Fine porous membrane and process for producing the same

Details Fine porous membrane and process for producing the same Fine porous membrane and process for producing the same

1987-12-02

1989-06-20

Sever, Frank

Liquid purification or separation

Filter

Material

528171, B01D 1300

Patent

active

048407330

ABSTRACT:
A fine porous membrane having a pore size distribution in the thickness direction and having a layer having a minimum pore size in the interior thereof, wherein the ratio of maximum pore size to the average pore size, each as determined according to ASTM-316-80, is not more than 1.8. The fine porous membrane is produced by a process comprising casting a film-forming solution, comprising a polymer in a solvent having incorporated therein a swelling agent and a non-solvent, on a casting carrier while being in a solution state, directing air having a temperature of from 15.degree. to 60.degree. C. and a relative humidity of from 10 to 80% onto the surface of the cast film at a velocity of from 0.2 to 4 m/sec for a period of from 2 to 17 seconds to cause coacervation of the cast film while controlling the evaporation loss of the solvent from the cast film and the absorption of non-solvent vapors in the air, dipping the case film in a coagulating bath to cause phase separation and coagulation to form a fine porous membrane, and stripping off the membrane from the casting carrier. The fine porous membranes has a low filtration resistance, a great filtration flow rate, a high efficiency in trapping fine particles and bacteria, and a long life.

REFERENCES:
patent: 4085090 (1978-04-01), Hara et al.
patent: 4229297 (1980-10-01), Nohmi et al.

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