JP3032618B2 - Hollow fiber membrane for hemodialysis and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hollow fiber membrane for hemodialysis comprising an ethylene-vinyl alcohol copolymer and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, a hollow fiber membrane made of an ethylene-vinyl alcohol (hereinafter abbreviated as EVA) copolymer has a good anti-hemolytic property and anti-thrombotic property, and has a high durability and a high chemical stability. Is widely used as a dialysis membrane for artificial kidneys. As such a hollow fiber membrane for hemodialysis, for example, JP-B-58-36602 and JP-B-58-36602.
No. 3-11909 proposes an anisotropic hollow fiber membrane having a thin dense layer on the outer surface of the hollow fiber membrane and a porous layer on the inner surface of the hollow fiber membrane. The hollow fiber membrane having the anisotropic structure can be produced under the conditions in which the polymer concentration and the coagulation bath temperature are strictly specified.

[0003]

However, in recent years, with the advancement of dialysis medical treatment, the required performance of membranes has been increased, and in particular, labor saving at dialysis sites, reduction of dialysis time, and the like are required. Needless to say, a hemodialysis membrane having high water permeability and high diffusion permeability of a low molecular weight substance, and further having a high rejection in the albumin region is desired. However, conventional hollow fiber membranes for hemodialysis having an anisotropic structure made of an EVA-based polymer have a problem that the rejection in the albumin region is low although the water permeability and the diffusion permeability of low-molecular substances are excellent. Therefore, an object of the present invention is to provide a hollow fiber membrane for hemodialysis comprising an EVA-based copolymer having excellent water permeability and diffusion permeability of a low molecular weight substance and having a high rejection in an albumin region. Another object of the present invention is to provide a method for producing a hollow fiber membrane for hemodialysis comprising the above EVA-based copolymer.

[0004]

Means for Solving the Problems The present inventors have studied in detail the structure of a conventional hollow fiber membrane for hemodialysis comprising an EVA-based copolymer in order to achieve the above object, and as a result, have found that an anisotropic structure has been obtained. The present inventors have found that a hemodialysis membrane having a high rejection rate in the albumin region can be provided by strictly controlling the pores of the dense layer of the hollow fiber membrane for hemodialysis, and as a result of further studies, the present invention has been achieved. That is, the invention according to claim 1 of the present invention provides a method in which the inner surface of a hollow fiber membrane composed of an ethylene-vinyl alcohol-based copolymer is 30 ° or less.
A thin dense layer having fine pores, a microporous layer having a volume occupied by pores of 0.01 μ or less of 10% or less and a porosity of 40% or more on the inner and outer surfaces of the hollow fiber membrane, And the water permeability in the bovine blood system is 15 ml / mmHg / Hr / m
² or more, the overall mass transfer coefficient of urea is 0.03 cm / mi
n is a hollow fiber membrane for hemodialysis, wherein the albumin rejection is 95% or more.

[0005] The invention according to claim 2 of the present invention has a polymerization degree of 8
00 or more, saponification degree 95 mol% or more, ethylene content 10
~ 60 mol% of an ethylene-vinyl alcohol copolymer is dissolved in a solvent, and a halogenated salt is introduced from the inside of the annular nozzle.
A method for producing a hollow fiber membrane for hemodialysis, comprising coagulating in a coagulating solution containing water as a component while injecting an aqueous solution containing 5% by weight or more of a compound .

The hollow fiber membrane for hemodialysis comprising the EVA copolymer of the present invention has an anisotropic structure having a thin dense layer on the inner surface. Such a dense layer greatly affects the passage of solutes such as low molecular substances such as urea and inorganic substances and the prevention of passage of substances in the albumin region. Although pores cannot be clearly confirmed on the surface by observation with an electron microscope (× 10000), it is necessary to provide strictly controlled micropores of 30 A or less in order to prevent the passage of substances in the albumin region. The thickness of the dense layer is about 30 to 100A.

