A structurally controllable regenerated cellulose virus-removing filter membrane and its preparation method

Abstract

This invention relates to the field of membrane separation, and more particularly to a regenerated cellulose virus-removing filter membrane with controllable structure and its preparation method. The method in this application adjusts the saturated vapor pressure of the coagulation bath, thereby changing the phase separation rate of the casting solution in the coagulation bath, ultimately preparing a virus-removing membrane with moderate thickness, high protein permeability, and good virus retention effect. This enables the prepared cellulose filter membrane to retain viruses with a size of 20 nm and above.

Description

Technical Field

[0001] This invention relates to the field of membrane separation, and more particularly to a regenerated cellulose virus-removing filter membrane with controllable structure and its preparation method. Background Technology

[0002] In the fields of biopharmaceuticals and recombinant proteins, virus removal is an essential step. Membrane separation is an extremely gentle virus removal method that ensures excellent virus removal capabilities while having almost no impact on proteins. However, traditional PES virus removal membranes have high protein adsorption, making the use of cellulose to prepare virus removal membranes a highly promising approach.

[0003] With the development of the times and the advancement of science and technology, the demand for filtration in the biopharmaceutical field is constantly increasing. Modern high-efficiency separation typically relies on membranes. Membrane separation technology offers advantages such as high separation efficiency, low energy consumption, and small footprint. The core component, the separation membrane, primarily utilizes the pressure difference across the membrane to separate solutions that cannot separate naturally, thereby achieving separation, purification, and concentration. In the biological and pharmaceutical fields, the characteristic of membrane separation technology that it does not easily cause denaturation of active substances makes it widely used in the production processes of various biological agents.

[0004] In practical applications, it is usually necessary to select a filter membrane with an appropriate pore size based on the experimental requirements of the filtration purpose, and to utilize the differences between pore sizes to achieve the ideal retention effect.

[0005] US Patent Application No. 9010545A discloses a method for preparing a multilayer composite virus-removing PES membrane. This method uses two different casting solutions, which are simultaneously extruded through a mold onto a moving steel belt and immersed in a coagulation bath to obtain a composite membrane with one layer of macropores and one layer of micropores. This process requires very sophisticated equipment and is extremely complex; multilayer pore membranes cannot be produced in a single step.

[0006] Application CN115608165A discloses an asymmetric cellulose filter membrane for virus removal and its preparation method. In the preparation process, the asymmetric cellulose filter membrane is integrally formed using a casting solution without the need for composite materials. The pore sizes on both outer surfaces are adjusted to be different, and the filter membrane body is divided into a dirt-holding layer and a retention layer based on the different pore size ranges. The average pore size of the membrane body gradually changes slowly with thickness. Factors such as the pore size, number, and shape of the membrane pores significantly affect the filtration accuracy and membrane flow rate. However, the pore size variation range of this application is limited, making it impossible to precisely control the desired pore size. Controlling the distribution range of different pore sizes is crucial for the filtration process. Therefore, a preparation method that can effectively control the pore size distribution of the filter membrane within a limited range is needed. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of existing regenerated cellulose virus-removing filter membranes, which are difficult to precisely control the pore size of the filter membrane during preparation and have complex preparation processes. The invention provides a regenerated cellulose virus-removing filter membrane with controllable structure and its preparation method to overcome the above-mentioned deficiencies.

[0008] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution:

[0009] In a first aspect, this application provides a method for preparing a regenerated cellulose virus-removing filter membrane with controllable structure, comprising the following steps:

[0010] (S.1) Dissolve cellulose in a copper ammonia solution to prepare a casting solution;

[0011] (S.2) The casting solution is cast onto the substrate surface to form a liquid film;

[0012] (S.3) Immerse the liquid film in a coagulation bath to solidify and form a hydrated cellulose membrane;

[0013] (S.4) The hydrated cellulose membrane is regenerated to obtain the regenerated cellulose virus-removing filter membrane.

[0014] Its characteristic is that it further includes:

[0015] The steps of allowing the casting solution described in step (S.1) to stand to reduce the defect rate of the regenerated cellulose virus-removing filter membrane, and adjusting the saturated vapor pressure of the coagulation bath to 8.5 kPa-14.9 kPa before step (S.3).

[0016] The inventors made an unexpected discovery during their routine research: the pore size of the cellulose membrane surface is significantly related to the saturated vapor pressure of the coagulation bath used during the membrane preparation process. By purposefully controlling the saturated vapor pressure of the coagulation bath, cellulose membranes with the desired pore size range can be obtained.

[0017] The inventors conducted a series of investigations into this accidental discovery and found that the principle lies in the following: the stronger the interaction force between the molecules of the coagulation bath liquid, the slower the exchange rate of the casting solution during the phase transformation process after immersion in the coagulation bath, resulting in a larger pore size of the obtained filter membrane; conversely, the weaker the interaction force between the molecules of the coagulation bath liquid, the faster the exchange rate of the casting solution during the phase transformation process, resulting in a smaller pore size of the obtained filter membrane. The interaction force between the molecules of the coagulation bath liquid is macroscopically manifested as a corresponding saturated vapor pressure value. Generally speaking, the stronger the interaction force between the molecules of the coagulation bath liquid, the lower its corresponding saturated vapor pressure, and vice versa. The applicant therefore concluded that it is practically feasible to prepare filter membranes with different pore sizes by controlling the saturated vapor pressure of the coagulation bath.

