Test method and manufacturing method for filters

Abstract

The present application provides a filter test method and a manufacturing method, which can evaluate the filtration performance of a filtration membrane with high accuracy in a simple manner regardless of the opening shape of the filtration membrane. A filter test method for a filter having a container, a filtration membrane disposed in the container, an input port communicating with a primary side of the filtration membrane, and an output port communicating with a secondary side of the filtration membrane, the test method comprising a wetting process in which the filtration membrane is brought into a wet state; an air injection process in which, after the wetting process, the output port is closed, and air is injected from the input port to increase the pressure on the primary side of the filtration membrane; and a volume measurement process in which, after the air injection process, the output port is opened, and the volume of air leaked from the output port from the time when the pressure on the primary side reaches a predetermined value is measured after an equilibrium state in which the pressure difference between the primary side and the secondary side of the filtration membrane becomes substantially constant is established.

Description

TECHNICAL FIELD

[0001] The present application relates to a test method and a manufacturing method of a filter. BACKGROUND

[0002] In the past, when a blood purification method such as hemodialysis therapy, plasma exchange therapy is performed, a filtration membrane is used. For this filtration membrane, it is important to accurately measure the maximum pore diameter so as to prevent components such as bacteria, cancer cells from passing through.

[0003] As a conventional maximum pore diameter measurement method, a bubble point (BP) method, a SEM method, a bacterial culture solution filtration method, and the like are proposed, but in the case of using the SEM method, the observable region is extremely narrow, and in the case of using the bacterial culture solution filtration method, the culture is excessively time-consuming, and it is clear that both are not suitable for performance evaluation.

[0004] The BP method is a method of measuring the maximum pore diameter by assuming the pores of the filtration membrane as a perfect circle, and in this BP method, a liquid (water, alcohol, or the like) is filled in the secondary side of the filtration membrane and in the pores, a pressure based on a gas is applied from the primary side of the filtration membrane, and the pressure at the time when the gas on the primary side transfers to the secondary side through the filtration membrane is measured, whereby the maximum pore diameter is calculated. At present, a technique of calculating the maximum pore diameter of a micro-porous membrane for blood treatment, a hollow fiber membrane for ascites filtration using this BP method is proposed (for example, refer to Patent Literature 1 and Patent Literature 2).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Laid-Open No. 9-51946

[0008] Patent Literature 2: Japanese Patent Application Laid-Open No. 2019-180568 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, since the BP method is a method of measuring the maximum pore diameter by assuming the pores of the filtration membrane as a perfect circle, in the case of measuring the maximum pore diameter of a filtration membrane having a non-perfect circular shape such as an elliptical pore, there is a case where a deviation occurs between the measurement result and the actual filtration performance. The inventors of the present application conducted a study, and as a result, it was clarified that the reason for the deviation is that the pores of the stretched aperture membrane are elliptical, and the filtration performance with respect to bacteria and the like in the ascites is affected by the major axis of the elliptical pore, on the other hand, the maximum pore diameter measured using the BP method is based on the minor axis of the elliptical pore.

[0011] The present application is made in view of the above-described circumstances, and aims to be able to evaluate the filtration performance of a filtration membrane with good accuracy in a simple manner regardless of the aperture shape of the filtration membrane.

[0012] Solution to the problem

[0013] To achieve the above object, the test method of the present application is a test method of a filter (e.g., an ascites filter) that has a container, a filter membrane disposed in the container, an input port that communicates with a primary side of the filter membrane, and an output port that communicates with a secondary side of the filter membrane, the test method of the filter comprising: a wetting process in which the filter membrane is brought to a wet state; an air injection process in which, after the wetting process, the output port is closed and air is injected from the input port, thereby raising the pressure of the primary side of the filter membrane; and a volume measurement process in which, after the air injection process, the output port is opened, and after an equilibrium state in which a pressure difference between the primary side and the secondary side of the filter membrane becomes substantially constant is established, the volume of air that leaks from the output port from the time when the pressure of the primary side reaches a prescribed value (e.g., 98.0 kPa) is measured.

