JP5835659B2 - Porous hollow fiber membrane for protein-containing liquid treatment - Google Patents

Description

  The present invention relates to a porous hollow fiber membrane for protein-containing liquid treatment that can efficiently separate a useful recovery substance contained in an aqueous fluid such as a protein solution and fine particles such as viruses.

  Hollow fiber membranes intended for the treatment of aqueous fluids are widely used in industrial applications such as microfiltration and ultrafiltration, and medical applications such as hemodialysis, hemofiltration and hemodiafiltration. In particular, in recent years, in the manufacturing process of biopharmaceuticals and blood products, there is a demand for a technique for removing pathogenic substances such as viruses from protein solutions, which are useful components, and improving safety.

According to Non-Patent Document 1, regarding the virus removal / inactivation process of the plasma fraction preparation, it is desirable to work on two or more different virus inactivation and removal processes. According to the description of Non-Patent Document 2, the LRV to be achieved as the target value is about 4. Further, in Non-Patent Document 3, “Especially regarding the virus removal / inactivation process in Japan,“ Guidelines for ensuring the safety of plasma fraction preparations against viruses ”, Medicinal Product No. 1047 (August 30, 1999) , It is stated that “it is desirable to consider two or more different virus inactivation and removal processes”, and for a specific virus, the total virus clearance index of the manufacturing process (total virus clearance). An index of 9 or more is required. Is described. The LRV means the virus clearance index R shown in Non-Patent Document 1 as follows.
Virus clearance index R = log ((V1 × T1) / (V2 × T2))
V1 Capacity before process treatment T1 Virus titer before process treatment V2 Capacity after process treatment T2 Virus titer after process treatment

  Virus removal and inactivation methods include heat treatment, optical treatment such as gamma rays and ultraviolet irradiation, chemical treatment such as low pH treatment, precipitation fractionation such as ethanol fractionation and ammonium sulfate fractionation, and removal by membrane filtration. However, membrane removal methods that do not lead to protein denaturation have attracted attention in removing viruses from protein solutions.

  On the other hand, in the manufacturing process of biopharmaceuticals and blood products, proteins that are useful components must be efficiently permeated and recovered from the viewpoint of productivity. However, especially when the target of separation and removal is a small-sized virus such as parvovirus, it has been difficult to satisfy the virus removal characteristics and the permeation characteristics of useful proteins at the same time.

In Patent Document 1, an average permeation for 5 minutes from the start of filtration when 3 wt% bovine immunoglobulin having a specific maximum pore size and the proportion of the monomer is 80 wt% or more is filtered at a constant pressure of 0.3 MPa. A hydrophilic microporous membrane is disclosed in which the relationship between the rate (globulin permeation rate A), the average permeation rate (globulin permeation rate B) for 5 minutes from the lapse of 55 minutes after the start of filtration, and the maximum pore diameter is parameterized. . The constituent requirements of this film are as follows.
(1) Maximum pore diameter of 10 to 100 nm
(2) Globulin permeation rate A> 0.0015 × maximum pore size (nm) ^2.75
(3) Globulin permeation rate B / globulin permeation rate A> 0.2

  These requirements (1) to (3) merely describe the target characteristics of the membrane for the purpose of removing viruses from protein solutions, in which viruses are efficiently removed and the permeation amount of protein solutions is high. However, it does not give useful and specific information on the problem of obtaining a membrane with high protein permeability and high virus removal.

  Considering in detail about (3), the permeation rate of the protein solution does not necessarily decrease with time if the ratio between the permeation rate after 55 minutes from the start of filtration and the permeation rate immediately after the start of filtration is high. do not do. For example, it is conceivable that the permeation rate of the protein solution gradually decreases as the filtration time elapses, and a defect occurs in the membrane at a certain point, and the permeation rate is reversed. In this case, as a result, the permeation speed 55 minutes after the start of filtration increases, and the ratio of both may exceed 0.2. However, it cannot be said that a membrane exhibiting such a behavior has achieved the problem of obtaining a membrane with high protein permeability and high virus removal.

  Patent Document 1 also discloses a microporous membrane having a sparse structure layer with a high porosity and a dense layer with a low porosity, but here it is easy to make a homogeneous structure by heat-induced phase separation in the first place. A hollow fiber membrane made of polyvinylidene fluoride (hereinafter abbreviated as PVDF) has been discussed. For example, a material such as a polysulfone resin widely used as a material for hemodialysis membranes due to its high water permeability. It is difficult to apply the technology as it is.

  Patent Document 2 discloses a microporous film having a sparse structure layer with a high porosity and a dense layer with a low porosity, but PVDF is also assumed as a material here. While PVDF is excellent in physical strength, it is a hydrophobic material, so that protein adsorption, membrane contamination and clogging are likely to occur, and the filtration rate is drastically reduced. In order to improve this unfavorable characteristic, it is necessary to impart hydrophilicity to the membrane. Generally, PVDF material membranes must be modified to hydrophilicity by post-treatment after film formation. As compared with a general polysulfone resin, forming a film in a blended state with a conductive polymer has a disadvantage in that it is a complicated manufacturing process.

  Patent Document 3 discloses a virus-retaining ultrafiltration membrane having an initial LRV of at least 4.0 relative to PhiX174 and having a surface hydrophilized with hydroxyalkylcellulose. In the technique disclosed here, the hydrophilicity is made by a special hydrophilic polymer, and lacks versatility. A blend of polysulfone or the like and a hydrophilic polymer such as polyvinyl pyrrolidone is also exemplified, but hydrophilic treatment with hydroxyalkyl cellulose is essential. Further, although a hollow fiber type is allowed as the membrane, a flat membrane type is assumed, and a sufficient explanation for obtaining the hollow fiber membrane type is not made.

  Patent Document 4 discloses a method for producing an immunoglobulin preparation that effectively removes viruses in industrial production processes and does not cause filtration problems such as clogging of the removal membrane due to aggregates and contaminating proteins. ing. Here, there is a description that a step of filtering an immunoglobulin solution using a porous membrane having an average pore diameter of 15 to 20 nm is included, and the material of the porous membrane is preferably regenerated cellulose. Further, FIGS. 1, 2 and 3 show graphs in which the accumulated filtrate amount extends almost linearly with respect to the elapsed time. Certainly, when filtered using the regenerated cellulose virus-removing membrane Planova 20N (Asahi Kasei Pharma Co., Ltd.) described in Example 1, it may be considered that such behavior is exhibited. The effect of being a regenerated cellulose material having very high hydrophilicity is great. In fact, it has been very difficult to obtain a membrane having such a linear filtration behavior with a synthetic membrane composed of a hydrophobic polymer and a hydrophilic polymer. Since the cellulose membrane has low strength when wet in water, it is difficult to set the filtration pressure high, and it has a drawback that a high permeation rate cannot be obtained.

  In Patent Document 5, a polymer porous hollow fiber having a pore structure in which the in-plane porosity initially decreases as it proceeds from the inner wall surface to the inside of the wall and passes through at least one minimum portion, and then increases again at the outer wall portion. A membrane and a virus removal method using this membrane to filter an aqueous protein solution are disclosed. If the membrane structure disclosed here is simply expressed, it can be said that the pore diameter of the membrane wall is a hollow fiber membrane that is sparse-dense-sparse in the film thickness direction. Having such a tilted structure and having a specific average pore size is said to be suitable for removing proteins with high efficiency and for recovering proteins with high permeability without denaturing the proteins. Although various polymer materials are exemplified as the material, it is a technology using regenerated cellulose, and it is difficult to apply the technology disclosed here to many materials for general use. Further, the disadvantages of the cellulose material are as already described.

In Patent Document 6, the surface on the downstream side of the filtration has a dot-like or slit-like opening, the surface on the upstream side of the filtration has a network structure or a fine particle aggregate structure, and the central region of the film thickness portion is substantially homogeneous And a porous membrane having a structure in which the film thickness portion has substantially no macrovoid is disclosed. This membrane structure is said to be suitable for efficient virus removal and efficient protein permeation / recovery, but the clearance index of bacteriophage φX174 in the examples is 0.1% in the BSA-added system solution. The result was a sweeter condition than the actual virus removal process of> 5.1 at a filtration load of 50 L / m ² , and it was by no means an efficient virus removal.

WO2004 / 035180 WO2003 / 026779 JP 2007-136449 A JP 2008-094722 A Japanese Patent Publication No. 04-050054 WO2010 / 074136

Medicinal Product No. 1047 (August 30, 1999) (Notified by the Director of the Pharmaceutical Safety Bureau of the Ministry of Health and Welfare) PDA Journal of GMP and Validation in Japan, Vol. 7, no. 1, p. 44 (2005) PDA Journal of GMP and Validation in Japan, Vol. 9, no. 1, p. 6 (2007)

  The present invention has been made in view of the above-described conventional state of the art, and its purpose is to separate and remove a removal substance such as a virus with a high phage clearance index while efficiently transmitting a useful collection substance such as a protein. An object of the present invention is to provide a porous hollow fiber membrane that can be used.

  As a result of intensive studies to achieve the above object, the present inventors have found a structure of a specific film thickness part capable of capturing fine particles such as viruses of a specific size and permeating smaller useful substances, and the present invention. It was completed.

