JP2005342094A - Highly water permeable hollow fiber membrane type blood purification apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a medical hollow fiber type blood purification apparatus which is excellent in safety and in assembling modules and shows highly water permeable performance for the treatment of chronic renal failure. <P>SOLUTION: The hollow fiber membrane is made of a polysulfone system polymer containing a hydrophilic polymer. The hollow fiber membrane having a thickness of the membrane of 10-50 μm, an ratio of opening of an outer surface of 8-25%, a degree of uneven thickness of 0.6 or more, a ratio of the hydrophilic polymer on the outer surface of 25-50 percent by mass, an elution of the hydrophilic polymer from the hollow fiber membrane of 10 ppm or less, a burst pressure of the hollow fiber membrane of 0.5-2.0 MPa, and a rate of content of a soluble cyclic dimer of 1.0 percent or less by mass to the polysulfone system polymer is housed in the blood purification apparatus. The high performance hollow fiber membrane type blood purification apparatus is characterized with a coefficient of water permeability of 150 ml/m<SP>2</SP>/hr/mmHg or more. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a medical highly permeable hollow fiber blood purifier having excellent water permeability and used for the treatment of chronic renal failure, excellent in safety and module assembly.

  In blood purification therapy for the treatment of renal failure, natural materials such as cellulose, cellulose diacetate and cellulose triacetate, and synthetic polymers such as polysulfone, Modules such as hemodialyzers, hemofilters or hemodialyzers using dialysis membranes using polymers such as methyl methacrylate and polyacrylonitrile and ultrafiltration membranes as separation materials are widely used. In particular, modules using hollow fiber membranes as separation materials are important in the dialyzer field due to advantages such as reduction of the amount of blood circulating outside the body, high efficiency of removing substances in the blood, and productivity during module production. high.

  A dialysis module using a hollow fiber membrane usually causes blood to flow in the hollow part of the hollow fiber and counterflow of the dialysate to the outer part, and low mass of urea, creatinine, etc. by mass transfer based on diffusion from the blood to the dialysate. The main goal is to remove molecular weight substances from the blood. Furthermore, with the increase in the number of long-term dialysis patients, dialysis complications have become a problem. In recent years, substances to be removed by dialysis are not only low molecular weight substances such as urea and creatinine, but also from medium molecular weights of several thousand to molecular weights of 1 to 20,000. It is required for blood purification membranes to expand to high molecular weight substances and to remove these substances. In particular, β2 microglobulin with a molecular weight of 11700 has been found to be a causative substance of carpal tunnel syndrome and is a removal target. In order to obtain a membrane used for the treatment of such high molecular weight substance removal, the pore diameter of the membrane is increased, the number of pores is increased, the porosity is increased, or the film thickness is increased as compared with the conventional dialysis membrane. It is preferable to reduce the thickness and increase the water permeability of the membrane.

  However, in order to increase the water permeability, as described above, improvements such as increasing the pore diameter of the membrane, increasing the number of pores, increasing the porosity, and reducing the film thickness are necessary. It is. When this improvement is made, the elution of the hydrophilic polymer increases, and the problems that the film strength is lowered arise. If elution of the hydrophilic polymer increases, the accumulation of the hydrophilic polymer, which is a foreign substance, in the human body during long-term dialysis increases, which may cause side effects and complications. In addition, the decrease in film strength leads to problems such as damage to the yarn during the manufacturing process, transportation process, and handling, breakage of the yarn, and blood leakage during treatment.

As means for suppressing blood leakage, a technique for further reducing the concentration of the organic solvent in the conventional aqueous solution containing an organic solvent and finding an appropriate range of the gas phase passage time after the nozzle discharge and the concentration of the core is disclosed. Yes. (For example, see Patent Document 1). That is, it is a method of forming a thin dense layer on the inner surface of the membrane while controlling water permeability. However, the formation state of the dense layer on the inner surface of the membrane significantly affects water permeability, making it difficult to narrow the range of water permeability.
JP 2000-107577 A

  Furthermore, increasing the pore diameter of the membrane, increasing the number of pores, and increasing the porosity increase the amount of hydrophilic polymer present on the outer surface of the membrane, which allows dialysis. Endotoxin (endotoxin) contained in the solution is more likely to enter the blood side, leading to side effects such as fever, or hydrophilic polymers present on the outer surface of the membrane when the membrane is dried The hollow fiber membranes stick together (adhere) and cause problems such as deterioration in module assembly.

Among the above-mentioned problems, with regard to the problem that endotoxin (endotoxin) enters the blood side, a method using the characteristic that endotoxin has a hydrophobic portion in its molecule and is easily adsorbed to hydrophobic materials. Is disclosed. (For example, refer to Patent Document 2). That is, it can be achieved by setting the ratio of the hydrophilic polymer to the hydrophobic polymer on the outer surface of the hollow fiber membrane to 5 to 25% by mass. Certainly, this method is a preferable method for suppressing the invasion of endotoxin into the blood side, but to impart this property, it is necessary to remove the hydrophilic polymer present on the outer surface of the membrane by washing. There is a problem that this cleaning requires a great deal of processing time and is economically disadvantageous. For example, in the embodiment of the above-mentioned patent, shower cleaning with hot water at 60 ° C. and cleaning with hot water at 110 ° C. are performed for 1 hour each.
JP 2000-254222 A

In addition, it is preferable to reduce the hydrophilic high molecular weight present on the outer surface of the membrane from the viewpoint of suppressing the invasion of endotoxin into the blood side. Therefore, when the dried hollow fiber membrane bundle is returned to a wet state, the familiarity with the physiological saline used for wetting becomes low. This is not preferable because it leads to the problem. As a method for improving this point, for example, a method of blending a hydrophilic compound such as glycerin is disclosed. (For example, refer to Patent Documents 3 and 4). However, if the method deviates from the proper concentration range, the hydrophilic compound acts as a foreign substance during dialysis, and the hydrophilic compound is susceptible to deterioration such as photodegradation, which adversely affects the storage stability of the module. Has the problem. In addition, there is also a problem of causing adhesive inhibition of the adhesive when the hollow fiber membrane bundle is fixed to the module in module assembly.
JP-A-2001-190934 Japanese Patent No. 3193262

As a method for avoiding the sticking of the hollow fiber membranes, which is another problem described above, a method in which the porosity of the outer surface of the membrane is 25% or more is disclosed. (For example, refer to Patent Document 5). Certainly, this method is a preferable method for avoiding sticking, but has a problem that the membrane strength becomes low due to the high porosity and leads to the above-mentioned problem of blood leakage. Also disclosed is a method in which the porosity and area of the outer surface of the membrane are specified. (For example, refer to Patent Document 6). This method has a problem of low water permeability.
JP 2001-38170 A JP 2000-140589 A

Patent Document 7 discloses a technical requirement that, in a hydrophobic polymer hollow fiber membrane containing a hydrophilic polymer, elution of the hydrophilic polymer from the hollow fiber membrane is 10 ppm or less. However, in the prior art, no consideration is given to hemodiafiltration that requires higher pressure resistance and endotoxin exclusion compared to conventional hemodialysis. For example, there is no description regarding technical matters related to the abundance ratio, burst pressure, open area ratio, average pore area of outer surface polyvinylidylpyrrolidone, and in particular, technical matters related to important uneven thickness and burst pressure due to scratches There is no description.
JP 2001-170171 A

There is no doubt that endotoxin permeation into the blood and elution of hydrophilic polymers into the blood will affect safety, but it cannot be asserted that sufficient safety can be ensured only by paying attention to these. In fact, there are still reports of anaphylactoid shock cases even in dialysis membranes that are said to suppress the elution of polyvinylpyrrolidone (see, for example, Non-Patent Document 1).
Nakayama et al., 0-439 43rd Annual Meeting of Japanese Society for Dialysis Therapy, p620, 1998

For the dialysis membrane eluate, (1) Appearance, (2) Awadachi, (3) pH, (4) Zinc, (5) Copper, (6) UV spectrum standards are shown (for example, non- The elution of polyvinylpyrrolidone can be detected by UV absorption. However, when we measured a commercially available polyvinyl pyrrolidone-containing polysulfone dialysis membrane, the UV value of the eluate is in the vicinity of the reference value and does not reflect problems such as a decrease in blood pressure and shock symptoms in the clinic. Further, the amount of polyvinylpyrrolidone eluted in the fraction obtained by washing the blood flow path with physiological saline was as low as several mg. In other words, when the amount of elution with water (saline) is used as an index, the biocompatibility of the polysulfone-based dialysis membrane containing polyvinylpyrrolidone at present may not be sufficiently confirmed, and extraction to the same extent as blood or blood is possible. It is thought that it is necessary to obtain an eluate from the extracorporeal circuit with a powerful force and to make a judgment with a new index for confirming the presence or absence of the influence on the living body.
Dialysis-type artificial kidney device approval criteria (June 20, 1983, Yakuhatsu No.494)

  As a result of examining the safety from the above viewpoint, the inventors have found a method for judging the influence on a living body by dissolving a residue obtained by concentrating and lyophilizing an extract in a physiological saline for injection and administering it to a dog. As a result of confirmation by this method, it was clarified that the cyclic dimer in the membrane had a certain amount or less and the safety was high, and the present invention was reached.

Although the detailed mechanism is unknown, the following two points are considered as causes.
1. The cyclic dimer elutes, which directly causes a reduction in safety.
2. When the content of the cyclic dimer is large, it is presumed that the cyclic dimers are unstable in the solvent and thus aggregate and insolubilize each other. The presence of the insolubilized aggregate in the membrane and / or on the membrane surface affects the elution from the membrane such as a hydrophilic polymer, leading to a reduction in safety.

