Virus-removal cellulose filtration membrane, and preparation process therefor and use thereof

Abstract

A virus-removal cellulose filtration membrane, and a preparation process therefor and the use thereof. The filtration membrane comprises a porous main body, and the porous main body has a liquid inlet surface for allowing protein-containing feed liquid to enter and a liquid outlet surface allowing protein-containing feed liquid to flow out; the water flux Twater of the filtration membrane is 30 to 85 LMH@30 psi; the stable flux T240 of the filtration membrane for 50 g / L of protein-containing feed liquid is not lower than 5 LMH@30 psi; and the retention capacity of the filter membrane for a PP7 bacteriophage satisfies LRV≥5. Further disclosed in the present invention are a preparation process of the filtration membrane and the virus-removal filtration use of the filtration membrane in feed liquid with a concentration of greater than 20 g / L. A filtration membrane having a low water flux in general cognition often also has a relatively low protein filtrate flux. Although the filtration membrane in the present invention has a relatively low water flux, when the filtration membrane is used to filter a high-concentration protein preparation having a protein concentration of greater than 20 g / L, the filtration membrane has an unexpectedly high flux.

Description

A cellulose virus removal filter membrane and its preparation process and application Technical Field

[0001] The present application relates to the field of membrane separation technology, and in particular to a cellulose virus removal filter membrane and its preparation process and application. Background Art

[0002] For all types of biologics, whether it's endogenous viruses carried by the original cell line itself or exogenous viruses accidentally introduced during the production process, there is a risk of viral contamination in the biologics. This viral contamination can lead to serious clinical consequences. Therefore, the viral safety of all types of biologics must be guaranteed. This is also an important reason why relevant documents such as the 2020 edition of the "Chinese Pharmacopoeia" and ICH Q5A "Biological Technology Products - Viral Safety Evaluation" have set high requirements for the viral safety of biologics.

[0003] Membrane separation technology has the advantages of not requiring additional reagents, the separation process does not involve phase change, can be operated at room temperature, and has low energy consumption. It is particularly suitable for the separation and treatment of heat-sensitive substances and bioactive substances. Therefore, it has replaced some traditional common virus inactivation methods such as organic solvent inactivation, detergent inactivation, and low pH inactivation, and is widely used in the virus removal steps in the preparation process of various biological preparations.

[0004] Currently, the more commonly used virus removal membranes include PVDF virus removal membrane, PES virus removal membrane and cellulose virus removal membrane. Among them, PES virus removal membrane often has a higher filtration efficiency and good virus filtration effect, but the hydrophilicity of PES material is poor. The currently common commercial PES virus removal membrane that has undergone hydrophilic modification still has poor hydrophilicity and easily adsorbs active proteins in the feed liquid (the main active ingredient in biological preparations). PVDF virus removal membrane also has similar problems as PES virus removal membrane. Compared with PVDF and PES materials, cellulose materials have significantly better hydrophilicity and lower specific adsorption of active proteins in the feed liquid, and therefore often have a higher protein yield.

[0005] However, cellulose virus removal membranes have the disadvantage of low flux when filtering high protein concentration liquids, and even lose their practical industrial application value. For example, in the article "Effect of antibody solution conditions on filter performance for virus removal filter Planova 20N" published by Asahi Kasei Corporation in Wiley Online Library in March 2010, it was clearly mentioned that the antibody solution conditions (such as antibody concentration, ionic strength, pH value, etc.) will affect the filtration performance of the virus removal filtration process, and it was clearly mentioned that the Planova 20N produced by the company TM The optimal application condition of 20N cellulose virus removal membrane is IgG concentration of 10-20mg / mL. When the IgG concentration in the filtered liquid reaches 40mg / mL or even 50mg / mL, the Planova TM The average flux of 20N cellulose virus removal membrane will be as low as 10L / m 2 / h or even 4L / m 2 / h or less. It should be noted that if the filtration time is too long, the possibility of virus penetration increases and the reliability of virus retention cannot be guaranteed. Therefore, too low a flux means almost no production feasibility and cannot meet the actual mass production needs.

[0006] However, in addition to biological preparations such as immunoglobulins, which already have high concentrations, increasing the concentration of various low-concentration biological preparations has become an important trend in the technological updates and iterations of the field of biological preparations. For example, high-concentration monoclonal antibody preparations approved in recent years account for a high proportion of the total approved antibody preparations. This is because the current method of administration of various biological preparations is subcutaneous injection, and the maximum dose of subcutaneous administration generally needs to be controlled at less than 2mL. For example, the therapeutic dose of monoclonal antibody drugs is high, which means that a single subcutaneous injection of biological preparations must contain a higher concentration of active protein to ensure efficacy. In addition, high-concentration preparations often mean higher production efficiency and lower production costs. Based on various advantages, high-concentration preparations are the current development trend, but this also brings more severe challenges to their production process.

[0007] For example, for PES virus removal membranes, which have poor hydrophilicity and high protein adsorption rates, higher protein concentrations often mean a higher possibility of protein adsorption. A large amount of adsorbed protein can easily lead to blockage of the virus removal membrane pore structure, which rapidly reduces its lifespan and inevitably increases production costs. More importantly, higher protein adsorption means lower protein yields, and the high production costs of active proteins make the disadvantage of high protein loss difficult for manufacturers to accept. For virus removal membranes made of cellulose with good hydrophilicity and low protein adsorption rates, although they have a higher protein yield and thus lower protein loss due to their good hydrophilicity, their low flux when filtering high-concentration protein solutions makes it difficult to meet the virus removal needs of high-concentration protein solutions.

[0008] Obviously, for high-concentration protein preparations such as those with a concentration greater than 20 mg / mL (20 g / L), it is necessary to ensure a low possibility of virus breakthrough while also achieving high throughput and high protein yield, which is a technical problem that is currently difficult to achieve but urgently needs to be solved.

[0009] Summary of the Invention

[0010] The present application provides a cellulose virus removal filter membrane, its preparation process and application. Although the filter membrane in the present application has a relatively low water flux, it is different from the generally known filter membranes with low water flux which often also have low protein filtrate flux. When the filter membrane of the present application is used to filter high-concentration protein preparations with a protein concentration greater than 20 g / L, it has an unexpectedly high flux; in addition, the lower water flux also means efficient retention of viruses in the feed liquid, and the good hydrophilicity of the cellulose material makes the filter membrane of the present application not only have good virus retention effect and higher flux, but also have a higher protein yield. Therefore, the filter membrane of the present application is particularly suitable for virus removal filtration of high-concentration protein preparations with a concentration greater than 20 g / L.

[0011] In the first aspect, the present application provides a cellulose virus removal filter membrane, which adopts the following technical solution:

[0012] A cellulose virus removal filter membrane comprises a porous body having a liquid inlet surface for a feed liquid to enter and a liquid outlet surface for the feed liquid to flow out;

[0013] The water flux T of the filter membrane 水 Not higher than 85LMH@30psi and not lower than 30LMH@30psi;

[0014] The stable flux T of the membrane 240 Not less than 6LMH@30psi, the stable flux T 240The flux data of the membrane when the protein concentration n in the filtered liquid is 50 g / L and the filtration time t is 240 min;

[0015] The retention capacity of the filter membrane for PP7 phage satisfies LRV≥5@(0.1 g / L, IVIG).

[0016] By adopting the above technical solution, as mentioned above, the currently common cellulose virus removal membranes such as the commercially available Planova TM Although the 20N cellulose virus removal membrane has good virus retention ability and low protein loss when filtering medium and low concentration protein liquids with protein concentrations not higher than 20g / L, when filtering high concentration protein liquids with protein concentrations greater than 20g / L, the flux of the filter membrane decreases rapidly as the protein concentration in the liquid continues to increase. When the protein concentration in the liquid reaches 50g / L, its flux is close to 0, and it loses the possibility of being suitable for actual production.

[0017] It is generally believed that the water flux performance of a filter membrane can well characterize the transmembrane resistance of the filter membrane to the filtered liquid. This is because the higher the water flux of the filter membrane, the lower the transmembrane resistance of the filter membrane to deionized water, and the deionized water can pass through the filter membrane quickly. Similarly, when the filtered liquid is changed from deionized water to a protein liquid containing protein, the resistance of the filter membrane to the protein liquid should also be low. Therefore, the filter membrane should also have good flux when used to filter protein liquid. In other words, there should be a certain positive correlation between water flux and protein liquid flux. Of course, protein liquid has a higher viscosity than deionized water, and higher viscosity means greater transmembrane resistance. Therefore, the absolute value of the flux of protein liquid is generally lower than that of water.

