

The invention provides an asymmetric polyether sulfone filter membrane for virus removal and a preparation method thereof, wherein the filter membrane comprises a main body, one side surface of the main body is a first porous outer surface, the other side surface of the main body is a second porous outer surface, the average pore diameter of the first porous outer surface is 150-450nm, and the pore area rate is smaller and is 0.10-2%; the average pore diameter of the second porous outer surface is 10-40nm, and the pore area is larger by 2.1% -10%; the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering 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-filtering layer and the other side of the separating layer are transited by continuous fibers; the polyether sulfone filter membrane is prepared by only one casting membrane liquid, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the filter membrane has stronger retention effect on parvovirus with the particle size of 20nm and above; and the filter membrane has higher mechanical strength, is easy to carry out various processing treatments, and meets the requirements of practical application.

Description

Asymmetric polyether sulfone filter membrane for virus removal and preparation method thereof

Technical Field

The invention relates to the technical field of membrane materials, in particular to an asymmetric polyether sulfone filter membrane for virus removal and a preparation method thereof.

Background

In recent years, in addition to human blood-derived plasma fractionation preparations, countermeasures for improving virus safety are also required for biopharmaceuticals; therefore, pharmaceutical manufacturers have studied the introduction of a virus removal/inactivation step into the manufacturing process; a virus removal method in which filtration is performed using a virus removal filter is an effective method for reducing viruses while not denaturing useful proteins.

In the field of plasma fractionation preparations, cases of human infection due to parvovirus B19 are endless; in the field of biological medicine, cases of pollution of Chinese Hamster Ovary (CHO, Chinese Hamster Ovary) cells by mouse parvovirus also occur; this is because parvovirus has no envelope, is physically and chemically stable, and is resistant to heat, low pH, and chemical treatment, which are inactivation steps generally performed in the production process of pharmaceuticals. Therefore, as a method for removing viruses having a different action mechanism from that of the inactivation method, there is an increasing demand for removing parvoviruses by using a virus-removing membrane.

For example, chinese patent CN1759924B (EMD millipore applications) discloses a multilayer composite ultrafiltration membrane comprising (as in fig. 10) at least one first porous membrane layer having a first face and an equivalent second face, and at least one second porous membrane layer having an equivalent first face and second face, the first layer being superimposed with a junction of the second layers and having a porosity junction transition region from the equivalent first face of the second layer to the equivalent second face of the first layer, wherein at least one of the layers is an asymmetric ultrafiltration membrane; the membrane structure formed by compounding has stronger interception effect on parvovirus, and can obtain higher protein yield, thereby meeting the requirements of practical application.

However, the composite ultrafiltration membrane can be made using at least two different membrane casting solutions by co-casting two solutions using a slot die coater (e.g., fig. 11), adjusting the cast thickness of the first polymer solution to the appropriate thickness, and the cast thickness of the second polymer solution to a final layer thickness of 15 microns or about 10% of the total membrane thickness, under conditions selected so that the first solution is rapidly heated above the cloud point on the casting drum before immersion in a water bath at 55 ℃, while the second solution has not yet reached its cloud point; such that the first polymer solution forms a microporous layer and the second polymer solution forms an ultrafiltration layer; the preparation of various membrane casting solutions is relatively complicated, the composite process is complex, and the economic cost is high, so that the development of virus removal membranes is limited to a certain extent.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide an asymmetric polyether sulfone filter membrane for virus removal and a preparation method thereof, wherein the polyether sulfone filter membrane is prepared by only one casting membrane liquid, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the prepared polyether sulfone filter membrane has a strong virus interception effect; the filter membrane has higher mechanical strength, and meets the requirements of practical application;

in order to achieve the purpose, the invention provides the following technical scheme: an asymmetric polyethersulfone filter membrane for virus removal comprises a main body, wherein a non-directional tortuous passage is formed in the main body, one side surface of the main body is a first porous outer surface, the other side surface of the main body is a second porous outer surface, the average pore diameter of the first porous outer surface is 150-450nm, and the average pore diameter of the second porous outer surface is 10-40 nm;

the area ratio of the holes on the first porous outer surface is 0.10% -2%, and the area ratio of the holes on the second porous outer surface is 2.1% -10%; the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering 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-filtering layer and the other side of the separating layer are transited by continuous fibers; for colloidal gold with a particle size of 20nm, the LRV of the filter membrane is not lower than 4.

In the membrane main body structure of the polyether sulfone filter membrane provided by the invention, the pore diameters of holes on two outer surfaces of the filter membrane are different and have a certain difference; the pore diameter of the pores on one outer surface is larger, the outer surface with the larger pore diameter is called as a first porous outer surface in the invention, namely the first porous outer surface is a large pore surface of the filter membrane, the average pore diameter of the first porous outer surface is 150-450nm, preferably, the average pore diameter of the first porous outer surface is 200-400nm, and the existence of the large pore surface is beneficial to improving the integral filtering speed of the membrane, so that the fluid filtering time is shorter and the time cost is lower;

the pores on the other outer surface of the filter membrane have smaller pore diameters, the outer surface with the smaller pore diameters is called a second porous outer surface in the invention, namely the second porous outer surface is a small pore surface of the filter membrane, the average pore diameter of the second porous outer surface is 10-40nm, and preferably, the average pore diameter of the second porous outer surface is 15-35 nm; the existence of the small pore surface is beneficial to improving the filtration precision of the membrane, and ensures that the polyether sulfone filter membrane has higher retention effect on parvovirus; the average pore size of the first porous outer surface and the average pore size of the second porous outer surface are different and have a certain difference, which indicates that the polyethersulfone filter membrane is an asymmetric membrane, so that the integral membrane has higher filtration speed, larger pollutant carrying capacity and longer service life; but also can ensure that the parvovirus (particularly the parvovirus with the grain diameter of about 20 nm) has stronger trapping capacity and meets the requirement of practical application;