[0018] Generally speaking, the diameter of viruses is around 20nm-250nm. The purpose of the filter membrane in this application is to remove viruses from the solution. Therefore, the SEM of the retention layer of the regenerated cellulose virus-removing filter membrane needs to be below 30nm in order to achieve the purpose of thoroughly filtering viruses from the solution.

[0019] Actual testing revealed that when the saturated vapor pressure of the coagulation bath was adjusted to between 8.5 kPa and 14.9 kPa, the regenerated cellulose filter membrane obtained after the casting liquid was immersed in the coagulation bath possessed the ability to filter viruses from the solution. The method of this invention can prepare a filter membrane with an asymmetric structure, comprising a porous layer and a retention layer. One side of the porous layer is a porous inlet surface with an average pore size ranging from 1 μm to 4 μm, designed to filter large particles and large protein aggregates from the solution. Simultaneously, the large-pore porous inlet surface reduces the resistance of the liquid passing through the filter membrane, thereby increasing the water flux. The retention layer has an average pore size ranging from 10 nm to 25 nm, enabling it to completely retain and filter viral components from the solution. When the saturated vapor pressure of the coagulation bath is less than 8.5 kPa, the strong intermolecular forces within the coagulation bath result in a relatively stable state, which is not conducive to exchange with the casting solution. This leads to a slow phase separation rate and a larger pore size in the prepared filter membrane, making it unsuitable for virus filtration. Conversely, when the saturated vapor pressure of the coagulation bath is greater than 14.9 kPa, the phase transition rate accelerates, causing a rapid decrease in the pore size of the prepared filter membrane. This can even result in an ultrafiltration structure, affecting protein permeation during virus filtration and significantly reducing water flux, making it difficult to apply effectively in practical scenarios.

[0020] In addition to controlling the saturated vapor pressure of the coagulation bath, this application also includes key treatments for the casting solution and the liquid film obtained after the casting solution is cast onto the substrate surface.

[0021] The inventors discovered that after the casting solution is prepared, the cellulose undergoes a certain orientation and stress during the dissolution process due to stirring. If this is not addressed, defects often occur during film formation, affecting the flux, retention, and loading capacity of the filtration membrane. Therefore, this application adds a settling process after the casting solution is prepared. This settling process not only removes residual air bubbles but also allows the cellulose molecular chains sufficient time to unfold, thus stabilizing the casting solution and bringing it to a more natural state. Therefore, this application's addition of a settling process after the casting solution is prepared effectively reduces the defect rate of the final cellulose filter membrane.

[0022] In this application, the saturated vapor pressure of the coagulation bath can be adjusted in various ways, such as by adjusting the temperature and composition of the coagulation bath. Therefore, different adjustment methods can be selected, providing more options for realizing this invention.

[0023] Therefore, in summary, this application uses a combination of multiple technical means to prepare a regenerated cellulose virus-removing filter membrane with adjustable pore size and thickness. It has a good virus retention effect, while also having the advantage of high protein permeability. Furthermore, it can maintain high throughput during the filtration process, which greatly improves social benefits.

[0024] Preferably, the saturated vapor pressure of the coagulation bath is adjusted by changing the temperature of the coagulation bath.

[0025] Preferably, the coagulation bath temperature is 10℃-45℃.

[0026] Preferably, the saturated vapor pressure of the coagulation bath is adjusted by changing the composition of the coagulation bath.

[0027] Preferably, the coagulation bath component includes at least one of a low-saturated vapor pressure solvent or a high-saturated vapor pressure solvent. The low-saturated vapor pressure solvent is a solvent with a saturated vapor pressure < 10 kPa at 40°C, and the high-saturated vapor pressure solvent is a solvent with a saturated vapor pressure > 10 kPa at 40°C.

[0028] In this application, the saturated vapor pressure of the coagulation bath can be adjusted in various ways, such as by adjusting the temperature and composition of the coagulation bath. Therefore, different adjustment methods can be selected, providing more options for realizing this invention.

[0029] Preferably, the low-saturated vapor pressure solvent is at least one of water, tetrachloroethylene, pentachloroethane, 1,1,2,2-tetrachloroethane, acetic acid, dimethylformamide, n-propanol, n-butanol, isobutanol, pyridine, n-pentanol, isoamyl alcohol, butyl acetate, toluene, and xylene; the high-saturated vapor pressure solvent is at least one of carbon tetrachloride, chloroform, formic acid, methanol, ethanol, 1,2-dichloroethylene, acetonitrile, acetone, tetrahydrofuran, diethylamine, methyl tert-butyl ether, diisopropyl ether, and hexane.