[0018] Based on the above general knowledge, for the currently common cellulose virus removal membrane, if you want to improve its flux when filtering high-concentration protein liquid, the general practice is to further increase the water flux of the filter membrane to ensure that the filter membrane has low resistance to the liquid, thereby ensuring that when the filter membrane filters high-concentration protein liquid with a protein concentration greater than 20g / L, the protein liquid is subject to lower resistance from the filter membrane, thereby having a higher flux.

[0019] However, the inventors of the present application unexpectedly discovered that when the filter membrane is used to filter a high-concentration protein solution with a protein concentration greater than 20g / L, controlling the filter membrane to have a lower water flux can, on the contrary, enable the filter membrane to have a high protein solution flux that is counterintuitive. This is quite unexpected. The inventors of the present application controlled the water flux of the filter membrane to be no higher than 85LMH@30psi and LRV≥5. When the filter membrane was filtering a solution with a high protein concentration (50g / L, IVIG solution), the flux was still able to reach at least no less than 6LMH@30psi even when the filtration duration was a long 240min. When filtering a high-concentration protein solution, the Planova TM The flux of the 20N cellulose virus removal membrane has approached zero, making it unsuitable for production. This result is quite unexpected, as it contradicts the current understanding that a greater water flux leads to a greater protein filtration flux.

[0020] This may be because the virus removal filter membrane in this application adopts a dead-end filtration method. Compared with the tangential flow filtration method adopted by ordinary ultrafiltration membranes, since the dead-end filtration method is a complete transmembrane filtration of the feed liquid, the filter membrane tends to withstand greater pressure. According to the modified Mooney equation, it is generally believed that as the protein concentration in the feed liquid increases, the viscosity tends to increase exponentially. Higher viscosity often means that during virus removal filtration, the feed liquid is subject to higher flow resistance when flowing through the filter membrane, and the filter membrane itself will also be subject to higher pressure. When the protein concentration in the feed liquid is not higher than 20g / L (the concentration of IVIG, which will not be repeated later), the viscosity of the feed liquid can still be maintained at a relatively low level. When the protein concentration in the feed liquid is higher than 20g / L, or even reaches 50g / L or higher, the viscosity of the feed liquid increases rapidly, and the pressure on the filter membrane also increases rapidly. Since the cellulose material has the defect of being soft in texture (this is also why the Planova TM One of the important reasons why the official guidance filtration pressure of 20N cellulose virus removal membrane is 98kPa) is that when it is subjected to greater pressure, the filter membrane with softer cellulose material as the membrane-forming material is prone to the collapse of the pore structure, resulting in an undesirable significant reduction in the flux of the filter membrane.

[0021] Therefore, if conventional improvement methods are adopted to further improve the water flux performance of the filter membrane, although the filter membrane does have lower resistance to deionized water, higher water flux often means that the filter membrane has a higher porosity and / or a larger pore size. For working conditions with lower viscosity (such as deionized water or low-concentration protein feed), the pressure on the filter membrane is lower, and the pore structure of the filter membrane is not easily deformed under pressure. Higher porosity and / or larger pore size have lower resistance to the feed, thus having a higher flux. However, for high-concentration protein feed with a protein concentration greater than 20g / L, the viscosity of the feed increases sharply, and the pressure on the filter membrane also increases sharply. The porous body with higher porosity combined with the cellulose-based membrane-forming material with a relatively soft texture makes the filter membrane very prone to pore collapse when subjected to higher pressure. Once the membrane pores collapse, the porosity and pore size of the filter membrane will all decrease significantly (the membrane structure after collapse will become quite dense). The collapsed pore structure and the already high viscosity feed make the filter membrane have a lower flux for high-concentration protein feed. Therefore, as the water flux of the membrane increases, the filtration flux of the high-concentration protein solution of the membrane will counterintuitively decrease.

[0022] The specific selection of a filter membrane with a water flux of no more than 85LMH@30psi and an LRV ≥ 5 in this application means that the filter membrane has a certain resistance to deionized water, but it also means that it has a relatively low porosity and / or a smaller pore size, and thus has higher strength and self-supporting performance. When filtering high-concentration protein liquids, filter membranes with higher self-supporting performance are less likely to deform even under higher pressures, and are even less likely to experience pore structure collapse; therefore, during the filtration process, they actually have a higher porosity and / or a larger pore size than the collapsed membrane, and therefore have a higher filtration flux for high-concentration protein liquids.

[0023] Of course, the water flux of the filter membrane should not be too low. If the water flux of the filter membrane is less than 30LMH@30psi, although the strength of the filter membrane can be further improved, thereby having better self-supporting performance, too low a water flux often means that the filter membrane has too low a porosity and / or too small a pore size, and thus has a high resistance to deionized water. Therefore, when the filter membrane is used to filter a high-concentration protein liquid, even if the pore structure of the filter membrane does not undergo any deformation, its filtration resistance for the high-concentration protein liquid is also large. The unavoidable small amount of deformation and the already high viscosity of the liquid result in a low flux when the filter membrane is filtering a high-protein concentration liquid.

[0024] In summary, for the special high-concentration protein liquid virus removal filtration conditions, the high-concentration protein liquid flux of the filter membrane first increases continuously with the increase of water flux, and then decreases, rather than the generally accepted continuous increase with the increase of water flux. Therefore, in this application, by specifically selecting a filter membrane with a water flux of 30~85LMH@30psi, it can be ensured that the filter membrane has a higher flux when filtering high-concentration protein liquid.

[0025] It should be noted that the commercially available Planova TM The official nominal filtration pressure of the 20N cellulose virus removal membrane is about 14 psi. Therefore, although the test pressure in the aforementioned literature is not 30 psi, it is foreseeable that since 30 psi far exceeds the nominal filtration pressure of the commercially available cellulose virus removal membrane, the filter membrane is likely to experience excessive pore structure collapse under the conditions of a filtration pressure of 30 psi and a high viscosity of a high-concentration protein feed. This means further blockage of the feed flow channel in the filter membrane, and its flux will be further reduced, tending towards 0.

[0026] It is understood that the water flux data test conditions of the filter membrane in this application are to place the filter membrane in a filtration area of ​​4.1 cm 2 In a stainless steel metal holder (such as Millipore's Virusmax test device with an effective filtration area of ​​4.1 cm 2 The flux test is performed using a stainless steel replaceable membrane filter or other conventional flux test devices in the art) and deionized water as the test liquid. The water flux of the filter membrane referred to in this application is T 水 No higher than 85LMH@30psi means that the filter membrane is subjected to flux test by the above-mentioned test device, and the test pressure during the flux test is controlled at 30psi, and the test result is no higher than 85LMH; wherein LMH refers to L / (h·m 2 ).

[0027] The high-concentration protein solution flux data test conditions of the filter membrane in this application are the same as the water flux test conditions, with the only difference being that an IVIG solution with a concentration of 50 g / L is used as the test solution.

[0028] The virus retention ability test conditions of the filter membrane in this application are as follows: referring to the relevant virus retention test conditions in PDA TR41, the model virus is PP7 phage, the model protein is IVIG, the concentration of IVIG is 0.1 g / L, and the PP7 phage titer before and after filtration of the liquid is tested respectively. The retention data LRV of the filter membrane for PP7 phage can be calculated.

[0029] Optionally, the water flux T of the filter membrane 水 Not higher than 80LMH@30psi and not lower than 35LMH@30psi;

[0030] The stable flux T of the membrane 240 Not less than 10LMH@30psi;

[0031] The retention capacity of the filter membrane for PP7 phage satisfies LRV≥5.5@(0.1 g / L, IVIG).

[0032] Optionally, the water flux T of the filter membrane 水 Not higher than 75LMH@30psi and not lower than 40LMH@30psi; further optionally, the water flux T 水 Not higher than 70LMH@30psi and not lower than 50LMH@30psi.

[0033] Optionally, the stable flux T of the filter membrane 240 Not less than 12LMH@30psi; further optionally, the stable flux T of the filter membrane 240 Not less than 14LMH@30psi.

[0034] Optionally, the retention capacity of the filter membrane for PP7 phage satisfies LRV≥5.8@(0.1 g / L, IVIG); further optionally, the retention capacity of the filter membrane for PP7 phage satisfies LRV≥6.0@(0.1 g / L, IVIG).

[0035] By adopting the above technical solution, it is also unexpected that, on the basis of the water flux of the filter membrane being no higher than 85LMH@30psi, the water flux of the filter membrane is further controlled to be no higher than 75 or even no higher than 70LMH@30psi. As the water flux of the filter membrane further decreases, when the filter membrane filters a high-concentration protein solution with a protein concentration of 50g / L, a further preferred flux of no less than 10 or even no less than 12LMH@30psi can be obtained.