[0014] According to this method, after temporarily plugging the openings of the filter membrane with liquid by bringing the filter membrane to a wet state, the output port that communicates with the secondary side of the filter membrane is closed and air is injected from the input port that communicates with the primary side of the filter membrane, thereby raising the pressure of the primary side of the filter membrane, and after the output port is opened and an equilibrium state (a state in which the pressure difference between the gas of the primary side and the gas of the secondary side of the filter membrane becomes substantially constant) is established, the volume of air that leaks from the output port from the time when the pressure of the primary side reaches a prescribed value (e.g., 98.0 kPa) is measured. Thus, regardless of the shape of the openings of the filter membrane (e.g., even in the case where the openings are elliptical holes having a long axis and a short axis), the maximum pore diameter of the openings of the filter membrane can be appropriately calculated based on the measured leakage volume, and thus the filtration performance of the filter membrane can be evaluated with good precision. In addition, in the BP method that has been employed in the past, high pressure needs to be applied to the filter membrane, and there is a possibility that the hollow fibers that constitute the filter membrane will break, in contrast to which, in the present method, such high pressure need not be applied, and thus the test can be easily performed without applying excessive load to the filter membrane. Furthermore, in the BP method, a test needs to be performed using a mini module (a module that has been reduced in size), in contrast to which, the present method can perform a test using a full module (a module that has the actual size used), and thus has the advantage that the maximum pore diameter under actual product specifications can be ensured.

[0015] In the test method of the filter membrane of the present application, the wetting process can include: a liquid injection process in which liquid is injected from the input port to the primary side of the filter membrane, thereby filling the primary side and the secondary side of the filter membrane disposed in the container with liquid; and a liquid discharge process in which, after the liquid injection process, the output port is opened, thereby discharging a portion (e.g., about 2 / 3) of the filled liquid.

[0016] According to this method, the filtration membrane can be sufficiently brought into a wet state by filling the primary side and the secondary side of the filtration membrane with a liquid. In addition, if all of the filled liquid is removed, the filtration membrane dries and it becomes difficult to continue the test, but in this method, by leaving part of the filled liquid in the container, drying of the filtration membrane can be inhibited.

[0017] In the test method for a filtration membrane of the present application, a pressurization release process of opening the output port for a prescribed time to release the pressurization can be included between the air injection process and the volume measurement process.

[0018] According to this method, the output port is opened for a prescribed time to release the pressurization before the transition to the volume measurement process after the air injection process. Thus, even in the case where the pressure of the primary side of the filtration membrane excessively rises due to the injection of air from the input port, the pressure can be rapidly reduced to approach the equilibrium state, and measurement of the leakage volume can be rapidly performed.

[0019] In addition, the production method of the present application is a production method of a filter provided with a container, a filtration membrane disposed in the container, an input port communicating with the primary side of the filtration membrane, and an output port communicating with the secondary side of the filtration membrane, the production method of the filter including a test method for evaluating the filtration performance of the filtration membrane, the test method including: a wetting process in which the filtration membrane is brought into a wet state; an air injection process in which the output port is closed after the wetting process, and air is injected from the input port, thereby raising the pressure of the primary side of the filtration membrane; and a volume measurement process in which the output port is opened after the air injection process, and the volume of air leaked from the output port from the time when the pressure of the primary side reaches a prescribed value is measured after an equilibrium state in which the pressure difference between the primary side and the secondary side of the filtration membrane becomes substantially constant is established.

[0020] According to this method, since a test method is adopted in which the maximum pore diameter of the pores of the filtration membrane can be appropriately calculated based on the measured leakage volume regardless of the shape of the pores of the filtration membrane, whether the produced filtration membrane has the desired filtration performance can be evaluated with good precision. In the case where the produced filtration membrane does not have the desired filtration performance, appropriate processing (for example, reevaluation of the production process) can be performed to obtain the desired filtration performance.

