Method for manufacturing microporous membrane for virus filtration having precisely controlled pore sizes

Abstract

The present invention relates to a method for manufacturing a hydrophilic microporous membrane for virus filtration. Specifically, the hydrophilic microporous membrane is manufactured by performing a hydrophilization treatment without using a crosslinking agent, and the microporous membrane for virus removal thus manufactured has excellent water permeability and protein permeability and exhibits good durability against organic solvents.

Description

Method for manufacturing a microporous membrane for virus filtration with precisely controlled pore size

[0001] The present invention relates to a method for manufacturing a microporous membrane for virus filtration in which the pore size distribution is precisely controlled.

[0002] When preparations containing biopharmaceuticals are administered to the human body, viruses that may be present in the preparation pose a risk of causing serious problems. Therefore, a process to remove viruses is necessary during the manufacturing of biopharmaceuticals. Among these methods, membrane filtration, which physically removes viruses, is an effective technique capable of eliminating viruses without altering useful proteins.

[0003] Virus filtration membranes (microporous membranes) play an essential role in the manufacturing of biopharmaceuticals and the purification and production processes of biological agents. These membranes must effectively remove fine particles, such as viruses, while simultaneously satisfying throughput and selective permeability. To achieve this, the pore size and distribution of the membrane must be designed to precisely match the size and shape of viruses.

[0004] In the manufacturing of separator membranes, processes that improve their physical properties and stability are crucial. Specifically, heat treatment enhances the tensile strength and elongation of the membrane, thereby reducing the likelihood of breakage or deformation during use. This is essential for the stable operation of the membrane, particularly in high-pressure environments. Furthermore, heat treatment strengthens the thermal stability of the membrane, ensuring that its performance is maintained under various temperature conditions.

[0005] The performance of virus filtration membranes is largely dependent on the maximum pore size and the uniformity of the pore size distribution. If the pore size distribution is wide or the maximum pore size is larger than the virus size, there is a higher likelihood that small viruses will pass through without being filtered. Therefore, to guarantee virus removal performance, the membrane must meet specific requirements. First, the maximum pore size must be designed to be smaller than the virus size, and the pore size distribution must be narrowed. Second, uniform heat treatment must be applied throughout the membrane to ensure the precision of the pore structure and the uniformity of performance.

[0006] Conventional heat treatment processes primarily utilize air or steam as heat sources, but these methods have several inherent limitations. First, there is the issue of non-uniformity in heat transfer. Air or steam is prone to localized temperature differences when transferring heat to the membrane surface, making it difficult to achieve uniform heat treatment across the entire membrane. Consequently, the pore size and pore distribution of the membrane are frequently controlled unevenly. Second, existing heat treatment methods have primarily focused on improving the physical strength of the membrane. While this approach may be effective for improving tensile strength and elongation, it has shown limitations in narrowing the pore size distribution or effectively reducing the maximum pore size. As a result, existing methods alone fail to sufficiently meet the performance requirements of applications demanding precise pore control, such as virus removal.

[0007] In conventional membrane manufacturing processes, methods involving heat treatment following immersion in water have been attempted. This approach aimed to improve the physical properties of the membrane by utilizing water's high specific heat and uniform heat transfer characteristics compared to heat sources such as air or steam. Consequently, it demonstrated some success in enhancing the tensile strength and elongation of the membrane, as well as increasing thermal stability. This is considered a significant advancement for maintaining membrane durability under high temperature and high pressure conditions.

[0008] However, these processes have primarily focused on enhancing physical properties, and sufficient technical solutions have not been established for the problem of precisely controlling the pore size and distribution of the membrane. Despite the advantage of heat treatment by immersion in water enabling uniform heat transfer, there has been a lack of attempts to utilize this method at a sophisticated level, such as for controlling pore structure. In particular, there were limitations in ensuring precision by reducing pore size to a level suitable for virus removal or narrowing the pore distribution. To overcome these technical limitations, a new heat treatment process is required that can maintain the physical stability of the membrane while precisely controlling pore size and distribution.

[0009]

[0010] Accordingly, the inventors continued their research and developed a heat treatment method capable of controlling pore size in an efficient and economical manner, thereby compensating for the limitations of existing processes, and arrived at the present invention.