[0036] This may be because, unlike filtering low-viscosity liquids, when a membrane is used to filter high-viscosity liquids, its flux performance is affected by the combined effects of multiple factors. Lower water flux and higher virus retention capacity mean lower porosity and / or smaller pore size, which often leads to increased resistance to the liquid. However, lower porosity and / or smaller pore size also mean further improvements in the membrane's pressure resistance and self-supporting properties, resulting in smaller pore structure deformation when filtering high-viscosity liquids.

[0037] As the water flux of the membrane decreases gradually (for example, from 85 to 80 or even 75 or 70 LMH @ 30 psi), the greater impact on the high-viscosity liquid filtration flux of the membrane may be the pressure resistance of the membrane, rather than the resistance of the membrane pores to the liquid. This is because although the decrease in the water flux of the membrane is accompanied by an increase in the liquid resistance, the increase in the liquid resistance is relatively slow and the impact is relatively small; however, the decrease in the water flux of the membrane is accompanied by a rapid increase in the pressure resistance of the membrane, which causes the deformation of the membrane to decrease rapidly when subjected to greater pressure. The smaller deformation means that the membrane has a higher porosity and / or pore size during the actual filtration process, thereby further improving the high-viscosity liquid filtration flux of the membrane. As the water flux of the filter membrane further decreases, although the pressure resistance of the filter membrane is further improved, the further improvement of the pressure resistance has a marginal diminishing effect on the filter membrane that already has a small deformation. The deformation of the filter membrane can indeed be further reduced, but the improvement is small; and the further reduction of the porosity and / or pore size of the filter membrane means that the resistance of the filter membrane to the feed liquid is further improved, which makes it difficult for the filter membrane to obtain a higher flux when filtering high-concentration protein feed liquid even with a smaller deformation. Therefore, the high-concentration protein feed flux of the filter membrane decreases with the water flux, showing a trend of gradually increasing and then gradually decreasing. Therefore, the water flux of the filter membrane is not the higher the better, nor the lower the better. In the present application, the water flux of the filter membrane can be further preferably not less than 40 or even not less than 50LMH@30psi, so that the filter membrane can obtain a further more preferred high-concentration protein feed filtration flux performance under the influence of various influencing factors such as feed liquid resistance and pressure resistance.

[0038] It's important to note that when the feed liquid is ultrapure water or a low-concentration protein solution, the pressure on the membrane is low and the deformation of the membrane pore structure is small. Therefore, the porosity and / or pore size of the membrane when it is not under pressure are not much different from the porosity and / or pore size of the membrane in actual use. This means that a high water flux of the membrane often also means that the membrane has a high flux when filtering low-concentration protein solutions.

[0039] However, when the feed liquid is a high protein concentration feed liquid with a protein concentration greater than 20g / L, what directly affects the filter membrane flux is not the porosity and / or pore size of the filter membrane when not under pressure, but the porosity and / or pore size of the filter membrane after it is subjected to a large pressure and deformed (that is, in actual application). Therefore, the fact that the filter membrane has a higher porosity and / or pore size when not under pressure does not mean that the filter membrane still has a higher porosity and / or pore size after being subjected to a large pressure; in fact, the inventors of this application have found that appropriately reducing the water flux of the filter membrane means that the filter membrane has a properly reduced porosity and / or pore size, and thus has a higher pressure resistance, thereby reducing the deformation amount of the filter membrane after being subjected to a large pressure, and instead having a higher porosity and / or pore size in actual use. This results in the abnormal phenomenon that the flux of the filter membrane increases as the water flux decreases when filtering a high-concentration protein feed liquid, which is also very unexpected.

[0040] Optionally, the top wash LRV retention rate of the filter membrane is not less than 0.85.

[0041] Optionally, the top wash LRV retention rate of the filter membrane is not less than 0.9.

[0042] By adopting the above technical solution, for the specific high-concentration protein solution conditions of this application, even if the membrane-forming material is a hydrophilic cellulose material, it is still difficult to avoid the membrane retaining and adsorbing a small amount of protein in the solution. As mentioned above, the high production cost of active proteins necessitates a high recovery rate for the protein solution. Therefore, after using the membrane for virus removal, the protein in the filter membrane must be further eluted, a process called top wash.

[0043] In order to ensure that the protein in the filter membrane is fully eluted to improve the protein recovery rate, after the membrane virus removal filtration / virus challenge test is completed (the filtration is considered to be completed when the membrane flux drops to 25% or the challenge liquid is filtered until only a small amount remains at the bottom), the pressure on the feed liquid side needs to be removed, and after adding buffer to the feed liquid side, the process is kept at normal pressure for a period of time (generally 15 minutes is sufficient, and no filtration or other operations are performed at this stage), so that the protein retained by the filter membrane has sufficient time to move and diffuse and be released, or be released again due to changes in the membrane pore structure; after the process residence is completed, the pressure is increased again to perform the virus filtration / virus challenge test after the process residence, and the filtrate obtained from the test is collected separately and the virus titer is determined, and the LRV after the process residence is calculated.

[0044] During the process dwell phase, not only proteins are released and eluted due to movement, diffusion, and changes in membrane pore structure, but viruses originally retained by the membrane are also released and eluted due to movement, diffusion, and changes in membrane pore structure. Therefore, the LRV after a process dwell phase is generally lower than the LRV measured by a normal virus challenge test. The ratio of the LRV data after a process dwell phase to the LRV data measured by a normal virus challenge test is the LRV retention rate. A higher LRV retention rate indicates that the membrane released less virus during the process dwell phase.

[0045] Obviously, the main factors affecting the LRV retention rate of the filter membrane are the movement and diffusion of the virus itself and the degree of change in the membrane structure of the filter membrane. It is generally believed that viruses and proteins both undergo disordered Brownian motion, and the main influencing factors of Brownian motion are particle size and temperature. In addition, the greater the deformation recovery of the filter membrane after the liquid pressure is removed, the more proteins and viruses are released. This is because the filter membrane that has been deformed under pressure will recover its deformation after the liquid pressure is removed. During the deformation recovery process, it will exert a force on the proteins and viruses trapped / adsorbed in the filter membrane. This force can promote the release of proteins and viruses from the membrane pore structure, and the possibility of subsequent elution is higher. The top wash LRV naturally decreases, resulting in a decrease in the LRV retention rate of the filter membrane. Therefore, the higher the pressure resistance of the filter membrane, the higher the LRV retention rate.

[0046] The LRV retention rate of the filter membrane is not less than 0.85, which means that the filter membrane has good pressure resistance. In combination with the water flux of the filter membrane being not higher than 85LMH@30psi and LRV≥5@(0.1g / L, IVIG), the filter membrane can have a further preferred high-concentration protein liquid filtration flux.

[0047] Optionally, the long-term average flux of the filter membrane is 8 to 30 LMH@30 psi, and the long-term average flux is the average flux value when the protein concentration of the filter membrane in the filtered liquid is 50 g / L and the filtration time t is 100 min to 300 min.

[0048] Optionally, the long-term average flux of the filter membrane is 10 to 30 LMH@30 psi; further optionally, the long-term average flux of the filter membrane is 12 to 30 LMH@30 psi.

[0049] By employing this technical solution, when filtering high-concentration protein solutions, the membrane's pore structure becomes clogged not only by retained viruses but also by small amounts of protein adsorbed by the membrane. If the membrane's capacity to hold contaminants is too small after compression and deformation, the small amount of retained viruses and adsorbed protein can severely clog the membrane's pore structure, leading to a rapid decrease in membrane flux.

[0050] It is generally believed that a membrane with a higher water flux has a higher porosity and / or pore size, naturally providing more space for dirt to accumulate and making it less susceptible to pore blockage. However, the membrane in this application, while having a lower water flux when filtering a high-concentration protein solution, was able to maintain a high average filtration flux over a longer filtration time, which was also unexpected.

[0051] The long-term flux average value means that the filtration flux data of the filter membrane is recorded every 5 minutes, with the filtration time of 100 minutes as the starting point and the filtration time of 300 minutes as the end point (of course, the recording frequency can be appropriately increased or decreased according to actual needs, but the recording frequency should not be greater than 10 minutes / time to avoid introducing excessive errors), and the average flux data of the filter membrane during this time period is calculated based on the recorded data.

[0052] Optionally, the protein flux attenuation coefficient X of the filter membrane 50 @100min is not higher than 85%, the protein flux attenuation coefficient of the filter membrane is X 50 @100min is obtained by the following formula: Xn=(1-T t / T 水 )×100%;

[0053] In the above formula, Xn is the protein flux attenuation coefficient when the protein concentration in the feed solution is n, T t is the flux data of the filter membrane when the protein concentration in the filtered liquid is n and the filtration time is t, the unit is LMH; X 50 @100min refers to the protein flux attenuation coefficient when the protein concentration n in the feed solution is 50g / L and the filtration time t is 100min.