[0030] Preferably, the mass ratio of the high saturated vapor pressure solvent to the low saturated vapor pressure solvent is (0.05-5):1, and more preferably (0.2-3):1.

[0031] The (S.2) step further includes a step of preforming the liquid film in an air atmosphere.

[0032] In this application, after casting the liquid film, the liquid film is not immediately immersed in the coagulation bath. Instead, the liquid film is first pre-formed in an air atmosphere, which allows the moisture in the liquid film to exchange with the air to a certain extent, thereby controlling the obtaining of virus-removing filter membranes with different pore sizes and distributions.

[0033] Preferably, the preforming conditions are as follows: preforming temperature 20℃-30℃, air humidity 40%-80%, wind speed 0.1 m / s-1m / s, and preforming dwell time 0.5 s-10s.

[0034] Preferably, the regeneration process includes a step of water washing followed by acid washing and regeneration.

[0035] Preferably, the regeneration bath is either an acid solution or an acidic salt solution.

[0036] Preferably, the acid washing and regeneration includes placing the water-washed hydrated cellulose membrane in a regeneration bath;

[0037] The regeneration bath is a solution of at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, citric acid, malic acid, maleic acid, copper chloride, zinc chloride, calcium chloride, magnesium chloride, copper sulfate, zinc sulfate, and calcium sulfate.

[0038] Preferably, the casting solution in step (S.1) comprises, by weight percentage: 2 wt%-10 wt% copper, 5 wt%-25 wt% ammonia, 5 wt%-20 wt% cellulose, 0.1 wt%-5 wt% antioxidant, 5 wt%-50 wt% pore-forming agent, and 1 wt%-5 wt% thickener.

[0039] Generally speaking, the lower the solid content of cellulose in the casting solution, the lower the density of the prepared membrane, and therefore the larger the pore size of the prepared membrane. However, the mechanical properties of the membrane, such as strength and toughness, will be correspondingly lower. On the other hand, the higher the solid content of cellulose, the higher the density of the membrane, and the more compact the cellulose molecules are arranged, so the mechanical properties of the membrane will be correspondingly improved. However, this will reduce the pore size of the membrane and the membrane flux.

[0040] Generally, when preparing cellulose filter membranes, a cellulose solids content of 1 wt% to 4 wt% is common. However, the cellulose solids content of the casting solution in this application is 5 wt% to 20 wt%, which is significantly higher than that of traditional casting solutions. Therefore, under theoretical conditions, the pore size of the filter membrane prepared using a high-solids casting solution would be smaller, leading to a decrease in water flux. However, by adjusting the saturated vapor pressure of the coagulation bath, this application can control the phase separation rate of the casting solution in the coagulation bath to be lower. This results in a cellulose filter membrane with a larger pore size on the porous inlet surface and a larger pore area on the porous outlet surface while maintaining a small pore size, thus effectively ensuring membrane flux and mechanical properties.

[0041] This application also adds a certain amount of pore-forming agent to the casting solution. Its main function is to make the pores of the porous membrane more interconnected during the phase transformation process of the liquid film, thereby greatly increasing its LMH while ensuring retention. The addition of a thickener can effectively increase the viscosity of the casting solution, thus making the casting solution more uniform and stable.

[0042] Preferably, the antioxidant includes at least one of glucose, sucrose, anhydrous sodium sulfite, sodium bisulfite, sodium metabisulfite, butylphenol, tert-butyl-p-hydroxyanisole, thiourea, vitamin C, propyl gallate, α-tocopherol, and ascorbyl palmitate.

[0043] Preferably, the pore-forming agent includes at least one selected from polyvinylpyrrolidone, polyethylene glycol, glycerol, ethylene glycol, methanol, ethanol, propanol, butanol, formamide, and acetamide.

[0044] Preferably, the thickener includes at least one of starch, gum arabic, pectin, agar, gelatin, alginate, carrageenan, dextrin, carboxymethyl cellulose, propylene glycol alginate, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium alginate, casein, sodium polyacrylate, polyoxyethylene, and polyvinylpyrrolidone.

[0045] Preferably, the settling temperature of the casting solution is 10℃-50℃, and the settling time is 12h-96h.

[0046] During actual operation, the applicant discovered that virus-removing filter membranes with different pore sizes and distributions can be obtained by controlling pre-forming conditions such as wind speed, temperature, air humidity, and residence time. Within a certain range, the higher the air humidity, the higher the air wind speed, the longer the residence time, and the higher the temperature, the greater the degree of water vapor exchange with the wet membrane, and the larger the surface openings.

[0047] Preferably, in step (S.2), the settling temperature of the casting solution is 10℃-50℃, and the settling and degassing time is 12h-96h.

[0048] Cellulose in the casting solution requires stirring during dissolution to improve its solubility. However, as a natural polymer, cellulose is subjected to stirring forces, resulting in orientation and internal stress along the stirring direction. This orientation and internal stress can cause defects in the cellulose membrane formation process. Therefore, a settling treatment is necessary to allow the cellulose within the casting solution to unwind during its free rotation, thereby eliminating the orientation and internal stress.

