Hollow fiber membrane for blood purification and blood purification apparatus using the same
An object of the present invention is to provide a hollow fiber membrane with enhanced phosphorus-removing performance without impairing antithrombogenicity in order to inhibit in vivo accumulation of phosphate ions in living body that might cause bone metabolism disorders. The present inventors have found that a hollow fiber membrane having a specific membrane structure and a specific membrane composition possesses a very useful range for inner surface charges of the membrane. More particularly, the inventors have discovered that the above object can be achieved in a limited range in which the zeta potential on the inner surface of a hollow fiber membrane measured under given certain conditions is greater than −3.0 mV but less than 0 mV. This finding has led to the completion of the present invention.
1. A hollow fiber membrane for blood purification having an integrally continuous structure from the inner membrane surface to the outer membrane surface and comprising a hydrophobic polymer and a hydrophilic polymer, and
the hollow fiber membrane comprising a polyvinyl pyrrolidone as the hydrophilic polymer in the range of 3.0 to 5.0 wt % based on the hollow fiber membrane,
exhibiting a zeta potential on the inner surface thereof of greater than −3.0 mV but less than 0 mV at pH 7.5, when measured using a sample with an embedded resin on the outer side for allowing the electrolyte solution to flow through only the inside of the hollow fiber, and using a 0.001 mol/l potassium chloride aqueous solution as an electrolyte solution.
2. The follow fiber membrane for blood purification according to claim 1 , further exhibiting:
(a) a polyvinyl pyrrolidone sieving coefficient of 45% or more in a filtration test using a polyvinyl pyrrolidone aqueous solution with a weight average molecular weight of 40,000,
(b) a protein adsorption amount of 65 mg/m 2 or less,
(c) a breaking strength of 60 kg/cm 2 or more, and
(d) a breaking elongation of 60% or more.
3. The hollow fiber membrane for blood purification according to claim 2 , wherein an overall mass transfer coefficient of phosphorous is 0.040 cm/min or greater.
4. The hollow fiber membrane for blood purification according to claim 2 , further comprising: a thickness of a dense layer between 1 and 5 μm.
5. A blood purification apparatus comprising the hollow fiber membrane according to claim 2 , installed in a cylindrical container having two nozzles for flowing a dialysate, the cylindrical container having both ends fabricated with a potting material for separating the hollow inside of the membrane from the outside by a membrane wall and the cylindrical container further having a header cap for flowing blood fitted on both ends.
6. The hollow fiber membrane for blood purification according to claim 1 , wherein an overall mass transfer coefficient of phosphorous is 0.040 cm/min or greater.
7. The hollow fiber membrane for blood purification according to claim 6 , further comprising: a thickness of a dense layer between 1 and 5 μm.
8. A blood purification apparatus comprising the hollow fiber membrane according to claim 6 , installed in a cylindrical container having two nozzles for flowing a dialysate, the cylindrical container having both ends fabricated with a potting material for separating the hollow inside of the membrane from the outside by a membrane wall and the cylindrical container further having a header cap for flowing blood fitted on both ends.
9. The hollow fiber membrane for blood purification according to claim 1 , further comprising: a thickness of a dense layer between 1 and 5 μm.
10. A blood purification apparatus comprising the hollow fiber membrane according to claim 9 , installed in a cylindrical container having two nozzles for flowing a dialysate, the cylindrical container having both ends fabricated with a potting material for separating the hollow inside of the membrane from the outside by a membrane wall and the cylindrical container further having a header cap for flowing blood fitted on both ends.
11. A blood purification apparatus comprising the hollow fiber membrane according to claim 1 , installed in a cylindrical container having two nozzles for flowing a dialysate, the cylindrical container having both ends fabricated with a potting material for separating the hollow inside of the membrane from the outside by a membrane wall and the cylindrical container further having a header cap for flowing blood fitted on both ends.
12. The blood purification apparatus according to claim 11 , wherein the hollow fiber membrane has a phosphorus clearance of at least 180 ml/min per a membrane area of 1.5 m 2 .
13. The follow fiber membrane for blood purification according to claim 1 , wherein the hydrophobic polymer is selected from the group consisting of a polysulfone-based resin, polyether sulfone-based resin, polyamide-based resin, polyimide-based resin, polyphenyl ether-based resin, and polyphenylene sulfide-based resin.