[0011] The objective of the present invention is to provide a method for manufacturing a microporous membrane for virus filtration in which the pore size and distribution are precisely controlled.

[0012] Another objective of the present invention is to provide a hydrophilic microporous membrane for virus filtration manufactured by the above method.

[0013]

[0014] However, the technical problems that the present invention aims to solve are not limited to the purposes mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0015] To solve the above problem, the present invention provides a method for manufacturing a microporous membrane for virus filtration comprising the following steps:

[0016] Dibutyl phthalate (DBP) is added to a molten mixture containing polyvinylidene fluoride (PVDF) resin and dicyclohexyl phthalate (DCHP), and an unsolidified hollow fiber is formed by extruding through a nozzle;

[0017] The above unsolidified hollow fiber is cooled using a liquid refrigerant at 0 to 50 ℃ to obtain a solidified hollow fiber;

[0018] Extract and remove DCHP and DBP from the above-mentioned solidified hollow fiber;

[0019] Wash the hollow fiber from which the above DCHP and DBP have been removed;

[0020] Immerse the above-mentioned washed hollow fibers in water; and

[0021] The hollow fiber immersed in the water above is fixed with a tension control device to a maximum tension of 500 to 950 cN / mm 2 A step of performing heat treatment at a high temperature while maintaining tension.

[0022] The above maximum tension can be measured by the following formula.

[0023]

[0024] In the above equation, F is the tension (cN) and A is the cross-sectional area of ​​the microporous membrane (mm² 2 )lim.

[0025] The step of performing heat treatment at the above high temperature can be performed at 120 to 130 degrees for 1 to 6 hours.

[0026] The above tension adjustment device may be a jig.

[0027] The above-mentioned microporous membrane for virus filtration may have a maximum pore size of 20 to 30 nm.

[0028] The above-mentioned microporous membrane for virus filtration may have a pore size variation coefficient of 2.5 to 5%.

[0029] After the step of performing heat treatment at the above high temperature, a step of drying in a vacuum may be added.

[0030] The method for manufacturing a microporous membrane (separation membrane) for virus removal according to the present invention enables precise control of the pore size and distribution of the separation membrane by using a tension control device during heat treatment when the separation membrane is immersed in water. Accordingly, the present invention provides a separation membrane capable of maximizing virus removal efficiency.

[0031] Furthermore, the method for manufacturing a virus removal membrane according to the present invention simultaneously achieves physical strength and pore structure control, and also enables precise control of pore size and distribution through the uniform transfer of a heat source during the heat treatment process, thereby providing the effect of maximizing the performance of the virus removal membrane.

[0032] By producing biopharmaceuticals and biological preparations using a separation membrane obtained through the economical and efficient separation membrane manufacturing process according to the present invention, high safety and quality can be ensured.

[0033] FIG. 1 is a diagram showing the structure of a length-adjustable jig for heat treatment of a separator applied in one embodiment of the present invention.

[0034] [1] Support frame

[0035] [2] Separator fixing cover

[0036] [3] Length adjustment guide slot

[0037] [4] Adjustment screw

[0038] In one aspect, the present invention relates to a method for manufacturing a microporous membrane for virus filtration comprising the following steps:

[0039] Dibutyl phthalate (DBP) is added to a molten mixture containing polyvinylidene fluoride (PVDF) resin and dicyclohexyl phthalate (DCHP), and an unsolidified hollow fiber is formed by extruding through a nozzle;

[0040] The above unsolidified hollow fiber is cooled using a liquid refrigerant at 0 to 50 ℃ to obtain a solidified hollow fiber;

[0041] Extract and remove DCHP and DBP from the above-mentioned solidified hollow fiber;

[0042] Wash the hollow fiber from which the above DCHP and DBP have been removed;

[0043] Immerse the above-mentioned washed hollow fibers in water; and

[0044] The hollow fiber immersed in the water above is fixed with a tension control device to a maximum tension of 500 to 950 cN / mm 2 A step of performing heat treatment at a high temperature while maintaining tension.

[0045] The above maximum tension can be measured by the following formula.

