Porous polypropylene membrane and methods for production thereof

Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Miscellaneous

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623 11, 61F 254, A61F 254

Patent

active

051395290

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a porous polypropylene membrane and a method for the production thereof.
Further, this invention relates to a porous polypropylene hollow fiber membrane, a method for the production thereof, and an artificial lung using the hollow fiber membrane. More particularly, this invention relates to a porous polypropylene hollow fiber membrane possessing a high gas-exchange capacity, a method for the production thereof, and an artificial lung using the hollow fiber membrane. Still more particularly, this invention relates to a porous polypropylene hollow fiber membrane which, while being used in an artificial lung of the type passing blood inside or the type passing blood outside the hollow fiber membrane, exhibits a high gas-exchange capacity without inflicting damage upon blood components, inducing an increase in the pressure loss, or suffering from leakage of blood plasma during a protracted service, a method for the production thereof, and an artificial lung using the hollow fiber membrane.
This invention also relates to a flat-film type porous polypropylene membrane to be used for blood plasma separation, i.e. separation of blood into blood cells and blood plasma, and for removal of bacteria from blood and a method for the production thereof. More particularly, this invention relates to a flat-film type porous polypropylene membrane which, when used for the blood plasma separation, exhibits a high blood plasma separation speed and has only a sparing possibility of incurring such adverse phenomena as leakage of part of the blood cells in the blood plasma after the blood-plasma separation and hemolysis and a method for the production thereof.


BACKGROUND ART

Generally in the cardiac operation, an artificial lung of hollow fiber membrane is used as inserted in the extra-corporeal circulatory path for the purpose of leading a patient's blood out of his body, adding oxygen to the blood, and removing carbon dioxide gas from the blood. The hollow fiber membranes available in the artificial lungs of this nature come in the two types, namely the homogeneous membrane and the porous membrane. The homogeneous membrane effects passage of a gas by allowing the molecules of the gas to be dissolved and dispersed in the membrane. A typical example of the homogeneous membrane is silicone rubber, which has been commercialized as MERA SILOX (Senko Ika Kogyo K.K.),for instance. Because of the restriction imposed by the gas permeability, silicone rubber is the only practicable homogeneous membrane known to the art. The silicone rubber membrane, by reason of strength, is not allowed to have a wall thickness less than 100 .mu.m. It, therefore, has limited gas permeability and exhibits particularly poor permeability to carbon dioxide gas. Worse still, the silicone rubber has a disadvantage that it is expensive and deficient in workability.
In contrast, the porous membrane is such that the micropores contained in the membrane are notably large as compared with the molecules of a gas given to be passed and, therefore, the gas passes the micropores in the form of volume flow. Various artificial lungs using microporous polypropylene membranes and other similar porous membranes have been proposed. It has been proposed, for example, to manufacture porous polypropylene hollow fibers by melt spinning polypropylene with a nozzle for the production of hollow fibers at a spinning temperature in the range of 210.degree. to 270.degree. C. at a draft ratio in the range of 180 to 600, then subjecting the spun fibers to a first heat treatment at a temperature of not more than 155.degree. C., stretching the hot spun fibers to an extent in the range of 30 to 200% at a temperature below 110.degree. C., and subjecting the stretched fibers to a second heat treatment at a temperature exceeding the temperature of the first heat treatment and not exceeding 155.degree. C. (Japanese Patent Publication SHO 56(1981)-52,123). In the porous hollow fibers obtained as described above, since the micropores are physically f

REFERENCES:
patent: 4405688 (1983-09-01), Lowery et al.
patent: 4708800 (1987-11-01), Ichikawa et al.
patent: 4770852 (1988-09-01), Takahara et al.
patent: 4900444 (1990-02-01), Seita et al.
patent: 4964991 (1990-10-01), Seita et al.

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