  An object of the present invention is to provide a medical hollow fiber blood purifier having excellent water permeability and used for the treatment of chronic renal failure, which is excellent in safety, module assembly, and blood compatibility.

The present invention relates to a hollow fiber membrane composed of a polysulfone-based polymer containing a hydrophilic polymer, and has a thickness of 10 to 50 μm, an outer surface porosity of 8 to 25%, a thickness deviation of 0.6 or more, and The ratio of the hydrophilic polymer present on the surface is 25 to 50% by mass, the elution of the hydrophilic polymer from the hollow fiber membrane is 10 ppm or less, and the burst pressure of the hollow fiber membrane is 0.5 to 2%. A blood purifier housing a hollow fiber membrane having a content of a soluble cyclic dimer with respect to the polysulfone-based polymer of 1.0 MPa or less, having a water permeability of 150 ml / m ² / hr / mmHg or more A high-performance hollow fiber membrane blood purifier characterized by

  The hollow fiber blood purifier of the present invention is excellent in safety and module assemblability, and further has a blood retention and performance maintenance when using blood contact because the platelet retention rate during blood perfusion is within a predetermined range. Therefore, it is suitable as a medical hollow fiber blood purifier having high water permeability for use in the treatment of chronic renal failure such as hemodialysis, hemofiltration and hemodiafiltration.

The hollow fiber membrane used in the present invention is characterized in that it is composed of a hydrophobic polymer containing a hydrophilic polymer. Examples of the hydrophobic polymer material in the present invention include cellulose-based materials such as regenerated cellulose, cellulose acetate, and cellulose triacetate, polysulfone-based materials such as polysulfone and polyethersulfone, polyacrylonitrile, polymethyl methacrylate, and ethylene vinyl alcohol copolymer. However, it is preferable to use a cellulose or polysulfone type which can easily obtain a hollow fiber having a water permeability of 150 mL / m ² / hr / mmHg or more. Polyether sulfone is particularly preferable for cellulose triacetate and polysulfone.

  The hydrophilic polymer used in the present invention is not particularly limited, and those that form a micro phase separation structure in a solution with a hydrophobic polymer are preferably used. Polyethylene glycol, polyvinyl alcohol, carboxymethyl cellulose, polyvinyl pyrrolidone and the like can be mentioned, but it is a preferred embodiment that polyvinyl pyrrolidone is used from the viewpoint of safety and economy.

  In the present invention, the composition ratio of the hydrophilic polymer to the hydrophobic polymer in the membrane may be in a range that can provide sufficient hydrophilicity and high water content to the hollow fiber membrane, and the hydrophobic polymer 80 to 99 mass. The mass ratio of the hydrophilic polymer to% is preferably 1 to 20% by mass. When the mass ratio of the hydrophilic polymer to the hydrophobic polymer is too small, the effect of imparting hydrophilicity to the film may be insufficient. Therefore, the mass ratio is more preferably 2% by mass or more. On the other hand, when the mass ratio is too large, the effect of imparting hydrophilicity is saturated, and the amount of elution from the membrane of the hydrophilic polymer increases, and the amount of elution from the membrane of the hydrophilic polymer described later exceeds 10 ppm. There is. Therefore, it is more preferably 18% by mass or less, further preferably 15% by mass or less, still more preferably 12% by mass or less, and particularly preferably 9% by mass or less.

  In the present invention, the elution amount of the hydrophilic polymer from the hollow fiber membrane is preferably 10 ppm or less. When the elution amount exceeds 10 ppm, side effects and complications due to long-term dialysis due to the eluted hydrophilic polymer may occur. A method for satisfying the characteristics is optional without limitation, and can be achieved, for example, by setting the composition ratio of the hydrophilic polymer to the hydrophobic polymer within the above range or optimizing the film forming conditions of the hollow fiber membrane. . More preferably, the elution amount of the hydrophilic polymer is 8 ppm or less, more preferably 6 ppm or less, and still more preferably 4 ppm or less. In addition, the amount of elution of the hydrophilic polymer is preferably zero from the viewpoint of safety to the living body. However, when the amount of elution of the hydrophilic polymer is made zero, the degree of hydrophilicity of the blood contact surface decreases, and blood Since the compatibility may be lowered, the elution amount of the hydrophilic polymer seems to be within an allowable range of about 0.1 ppm.

  In the present invention, the content of the soluble cyclic dimer with respect to the polymer is preferably 1.0% by weight or less. Insoluble aggregates are practically not observed on the membrane surface, and there is no possibility that the antithrombogenicity is lowered because hydrophobic portions are not scattered.

  Furthermore, it is a preferred embodiment that the hydrophilic polymer is insolubilized by crosslinking. There is no limitation on the crosslinking method, the degree of crosslinking, etc. For example, the crosslinking method includes γ-rays, electron beams, heat, chemical crosslinking, etc. Among them, residues such as initiators do not remain, and in terms of high material permeability, γ-rays and electron beams are used. Crosslinking is preferred. In the present invention, it is preferable that the module is liquid-tightly filled with degassed water, sealed, and irradiated with γ rays of 10 kGy to 60 kGy. If the amount of γ-ray irradiation is too small, crosslinking may be insufficient and the amount of eluate may increase. If the amount of γ-ray irradiation is too large, the hydrophobic polymer, hydrophilic polymer, housing case, and urethane resin may be decomposed and deteriorated, so 50 kGy or less is more preferable. More preferably, it is 40 kGy or less, and still more preferably 30 kGy or less. Here, the degassed water means water that has been heated to room temperature to 50 ° C. and stirred for 15 minutes to 2 hours under a reduced pressure of −500 to −760 mmHg. When water that has not been degassed is used, the membrane constituent material may be oxidized and deteriorated due to dissolved oxygen in the water, resulting in an increase in eluate.

  Insolubilization in the present invention refers to solubility when the crosslinked film is immersed in dimethylformamide. That is, 1.0 g of the crosslinked film is taken, dissolved in 100 ml of dimethylformamide, and the presence or absence of insoluble matter is visually observed and determined. In the case of a module in which a liquid is filled in the module, the filling liquid is first withdrawn, and then pure water is allowed to flow at 500 mL / min for 5 minutes in the dialysate side flow path, and then pure water is similarly applied to the blood side flow path. Flow for 5 minutes at 200 mL / min. Finally, 200 mL / min of pure water is passed through the membrane from the blood side to the dialysate side to finish the washing process. The hollow fiber membrane is taken out from the obtained module and freeze-dried to make a sample for measuring unnecessary components. In the case of a dry hollow fiber membrane module, the same washing treatment is performed to obtain a measurement sample.

  In the present invention, the abundance ratio of the above-described hydrophilic polymer on the outer surface of the hollow fiber membrane is preferably 25 to 50% by mass. If the proportion of the hydrophilic polymer on the outer surface is less than 25% by mass, the proportion of the hydrophilic polymer on the entire membrane, particularly the inner surface of the membrane, becomes too low, and blood compatibility and permeation performance may be degraded. . In the case of a dry film, the priming property may be lowered. When the hemodialyzer is used for blood purification therapy, it is necessary to perform wetting and defoaming by allowing physiological saline or the like to flow inside and outside the hollow fiber membrane of the hemodialyzer. In this priming operation, roundness of the hollow fiber membrane, edge crushing, deformation, hydrophilicity of the membrane material, etc. are thought to affect the priming properties, but it consists of a hydrophobic polymer and a hydrophilic polymer. In the case of a hollow fiber membrane and a dry membrane module, the hydrophilic / hydrophobic balance of the hollow fiber membrane greatly affects the priming property. Therefore, the more preferable proportion of the hydrophilic polymer is 27% by mass or more, and more preferably 30% by mass or more. If the proportion of the hydrophilic polymer on the outer surface exceeds 50% by mass, the endotoxin (endotoxin) contained in the dialysate is likely to enter the blood side, leading to side effects such as fever, When the membrane is dried, a hydrophilic polymer existing on the outer surface of the membrane is interposed, and the hollow fiber membranes stick to each other (adhere), which may cause problems such as deterioration in module assembly. Therefore, a more preferable existence ratio is 47 mass% or less, More preferably, it is 45 mass% or less.

  Examples of the method of setting the ratio of the hydrophilic polymer existing on the outer surface of the hollow fiber membrane within the above-described range include, for example, setting the ratio of the hydrophilic polymer to the hydrophobic polymer within the above-described range, or forming the hollow fiber membrane. This can be achieved by optimizing the conditions. It is also an effective method to wash the formed hollow fiber membrane. As film forming conditions, humidity adjustment of the air gap part at the nozzle outlet, stretching conditions, temperature of the coagulation bath, optimization of the composition ratio of the solvent and the non-solvent in the coagulation liquid, etc. Washing, alcohol washing, centrifugal washing and the like are effective.

  The air gap portion is preferably surrounded by a member for blocking outside air, and the humidity inside the air gap is preferably adjusted by the composition of the spinning dope, the nozzle temperature, the air gap length, the temperature of the external coagulation bath, and the composition. For example, a spinning stock solution consisting of polyethersulfone / polyvinylpyrrolidone / dimethylacetamide / water = 10-25 / 0.5-12.5 / 52.5-89.5 / 0-10.0 is used at a nozzle of 30-60 ° C. When the air gap is discharged through the air gap of 100 to 1000 mm and led to an external coagulation bath having a concentration of 0 to 70 mass% and a temperature of 50 to 80 ° C., the absolute humidity of the air gap portion is 0.01 to 0.3 kg / kg. It becomes dry air. By adjusting the humidity of the air gap part to such a range, it becomes possible to control the outer surface open area ratio, the outer surface average pore area, and the outer surface hydrophilic polymer content to an appropriate range.