That is, the present invention has the following configurations (1) to (10).
(1) When a colloidal gold particle comprising a hydrophobic polymer and a hydrophilic polymer and having a particle diameter of 20 nm is subjected to constant pressure filtration, it has a trapping layer in the vicinity of the inner periphery and the outer periphery of the film thickness portion. Has a dense-sparse-dense structure from the inner periphery to the outer periphery, and when colloidal gold colloidal particles having a particle diameter of 10 nm are filtered under constant pressure, the colloidal gold is not trapped in the film thickness portion. Porous hollow fiber membrane for processing.
(2) The porous hollow fiber membrane for protein-containing liquid treatment as described in (1), wherein the thickness of the capturing layer existing in the vicinity of the inner periphery and in the vicinity of the outer periphery is 1 to 15 μm.
(3) The porous for protein-containing liquid treatment according to (1), wherein the vicinity of the inner periphery and the vicinity of the outer periphery refer to ranges from the inner surface and the outer surface of the hollow fiber membrane to 30% of the film thickness, respectively. Hollow fiber membrane.
(4) The vicinity of the inner periphery and the vicinity of the outer periphery refer to a range of 1 to 30% of the film thickness from the inner surface and the outer surface of the hollow fiber membrane, respectively. Porous hollow fiber membrane.
(5) The porous hollow for protein-containing liquid treatment according to any one of (1) to (4), wherein the pore diameter of the capturing layer existing in the vicinity of the inner periphery and in the vicinity of the outer periphery is 10 to 40 nm. Yarn membrane.
(6) The porous hollow fiber membrane for protein-containing liquid treatment according to any one of (1) to (5), wherein the inner diameter is 150 to 400 μm and the film thickness is 50 to 100 μm.
(7) The porous hollow fiber membrane for protein-containing liquid treatment according to any one of (1) to (6), wherein the hydrophobic polymer is a polysulfone polymer.
(8) The porous hollow fiber membrane for protein-containing liquid treatment according to any one of (1) to (7), wherein the hydrophilic polymer is polyvinylpyrrolidone.
(9) The porous hollow fiber membrane for protein-containing liquid treatment according to any one of (1) to (8), which is a membrane used for separating a virus from a protein solution.
(10) The porous hollow fiber for protein-containing liquid treatment according to any one of (1) to (9), wherein the permeation rate of pure water is 10 to 400 L / (h · m ² · bar) film.

  The porous hollow fiber membrane of the present invention allows a useful recovery substance such as a protein to permeate efficiently, and at the same time, removes a removal substance such as a virus with a high phage clearance index. In the production process, it can be suitably used as a membrane for removing pathogenic substances such as viruses from a solution of proteins that are useful components.

FIG. 1 shows an example of an optical microscope image of a cross section of a hollow fiber membrane when colloidal gold particles having a particle diameter of 20 nm are filtered at a constant pressure. In the image of FIG. 1, there are trapping layers dyed with colloidal gold near the inner periphery and the outer periphery of the hollow fiber membrane with respect to the filtration direction of the membrane cross section. FIG. 2 shows an example of an optical microscope image in which a trapping layer dyed with colloidal gold exists only in the vicinity of the outer periphery of the hollow fiber membrane when filtered at a constant pressure as in FIG. FIG. 3 shows an example of a transmission electron microscope image of the film thickness portion of the hollow fiber membrane. In the image of FIG. 3, the film thickness portion has a dense-sparse-dense structure from the vicinity of the inner periphery to the vicinity of the outer periphery, and the film thickness portion has a structure having substantially no macrovoids. FIG. 4 shows an example of an enlarged image of the vicinity of the inner periphery of the film thickness portion of FIG. FIG. 5 shows an example of an enlarged image of the central portion of the film thickness portion of FIG. FIG. 6 shows an example of an enlarged image of the vicinity of the outer periphery of the film thickness portion of FIG. FIG. 7 shows an example of a transmission electron microscope image of a hollow fiber membrane in which a trapping layer dyed with a colloid of 20 nm exists only in the vicinity of the outer periphery of the hollow fiber membrane when filtered at a constant pressure as in FIG. In the image of FIG. 7, the film thickness portion has a sparse-sparse-dense structure from the vicinity of the inner periphery to the vicinity of the outer periphery. FIG. 8 shows an example of an enlarged image of the vicinity of the inner periphery of the film thickness portion of FIG. FIG. 9 shows an example of an enlarged image of the central portion of the film thickness portion of FIG. FIG. 10 shows an example of an enlarged image of the vicinity of the outer periphery of the film thickness portion of FIG. The membrane structure is dense. FIG. 11 shows that when a colloidal gold particle having a particle diameter of 20 nm is filtered at a constant pressure, the same membrane as the membrane having a trapping layer dyed with colloidal gold in the vicinity of the inner periphery and the outer periphery of the hollow fiber membrane is used. The example of the optical microscope image in which the capture layer dye | stained with the gold colloid does not exist in a hollow fiber membrane when the gold colloid particle of 10 nm is filtered by constant pressure is shown. FIG. 12 is an explanatory diagram of the vicinity of the inner periphery and the vicinity of the outer periphery of the porous hollow fiber membrane of the present invention.

  Design of a membrane structure is important in order to separate and remove a removal substance such as a virus with a high phage clearance index while a useful collection substance such as a protein efficiently permeates. In particular, when the target of separation and removal is a small-sized virus such as a parvovirus, it is necessary to efficiently separate these because they are at the same molecular size level as useful proteins.

  First, as a basic requirement, a pressure strength that can withstand the lowest filtration pressure level 1 Bar in the manufacturing process of biopharmaceuticals and blood products is required. For this purpose, the film structure needs to have a uniform and certain thickness without having a large void or defect.

  Next, in order to achieve high phage clearance as a virus removal membrane, it is necessary to block the transmission of viruses with a diameter of 20 to 30 nm, and at the same time to pass through useful proteins (such as immunoglobulins) with a diameter of about 10 nm that do not change much in size. There is. For this purpose, a dense layer with extremely high fractionation is required as the film structure. In addition, it is preferable that a plurality of dense layers exist in the film thickness portion in order to improve the phage clearance of the entire film.

  Furthermore, it is necessary to efficiently permeate useful proteins. For this purpose, it is preferable that the film has a structure that is somewhat sparse except for a dense part that prevents viruses, but does not have a large void-like defect.

  From the above knowledge, the present inventor has a virus trapping layer in the vicinity of the inner periphery and the outer periphery of the film thickness portion as the virus removal film, and the film thickness portion is dense-sparse-dense from the inner periphery to the outer periphery. I found that it was necessary to take a simple structure.

Specifically, the film structure of the present invention will be described with reference to the drawings.
The porous hollow fiber membrane of the present invention has two trapping layers in the vicinity of the inner periphery and the outer periphery of the hollow fiber membrane with respect to the filtration direction of the membrane cross section when colloidal gold particles having a particle diameter of 20 nm are filtered at constant pressure. In addition, when colloidal gold particles having a particle diameter of 10 nm are filtered under constant pressure, the colloidal gold is not trapped in the film thickness portion. “Two capture layers” means that there are layers for capturing colloidal gold in the vicinity of the inner periphery and the vicinity of the outer periphery. Specifically, the structure as shown in FIG. 1 is a “structure having two acquisition layers”.

  Here, the vicinity of the inner periphery and the vicinity of the outer periphery refer to a range of 30% of the film thickness from the inner surface and the outer surface of the hollow fiber membrane, respectively, particularly a range of 1 to 30%, as shown in FIG. For example, when the film thickness is 100 μm, the vicinity of the inner periphery ranges from the inner surface to a depth of 30 μm. It is important to have one each in the vicinity of the inner periphery and the periphery of the outer periphery of the structure where the trapping layer is sparse, in order to achieve both virus prevention and penetration of useful proteins. For example, if two capture layers exist in the vicinity of the inner periphery, the vicinity of the outer periphery, or other regions, if the capture layers are too close to each other, a membrane structure in which a dense capture layer is continuous is formed, and the permeation of useful proteins It ’s a big resistance for me. Moreover, it is preferable that the thickness of the acquisition layer of inner periphery vicinity and outer periphery vicinity is 1-15 micrometers. If the thickness is less than 1 μm, the virus capturing function cannot be sufficiently obtained, and if it exceeds 15 μm, the permeability of the membrane may be deteriorated.

  In the present invention, the reason why the colloidal gold is used for the capture test is that the properties of the colloidal gold and the small-diameter virus are very similar. Both are rigid spheroids, and gold colloidal particles with a particle size of 20 nm are very close to the size of a small virus of 20 to 30 nm. Therefore, the fact that the porous hollow fiber membrane of the present invention has two capture layers of colloidal gold particles having a particle diameter of 20 nm means that there are two capture layers of small-diameter viruses. For example, when the removal rate of small-diameter virus in one capture layer is 99.9%, if there are two capture layers, the removal rate can be increased to 99.9999%. Can be improved. Moreover, the fact that gold colloidal particles having a particle diameter of 10 nm are not captured by the porous hollow fiber membrane of the present invention means that useful proteins having a diameter of about 10 nm are permeated. In the present invention, these conditions enable efficient separation of small-diameter viruses and useful proteins.

  On the other hand, FIG. 2 shows an example in which when a colloidal gold particle having a particle diameter of 20 nm is subjected to constant pressure filtration, a capturing layer dyed with colloidal gold exists only in the vicinity of the outer periphery. This is an unfavorable structure in the present invention.

  Further, as shown in FIG. 3, the porous hollow fiber membrane of the present invention has a dense-sparse-dense structure in which the film thickness portion extends from the vicinity of the inner periphery to the vicinity of the outer periphery. Specifically, in the transmission electron microscope image, the film thickness portion has a structure in the vicinity of the inner periphery as shown in FIG. 4, the vicinity of the outer periphery as shown in FIG. 6, and the central portion between them as shown in FIG. 5. The black part or the gray part in the figure indicates a polymer part, and the white part indicates a void due to a membrane hole. In the vicinity of the inner periphery and the outer periphery of the film thickness, there is a “dense structure” in which there are many black and gray regions in the entire image, and this is a so-called “small virus capturing layer”. On the other hand, the central part of the film thickness is a “sparse structure” in which the polymer part is smaller than the vicinity of the inner periphery and the vicinity of the outer periphery, and plays a role of improving the permeability of useful proteins and maintaining the strength of the entire film.