it is known that factors such as the pore size and the number of pores of the membrane, the shape of the pores and the like can greatly influence the properties such as the filtration precision (interception efficiency) and the flow rate of the membrane; generally, in an asymmetric filter membrane, the hole area ratio (hole area/corresponding membrane area) of a large hole surface is greater than that of a small hole surface (the larger the hole diameter, the larger the hole area ratio under the condition that the number of holes is basically the same); the polyethersulfone filter membrane is opposite, the pore area rate of the large pore surface (the first porous outer surface) is smaller than that of the small pore surface (the second porous outer surface), and both outer surfaces have proper pore area rates, so that the polyethersulfone filter membrane has larger flow velocity, is convenient for fluid to rapidly pass through the porous membrane, shortens the filtration time, and also has larger mechanical strength, large tensile strength, high industrial value and long service life;

by observing the structure of the main body of the membrane, the whole main body of the filter membrane is mainly divided into two areas in the thickness direction, wherein one area is a pre-filtering layer comprising a first porous outer surface, the pore diameter of the inner pores of the pre-filtering layer is relatively large and is mainly used for intercepting large-particle impurities in fluid, and the pre-filtering layer has large dirt holding capacity and high flow speed; and can provide support and protection for the separation layer; the other area is a separation layer containing a second porous outer surface, the pore diameter of the inner pores is relatively small, and the separation layer is mainly used for intercepting fine particle impurities such as parvovirus in protein, so that the filter membrane has high virus trapping capacity, and the polyether sulfone filter membrane is particularly suitable for being used as a virus removal membrane;

further, the other side of the pre-filter layer (the side of the pre-filter 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 being understood that "continuous" means that substantially all of the fibers are integrally connected to each other, e.g., integrally formed, without the need for additional bonding agents or the like to connect them to each other, and the fibers in the network are not separable from each other unless torn by an external force; at the same time, the continuous network-like fibers are interconnected with the first porous outer surface and the second porous surface; the materials of all parts of the polyether sulfone filter membrane are uniform, namely the whole membrane is made of polyether sulfone materials, and no change exists in the materials; the polyether sulfone filter membrane is proved to be integrally formed without processes such as compounding and the like;

the virus trapped by the invention mainly aims at various viruses with the particle size of 20nm and above (such as mouse parvovirus, the particle size of which is about 20 nm); by using colloid with the particle size of 20nm as the trapping effect,

after interception test, the LRV is not lower than 4, which shows that the polyethersulfone filter membrane has very high interception rate to virus, plays a role in sufficiently retaining virus impurities and meets the requirement of practical application; in addition, for the test method of virus impurities, reference may be made to patent-CN 105980037B-membrane for virus removal, CN 101816898B-ultrafiltration membrane and preparation method thereof, CN 1759924B-ultrafiltration membrane and preparation method thereof, and the like.

In the context of the present invention, an asymmetric membrane is understood to be a membrane in which the prefiltration layer and the separation layer are both composed of the same material, the two layers being joined to form a unitary structure and being formed directly during the membrane preparation process; in the transition from the prefilter layer to the separation layer, there is only a change in the membrane structure; in contrast, for example, composite membranes, which have a multilayer structure and in which a dense layer as a separating layer is applied in a separate process step to a porous, frequently microporous, support layer or support membrane, the materials of which the support layer and the separating layer are composed often also being different;

the measurement mode of the average pore diameter of the membrane surface can be realized by performing morphology characterization on a membrane structure by using a scanning electron microscope, then performing measurement by using computer software (such as Matlab, NIS-Elements and the like) or manually, and performing corresponding calculation; in the production of the membrane, various characteristics such as the pore size distribution in the direction perpendicular to the thickness of the membrane (the direction is a planar direction if the membrane is in the form of a flat sheet membrane; the direction is perpendicular to the radial direction if the membrane is in the form of a hollow fiber membrane) are substantially uniform and substantially uniform; the average pore size of the whole of the plane can be reflected by the average pore size of a partial region on the corresponding plane. In practice, the surface of the membrane can be characterized by an electron microscope to obtain a corresponding SEM image, and since the pores on the surface of the membrane are substantially uniform, a certain area, such as 1 μm, can be selected²(1 μm by 1 μm) or 25 μm²(5 μm multiplied by 5 μm), the specific area size is determined according to the actual situation, the pore diameters of all pores on the area are measured by corresponding computer software or manually, and then the average pore diameter of the surface is obtained by calculation; of course, the skilled person can also obtain the above parameters by other measuring means, which are only used as reference.

As a further improvement of the invention, the first porous outer surface is provided with a plurality of first holes in a circular hole shape; the second porous outer surface is provided with a plurality of second round-hole-shaped holes; the difference between the area ratio of the holes on the second outer surface and the area ratio of the holes on the first outer surface is greater than 1.5%.

In the membrane body structure of the polyether sulfone filter membrane provided by the invention, a certain number of first holes with certain pore diameters are clearly seen on the first porous outer surface of the membrane, and the factors such as the pore diameter size, the number and the shape of the holes of the membrane can generate great influence on the properties such as the filtration precision (interception efficiency) and the membrane flow rate of the membrane; according to the invention, the first holes on the outer surface of the first porous body are of a circular hole-shaped structure, some first holes are circular, and some first holes are oval; meanwhile, a certain number of second holes with certain pore diameters exist on the second porous outer surface of the membrane, and the second holes on the second porous outer surface are also in a circular hole-shaped structure, some second holes are circular, and some second holes are oval; the first hole and the second hole in the shape of round holes are easier to intercept viruses; in addition, the difference between the area rate of the second holes on the second outer surface and the area rate of the first holes on the first outer surface (the value obtained by subtracting the area rate of the first holes on the first outer surface from the area rate of the second holes on the second outer surface) is more than 1.5 percent, namely, the number of the second holes on the small hole surface (the second porous outer surface) is larger, and the number of the first holes on the large hole surface (the first porous outer surface) is smaller, so that the difference of the area rates of the holes further ensures that the whole membrane has higher tensile strength and elongation at break, and is suitable for various processing treatments; and also enables the filter membrane to have larger flux, and can rapidly and efficiently filter various fluids.