  As the internal coagulation liquid, a 0 to 80% by mass dimethylacetamide (DMAc) aqueous solution is preferable. If the concentration of the internal coagulation solution is too low, the dense layer on the blood contact surface becomes thick, which may reduce the solute permeability. A more preferable internal coagulation liquid concentration is 15% by mass or more, further preferably 25% by mass or more, and still more preferably 30% by mass or more. On the other hand, if the concentration of the internal coagulating liquid is too high, the formation of the dense layer tends to be incomplete, and the fractionation characteristics may deteriorate. The concentration of the internal coagulation liquid is more preferably 70% by mass or less, further preferably 60% by mass or less, and still more preferably 50% by mass or less.

  As the external coagulation liquid, it is preferable to use a DMAc aqueous solution of 0 to 50% by mass. If the concentration of the external coagulation solution is too high, the outer surface open area ratio and outer surface average pore area will become too large, which may increase the backflow of endotoxin to the blood side during dialysis and decrease the burst pressure. is there. Therefore, the external coagulation liquid concentration is more preferably 40% by mass or less, further preferably 30% by mass or less, and still more preferably 25% by mass or less. If the concentration of the external coagulation liquid is too low, it is necessary to use a large amount of water to dilute the solvent brought in from the spinning stock solution, and the cost for waste liquid treatment increases. Therefore, the lower limit of the external coagulation liquid concentration is more preferably 3% by mass or more, and further preferably 5% by mass or more.

  In the production of the hollow fiber membrane of the present invention, it is preferable that stretching is not substantially applied before the hollow fiber membrane structure is completely fixed. “Substantially no stretching” means that the roller speed during the spinning process is controlled so that the spinning dope discharged from the nozzle is not loosened or excessively tensioned. The discharge linear speed / coagulation bath first roller speed ratio (draft ratio) is preferably in the range of 0.7 to 1.8. If the ratio is less than 0.7, the running hollow fiber membrane may be loosened, leading to a decrease in productivity. Therefore, the draft ratio is more preferably 0.8 or more, further preferably 0.9 or more, and More preferably 95 or more. If it exceeds 1.8, the membrane structure may be destroyed, for example, the dense layer of the hollow fiber membrane is torn. Therefore, the draft ratio is more preferably 1.7 or less, still more preferably 1.6 or less, still more preferably 1.5 or less, and particularly preferably 1.4 or less. By adjusting the draft ratio to this range, deformation and destruction of the pores can be prevented, clogging of blood protein into the membrane pores can be prevented, and performance stability over time and sharp fractionation characteristics can be expressed. Is possible.

The hollow fiber membrane that has passed through the water-washing bath is wound into a basket in a wet state to form a bundle of 3,000 to 20,000. Next, the obtained hollow fiber membrane bundle is washed to remove excess solvent and hydrophilic polymer. As a method for cleaning the hollow fiber membrane bundle, in the present invention, it is preferable to treat the hollow fiber membrane bundle by immersing it in hot water at 70 to 130 ° C., or from room temperature to 50 ° C. and 10 to 40 vol% ethanol or isopropanol aqueous solution. .
(1) In the case of hot water washing, the hollow fiber membrane bundle is immersed in excess water and treated at 70 to 90 ° C. for 15 to 60 minutes, and then the hollow fiber membrane bundle is taken out and subjected to centrifugal dehydration. This operation is repeated three or four times while renewing the water to perform the cleaning process.
(2) A method of treating a hollow fiber membrane bundle immersed in excess water in a pressurized container at 121 ° C. for about 2 hours can also be employed.
(3) When using an ethanol or isopropanol aqueous solution, it is preferable to repeat the same operation as in (1).
(4) It is also preferable that the hollow fiber membrane bundles are arranged radially in the centrifugal washer, and the centrifugal washing is performed for 30 minutes to 5 hours as a total time while spraying washing water at 40 ° C. to 90 ° C. from the rotation center in a shower shape. Is the method.
Two or more cleaning methods may be combined. In any of the methods, if the processing temperature is too low, it is necessary to increase the number of times of cleaning, which may lead to an increase in cost. On the other hand, when the treatment temperature is too high, the decomposition of the hydrophilic polymer is accelerated, and conversely, the cleaning efficiency may be lowered. By performing the above-described washing, it is possible to optimize the abundance of the hydrophilic polymer on the outer surface, and to suppress sticking and reduce the amount of eluate.

  In addition, the abundance ratio of the hydrophilic polymer surface outermost layer described above was measured and calculated by the ESCA method as described later, and the outermost layer portion (depth number from the surface layer) of the hollow fiber membrane surface was calculated. The absolute value of the existence ratio of ˜several tens of meters) is obtained. In the present invention, the hydrophilic polymer (PVP) content up to about 10 nm (100 mm) from the outer surface of the hollow fiber membrane by the ESCA method (outermost layer) is the hydrophilic polymer of the outermost layer of the outer surface of the hollow membrane. The existence ratio was used.

Another feature of the present invention is a blood purifier comprising a hollow fiber membrane having a burst pressure of 0.5 MPa or less, and the permeability of pure water of the blood purifier is 150 ml / m ² / hr / mmHg. is required. When the burst pressure is less than 0.5 MPa, it becomes impossible to detect a potential defect that leads to blood leak as described later. Further, when the pure water filtration coefficient is less than 150 ml / m ² / hr / mmHg, a high removal efficiency cannot be obtained. In order to increase the removal efficiency, the pore diameter is increased or the number of pores is increased. However, this tends to cause a problem that the film strength is reduced or defects are formed. However, in the hollow fiber membrane of the present invention, the porosity of the support layer portion is optimized by optimizing the pore diameter of the outer surface, and the solute permeation resistance and membrane strength are balanced. A more preferable range of water permeability is 200 ml / m ² / hr / mmHg or more, more preferably 300 ml / m ² / hr / mmHg or more, particularly preferably 400 ml / m ² / hr / mmHg or more, most preferably 500 ml / m ^2. / Hr / mmHg or more. Moreover, when the water permeability is too high, it becomes difficult to control the water removal during hemodialysis. For this reason, 2000 ml / m < ² > / hr / mmHg or less is preferable. More preferably 1800 ml / m ² / hr / mmHg or less, further preferably 1500 ml / m ² / hr / mmHg or less, even more preferably 1300 ml / m ² / hr / mmHg or less, particularly preferably 1000 ml / m ² / hr / h / g. It is below mmHg.

  The present inventors examined the physical properties of hollow fiber membranes used in blood purifiers. Usually, a module used for blood purification is subjected to a leak test in which the inside or outside of the hollow fiber is pressurized with air in order to confirm defects of the hollow fiber or the module at the final stage of production. When a leak is detected by the pressurized air, the module is discarded as a defective product or is repaired. The air pressure in this leak test is often 1500 to 2000 mmHg (0.2 to 0.27 MPa), which is several times the guaranteed pressure resistance of the hemodialyzer (usually 500 mmHg). However, in the case of a hollow fiber type blood purification membrane having a particularly high water permeability, microscopic scratches, crushing, and tearing of the hollow fiber that cannot be detected by a normal pressure leak test are caused by manufacturing processes (mainly sterilization and When packaging (packing), transportation process, or clinical treatment (unpacking, priming, etc.), it leads to hollow fiber breakage and pinholes, which causes problems such as blood leaking during treatment. The present inventors have found that. As a result of intensive studies on the above events, potential yarn defects that lead to hollow fiber breakage and pinholes during clinical use cannot be detected with the pressure in the normal pressurized air leak test. It has been found that suppressing the occurrence of uneven thickness of the hollow fiber membrane is effective for suppressing the occurrence of the above-described potential defects, and has led to the present invention.

  The burst pressure in the present invention is an index of the pressure resistance performance of the hollow fiber membrane after the hollow fiber is made into a module. The inside of the hollow fiber membrane is pressurized with gas, and the pressure is gradually increased. This is the pressure when bursting without being able to withstand the pressure. The higher the burst pressure, the less the hollow fiber membrane is cut and the occurrence of pinholes during use, so 0.5 MPa or more is preferred, 0.55 MPa or more is more preferred, and 0.6 MPa or more is even more preferred. If the burst pressure is less than 0.5 MPa, there may be a potential defect. The higher the burst pressure, the better. However, if the focus is on increasing the burst pressure and the film thickness is increased or the porosity is decreased too much, the desired film performance may not be obtained. Therefore, when finished as a hemodialysis membrane, the burst pressure is preferably less than 2.0 MPa. More preferably, it is less than 1.7 MPa, more preferably less than 1.5 MPa, even more preferably less than 1.3 MPa, and particularly preferably less than 1.0 MPa.

  The present invention has been found on the basis of the knowledge that the safety of hollow fiber membranes in dialysis treatment cannot be sufficiently proved by blood leak characteristics governed by macro characteristics such as conventionally known membrane strength. In other words, in order to ensure the safety of blood leaks in dialysis procedures where high filtration pressure is generated, in addition to the macro characteristics, the establishment of evaluation including defects due to potential defects as described above has been studied. The invention has been completed.

  The present invention has been found on the basis of the knowledge that the safety of hollow fiber membranes in long-term dialysis cannot be sufficiently proved by blood leak characteristics governed by macro characteristics such as conventionally known membrane strength. In other words, in order to ensure the safety of blood leaks in long-term dialysis, the present invention was completed by earnestly studying the establishment of evaluation including defects due to potential defects as described above in addition to macro characteristics. is there.