  Moreover, it is preferable that the porous hollow fiber membrane of the present invention does not have macrovoids at least in the intermediate layer. “No macro voids” means that when a SEM image (1000x) of five different areas of the film thickness is observed with the naked eye, it is compared with the structure of the uniform film thickness in any field of view. Clearly, this means that a void region where a real part of the film is missing in a circular shape, an elliptical shape or a saddle shape, that is, a macro void is not observed. The presence of macrovoids is not preferable because it leads to a decrease in the strength of the entire hollow fiber membrane, which in turn may lead to defects in the capturing part.

  The porous hollow fiber membrane of the present invention comprises a hydrophobic polymer and a hydrophilic polymer. Examples of the hydrophobic polymer include polyester, polycarbonate, polyurethane, polyamide, polysulfone (hereinafter abbreviated as PSf), polyethersulfone (hereinafter abbreviated as PES), polymethyl methacrylate, polypropylene, polyethylene, PVDF, and the like. The Among them, polysulfone polymers such as PSf and PES having repeating units represented by the following formulas [I] and [II] are advantageous and preferable for obtaining a highly water-permeable membrane. The polysulfone polymer referred to here may contain a substituent such as a functional group or an alkyl group, and the hydrogen atom of the hydrocarbon skeleton may be substituted with another atom such as halogen or a substituent. These may be used alone or in combination of two or more. Here, the polysulfone polymer preferably has a high molecular weight. When the molecular weight is low, a homogeneous structure is not formed at the time of forming the hollow fiber membrane, and the phage clearance is lowered. Specifically, in the case of polyethersulfone, the reduced viscosity is 0.49 or more, preferably 0.50 or more, more preferably 0.51 or more. Although it is preferable that the reduced viscosity is large, the upper limit of the reduced viscosity of a commercially available polyethersulfone polymer is about 0.60. In the case of polyethersulfone, a normal separation membrane often uses a polymer having a reduced viscosity of 0.47 or less.

  Examples of the hydrophilic polymer include high molecular carbohydrates such as polyethylene glycol, polyvinyl alcohol, polyvinyl pyrrolidone (hereinafter abbreviated as PVP), carboxymethyl cellulose, and starch. Among these, PVP is preferable from the viewpoint of compatibility with the polysulfone polymer and its use as an aqueous fluid treatment membrane. These may be used alone or in admixture of two or more. As the molecular weight of PVP, those having a K value of 17 to 120 are preferably used. Specifically, for example, Luvitec (trade names) K17, K30, K60, K80, K85, K90 and the like commercially available from BASF are preferable, and Luvitec (trade names) K80, K85, K90 and the like are more preferable.

The porous hollow fiber membrane of the present invention preferably has a pure water permeation rate (hereinafter abbreviated as pure water flux) of 10 to 400 L / (h · m ² · bar). More preferably, it is 50-300L / (h * m < ² > * bar). The pure water flux is a standard indicating the pore diameter of the porous membrane. If the pure water flux is smaller than the above numerical value, the pore diameter becomes excessively small, and it may be difficult to efficiently permeate the protein. Moreover, since the amount of water permeation is small, the efficiency of filtrate recovery may be reduced. If the pure water flux is larger than the above numerical value, the pore diameter becomes excessively large, and it may be difficult to efficiently remove and remove a removal substance such as a virus.

  In the porous hollow fiber membrane of the present invention, it is preferable that the protein, which is a component to be recovered in the filtrate, exhibits high permeability through the filtration process. It is difficult to determine what degree of transmittance is required depending on the use, type, concentration, etc. of the protein, but it is preferably 95% or more in the present invention. If it is less than 95%, protein loss due to filtration will increase and productivity will decrease. Considering that the transmittance may decrease over time, and that the transmittance is preferably at least 95% throughout the entire filtration process, the transmittance retention is preferably at least 95%.

In the actual protein filtration process, filtration is performed at a maximum of about 50 to 200 L / m ² , and a membrane having a high filtration rate from the start of filtration to the initial stage is particularly preferred. In the protein filterability test of the hollow fiber membrane of the present invention, the time taken for 30 L / m ² filtration was used as the index. The reason is that if the filtration amount of the protein solution per unit membrane area is less than 30 L / m ² , there is a risk of underestimation when considering the actual process of the membrane, while if it exceeds 30 L / m ² , the experimental level mini Even if a module is used, the protein solution to be prepared becomes enormous, which is not realistic. From the above points, the time required for 30 L / m ² filtration was selected as an index for evaluating the permeability of protein in the membrane.

  In the present invention, a 0.25% immunoglobulin solution as a protein solution was filtered at a constant pressure of 1.0 bar over 120 minutes in a dead end, and a membrane filtration experiment was performed. The immunoglobulin used at this time is preferably an intravenous immunoglobulin preparation (hereinafter referred to as IVIG) from the viewpoint of availability and stability of quality. In general, IVIG is often supplied as a solution having a concentration of about 5% or a kit that can dissolve a lyophilized component to obtain a solution having a concentration of about 5%. Considering 0.1 to 0.5%, 5% of the stock solution was diluted and used as 0.25%.

In this invention, the filtration experiment for calculating | requiring the transmittance | permeability of an immunoglobulin solution and 30 L / m < ² > filtration time was calculated | required on the following measuring conditions. The liquid temperature was adjusted to 25 ° C.
(1) IVIG was diluted to 0.25% with PBS, and the pH was adjusted to 6.8.
(2) The solution was introduced into the hollow fiber membrane in a dry state, and filtered at a constant pressure of 1.0 bar over 120 minutes.
(3) From the start to the end of filtration, the filtration time and the filtrate recovery amount were recorded at points of 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, and 120 minutes.

  In the porous hollow fiber membrane of the present invention, the upstream side surface of the filtration may be the hollow fiber membrane lumen side or the outer side of the hollow fiber membrane, but from the durability against the pressure applied when the filtration is performed. The hollow fiber membrane lumen side is preferably the upstream side of filtration, and filtration is preferably performed from the inside toward the outside.

  The inner diameter of the porous hollow fiber membrane of the present invention is preferably 150 to 400 μm, more preferably 170 to 350 μm, and further preferably 180 to 300 μm. The film thickness is preferably 50 to 100 μm, more preferably 50 to 90 μm, and further preferably 55 to 80 μm. When the inner diameter is smaller than the above range, when filtration is performed from the inside to the outside, the pressure loss due to liquid passage increases, and the filtration pressure may become non-uniform in the length direction of the hollow fiber membrane. In addition, when a liquid to be processed containing a large amount of impurities and agglomerated components is introduced, a lumen in the liquid may be blocked due to components in the liquid to be processed. When the inner diameter is larger than the above range, the hollow fiber membrane is liable to be crushed or distorted. When the film thickness is smaller than the above range, the hollow fiber membrane tends to be crushed or distorted. When the film thickness is larger than the above range, the resistance when the liquid to be treated passes through the film wall increases, and the permeability may decrease.

  The porous hollow fiber membrane of the present invention preferably has a bacteriophage clearance index (LRV) of 4 or more, more preferably 5 or more. By having such characteristics, it can be preferably applied to virus removal from protein-containing liquids. The bacteriophage referred to here is preferably a bacteriophage having a diameter of 20 to 30 nm, such as PP7, φX174, and more preferably φX174 from the viewpoint of easy handling of host bacteria.

Care should also be taken in setting the filtration load when measuring the bacteriophage clearance index. Generally, the greater the filtration load on the membrane, the greater the risk that the membrane will break through and the phage will leak. The more filtration load, the more severe the evaluation. In an actual biopharmaceutical process, filtration of about 50 to 200 L / m ² is performed, and therefore it is preferable to apply a filtration load higher than this even when measuring bacteriophage clearance. In the present invention, considering this point, the filtration load at the time of bacteriophage clearance measurement is set to 300 L / m ² .

  As the method for producing the porous hollow fiber membrane of the present invention, a conventionally known method can be appropriately employed. For example, a hydrophobic polymer, a hydrophilic polymer, a solvent, and a non-solvent are mixed and dissolved, and defoamed. Is simultaneously discharged from the annular part and center part of the double-tube nozzle together with the core liquid as a film-forming solution, and led to the coagulation bath through the idle part (air gap part) to form a hollow fiber membrane (dry wet spinning method) ), A method of winding and drying after washing with water.

  Solvents used in the film-forming solution are N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP), N, N-dimethylformamide (hereinafter abbreviated as DMF), N, N-dimethylacetamide (hereinafter abbreviated as DMAc). ), Dimethyl sulfoxide (hereinafter abbreviated as DMSO), ε-caprolactam, etc., can be widely used as long as they are good solvents for hydrophobic polymers and hydrophilic polymers. When a polysulfone polymer such as PSf or PES is used, an amide aprotic solvent such as NMP, DMF, or DMAc is preferable, and NMP is particularly preferable. In the present invention, the amide solvent means a solvent containing an N—C (═O) amide bond in the structure, and the aprotic solvent is directly bonded to a hetero atom other than a carbon atom in the structure. Means a solvent containing no hydrogen atom.

  Further, it is preferable to add a non-solvent to the film forming solution. Examples of the non-solvent used include ethylene glycol (hereinafter abbreviated as EG), propylene glycol (hereinafter abbreviated as PG), diethylene glycol (hereinafter abbreviated as DEG), triethylene glycol (hereinafter abbreviated as TEG), Examples include polyethylene glycol (hereinafter abbreviated as PEG), glycerin, water, and the like. When a polysulfone polymer such as PSf or PES is used as the hydrophobic polymer and PVP is used as the hydrophilic polymer, DEG, Ether polyols such as TEG and PEG are preferred, and TEG is particularly preferred. In the present invention, the ether polyol means a substance having at least one ether bond and two or more hydroxyl groups in the structure.