[0049] The applicant discovered that the free rotation and movement of cellulose are significantly affected by temperature. At low temperatures, its free rotation and movement activity is lower, thus requiring a longer settling time to eliminate internal orientation and internal stress. Conversely, at higher temperatures, only a shorter settling time is needed to eliminate these internal orientations and internal stresses. In this application, a settling temperature of 10℃-50℃ allows for the production of a casting solution free of internal orientation and internal stress within a reasonable process time range, thereby improving the quality of the final cellulose filter membrane and increasing the efficiency of cellulose filter membrane preparation.

[0050] Preferably, the liquid film is obtained by scraping the casting liquid onto the substrate at a uniform speed using a doctor blade.

[0051] Preferably, the substrate includes any one of PET film, steel strip, and glass plate.

[0052] Secondly, this application provides a regenerated cellulose virus-removing filter membrane with controllable structure prepared by the method described above. The main structure of the regenerated cellulose virus-removing filter membrane includes a loose layer and a retention layer. One side of the loose layer is a porous liquid inlet surface, and one side of the retention layer is a porous liquid outlet surface. The other side of the loose layer and the other side of the retention layer are transitioned by continuous fibers.

[0053] The average pore size of the porous liquid inlet surface is 1 μm - 4 μm.

[0054] The average pore size of the porous liquid outlet surface is 10 nm - 30 nm.

[0055] The average pore size of the retaining layer is 15 nm - 30 nm.

[0056] The average pore size of the loose layer is 1 μm - 2.5 μm.

[0057] The filter membrane in this application is a regenerated cellulose filter membrane. Compared with polyethersulfone (PES) filter membranes, it has good hydrophilicity and lower protein adsorption capacity, thus effectively reducing protein loss during filtration. Furthermore, its structure shows a significant difference in pore size between the porous inlet and outlet surfaces of the cellulose filter membrane provided in this application. The average pore size of the pores on the outlet surface, measured by SEM, is 10 nm–25 nm, demonstrating a strong filtration effect on small viruses. In contrast, the pore size of the inlet surface is 1 μm–4 μm, which is 40–400 times larger than that of the outlet surface. This allows for effective filtration of large particulate impurities in the liquid being filtered while maintaining the inlet rate of the porous inlet surface. Meanwhile, the loose layer and the retention layer are connected by continuous fibers. Therefore, the cellulose filter membrane provided in this application has a uniform change along its thickness direction, which can effectively retain large protein aggregates of various sizes, thereby preventing them from clogging the filter pores at the porous liquid outlet and causing a decrease in protein recovery rate.

[0058] Preferably, the thickness of the porous layer is 15 μm-25 μm, accounting for 10%-30% of the total membrane thickness.

[0059] The thickness of the retention layer is 60 μm-85 μm, accounting for 70%-90% of the total membrane thickness.

[0060] Preferably, the flow rate of the regenerated cellulose virus-removing filter membrane is 40 LMH / bar - 60 LMH / bar; the protein permeability of the regenerated cellulose virus-removing filter membrane is >99%; and the virus rejection capacity (LRV) of the regenerated cellulose virus-removing filter membrane is >6.

[0061] Therefore, this application has the following beneficial effects:

[0062] (1) By comparing the effect of the saturated vapor pressure of the coagulation bath on the membrane structure, this invention found that within a certain range, a regenerated cellulose virus-removing filter membrane with adjustable pore size and thickness can be prepared, which has a good retention effect on viruses, while proteins have a higher permeability and can maintain a high throughput during the filtration process, which greatly improves social benefits.

[0063] (2) The present invention adds a settling process after the casting solution is prepared, which can not only remove the residual air bubbles, but also allow the cellulose molecular chains to have enough time to unfold, thus tending to a natural state, making the casting solution more stable and reducing the defect rate of the final cellulose filter membrane.

[0064] (3) Before the filter membrane in this application is formed, a pre-forming step is first carried out in the air atmosphere, so that the water in the liquid membrane can be exchanged with the air to a certain extent, thereby controlling the virus removal filter membrane with different pore sizes and distributions.

[0065] (4) The preparation method in this application can prepare the desired regenerated cellulose virus-removing filter membrane in one step, thereby simplifying the preparation process of the regenerated cellulose virus-removing filter membrane. Attached Figure Description

[0066] Figure 1 This is a SEM image of the porous liquid inlet surface of the regenerated cellulose virus-removing filter membrane prepared in Example 1.

[0067] Figure 2 This is a SEM image of the porous liquid outlet surface of the regenerated cellulose virus-removing filter membrane prepared in Example 1.