  The thickness deviation in the present invention is a thickness deviation when observing 100 cross sections of hollow fiber membrane modules in the hollow fiber membrane module, and is expressed as a ratio between the maximum value and the minimum value. In the present invention, the minimum thickness deviation of 100 hollow fibers is 0.6 or more. If even one hollow fiber includes a hollow fiber with a thickness deviation of less than 0.6, the hollow fiber may cause a leak during clinical use. Instead, it represents the minimum value of 100 lines. Higher unevenness increases the uniformity of the film, suppresses the appearance of latent defects, and improves the burst pressure. Therefore, it is more preferably 0.7 or more, more preferably 0.8 or more, and still more preferably 0. .85 or more. If the uneven thickness is too low, latent defects are likely to be manifested, the burst pressure is lowered, and blood leakage is liable to occur.

  The film thickness of the hollow fiber membrane is preferably 10 μm or more and 60 μm or less. If it exceeds 60 μm, the permeability of medium to high molecular weight substances having a low movement speed may be lowered even if the water permeability is high. The thinner the film thickness is, the higher the material permeability is, and it is more preferably 55 μm or less, further preferably 50 μm or less, and still more preferably 45 μm or less. On the other hand, when the film thickness is less than 10 μm, the burst pressure may be lowered even if the film strength is low and the thickness deviation is 0.6 or more. Therefore, the film thickness is more preferably 20 μm or more, further preferably 25 μm or more, still more preferably 30 μm or more, and particularly preferably 35 μm or more.

  The present invention can be suitably used for a blood purification hollow fiber membrane, and is particularly suitable as a hollow fiber membrane blood purification device used for the treatment of patients with renal failure, such as hemodialysis, hemodiafiltration and blood filtration.

  As an index indicating blood compatibility, there is a method for evaluating adhesion of platelets when contacted with blood. Conventionally, in order to improve blood compatibility, studies have been made with the goal of reducing the amount of platelet adhesion (improving platelet retention). Activation is considered unavoidable in some sense, even if the degree of difference. In the case of a membrane with a very high platelet retention rate, the apparent blood compatibility is judged to be good, but if the view is changed, even the platelets activated by contact with foreign materials are in the blood. May have been released. From such a viewpoint, as a result of further intensive studies, it was found that the retention rate of platelets is actually preferably 70% to 98%, and the present invention has been achieved. A more preferable range of the platelet retention is 75% to 98%, and a more preferable range is 80% to 98%. If the platelet retention rate is less than this range, the amount of platelet adhesion increases, and blood clots may be easily formed or the blood purification function may be reduced. In addition, if it is larger than this range, even activated platelets are released into the blood, so blood components such as blood cells and plasma circulating in the living body are stimulated, and the whole blood in the living body is activated Therefore, there is no denying the tendency to clot and in some cases the risk of embolization.

  Increasing the hydrophilic polymer concentration on the inner surface of the membrane is one means for improving blood compatibility. However, if the surface concentration becomes too high, the amount of the hydrophilic polymer eluted into the blood increases, and the blood The risk of platelet aggregation, blood clots, and in some cases embolization is also undeniable. Therefore, in order to realize better blood compatibility, it is necessary that the platelet retention rate during blood perfusion is within a predetermined range. Due to these characteristics, blood compatibility and performance retention when using blood contact are required. , Safety is realized at a high level.

  The present invention can be suitably used for a hollow fiber membrane for blood purification, and is particularly suitable as a hollow fiber membrane used for the treatment of patients with renal failure, such as hemodialysis, hemodiafiltration and blood filtration.

  As a method for producing a hollow fiber membrane used in such a blood purifier, a solution of a hydrophobic polymer having a composition described above and a hydrophilic polymer dissolved in a solvent that dissolves the formulation is used. Manufactured by dry and wet methods. In order to set the burst pressure to 0.5 MPa or more, it is effective and preferable to make the thickness of the hollow fiber membrane 0.6 or more as described above. As an achievement means for making the unevenness degree 0.6 or more, for example, it is preferable to make the slit width of the nozzle that is the discharge port of the film forming solution strictly uniform. The spinning nozzle of the hollow fiber membrane is generally a tube-in-orifice type nozzle having an annular portion for discharging the spinning stock solution and a core liquid discharge hole serving as a hollow forming agent inside thereof. It refers to the width of the outer annular portion that discharges the spinning dope. By reducing the variation in the slit width, uneven thickness of the spun hollow fiber membrane can be reduced. Specifically, the ratio between the maximum value and the minimum value of the slit width is 1.00 or more and 1.11 or less, and the difference between the maximum value and the minimum value is preferably 10 μm or less, more preferably 7 μm or less, More preferably, it is 5 micrometers or less, More preferably, it is 3 micrometers or less. Also, the nozzle temperature is optimized. The nozzle temperature is preferably 20 to 100 ° C. If it is less than 20 ° C., it is easily affected by the room temperature, the nozzle temperature is not stable, and the discharge stock of the spinning stock solution may occur. Therefore, the nozzle temperature is more preferably 30 ° C. or higher, further preferably 35 ° C. or higher, and further preferably 40 ° C. or higher. On the other hand, when the nozzle temperature exceeds 100 ° C., the viscosity of the spinning dope may be too low and ejection may become unstable, and thermal degradation and decomposition of the hydrophilic polymer may proceed. Therefore, the nozzle temperature is more preferably 90 ° C. or less, further preferably 80 ° C. or less, and still more preferably 70 ° C. or less.

  Further, as a measure for increasing the burst pressure, it is also an effective method to reduce the potential defects by reducing the flaws on the surface of the hollow fiber membrane, the mixing of foreign matter and bubbles. As a method of reducing the occurrence of scratches, the material and surface roughness of rollers and guides in the manufacturing process of the hollow fiber membrane are optimized, the container and the hollow fiber membrane are inserted when the hollow fiber membrane bundle is inserted into the module container at the time of module assembly. It is effective to devise such that contact with the fiber or rubbing between the hollow fiber membranes is reduced. In the present invention, it is preferable to use a roller having a mirror-finished surface in order to prevent the hollow fiber membrane from slipping and scratching the surface of the hollow fiber membrane. Further, it is preferable to use a guide whose surface is textured or knurled in order to avoid contact resistance with the hollow fiber membrane as much as possible. When the hollow fiber membrane bundle is inserted into the module container, the hollow fiber membrane bundle is not directly inserted into the module container, but a film whose contact surface with the hollow fiber membrane is processed with a satin finish, for example, is wound around the hollow fiber membrane bundle. It is preferable to use a method in which only the film is removed from the module container after being inserted into the module container.

  As a method for suppressing the mixing of foreign matter into the hollow fiber membrane, a method using a raw material with less foreign matter, filtering the spinning dope for forming a membrane, and reducing foreign matter is effective. In the present invention, it is preferable to filter the spinning dope using a filter having a pore size smaller than the film thickness of the hollow fiber membrane. Specifically, the pore size provided while the uniformly dissolved spinning dope is led from the dissolution tank to the nozzle. Pass through a 10-50 μm sintered filter. 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 size 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, and still more preferably 10 to 35 μm. If the filter pore size is too small, the back pressure may increase and the quantitativeness may decrease. Further, as a method for suppressing the mixing of bubbles, it is effective to defoam a polymer solution for film formation. Depending on the viscosity of the spinning dope, static defoaming or vacuum defoaming can be used. Specifically, after the pressure in the dissolution tank is reduced to -100 to -760 mmHg, the tank is sealed and allowed to stand for 5 to 30 minutes. This operation is repeated several times to perform defoaming treatment. 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. On the other hand, when the degree of vacuum is too high, the cost for increasing the degree of sealing of the system may increase. The total treatment time is preferably 5 minutes to 5 hours. If the treatment time is too long, the hydrophilic polymer 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.

In the present invention, the hole area ratio of the outer surface of the hollow fiber membrane is 8 to 25%, and the average hole area of the hole portion on the outer surface of the hollow fiber membrane is 0.3 to 1.0 μm ² . This is effective for imparting the above-mentioned characteristics and is a preferred embodiment. If the open area ratio is less than 8% or the average pore area is less than 0.3 μm ² , the water permeability may decrease. Therefore, the open area ratio is more preferably 9% or more, and further preferably 10% or more. The average pore area is more preferably 0.4 μm ² or more, further preferably 0.5 μm ² or more, and further preferably 0.6 μm ² or more. Further, when the membrane is dried, the hydrophilic polymer existing on the outer surface of the membrane is interposed, and the hollow fiber membranes are fixed to each other, causing problems such as deterioration in module assemblability. On the contrary, when the open area ratio exceeds 25% or the average pore area exceeds 1.0 μm ² , the burst pressure may decrease. Therefore, the porosity is more preferably 23% or less, further preferably 20% or less, still more preferably 17% or less, and particularly preferably 15% or less. The average pore area is more preferably 0.95 .mu.m ² or less, more preferably 0.90 .mu.m ² or less.

  As a specific means for controlling the mass ratio of the hydrophilic polymer to the hydrophobic polymer in the membrane within the above range, for example, the composition ratio of the hydrophobic polymer to the hydrophilic polymer in the spinning dope is set to 95: 5-67. : 33, adjusting the condition of the external coagulation liquid to 5 to 40% by mass, or performing hot water washing or alcohol washing after film formation.

  As a method for obtaining a polysulfone polymer having a low content of soluble cyclic dimer, specifically, it is preferable to purify a commercially available polysulfone polymer and then use it for film formation. After dissolving in a good solvent, there is a method of recovering the polysulfone polymer by reprecipitation in a solvent which is a poor solvent and dissolves the soluble cyclic dimer. In addition, after dissolving polysulfone polymer in a good solvent, about 1-5% of water is added to forcibly generate insoluble aggregates, which are separated by filtration or centrifugation, and preparative chromatography A method of fractionating a fraction not containing a soluble cyclic dimer is also conceivable. Either method can be collected.