  By using a membrane-forming solution prepared using these solvents and non-solvents, it is considered that phase separation (coagulation) in the spinning process is controlled, and it is advantageous to form a preferred membrane structure of the present invention. For controlling the phase separation, the composition of the core liquid described later and the composition of the liquid in the coagulation bath (external coagulation liquid) are also important.

  The solvent / non-solvent ratio in the film forming solution is an important factor for controlling phase separation (coagulation) in the spinning process. It is preferable that the non-solvent is the same amount or slightly excess with respect to the solvent. Specifically, the solvent / non-solvent is preferably 25/75 to 50/50 by weight, and 30/70 to 50 / 50 is more preferable, and 35/65 to 50/50 is still more preferable. If the content of the solvent is less than the above range, solidification proceeds, the membrane structure becomes too dense, and the permeability tends to decrease. Moreover, when there is more solvent content than the said range, advancing of phase-separation will be suppressed too much, a void | hole with a large pore diameter will arise, and the possibility of causing the fall of a separation characteristic and intensity | strength will become large.

  The concentration of the hydrophobic polymer in the film forming solution is not particularly limited as long as film formation from the solution is possible, but is preferably 10 to 40% by weight, more preferably 10 to 30% by weight, and 15 to 25% by weight. Is more preferable. In order to obtain high permeability, it is preferable that the concentration of the hydrophobic polymer is low. However, if the concentration is too low, strength may be lowered and separation characteristics may be deteriorated. The amount of hydrophilic polymer added is sufficient to impart hydrophilicity to the hollow fiber membrane and prevent non-specific adsorption during filtration of the liquid to be processed, without affecting the membrane formation from the membrane-forming solution. If it is, it will not restrict | limit in particular, However, 2-20 weight% is preferable as a density | concentration of the hydrophilic polymer in a film forming solution, and 3-15 weight% is more preferable. If the amount of the hydrophilic polymer added is small, hydrophilicity imparting to the film becomes insufficient, and the retention of film characteristics may be reduced. On the other hand, if the amount is too high, the hydrophilicity-imparting effect is saturated and the efficiency is not good, and the phase separation (or coagulation) of the film-forming solution is likely to proceed excessively, and the operability is deteriorated. It is disadvantageous to form a preferable film structure.

  It is preferable to add copper acetate to the film forming solution of the present invention in order to suppress radical generation. When copper acetate is not added to the film-forming solution, the throughput of the protein solution and the phage clearance are likely to decrease. In the absence of copper acetate, radicals are generated due to the influence of heat during the film-forming solution, which causes the hydrophilic polymer polyvinylpyrrolidone to be decomposed, thereby reducing the hydrophilicity of the membrane and the pore structure of the membrane. This is thought to be due to a negative impact on throughput and phage clearance. The amount of copper acetate added is preferably 0.25 to 5 ppm, more preferably 0.5 to 3 ppm. If the addition amount is less than this, the throughput and phage clearance are lowered as described above, and if it is more than this, the residual amount in the hollow fiber membrane is increased, which is not preferable as a hollow fiber membrane used for pharmaceutical production.

  The film-forming solution can be obtained by mixing a hydrophobic polymer, a hydrophilic polymer, a solvent, and a non-solvent, and dissolving them by stirring. At this time, the solution can be efficiently dissolved by appropriately applying the temperature, but excessive heating may cause decomposition of the polymer, so that it is preferably 30 to 100 ° C, more preferably 40 to 80 ° C. is there. When PVP is used as the hydrophilic polymer, PVP tends to undergo oxidative degradation due to the influence of oxygen in the air. Therefore, it is preferable to prepare the film-forming solution in an inert gas atmosphere. Examples of the inert gas include nitrogen and argon, but nitrogen is preferably used. At this time, the residual oxygen concentration in the dissolution tank is preferably 3% or less.

  In order to obtain a hollow fiber membrane free from defects, it is preferable to exclude bubbles from the membrane forming solution. As a method for suppressing the mixing of bubbles, it is effective to defoam the film forming solution. Depending on the viscosity of the film-forming solution, static defoaming or vacuum defoaming can be used. In this case, the inside of the dissolution tank is depressurized to normal pressure −0.015 to normal pressure −0.090 MPa, and then the tank is sealed and left to stand for 30 minutes to 180 minutes. This operation is repeated several times to perform a defoaming process. If the degree of vacuum is too low, the treatment may take a long time because it is necessary to increase the number of defoaming times. Moreover, when the pressure reduction degree is too high, the cost for raising the sealing degree of a system may become high. The total treatment time is preferably 5 minutes to 5 hours. If the treatment time is too long, the components of the film-forming solution may be decomposed and deteriorated due to the effect of reduced pressure. If the treatment time is too short, the defoaming effect may be insufficient. Further, a method can be adopted in which a depressurization portion is provided in a flow path for guiding the film forming solution from the tank to the nozzle, and defoaming is performed while the film forming solution is flowing. The degree of reduced pressure at this time is preferably normal pressure−0.005 to normal pressure−0.080 MPa.

  When film formation is performed, it is preferable to use a film formation solution from which foreign matters are excluded in order to avoid generation of defects in the membrane structure due to foreign matters mixed into the hollow fiber membrane. Specifically, a method of using a raw material with less foreign matter, filtering the film forming solution, and reducing foreign matter is effective. In the present invention, it is preferable to filter the membrane-forming solution using a filter having a pore size smaller than the thickness of the hollow fiber membrane bundle and then discharge from the nozzle. Specifically, the uniformly-dissolved membrane-forming solution is discharged from the dissolution tank. A sintered filter having a pore diameter of 10 to 50 μm provided while being led to the nozzle is passed. The filtration treatment may be performed at least once. However, when the filtration treatment is performed in several stages, it is preferable to reduce the pore diameter of the filter as it is in the latter stage in order to extend the filtration efficiency and the filter life. The pore size of the filter is more preferably 10 to 45 μm, further preferably 10 to 40 μm. If the filter pore size is too small, the back pressure may increase and productivity may decrease.

  As the composition of the core liquid used for forming the hollow fiber membrane, it is preferable to use a liquid mainly composed of a solvent and / or a non-solvent contained in the membrane forming solution. However, with only the solvent contained in the film forming solution, coagulation on the inner wall surface of the lumen is excessively suppressed, so that a preferable surface structure cannot be obtained. Therefore, it is preferable to use any of a mixed solution of a solvent and a non-solvent, a non-solvent alone, a mixed solution of a solvent and water, a mixed solution of a non-solvent and water, or a mixed solution of a solvent, a non-solvent, and water. The amount of the organic component contained in the core liquid is preferably 50 to 100% by weight, and more preferably 60 to 100% by weight. More specifically, when the core liquid is a mixed liquid of a solvent and water, the amount of the organic component is 50 to 65% by weight. When the core liquid is a mixed liquid of the non-solvent and water, the amount of the organic component is When the core solution is a mixed solution of solvent, non-solvent and water, the same as the solvent / non-solvent ratio of the film-forming solution is diluted with water, and the organic component concentration is 60% by weight. It is preferable to set it to -98 weight%. If the content of the organic component is less than this, solidification tends to proceed, the membrane structure becomes too dense, and the permeability decreases. On the other hand, if the content of the organic component is larger than this, the progress of phase separation is excessively suppressed, and pores having a large pore diameter are likely to be generated, which increases the possibility of degrading separation characteristics and strength.

  The composition of the external coagulation liquid is preferably a mixed liquid of a solvent and a non-solvent contained in the film forming solution and water. At this time, it is preferable that the ratio of the solvent and the non-solvent contained in the external coagulation liquid is the same as the solvent / non-solvent ratio of the film forming solution. The same solvent and non-solvent that are used for the film-forming solution are mixed in the same ratio as in the film-forming solution, and diluted by adding water to this is preferably used. The content of water in the external coagulation liquid is 30 to 90% by weight, preferably 40 to 80% by weight. If the water content is higher than this, solidification tends to proceed, the membrane structure becomes too dense, and the permeability decreases. On the other hand, if the water content is less than this, the progress of phase separation is excessively suppressed, and pores having a large pore diameter are likely to be generated, which increases the possibility of degrading separation characteristics and strength. On the other hand, when the temperature of the external coagulation liquid is low, coagulation tends to proceed, and the membrane structure may become too dense, resulting in a decrease in permeability. On the other hand, if it is high, the progress of the phase separation is excessively suppressed, and pores having a large pore diameter are likely to be generated, and the possibility of causing a reduction in separation characteristics and strength is increased. 65 ° C.

  A factor controlling the film structure also includes the temperature of the nozzle. If the temperature of the nozzle is low, solidification tends to proceed, the membrane structure becomes too dense, and the permeability decreases. On the other hand, if it is high, the progress of phase separation is excessively suppressed, and pores having a large pore diameter are likely to be generated, and the possibility of causing a decrease in separation characteristics and strength is increased. Therefore, 30 to 85 ° C., preferably 40 to 40 ° C. 75 ° C.

  As a method for producing a porous hollow fiber membrane of the present invention, a membrane forming solution discharged from a double tube nozzle together with a core liquid is introduced into a coagulating bath filled with an external coagulating liquid through an air gap portion to form a hollow fiber membrane. The dry-wet spinning method to be formed is exemplified, but the residence time in the air gap portion of the film-forming solution discharged from the nozzle can also be a factor for controlling the film structure. If the residence time is short, the outer coagulating liquid quenches the growth of aggregated particles due to phase separation in the air gap portion, so that the outer surface becomes dense and the permeability is lowered. In addition, the densification of the outer surface is not preferable because the obtained hollow fiber membrane tends to stick. If the residence time is long, pores having a large pore diameter are likely to be generated, and the possibility of deteriorating separation characteristics and strength is increased. The preferable range of the residence time in the air gap is 0.01 to 2 seconds, more preferably 0.02 to 1 second, and further preferably 0.02 to 0.5 seconds.