[0046]

[0047] In the above equation, F is the tension (cN) and A is the cross-sectional area of ​​the microporous membrane (mm² 2 )lim.

[0048] In the present invention, the term “microporous membrane” refers to a microporous hollow fiber membrane and is also referred to as a “separation membrane.” In this specification, “separation membrane” refers to a “microporous membrane.”

[0049] The term “pore size distribution” as used in this invention refers to a concept representing the relative frequency of various pore sizes existing across the entire area of ​​a material, and is an important indicator for evaluating the uniformity of the pore structure within the material. A narrow pore size distribution implies that the pore sizes are relatively uniform. Furthermore, in processes such as hemodialysis, the pore size distribution determines filtration efficiency and flow rate.

[0050] The above PVDF resin is a material with excellent heat resistance and moldability, and is widely used in this technical field for virus removal membranes. In particular, the separation membrane formed through a high-temperature melt mixing and extrusion process provides a structure with high strength and chemical resistance.

[0051] The method for manufacturing a microporous membrane according to the present invention combines a heat treatment process, in which hollow fibers are immersed in water and heated, with a tension control device to not only improve the physical strength of the membrane but also maximize virus removal efficiency through pore size control. The heat treatment process plays a crucial role in enhancing the physical stability and durability of the membrane, while fixation using the tension control device contributes to securing a uniform thickness and structural stability of the membrane. By using water as a heat source medium in the heat treatment process of the membrane, uniform heat treatment is provided to the membrane, thereby enabling precise control of pore size and distribution.

[0052] In this invention, a method is adopted in which a membrane is heated while immersed in water and a tension control device is utilized during heat treatment to precisely manage the shrinkage rate of the membrane. Specifically, by measuring the tension with the tension control device and adjusting the tension based on the maximum tension, the pore size of the membrane can be controlled. Since water has a higher specific heat than air or steam, uniform heat transfer is possible. By immersing the membrane in water and applying a temperature of 120 degrees or higher to uniformly control the pore size (coefficient of variation) of the membrane, the maximum pore size of the membrane can be reduced and the pore size distribution narrowed. Through this, a pore structure optimized for the size and shape of virus particles can be formed while maintaining the physical stability of the membrane, and the virus removal efficiency can be significantly improved.

[0053] The step of performing heat treatment at the above high temperature can be performed at 120 to 130 degrees for 1 to 6 hours. If the temperature and time ranges are exceeded, problems may arise where the desired pore size distribution cannot be obtained and the intrinsic physical properties change.

[0054] The above tension adjustment device may be a jig.

[0055] FIG. 1 is a diagram showing the structure of a length-adjustable jig for heat treatment of a separator. The jig is a device for stably processing the heat treatment process and is designed to fix and contract separator membranes of various lengths. Specifically, the separator membrane support frame (1) is a structure that stably supports the separator membrane and is made of SUS316L, a material that minimizes thermal expansion and oxidation even at high temperatures. The separator membrane fixing cover (2) performs the function of fixing the separator membrane to the support frame (1), and the fixing cover is designed to prevent movement of the separator membrane during heat treatment and to be easily attached and detached. The length-adjustable guide slot (3) is a groove-shaped structure formed on the top of the support frame (1), and the position of the separator membrane fixing cover (2) can be adjusted in the longitudinal direction using an adjustment screw (4). The guide slot (3) provides a length adjustment range to fix separator membranes of various sizes and enables precise adjustment by operating in a sliding manner. The above adjustment screw (4) serves to fix the separator fixing cover (2) to the support frame (1) and move it along the length adjustment guide slot (3). The user can accurately fix separators of various sizes by adjusting the values ​​while tightening and loosening the screw.

[0056] The above-mentioned microporous membrane for virus filtration may have a maximum pore size of 23 to 26 nm.

[0057] The above-described microporous membrane for virus filtration may have a coefficient of variation of 2.5 to 5% for the pore size. Such a narrow pore size distribution demonstrates that the pore size of the separation membrane of the present invention is very uniform.

[0058] After the step of performing heat treatment at the high temperature mentioned above, a vacuum drying step may be added. Vacuum drying is a widely known process in this technical field.