  In the present invention, optimization of the abundance of the above-described hydrophilic polymer on the outer surface of the hollow fiber membrane and optimization of the burst pressure are conducted as a separate technique to solve the above-mentioned problems. However, the inventors have found that the following unexpected synergistic effects can be obtained by simultaneously executing both technologies that seem to be surprisingly irrelevant. Although potential membrane defects that were not considered a problem in the past may become apparent with this therapy, it is possible to detect membrane defects in advance by setting the burst pressure to a certain value or more, which is sufficient as a product. It was found that safety that can be used for therapy can be secured. In addition, it has been pointed out that there is a risk of serious symptoms such as anaphylaxis when an eluate derived from a membrane material in dialysate by reverse filtration or endotoxin contained in the dialysate is mixed in blood. The hollow fiber membrane of the present invention has a high water permeability (that is, a large membrane pore diameter) by making the hydrophilic high molecular weight of the outer surface within a specific range and making the membrane surface porosity and pore area into a specific range. A hollow fiber membrane (having a high porosity) also achieves a high level of both solute removability and safety for preventing foreign matter from entering the blood without causing leakage.

  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 method of the physical property in the following examples is as follows.

1. Measurement of filtration coefficient of pure water The blood outlet circuit of the dialyzer (the outlet side from the pressure measurement point) was sealed with forceps. Purified water kept at 37 ° C is placed in a pressurized tank, and the pressure is controlled by a regulator. The pure water is sent to a dialyzer kept warm in a 37 ° C high-temperature tank, and the mass of the filtrate flowing out from the dialysate side is 1 / 100g. Measure up to. The transmembrane pressure difference (TMP) is
TMP = (Pi + Po) / 2
And Here, Pi is the dialyzer inlet side pressure, and Po is the dialyzer outlet side pressure. Change the TMP at four points, measure the filtration flow rate, and calculate the water permeability (mL / hr / mmHg) from the slope of the relationship. At this time, the correlation coefficient between TMP and filtration flow rate should be 0.999 or more. In order to reduce the pressure loss error due to the circuit, TMP is measured in the range of 100mmHg or less. The water permeability of the hollow fiber membrane is calculated from the membrane area and the water permeability of the dialyzer.
UFR (H) = UFR (D) / A
Where UFR (H) is the water permeability of the hollow fiber membrane (mL / m ² / hr / mmHg), UFR (D) is the water permeability of the dialyzer (mL / hr / mmHg), and A is the membrane area of the dialyzer ( m ² ).

2. Calculation of membrane area The membrane area of the dialyzer was determined based on the inner diameter of the hollow fiber.
A = n × π × d × L
Here, n is the number of hollow fibers in the dialyzer, π is the circumference, d is the inner diameter (m) of the hollow fiber, and L is the effective length (m) of the hollow fiber in the dialyzer.

3. Burst pressure Fill the dialysate side of the module consisting of about 10,000 hollow fiber membranes with water and plug it. Supply dry air or nitrogen from the blood side at room temperature and pressurize at a rate of 0.5 MPa per minute. The pressure was increased, and the air pressure when the hollow fiber membrane burst (burst) with pressurized air and bubbles were generated in the liquid filled on the dialysate side was defined as the burst pressure.

4). Unevenness of wall Observe the cross section of 100 hollow fibers with a 200x projector. In one field of view, the thickness of the thickest part and the thinnest part was measured for one yarn cross section with the largest film thickness difference.
Thickness unevenness = thinnest part / thickest part thickening degree = 1, and the film thickness is perfectly uniform.

5). Elution amount of hydrophilic polymer An example of the measurement method when polyvinylpyrrolidone is used as the hydrophilic polymer is shown below.
Extraction was performed by the method defined in the dialysis artificial kidney device production standard, and polyvinylpyrrolidone in the extract was quantified by a colorimetric method.
That is, 100 ml of pure water was added to 1 g of the hollow fiber membrane and extracted at 70 ° C. for 1 hour. To 2.5 ml of the resulting extract, 0.25 ml of a 0.2 molar citric acid aqueous solution and 0.5 ml of 0.006 N iodine aqueous solution were added and mixed well, and after standing at room temperature for 10 minutes, the absorbance at 470 nm was measured. . Quantification was performed with a calibration curve obtained according to the above method using a standard polyvinylpyrrolidone.
In the case of the wet hollow fiber membrane module, physiological saline was passed through the dialysate side channel of the module at 500 mL / min for 5 minutes, and then passed through the blood side channel at 200 mL / min. Thereafter, the solution was allowed to pass through for 3 minutes while filtering from the blood side to the dialysate side at 200 mL / min, and then freeze-dried to obtain a dry membrane, and the above-described quantification was performed using the dry membrane.

6). Abundance ratio of hydrophilic polymer on outer surface The abundance ratio of hydrophilic polymer to hydrophobic polymer was determined by X-ray photoelectron spectroscopy (ESCA method). A measurement method in the case of using polysulfone-based polymer as the hydrophobic polymer and polyvinylpyrrolidone as the hydrophilic polymer is exemplified.
One hollow fiber membrane was attached to a sample stage, and measurement was performed by X-ray photoelectron spectroscopy (ESCA method). The measurement conditions are as follows.
Measuring device: ULVAC-Phi ESCA5800
Excitation X-ray: MgKα ray X-ray output: 14 kV, 25 mA
Photoelectron escape angle: 45 °
Analysis diameter: 400μmφ
Pass energy: 29.35 eV
Resolution: 0.125 eV / step
Degree of vacuum: about 10 ⁻⁷ Pa or less From the measured value (N) of nitrogen and the measured value (S) of sulfur, the PVP content ratio on the surface was calculated by the following formula.
<In case of PVP-added PES (polyethersulfone) membrane>
PVP content ratio (Hpvp) [%]
= 100 × (N × 111) / (N × 111 + S × 232)
<In the case of PVP-added PSf (polysulfone) membrane>
PVP content ratio (Hpvp) [%]
= 100 × (N × 111) / (N × 111 + S × 442)

7). The mass ratio of the hydrophilic polymer in a film | membrane The measuring method at the time of using PVP as a hydrophilic polymer is illustrated. The sample was dried at 80 ° C. for 48 hours using a vacuum dryer, and 10 mg of the sample was analyzed with a CHN coder (manufactured by Yanaco Analytical Industrial Co., Ltd., MT-6 type). Calculated with
Mass ratio (mass%) of PVP = nitrogen content (mass%) × 111/14

8). Porosity of the outer surface of the hollow fiber membrane The outer surface of the hollow fiber membrane is observed with an electron microscope of 10,000 times and a photograph (SEM photograph) is taken. The image was processed with image analysis processing software to obtain the porosity of the outer surface of the hollow fiber membrane. The image analysis processing software is measured using, for example, Image Pro Plus (Media Cybernetics, Inc.). The emphasis / filtering operation is performed on the captured image so that the hole and the blockage are identified. Thereafter, the holes are counted, and when the lower polymer chain can be seen inside the holes, the holes are combined and counted as one hole. The area (A) of the measurement range and the cumulative area (B) of the pores within the measurement range were determined, and the area ratio (%) = B / A × 100. This was carried out 10 views and the average was obtained. Scale setting is performed as an initial operation, and holes on the measurement range boundary are not excluded during counting.

9. The average pore area of the apertures on the outer surface of the hollow fiber membrane was counted in the same manner as in the previous section to determine the area of each pore. In addition, holes on the measurement range boundary were excluded during counting. This was carried out for 10 fields of view and the average of all pore areas was determined.

10. Hollow Fiber Membrane Thickness Project the cross-section of the hollow fiber membrane with a projector with a magnification of 200 times, and find the inner diameter (A) and outer diameter (B) of the largest, smallest, and medium-sized hollow fibers within each field of view. Measure the thickness of each hollow fiber by the following formula,
Film thickness = (B-A) / 2
The average film thickness of 90 hollow fibers of 30 fields of view was calculated.

11. Endotoxin concentration Dialysate with an endotoxin concentration of 200 EU / L is fed from the inlet of the module at a flow rate of 500 ml / min, and dialysate containing endotoxin is filtered from the outside to the inside of the hollow fiber membrane at a filtration rate of 15 ml / min for 2 hours. The dialysate filtered from the outside of the hollow fiber membrane to the inside of the hollow fiber membrane was stored, and the endotoxin concentration of the stored solution was measured. Endotoxin concentration was analyzed using Limulus ESII Test Wako (manufactured by Wako Pure Chemical Industries, Ltd.) according to the manual method (gelation overturning method).

12 Blood Leakage Test Using a module primed with raw food, 37 ° C bovine blood, which has been inhibited by coagulation by adding citric acid, is fed to the blood purifier at 200 mL / min, and blood is fed at a rate of 20 mL / min Filter. At this time, the filtrate is returned to blood to be a circulatory system. After 60 minutes, the filtrate from the blood purifier is collected, and the red color resulting from red blood cell leakage is visually observed. In this blood leak test, 30 blood purifiers were used in each of the examples and comparative examples, and the number of blood leaked modules was examined.

13. Adhesiveness of hollow fiber membrane About 10,000 hollow fibers were bundled, mounted in a module case of 30 mmφ to 35 mmφ, and sealed with a two-component polyurethane resin to prepare a module. A leak test was conducted at five levels for each level, and the number of modules with poor urethane resin sealing was counted.