[0021] Effects of the Invention

[0022] According to the present application, the filtration performance of a filtration membrane can be evaluated with good precision in a simple manner regardless of the shape of the pores of the filtration membrane. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1This is a flowchart illustrating the steps of a test method for a filter according to an embodiment of the present invention.

[0024] Figure 2 This is an explanatory diagram illustrating the humidification process of the test method for the filter according to an embodiment of the present invention.

[0025] Figure 3 This is an explanatory diagram illustrating the air injection process of the test method for the filter according to an embodiment of the present invention.

[0026] Figure 4 This is an explanatory diagram illustrating the pressurization and release process of the test method for the filter according to an embodiment of the present invention.

[0027] Figure 5 This is an explanatory diagram illustrating the volume measurement process of the test method for the filter according to an embodiment of the present invention.

[0028] Explanation of reference numerals in the attached figures

[0029] 1. Filter; 10. Container; 11. Air inlet (inlet); 13. Filtrate outlet (bottom outlet, outlet); 14. Filtrate outlet (top outlet, outlet); 20. Filter membrane; S1. Humidification process; S11. Liquid injection process; S12. Liquid drainage process; S2. Air injection process; S3. Pressurization and release process; S4. Volume measurement process. Detailed Implementation

[0030] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0031] First, the structure of filter 1, evaluated using the test method according to an embodiment of the present invention, will be described. For example... Figure 2 As shown, the filter 1 in this embodiment is an ascites filter comprising a container 10, a filter membrane 20 disposed in the container 10, an inlet (air injection port 11) communicating with the primary side of the filter membrane 20, and an outlet (filtrate discharge port 13, 14) communicating with the secondary side of the filter membrane 20.

[0032] The container 10 is a cylindrical shell made of glass or the like. Inside the container 10 is a generally cylindrical filter membrane (stretched perforated membrane) 20 with extended openings. At one axial end of the container 10 (the end facing downwards in the vertical direction), an air injection port 11 is provided for injecting air into the container 10 during the air injection step S2 described later. The air injection port 11 communicates with the primary side (inner side) of the filter membrane 20 and functions as an input port in this invention. On the other hand, at the other axial end of the container 10 (the end facing upwards in the vertical direction), an air outlet 12 is provided for partially expelling air from the container 10 during the air injection step S2 in this embodiment. The air outlet 12 also communicates with the primary side (inner side) of the filter membrane 20.

[0033] The container 10 has filtrate outlets 13 and 14 on its side wall for discharging the filtrate that has passed through the filter membrane 20. These filtrate outlets 13 and 14 communicate with the secondary side (outer side) of the filter membrane 20 and function as output ports in this invention. In this embodiment, during the draining step S12 of the humidification step S2, a portion of the liquid filled into the container 10 is discharged from the filtrate outlet 13 (hereinafter referred to as the "lower outlet"), which is positioned vertically downwards. Furthermore, in this embodiment, during the pressurization release step S3, the pressurized air is released via the filtrate outlet 14 (hereinafter referred to as the "upper outlet"), which is positioned vertically upwards, and during the volume measurement step S4, the volume of air leaking from the upper outlet 14 is measured.

[0034] Next, use Figures 1-5 The test method for embodiments of the present invention will be described. In this test method, in order to evaluate the filtration performance of the filter 1, the maximum pore size of the filter membrane (stretched open-pore membrane) 20 provided on the filter 1 is calculated.

[0035] First, the filter membrane 20 of filter 1 is made wet (wetting process S1). The wetting process S1 in this embodiment includes, for example... Figure 2 The liquid injection process S11, which involves filling liquid into the primary and secondary sides of the filter membrane 20 disposed within the container 10 as shown in (A), and the process as shown in (A) Figure 2 The draining process S12, as shown in (B) and (C), removes a portion of the filled liquid.