[0054] By adopting the above technical solution,

[0055] The protein flux attenuation coefficient X of the filter membrane in this application 50 The "@100min" value is no higher than 85%. This refers to the flux decay rate of the membrane when used to filter a 50 g / L protein solution for 100 minutes, compared to the water flux data. For example, if the water flux of the membrane is 100 LMH, and the flux when used to filter a 50 g / L protein solution for 100 minutes is 20 LMH, the protein flux decay coefficient of the membrane is 80%. A larger flux decay coefficient indicates that the flux of the membrane when used to filter a high-concentration protein solution is attenuated compared to the water flux of the membrane.

[0056] The filter membrane in the present application controls the water flux of the filter membrane to be no higher than 85LMH@30psi and LRV ≥ 5@(0.1g / L, IVIG), and cooperates with the filter membrane to have a flux attenuation coefficient of no higher than 85%, thereby ensuring that the filter membrane has a flux that is slightly different from the water flux when filtering high-concentration protein liquid.

[0057] The flux data when the filter membrane filtration time is 100 minutes is specifically selected to calculate the protein flux attenuation coefficient because, for the virus removal membrane using dead-end filtration, the flux of the filter membrane will show a significant decline at the beginning when the virus removal is performed. When the filtration time reaches 100 minutes, the filter membrane is often no longer in the stage of rapid flux decline, and is more valuable for reference.

[0058] Optionally, the protein flux attenuation coefficient of the filter membrane, X 50 @100min is not higher than 80%, the T 100 Not less than 12LMH@30psi.

[0059] By adopting the above technical solution, the flux attenuation coefficient of the filter membrane is further limited to no more than 80%, and the water flux of the filter membrane is no more than 85LMH@30psi and LRV≥5@(0.1g / L, IVIG), which can further ensure that the filter membrane has a higher flux when filtering high-concentration protein liquid. The T 100 Not less than 12LMH@30psi, which has a multiple-fold increase in flux compared to the currently commercially available cellulose virus removal membranes.

[0060] Optionally, the relative deviation of the mid-term flux of the filter membrane is not higher than 20%, and the relative deviation of the mid-term flux is the relative deviation between the flux data at a filtration time t of 100 min and the flux data at a filtration time t of 200 min when the protein concentration n of the filter membrane in the filtered liquid is 50 g / L.

[0061] By adopting the above technical solution, since the filter membrane in this application is a cellulose filter membrane with good hydrophilicity and low protein adsorption, when the filter membrane is used to filter deionized water or low-concentration protein liquid, the membrane pore structure of the filter membrane is often not easily blocked by the protein liquid. When the filter membrane is used to filter high-concentration protein liquid, even if the protein adsorption rate of the filter membrane is low, due to the high protein concentration in the liquid, the absolute value of the protein adsorbed and retained by the filter membrane is inevitably high. Therefore, as the virus filtration time increases, the amount of protein retained in the filter membrane increases, and part of the pore structure is inevitably blocked, which will inevitably lead to a decrease in the filter membrane flux.

[0062] In this application, the relative deviation of the medium-term flux of the filter membrane is not higher than 20%, which can ensure that the filter membrane has a more stable and higher flux when filtering high-concentration protein feed liquid. This may be because as the pore structure of the filter membrane is gradually blocked, and the gradual blockage of the pore structure means a further increase in the resistance of the filter membrane to the feed liquid, and naturally it can withstand a greater feed liquid pressure. Therefore, as the filtration process proceeds, the pressure borne by the filter membrane gradually increases. If the filter membrane cannot withstand the gradually increasing pressure, the pore structure of the filter membrane will gradually collapse as the filtration time prolongs. Combined with the already higher protein retention rate, it will lead to a rapid decline in the flux of the filter membrane. The relative deviation of the medium-term flux of the filter membrane not being higher than 20% indicates that although the flux of the filter membrane decreases as the filtration time prolongs, the decrease amplitude is relatively low, and the filter membrane has sufficient pressure resistance to ensure that no obvious pore structure collapse occurs as the pressure borne by the filter membrane increases, so as to have a relatively high and stable flux.

[0063] In this application, the relative deviation of the medium-term flux = |measured value - average value| / average value × 100%. In the above formula, the average value refers to the average value of the flux data when the filtration time of the filter membrane is 100 min and the flux data when the filtration time is 200 min, and the measured value is the flux data when the filtration time of the filter membrane is 100 min or the flux data when the filtration time is 200 min.

[0064] Optionally, the relative deviation of the long-term flux of the filter membrane is not higher than 30%. The relative deviation of the long-term flux is the relative deviation of the flux data when the filtration time t is 100 min and the flux data when the time is 300 min when the protein concentration n in the feed liquid filtered by the filter membrane is 50 g / L.

[0065] By adopting the above technical solution, similar to the relative deviation of the medium-term flux of the filter membrane, the relative deviation of the long-term flux of the filter membrane is controlled not to be higher than 30%, indicating that even when the filter membrane filters a high-concentration protein feed liquid with a concentration as high as 50 g / L, the filter membrane can still ensure that no obvious pore structure collapse occurs when the filtration time reaches 300 min, so as to have a relatively high and stable flux.

[0066] In this application, the relative deviation of the long-term flux = |measured value - average value| / average value × 100%. In the above formula, the average value refers to the average value of the flux data when the filtration time of the filter membrane is 100 min and the flux data when the filtration time is 300 min, and the measured value is the flux data when the filtration time of the filter membrane is 100 min or the flux data when the filtration time is 300 min.

[0067] Optionally, the long-term flux change gradient of the filter membrane is not greater than 3LMH / 100min, and the long-term flux change gradient is the ratio of the difference between the flux data at a filtration time t of 100min and the flux data at a filtration time t of 300min when the protein concentration n of the filter membrane in the filtered liquid is 50g / L to the filtration time.

[0068] By adopting the above technical solution, many factors affect the membrane flux, such as the aforementioned membrane pressure resistance and the membrane's adsorption rate of protein in the feed liquid. The membrane's long-term flux gradient can, to a certain extent, comprehensively characterize the membrane's pressure resistance and the impact of factors such as the protein adsorption rate on the membrane flux decay rate. The membrane's low long-term flux gradient, combined with the membrane's low water flux data, means that the membrane not only has a low protein adsorption rate but also has good pressure resistance. This ensures that the membrane maintains a stable and high flux even when used to filter high-concentration protein feed liquids with a protein concentration of up to 50g / L.

[0069] It can be understood that the long-term capacity change gradient of the filter membrane is no more than 3LMH / 100min, which means that the difference between the flux data when the filtration time is 100min and the flux data when the filtration time is 300min is no more than 6LMH (for a filtration time of 200min).

[0070] Optionally, when the protein concentration in the filtered liquid is 50 g / L, the time for the flux to decay by 75% is not less than 360 min, and the T 360 Not less than 8LMH@30psi.

[0071] By adopting the above technical solution, it is generally believed that when performing virus removal filtration, the filtration endpoint is when the flux of the filter membrane decays by 75% (the flux retains 25%). In this application, the filtration endpoint time of the filter membrane is not less than 360 minutes, and when the filtration is applied for 360 minutes, the flux of the filter membrane can still be maintained at not less than 8LMH@30psi. This indicates that as the filtration progresses, the membrane pore structure of the filter membrane does not experience obvious clogging, and still has a higher flux than commercially available cellulose virus removal membranes.

[0072] Optionally, the PMI average pore size of the filter membrane is not greater than 30 nm and not less than 15 nm, and the SEM average pore size of the liquid inlet surface is greater than the SEM average pore size of the liquid outlet surface.

[0073] Optionally, the PMI average pore size of the filter membrane is not greater than 25 nm; further optionally, the PMI average pore size of the filter membrane is not greater than 23 nm; further optionally, the PMI average pore size of the filter membrane is not greater than 22 nm.

[0074] By adopting the above technical solution, since the existing cellulose virus removal membrane has a low flux when used to filter high-concentration protein liquid, in order to increase the flux of the filter membrane, the general practice is to increase the PMI average pore size of the filter membrane. Although the increase in the PMI average pore size often leads to a decrease in the virus retention capacity of the filter membrane, it is expected that the flux of the filter membrane will increase accordingly.

