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:
Jan. 20, 2009
Filed:
Aug. 28, 2003
Hidehiko Funaoka, Tokyo, JP;
Kotaro Takita, Yokohama, JP;
Norimitsu Kaimai, Kanagawa, JP;
Shigeaki Kobayashi, Kanagawa, JP;
Koichi Kono, Saitama, JP;
Hidehiko Funaoka, Tokyo, JP;
Kotaro Takita, Yokohama, JP;
Norimitsu Kaimai, Kanagawa, JP;
Shigeaki Kobayashi, Kanagawa, JP;
Koichi Kono, Saitama, JP;
Tonen Chemical Corporation, Tokyo, JP;
Abstract
The present invention provides a microporous polyolefin membrane of high permeability and novel structure, and also provides a method of producing the same, wherein its average pore size is gradually decreases from at least one membrane surface towards its center. The method of producing the microporous polyolefin membrane comprises the steps of extruding the solution, composed of 10 to 50 weight % of (A) a polyolefin having a weight-average molecular weight of 5×105 or more or (B) a composition containing this polyolefin and 50 to 90 weight % of a solvent, into a gel-like formed article and removing the solvent therefrom, wherein a treatment step with a hot solvent is incorporated.