[0059] The separation membrane manufactured according to the present invention exhibits superior water permeability and protein adsorption resistance compared to conventional separation membranes, and demonstrates excellent durability even during long-term use. Due to these characteristics, the separation membrane according to the present invention can be utilized in various industrial fields such as water treatment, pharmaceuticals, and biomedicine.

[0060]

[0061] The present invention is capable of various modifications and may have various embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description below. However, this is not intended to limit the present invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the present invention. In describing the present invention, detailed descriptions of related prior art are omitted if it is determined that such detailed descriptions may obscure the essence of the present invention.

[0062]

[0063] [Example]

[0064] The present invention will be explained in detail below through examples.

[0065] However, the following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the following examples.

[0066]

[0067] <Example 1>

[0068] A composition was prepared by mixing 55 wt% DCHP (Tokyo Chemicals Industry Co., Ltd.) and 45 wt% PVDF (3M Corp., #6012) and mixing them by stirring at 140 ℃. Subsequently, the mixture was uniformly melt-mixed at 210 ℃ for 12 hours using a high-temperature stirrer (indirect heat source method). The mixture was extruded in the form of hollow fibers at a speed of 4.7 g / min from a nozzle having a circular orifice with an outer diameter of 1.2 mm and an inner diameter of 0.8 mm, while DBP (Daejung Chemical Industry Co., Ltd.) was injected into the membrane hollows at a speed of 8.4 g / min at 140 ℃. The extruded hollow fibers were cooled in a temperature-controlled coagulation bath at 30 ℃, while maintaining a winding speed of 60 m / min (draft ratio 7). The cooled hollow fibers were immersed in ethanol (Samjun Corp.) to remove DCHP and DBP, and the ethanol was replaced with water for the extracted membranes. After extraction was complete, the membranes were heat-treated while immersed in water at 121 ℃ for 6 hours using a high-pressure steam heat treatment device (HK-AC200 manufactured by Korea General Machinery), during which a maximum tensile of 500 cN / mm² was applied. 2 The membrane was fixed using a jig. After the heat treatment was completed, the jig was removed, the residue on the membrane was replaced with ethanol, and then vacuum dried at 60°C.

[0069]

[0070] <Example 2>

[0071] A separation membrane was prepared using the same method as in Example 1, except that the extracted separation membrane was heat-treated at 123 °C in a high-pressure steam heat treatment apparatus. At this time, the maximum tension was 500 cN / mm 2 A jig was used to match it.

[0072]

[0073] <Example 3>

[0074] A separation membrane was prepared using the same method as in Example 1, except that the extracted separation membrane was heat-treated in a high-pressure steam heat treatment apparatus at a heat treatment temperature of 125 ℃. At this time, the maximum tension was 500 cN / mm 2 A jig was used to match it.

[0075]

[0076] <Example 4>

[0077] A separation membrane was prepared using the same method as in Example 1, except that the extracted separation membrane was heat-treated in a high-pressure steam heat treatment apparatus at 127 °C for 4 hours. At this time, the maximum tension was 500 cN / mm 2 A jig was used to match it.

[0078]

[0079] <Example 5>

[0080] A separation membrane was prepared using the same method as in Example 1, except that the extracted separation membrane was heat-treated in a high-pressure steam heat treatment apparatus at 129 °C for 4 hours. At this time, the maximum tension was 500 cN / mm 2 A jig was used to match it.

[0081]

[0082] <Example 6>

[0083] Set the heat treatment temperature to 125 ℃, and the maximum tensile strength during heat treatment is 650 cN / mm 2 A separator was manufactured in the same manner as in Example 1, except that a jig was used to match it.

[0084]

[0085] <Example 7>

[0086] Set the heat treatment temperature to 125 ℃, and the maximum tensile strength during heat treatment is 800 cN / mm 2 A separator was manufactured in the same manner as in Example 1, except that a jig was used to match it.

[0087]

[0088] <Example 8>

[0089] Set the heat treatment temperature to 125 ℃, and the maximum tensile strength during heat treatment is 950 cN / mm 2 A separator was manufactured in the same manner as in Example 1, except that a jig was used to match it.