14 Residual blood of the hollow fiber membrane Fill the dialysate side of the module with a membrane area of 1.5 m ² with physiological saline, fill the blood bag with 200 ml of heparinized blood collected from a healthy person, connect the blood bag and the module with a tube, Circulate at 37 ° C. for 1 hour with a blood flow rate of 100 ml / min. Blood samples before the start of circulation and 60 minutes of circulation are sampled, and the white blood cell count and platelet count are measured. The measured value is corrected with the value of hematocrit.
Correction value = measured value (60 minutes) x hematocrit (0 minutes) / hematocrit (60 minutes)
The rate of change of white blood cells and platelets is calculated from the correction value.
Rate of change = correction value (60 minutes) / pre-circulation value x 100
After the circulation for 60 minutes, the blood was returned with physiological saline, and the number of remaining blood was counted. The evaluation was carried out with the number of remaining blood threads being 10 or less, ◯, 11 to 30 threads as Δ, and 31 or more threads as ×.

15. Priming property While the dialysate side port of the module is covered, distilled water for injection is allowed to flow from the blood side inlet port at 200 mL / min until 10 seconds elapses after the distilled water for injection reaches the outlet port. The module case was detaped by tapping the module case 5 times with forceps, and the number of bubbles passed for 1 minute was visually confirmed. The determination was made according to the following criteria.
10 / min or less: ○
11 / min or more and less than 30 / min: △
30 pieces / minute or more: ×

16. Determination of Soluble Cyclic Dimer 0.1 g of freeze-dried hollow fiber membrane or polysulfone polymer was stirred and dissolved with 100 cc of N-methyl-2pyrrolidone. A solution obtained by filtering the solution with a disk filter (0.45 μ) made of Teflon (R) was used as a sample. The measurement was carried out using a high performance liquid chromatograph, while passing N, N-dimethylformamide as an eluent at a flow rate of 0.5 cc / min through a molecular sieve column (Showa Denko Co., Ltd .: Shodex Asahi Pack GF-310HQ) Monitoring was performed at a wavelength of 270 nm in an ultraviolet detector. A fixed amount of sample solution is injected, the peak area that appears in the oligomer region is determined, and the content of soluble cyclic dimer in the sample is calculated from a calibration curve created using a previously purified soluble cyclic dimer. did.

17. Observation of insoluble aggregates on membrane surface A freeze-dried hollow fiber membrane was horizontally fixed on a data base and sliced obliquely to expose a part of the inner surface of the membrane. After silver deposition, the presence state of insoluble aggregates on the inner surface was observed with a scanning line microscope (S-530, manufactured by Hitachi, Ltd.) at a magnification of 2000 times.

18. 40 vol% ethanol extraction method In the case of a wet type in which the module is filled with a preservative solution, the internal preservative solution is first discharged from either the blood channel side or the dialysate channel side. Then, extraction operation is implemented in the following procedures.
After closing the dialysate side of the module, connecting a tube to the blood side inlet / outlet and flushing with 500 mL of distilled water, the distilled water in the module is replaced with 40 vol% aqueous ethanol. The inside of the module is filled and sealed while injecting 40 vol% ethanol aqueous solution from the dialysate side. Next, while keeping 300 mL of a 40 vol% ethanol aqueous solution at 40 ° C. while circulating it for 1 hour with a peristaltic pump (flow rate 150 mL / min), the circulating fluid is recovered to obtain an extract. When extracting not only one module but also two or more modules, it is possible to obtain a corresponding extract by repeating the above extraction operation. The obtained extract is concentrated using a rotary evaporator and freeze-dried to obtain an extraction residue (eluate). Glass instruments are sterilized by dry heat, tubes are autoclave sterilized from silicone, ethanol used for preparing the extraction solvent is distilled, and distilled water for injection is used. The amount of extraction residue is calculated as the increase in the container weight before and after concentration and freeze-drying.

19. Measurement of blood histamine level
The extraction residue of 5 modules with 40 vol% ethanol aqueous solution is dissolved in 10 mL of physiological saline for injection and administered into the forelimb vein (cephalic vein) of dogs weighing approximately 10 kg. Blood samples were collected from dogs before administration and at 5, 15, 30, and 120 minutes after administration, and the hematocrit value of each sample blood was measured, and the histamine value of each sample plasma was determined using the Histamine-ELISA kit (ICN Pharmaceuticals Inc.). And measured. Furthermore, the symptom of the dog was observed until 120 minutes after administration, and the presence or absence of anaphylactoid symptoms was examined.

(Example 1)
Polyethersulfone (Suika Chemtex Co., Ltd., SUMIKAEXCEL (R) 4800P) was purified to obtain a purified polyethersulfone having a soluble cyclic dimer content of 1.0% by weight or less based on the polysulfone polymer. . The polyethersulfone 17% by mass, polyvinylpyrrolidone (BASF Kollidon (R) K-90) 2.5% by mass, dimethylacetamide (DMAc) 77.5% by mass, RO water 3% by mass were uniformly dissolved at 50 ° C. After reducing the pressure in the system to −500 mmHg using a vacuum pump, the system was immediately sealed and allowed to stand for 15 minutes so that the solvent and the like would evaporate and the film forming solution composition would not change. This operation was repeated three times to degas the film forming solution. The film-forming solution was passed through two types of sintered filters of 30 μm and 15 μm in order, and then a 60 mass% DMAc aqueous solution was degassed in advance at −700 mmHg for 30 minutes from a tube-in orifice nozzle heated to 80 ° C. After passing through a 400 mm dry section cut off from the outside air by using a spinning tube, it was coagulated in a 20 mass% DMAc aqueous solution at 60 ° C., and was rolled up in a wet state. The average nozzle slit width of the tube-in-orifice nozzle used is 60 μm, the maximum is 61 μm, the minimum is 59 μm, the maximum and minimum slit width ratio is 1.03, the draft ratio of the film forming solution is 1.06, and the absolute humidity of the dry section Was 0.21 kg / kg dry air. During the spinning process, the roller in contact with the hollow fiber membrane was made of stainless steel whose surface was mirror-finished, and the guides were all made of stainless steel whose surface was textured.

  A polyethylene film whose surface on the hollow fiber bundle side is textured is wrapped around about 10,000 bundles of the hollow fiber membranes, then washed in hot water at 80 ° C. for 30 minutes × 4 times, and after completion of washing, 40 Drying was performed in a nitrogen atmosphere at 0 ° C. The resulting hollow fiber membrane had an inner diameter of 198.5 μm and a film thickness of 28.5 μm. It was 4.3 mass% when the mass ratio of the hydrophilic polymer in a hollow fiber membrane was measured.

  As a result of assembling a blood purifier using the hollow fiber membrane thus obtained and conducting a leak test, no adhesion failure due to the sticking of the hollow fibers was found.

  The blood purifier was filled with RO water and irradiated with γ rays at an absorbed dose of 25 kGy for crosslinking. When the hollow fiber membrane was cut out from the blood purifier after γ-irradiation and subjected to the eluate test, the amount of PVP elution was 8 ppm, which was a satisfactory level.

  The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a product that passed the leak test with a pressure drop for 10 seconds of 30 mmAq or less was used in subsequent tests. Further, when the hollow fiber membrane was taken out from the blood purifier and the outer surface was observed with a microscope, defects such as scratches were not observed. In addition, citrated fresh cow blood was flowed to the blood purifier at a blood flow rate of 200 mL / min and a filtration rate of 10 mL / min, but no blood cell leak was observed. Endotoxin filtered from the outer side of the hollow fiber to the inner side of the hollow fiber was below the detection limit and was at a level with no problem. The other analysis results are shown in Table 1.

Further, the content of the soluble cyclic dimer in the obtained hollow fiber membrane was 0.6%, and a minute amount of insoluble aggregates were present on the membrane surface. The LDH activity of this film was 10.5%. Using a blood purifier with a membrane area of 1.5 m ² , blood extraction was performed at 40 ° C. for 1 hour using a 40 vol% aqueous ethanol solution to obtain an extract. The extract of 5 modules was concentrated and freeze-dried to obtain an extraction residue, which was administered to a dog as a sample, and the blood histamine level was measured. The results are shown in Table 2.

(Comparative Example 1)
A wet hollow fiber membrane bundle was obtained in the same manner as in Example 1 except that unpurified polyethersulfone was used, the filter was not allowed to pass through, and no washing was performed. A blood purifier was assembled using the hollow fiber membrane thus obtained. The blood purifier was filled with RO water and irradiated with γ rays at an absorbed dose of 25 kGy for crosslinking. The resulting hollow fiber membrane had an inner diameter of 199.3 μm and a film thickness of 28.7 μm. The mass ratio of the hydrophilic polymer in the hollow fiber membrane was measured and found to be 9.6% by mass. When the hollow fiber membrane was taken out from the blood purifier after γ-irradiation and observed with a microscope, there was a case in which a knob-like defect that seemed to be a mixture of undissolved components was observed. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a module having a pressure drop for 10 seconds of 30 mmAq or less was used for the test. In the blood leak test using bovine blood, 3 out of 30 modules showed blood cell leaks. It is considered that there was insufficient strength and / or defects in the thin film portion because the unevenness and burst pressure were low. As a result of the endotoxin permeation test, endotoxin permeating into the hollow fiber was observed. The cause is considered to be that cleaning was not performed, so that the proportion of PVP present on the outer surface of the hollow fiber membrane increased, and endotoxin easily passed. The other analysis results are shown in Table 1.