[0075] However, the inventors of the present application unexpectedly discovered that, for the specific high-concentration protein liquid filtration working conditions in this application, compared to the generally known method of increasing the PMI average pore size of the filter membrane, reducing the PMI average pore size of the filter membrane can not only ensure that the filter membrane has a higher virus retention capacity, but also enable the filter membrane to have a higher flux under specific working conditions. This may be because a lower PMI average pore size often means that the filter membrane has a higher density. Within a certain range, the effect of the reduction in the porosity of the filter membrane on the improvement of the filter membrane's pressure resistance on the filter membrane flux is greater than the effect of the reduction in the porosity of the filter membrane on the filter membrane flux caused by the increase in the liquid resistance. Therefore, unlike general cognition, the present application can enable the filter membrane to have a higher flux when used to filter high-concentration protein liquid by controlling the PMI average pore size of the filter membrane to be no more than 30nm, and more preferably, no more than 25nm or even no more than 22nm.

[0076] In summary, for the special high-concentration protein solution virus removal filtration condition, the high-concentration protein solution flux of the filter membrane first increases continuously with the increase of the PMI average pore size, and then decreases; rather than the generally known continuous increase with the increase of the PMI average pore size. Therefore, in this application, by specifically selecting a filter membrane with a PMI average pore size of 15 to 39 nm, it is possible to ensure a higher flux when the membrane is filtering high-concentration protein solutions.

[0077] In the present application, the PMI average pore size of the filter membrane can be measured by a PMI pore size tester, and the test liquid used is a Galwick standard test liquid with a surface tension of 15.9 dynes / cm.

[0078] Optionally, the porous body consists of a cellulose layer; or

[0079] The porous body is obtained by compounding a cellulose layer and a support layer, and a surface of the cellulose layer facing away from the support layer is a liquid outlet surface.

[0080] By adopting the above technical solution, the filter membrane can be a pure cellulose filter membrane composed of a cellulose layer, or a composite filter membrane composed of a cellulose layer and a support layer that can be used to further improve the strength of the filter membrane.

[0081] In a second aspect, the present application provides a preparation process for a cellulose virus removal filter membrane, which adopts the following technical solution:

[0082] A preparation process of a cellulose virus removal filter membrane comprises the following steps:

[0083] S1, preparing a casting solution, preparing a first casting solution, wherein the first casting solution includes a cellulose film-forming polymer and a casting good solvent;

[0084] S2, casting to form a film, casting the first casting liquid onto the carrier to obtain a liquid film;

[0085] S3, pretreatment, placing the liquid film in a pretreatment bath for pretreatment to obtain a pretreated film;

[0086] S4, curing, placing the pretreated film in a coagulation bath for phase separation curing to obtain a primary film;

[0087] S5, hydrolysis regeneration, placing the primary membrane in a regeneration bath for hydrolysis to obtain a regenerated cellulose membrane, wherein the regeneration bath is a sodium hydroxide aqueous solution with a concentration of 0.01 to 1 mol / L, and a primary hydrolysis is performed first and then a secondary hydrolysis is performed, wherein the temperature of the regeneration bath during the primary hydrolysis is 60 to 80° C., the primary hydrolysis time is 10 to 30 minutes, and the temperature of the regeneration bath during the secondary hydrolysis is 30 to 40° C., and the secondary hydrolysis time is 40 to 150 minutes;

[0088] S6. Cross-linking treatment: placing the regenerated cellulose membrane in a cross-linking agent solution for cross-linking treatment, the cross-linking time is 300-700 min, the cross-linking temperature is 20-80°C, the concentration of sodium hydroxide in the cross-linking agent solution is 0.05-1 mol / L, the cross-linking agent is at least one of polyglycidyl ether, epichlorohydrin, adipic acid, succinic anhydride, hexamethylene diisocyanate, and maleic anhydride, and the concentration of the cross-linking agent in the cross-linking agent solution is 0.5-2 mol / L.

[0089] By adopting the above technical solution, in the hydrolysis and regeneration step, not only the process of hydrolyzing the cellulose film-forming polymer to obtain regenerated cellulose occurs; regenerated cellulose is prone to alkaline hydrolysis and oxidative degradation under alkaline and high temperature conditions. Due to the degradation reaction of the glycosidic bonds of the cellulose molecular chain breaking, low molecular weight cellulose will be generated, which will cause the strength of the obtained virus removal membrane to decrease. However, if the degree of hydrolysis of the cellulose film-forming polymer to regenerated cellulose is too low, it will affect the hydrophilic properties of the virus removal membrane finally obtained, and ultimately affect the protein yield of the virus removal membrane. Obviously, in the hydrolysis and regeneration process, how to ensure that the cellulose film-forming polymer is fully hydrolyzed into regenerated cellulose to ensure the hydrophilicity of the virus removal, while the regenerated cellulose is less hydrolyzed into low molecular weight cellulose, is a more difficult problem to solve.

[0090] The inventors of this application discovered that when the primary membrane obtained by phase separation solidification is hydrolyzed and regenerated, a special secondary hydrolysis process is adopted, combining a relatively short time of high-temperature primary hydrolysis with a relatively long time of low-temperature secondary hydrolysis, so that the filter membrane can have a higher flux when used to filter high-concentration protein liquid.

[0091] This may be because the difficulty of ensuring that the cellulose film-forming polymer is hydrolyzed to obtain regenerated cellulose is different from the difficulty of further hydrolyzing the regenerated cellulose. When the regenerated membrane is subjected to a hydrolysis and regeneration process, it is always more inclined to first hydrolyze the cellulose film-forming polymer to obtain regenerated cellulose, and then further hydrolyze the regenerated cellulose. Among them, in the early stage of hydrolysis and regeneration, due to the high content of cellulose film-forming polymer in the primary membrane, it is more inclined to first hydrolyze the cellulose film-forming polymer to obtain regenerated cellulose. Therefore, a short-term high-temperature hydrolysis can ensure that the cellulose film-forming polymer is quickly hydrolyzed to obtain regenerated cellulose. As the hydrolysis reaction proceeds, the proportion of regenerated cellulose in the primary membrane gradually increases. If the alkaline and high-temperature reaction environment is still maintained, although the reaction of hydrolyzing the film-forming polymer to obtain regenerated cellulose will still proceed, further hydrolysis of the regenerated cellulose will inevitably occur, resulting in a decrease in the strength of the obtained virus removal membrane. Based on this, after a short-term high-temperature primary hydrolysis, a further specific long-term low-temperature secondary hydrolysis is required. By controlling the lower reaction temperature, the possibility of cellulose alkaline hydrolysis and oxygen degradation can be greatly reduced (the temperature is low, and cellulose is difficult to undergo alkaline hydrolysis and oxygen degradation, but the hydrolysis of cellulose film-forming polymers to regenerated cellulose can still proceed), thereby ensuring a high hydrolysis rate of cellulose film-forming polymers, thereby ensuring that the final virus removal product not only has good hydrophilicity, but also has high strength.

[0092] Furthermore, because regenerated cellulose has a relatively soft texture, the strength of the resulting virus removal membrane can be further improved by cross-linking the regenerated cellulose membrane. However, cross-linking inevitably clogs the membrane pore structure, resulting in a decrease in the membrane's porosity and / or pore size. As mentioned above, it is generally believed that although the strength of the virus removal membrane will be improved after cross-linking, its flux will inevitably decrease.

[0093] However, the inventors of this application found that, in fact, when polyglycidyl ether, epichlorohydrin, organic acid or organic anhydride is used as a cross-linking agent, within a certain cross-linking time range, the longer the cross-linking time (that is, the higher the degree of cross-linking), the virus removal membrane has a higher flux when filtering a high-concentration protein liquid. This is quite unexpected. It is generally believed that as the degree of cross-linking increases, the pore structure size in the filter membrane continues to decrease, and the resistance of the filter membrane to the liquid continues to increase, resulting in a gradual decrease in flux. However, the polyglycidyl ether specifically used in the application as a cross-linking agent can attach to and cross-link the regenerated cellulose fibers, thereby reinforcing the fiber skeleton structure of the regenerated cellulose membrane to improve the strength of the obtained virus removal membrane. The increase in the strength of the virus removal membrane, within a certain range, contributes more to the improvement of the filter membrane flux than the negative impact of the decrease in the pore size of the virus removal membrane on the flux improvement, so that the virus removal membrane has a high flux beyond general cognition.

[0094] Optionally, the polyglycidyl ether is at least one of diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol triglycidyl ether;

[0095] In step S6, the ambient pressure is maintained at 0.5 to 0.8 bar during the cross-linking process.

[0096] By adopting the above technical solution, applying an appropriate small negative pressure during the cross-linking treatment can ensure that the cross-linking agent can better penetrate into the pore structure of the regenerated cellulose membrane, thereby achieving a sufficient cross-linking reinforcement effect.