[0090]

[0091] <Comparative Example 1>

[0092] It was prepared using the same method as in Example 1, but the extracted membrane was not immersed in water and was heat-treated at 125 °C for 4 hours using a steam-introductory autoclave (Hanshin). At this time, the maximum tension was 500 cN / mm 2 A jig was used to match it.

[0093]

[0094] <Comparative Example 2>

[0095] It was prepared using the same method as in Example 1, but the extracted membrane was heat-treated in a convection oven (Hanbacktech) at 125 °C for 4 hours. This maximum tension is 500 cN / mm 2 A jig was used to match it.

[0096]

[0097] <Test Example>

[0098] The performance evaluation method for the membranes prepared in the examples and comparative examples is as follows. The results of the performance evaluation are shown in Tables 1 and 2 below.

[0099]

[0100] (1) Measurement of tensile strength and elongation

[0101] Measurements were performed using a Universal Testing Machine (UTM) in accordance with the international standard ASTM D3379. The membrane samples were conditioned for at least 24 hours in a constant environment (23 ℃, 50% relative humidity), and a single filament was fixed to the Universal Testing Machine. The single filament was stretched while increasing the tension at a constant speed. The load and displacement until fracture were recorded, and the load (N) at the point of fracture was [calculated using] the cross-sectional area (mm²). 2 The tensile strength was measured using the following mathematical formula 1 by dividing by ), and the elongation was measured using mathematical formula 2 by dividing the length of the specimen at the time of fracture by the original length and expressing it as a percentage.

[0102]

[0103]

[0104]

[0105]

[0106] (2) Maximum tension control and measurement

[0107] To control the maximum tension, heat treatment was performed with the separator fixed using the jig of Fig. 1. The tension acting on the separator during heat treatment was designed to be quantitatively controlled by adjusting the length of the jig. After heat treatment, the actual tension acting on the separator was measured 10 times on a single strand using Tensitron's TX-5000-1 instrument, and the average value was calculated. The measured tension was quantified by dividing it by the cross-sectional area of ​​the hollow fiber membrane and calculated using Equation 3.

[0108]

[0109] F: Acting force (tension, cN)

[0110] A: Cross-sectional area (mm²) 2 )

[0111]

[0112] (3) amount of water

[0113] The permeation amount of pure water at a temperature of 25°C was measured by static pressure dead-end filtration, and the permeation amount was calculated as follows using Equation 4 from the membrane area, filtration pressure (3 bar), and filtration time.

[0114]

[0115]

[0116] (4) Maximum respect

[0117] The bubble point (Pa) obtained by the bubble point method based on ASTM F316-86 was converted into maximum pore size (nm). As the test solution for immersing the membrane, a fluorocarbon liquid with a surface tension of 12 mN / m (Sumitomo 3M perfluorocarbon coolant FX-3250 product name) was used. The bubble point was determined by setting one hollow fiber membrane with an effective length of 8 cm in a bubble point measuring device, gradually increasing the pressure on the hollow side, and setting the pressure at which the gas flow rate permeating the membrane reached 2.4 E-3 liters / min.

[0118]

[0119] (5) Coefficient of Variation (CV)

[0120] The pore size distribution was analyzed based on data obtained from repeated measurements using a Liquid-Liquid Porometer from PMI (Porous Materials Inc.), and was expressed as a coefficient of pore size variation to quantify it.

[0121] The coefficient of variation in pore size is an indicator that evaluates the uniformity of pore size or the variability of the distribution, and is the ratio of the standard deviation of a data set to the mean value (Equation 5). This indicator is not affected by units and is used because it is suitable for comparing or analyzing various pore size distributions as it expresses the relative variability of the data.

[0122]

[0123]

[0124] (6) Measurement of bacteriophage removal rate

[0125] In this invention, the following experiment was conducted to evaluate the Virus Filtration Efficiency (VFE). A solution containing bacteriophages was prepared, and a virus suspension of a certain concentration was prepared using this solution. Subsequently, a test filter was installed in a filtration device, and the system was configured so that the bacteriophage suspension could pass through the filter under a constant pressure (3 bar). To evaluate the effectiveness of the filter, phiX174 bacteriophages with a diameter of approximately 22–27 nm and an icosahedral structure without an outer envelope were used. phiX174 is widely used as a model virus suitable for evaluating filter performance due to its very small size.