[0068] Figure 3 This is a SEM image of a cross section of the regenerated cellulose virus-removing filter membrane prepared in Example 1. Detailed Implementation

[0069] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0070] Example 1

[0071] Prepare a casting solution with a total material weight of 12 kg. Weigh copper oxide, ammonia, glucose, polyvinylpyrrolidone, and starch, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 10℃, add bamboo pulp cellulose with a DP of 700 and dissolve it completely for 6 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 5 wt%, copper content of 2 wt%, ammonia content of 5 wt%, glucose content of 0.1 wt%, starch content of 1 wt%, and polyvinylpyrrolidone content of 5 wt%. After standing for 12 hours at 10℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 0.5 seconds under conditions of 40% humidity, 0.3 m / s wind speed, and 25°C, the liquid film, along with the substrate film, was transferred to a 15°C coagulation bath to solidify for 1 minute, forming a new film. The mass ratio of the coagulation bath was methanol:water = 0.4:3 (saturated vapor pressure 9.5 kPa). Subsequently, the film was washed in 25°C water and then placed in a 25°C regeneration bath containing 10 wt% citric acid to remove residual copper-ammonia complexes.

[0072] Figure 1 This is a SEM image of the porous liquid inlet surface of the regenerated cellulose virus-removing filter membrane prepared in this embodiment; Figure 2 This is a SEM image of the porous liquid outlet surface of the regenerated cellulose virus-removing filter membrane prepared in this embodiment; Figure 3 This is a SEM image of the cross-section of the regenerated cellulose virus-removing filter membrane prepared in this embodiment.

[0073] Example 2

[0074] Prepare a casting solution with a total material weight of 12 kg. Weigh copper hydroxide, ammonia, sodium sulfite, polyethylene glycol, and polyethylene oxide, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 15℃, add cotton pulp cellulose with a DP of 700 and dissolve it completely for 12 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 8 wt%, copper content of 4 wt%, ammonia content of 10 wt%, sodium sulfite content of 0.5 wt%, polyethylene oxide content of 2 wt%, and polyethylene glycol content of 10 wt%. After standing for 24 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 1 second in an environment with 50% humidity, 0.5 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 20°C coagulation bath to solidify for 3 minutes to form a film. The mass ratio of the coagulation bath was acetone:water = 0.25:2 (saturated vapor pressure 11.2 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 10 wt% malic acid to remove residual copper-ammonia complexes.

[0075] Example 3

[0076] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 3 seconds in an environment with 55% humidity, 0.4 m / s wind speed, and 25°C, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was tetrahydrofuran:water = 0.3:4 (saturated vapor pressure 8.5 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath of 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0077] Example 4

[0078] Prepare a casting solution with a total material weight of 12 kg. Weigh copper sulfate, ammonia, vitamin C, methanol, and dextrin, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 30℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely for 36 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 15 wt%, copper content of 8 wt%, ammonia content of 20 wt%, vitamin C content of 3 wt%, dextrin content of 3 wt%, and methanol content of 30 wt%. After standing at 40℃ for 48 hours to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 5 seconds in an environment with 60% humidity, 0.6 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 30°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was ethanol:water = 18:5 (saturated vapor pressure 14.9 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 20 wt% hydrochloric acid to remove residual copper-ammonia complexes.

[0079] Example 5

[0080] Prepare a casting solution with a total material weight of 12 kg. Weigh copper hydroxide, ammonia, ascorbate palmitate, formamide, and propylene glycol alginate, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 40℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely in the absence of air for 48 hours to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 20 wt%, copper content of 10 wt%, ammonia content of 25 wt%, ascorbate palmitate content of 5 wt%, propylene glycol alginate content of 5 wt%, and formamide content of 35 wt%. After standing at 50℃ for 96 hours to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 10 seconds in an environment with 75% humidity, 0.8 m / s wind speed, and 25°C, the liquid film, along with the substrate film, was transferred to a 40°C coagulation bath for 5 minutes to solidify and form a film. The mass ratio of the coagulation bath was (1,4-)dioxane:water = 2:1 (saturated vapor pressure 9.9 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 20 wt% hydrochloric acid to remove residual copper ammonia complexes.

[0081] Example 6

[0082] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 4 seconds in an environment with 80% humidity, 1 m / s wind speed, and 25°C, the liquid film, along with the substrate film, was transferred to a 30°C coagulation bath for 5 minutes to solidify and form a film. The mass ratio of the coagulation bath was pyridine:acetone = 1.5:2 (saturated vapor pressure 12.9 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0083] Example 7

[0084] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 5 seconds in an environment with 40% humidity, 0.1 m / s wind speed, and 20°C temperature, the liquid film, along with the substrate film, was transferred to a 30°C coagulation bath for 5 minutes to solidify and form a film. The mass ratio of the coagulation bath was pyridine:acetone = 1.5:2 (saturated vapor pressure 12.9 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0085] Example 8

[0086] Prepare a casting solution with a total material weight of 12 kg. Weigh copper sulfate, ammonia, vitamin C, methanol, and dextrin, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 30℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely for 36 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 15 wt%, copper content of 8 wt%, ammonia content of 20 wt%, vitamin C content of 3 wt%, dextrin content of 3 wt%, and methanol content of 30 wt%. After standing at 40℃ for 48 hours to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 5 seconds in an environment with 60% humidity, 0.6 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was ethanol:water = 18:5 (saturated vapor pressure 12.7 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 20 wt% hydrochloric acid to remove residual copper-ammonia complexes.