  The draft ratio in the air gap portion and the coagulation bath, that is, the ratio between the take-up speed from the coagulation bath and the film-forming solution discharge linear speed from the double tube nozzle can also be a factor controlling the film structure. The draft ratio mentioned here may be considered exclusively as the stretch ratio in the air gap part, but the orientation of the polymer chains can be adjusted by applying appropriate stretching in the air gap where the growth of the aggregated particles due to phase separation is suppressed. It is believed that this will affect the microstructure of the film.

  In order to simultaneously satisfy the orientation in the vicinity of the outer periphery and the orientation in the vicinity of the inner periphery of the hollow fiber membrane and lead each to a dense membrane structure, the draft ratio is preferably 4 to 20, preferably 4 to 15. When the draft ratio is smaller than this, the colloidal gold capturing layer appears only in the vicinity of the outer periphery, and as a result, there is a possibility that the removal effect of a substance to be removed such as a virus is not sufficiently exhibited. On the other hand, if the draft ratio is larger than this, the level of proper orientation is exceeded, and the pores of the membrane are deformed, which may cause a decrease in flux and a decrease in the permeability of useful proteins. If the draft ratio is further increased, even the skeleton structure of the membrane is destroyed, the strength is lowered, yarn breakage is likely to occur during spinning, and the risk that the operability is lowered increases.

  In addition, it is necessary to spin a membrane in which a colloidal gold capturing layer is expressed in the vicinity of the inner periphery and the outer periphery of the hollow fiber membrane by the above-described appropriate draft ratio in a state as close to non-stretching as possible in the subsequent steps. Spinning close to non-stretching means that the ratio of the speed at which the hollow fiber membrane is pulled up at the final stage of spinning and the take-up speed from the coagulation bath is close to 1. By such unstretched spinning, there is no possibility that the film structure of the colloidal gold capture layer, so-called dense layer, is deformed or destroyed. Specifically, the ratio of the scraping speed / take-off speed is preferably 0.99 to 1.15. If it is higher than this, the permeability of useful proteins may be reduced due to a decrease in flux. The speed ratio should be as low as possible, but if it is too low, the hollow fiber membrane running in the spinning process will sag and spinning will be impossible. The lifting speed is not particularly limited as long as a hollow fiber membrane having no defect can be obtained and productivity can be secured, but is preferably 5 to 40 m / min, more preferably 10 to 30 m / min. If the spinning speed is lower than this, productivity may be lowered. If the spinning speed is higher than this, it becomes difficult to ensure the above spinning conditions, particularly the residence time in the air gap portion and the residence time in the coagulation bath.

  After passing through the aforementioned air gap portion, the hollow fiber membrane guided to the coagulation bath contacts the external coagulation liquid in a state where coagulation from the outside proceeds to some extent while coagulation from the core liquid proceeds. During the passage of the external coagulation liquid, the hollow fiber membrane is completely solidified and the structure is determined and pulled up. The residence time in the coagulation bath is important for controlling the membrane structure, specifically, preferably 1 to 15 seconds, more preferably 2 to 10 seconds, and further preferably 2 to 5 seconds. If the residence time in the coagulation bath is shorter than this, coagulation is insufficient, and if it is longer than this, the film-forming speed is reduced and the coagulation bath needs to be enlarged.

  The hollow fiber membrane pulled up from the coagulation bath is guided to a washing bath filled with warm water and washed in a heated state, whereby a hollow fiber membrane having preferable separation characteristics, permeation characteristics, and membrane structure can be obtained. The temperature of the hot water is preferably 30 to 100 ° C, more preferably 40 to 90 ° C. There is a high possibility that the cleaning effect will be insufficient at a temperature lower than this, and water may not be used as the cleaning liquid at a temperature higher than this.

  The hollow fiber membrane obtained through on-line cleaning after film formation suppresses changes in membrane properties during use and washing operations, and ensures the retention and stability of membrane properties and the recovery of membrane properties. Heat treatment is preferably performed. By making this heat treatment an immersion treatment in hot water, the effect of washing and removing the solvent, non-solvent, etc. remaining in the hollow fiber membrane can be expected at the same time.

  The temperature of the hot water used for the heat treatment of the hollow fiber membrane is 40 to 100 ° C, more preferably 60 to 95 ° C, the treatment time is 30 to 90 minutes, more preferably 40 to 80 minutes, still more preferably 50 to 50 ° C. 70 minutes. If the temperature is lower than this and the processing time is shorter than this, the heat history applied to the hollow fiber membrane may be insufficient, and the retention and stability of the membrane characteristics may be lowered, and the cleaning effect is insufficient. Therefore, there is a high possibility that the amount of eluate increases. If the temperature is higher than this and the treatment time is longer than this, the water may boil or the treatment may take a long time, resulting in a decrease in productivity. The bath ratio of the hollow fiber membrane to hot water is not particularly limited as long as the hollow fiber membrane is sufficiently immersed in the hot water, but using too much hot water may reduce productivity. There is. Also, during this heat treatment, if the hollow fiber membrane is bundled in an appropriate length and immersed in hot water in an upright state, the hot water can easily reach the lumen portion, and the heat treatment / cleaning effect is improved. It is preferable from the viewpoint.

  The porous hollow fiber membrane of the present invention is preferably treated with high-pressure hot water immediately after the heat treatment. Specifically, it is preferably set in a high-pressure steam sterilizer in a submerged state and processed at a processing temperature of 120 to 140 ° C. and a processing time of 20 to 120 minutes, which are normal high-pressure steam sterilization conditions. At this time, it is preferable that the hollow fiber membrane which has been subjected to the heat treatment is immediately started to be subjected to the high-pressure hot water treatment in a wet state and in a high temperature state. By heat treatment, the membrane temperature rises and the high pressure hydrothermal treatment is performed in a “relaxed” state, so that the excess hydrophilic polymer is removed and at the same time the existence state is optimized and the permeation characteristics are optimized. It is thought. If the treatment temperature is lower than the above range, or if the treatment time is short, the treatment conditions are too mild to remove excess hydrophilic polymer and to optimize the existence state, resulting in changes in membrane characteristics over time. The possibility of causing problems such as contamination of the liquid to be treated due to elution during use is increased. When the processing temperature is higher than the above range, when the processing time is long, the processing conditions are harsh, leading to degradation of separation characteristics and strength due to destruction of the membrane structure, excessive extraction of hydrophilic polymer, etc. The potential will increase.

  The hollow fiber membrane that has been subjected to film formation, heat treatment, and high-pressure hydrothermal treatment is finally completed by drying. As a drying method, commonly used drying methods such as air drying, reduced pressure drying, hot air drying, and microwave drying can be widely used. In particular, microwave drying recently used for drying blood treatment membranes can be preferably used in that a large amount of hollow fiber membranes can be efficiently dried at a relatively low temperature. The temperature at the time of drying is room temperature to 70 ° C, preferably 30 to 65 ° C. If the temperature is lower than this, it takes a long time to dry, and if the temperature is higher than this, the energy cost for generating hot air becomes high, which is not preferable. In addition, when the hollow fiber membrane is dried to an absolutely dry state, it becomes difficult to maintain favorable permeation characteristics due to decomposition and migration of the hydrophilic polymer, and therefore the moisture content after the drying treatment is preferably Is preferably set to 1 to 12%, more preferably 2 to 10%. If the moisture content is lower than this, it is difficult to obtain preferable permeation characteristics. If the moisture content is higher than this, it is difficult to obtain a high moisture content and the handleability deteriorates.

  Hereinafter, the effectiveness of the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, the evaluation methods in the following examples are as follows.

1. Measurement of moisture content of hollow fiber membrane Using the hollow fiber membrane bundle obtained by spinning and post-treatment, the moisture content of the hollow fiber membrane was calculated by the following equation [1].
Hollow fiber membrane moisture content [%] = 100 × (W1 + W2) / W1 [1]
Here, W1 is the weight (g) of the hollow fiber membrane bundle obtained by spinning and post-treatment, and W2 is an absolutely dry hollow fiber obtained by drying this hollow fiber membrane bundle in a 120 ° C. dry heat oven for 2 hours. It is the weight (g) of the membrane bundle.

2. Production of Mini Module A hollow fiber membrane was cut into a length of about 30 cm and both ends were bundled with a paraffin film to produce a hollow fiber membrane bundle. Both ends of this hollow fiber membrane bundle were inserted into a pipe (sleeve) and hardened with a urethane potting agent. The ends were cut to obtain a double-end open mini-module with both ends fixed by sleeves. The number of hollow fiber membranes was appropriately set so that the surface area of the inner surface was 30 to 50 cm ² .

3. Production of Mini Module with Outer Tube A cylindrical tip with a side tube was attached to one end of a polyvinyl chloride tube (about 15 cm long) and the other end. Insert one to five hollow fiber membranes cut to a length of about 15 cm into this polyvinyl chloride tube with tips at both ends, and insert the tip portions at both ends so as not to block the hollow fiber membrane lumen. Was hardened with a silicone adhesive. This mini-module with an outer tube allows filtration from the lumen of the hollow fiber membrane toward the outer wall (inner-outer filtration) by introducing a liquid from the tip portion of the hollow tube into the lumen of the hollow fiber membrane. It is also possible to perform filtration (outside-inside filtration) from the outer wall toward the lumen by introducing the liquid from the outer wall.

4). Calculation of membrane area The membrane area of the module was determined based on the diameter near the inner periphery of the hollow fiber membrane. The membrane area A [m ² ] of the module can be calculated by the following equation [2].
A = n × π × d × L [2]
Here, n is the number of hollow fiber membranes, π is the circumference, d is the inner diameter [m] of the hollow fiber membrane, and L is the effective length [m] of the hollow fiber membrane in the module.