As a further development of the invention, the pre-filter layer comprises a skin region and a pre-filter region, the skin region being located on the side of the pre-filter layer facing away from the separation layer, the side of the skin region comprising the first porous outer surface, the skin region having a thickness of 0.3 to 3.2 μm.

In the bulk structure of the filter membrane of the invention, we have found that there is a region within the pre-filter layer where there are fewer pores and very low porosity, this region we call the skin zone region, which is located on the side of the pre-filter layer facing away from the separation layer; the largest characteristic of the skin region is that the number of holes is small, and the porosity of the region is low; the surface of the leather layer region, which is far away from the separation layer, is a first porous outer surface, the number of first holes on the first porous outer surface is small, and although the average pore diameter of the first holes is still larger, the hole area rate of the first holes on the first porous outer surface is smaller than the hole area rate of the second holes on the second porous outer surface; the existence of the skin layer region is beneficial to improving the tensile strength of the membrane, and simultaneously provides a supporting and protecting function for the separating layer, so that the whole membrane is more pressure-resistant, is not easy to crack and has longer service life; in addition, the measurement shows that the thickness of the skin layer region is 0.3-3.2 μm, and the thickness is smaller, so that the supporting strength of the membrane can be improved, and the integral filtering speed and pollutant carrying capacity of the membrane can be avoided.

As a further improvement of the invention, the PMI average pore diameter of the filter membrane is 15-25nm, the thickness of the filter membrane is 50-150 μm, and the porosity is 70-85%.

The average pore size of the filter membrane is tested by a PMI pore size tester, the PMI average pore size of the filter membrane obtained after the test is 15-25nm, and the polyether sulfone filter membrane has a strong interception effect on nano-scale parvovirus (even the murine parvovirus with the particle size of 20 nm) under the synergistic effect of a tortuous path of a membrane main body structure and a certain thickness of the membrane, can meet the requirement of practical application, and is suitable for being used as a virus membrane;

the thickness of the film can be measured by using a scanning electron microscope to perform morphology characterization on the film structure, and then using computer software (such as Matlab, NIS-Elements and the like) or manually measuring and then calculating; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference; when the thickness of the film is too small, the mechanical strength of the film is low; meanwhile, as the filtering time is too short, effective filtering cannot be carried out; when the thickness of the membrane is too large, the filtration time is too long, and the time cost is too large; the thickness of the polyethersulfone filter membrane is 50-150 mu m, so that the polyethersulfone filter membrane has high mechanical strength, can be effectively filtered, and has high filtering efficiency, short filtering time and low time cost;

when the porosity of the membrane is too high, the tensile strength of the membrane is too low, the mechanical property of the membrane is poor, the industrial practical value is low, and the market demand cannot be met; when the porosity of the membrane is too low, on one hand, the flow rate of the membrane is influenced, so that the filtering speed of the membrane is low, the filtering time is long, and the time cost is high; on the other hand, the pollution capacity of the membrane is too low, the service life is too short, the membrane needs to be replaced in a short time, and the economic cost is greatly improved; the porosity of the porous membrane is 70-85%, so that the membrane not only has good tensile strength, but also has high filtering speed, high flow rate, high pollutant carrying capacity, long service life and low economic cost, and can retain more impurity particles.

As a further improvement of the invention, the average pore diameter variation gradient of the filter membrane is 1.5-6 μm/1 μm; 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 to 23.

In the invention, the aperture size of the holes of the filter membrane is changed in a gradient way along with the thickness, the aperture is gradually reduced from a large aperture surface to a small aperture surface; the ratio of the average pore sizes of the two outer surfaces can be called an asymmetry factor, and the smaller the value is (the closer to 1), the stronger the symmetry of the two outer surfaces of the filter membrane is; the larger the value, the larger the asymmetry of the two outer surfaces of the filter membrane; the measurement shows 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, preferably 10-20, which indicates that the two outer surfaces of the polyethersulfone filter membrane are asymmetric but not highly asymmetric; the asymmetric structure not only ensures that the filter membrane has larger flux and longer service life; the high virus interception efficiency of the filter membrane is ensured, and the actual requirement is met;

because the pore size of the polyethersulfone filter membrane changes along with the gradient of the membrane thickness, the invention reflects the speed of the change of the membrane pore size along with the thickness through the size of the average pore size change gradient, the larger the value of the change is, the faster the pore size change is, the smaller the value is, the smaller the pore size change is; the value can be obtained by (average pore diameter of the first porous outer surface-average pore diameter of the second porous outer surface)/thickness, so the unit is mum (representative pore diameter)/1μm (representative thickness), the average pore diameter change gradient of the filter membrane is 1.5-6μm/1μm, the change gradient value is smaller, which shows that the pore diameter of the filter membrane changes along with the thickness in small gradient, the pore diameter of the filter membrane does not change too fast, and no overlarge pores exist (if overlarge pores exist, the filter membrane does not resist pressure, the filter membrane is easy to break under the action of pressure, and the service life is short), thereby the high-efficiency interception of the membrane to virus can be ensured, the filter membrane has faster flux and larger pollutant carrying capacity can be ensured; in addition, the pre-filtering layer of the filter membrane can provide supporting and protecting functions for the separating layer, and the integral mechanical strength of the membrane is improved.

