The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 20, 1989
Filed:
Dec. 02, 1987
Jun Sasaki, Kanagawa, JP;
Atsushi Adachi, Kanagawa, JP;
Kyoichi Naruo, Kanagawa, JP;
Yukio Shinagawa, Kanagawa, JP;
Sumio Ohtani, Kanagawa, JP;
Fuji Photo Film Co., Ltd., Kanagawa, JP;
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.