[0036] The filling of liquid in the liquid injection process S11 can be carried out by injecting liquid into the primary side of the filter membrane 20 from the air injection port (inlet port) 11 and allowing it to permeate into the secondary side of the filter membrane 20 (i.e., allowing the liquid to move from the primary side of the filter membrane 20 to the secondary side), or by injecting liquid into the secondary side of the filter membrane 20 from the lower outlet port 13 and allowing the liquid to move from the primary side of the filter membrane 20 to the upper outlet port 14 (i.e., allowing the liquid to move from the secondary side of the filter membrane 20 to the secondary side again via the primary side).

[0037] In the draining process S12, such as Figure 2 As shown in (B), approximately 2 / 3 of the filled liquid is discharged from the lower outlet 13 (at this time, the upper outlet 14 is also pre-opened). If all the liquid is discharged, the filter membrane 20 may dry out, making it difficult to continue the test (if the filter membrane 20 is not wet, air blockage cannot be formed, making accurate evaluation impossible). On the other hand, if too much liquid remains in the container 10, when the pressure on the primary side of the filter membrane 20 is increased in the air injection step S2 described later, the liquid will be discharged from the upper outlet 14, making accurate evaluation impossible. In the liquid discharge step S12, when approximately 2 / 3 of the filled liquid has been discharged, as... Figure 2 As shown in (C), close the two filtrate outlets (output ports) 13 and 14.

[0038] After the humidification process S1, air is injected through the air injection port (inlet) 11, thereby increasing the pressure on the primary side of the filter membrane 20 (air injection process S2). In the air injection process S2 of this embodiment, firstly, as... Figure 3 As shown in (A), with the air outlet 12 and the filtrate outlet (output port) 13, 14 closed, air at a pressure of approximately 98.0 kPa to 100 kPa is injected through the air inlet 11. This compresses the air layer inside the container 10, reducing its volume to approximately half, causing the liquid level in the container 10 to rise to approximately two-thirds of the container's height. Then, as... Figure 3 As shown in (B), the air outlet 12 is temporarily opened. This releases the compressed state of the air layer, causing the liquid level to drop to approximately half the height of container 10. Then, as... Figure 3 As shown in (C), if the air outlet 12 is closed, the air layer inside the container 10 is compressed again, so the liquid level rises again to about 2 / 3 of the height of the container 10.

[0039] After the air injection process S2, with the air injection port (inlet port) 11 closed, as follows: Figure 4(A) and (B) of FIG. 6, the upper discharge port 14 is opened for a prescribed time (for example, about 0.5 seconds) to release the pressurization (pressurization release step: S3). The pressurization release step S3 in the present embodiment is a step performed to optimize the shape of the filter membrane 20 in the volume measurement step S4 described later by removing the pressure that is excessively applied to the filter membrane 20. After the release of the pressurization is achieved by the pressurization release step S3, as shown in (A) and (B) of FIG. 7, the upper discharge port 14 is closed again. Figure 4

[0040] After the pressurization release step S3, as shown in (A) and (B) of FIG. 8, the upper discharge port (output port) 14 is opened, and after a state in which the pressure difference between the primary side and the secondary side of the filter membrane 20 becomes substantially constant (for example, a state in which the pressure of the primary side becomes 98.4 kPa) is established, the volume of air leaked from the upper discharge port 14 from the time at which the pressure of the primary side reaches a prescribed value (for example, 98.0 kPa) is measured (volume measurement step: S4). In the volume measurement step S4 of the present embodiment, the volume of air leaked from the upper discharge port 14 from the time at which the pressure of the primary side reaches the prescribed value to the elapse of a prescribed time (for example, 10 seconds) is measured. The prescribed value and the prescribed time can be appropriately set according to the specifications and dimensions of the filter 1 that is the evaluation object. Figure 5

[0041] Thereafter, the maximum pore diameter of the filter membrane 20 is calculated on the basis of the volume of air measured in the volume measurement step S4, and the filtration performance of the filter 1 is evaluated on the basis of the calculated maximum pore diameter (evaluation step: S5). Furthermore, the evaluation method of the filtration performance in the evaluation step S5 is not limited thereto, and for example, if the volume of air measured in the volume measurement step S4 is equal to or less than a prescribed amount (for example, 0.5 mL), it can also be evaluated as satisfying the desired filtration performance.