[0097] Optionally, in step S3, the pretreatment bath comprises a pretreatment good solvent and a pretreatment non-solvent, and the mass proportion of the pretreatment non-solvent in the pretreatment bath is 5-20%, and the temperature of the pretreatment bath is 30-40° C.;

[0098] In step S4, the temperature of the coagulation bath is not higher than 30° C., the coagulation bath comprises a coagulation good solvent and a coagulation non-solvent, and the mass proportion of the coagulation non-solvent in the coagulation bath is 85-95%.

[0099] By adopting the above technical solution, the present application also specially adopts a low-temperature coagulation phase separation process, which can also improve the strength of the prepared virus removal membrane, thereby reducing the deformation of the filter membrane when filtering high-concentration protein liquid, so as to obtain a higher flux.

[0100] This may be because the increase in coagulation bath temperature will accelerate the double diffusion rate, the polymer solidification effect is too intense, and the cellulose macromolecules have not yet had time to crystallize and orient themselves. Therefore, the cellulose macromolecules in the final virus removal membrane have low crystallinity, disordered arrangement, loose network structure, and low orientation, resulting in low strength of the virus removal membrane, excessive deformation when filtering high-concentration protein liquid, and a significant decrease in flux.

[0101] Optionally, the film casting good solvent, pretreatment good solvent and solidification good solvent are at least one of acetone, dioxane, N,N-dimethylacetamide, N-methylpyrrolidone, acetic acid, propionic acid, butyric acid and valeric acid;

[0102] The cellulose polymer is at least one of cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose acetate phthalate, cellulose acetate butyrate, and cellulose acetate propionate.

[0103] Optionally, in step S1, a second casting solution having a lower solid content than the first casting solution is further prepared, and both the first casting solution and the second casting solution include a cellulose film-forming polymer and a casting good solvent;

[0104] In the step S2, the first casting liquid and the second casting liquid are sequentially cast onto the carrier to obtain a liquid film.

[0105] By adopting the above technical solution, compared with the single-layer casting process, the double-layer casting process controls the different solid content, scraping thickness, etc. of the two layers of casting liquid, and controls the proportion of the membrane body with a large pore structure and the proportion of the membrane body with a small pore structure in the filter membrane. By further casting a second casting liquid with a lower solid content on the first casting liquid, the second casting liquid with a lower solid content is more likely to form a porous membrane structure with a larger pore size, which can better form a pre-filtration effect on large particles of impurities in the feed liquid, and is therefore more suitable for more complex systems. Therefore, the choice of using a single-layer casting process or a double-layer casting process can be based on actual needs.

[0106] Optionally, the solid content of the first casting solution is 15-30%, and the solid content of the second casting solution is 5-20%;

[0107] In the step S2, the scraping speed of the first casting liquid is lower than the scraping speed of the second casting liquid, and the scraping speed of the second casting liquid is 1-3 m / min.

[0108] By employing the above-mentioned technical solution, it is noteworthy that the inventors of this application have also discovered that the scraping speed of the first and second casting solutions during the membrane formation process also has a certain impact on the performance of the final virus removal membrane. For example, within a certain range, appropriately increasing the scraping speed can improve the strength of the resulting virus removal membrane, thereby reducing membrane deformation when filtering high-concentration protein solutions, thereby achieving higher flux.

[0109] This may be due to the fact that increasing the scraping speed significantly increases the film's tensile strength and elongation at break. This is because, under the action of external forces, macromolecular chains, segments, and crystallites inevitably exhibit varying degrees of orientation. The force applied by the scraper is proportional to the scraping speed. As the scraping speed increases, the force applied by the scraper also increases, leading to an increase in the polymer material's degree of orientation. The number of chemical bonds per unit cross-section in the direction of the covalently linked molecular chains increases significantly, significantly enhancing the tensile strength.

[0110] Optionally, in step S2, after the first casting solution and the second casting solution are applied to the carrier to obtain a liquid film, a support layer is covered on the liquid film;

[0111] The support layer is one of PVDF microporous membrane, PES microporous membrane, PTFE microporous membrane, Nylon microporous membrane, cellulose microporous membrane, polyolefin microporous membrane or non-woven substrate.

[0112] By adopting the above-mentioned technical solution, the introduction of a microporous membrane support layer or a nonwoven support layer can further improve the pressure resistance of the filter membrane. Because the pore structure of the microporous membrane support layer or the nonwoven support layer is significantly larger than that of the cellulose layer formed by the casting solution, the introduction of the support layer has a relatively small impact on the flux of the filter membrane. Of course, while the introduction of the support layer can improve the overall pressure resistance of the filter membrane, if the strength of the cellulose layer in the filter membrane is too low, the cellulose layer itself may still undergo significant deformation when used to filter high-concentration protein solutions.

[0113] In a third aspect, the present application provides the application of the aforementioned cellulose virus removal filter membrane for virus removal filtration in a feed liquid with a protein concentration higher than 20 g / L.

[0114] In summary, this application includes at least one of the following beneficial technical effects:

[0115] 1. Unlike the commonly accepted view that increasing the water flux of a membrane can improve the flux of a high-concentration protein solution, the membrane in this application counterintuitively controls the membrane to have a lower water flux and a higher virus retention capacity, thereby enabling the membrane to have a higher flux when filtering a high-concentration protein solution.

[0116] 2. The flux of the filter membrane in this application is less attenuated when filtering high-concentration protein solutions than when filtering deionized water. This indicates that the membrane pore structure of the filter membrane with a lower water flux does not undergo excessive deformation even when filtering high-viscosity, high-concentration protein solutions, thereby ensuring a higher flux when filtering high-concentration protein solutions.

[0117] 3. The filter membrane of the present application has a relatively low medium-term flux relative deviation and a low long-term flux relative deviation, ensuring that even as the filtration time increases and the pressure on the filter membrane increases further, no significant pore structure collapse occurs, thereby achieving a relatively high and stable flux;

[0118] 4. The filter membrane of the present application has a smaller PMI average pore size through counterintuitive control, which can enable the filter membrane to have a higher flux when used to filter high-concentration protein liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0119] FIG1 is a curve showing the change in flux over time when the virus removal membrane prepared in Example 1 of the present application is used to filter an IVIG solution with a protein concentration of 50 g / L.

[0120] FIG2 is a curve showing the change in flux over time when the virus removal membrane prepared in Example 2 of the present application is used to filter an IVIG solution with a protein concentration of 50 g / L.

[0121] FIG3 is a curve showing the change in flux over time when the virus removal membrane prepared in Example 3 of the present application is used to filter an IVIG solution with a protein concentration of 50 g / L. DETAILED DESCRIPTION

[0122] The present application is further described in detail below with reference to Figures 1 to 3 .

[0123] The embodiments of the present application disclose a cellulose virus removal filter membrane, a preparation process, and applications thereof.

[0124] Example 1

[0125] This embodiment discloses a cellulose virus removal filter membrane, the preparation process of which includes the following process steps:

[0126] S1. Preparation of casting liquids: preparing a first casting liquid and a second casting liquid respectively. The first casting liquid and the second casting liquid both include a cellulose film-forming polymer and a casting good solvent. In this embodiment, the film-forming polymers in the first casting liquid and the second casting liquid are the same, both are cellulose diacetate (or called cellulose diacetate, CA), and the casting good solvents in the first casting liquid and the second casting liquid are also the same, both are N,N-dimethylacetamide. In addition, in this embodiment, the solid content of the first casting liquid is 23 wt %, and the solid content of the second casting liquid is lower than that of the first casting liquid. Specifically, the solid content of the second casting liquid is 12 wt %.

[0127] S2, casting into a film, first, the prepared first casting liquid is scraped onto a carrier by scraping, and the carrier can be a steel belt or a film such as a PET release film. In this embodiment, a steel belt is selected as the carrier, and the scraping speed of the first casting liquid is 1.5 m / min; after the first casting liquid is scraped, the second casting liquid is scraped onto the top of the first casting liquid, and the scraping speed of the second casting liquid is 2 m / min. After the first casting liquid and the second casting liquid are cast onto the carrier in sequence, a nylon microporous membrane with a nominal pore size of 0.22 μm and a thickness of 70 μm is covered on the top of the second casting liquid to obtain a liquid film.

[0128] S3. Pretreatment: placing the liquid film in a pretreatment bath for pretreatment. The pretreatment time is 20 seconds, and the temperature of the pretreatment bath is maintained at 35°C. After the pretreatment is completed, a pretreated film is obtained. In this embodiment, the pretreatment bath uses a mixed system of a pretreatment good solvent and a pretreatment non-solvent, and the mass proportion of the pretreatment non-solvent in the pretreatment bath is 13%. The pretreatment non-solvent is deionized water, and the pretreatment good solvent is N,N-dimethylacetamide.