[0007] The microporous layers on the inner and outer surfaces of the hollow fiber membrane have relatively large vacuoles, and the porosity is 40% or more and the volume occupied by pores of 0.01 µm or less is 10%.
It is as follows. Usually, it is appropriate that the porosity is 50% or more and the volume occupied by pores of 0.01 micron or less is 5% or less. The pore shape in the microporous layer has a network structure, a microporous structure, a honeycomb structure, a particle structure and the like. The fact that the inside and outside surfaces of this hollow fiber membrane have a microporous structure greatly affects water permeability. The porosity (P) in the present invention is a value obtained from the following equation. P = (1−ρa / ρb) × 100 where, ρa: specific gravity of the EVA copolymer constituting the hollow fiber membrane, ρb: apparent specific gravity of the hollow fiber membrane, pore distribution is a value measured by a mercury porosimeter. I asked more. The hollow fiber membrane for hemodialysis comprising the EVA copolymer of the present invention usually has an outer diameter of 100 to 1000 μm and a thickness of 5 to 5 μm.
１００100 μm is preferably used.

[0008] The hollow fiber membrane for hemodialysis according to the present invention is permeability of bovine blood system permeability of water even 30~200ml / mmHg / Hr / m ² varies to ^{15~30ml / mmHg / Hr / m 2} , The albumin inhibition rate is 60-90% in the water system, but 95% in the bovine blood system.
It becomes higher with above. However, the overall mass transfer coefficient of urea, which is a low molecular weight substance, is small even when it is changed to bovine blood system.
cm / min or more is maintained. Such a hollow fiber membrane for hemodialysis is not only used as a dialysis membrane for an artificial kidney,
For example, it can be used as a filtration membrane for a filtration type artificial kidney, a filtration membrane or a concentration membrane for ascites fluid, a plasma fractionation membrane, and the like.

Next, a method for producing the hollow fiber membrane for hemodialysis according to the present invention will be described. EVA used in the present invention
The system copolymer may be any of random, block and graft copolymers, but those having a degree of polymerization of less than 800 preferably have a degree of polymerization of 800 or more because the mechanical strength during film formation is not sufficient. Usually, those having a polymerization degree of 1000 or more are used. . 10 mol% as ethylene content
In the following, there is a problem that the mechanical properties when wet are insufficient and there are many eluted substances. On the other hand, if it is 60 mol% or more, the diffusion permeability of the solute is reduced. Therefore, those having an ethylene content of 10 to 60 mol%, usually 20 to 45 mol%, are preferably used. The saponification degree of the EVA copolymer is required to be 95 mol% or more from the viewpoint of mechanical strength when wet, and a substantially completely saponified one having a saponification degree of 99 mol% or more is usually used.

The EVA copolymer used in the present invention contains, for example, a copolymerizable polymerizable monomer such as methacrylic acid, vinyl chloride, methyl methacrylate, acrylonitrile and vinyl pyrrolidone in an amount of 15 mol% or less. It may be copolymerized, and crosslinking is introduced by treating the EVA-based copolymer with an inorganic crosslinking agent such as boron or an organic crosslinking agent such as diisocyanate or dialdehyde before or after spinning. What was done,
Alternatively, those in which a functional hydroxyl group of a vinyl alcohol unit is acetalized with an aldehyde such as formaldehyde, acetaldehyde, butyraldehyde, and benzaldehyde in a range of 30 mol% or less are also included. Crosslinking with a polyhydric aldehyde compound is preferred because the heat resistance and strength of the film are greatly improved.

Solvents for dissolving the EVA copolymer include monohydric alcohols such as methanol and ethanol, polyhydric alcohols such as ethylene glycol, propylene glycol and glycerin, phenol, meta-cresol and the like.
N-methylpyrrolidone, formic acid, and hydrates thereof are known, but blood having high water permeability and high diffusion permeability of low molecular weight substances, which are the object of the present invention, and having high rejection in the albumin region In order to obtain a hollow fiber membrane for dialysis, it is preferable to use dimethylsulfoxide, dimethylacetamide, pyrrolidone, N-methylpyrrolidone or a mixture thereof as a solvent. When the EVA-based copolymer is dissolved in the above-mentioned solvent, particularly dimethyl sulfoxide, it may contain water or another solvent such as methanol, isopropyl alcohol or dimethylformamide, or may contain other liquids and inorganic salts having good miscibility with the solvent. good.

