Hollow fiber membranes and method of manufacture
First Claim
1. An asymmetric, microporous, hollow fiber membrane comprising a polyimide polymer wherein said polyimide polymer has a molecular weight of about 30,000 daltons to about 125,000 daltons and wherein said hollow fiber membrane has an inner diameter of approximately 280 microns and an outer diameter of approximately 380 microns and a pore size range of approximately 0.001 microns to about 0.5 microns and wherein said hollow fiber membrane is characterized by a uniform sponge structure and the absence of voids.
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Abstract
An asymmetric, microporous hollow fiber membrane comprising a polyimide is disclosed. The hollow fiber membrane is chemically inert to aqueous solutions and/or blood, is immediately rewettable after repeated steam and chemical sterilizations, has superior clearance, sieving, and water permeability characteristics and is usable over a wide range of applications such as dialysis and water filtration. Also disclosed is the process for manufacturing the polyimide hollow fiber membrane.
74 Citations
31 Claims
- 1. An asymmetric, microporous, hollow fiber membrane comprising a polyimide polymer wherein said polyimide polymer has a molecular weight of about 30,000 daltons to about 125,000 daltons and wherein said hollow fiber membrane has an inner diameter of approximately 280 microns and an outer diameter of approximately 380 microns and a pore size range of approximately 0.001 microns to about 0.5 microns and wherein said hollow fiber membrane is characterized by a uniform sponge structure and the absence of voids.
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9. A process for the manufacture of an asymmetric, microporous hollow fiber membrane comprising the steps of:
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(a) passing, through an outer annular orifice of a tube-in-orifice spinneret, a polymeric solution comprising about 15-25 wt. % of a highly polar polyimide polymer dissolved in a solvent with respect to the polymer, said solution having a viscosity of about 1500-5000 cps, to form an annular liquid; (b) passing, though the inner tube of the spinneret, into the center of the annular liquid, a precipitating solution comprising about (I) 99-65 wt. % of a solvent with respect to the polymer, and (ii) 1-35 wt. % of a non-solvent with respect to the polymer, wherein the precipitating solution interacts with the polymeric solution to form an annular polymer precipitate; (c) dropping the polymer precipitate through the atmosphere or an augmented atmosphere at a distance of about 0.5-0.2 meters; (d) quenching the polymer precipitate in a bath maintained at about 15°
-45°
C. to form a hollow fiber; and(e) taking up the fiber at a rate of about 40-70 meters/min, wherein said hollow fiber membrane is characterized by uniform sponge structure and the absence of voids. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. A process for the manufacture of an asymmetric, microporous hollow fiber membrane comprising the steps of:
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(a) passing, through an outer annular orifice of a tube-in-orifice spinneret, a polymeric solution comprising about 16-18 wt. % of a highly polar polyimide polymer dissolved in a solvent with respect to said polymer, said solution having a viscosity of about 1500-5000 cps, to form an annular liquid; (b) passing, through the inner tube of the spinneret, into the center of the annular liquid, a precipitating solution comprising about (i) about 80 wt. % of a solvent with respect to said polymer, and (ii) about 20 wt. % water, wherein the precipitating solution interacts with the polymeric solution to form an annular polymer precipitate; (c) dropping the polymer precipitate through the atmosphere or an augmented atmosphere for about 0.5-2.0 meters; (d) quenching the polymer precipitate in a bath maintained at about 15°
-45°
C. to form a hollow fiber; and(e) taking up the fiber at a rate of about 40-70 meters/min; wherein said fiber membrane is uniformly porous, characterized by the absence of voids, and has a water permeability of at least 500 mL/hr/mmHg/m2. - View Dependent Claims (25, 26, 27)
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28. An asymmetric, microporous, hollow fiber membrane comprising a polyimide polymer having the structure:
- ##STR23## wherein 10% to 90% of the R groups are ##STR24## an the remaining R groups are ##STR25## wherein at a blood flow rate of 200 mL/min, said membrane has a high rate of water permeability of about 17 mL/min/mmHg/m2 ;
a high clearance rate of 175-190 mL/min for urea, 150-180 mL/min for creatinine and phosphorous, about 88-125.1 mL/min for Vitamin B12 and about 125-165 mL/min for Cytochrome C; and
high sieving coefficients of from about 0.01 or less for albumin, and from about 0.65 to about 1.0 for myoglobin for fibers having 1.25 m2 active surface area; and
wherein said hollow fiber membrane is characterized by a uniform sponge-like structure and the absence of voids. - View Dependent Claims (29, 30, 31)
- ##STR23## wherein 10% to 90% of the R groups are ##STR24## an the remaining R groups are ##STR25## wherein at a blood flow rate of 200 mL/min, said membrane has a high rate of water permeability of about 17 mL/min/mmHg/m2 ;
Specification