(Comparative Example 2)
16% by mass of unrefined polyethersulfone (manufactured by Sumika Chemtex, Sumika Excel (R) 7800P), 6% by mass of polyvinylpyrrolidone (Collidon (R) K-90 by BASF), 75% by mass of DMAc, 3% by mass of water The solution was melted at 50 ° C., and the pressure in the system was reduced to −500 mmHg using a vacuum pump. The system was immediately sealed and allowed to stand for 15 minutes so that the solvent and the like were volatilized and the film forming solution composition did not change. This operation was repeated three times to degas the film forming solution. This membrane-forming solution was passed through a 30 μm filter, and simultaneously discharged and spun from a tube-in orifice nozzle heated to 60 ° C. using a 30% by mass DMAc aqueous solution previously degassed at −700 mmHg for 2 hours as a hollow forming agent. After passing through a 600 mm dry part cut off from the outside by a tube, it was solidified in a DMAc aqueous solution having a concentration of 10% by mass and 60 ° C. The nozzle slit width of the tube-in-orifice nozzle used is an average of 100μm, maximum 110μm, minimum 90μm, maximum / minimum slit width ratio 1.22, draft ratio 2.41, dry section absolute humidity 0.11kg / Kg dry air. The obtained hollow fiber membrane was passed through a water washing tank at 40 ° C. for 45 seconds to remove the solvent and excess hydrophilic polymer, and then wound up in a wet state and dried in air at 50 ° C. The obtained hollow fiber membrane had an inner diameter of 197.8 μm and a film thickness of 29.2 μm. It was 7.4 mass% when the mass ratio of the hydrophilic polymer in a hollow fiber membrane was measured.

  A blood purifier was assembled using the hollow fiber membrane thus obtained. The blood purifier was filled with pure water and irradiated with γ rays at an absorbed dose of 25 kGy for crosslinking treatment. When the hollow fiber membrane was cut out from the blood purifier after γ-ray irradiation and subjected to the eluate test, the elution amount of PVP was 12 ppm. The poor cleaning of the hollow fiber membrane was considered. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a module having a pressure drop for 10 seconds of 30 mmAq or less was used for the test. In the blood leak test using bovine blood, two of the 30 modules showed blood cell leaks. From the fact that the uneven thickness is small and the outer surface hole diameter is too large, it seems that pinholes are generated and / or broken. As a result of the endotoxin permeation test, endotoxin filtered from the outside of the hollow fiber to the inside of the hollow fiber was detected. It is presumed that endotoxin was easily permeated due to the large amount of PVP on the outer surface and the large porosity. The other analysis results are shown in Table 1.

(Example 2)
Polyethersulfone (Sumika Chemtex, Sumika Excel (R) 4800P) 18% by mass, polyvinyl pyrrolidone (BASF Kollidon (R) K-90) 3.5% by mass, DMAc73. Dissolve 5% by mass and 5% by mass of water at 50 ° C., and then reduce the pressure inside the system to −700 mmHg using a vacuum pump. Sealed and left for 10 minutes. This operation was repeated three times to degas the film forming solution. The obtained membrane-forming solution was passed through 15 μm and 15 μm two-stage filters, and then a 50 mass% DMAc aqueous solution was degassed in advance at −700 mmHg for 2 hours as a hollow forming agent from a tube-in orifice nozzle heated to 70 ° C. At the same time, it was discharged and after passing through a 300 mm air gap part cut off from the outside air by a spinning tube, it was solidified in water at 60 ° C. The nozzle slit width of the tube-in-orifice nozzle used is an average of 45 μm, the maximum is 45.5 μm, the minimum is 44.5 μm, the maximum and minimum slit width ratio is 1.02, the draft ratio is 1.06, and the absolute humidity of the dry section is 0 .12 kg / kg dry air. The hollow fiber membrane pulled up from the coagulation bath was passed through a 85 ° C. water washing tank for 45 seconds to remove the solvent and excess hydrophilic polymer, and then rolled up. The roller for changing the yarn path during the spinning process was a mirror-finished surface, and the fixing guide was a satin-finished surface.

  A polyethylene film similar to that in Example 1 was wrapped around a bundle of about 10,000 hollow fiber membranes, and then immersed and washed in a 40 vol% isopropanol aqueous solution at 30 ° C. for 30 minutes × 2 times, and then replaced with water. And dried in a nitrogen stream at 60 ° C. The resulting hollow fiber membrane had an inner diameter of 198.5 μm and a film thickness of 28.5 μm. When the mass ratio of the hydrophilic polymer in the hollow fiber membrane was measured, it was 7.3% by mass. A blood purifier was assembled using the hollow fiber membrane thus obtained. As a result of the leak test, no adhesion failure caused by the sticking of the hollow fibers was found. The blood purifier was subjected to the subsequent analysis without performing the crosslinking treatment of the hydrophilic polymer. When the hollow fiber membrane was cut out from the blood purifier not irradiated with γ-ray and subjected to the eluate test, the elution amount of PVP was as good as 6 ppm. Further, when the hollow fiber membrane was taken out from the blood purifier and the outer surface was observed with a microscope, no defects such as scratches were observed. No blood cell leak was found in the blood leak test using bovine blood. In addition, as a result of the endotoxin permeation test, endotoxin filtered from the outside of the hollow fiber to the inside of the hollow fiber was below the detection limit and was at a level with no problem. The other analysis results are shown in Table 1.

(Comparative Example 3)
Unrefined polyethersulfone (Sumika Chemtex, Sumika Excel (R) 7800P) 22 mass%, Polyvinylpyrrolidone (BASF Kollidon (R) K-30) 9 mass%, DMAc 66 mass%, water 3 mass% Was melted at 50 ° C., and the pressure in the system was reduced to −350 mmHg using a vacuum pump. The system was immediately sealed and allowed to stand for 30 minutes so that the solvent and the like were volatilized and the film forming solution composition did not change. This operation was repeated twice to degas the film forming solution. After passing the obtained film-forming solution through a two-stage filter of 30 μm and 30 μm, the tube-in-orifice nozzle heated to 50 ° C. was discharged simultaneously with a 50 mass% DMAc aqueous solution that had been degassed in advance as a hollow forming agent, After passing through a 300 mm air gap part cut off from the outside air by a spinning tube, it was solidified in water at 50 ° C. The nozzle slit width of the tube-in-orifice nozzle used is an average of 45 μm, the maximum is 45.5 μm, the minimum is 44.5 μm, the maximum and minimum slit width ratio is 1.02, the draft ratio is 1.06, and the absolute humidity of the dry section is 0 0.07 kg / kg dry air. The hollow fiber membrane pulled up from the coagulation bath was passed through a 40 ° C. water washing tank for 45 seconds to remove the solvent and excess hydrophilic polymer, and then wound up. The resulting 10,000 hollow fiber membrane bundles were not washed and dried at 40 ° C. in an air atmosphere. The resulting hollow fiber membrane had an inner diameter of 199.5 μm and a film thickness of 29.0 μm. It was 7.7 mass% when the mass ratio of the hydrophilic polymer in a hollow fiber membrane was measured.

  Adherence was observed in the hollow fiber membrane bundle after drying, and when assembling the blood purifier, the end portion adhesive resin did not enter well between the hollow fiber membranes, and the blood purifier could not be assembled. The analysis results are shown in Table 1.

(Comparative Example 4)
A tube-in-orifice nozzle which was passed through a two-stage filter of 30 μm and 15 μm as in Comparative Example 1 and then heated to 80 ° C. using a 60 mass% DMAc aqueous solution degassed in advance as a hollow forming agent. Were simultaneously discharged, passed through a 400 mm long dry section cut off from the outside air by a spinning tube, and then coagulated in a coagulation bath composed of 70 ° C. RO water. The nozzle slit width of the tube-in-orifice nozzle used is an average of 60 μm, the maximum is 65 μm, the minimum is 55 μm, the maximum and minimum slit width ratio is 1.18, the draft ratio is 1.06, and the absolute humidity of the dry section is 0.28 kg. / Kg dry air. The hollow fiber membrane pulled up from the coagulation bath was then immersed in a water washing bath at a temperature of 60 ° C. for 45 seconds, wound up, and dried in a dry heat oven at 70 ° C. The resulting hollow fiber membrane had an inner diameter of 200.2 μm and a film thickness of 30.5 μm. The mass ratio of the hydrophilic polymer in the hollow fiber membrane was measured and found to be 6.3% by mass.

  As a result of assembling a blood purifier using the hollow fiber membranes thus obtained and conducting an air leak test, it was found that bubbles were generated from the module adhesion part. It seems that the poor adhesion resulting from the fixation of the hollow fibers was caused. When a hollow fiber membrane was cut out from a blood purifier that had not been subjected to crosslinking treatment and subjected to an eluate test, the amount of PVP elution was 12 ppm. This was thought to be due to insufficient washing of the hollow fiber membrane and uncrosslinked hydrophilic polymer. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a module having a pressure drop for 10 seconds of 30 mmAq or less was used for the test. No blood cell leak was found in the blood leak test using bovine blood. As a result of the endotoxin passage test, the endotoxin concentration in the filtrate was 10 EU / L, which was a slightly high level. The analysis results of the obtained blood purifier are shown in Table 1.

(Comparative Example 5)
Unrefined polyethersulfone (Sumika Chemtex, Sumika Excel (R) 5200P) 17% by mass, Polyvinylpyrrolidone (BASF Kollidon (R) K-90) 7.5% by mass, DMAc 72.5% by mass, water 3 After the mass% was dissolved at 50 ° C., the pressure in the system was reduced to −500 mmHg using a vacuum pump, and then the system was immediately sealed and left for 30 minutes so that the solvent and the like were volatilized and the film forming solution composition did not change. . This operation was repeated three times to degas the film forming solution. The obtained film-forming solution is discharged through a tube-in orifice nozzle heated to 50 ° C. together with a 75 mass% DMAc aqueous solution that has been degassed in advance as a hollow forming agent without passing through a filter, and is blocked from the outside air by a spinning tube. After passing through a 600 mm air gap, it was solidified in 70 ° C. water. The nozzle slit width of the tube-in-orifice nozzle used is an average of 60μm, maximum 64μm, minimum 56μm, maximum / minimum slit width ratio 1.14, draft ratio 1.06, dry section absolute humidity 0.23kg / Kg dry air. The obtained hollow fiber membrane was washed with water to remove the solvent, and then wound up into about 10,000 bundles. Subsequently, it was immersed in a 30% by mass glycerin aqueous solution at 50 ° C. for 1 hour and then dried at 80 ° C. The obtained hollow fiber membrane had an inner diameter of 197.8 μm and a film thickness of 30.3 μm. It was 6.1 mass% when the mass ratio of the hydrophilic polymer in a hollow fiber membrane was measured.