In dissolving the EVA-based copolymer in the above-mentioned solvent, the concentration thereof can be arbitrarily selected.
%, Preferably in the range of 5 to 20% by weight. The temperature of the polymer solution is usually from 0 to 120C, preferably from 5 to 80C. If the temperature exceeds 120 ° C., the polymer may be deteriorated. If the temperature is lower than 0 ° C., the viscosity of the stock solution tends to be too high, and spinning tends to be difficult.

In order to produce the hollow fiber membrane for hemodialysis of the present invention, a double annular nozzle is used, and at least one of an acid, a base and a salt thereof is added at 5% by weight to the center of the nozzle. As described above, the polymer solution is extruded into a coagulation liquid containing water as a component and solidified while pouring an aqueous solution usually containing 10% by weight or more. The kind of the acid, base, and salt compound used here can be arbitrarily selected.

Acids, bases and their salt compounds include, for example, acids, bases, such as HCl, HBr, NaOH and LiOH, LiCl, NaCl, NaBr, NaI, N
Hl, KBr, MgCl ₂ , CaCl ₂ , MgBr ₂ ,
Monovalent, divalent, such as AlCl ₃ , ZnCl ₂ , CuCl ₂ ,
Trivalent halide compound, HNO ₃ , NaNO ₃ , C
a (NO ₃ ) ₂ , LiClO ₃ , KClO ₃ , Mg (C
10 ₃ ) ₂ , Na ₂ SO ₄ , H ₂ SO ₄ , (NH ₄ ) ₂
SO ₄ , H ₃ PO ₄ , KAl (SO ₄ ) ₂ , Na ₃ PO ₄
Such as nitric acid, chloric acid, sulfuric acid, phosphoric acid, and salt compounds thereof,
Acetate compounds such as NaCH ₃ COO and Ca (CH ₃ COO) ₂ can be mentioned. Among them, CaCl ₂ , M
_{gCl 2, CaBr 2, MgBr 2} , ZnCl 2, Cu
A divalent halide salt compound such as Cl ₂ is preferably used. Further, CaCl ₂ is preferable in terms of safety and economy. The concentration of these salts is preferably at least 5% by weight, usually at least 10% by weight. If the amount is less than 5% by weight, the effect of the salt will not be sufficiently exerted, and the albumin rejection will be poor.
Further, the temperature of the injection solution is suitably from 10 to 50 ° C. Usually, 20 to 40 ° C is preferable. If the temperature is out of the above-mentioned temperature range, the diffusion permeability of the low-molecular substance is undesirably reduced.

An aqueous medium is used as a coagulant used for the coagulation liquid. Normally, a mixed solvent of water and an organic solvent soluble in water such as dimethylsulfoxide, dimethylacetamide, pyrrolidone, N-methylpyrrolidone, alcohol, and the like, and water containing an acid, a base, and a salt thereof used in an injection solution. Are used. Among them, a mixed solvent of dimethyl sulfoxide and water is preferably used as a coagulant.

The method for producing the hollow fiber membrane for hemodialysis of the present invention includes a wet method in which a solution of an EVA-based copolymer dissolved in a solvent is directly extruded from an annular nozzle into a coagulation solution, and coagulation is performed. Any method of a dry-wet method in which the combined solution is extruded from the annular nozzle and allowed to pass through a gas atmosphere and solidify in a coagulating liquid may be used.

The temperature of the coagulating liquid is usually 0 to 50 ° C., preferably 5 to 30 ° C. If it is lower than this, the entire membrane structure may be densified, and the water permeability and the diffusion permeability of the low-molecular substance may be reduced. On the other hand, if it is higher than this, the albumin rejection rate decreases and spinning becomes unstable, which is not preferable. When water and the above-mentioned organic solvent are mixed and used as the coagulating liquid, in addition to the above-mentioned conditions, when the concentration of the organic solvent exceeds 10% by weight, particularly, the concentration of the organic solvent (C)% by weight
It is preferable to carry out spinning under such a condition that a relationship of C <T is satisfied between the temperature and the temperature (T) ° C. of the mixed solvent. If the concentration is higher than this, the diffusion permeability of the solute deteriorates. When the concentration of the organic mixed solvent exceeds 40% by weight, the diffusion permeability of the solute is good even if the condition of C <T is not satisfied, but the film strength tends to be weak.