[0042] ​​In the test method of the above-described embodiment, after temporarily clogging the openings of the filtration membrane 20 with liquid by bringing the filtration membrane 20 into a wet state, the output port (filtrate discharge port 13, 14) communicating with the secondary side of the filtration membrane 20 is closed and air is injected from the input port (air injection port 11) communicating with the primary side of the filtration membrane 20, thereby raising the pressure of the primary side of the filtration membrane 20, and then, after opening the output port (upper discharge port 14) and establishing an equilibrium state (a state in which the pressure difference between the gas of the primary side and the gas of the secondary side of the filtration membrane 20 becomes substantially constant), the volume of air leaked from the output port (upper discharge port 14) from the time when the pressure of the primary side reaches a predetermined value (for example, 98.0 kPa) is measured. Thus, regardless of the shape of the openings of the filtration membrane 20 (for example, even in the case where the openings are elliptical holes having a long axis and a short axis), the maximum pore diameter of the openings of the filtration membrane 20 can be appropriately calculated on the basis of the measured leakage volume, and thus the filtration performance of the filtration membrane 20 can be evaluated with good precision. In addition, in the BP method conventionally employed, high pressure needs to be applied to the filtration membrane 20, and the hollow fibers constituting the filtration membrane 20 can be broken, in contrast to which, in the present method, such high pressure need not be applied, and thus the test can be easily performed without applying excessive load to the filtration membrane 20. Furthermore, in the BP method, a test needs to be performed using a mini module (a module reduced in size), in contrast to which, the present method can perform a test using a full module (a module of the actual size used) and thus has the advantage that the maximum pore diameter under actual product specifications can be ensured.

[0043] In addition, in the test method of the above-described embodiment, the wetting process S1 includes a liquid injection process S11 and a liquid discharge process S12, in the liquid injection process S11, liquid is injected from the input port (air injection port 11) to the primary side of the filtration membrane 20, thereby filling the primary side and the secondary side of the filtration membrane 20 disposed inside the container 10 with liquid, and in the liquid discharge process S12, a portion (for example, about 2 / 3) of the filled liquid is discharged by opening the output port (filtrate discharge port 13, 14) after the liquid injection process S11. Thus, by filling the primary side and the secondary side of the filtration membrane 20 with liquid, the filtration membrane 20 can be sufficiently brought into a wet state. In addition, if all of the filled liquid is discharged, the filtration membrane 20 dries and it becomes difficult to continue the test, but in the present method, by allowing the filled liquid to remain partially in the container, drying of the filtration membrane 20 can be suppressed.

[0044] Further, in the test method of the above-described embodiment, the pressurization release process S3 is implemented before the transition to the volume measurement process S4 after the air injection process S2, whereby the output port (the upper discharge port 14) is opened for a prescribed time to release the pressurization. Thus, even in the case where the pressure on the primary side of the filter membrane 20 excessively rises due to the injection of air from the input port (the air injection port 11), the pressure can be rapidly reduced to approach the equilibrium state, and the measurement of the leakage volume can be rapidly implemented.

[0045] Further, in the above-described embodiment, the test method for evaluating the filtration performance of the filter membrane 20 of the filter 1 is described, but the test method can be introduced when the filter 1 having the filter membrane 20 is manufactured. That is, a manufacturing method of a filter 1 that includes a container 10, a filter membrane 20 disposed in the container 10, an input port (air injection port 11) that communicates with a primary side of the filter membrane 20, and an output port (filtrate discharge port 13, 14) that communicates with a secondary side of the filter membrane 20, the manufacturing method of the filter 1 can include a test method for evaluating the filtration performance of the filter membrane 20, the test method can include: a wetting process S1 in which the filter membrane 20 is brought to a wet state; an air injection process S2 in which the output port (filtrate discharge port 13, 14) is closed after the wetting process S1, and air is injected from the input port (air injection port 11) to thereby raise the pressure on the primary side of the filter membrane 20; and a volume measurement process S4 in which the output port (upper discharge port 14) is opened after the air injection process S2, and the volume of air that leaks from the output port (upper discharge port 14) from the time when the pressure on the primary side reaches a prescribed value (for example, 98.0 kPa) is measured after an equilibrium state in which the pressure difference between the primary side and the secondary side of the filter membrane 20 becomes substantially constant is established.