5. Measurement of pure water flux Connect a circuit to two end sleeves (referred to as lumen inlet and lumen outlet, respectively) of the mini-module, and measure the inflow pressure of liquid to the mini-module and the outflow pressure of liquid from the mini-module. I was able to measure. Pure water is placed in a pressurized tank and kept at 25 ° C, and the pressure is controlled by a regulator so that the filtration pressure is about 1.0 bar, while pure water is introduced into the lumen inlet of the mini module to form a hollow fiber membrane. The lumen was filled with pure water. The circuit (downstream from the pressure measurement point) connected to the inner surface outlet was sealed with forceps to stop the flow, and the pure water entered from the lumen inlet of the module was totally filtered. Subsequently, pure water was sent to the mini module, and filtration was performed for 30 seconds to acclimate the membrane. The filtrate during the acclimation treatment was discarded. Thereafter, the amount of filtrate obtained from the outer surface of the hollow fiber membrane was recovered over 2 minutes, and the amount was measured. Further, the lumen inlet side pressure Pi and the lumen outlet side pressure Po at the time of filtration were measured, and the transmembrane pressure difference (TMP) ΔP was obtained by the following equation [3].
ΔP = (Pi + Po) / 2 [3]
From the filtration time t [h], TMPΔP [bar], the membrane area A [m ² ] of the mini-module, and the filtrate amount V [L], the pure water flux [L / (h · m ² · bar) is obtained according to the following equation [4]. ] Was obtained.
Pure water flux = V ÷ t ÷ A ÷ ΔP [4]

6). Immunoglobulin Permeation Test 9.6 g of Dulbecco's PBS (-) powder “Nissui” commercially available from Nissui Pharmaceutical Co., Ltd. was dissolved in distilled water to make a total volume of 1000 mL to obtain PBS. With this buffer solution, blood donated venoglobulin-IH Yoshitomi marketed by Mitsubishi Tanabe Pharma Corporation was diluted and adjusted to a pH of 6.8 with a 1 mol / L sodium hydroxide aqueous solution. The immunoglobulin concentration after dilution and pH adjustment was adjusted to 0.25% (hereinafter, this solution is abbreviated as IVIG / PBS). Circuits were connected to the two end tips (referred to as the lumen inlet and the lumen outlet, respectively) of the mini-module with the outer cylinder to enable liquid introduction / extraction into the hollow lumen of the hollow fiber membrane. The liquid inlet pressure can be measured on the liquid inlet side. The liquid outlet side was sealed with forceps to stop the flow, and the total amount of liquid entered from the lumen inlet of the module was filtered. IVIG / PBS was placed in a pressurized tank and kept at 25 ° C., and the pressure was controlled with a regulator so that the filtration pressure was 1.0 bar, and the IVIG / PBS was introduced into the lumen of the mini-module with an outer cylinder. The filtrate obtained from the outer surface of the hollow fiber membrane was collected from the side tube of the chip. The filtrate is received by changing the container at each time point of 10 minutes, 20 minutes, 40 minutes, 60 minutes, 80 minutes, 100 minutes, 120 minutes from the start of filtration (time point of n minutes from the start of filtration is referred to as Tn). It was. At this time, the filtrate collection amount of each fraction was measured by weight at each point. At this time, the filtrate collection amount of each fraction was read from the value displayed on the electronic balance. Throughput TPn [L / m ² ] up to time Tn was calculated by the following equation [5].
TPn = Wn ÷ 1.0 ÷ A ÷ 1000 [5]
Here, W is the total amount of filtrate recovered up to the fraction at the start of filtration n minutes [g], 1.0 is the density of IVIG / PBS [g / cc], and A is the membrane area [m ² ] of the module. is there.

7). Analysis of the relationship between immunoglobulin filtration time and filtrate recovery integrated amount (throughput) Filtration time Tn obtained in the above filtration test and the numerical value of throughput TPn up to the time of the filtration time are calculated on a spreadsheet software on a personal computer (Microsoft Excel) ) To calculate “time taken to filter 30 L / m ² ”.

8). Measurement of immunoglobulin permeability The immunoglobulin permeability P was calculated by the following equation [6] from the filtrate of each fraction obtained in the filtration test and IVIG / PBS as the filtrate.
P = 100 [%] × (protein concentration in filtrate) / (protein concentration of filtrate IVIG / PBS) [6]
Here, the protein concentration of the filtrate IVIG / PBS and the protein concentration in the filtrate were determined by measuring the absorbance at 280 nm and calculating the concentration from a calibration curve prepared with an immunoglobulin solution having a known concentration.

9. Measurement of clearance index of bacteriophage φX174 (1) Preparation of test phage solution Albumin from bovine serum (product number A2153) commercially available from Sigma-Aldrich Japan Co., Ltd. was prepared using PBS prepared by the above-described method. 0.1% by weight BSA solution (hereinafter simply referred to as BSA solution) was obtained by dissolution to 1% by weight. A concentrated cryopreserved solution containing φX174 (titer 1 to 10 × 10 ⁹ pfu / mL) was thawed and diluted 100 times with this BSA solution. Further, the solution was filtered with a membrane filter having a pore size of 0.1 μm to remove aggregated components and the like to obtain a test phage solution.

(2) Filtration test using a phage solution for testing A circuit is connected to two end chips (referred to as a lumen inlet and a lumen outlet, respectively) of a mini module with an outer cylinder, and the liquid into the hollow fiber membrane lumen The introduction was made possible. The liquid inlet pressure can be measured on the liquid inlet side. The liquid outlet side was sealed with forceps to stop the flow, and the total amount of liquid entered from the lumen inlet of the module was filtered. The test phage solution was placed in a pressurized tank, kept at 25 ° C., and introduced into the lumen of the mini-module with an outer cylinder while controlling the pressure with a regulator so that the filtration pressure was 1.0 bar. The filtrate obtained from the outer surface of the hollow fiber membrane was collected from the side tube of the chip. Filtration was performed until a 300 L filtrate was obtained per 1 m ² of the hollow fiber membrane area.

(3) Phage titration measurement of test phage solution and filtrate Escherichia coli was suspended in 10 mM MgSO ₄ aqueous solution so that the absorbance at 660 nm was 4.0 (hereinafter referred to as E. coli solution). ). In addition, an agar medium and top agar were prepared and warmed to 50 ° C. in advance. Especially the top agar was careful to keep the fluidity. 10 μL of a test phage solution appropriately diluted with a BSA solution; Coli solution (50 μL) was mixed and incubated at 37 ° C. for 20 minutes to infect phages in E. coli. After completion of the incubation, the total amount of this mixed solution was mixed with 3 mL of top agar, and the entire amount was rapidly developed on an agar medium. After the top agar was completely solidified on the agar medium, it was incubated at 37 ° C. for 2 to 4 hours. After completion of the incubation, the number of plaques on the agar medium was counted, and the titer of the test phage solution (hereinafter abbreviated as Tpre) [pfu / mL] was calculated in consideration of the dilution rate. The phage titer (hereinafter abbreviated as Tpost) of the filtrate was obtained in the same manner.

(4) Phage Clearance Index Calculation of Hollow Fiber Membrane The phage clearance index of the hollow fiber membrane was calculated by the following formula [7]. Here, Tpre [pfu / mL] is the titer of the test phage solution introduced into the evaluation hollow fiber membrane, and Tpost [pfu / mL] is the test phage solution filtered through the evaluation hollow fiber membrane. It is a phage titer of the filtrate obtained by this.
Phage clearance index [LRV] = log ₁₀ (Tpre / Tpost) [7]

10. Measurement of clearance index of bacteriophage φX174 at high load In the same manner as described above, the filtrate was recovered from the point in time when the filtration amount per 1 m ² of the hollow fiber membrane area exceeded 200 L, and the above method was performed using this recovered filtrate. Was used to determine the phage clearance index.

11. Capture test using colloidal gold (1) Preparation of gold colloid dispersion liquid Commercially available 10 nm or 20 nm colloidal gold colloid (manufactured by Sigma) (containing a small amount of citric acid, stabilizer and dispersant) 6 ml and 2.0% After mixing 3 ml of bovine serum albumin (manufactured by Nacalai Tesque), 3 ml of 0.4% glutathione (reduced) aqueous solution was added.

(2) Evaluation of fractionated layer of hollow fiber membrane The prepared 10 nm or 20 nm gold colloid dispersion was filtered into a minimodule under a pressure of 1 bar. The gold colloid dispersion was filtered at 10 L / m ² and then filtered again with the same amount of distilled water. About the cross section of the film | membrane, the capture | acquisition state of the gold colloid was observed at 500-times multiplication factor using the optical microscope (VHX-1000 by Keyence Corporation).

12 Measurement of Thickness and Position of Capture Layer The film subjected to the 20 nm gold colloid capture test was observed at 500 times using an optical microscope. The thickness of the part dyed by the gold colloid was determined from the image. Specifically, five points were arbitrarily measured with a ruler, and the average value was taken as the thickness of the trapping layer.
Further, the position of the trapping layer was measured by the following method. The film subjected to the 20 nm gold colloid capture test was observed at 500 times using an optical microscope. For the trapping layer near the inner periphery, measure the radial distance from the inner surface to the portion (innermost) stained with gold colloid with a ruler to obtain an average value, which is measured by the film thickness measurement described later. Dividing by the film thickness obtained, the position was determined as a percentage. For the trapping layer near the outer periphery, measure the distance in the radial direction from the outer surface to the portion stained with the gold colloid (outermost) with a ruler at five points to obtain an average value, and similarly divide by the film thickness The position was determined as a percentage.