The nozzle draft (the ratio between the linear speed of discharging the undiluted solution from the nozzle orifice and the winding speed from the coagulation bath) during spinning is usually 1.0 to 5.0. Preferably 2.0-
3.5. If it is lower or higher than this range, the diffusion permeability of the low-molecular substance is undesirably reduced. The thickness of the dried hollow fiber membrane obtained at this time is preferably in the range of 30 to 60 microns. If it is thicker than this, the diffusion permeability of the low-molecular substance tends to gradually deteriorate. If the thickness is smaller than this, the film strength becomes weak. Preferably it is 35 to 50 microns.

After completion of the solidification, stretching and wet heat treatment are carried out at a temperature of 40 to 80 ° C., preferably 55 to 70 ° C.
° C. If the wet heat treatment is insufficient, the processability in the subsequent process is impaired, and the storage stability of dimensions and performance after drying is reduced. If the wet heat treatment is excessive, the film structure changes, and the desired performance of the present invention cannot be obtained. The wet heat treatment is usually performed by passing the hollow fiber through water while also washing with water.However, the wet heat treatment and the water washing need not always be performed at the same time, and the hollow fiber is passed through a saturated steam atmosphere under the wet heat treatment. After performing the wet heat treatment, necessary water washing can be performed. Conversely, wet heat treatment may be performed after water washing. However, in the continuous process, it is preferable to perform the wet heat treatment and the water washing at the same time in terms of simplification of the process.

The film in a wet state is immersed in a water-miscible volatile organic solvent to replace water present on the surface or inside of the film, and then dried at normal pressure or reduced pressure. As the organic solvent in this case, a lower aliphatic alcohol or ketone having 1 to 5 carbon atoms is preferable, and for example, methanol, ethanol, amyl alcohol, acetone, methyl ethyl ketone, diethyl ketone and the like are used. Of these, acetone is particularly preferred. The drying is performed under normal pressure or reduced pressure, and the temperature and the steam pressure are 55 ° C. or less, preferably 50 ° C. or less, and the steam pressure is 20 mmHg or less, preferably 10 mmHg or less. By performing solvent replacement and drying under such conditions, drying can be performed while maintaining wet performance.

The dried hollow fiber membrane is subjected to dry heat treatment mainly for the purpose of improving the storage stability of dimensions and performance. Dry heat treatment temperature is 40-70 ° C, preferably 55-65 ° C
It is. Above this, the hollow fiber membrane may be flattened during the constant-length heat treatment. Further, a change occurs in the film structure, and the performance is reduced. Below this, sufficient heat fixation is not possible, and shrinkage proceeds with time, resulting in a change in the performance of the film. The water vapor pressure in the dry heat treatment atmosphere must be 60 mmHg or less. Above this, water molecules are adsorbed on the EVA copolymer, and when released into a room temperature atmosphere after the dry heat treatment, the water molecules are desorbed. The film structure changes with the separation, and the performance is reduced. After the dry heat treatment, the EVA copolymer hollow fiber membrane is cut into a certain length, and then bundled into a certain number to form a hollow fiber bundle.

The hollow fiber membrane thus obtained has excellent dimensional stability in a dry state, and does not change with time even in the state of a hollow fiber bundle, which is advantageous for storage. Moreover, since it is dried, it is convenient for transportation and the like. The performance before drying can be reproduced by re-wetting the dried hollow fiber membrane with water or saline before use.

[0023]

It is not clear why the hollow fiber membrane for hemodialysis of the present invention has excellent water permeability and diffusion permeability of low molecular weight substances, and also has a high rejection in the albumin region. When an aqueous solution of such a salt compound is injected, the EVA-based copolymer solidifies quickly due to a salting-out effect, so that a firm and dense layer is formed on the inner surface of the hollow fiber membrane. It is presumed that coagulation is promoted by the chelating effect of the copolymer on the hydroxyl groups, and that a stronger dense layer is formed.