[0087] Comparative Example 1

[0088] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 3 seconds at 55% humidity and 25°C, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was tetrahydrofuran:water = 1:2 (saturated vapor pressure 23.5 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath of 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0089] Comparative Example 2

[0090] Prepare a casting solution with a total material weight of 12 kg. Weigh copper sulfate, ammonia, vitamin C, methanol, and dextrin, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 30℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely for 36 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 15 wt%, copper content of 8 wt%, ammonia content of 20 wt%, vitamin C content of 3 wt%, dextrin content of 3 wt%, and methanol content of 30 wt%. After standing for 48 hours at 40℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape the liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming by standing for 5 seconds at 60% humidity and 25℃, transfer the liquid film along with the substrate to a 30℃ coagulation bath (water, saturated vapor pressure 4.2 kPa) for 5 minutes to form a film. After being transferred to 25°C water for washing, it was then placed in a 25°C 20wt% hydrochloric acid regeneration bath to remove residual copper-ammonia complex.

[0091] Comparative Example 3

[0092] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 3 seconds in an environment with 55% humidity, 0.4 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was tetrahydrofuran:water = 1:5 (saturated vapor pressure 15.6 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath of 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0093] Comparative Example 4

[0094] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 3 seconds in an environment with 55% humidity, 0.4 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was tetrahydrofuran:water = 0.1:1 (saturated vapor pressure 7.8 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath of 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0095] Comparative Example 5

[0096] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700, and stir thoroughly for 24 hours in the absence of air to dissolve, thus preparing a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After the casting solution is prepared, pour it onto a substrate and scrape a liquid film at a thickness of 300 μm at a speed of 2 m / min. After pre-forming for 3 seconds in an environment with 55% humidity, 0.4 m / s wind speed, and 25°C, the liquid film, along with the substrate film, was transferred to a 25°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was tetrahydrofuran:water = 0.3:4 (saturated vapor pressure 8.5 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath of 15 wt% maleic acid to remove residual copper-ammonia complexes.

[0097] Comparative Example 6

[0098] Prepare a casting solution with a total material weight of 12 kg. Weigh copper chloride, ammonia, butylphenol, glycerol, and hydroxymethyl cellulose, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 20℃, add wood pulp cellulose with a DP of 700 and dissolve it completely for 24 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 10 wt%, copper content of 6 wt%, ammonia content of 15 wt%, butylphenol content of 1 wt%, hydroxymethyl cellulose content of 2.5 wt%, and glycerol content of 20 wt%. After standing for 36 hours at 25℃ to remove bubbles and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. Then, directly transfer the liquid film along with the substrate to a 25℃ coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath is tetrahydrofuran:water = 0.3:4 (saturated vapor pressure 8.5 kPa). After being washed in water at 25°C, it was then placed in a regeneration bath of 15wt% maleic acid at 25°C to remove residual copper-ammonia complex.

[0099] Comparative Example 7

[0100] Prepare a casting solution with a total material weight of 12 kg. Weigh copper sulfate, ammonia, vitamin C, methanol, and dextrin, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 30℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely for 36 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 15 wt%, copper content of 8 wt%, ammonia content of 20 wt%, vitamin C content of 3 wt%, dextrin content of 3 wt%, and methanol content of 30 wt%. After standing at 40℃ for 48 hours to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 5 seconds in an environment with 60% humidity, 0.6 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 5°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was ethanol:water = 18:5 (saturated vapor pressure 10.2 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 20 wt% hydrochloric acid to remove residual copper-ammonia complexes.

[0101] Comparative Example 8

[0102] Prepare a casting solution with a total material weight of 12 kg. Weigh copper sulfate, ammonia, vitamin C, methanol, and dextrin, and dilute with water to prepare a copper-ammonia solution. After adjusting the temperature to 30℃, add hemp pulp cellulose with a DP of 700 and dissolve it completely for 36 hours in the absence of air to prepare a homogeneous and stable cellulose casting solution with a cellulose content of 15 wt%, copper content of 8 wt%, ammonia content of 20 wt%, vitamin C content of 3 wt%, dextrin content of 3 wt%, and methanol content of 30 wt%. After standing at 40℃ for 48 hours to defoam and relieve stress, it is ready for use. Pour the prepared casting solution onto a substrate and scrape a liquid film at a speed of 2 m / min to a thickness of 300 μm. After pre-forming for 5 seconds in an environment with 60% humidity, 0.6 m / s wind speed, and 25°C temperature, the liquid film, along with the substrate film, was transferred to a 50°C coagulation bath to solidify for 5 minutes to form a film. The mass ratio of the coagulation bath was ethanol:water = 18:5 (saturated vapor pressure 20.6 kPa). Subsequently, it was transferred to 25°C water for washing, and then placed in a 25°C regeneration bath with 20 wt% hydrochloric acid to remove residual copper-ammonia complexes.