As a further improvement of the present invention, the pre-filter layer comprises first fibers forming a porous structure, the first fibers being a sheet-like structure; the separation layer comprises second fibers forming a porous structure, and the second fibers are in a strip-shaped structure.

In the membrane body structure of the PES filter membrane provided by the invention, the fiber structure can be clearly seen to be changed along with the membrane thickness, the first fibers in the pre-filter layer are of a sheet structure, and the second fibers in the separation layer are of a strip structure; the pre-filtering layer formed by the first fibers of the flaky structure is more stable and pressure-resistant, and can play a certain supporting and protecting role on the separation layer, and the distribution of the flaky fiber structure can help fluid diffusion and improve the interception effect of the small holes; and the separation layer formed by the second fibers with the strip-shaped structures has proper porosity and pore distribution, so that the whole membrane has higher flow rate, and meanwhile, the virus interception efficiency is high.

As a further development of the invention, the average diameter of the first fibers is greater than the average diameter of the second fibers, the average diameter of the second fibers being between 30 and 75 nm.

The average diameter of the first fibers is larger than that of the second fibers, because the holes of the pre-filtering layer are relatively large, the holes formed by the thick first fibers have high stability and are not easy to collapse or shrink, and the stability of the flow rate of the fluid is further ensured; in addition, the average diameter of the second fibers is 30-75nm, so that the stability of holes in the separation layer is ensured, and the parvovirus impurities can be well retained; with the structure, the thick and thin first fibers and the thin and thick second fibers are beneficial to ensuring that the whole membrane has higher mechanical strength and filtration stability, and can be efficiently filtered for a long time; therefore, the PES filter membrane is particularly suitable for being applied to the field of virus removal;

the thickness degree of the fiber section can be regarded as the diameter of the fiber, and the average diameter of the second fiber in the invention can be calculated by using a scanning electron microscope to perform morphology characterization on the cross-sectional structure of the filter membrane and then using computer software (such as Matlab, NIS-Elements and the like) or manually to perform measurement; it will of course be appreciated that the above parameters may also be obtained by other measurement means by a person skilled in the art.

As a further improvement of the invention, the PMI average pore diameter of the pre-filtering layer is 50-200nm, and the porosity is 75-93%; the thickness of the prefilter layer accounts for 70-90% of the thickness of the membrane.

Compared with the separation layer, the pore diameter of the hole of the pre-filtering layer is larger, and the integral porosity is also larger; tests show that the PMI average pore size of the pre-filtering layer is 50-200nm (preferably 60-180nm), so that the filter membrane has high flow velocity, and can also play a sufficient role in intercepting large-particle impurities (large-particle-size viruses) without influencing the interception of subsequent parvoviruses; no extra large holes exist, the pre-filtering layer is ensured to provide a supporting and protecting function for the separating layer, and the separating layer can efficiently capture viruses for a long time; meanwhile, the membrane is integrally pressure-resistant, is not easy to break under the action of pressure and has long service life; the thickness of the pre-filtering layer accounts for 70-90% of the whole thickness of the membrane, which shows that most areas of the membrane are the pre-filtering layer, and under the combined action of large aperture and high porosity (the porosity of the pre-filtering layer is 75-93%), the whole membrane is ensured to have higher flux, high filtering speed, low time cost, higher dirt receiving capacity and long service life.

The PMI average pore diameter, porosity, thickness and other parameters of the pre-filtering layer can be divided into a separating layer and the pre-filtering layer by tearing the polyether sulfone filtering membrane, and then the pre-filtering layer is subjected to corresponding parameter test; or the film cross-sectional structure is subjected to morphology characterization by using a scanning electron microscope, and then is measured and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually; of course, the skilled person can also obtain the above parameters by other measuring means, and the above measuring means is only used for reference;

as a further improvement of the invention, the average pore diameter of the separating layer is 15-25nm, the porosity is 60-80%, and the thickness of the separating layer is 2-20 μm.

Compared with a pre-filtering layer, the pore diameter of the pores of the separating layer is smaller, and the average pore diameter (PMI average pore diameter) of the separating layer is 15-25nm, so that the polyether sulfone filtering membrane has higher interception efficiency on impurities with small particle size (particularly parvoviruses with the particle size of 20 nm), the requirement of practical application is met, and the polyether sulfone filtering membrane is particularly suitable for being applied to the field of virus removal;

the thickness of the separation layer is 2-20 μm, so that the impurity interception efficiency is ensured, the integral membrane is further ensured to have higher flux, the filtration speed is high, and the time cost is low; meanwhile, the porosity of the separation layer is 60-80%, which shows that the separation layer can play a sufficient role in retaining parvovirus, and the service life of the membrane is further prolonged;

the parameters of the separating layer such as average pore diameter, porosity, thickness and the like can be obtained by tearing the polyether sulfone filter membrane, dividing the polyether sulfone filter membrane into the separating layer and the pre-filtering layer, and then carrying out corresponding parameter test on the separating layer; or the film cross-sectional structure is subjected to morphology characterization by using a scanning electron microscope, and then is measured and measured by using computer software (such as Matlab, NIS-Elements and the like) or manually; in addition, the thickness of the separation layer can also be subjected to interception test by using 20nm colloidal gold as impurity particles, the length of a 20nm colloidal gold interception area in the filter membrane is the thickness of the separation layer, and the specific test method can refer to Chinese patent CN 105980037B-membrane for removing viruses; of course, the skilled person can also obtain the above parameters by other measuring means, which are only used as reference.

As a further improvement of the invention, the pre-filter layer further comprises a transition region, the transition region is positioned on one side of the pre-filter layer close to the separation layer, the continuous fibers form a porous structure of the transition region, and the continuous fibers gradually change from a sheet structure to a strip structure; one side of the continuous fibers adjacent the separation layer is continuous with one side of the second fibers adjacent the pre-filter layer.