[0126] During the process of injecting a virus suspension into a filtration device and passing it through a filter, the filter removes virus particles. After collecting the filtered sample (outlet sample) and the undiluted solution before filtration (inlet sample), the filtration performance of the filter was evaluated by comparing the virus concentrations of the two samples. Virus concentration was quantitatively measured using the plaque formation analysis method to confirm the virus filtration rate of the filter, and the bacteriophage removal rate was measured using the following Equation 6.

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133] The above examples show that the physical properties and pore structure of the separation membrane were improved by controlling various heat treatment temperatures and the shrinkage rate of the jig. Through Tables 1 and 2, it can be seen that the membranes of the examples according to the present invention have a precisely controlled pore size distribution and an excellent virus removal rate compared to comparative examples.

[0134] The microporous membrane according to the present invention simultaneously achieved physical strength and pore structure control, and maximized the performance of the separation membrane for virus removal by precisely controlling the pore size and distribution through the uniform transfer of a heat source during the heat treatment process.

[0135]

[0136] Foregoing, specific parts of the present invention have been described in detail. It will be apparent to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the invention. Accordingly, the actual scope of the invention is defined by the appended claims and their equivalents.

[0137] The microporous membrane obtained through the economical and efficient membrane manufacturing process according to the present invention exhibits superior water permeability and protein adsorption resistance compared to conventional membranes, and demonstrates excellent durability even during long-term use. Therefore, the manufacturing process according to the present invention and the microporous membrane for virus filtration produced thereby can be utilized in various industrial fields such as water treatment, pharmaceuticals, and biomedicine.

[0138]

[0139] The present invention was carried out under the support of the Ministry of Trade, Industry and Energy of the Republic of Korea under project number 1415185455 and project number 20010846, the management agency for the said project is the Korea Institute of Planning and Evaluation for Industrial Technology, the research project name is “Development of Materials and Components Technology”, and the research project name is “Development of Nanofiltration-grade Biofiltration Module for Virus Removal”.

Claims

1. Dibutyl phthalate (DBP) is added to a molten mixture containing polyvinylidene fluoride (PVDF) resin and dicyclohexyl phthalate (DCHP), and an unsolidified hollow fiber is formed by extruding through a nozzle; The above unsolidified hollow fiber is cooled using a liquid refrigerant at 0 to 50 ℃ to obtain a solidified hollow fiber; Extract and remove DCHP and DBP from the above-mentioned solidified hollow fiber; Wash the hollow fiber from which the above DCHP and DBP have been removed; Immerse the above-mentioned washed hollow fibers in water; and The hollow fiber immersed in the water above is fixed with a tension control device to a maximum tension of 500 to 950 cN / mm 2 Performing heat treatment at a high temperature while maintaining the tension of; A method for manufacturing a microporous membrane for virus filtration comprising the steps, A method for manufacturing a microporous membrane for virus filtration, wherein the maximum tension is measured by the following formula: In the above equation, F is the tension (cN) and A is the cross-sectional area of ​​the microporous membrane (mm² 2 )lim.

2. In Paragraph 1, A manufacturing method in which the step of performing heat treatment at the above high temperature is performed at 120 to 130 ℃ for 1 to 6 hours.

3. In Paragraph 1, The above tension adjustment device is a jig, and the manufacturing method.

4. In Paragraph 1, A method for manufacturing the above-mentioned microporous membrane for virus filtration, wherein the maximum pore size is 20 to 30 nm.

5. In Paragraph 1, The above-described microporous membrane for virus filtration has a pore size variation coefficient of 2.5 to 5%, and is manufactured by a method.

6. In Paragraph 1, The above-described microporous membrane for virus filtration is manufactured by a method having a pore size variation coefficient of 2.9 to 4.4%.

7. In Paragraph 1, A manufacturing method comprising adding a step of drying in a vacuum after the step of performing heat treatment at the above high temperature.

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