13. Measurement of pore diameter of trapping layer The colloidal gold solution of 10 nm filtered in (2) was measured with a scanning electron microscope (VE-9800 manufactured by Keyence Corporation) at a magnification of 100,000, and n = 50 particle sizes were measured. Asked. This maximum particle size was taken as the minimum pore size of the dense layer.
Next, the maximum pore diameter was determined by the bubble point method. Specifically, a hollow fiber membrane module with one end bonded and sealed was immersed in Porous Materials' Galwick, pressurized from the hollow side, and the maximum pore diameter was calculated from the pressure at which bubbles were confirmed at regular intervals.
Maximum pore diameter (nm) = 28.6 × 15.9 ÷ pressure value (bar)

14 Measurement of the inner diameter and thickness of the hollow fiber membrane The inner diameter, outer diameter, and thickness of the hollow fiber membrane are appropriately adjusted so that the hollow fiber membrane does not fall out into a hole of φ3 mm formed in the center of the slide glass. After the sample is cut with a razor on the upper and lower surfaces of the slide glass to obtain a hollow fiber membrane cross section sample, it is obtained by measuring the short diameter and long diameter of the cross section of the hollow fiber membrane using a projector Nikon-V-12A. Measure the short axis and long axis in two directions for each cross section of the hollow fiber membrane, and calculate the arithmetic average value of each of the cross section of the hollow fiber membrane as the inner diameter and outer diameter of one hollow fiber membrane. did. The same measurement was performed on five cross sections, and the average value was defined as the inner diameter and film thickness.

15. Pressure resistance test of hollow fiber membrane Pressurized air was sent to the hollow portion side of the mini module, and the pressure (MPa) at which the hollow fiber membrane burst was read. In view of the capability of the apparatus, the maximum pressurization value is 0.82 MPa, and when it does not burst even at this pressure, it is expressed as> 0.82 MPa.

Example 1
PES (BASF Ultrason (trade name) E6020P reduced viscosity 0.59) 20 parts by weight, BASF PVP (Luvitec (trade name) K90PH) 6 parts by weight, Mitsubishi Chemical Corporation NMP 33.3 parts by weight, Mitsui Chemicals, Inc. 40.6999 parts by weight of TEG manufactured and 0.0001 parts by weight of copper acetate manufactured by Wako Pure Chemical Industries, Ltd. were mixed and dissolved at 55 ° C. for 6 hours to obtain a uniform solution. At this time, the inside of the system was repeatedly purged with nitrogen several times by reducing pressure and introducing nitrogen, and a solution was prepared in a sealed state. After preparing the solution, the pressure was reduced to normal pressure -0.09 MPa at 55 ° C., and then the system was immediately sealed and left to stand for 30 minutes so that the solvent and the like would volatilize and the solution composition would not change. Further, the solution was continuously defoamed in a reduced pressure portion provided in a flow path connecting the tank to the nozzle, and then introduced into the nozzle. At this time, the temperature of the flow path was 55 ° C., and the degree of pressure reduction in the reduced pressure portion was normal pressure −0.050 MPa.

  The film-forming solution is discharged from the annular part of the double tube nozzle, and a mixed liquid of 38.25 parts by weight of NMP, 46.75 parts by weight of TEG and 15 parts by weight of RO water is discharged from the center part as a core liquid, and through a 15 mm air gap. , 27 parts by weight of NMP, 33 parts by weight of TEG, and 40 parts by weight of RO water were introduced into a coagulation bath filled with an external coagulation liquid. At this time, the nozzle temperature was set to 55 ° C., and the external coagulation liquid temperature was set to 60 ° C. The hollow fiber membrane pulled up from the coagulation bath was led to a washing tank filled with 55 ° C. warm water.

  The spinning speed was 22.2 m / min, the running length of the hollow fiber membrane in the coagulation bath was 450 mm, and the residence time in the coagulation bath was 1.22 seconds. The running length was set so that the residence time in the washing tank was 30 seconds. The hollow fiber membrane was controlled in terms of the amount of the membrane-forming solution and core solution discharged so that the inner diameter was about 200 μm and the film thickness was about 60 μm. The air gap residence time of the hollow fiber membrane calculated from the above conditions was 0.04 seconds. The draft ratio was 10.5, and the ratio of the lifting speed / take-off speed was 1.01.

  The wound hollow fiber membranes were bundled with a number of 5600 and a length of 40 cm, and the core liquid was removed. Then, it was immersed in 80 degreeC RO water for 60 minutes in the upright state, and the hot water process was performed. The hollow fiber membrane that had been subjected to the heat treatment was immediately submerged in a high-pressure steam sterilizer containing hot water at 40 ° C. in a wet state, and subjected to high-pressure hot water treatment under conditions of 132 ° C. × 20 minutes.

  Next, 48 hollow fiber membrane bundles are placed on a rotary table and placed in a microwave drying apparatus (HD-12R manufactured by Chiyoda Seisakusho Co., Ltd.), irradiated with 8 kW of microwaves, and the inside of the drying apparatus is reduced to 7 kPa for 27 minutes. A drying treatment was performed. Subsequently, the microwave output was set to 3.5 kW, a drying process was performed for 7 minutes under a reduced pressure of 7 kPa, and the microwave output was further reduced to 2 kW to complete the drying for 5 minutes. Further, the hollow fiber bundle was submerged once more in a high-pressure steam sterilizer containing warm water at 40 ° C., and subjected to high-pressure hot water treatment under conditions of 132 ° C. × 20 minutes. Subsequently, microwave drying was performed as before. The maximum temperature reached on the hollow fiber membrane surface in the drying step was 60 ° C., and the moisture content of the dry hollow fiber membrane was 3.3%. Through the above steps, a hollow fiber membrane (A) having an inner diameter of 198 μm and a film thickness of 59 μm was obtained.

As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured (FIG. 11). Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity (FIG. 1). Further, when this hollow fiber membrane (A) was observed with a transmission electron microscope (JEM-2100 manufactured by JEOL Ltd.) at a magnification of 2000 times, the membrane structure was dense in the vicinity of the inner periphery and the vicinity of the outer periphery (black and gray portions). (FIGS. 4 and 6), it was confirmed that the central part has a sparse film structure (FIGS. 5 and 3). When observed at 500 times with a scanning electron microscope, the central region of the film thickness portion of the hollow fiber membrane (A) has a substantially homogeneous structure, and the film thickness portion has a structure substantially free of macrovoids. It was. The thickness of the trapping layer near the inner periphery was 5 μm, and the thickness of the trapping layer near the outer periphery was 12 μm. Further, the trapping layer near the inner periphery was at a position of approximately 18% from the inner surface, and the trapping layer near the outer periphery was at a position of approximately 25% from the outer surface. Further, the trapping layer had a minimum pore size of 11 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (A) are shown in Table 1. In evaluating the hollow fiber membrane, pure water flux was measured and an immunoglobulin permeation test was performed. Then, using the filtrate obtained at the time of filtration of 30 L / m ² and the filtration time at 120 minutes obtained in the immunoglobulin permeation test, the immunoglobulin permeability was measured by the method described above. . Moreover, the clearance index (hereinafter abbreviated as φX174-CL300) of bacteriophage φX174 at the time of 300 L of filtration load per 1 m ^{2 of the} hollow fiber membrane area was measured.

(Example 2)
A hollow fiber membrane (B) was obtained in the same manner as in Example 1 except that the BASF PVP was changed to (Luvitec (trade name) K85PH). As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) in the inner periphery and the vicinity of the outer periphery, but the film structure was sparse in the central portion. As a result of SEM observation, the central region of the film thickness portion of the hollow fiber membrane (B) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the trapping layer near the inner periphery was 4 μm, and the thickness of the trapping layer near the outer periphery was 11 μm. Further, the trapping layer present in the vicinity of the inner periphery was 17% from the inner surface, and the trapping layer present in the vicinity of the outer periphery was 25% from the outer surface. Further, the trapping layer had a minimum pore size of 12 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (B) are shown in Table 1.

(Example 3)
A hollow fiber membrane (C) was obtained in the same manner as in Example 1 except that the draft ratio was changed to 17.0. The maximum temperature reached on the hollow fiber membrane surface in the drying step was 60 ° C., and the moisture content of the dry hollow fiber membrane was 3.1%. As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) in the inner periphery and the vicinity of the outer periphery, but the film structure was sparse in the central portion. When SEM observation was performed, the central region of the film thickness portion of the hollow fiber membrane (C) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the capturing layer existing in the vicinity of the inner periphery was 5 μm, and the thickness of the capturing layer existing in the vicinity of the outer periphery was 12 μm. Further, the trapping layer present in the vicinity of the inner periphery was 19% from the inner surface, and the trapping layer present in the vicinity of the outer periphery was 26% from the outer surface. Further, the trapping layer had a minimum pore size of 11 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (C) are shown in Table 1.

Example 4
A hollow fiber membrane (D) was obtained in the same manner as in Example 1 except that the ratio of the lifting speed / take-off speed was changed to 1.20. The maximum temperature reached on the hollow fiber membrane surface in the drying step was 60 ° C., and the moisture content of the dry hollow fiber membrane was 3.6%. As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the cross section of the film subjected to the gold colloid capturing test of 20 nm with an optical microscope, the gold colloid was captured in the vicinity of the inner periphery and the vicinity of the outer periphery. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) near the inner periphery and the outer periphery, but the film structure was sparse in the central portion. When SEM observation was performed, the central region of the film thickness portion of the hollow fiber membrane (D) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the trapping layer near the inner periphery was 3 μm, and the thickness of the trapping layer near the outer periphery was 11 μm. Further, the trapping layer present in the vicinity of the inner periphery was 18% from the inner surface, and the trapping layer present in the vicinity of the outer periphery was 24% from the outer surface. Furthermore, the minimum pore size of the trapping layer was 12 nm, and the maximum pore size was 37 nm. The details and evaluation results of the hollow fiber membrane (D) are shown in Table 1.