As a further improvement of the invention, the average pore diameter of the transition region is 60-170nm, and the porosity is 75% -82%; the thickness of the transition zone is 4-20 μm.

The membrane pore size, the fiber structure and other characteristics of the polyether sulfone filter membrane are gradually changed along with the thickness instead of mutation, so that the integral membrane has high mechanical strength, the tensile strength is high, and the requirements of practical application can be met; a transition area is arranged on one side of the pre-filtering layer close to the separating layer, and continuous fibers in the transition area form a porous structure of the transition area, so that pores with proper pore sizes and excellent porosity in the transition area are ensured; in the direction of the pre-filtering layer facing the separating layer, the continuous fibers gradually change from the sheet structure to the strip structure; meanwhile, the side of the continuous fibers adjacent to the separation layer is continuous with the side of the second fibers adjacent to the pre-filter layer, and "continuous" means that substantially all of the fibers (continuous fibers and second fibers) are integrally connected to each other, e.g., integrally formed, without being connected to each other using an additional adhesive or the like, and the network-like fibers cannot be separated from each other unless torn by an external force; thus also showing that the materials of all parts of the polyethersulfone filter membrane are uniform, namely the whole membrane is made of polyethersulfone materials and is integrally formed, and no change exists in the materials; the average pore diameter of the transition zone is 60-170nm, and the porosity is 75% -82%; the thickness of the transition zone is 4-20 μm, and under the combined action of the three, the filter membrane is further ensured to have higher trapping capacity for various viruses, and has the advantages of higher flux, high filtering speed and high economic benefit.

As a further improvement of the invention, the tensile strength of the polyethersulfone filter membrane is 6-12MPa, and the elongation at break is 8-30%; the flux of the polyether sulfone filter membrane is more than 600L x h^-1*m^-2@30 psi; the protein yield of the polyether sulfone filter membrane is not lower than 98%.

Important indexes for evaluating the mechanical strength of the filter membrane are the tensile strength and the elongation at break of the filter membrane; under certain conditions, the higher the tensile strength of the filter membrane is, the better the mechanical strength of the filter membrane is; tensile strength refers to the ability of a film to withstand parallel stretching; when the film is tested under a certain condition, the film sample is acted by a tensile load until the film sample is damaged, and the tensile strength and the elongation at break of the film can be calculated according to the maximum tensile load corresponding to the damage of the film sample, the change of the size (length) of the film sample and the like; tensile strength, elongation at break, can be measured by a universal tensile tester, tensile strength testing methods are well known in the art, for example, tensile strength testing procedures are explained in detail in ASTM D790 or ISO 178; the tensile strength of the filter membrane is 6-12 MPa; the elongation at break is 8-30%, which shows that the filter membrane of the invention has larger tensile strength and elongation at break, better mechanical property and higher industrial practical value, and can completely meet the market demand.

The permeation flux is also called the permeation rate, flux for short, and refers to the amount of substance that a filter membrane passes through the unit membrane area in a unit time under a certain working pressure in the separation process; the flux reflects the speed of the filtration; the higher the flux, the faster the filtration rate of the membrane; the flux of the polyether sulfone filter membrane is more than 600L x h^-1*m^-2@30psi, its flux is great, indicates that the filtration rate of filter membrane is faster, when guaranteeing to hold back efficiency, and the fluid can rapid through filtration membrane, and the time cost is lower, and economic benefits is higher.

The protein yield of the polyether sulfone filter membrane is not lower than 98%, which indicates that the effective substance protein in the fluid is not easy to be adsorbed on the membrane, on one hand, the membrane pores are not blocked, and the filter membrane still has longer service life, on the other hand, the content change of the effective substance protein in the fluid is ensured to be very small, the protein is not basically lost, and the economic benefit is ensured; as a method for measuring the protein yield, reference may be made to a patent-CN 105980037B-virus-removing membrane, a CN 101816898B-ultrafiltration membrane and a method for producing the same, a CN 1759924B-ultrafiltration membrane and a method for producing the same, and the like.

On the other hand, the invention also provides a preparation method of the asymmetric polyether sulfone filter membrane for virus removal, which comprises the following steps:

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 15-30 parts of polyether sulfone; 50-80 parts of an organic solvent; 3-10 parts of hydrophilic additive; the viscosity of the casting solution is at least 8000 cps;

s2: immersing the liquid film together with the carrier into the curing liquid for at least 20 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the cloud point of the casting solution is at least 5 ℃ higher than the temperature of the coagulation bath, and the cloud point of the casting solution is higher than 25 ℃.

As a further improvement of the present invention, the organic solvent is at least one of 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-formamide in a mass ratio of 4: 1; 1; the thickness of the liquid film is at least greater than 200 um.

As a further improvement of the invention, 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 ℃.