[0024]

【Example】

Example 1 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, a 20% by weight aqueous solution of CaCl ₂ as an internal injection solution at 20 ° C.
At 20 ° C., 10 with nozzle draft 2.5
The undiluted solution was extruded into water containing DMSO by weight, solidified, subjected to wet heat stretching, drying and dry heat treatment to obtain a dry hollow fiber membrane. FIG. 1 shows an electron micrograph (2000 times) showing the cross-sectional structure of this film. This film has a dense layer thickness of 0.3
μ, the porosity was 62%, the ratio of the volume occupied by pores of 0.01 μ or less was 5%, and the film thickness was 45 μ. In addition, this hollow fiber is assembled as a hollow fiber bundle into a module with an effective area of 1 m ² , and water-based water permeability according to the dialyzer performance evaluation standard.
Urea clearance, albumin rejection, and water permeability, urea clearance and albumin rejection were measured using bovine blood with a hematocrit value of 30% and total protein of 6 g / dl in accordance with the operation procedure of an aqueous system. The overall mass transfer coefficient (K) of urea was determined from the following formula based on the urea clearance data. Table 1 shows the results.

K = [Q _B / A × (1−Z)] × LN (1−EZ) / (1−E) E = C _L / Q _B Z = Q _B / Q _D Q _B : blood side inlet Flow rate (ml / min) Q _D : flow rate at the dialysate side inlet (ml / min) A: membrane area (cm ² ) CL: urea clearance (ml / min)

Example 2 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, while injecting a 20 wt% aqueous solution of NaCl as an internal injecting solution at 20 ° C, the stock solution was extruded into water containing 20 wt% and 10 wt% DMSO by nozzle draft 2.5 to coagulate. Thereafter, the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane. The film had a dense layer thickness of 0.2 μm, a porosity of 60%,
The ratio of the volume occupied by pores of 01 μm or less was 7%, and the film thickness was 46 μm. Table 1 shows the performance of the hollow fiber membrane.

Example 3 Ethylene content 25 mol%, degree of polymerization 1400, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 15% by weight to prepare a spinning dope. Using a double ring nozzle, while injecting a 10% by weight aqueous solution of CaCl ₂ as an internal injection solution at 30 ° C., the stock solution was extruded into water containing 7% by weight of DMSO at 15 ° C. with a nozzle draft 3.2 to coagulate. Thereafter, the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane.
The film has a dense layer thickness of 0.05μ, porosity of 68%, 0.01
The ratio of the volume occupied by the submicron pores was 3%, and the film thickness was 42 μm. Table 1 shows the performance of the hollow fiber membrane.

Example 4 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double-ring nozzle, H ₂ SO ₄ , 20% by weight aqueous solution was used as an internal injection solution at 20 ° C.
At 20 ° C., 10 with nozzle draft 2.5
The undiluted solution was extruded into water containing DMSO in an amount of 100% to coagulate, and the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane. The film has a dense layer thickness of 0.1 μm, a porosity of 63%, and a thickness of 0.1 μm.
The ratio of the volume occupied by pores of 01 μm or less was 4%, and the film thickness was 44 μm. Table 1 shows the performance of the hollow fiber membrane.

Example 5 Ethylene content 33 mol%, polymerization degree 1300, saponification degree 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double-ring nozzle, an undiluted solution was extruded into water containing 20% by weight and 10% by weight DMSO by a nozzle draft 2.5 while injecting a 20% by weight aqueous solution of NaOH as an internal injection solution at 20 ° C., and solidified. ,
Thereafter, the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane. The film has a dense layer thickness of 0.2μ, porosity of 60%, 0.0
The ratio of the volume occupied by pores of 1 micron or less was 5% and the film thickness was 40 μm. Table 1 shows the performance of the hollow fiber membrane.

Example 6 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, while injecting CaCl ₂ , 7% by weight aqueous solution as an internal injection solution at 20 ° C., the stock solution was pushed out into water containing 20% at 10% DMSO by nozzle draft 2.5, and solidified. Let
Thereafter, the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane. The film had a dense layer thickness of 0.04 μm, a porosity of 64%,
The ratio of the volume occupied by the pores of 01 μm or less was 6%, and the film thickness was 42 μm. Table 1 shows the performance of the hollow fiber membrane.