[0046] When such a manufacturing method is employed, since the test method in which the maximum pore diameter of the pores of the filter membrane 20 can be appropriately calculated based on the measured leakage volume regardless of the shape of the pores of the filter membrane 20 is employed, whether the manufactured filter membrane 20 has the desired filtration performance can be evaluated with good precision. In the case where the manufactured filter membrane 20 does not have the desired filtration performance, appropriate processing (for example, reevaluation of the manufacturing process) can be performed to obtain the desired filtration performance.

[0047] The present application is not limited to the above-described embodiments, and modes obtained by appropriately applying design changes to the embodiments by those skilled in the art within the scope of the present application are also included in the scope of the present application, as long as the modes have the characteristics of the present application. That is, each element included in the above-described embodiments and the arrangement, material, condition, shape, size, and the like thereof are not limited to the illustrated content, but can be appropriately changed. In addition, each element included in the above-described embodiments can be combined within a technically feasible range, and a mode obtained by combining them is also included in the scope of the present application, as long as the mode has the characteristics of the present application.

Claims

1. A test method of a filter having a container, a filtration membrane disposed in the container, an input port communicating with a primary side of the filtration membrane, and an output port communicating with a secondary side of the filtration membrane, wherein the test method of the filter comprises: a wetting process in which the filtration membrane is brought to a wet state; an air injection process in which, after the wetting process, the output port is closed, air is injected from the input port, and thereby the pressure of the primary side of the filtration membrane is raised; a pressurization release process in which, after the air injection process, the input port is closed, the output port is opened for a prescribed time to cause pressurization release, and after an equilibrium state in which a pressure difference between the primary side and the secondary side of the filtration membrane becomes substantially constant is established, the output port is closed again; and a volume measurement process in which, after the pressurization release process, the output port is opened, and the volume of air leaked from the output port from the time when the pressure of the primary side reaches a prescribed value is measured.

2. The test method of the filter according to claim 1, wherein the prescribed value is 98.0 kPa.

3. The test method of the filter according to claim 1 or 2, wherein the wetting process comprises: a liquid injection process in which the primary side and the secondary side of the filtration membrane disposed in the container are filled with a liquid by injecting the liquid from the input port to the primary side of the filtration membrane or from the output port to the secondary side of the filtration membrane; and a liquid discharge process in which, after the liquid injection process, the output port is opened, and thereby a portion of the filled liquid is discharged.

4. The test method of the filter according to claim 3, wherein in the liquid discharge process, about 2 / 3 of the filled liquid is discharged.

5. The test method of the filter according to claim 1 or 2, wherein the filter is an ascites filter.

6. A manufacturing method of a filter having a container, a filtration membrane disposed in the container, an input port communicating with a primary side of the filtration membrane, and an output port communicating with a secondary side of the filtration membrane, wherein the manufacturing method of the filter comprises a test method for evaluating the filtration performance of the filtration membrane, the test method comprises: a wetting process in which the filtration membrane is brought to a wet state; an air injection process in which, after the wetting process, the output port is closed, air is injected from the input port, and thereby the pressure of the primary side of the filtration membrane is raised; a pressurization release process in which, after the air injection process, the input port is closed, the output port is opened for a prescribed time to cause pressurization release, and after an equilibrium state in which a pressure difference between the primary side and the secondary side of the filtration membrane becomes substantially constant is established, the output port is closed again; and ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the volume measurement process, after the pressurization and release process, the output port is opened, and the volume of air leaking from the output port from the moment the pressure on the primary side reaches a predetermined value is measured. The specified value is less than the pressure on the primary side in the equilibrium state.

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