[0103] The regenerated cellulose virus-removing filter membranes with controllable structures prepared in Examples 1-8 and Comparative Examples 1-8 were tested.

[0104] The detection methods are as follows:

[0105] Average pore size test: The test was conducted using a PMI pore size distribution tester. First, a membrane of a certain size was cut. The membrane was then wetted with ethanol of different concentrations, followed by a low surface tension (15.6 mN / m) solvent (provided by the US equipment manufacturer PMI). The membrane was then placed in the test tank. Finally, the average pore size and the initial pore size of the bubble were obtained by passing the dry-wet line.

[0106] Flow rate: Tested using a Millipore Virusmax testing device with a 25mm stainless steel replaceable membrane filter (this device is used for both protein permeability and virus filtration experiments), with an effective filtration area of ​​4.1cm². 2 The filtration test was conducted using ultrapure water at a temperature of 25°C and a pressure of 2 bar.

[0107] Dense layer thickness test: The thickness of the dense layer is measured using SEM cross-sectional images.

[0108] Protein transmittance test: Prepare a protein solution of a certain concentration (e.g., 1 g / L, 5 g / L, etc.), and pre-filter it through a 0.22 μm filter to remove particles and prepolymers of the protein solution. Then, use a Millipore Virusmax test device with a 25 mm stainless steel membrane filter for testing. Use a UV-5 ultraviolet spectrophotometer (Mettler) at a wavelength of 280 nm to measure the absorbance. The transmittance calculation formula is as follows: Transmittance = C1 / C0 × 100%, where C1 is the concentration of the permeate and C0 is the concentration of the original solution.

[0109] Virus retention assay: Polyclonal antibody IgG was used as the antibody solution. 5% MVM (mouse parvovirus) and BVDV (bovine viral diarrhea virus) were added to the resulting antibody solution, and the mixture was thoroughly stirred to obtain an antibody solution containing the virus. The assay was performed using a Millipore Virusmax assay device with a 25mm stainless steel membrane filter.

[0110] The calculation formula is as follows: LRV = log10(C0 / C F )

[0111] Where: C0 represents the infection titer of the stock solution containing antibodies against the virus, C F This indicates the infection titer in the filtrate after using a regenerated cellulose virus-removing filter membrane.

[0112] Saturated vapor pressure test of the coagulation bath: A saturated vapor pressure meter (DPCY-6C) was used to measure the saturated vapor pressure of the coagulation bath. The test liquid was placed in the balance tube, the temperature was determined, and the pressure was adjusted to bring the test liquid to a boil. The pressure at this point is the saturated vapor pressure at that temperature. By measuring the saturated vapor pressure at different temperatures, the Clapeyron-Crossius equation can be used to fit a curve of saturated vapor pressure versus temperature.

[0113] The Clapeyron-Crothy equation is shown below:

[0114] .

[0115] Protein load test: Protein load was low without a resting period. Normal group: 1 kg / m² 2 Control 5 was 0.5 kg / m 2 .

[0116] The test results are shown in Table 1 and Table 2 below.

[0117] Table 1 Performance of virus-removing filter membranes in different embodiments

[0118] .

[0119] Table 2 Performance of virus-removing filter membranes in different comparative examples

[0120] .

[0121] As can be seen from the data in Examples 1-8 and Comparative Examples 1-8, this application, by adjusting the saturated vapor pressure of the coagulation bath to between 8.5 kPa and 14.9 kPa, thereby changing the phase separation rate of the casting solution in the coagulation bath, ultimately prepares a virus-removing membrane with moderate thickness, high protein permeability, and good virus retention effect. This enables the prepared cellulose filter membrane to retain viruses with a size of 20 nm and above. When the saturated vapor pressure of the coagulation bath is too low, the pore size of the filter membrane is too large, resulting in poor retention and making it unsuitable for virus filtration. Conversely, when the saturated vapor pressure of the coagulation bath exceeds a certain value, the pore size of the prepared filter membrane decreases rapidly, and an ultrafiltration structure may even be obtained, affecting the protein permeability in virus filtration.

[0122] Meanwhile, as can be seen from the data in the table above, in addition to the influence of the saturated vapor pressure of the coagulation bath on the pore size of the regenerated cellulose virus-removing filter membrane, the settling process after the casting solution is prepared and the pre-forming step after the casting solution is scraped into a liquid film have a significant impact on the performance of the regenerated cellulose virus-removing filter membrane. This ensures that the cellulose filter membrane also has the advantages of extremely high water flux and mechanical properties, greatly reducing the difficulty of preparing virus-removing filter membranes from natural cellulose and greatly improving social benefits.