[0129] S4. Curing: Place the pretreated membrane in a coagulation bath until the pretreated membrane is completely phase-separated and solidified to obtain a primary membrane. The temperature of the coagulation bath needs to be controlled at 15°C. The coagulation bath includes a coagulation good solvent and a coagulation non-solvent, and the mass proportion of the coagulation non-solvent in the coagulation bath is 90%. The coagulation non-solvent is deionized water, and the coagulation good solvent is N,N-dimethylacetamide.

[0130] S5, hydrolysis regeneration, the primary membrane obtained after sufficient phase separation and solidification is placed in a regeneration bath for hydrolysis treatment to obtain a regenerated cellulose membrane. During hydrolysis, a primary hydrolysis is performed first and then a secondary hydrolysis is performed. During the primary hydrolysis, the temperature of the regeneration bath is controlled to 70°C, and the primary hydrolysis time is controlled to 20 minutes. During the secondary hydrolysis, the temperature of the regeneration bath is controlled to 35°C, and the secondary hydrolysis time is controlled to 90 minutes. Both the primary and secondary hydrolysis baths use a sodium hydroxide aqueous solution with a concentration of 0.5 mol / L.

[0131] S6, cross-linking treatment, placing the regenerated cellulose membrane obtained after hydrolysis and regeneration in a cross-linking agent solution for cross-linking treatment, and obtaining a cellulose virus removal filter membrane after cross-linking treatment. The concentration of the cross-linking agent polyethylene glycol diglycidyl ether in the cross-linking agent solution is 1.3 mol / L, and the cross-linking agent is also added with sodium hydroxide at a concentration of 0.5 mol / L. The cross-linking time is controlled to be 120 minutes, and the temperature of the cross-linking agent solution is controlled to be 65°C. In order to promote better penetration of the cross-linking agent into the membrane pore structure, in this embodiment, the environment during cross-linking is controlled to be negative pressure, specifically, the ambient pressure is 0.65 bar.

[0132] Example 2 to Example 7

[0133] The main difference between Example 2 to Example 7 is that different casting solutions are used to prepare the virus removal membranes and different membrane-making process parameters are adopted. See Table 1 for details.

[0134] Specifically, the virus removal membranes in Examples 2 and 4 lack a support layer structure. Therefore, in step S2, only the first and second casting solutions need to be sequentially cast onto the carrier, eliminating the need for a subsequent support layer coating step. In contrast, the virus removal membranes in Examples 3 and 5-7 all have a support layer structure. The support layer used in Examples 5-7 is the same as in Example 1: a nylon microporous membrane with a nominal pore size of 0.22 μm and a thickness of 70 μm. In contrast, Example 3 uses a non-woven fabric layer with a nominal pore size of 0.45 μm and a thickness of 60 μm.

[0135] Example 8 to Example 9

[0136] The main difference between Examples 8 and 9 and the previous examples is that they all utilize a single-layer casting process. Specifically, in step S2, only the first casting solution is cast onto the carrier to produce the liquid film, without the subsequent second casting process. Furthermore, the virus removal membrane in Example 8 includes a support layer structure, and the support layer used is the same as in Example 1: a nylon microporous membrane with a nominal pore size of 0.22 μm and a thickness of 70 μm. The virus removal membrane in Example 9, on the other hand, lacks a support layer structure. Specific process parameters are detailed in Table 1.

[0137] Comparative Example 1

[0138] Comparative Example 1 is a commercially available Planova manufactured by Asahi Kasei Corporation. TM 20N, and the membrane is a hollow cellulose virus removal membrane.

[0139] Comparative Example 2

[0140] Comparative Example 2 differs from Example 1 primarily in the solids content of the casting solution and the use of a longer, low-temperature hydrolysis process rather than a secondary hydrolysis process during the hydrolysis and regeneration step. Furthermore, this comparative example employed a longer crosslinking time and a higher crosslinker concentration to ensure the resulting virus removal membrane possesses excellent pressure resistance. Specific process parameters are detailed in Table 1.

[0141] Comparative Example 3

[0142] Comparative Example 3 differs from Example 1 primarily in the solids content of the casting solution and the use of a longer, high-temperature hydrolysis process rather than a secondary hydrolysis process in the hydrolysis regeneration step. Furthermore, this comparative example employed a shorter crosslinking time and lower crosslinker concentration to minimize clogging of the virus removal membrane pore structure. Specific process parameters are detailed in Table 1.

[0143] Table 1 Casting solution and process parameters of each embodiment and comparative example

[0144] The parameters of each embodiment and comparative example are detailed in Table 2.

[0145] Table 2 Parameters of Examples and Comparative Examples

[0146] In Table 2, Planova in Comparative Example 1 TM The official nominal operating pressure of 20N is 14psi, so its test pressure is 14psi, and its water flux needs to be converted from 14psi to the theoretical flux at 30psi. The calculation method is T 20N ×30 / 14, where T 20N It refers to the water flux of the membrane measured at 14 psi.

[0147] In Table 2, the tensile strength at break of each embodiment can be measured by a universal tensile tester, and the tensile strength at break of embodiment 1 is used as a benchmark to calculate the ratio of the tensile strength at break of each embodiment to that of embodiment 1.

[0148] in conclusion

[0149] By comparing the technical solutions and performance parameters of Example 1 and Examples 3 to 7, it is not difficult to find that for the virus removal membrane with a support layer, the filtration flux of the high-concentration protein liquid of the virus removal membrane shows a trend of gradually increasing and then decreasing with the increase of water flux, which is quite unexpected.

[0150] By further comparing the technical solutions and performance parameters of Examples 1, 3, and 5, it can be found that although Example 5 has a water flux similar to that of Example 3, the virus removal membrane in Example 5 has a significantly lower stable flux and a higher flux attenuation coefficient. This may be because the hydrolysis degree of the virus removal membrane in Example 5 is significantly higher than that of the virus removal membrane in Example 3, while the cross-linking degree is lower than that of the virus removal membrane in Example 3. Both excessively high hydrolysis degree and excessively low cross-linking degree will lead to a decrease in the strength of the virus removal membrane, resulting in the virus removal membrane in Example 5 having a suboptimal high-concentration protein filtration flux compared to the virus removal membrane in Example 3. Therefore, when the water flux of the virus removal membrane is high, appropriately reducing the water flux of the virus removal membrane is beneficial for improving the high-concentration protein filtration flux of the virus removal membrane.

[0151] By further comparing the technical solutions and performance parameters of Example 6 and Example 7, it is not difficult to find that for the virus removal membrane with a support layer, when the water flux of the virus removal membrane is low, the high-concentration protein feed filtration flux of the virus removal membrane shows an upward trend with the increase of water flux. This shows that although the strength of the virus removal membrane can be further improved by controlling the membrane manufacturing process parameters, as the strength of the virus removal membrane gradually increases, its effect on the high-concentration protein filtration flux has a marginal diminishing effect. In contrast, the resistance of the virus removal membrane to the feed continues to increase, and its effect on the high-concentration protein filtration flux increases accordingly. Therefore, when the water flux of the virus removal membrane is low, appropriately increasing the water flux of the virus removal membrane is beneficial to improving the high-concentration protein filtration flux of the virus removal membrane.

[0152] By comparing the technical solutions and performance parameters of Example 2 and Example 4, it is not difficult to find that for the virus removal membrane without a support layer, when the water flux of the virus removal membrane is high, the filtration flux of the high-concentration protein liquid of the virus removal membrane shows a downward trend with the increase of water flux, which is very unexpected. This may be related to the fact that the virus removal membrane of Example 4 has a lower strength than the virus removal membrane of Example 2 and is more prone to deformation (lower tensile strength at break). In addition, since the virus removal membrane in Example 4 does not have a support layer for reinforcement and has poor self-supporting performance, the flux of the virus removal membrane has a more obvious decline with the extension of the filtration time, which is reflected in the long-term deviation of the virus removal membrane reaching 40.2%, and the flux gradient reaching 4.05LMH / 100min. Therefore, appropriately reducing the water flux of the filter membrane is beneficial to improving the flux stability of the virus removal membrane when filtering high-concentration protein liquid.

[0153] Comparing the technical solutions and performance parameters of Examples 8 and 9 reveals that for single-layer virus removal membranes, regardless of whether a support layer is included, when the water flux of the virus removal membrane is within the preferred range, the protein flux attenuation coefficient is low, and the flux of high-concentration protein solutions is high. Furthermore, the introduction of a support layer reduces the protein flux attenuation coefficient of the virus removal membrane.