(Example 5)
A hollow fiber membrane (E) was obtained in the same manner as in Example 1 except that the draft ratio was changed to 3.5 and the ratio of the lifting speed / take-off speed was changed to 1.15. The maximum temperature reached on the surface of the hollow fiber membrane in the drying step was 60 ° C., and the moisture content of the dry hollow fiber membrane was 2.9%. As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) in the inner periphery and the vicinity of the outer periphery, but the film structure was sparse in the central portion. When SEM observation was performed, the central region of the film thickness portion of the hollow fiber membrane (E) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the trapping layer near the inner periphery was 3 μm, and the thickness of the trapping layer near the outer periphery was 11 μm. Further, the trapping layer present in the vicinity of the inner periphery was 17% from the inner surface, and the trapping layer in the vicinity of the outer periphery was 25% from the outer surface. Further, the trapping layer had a minimum pore size of 12 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (E) are shown in Table 1.

(Example 6)
A hollow fiber membrane (F) was obtained in the same manner as in Example 1 except that PES was changed to Sumika Excel (registered trademark) 5200P (reduced viscosity 0.52) manufactured by Sumitomo Chemtech. The maximum temperature reached on the hollow fiber membrane surface in the drying step was 60 ° C., and the moisture content of the dry hollow fiber membrane was 3.6%. As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) in the inner periphery and the vicinity of the outer periphery, but the film structure was sparse in the central portion. When SEM observation was performed, the central region of the film thickness portion of the hollow fiber membrane (F) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the capturing layer existing in the vicinity of the inner periphery was 5 μm, and the thickness of the capturing layer existing in the vicinity of the outer periphery was 12 μm. Further, the trapping layer present in the vicinity of the inner periphery was 19% from the inner surface, and the trapping layer present in the vicinity of the outer periphery was 25% from the outer surface. Further, the trapping layer had a minimum pore size of 12 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (F) are shown in Table 1.

(Example 7)
A hollow fiber membrane (G) was obtained in the same manner as in Example 1 except that the polysulfone-based polymer was PSf (P-3500 manufactured by Amoco Co., Ltd .: reduced viscosity 0.6). As a result of observing the cross section of the film subjected to the 10 nm colloidal gold capture test with an optical microscope, the colloidal gold was not captured. Moreover, as a result of observing the film | membrane cross section which implemented the gold colloid capture test of 20 nm with an optical microscope, the gold colloid was trapped by inner periphery and outer periphery vicinity. Further, when observed with a transmission electron microscope, it was confirmed that the film structure was dense (black and gray portions) in the inner periphery and the vicinity of the outer periphery, but the film structure was sparse in the central portion. As a result of SEM observation, the central region of the film thickness portion of the hollow fiber membrane (G) had a substantially homogeneous structure and a structure substantially free of macrovoids in the film thickness portion. The thickness of the capturing layer existing in the vicinity of the inner periphery was 5 μm, and the thickness of the capturing layer existing in the vicinity of the outer periphery was 12 μm. Further, the trapping layer present in the vicinity of the inner periphery was 18% from the inner surface, and the trapping layer present in the vicinity of the outer periphery was 26% from the outer surface. Further, the trapping layer had a minimum pore size of 11 nm and a maximum pore size of 36 nm. The details and evaluation results of the hollow fiber membrane (G) are shown in Table 1.

(Comparative Example 1)
A hollow fiber membrane (H) was obtained in the same manner as in Example 1 except that the draft ratio was changed to 17.0 and the ratio of the lifting speed / take-off speed was changed to 1.23. As a result of observing the cross section of the film subjected to the 10 nm or 20 nm gold colloid capture test with an optical microscope, the 20 nm gold colloid was captured near the inner periphery and the outer periphery, and further, the 10 nm gold colloid was also captured near the outer periphery. The thickness of the acquisition layer existing in the vicinity of the inner periphery was 6 μm, and the thickness of the acquisition layer existing in the vicinity of the outer periphery was 13 μm. Further, the trapping layer present near the inner periphery was 17% from the inner surface, and the trapping layer present near the outer periphery was 24% from the outer surface. Furthermore, the minimum pore size of the trapping layer was 9 nm, and the maximum pore size was 35 nm.
Further, the pure water flux was 31 L / (h · m ² · bar), which was greatly reduced as compared with the Examples, and the immunoglobulin permeability was as low as 93%. From these results, when the draft ratio was too large, the level of the proper orientation was exceeded, and the pores of the membrane were deformed, causing the capture of 10 nm gold colloid, the decrease in flux, and the decrease in the permeability of useful proteins. there is a possibility.
If the immunoglobulin permeability is less than 95%, protein loss due to filtration increases and productivity decreases, which is not practical. The details and evaluation results of the hollow fiber membrane (H) are shown in Table 1.

(Comparative Example 2)
A hollow fiber membrane (I) was obtained in the same manner as in Example 1 except that the draft ratio was changed to 2.0 and the ratio of the lifting speed / take-off speed was changed to 0.98. As a result of observing the cross section of the film subjected to the 10 nm or 20 nm gold colloid capture test with an optical microscope, the 10 nm gold colloid was not captured, whereas the 20 nm gold colloid was captured only in the vicinity of the outer periphery (FIG. 2). . When observed with a transmission electron microscope, the film structure was dense (black and gray) only in the vicinity of the outer periphery (FIG. 10), but it was confirmed that the film structure was sparse in the vicinity of the inner periphery and in the central part. (FIGS. 7, 8, and 9). The thickness of the trapping layer present in the vicinity of the outer periphery was 9 μm. The trapping layer present in the vicinity of the outer periphery was at a position 25% from the outer surface. Furthermore, the minimum pore diameter of the trapping layer was 13 nm or more, and the maximum pore diameter was 42 nm.
Further, as a result of measuring the clearance index of bacteriophage φX174 (hereinafter abbreviated as φX174-CL300) at the time of filtration load of 300 L per 1 m ^{2 of} hollow fiber membrane area, the performance was insufficient as a virus removal membrane as low as 3.1. Met. From these results, if the draft ratio is too small, the orientation in the vicinity of the outer periphery and the orientation in the vicinity of the inner periphery of the hollow fiber membrane did not occur at the same time, and each led to a dense membrane structure. There was a possibility that the trapping layer was not expressed and the virus removal effect was not sufficiently exhibited. The details and evaluation results of the hollow fiber membrane (I) are shown in Table 1.

(Comparative Example 3)
The hollow fiber membrane described in Example 1 (PES uses Sumika Excel 4800P manufactured by Sumitomo Chemtech Co., Ltd .: reduced viscosity 0.48) was used as the hollow fiber membrane (J). As a result of observing the cross section of the film subjected to the 20 nm gold colloid capture test with an optical microscope, no 20 nm gold colloid was captured anywhere.
Moreover, as a result of measuring the clearance index of bacteriophage φX174 at the time of 300 L of filtration load per 1 m ^{2 of the} hollow fiber membrane area, it was as low as 3.5 and was insufficient as a virus removal membrane.
From these results, when a hydrophobic polymer having a low reduced viscosity, in other words, a hydrophobic polymer having a low molecular weight is used, a homogeneous structure is not formed during the formation of the hollow fiber membrane, and the phage clearance may be lowered. The details and evaluation results of the hollow fiber membrane (J) are shown in Table 1.

  The porous hollow fiber membrane of the present invention is capable of separating and removing a removal substance such as a virus with a high phage clearance index while efficiently passing through a useful collection substance such as a protein. It is useful for the industry and greatly contributes to the industry.

Claims (9)

When a colloidal gold particle having a particle diameter of 20 nm is subjected to constant pressure filtration, comprising a hydrophobic polymer and a hydrophilic polymer, it has a trapping layer in the vicinity of the inner periphery and the outer periphery of the film thickness portion. to the outer vicinity from the vicinity dense - sparse - be made of dense structure, when pressure filtered colloidal gold particles having a child size 10 nm, the colloidal gold film thickness portion is not caught, and the permeation rate of the pure water is 10 A porous hollow fiber membrane for treating protein-containing liquid, characterized by being 400 L / (h · m ² · bar) .   2. The porous hollow fiber membrane for protein-containing liquid treatment according to claim 1, wherein a thickness of the capturing layer existing in the vicinity of the inner periphery and in the vicinity of the outer periphery is 1 to 15 μm.   2. The porous hollow fiber for protein-containing liquid treatment according to claim 1, wherein the vicinity of the inner periphery and the vicinity of the outer periphery indicate a range from the inner surface and the outer surface of the hollow fiber membrane to 30% of the film thickness, respectively. film.   4. The porous for protein-containing liquid treatment according to claim 3, wherein the vicinity of the inner periphery and the vicinity of the outer periphery indicate a range of 1 to 30% of the film thickness from the inner surface and the outer surface of the hollow fiber membrane, respectively. Hollow fiber membrane.   The porous hollow fiber membrane for protein-containing liquid treatment according to any one of claims 1 to 4, wherein the pore diameter of the capturing layer existing in the vicinity of the inner periphery and in the vicinity of the outer periphery is 10 to 40 nm.   The porous hollow fiber membrane for protein-containing liquid treatment according to any one of claims 1 to 5, wherein the inner diameter is 150 to 400 µm and the film thickness is 50 to 100 µm.   The porous hollow fiber membrane for protein-containing liquid treatment according to any one of claims 1 to 6, wherein the hydrophobic polymer is a polysulfone polymer.   The porous hollow fiber membrane for protein-containing liquid treatment according to any one of claims 1 to 7, wherein the hydrophilic polymer is polyvinylpyrrolidone.   The porous hollow fiber membrane for protein-containing liquid treatment according to any one of claims 1 to 8, which is a membrane used for separating a virus from a protein solution.