Claims

1. A method for preparing a regenerated cellulose virus-removing filter membrane with controllable structure, comprising the following steps: (S.1) Dissolve cellulose in a copper ammonia solution to prepare a casting solution; (S.2) The casting solution is cast onto the substrate surface to form a liquid film; (S.3) Immerse the liquid film in a coagulation bath to solidify and form a hydrated cellulose membrane; (S.4) The hydrated cellulose membrane is regenerated to obtain the regenerated cellulose virus-removing filter membrane. Its characteristic is that it further includes: The step of allowing the casting solution described in step (S.1) to stand in order to reduce the defect rate of the regenerated cellulose virus-removing filter membrane, wherein the standing temperature of the casting solution is 10℃-50℃ and the standing time is 12h-96h; and the step of adjusting the saturated vapor pressure of the coagulation bath to 8.5KPa-14.9Kpa before step (S.3); The coagulation bath composition includes a mixture of a low-saturated vapor pressure solvent and a high-saturated vapor pressure solvent, wherein the mass ratio of the high-saturated vapor pressure solvent to the low-saturated vapor pressure solvent is (0.05-5):1; The (S.2) step further includes a step of preforming the liquid film in an air atmosphere; The preforming conditions are as follows: preforming temperature 20℃-30℃, air humidity 40%-80%, wind speed 0.1 m / s-1m / s, and preforming dwell time 0.5 s-10s.

2. The method according to claim 1, characterized in that, The saturated vapor pressure of the coagulation bath is adjusted by changing the temperature of the coagulation bath or by changing the composition of the coagulation bath.

3. The method according to claim 2, characterized in that, The temperature range of the coagulation bath is 10℃-45℃.

4. The method according to claim 3, characterized in that, The low-saturated vapor pressure solvent is at least one of water, tetrachloroethylene, pentachloroethane, 1,1,2,2-tetrachloroethane, acetic acid, dimethylformamide, n-propanol, n-butanol, isobutanol, pyridine, n-pentanol, isoamyl alcohol, butyl acetate, toluene, and xylene; the high-saturated vapor pressure solvent is at least one of carbon tetrachloride, chloroform, formic acid, methanol, ethanol, 1,2-dichloroethylene, acetonitrile, acetone, tetrahydrofuran, diethylamine, methyl tert-butyl ether, diisopropyl ether, and hexane.

5. The method according to claim 1, characterized in that, The regeneration process includes a step of water washing followed by acid washing and regeneration. The acid washing and regeneration process involves placing the water-washed hydrated cellulose membrane in a regeneration bath. The regeneration bath is a solution of at least one of hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, citric acid, malic acid, maleic acid, copper chloride, zinc chloride, calcium chloride, magnesium chloride, copper sulfate, zinc sulfate, and calcium sulfate.

6. The method according to claim 1, characterized in that, The casting solution in step (S.1) comprises, by weight percentage: 2wt%-10wt% copper, 5wt%-25wt% ammonia, 5wt%-20wt% cellulose, 0.1wt%-5wt% antioxidant, 5wt%-50wt% pore-forming agent, and 1wt%-5wt% thickener.

7. The method according to claim 6, characterized in that, The antioxidants include at least one of glucose, sucrose, anhydrous sodium sulfite, sodium bisulfite, sodium metabisulfite, dibutylphenol, tert-butyl-p-hydroxyanisole, thiourea, vitamin C, propyl gallate, α-tocopherol, and ascorbyl palmitate. The pore-forming agent includes at least one of polyvinylpyrrolidone, polyethylene glycol, glycerin, ethylene glycol, methanol, ethanol, propanol, butanol, formamide, and acetamide; The thickener includes at least one of starch, gum arabic, pectin, agar, gelatin, seaweed gum, carrageenan, dextrin, carboxymethyl cellulose, propylene glycol alginate, methyl cellulose, sodium starch phosphate, sodium carboxymethyl cellulose, sodium alginate, casein, sodium polyacrylate, polyoxyethylene, and polyvinylpyrrolidone.

8. A regenerated cellulose virus-removing filter membrane with controllable structure prepared by the method of any one of claims 1-7, wherein the main structure of the regenerated cellulose virus-removing filter membrane includes a loose layer and a retention layer, one side of the loose layer is a porous liquid inlet surface, one side of the retention layer is a porous liquid outlet surface, and the other side of the loose layer and the other side of the retention layer are transitioned by continuous fibers, characterized in that... The average pore size of the porous liquid inlet surface is 1 μm - 4 μm. The average pore size of the porous liquid outlet surface is 10 nm - 30 nm. The average pore size of the retaining layer is 15 nm - 30 nm, and the average pore size of the loose layer is 1 μm - 2.5 μm; The thickness of the porous layer is 15 μm - 25 μm, accounting for 10% - 30% of the total membrane thickness; The thickness of the retention layer is 60 μm-85 μm, accounting for 70%-90% of the total membrane thickness.

9. The regenerated cellulose virus-removing filter membrane with controllable structure according to claim 8, characterized in that, The flow rate of the regenerated cellulose virus-removing filter membrane is 40 LMH / bar - 60 LMH / bar; the protein permeability of the regenerated cellulose virus-removing filter membrane is >99%; and the virus rejection capacity (LRV) of the regenerated cellulose virus-removing filter membrane is >6.

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