[0154] A further comparison of the technical solutions and performance parameters of Example 1 and Example 8 reveals that, given similar water fluxes, the virus removal membrane obtained by single-layer casting exhibits a higher flux of excess protein solution within the membrane. This is likely due to the lack of a second casting solution with a lower solids content compared to the virus removal membrane obtained by double-layer casting. Consequently, the large-diameter pore structure within the cellulose layer is less common, making localized deformation less likely. Similar trends were observed in Examples 2 and 9.

[0155] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A cellulose virus removal filter membrane, characterized in that: It comprises a porous body, wherein the porous body has a liquid inlet surface for the feed liquid to enter and a liquid outlet surface for the feed liquid to flow out; The water flux T of the membrane 水 Not higher than 85LMH@30psi and not lower than 30LMH@30psi; The stable flux T of the membrane 240 Not less than 6LMH@30psi, the stable flux T 240 The flux data of the membrane when the protein concentration n in the filtered liquid is 50 g / L and the filtration time t is 240 min; The retention capacity of the filter membrane for PP7 bacteriophage satisfies LRV≥5@(0.1 g / L, IVIG).

2. A cellulose virus removal filter membrane according to claim 1, characterized in that: The water flux T of the membrane 水 Not higher than 80LMH@30psi and not lower than 35LMH@30psi; The stable flux T of the membrane 240 Not less than 10LMH@30psi; The retention capacity of the filter membrane for PP7 bacteriophage satisfies LRV≥5.5@(0.1 g / L, IVIG).

3. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The top wash LRV retention rate of the filter membrane is not less than 0.

85.

4. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The long-term average flux of the filter membrane is 8-30LMH@30psi, and the long-term average flux is the average value of the flux when the protein concentration of the filter membrane in the filtered liquid is 50g / L and the filtration time t is 100min to 300min.

5. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The protein flux attenuation coefficient X of the filter membrane 50 @100min is not higher than 85%, the protein flux attenuation coefficient of the filter membrane is X 50 @100min is obtained by the following formula: Xn=(1-T t / T 水 )×100%; In the above formula, Xn is the protein flux attenuation coefficient when the protein concentration in the feed solution is n, T t is the flux data of the filter membrane when the protein concentration in the filtrate is n and the filtration time is t, in LMH; X 50 @100min refers to the protein flux attenuation coefficient when the protein concentration n in the feed solution is 50g / L and the filtration time t is 100min.

6. A cellulose virus removal filter membrane according to claim 5, characterized in that: The protein flux attenuation coefficient X of the filter membrane 50 @100min is not higher than 80%, the T of the filter membrane 100 Not less than 10LMH@30psi.

7. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The relative deviation of the mid-term flux of the filter membrane is no more than 20%, and the relative deviation of the mid-term flux is the relative deviation between the flux data when the filtration time t is 100 min and the flux data when the filtration time t is 200 min when the protein concentration n in the filtration liquid of the filter membrane is 50 g / L.

8. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The long-term flux relative deviation of the filter membrane is no more than 30%, and the long-term flux relative deviation is the relative deviation between the flux data when the filtration time t is 100 min and the flux data when the filtration time t is 300 min when the protein concentration n in the filtration liquid of the filter membrane is 50 g / L.

9. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The long-term flux change gradient of the filter membrane is no more than 3LMH / 100min, and the long-term flux change gradient is the ratio of the difference between the flux data at a filtration time t of 100min and the flux data at a filtration time t of 300min when the protein concentration n of the filter membrane in the filtered liquid is 50g / L to the filtration time.

10. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: When the protein concentration in the filtered liquid is 50 g / L, the time for the flux to decay by 75% is not less than 360 min. 360 Not less than 8LMH@30psi.

11. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The PMI average pore size of the filter membrane is not greater than 30 nm and not less than 15 nm, and the SEM average pore size of the liquid inlet surface is greater than the SEM average pore size of the liquid outlet surface.

12. A cellulose virus removal filter membrane according to claim 1 or 2, characterized in that: The porous body consists of a cellulose layer; or, The porous body is obtained by compounding a cellulose layer and a support layer, and a surface of the cellulose layer on a side facing away from the support layer is a liquid outlet surface.

13. The process for preparing the cellulose virus removal filter membrane according to any one of claims 1 to 12, characterized in that: The process steps include: S1, preparing a casting solution, preparing a first casting solution, wherein the first casting solution comprises a cellulose film-forming polymer and a casting good solvent; S2, casting to form a film, casting the first film casting liquid onto the carrier to obtain a liquid film; S3, pretreatment, placing the liquid film in a pretreatment bath for pretreatment to obtain a pretreated film; S4, solidification, placing the pretreated film in a solidification bath for phase separation solidification to obtain a primary film; S5, hydrolysis regeneration, placing the primary membrane in a regeneration bath for hydrolysis to obtain a regenerated cellulose membrane, wherein the regeneration bath is a sodium hydroxide aqueous solution with a concentration of 0.01-1 mol / L, and a primary hydrolysis is performed first and then a secondary hydrolysis is performed, wherein the temperature of the regeneration bath during the primary hydrolysis is 60-80°C, the primary hydrolysis time is 10-30 min, and the temperature of the regeneration bath during the secondary hydrolysis is 30-40°C, and the secondary hydrolysis time is 40-150 min; S6. Cross-linking treatment: placing the regenerated cellulose membrane in a cross-linking agent solution for cross-linking treatment, the cross-linking time is 300-700 min, the cross-linking temperature is 20-80°C, the sodium hydroxide concentration in the cross-linking agent solution is 0.05-1 mol / L, the cross-linking agent is at least one of polyglycidyl ether, epichlorohydrin, adipic acid, succinic anhydride, hexamethylene diisocyanate, and maleic anhydride, and the concentration of the cross-linking agent in the cross-linking agent solution is 0.5-2 mol / L.

14. The process for preparing the cellulose virus removal filter membrane according to claim 13, characterized in that: The polyglycidyl ether is at least one of diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and glycerol triglycidyl ether; In step S6, the ambient pressure is maintained at 0.5-0.8 bar during the cross-linking process.

15. The process for preparing the cellulose virus removal filter membrane according to claim 13, characterized in that: In step S3, the pretreatment bath includes a pretreatment good solvent and a pretreatment non-solvent, and the mass proportion of the pretreatment non-solvent in the pretreatment bath is 5-20%, and the temperature of the pretreatment bath is 30-40° C.; In the step S4, the temperature of the coagulation bath is not higher than 30°C, the coagulation bath comprises a coagulation good solvent and a coagulation non-solvent, and the mass proportion of the coagulation non-solvent in the coagulation bath is 85-95%.

16. The process for preparing the cellulose virus removal filter membrane according to claim 13, characterized in that: The film casting good solvent, pretreatment good solvent and solidification good solvent are at least one of acetone, dioxane, N,N-dimethylacetamide, N-methylpyrrolidone, acetic acid, propionic acid, butyric acid and valeric acid; The cellulose polymer is at least one of cellulose diacetate, cellulose triacetate, cellulose propionate, cellulose acetate phthalate, cellulose acetate butyrate, and cellulose acetate propionate.

17. The process for preparing the cellulose virus removal filter membrane according to any one of claims 13 to 16, characterized in that: In the step S1, a second casting solution with a lower solid content than the first casting solution is prepared, and both the first casting solution and the second casting solution include a cellulose film-forming polymer and a casting good solvent; In the step S2, the first casting liquid and the second casting liquid are sequentially cast onto the carrier to obtain a liquid film.

18. The process for preparing the cellulose virus removal filter membrane according to claim 17, characterized in that: The solid content of the first casting solution is 15-30%, and the solid content of the second casting solution is 5-20%; In the step S2, the scraping speed of the first casting liquid is lower than the scraping speed of the second casting liquid, and the scraping speed of the second casting liquid is 1-3 m / min.

19. The process for preparing the cellulose virus removal filter membrane according to claim 17, characterized in that: In the step S2, after the first casting liquid and the second casting liquid are applied to the carrier to obtain a liquid film, a support layer is covered on the liquid film; or, In the step S2, after the first casting liquid is scraped onto the carrier to obtain a liquid film, a support layer is covered on the liquid film; The support layer is one of PVDF microporous membrane, PES microporous membrane, PTFE microporous membrane, Nylon microporous membrane, cellulose microporous membrane, polyolefin microporous membrane or non-woven substrate.

20. Use of the cellulose virus removal filter membrane according to any one of claims 1 to 12 for virus removal filtration in a feed liquid with a protein concentration higher than 20 g / L.

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