  The hollow fiber membrane bundle thus obtained did not adhere to the hollow fibers because glycerin was adhered to the membrane surface, but the assembled blood purifier had a large amount of urethane oligomer at the end and sufficient safety It could not guarantee sex. The blood purifier was filled with water and irradiated with γ rays at an absorbed dose of 25 kGy. When the hollow fiber membrane was cut out from the blood purifier after γ-irradiation and subjected to the eluate test, the amount of PVP elution was 13 ppm. It was thought that molecular crosslinking was inhibited. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a module having a pressure drop for 10 seconds of 30 mmAq or less was used for the test. In the blood leak test using bovine blood, 4 of the 30 modules showed blood cell leaks. It was thought that the cause was that the thickness deviation was small and the outer surface pore diameter was too large. As a result of the endotoxin permeation test, the endotoxin filtered from the outside of the hollow fiber to the inside of the hollow fiber was at a very high level. This was considered to be due to the large open area and hole area on the outer surface. The other analysis results are shown in Table 1.

(Example 3)
Polysulfone (Amoco P-3500) 18% by mass, polyvinylpyrrolidone (BASF K-60) 9% by mass, DMAc 68% by mass and water 5% by mass were dissolved at 50 ° C. in the same manner as in Example 1. Then, after the pressure in the system was reduced to −300 mmHg using a vacuum pump, the system was immediately sealed and left for 15 minutes so that the solvent and the like were volatilized and the composition of the film forming solution was not changed. This operation was repeated three times to degas the film forming solution. After passing the obtained film-forming solution through two types of filters of 15 μm and 15 μm, the tube-in orifice nozzle heated to 40 ° C. was simultaneously discharged with a 35 mass% DMAc aqueous solution degassed in advance as a hollow forming agent, After passing through a 600 mm air gap part cut off from the outside air by a spinning tube, it was solidified in 50 ° C. water. The nozzle slit width of the tube-in-orifice nozzle used is an average of 60 μm, maximum 61 μm, minimum 59 μm, maximum and minimum slit width ratio is 1.03, draft ratio is 1.01, and dry section absolute humidity is 0.06 kg. / Kg dry air. The hollow fiber membrane pulled up from the coagulation bath was passed through a 85 ° C. water washing tank for 45 seconds to remove the solvent and excess hydrophilic polymer, and then rolled up. A bundle of about 10,000 hollow fiber membranes was immersed in pure water and washed in an autoclave at 121 ° C. for 1 hour. A polyethylene film similar to that of Example 1 was wound around the hollow fiber membrane bundle after washing, and then dried in a nitrogen stream at 45 ° C. The roller for changing the yarn path during the spinning process was a mirror-finished surface, and the fixing guide was a satin-finished surface. The resulting hollow fiber membrane had an inner diameter of 201.2 μm and a film thickness of 43.8 μm. It was 8.8 mass% when the mass ratio of the hydrophilic polymer in a hollow fiber membrane was measured.

  As a result of producing a module from the obtained hollow fiber membrane and conducting a leak test, no adhesion failure caused by the sticking of the hollow fibers was observed. A blood purifier was assembled using the hollow fiber membrane thus obtained. The blood purifier was filled with RO water and irradiated with γ rays at an absorbed dose of 25 kGy for crosslinking. When the hollow fiber membrane was cut out from the blood purifier after γ-irradiation and subjected to the eluate test, the amount of PVP elution was 7 ppm, which was a satisfactory level. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a product that passed the leak test with a pressure drop for 10 seconds of 30 mmAq or less was used in subsequent tests. Further, when the hollow fiber membrane was taken out from the blood purifier and the outer surface was observed with a microscope, defects such as scratches were not observed. In addition, citrated fresh cow blood was flowed to the blood purifier at a blood flow rate of 200 mL / min and a filtration rate of 10 mL / min, but no blood cell leak was observed. Endotoxin filtered from the outer side of the hollow fiber to the inner side of the hollow fiber was below the detection limit and was at a level with no problem. The other analysis results are shown in Table 1.

Example 4
Purified in the same manner as in Example 1, 17% by mass of polysulfone (Amoco P-1700), 5% by mass polyvinylpyrrolidone (BASF K-60), 68% by mass DMAc, and 5% by mass water were dissolved at 50 ° C. Then, after reducing the pressure in the system to −400 mmHg using a vacuum pump, the system was immediately sealed and left for 30 minutes so that the solvent and the like were volatilized and the composition of the film forming solution was not changed. This operation was repeated three times to degas the film forming solution. The obtained film-forming solution was passed through two types of filters of 15 μm and 15 μm, and then discharged from a tube-in orifice nozzle heated to 40 ° C. simultaneously with a 35 mass% DMAc aqueous solution degassed under reduced pressure as a hollow forming agent. After passing through a 600 mm air gap part cut off from the outside air by a spinning tube, it was solidified in 50 ° C. water. The nozzle slit width of the tube-in-orifice nozzle used is an average of 60 μm, the maximum is 61 μm, the minimum is 59 μm, the maximum and minimum slit width ratio is 1.03, the draft ratio is 1.01, and the absolute humidity of the dry section is 0.07 kg. / Kg dry air. The hollow fiber membrane pulled up from the coagulation bath was passed through a 85 ° C. water washing tank for 45 seconds to remove the solvent and excess hydrophilic polymer, and then rolled up. A bundle of about 10,000 hollow fiber membranes was immersed in pure water and washed in an autoclave at 121 ° C. for 1 hour. A polyethylene film was wound around the hollow fiber membrane bundle after washing, and then dried in a nitrogen stream at 45 ° C. The roller for changing the yarn path during the spinning process was a mirror-finished surface, and the fixing guide was a satin-finished surface. The resulting hollow fiber membrane had an inner diameter of 201.2 μm and a film thickness of 43.8 μm. The mass ratio of the hydrophilic polymer in the hollow fiber membrane was measured and found to be 5.2 mass%.

  As a result of assembling an evaluation module using the obtained hollow fiber membrane and conducting a leak test, no adhesion failure due to the sticking of the hollow fibers was found. A blood purifier was assembled using the hollow fiber membrane thus obtained. The blood purifier was filled with RO water and irradiated with γ rays at an absorbed dose of 25 kGy for crosslinking. When the hollow fiber membrane was cut out from the blood purifier after γ-irradiation and subjected to the eluate test, the PVP elution amount was 7 ppm, which was a satisfactory level. The blood purifier was filled with pressurized air at a pressure of 0.1 MPa, and a product that passed the leak test with a pressure drop for 10 seconds of 30 mmAq or less was used in subsequent tests. Further, when the hollow fiber membrane was taken out from the blood purifier and the outer surface was observed with a microscope, defects such as scratches were not observed. In addition, citrated fresh cow blood was flowed to the blood purifier at a blood flow rate of 200 mL / min and a filtration rate of 10 mL / min, but no blood cell leak was observed. Endotoxin filtered from the outer side of the hollow fiber to the inner side of the hollow fiber was below the detection limit and was at a level with no problem. The other analysis results are shown in Table 1.

(Comparative Example 6)
A spinning dope was obtained in the same manner as in Example 1 except that it was used without purification of polyethersulfone in Example 1 and PVP (Collidon (R) K-30 manufactured by BASF) was used. The LDH activity of this membrane was as high as 61.5%.

  The hollow fiber membrane blood purifier of the present invention has high safety and high performance stability and excellent module assemblability, and is suitable for a blood purifier having high water permeability used for the treatment of chronic renal failure. . Therefore, it is important to contribute to industrial development.

Claims (5)

A hollow fiber membrane made of a polysulfone-based polymer containing a hydrophilic polymer, having a film thickness of 10 to 50 μm, an outer surface porosity of 8 to 25%, an unevenness of 0.6 or more, and hydrophilicity on the outer surface The polymer is present in an amount of 25 to 50% by mass, the elution of the hydrophilic polymer from the hollow fiber membrane is 10 ppm or less, the burst pressure of the hollow fiber membrane is 0.5 to 2.0 MPa, the polysulfone A blood purifier housing a hollow fiber membrane having a soluble cyclic dimer content of 1.0% by mass or less with respect to a polymer, and having a water permeability of 150 ml / m ² / hr / mmHg or more. High performance hollow fiber membrane blood purifier. ^2. The highly water-permeable hollow fiber blood purifier according to claim 1, wherein an average pore area on the outer surface of the hollow fiber membrane is 0.3 to 1.0 μm ² .   3. The highly water-permeable hollow fiber membrane blood purifier according to claim 1, wherein a mass ratio of the hydrophilic polymer to the hydrophobic polymer is 1 to 20 mass%.   The highly water-permeable hollow fiber membrane blood purifier according to any one of claims 1 to 3, wherein the hydrophilic polymer is polyvinylpyrrolidone.   The highly water-permeable hollow fiber membrane blood purifier according to any one of claims 1 to 4, wherein the hydrophilic polymer is crosslinked and insoluble in water.