The preparation method of the polyether sulfone filter membrane comprises the steps of firstly preparing a membrane casting solution, wherein the membrane casting solution comprises a membrane forming substance polyether sulfone (polyether sulfone), an organic solvent (used for solvent polyether sulfone materials) and a hydrophilic additive; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2- [ [ tri (hydroxymethyl) methyl ] amino ] ethanesulfonic acid and 3-aminothiophene-2-formamide, and the polyvinylpyrrolidone can effectively control the viscosity of the system, inhibit the liquid membrane from forming macropores in the phase separation process and effectively improve the stability of membrane flux; under the synergistic effect of the three substances, the hydrophilicity of the surface of the filter membrane can be effectively improved (so that the protein yield is improved, and the service life of the filter membrane is prolonged), and the membrane pore structure can be optimized, so that an ideal membrane structure can be obtained; the viscosity of the casting film liquid can have great influence on the structure and the performance of the finally formed filter membrane, such as the pore diameter, the thickness, the flow rate and the like of the filter membrane; such viscosity setting ensures that the finally prepared filter membrane has proper thickness and obtains ideal pore diameter; the viscosity of the casting solution can be directly obtained by a viscometer; the viscosity of the casting solution is larger than 8000cps (but the viscosity cannot be too high and cannot be higher than 15000cps), and the higher the viscosity is, the slower the phase separation speed is; the viscosity is favorable for forming a membrane body structure with a large pore surface, a low pore area rate and a small pore surface and a high pore area rate; then, casting the casting solution on a carrier to form a liquid film; the casting solutions of the present invention may be cast manually (e.g., by pouring, casting, or spreading by hand on a casting surface) or automatically (e.g., poured or otherwise cast on a moving bed); a variety of apparatus known in the art can be used for casting. Casting equipment includes, for example, mechanical coaters, including doctor blades, or spray/pressurized systems. As is known in the art, a variety of casting speeds are suitable, such as casting speeds of about 1 to 5 feet per minute (fpm), and the like, as the case may be; preferably, the thickness of the liquid film is at least more than 200um, which is to ensure that the thickness after film formation is more than 30um, so that the whole film has higher mechanical strength, is suitable for various industrial processing treatments and has high industrial practical value; the thickness of the liquid film is larger, so that longer phase separation time is required, and a skin layer structure appears, namely, the area rate of holes of the large pore surface of the film is lower;

then the liquid film is immersed into the curing liquid along with the carrier for at least 20 seconds, the phase-splitting curing time is preferably 30-70 seconds, and the proper phase-splitting curing time can be beneficial to obtaining a filter membrane with an ideal membrane aperture size under the combined action of the liquid film casting system; the curing liquid can invade into the liquid film and gradually diffuse inwards, and then the curing liquid is cured to form a separation layer and a pre-filtering layer; the curing liquid contains water, and preferably, the curing liquid can also comprise a weak solvent, the weak solvent is any one of pentanol, hexanol, heptanol, octanol, hexane, propane, heptane and octane, the existence of the weak solvent is more favorable for obtaining a perfect membrane structure, and the integral phase separation speed is relatively slow, so that a skin layer structure is formed; the key points of the filter membrane preparation method are that the cloud point of the casting membrane liquid is at least 5 ℃ higher than the temperature of the coagulation bath, and the cloud point of the casting membrane liquid is more than 25 ℃ (the cloud point of the casting membrane liquid is the point where solids are precipitated at first); the preferable coagulating bath temperature is 20-50 ℃; the cloud point temperature of the casting solution is 30-60 ℃; the cloud point temperature of the casting solution is higher, the phase splitting speed of the whole casting solution is slow, and the phase splitting is delayed, so that the casting solution is skinned; the influence factors of phase separation caused by the internal non-solvent are weakened, the influence factors of phase separation caused by thermodynamic temperature change are increased, a lower aperture ratio at the bottom is formed, and the strength is improved; the polyethersulfone filter membrane is prepared by the preparation method, is prepared by only one casting membrane liquid, is integrally formed, does not need to be compounded, and has a relatively simple preparation process; meanwhile, the prepared polyether sulfone filter membrane has a strong virus interception effect and a high protein yield; the filter membrane has higher mechanical strength, and meets the requirements of practical application; therefore, the polyethersulfone filter membrane is particularly suitable for being used for removing virus membranes.

The invention has the beneficial effects that: the asymmetric polyether sulfone filter membrane for virus removal comprises a main body, wherein a non-directional tortuous passage is arranged in the main body, one side surface of the main body is a first porous outer surface, the first porous outer surface is a macroporous surface, the average pore diameter of the porous polyether filter membrane is 150-450nm, and the pore area rate is 0.10-2%; the other side surface of the main body is a second porous outer surface which is a small pore surface, the average pore diameter of the second porous outer surface is 10-40nm, and the area rate of the pores is 2.1% -10%; the membrane structure of the large pore surface area rate and the large pore surface rate of the small pore surface ensures that the filter membrane not only has high flux, but also can effectively and quickly filter; the film is ensured to have higher tensile strength and high stability; the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering 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-filtering layer and the other side of the separating layer are transited by continuous fibers; the polyether sulfone filter membrane is integrally prepared and formed only by one membrane casting solution without compounding, and the preparation process is relatively simple; meanwhile, the prepared polyether sulfone filter membrane has a strong interception effect on parvovirus, and can obtain high protein yield, so that the requirement of practical application is met; is particularly suitable for the field of virus removal; in addition, the invention also provides a preparation method of the filter membrane, and the preparation method is convenient, quick and effective, simple to operate, green and environment-friendly, and suitable for large-scale popularization.

Drawings

FIG. 1 is a Scanning Electron Microscope (SEM) image of a first outer surface of a PES filter membrane obtained by preparation of example 1, at 1000 magnification;

FIG. 2 is a further magnified Scanning Electron Microscope (SEM) image of the first outer surface of the PES filter membrane obtained in example 1, at a magnification of 5000 ×;

FIG. 3 is a Scanning Electron Microscope (SEM) image of the second outer surface of the PES filter membrane obtained by preparation of example 1, at a magnification of 10K ×;

FIG. 4 is a further magnified Scanning Electron Microscope (SEM) image of the second outer surface of the PES filter membrane obtained in example 1 at a magnification of 20K ×;

FIG. 5 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES filter membrane prepared in example 1, wherein the magnification is 500;

FIG. 6 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES filter membrane prepared in example 1, at a magnification of 20K ×;

FIG. 7 is a Scanning Electron Microscope (SEM) image of a longitudinal section of a PES filter membrane prepared in example 1, taken near the first outer surface, at a magnification of 10K ×;

FIG. 8 is a schematic diagram of a flux testing device for polyethersulfone filter membranes according to the present invention;

FIG. 9 is a schematic diagram of a testing device for testing the rejection efficiency of colloidal gold for a polyethersulfone filter membrane according to the invention;

FIG. 10 is a Scanning Electron Microscope (SEM) image of the cross section of a multi-layer composite ultrafiltration membrane prepared in patent CN 1759924B;

FIG. 11 is a schematic diagram of a compounding device in the preparation of a multi-layer composite ultrafiltration membrane according to patent CN 1759924B.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following examples, raw materials and equipment for preparing the filtration membranes were commercially available, unless otherwise specified. Wherein the structural morphology of the filter membrane is characterized by adopting a scanning electron microscope with the model number of S-5500 provided by Hitachi company.