Example 7 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, CaCl ₂ , 10% by weight, NaNO ₃ ,
While injecting a 10% by weight mixed aqueous solution at 20 ° C., the undiluted solution is extruded into water containing 10% by weight DMSO at 20 ° C. with a nozzle draft 2.5 to coagulate, and the same treatment as in Example 1 is performed. Thus, a dried hollow fiber membrane was obtained. The film had a dense layer thickness of 0.2 μm, a porosity of 61%, a volume ratio of pores of 0.01 μm or less of 5%, and a film thickness of 42 μm. Table 1 shows the performance of the hollow fiber membrane.

Comparative Example 1 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, while injecting water as an internal injection liquid at 20 ° C., the undiluted solution was extruded into water containing 10% by weight of DMSO at 20 ° C. with a nozzle draft 2.5 to coagulate. A dry hollow fiber membrane was obtained by performing the same treatment as described above. The film has a dense layer thickness of 0.
The porosity was 68 μm, the volume ratio occupied by pores of 0.01 μm or less was 4%, and the film thickness was 43 μm. Table 1 shows the performance of the hollow fiber membrane.

Comparative Example 2 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double-ring nozzle, while injecting CaCl ₂ and a 3% by weight aqueous solution as an internal injection solution at 20 ° C., the stock solution was extruded into water containing 20% by weight and 10% by weight DMSO with a nozzle draft 2.5, and solidified. Then, the same treatment as in Example 1 was performed to obtain a dried hollow fiber membrane. The film has a dense layer thickness of 0.02μ, porosity of 67%,
The ratio of the volume occupied by pores of 0.01 μm or less was 4%, and the film thickness was 42 μm. Table 1 shows the performance of the hollow fiber membrane.

Comparative Example 3 Ethylene content 33 mol%, degree of polymerization 1300, degree of saponification 9
9.9 mol% of the EVA copolymer was dissolved in DMSO at 17% by weight to prepare a spinning dope. Using a double ring nozzle, while injecting nitrogen gas at 20 ° C., the nozzle draft 2.0
The undiluted solution was extruded into water containing 6% by weight of DMSO at 10 ° C. and coagulated, and the same treatment as in Example 1 was performed to obtain a dry hollow fiber membrane. The film has a dense layer thickness of 0μ and a porosity of 4
3%, 5% of the volume occupied by pores of 0.01 μm or less, and 34 μm in film thickness. Table 1 shows the performance of the hollow fiber membrane.

[0035]

[Table 1]

[0036]

According to the hemodialysis membrane for artificial kidney of the present invention, a strong dense layer is formed by using an aqueous solution of an acid, a base and a salt compound thereof in a solution to be injected into a double-ring nozzle. High water permeability and diffusion permeability of low molecular substances,
In addition, since it has a high rejection rate in the albumin region, a high-performance hemodialysis membrane for artificial kidney can be provided.

[Brief description of the drawings]

FIG. 1 is an electron micrograph (× 2000) showing a cross-sectional structure of a hemodialysis membrane for an artificial kidney of the present invention.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-164428 (JP, A) JP-A-62-163705 (JP, A) JP-A-63-17686 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) A61M 1/18

Claims (2)

(57) [Claims] 1. An inner surface of a hollow fiber membrane composed of an ethylene-vinyl alcohol-based copolymer having a fine pore of 30 ° or less.
A thin dense layer having a microporous layer having a volume occupied by pores of 0.01 μ or less of 10% or less and a porosity of 40% or more on the inner and outer surfaces of the hollow fiber membrane; Water permeability in the system is not less than 15 ml / mmHg / Hr / m ² ,
The overall mass transfer coefficient of urea is 0.03 cm / min or more,
A hollow fiber membrane for hemodialysis having an albumin rejection of 95% or more. 2. A polymerization degree of 800 or more and a saponification degree of 95 mol%.
As described above, an ethylene-vinyl alcohol copolymer having an ethylene content of 10 to 60 mol% is dissolved in a solvent, and while an aqueous solution containing 5% by weight or more of a halide salt compound is injected from the inside of the annular nozzle, water is removed. A method for producing a hollow fiber membrane for hemodialysis, comprising coagulating in a coagulating solution as a component.