Example 1

A preparation method of an asymmetric polyethersulfone filter membrane for virus removal comprises the following steps:

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 23 parts of polyether sulfone; 65 parts of an organic solvent; 6 parts of a 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-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 45 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the coagulating bath is water, and the temperature of the coagulating bath is 30 ℃; the cloud point temperature of the casting solution is 40 ℃.

Example 2

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 25 parts of polyether sulfone; 68 parts of an organic solvent; 7 parts of a 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-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 50 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the coagulating bath is water, and the temperature of the coagulating bath is 35 ℃; the cloud point temperature of the casting solution was 45 ℃.

Example 3

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 27 parts of polyether sulfone; 71 parts of an organic solvent; 8 parts of a 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-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 55 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the coagulating bath comprises water and octanol, the volume of the octanol accounts for 8% of the total volume of the coagulating bath, and the temperature of the coagulating bath is 37 ℃; the cloud point temperature of the casting solution was 51 ℃.

Example 4

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 29 parts of polyether sulfone; 74 parts of an organic solvent; 9 parts of a hydrophilic additive; the organic solvent is ethyl acetate; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2- [ [ tris (hydroxymethyl) methyl ] amino ] ethanesulfonic acid and 3-aminothiophene-2-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 60 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the coagulating bath comprises water and pentane, the volume of the pentane accounts for 13% of the total volume of the coagulating bath, and the temperature of the coagulating bath is 40 ℃; the cloud point temperature of the casting solution was 56 ℃.

Example 5

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 20 parts of polyether sulfone; 60 parts of an organic solvent; 5 parts of a hydrophilic additive; the organic solvent is N-ethyl pyrrolidone; the hydrophilic additive comprises a mixture of polyvinylpyrrolidone, 2- [ [ tris (hydroxymethyl) methyl ] amino ] ethanesulfonic acid and 3-aminothiophene-2-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 38 seconds, wherein the curing liquid is immersed into the liquid film and gradually diffuses inwards, and then is cured to form a separation layer and a pre-filtering layer; the coagulating bath is water, and the temperature of the coagulating bath is 25 ℃; the cloud point temperature of the casting solution is 35 ℃.

Example 6

s1: preparing a casting solution, and casting the casting solution on a carrier to form a liquid film; the casting solution comprises the following substances in parts by weight: 18 parts of polyether sulfone; 55 parts of an organic solvent; 4 parts of a 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-formamide in a mass ratio of 4: 1; 1;

s2: immersing the liquid film together with the carrier into the curing liquid for 32 seconds, wherein the curing liquid invades into the liquid film and gradually diffuses inwards, and then curing to form a separation layer and a pre-filtering layer; the coagulating bath is water, and the temperature of the coagulating bath is 22 ℃; the cloud point temperature of the casting solution is 30 ℃.

Firstly, the method comprises the following steps: structural characterization

Carrying out morphology characterization on the membrane structure of the nanoscale polymer filtering membrane obtained in each embodiment by using a scanning electron microscope, and then obtaining required data; the specific results are as follows:

table 1:

table 2-polyethersulfone filter membrane body:

	thickness/mum	Porosity/%	PMI mean pore diameter/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

Table 3-separation and pre-filtration layers:

table 4-transition and cortical regions:

	thickness of transition zone/μm	Transition zone porosity/%)	Transition region PMI mean pore diameter/nm	Cortex region thickness/mum
					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

As can be seen from tables 1-4, the polyethersulfone filter membranes prepared in the embodiments 1-6 of the invention all have ideal membrane structures, and the filter membranes are integrated into a membrane, and are not subjected to a composite process, so that the process preparation is simple; the polyethersulfone filter membrane is an asymmetric membrane, the pore diameter of the membrane pore changes along with the small thickness gradient, no extra large pore exists, the high-efficiency interception of the virus is ensured, and the polyethersulfone filter membrane has higher flux, and is suitable for being applied to the field of virus removal.

Characteristic features

The membrane flux is calculated as follows:

the formula for calculating the membrane flux (J) is: j ═ V/(T × a) formula wherein:

j- -Membrane flux Unit: l H-1 m-2

V- -sample volume (L); t- -sampling time (h); a- -effective area of film (m2)

The polyethersulfone filter membrane separation performance measurement adopts the following operating conditions: the feed liquid is deionized water, the operating pressure is 30psi, the operating temperature is 25 ℃, and the pH of the solution is 7; the throughput testing device is shown in fig. 8;

	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

As can be seen from 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 treatments, and have strong industrial applicability; meanwhile, the filter has higher flux, high filtering speed and high efficiency and economic benefit.

Furthermore, the following test methods were used in accordance with CN 201010154974.7-ultrafiltration membrane and its preparation method, paragraph 114: performing a virus retention test:

the virus used is a murine parvovirus with a particle size of 20 nm;

after tests, the LRV of the polyether sulfone filter membranes prepared in the examples 1-6 on virus impurities with the particle size of 20nm is not lower than 4, so that the polyether sulfone filter membranes have sufficient retention effect on viruses with the particle size of 20nm and above; and the protein yield of the polyether sulfone filter membrane is not lower than 98 percent; therefore, the polyethersulfone filter membrane is particularly suitable for being applied to the field of virus removal.

And (3) testing the filtering precision: the polyether sulfone filter membranes obtained in the examples are subjected to interception efficiency test; intercepting particles: colloidal gold with particle size of 20nm

Experimental equipment: a Tianjin Roots particle counter KB-3; preparation of the experiment: the experimental set-up was assembled as per fig. 9, ensuring the set-up was clean, and the set-up was rinsed with ultra-pure water; and a filter membrane with the diameter of 47mm is taken and arranged in the butterfly filter, so that the air tightness of the assembled filter is ensured to be good.

The experimental steps are as follows:

the challenge was poured into a tank, the butterfly filter was vented, pressurized to 10kPa, and a clean bottle was used to take the butterfly downstream filtrate.

The number of particles in the filtrate and stock solutions was measured using a particle counter.

Intercepting efficiency:

in the formula:

eta-type-interception efficiency,%;

n₀-number of particles in stock solution, average of 5 sets of counts;

n₁-number of particles in filtrate, average of 5 groups of counts, one.

After tests, the rejection efficiency of the polyethersulfone filter membranes prepared in examples 1-6 to 20nm colloidal gold is not lower than 99.99%, which further shows that the polyethersulfone filter membranes have strong rejection effect on various viruses with the particle size of 20nm and above, and meet the requirements of practical application.

The above description is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may occur to those skilled in the art without departing from the principle of the invention, and are considered to be within the scope of the invention.

Claims

1. An asymmetric polyethersulfone filter membrane for virus removal, comprising a body having non-directional tortuous pathways therein, one surface of said body being a first porous outer surface and the other surface of said body being a second porous outer surface, wherein: the average pore diameter of the first porous outer surface is 150-450nm, and the average pore diameter of the second porous outer surface is 10-40 nm;

the area ratio of the holes on the first porous outer surface is 0.10% -2%, and the area ratio of the holes on the second porous outer surface is 2.1% -10%;

the main body comprises a pre-filtering layer and a separation layer for intercepting viruses, wherein one side of the pre-filtering 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-filtering layer and the other side of the separating layer are transited by continuous fibers;

for colloidal gold with a particle size of 20nm, the LRV of the filter membrane is not lower than 4.

2. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the outer surface of the first porous body is provided with a plurality of first holes in a circular hole shape; the second porous outer surface is provided with a plurality of second round-hole-shaped holes;

the difference between the area ratio of the holes on the second outer surface and the area ratio of the holes on the first outer surface is greater than 1.5%.

3. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the pre-filter layer comprises a skin layer region and a pre-filter region, the skin layer region is positioned on one side of the pre-filter layer, which is far away from the separation layer, one side of the skin layer region comprises a first porous outer surface, and the thickness of the skin layer region is 0.3-3.2 microns.

4. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the PMI average pore diameter of the filter membrane is 15-25nm, the thickness of the filter membrane is 50-150 mu m, and the porosity is 70-85%.

5. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the average pore diameter variation gradient of the filter membrane is 1.5-6 mu m/1 mu m; 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 to 23.

6. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the pre-filter layer comprises first fibers forming a porous structure, and the first fibers are sheet-like structures; the separation layer comprises second fibers forming a porous structure, and the second fibers are in a strip-shaped structure.

7. An asymmetric polyethersulfone filter membrane according to claim 6 for virus removal, said asymmetric polyethersulfone filter membrane comprising: the first fibers have an average diameter greater than an average diameter of the second fibers, and the second fibers have an average diameter of 30 to 75 nm.

8. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the PMI average pore diameter of the pre-filtering layer is 50-200nm, and the porosity is 75-93%; the thickness of the prefilter layer accounts for 70-90% of the thickness of the membrane.

9. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the average pore diameter of the separation layer is 15-25nm, the porosity is 60-80%, and the thickness of the separation layer is 2-20 μm.

10. An asymmetric polyethersulfone filter membrane according to claim 6 for virus removal, said asymmetric polyethersulfone filter membrane comprising: the pre-filtering layer also comprises a transition area, the transition area is positioned on one side of the pre-filtering layer close to the separating layer, the continuous fibers form a porous structure of the transition area, and the continuous fibers gradually change from a sheet structure to a strip structure; one side of the continuous fibers adjacent the separation layer is continuous with one side of the second fibers adjacent the pre-filter layer.

11. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the average pore diameter of the transition region is 60-170nm, and the porosity is 75% -82%; the thickness of the transition zone is 4-20 μm.

12. An asymmetric polyethersulfone filter membrane for virus removal according to claim 1, wherein said asymmetric polyethersulfone filter membrane comprises: the tensile strength of the polyether sulfone filter membrane is 6-12MPa, and the elongation at break is 8-30%;

the flux of the polyether sulfone filter membrane is more than 600L x h^-1*m^-2@30psi；

The protein yield of the polyether sulfone filter membrane is not lower than 98%.

13. The method for preparing an asymmetric polyethersulfone filter membrane for virus removal according to any one of claims 1-12, wherein the asymmetric polyethersulfone filter membrane comprises: the method comprises the following steps:

14. The method for preparing an asymmetric polyethersulfone filter membrane for virus removal according to claim 13, wherein said organic solvent is at least one of 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-formamide in a mass ratio of 4: 1; 1;

the thickness of the liquid film is at least greater than 200 um.

15. The method for preparing the asymmetric polyethersulfone filter membrane for removing viruses as claimed in claim 13, wherein said coagulation bath comprises water, and the temperature of said coagulation bath is 20-50 ℃; the cloud point temperature of the casting solution is 30-60 ℃.