Asahi Kasei Kogyo Kabushiki Kaisha

Shigeo Kaneko

Yoshinao Doi

Takeo Hanamura

Osamu Fujii

Katsumi Yoshitake

Osamu Fugii

Tetsuhiko Hirata

Yasuhiro Tanabe

This invention is directed to a microporous film comprising a 40 to 90 volume percent polyolefin having a number average molecular weight of 15,000 or more and a weight average molecular weight of less than 300,000 and a 10 to 60 volume percent inorganic filler and having a void space rate or porosity of 30 to 75 volume percent based on the volume of the film. The microporous film of such specific composition and structure has a desired wettability and a much reduced electrical resistance. Said resistance being as low as 0.0006 .OMEGA.dm.sup.2 /sheet. Said film has sufficient flexibility and mechanical strength to make it useful in wide variety of applications, especially as separators in batteries or electrolytical apparatuses etc. Such microporous material is prepared by: (a) blending a specified polyolefin, an inorganic filler and an organic liquid in amounts of 10 to 60 volume percent, 6 to 35 volume percent and 30 to 75 volume percent, respectively, based on the total volume of the blend, the amount of the polyolefin being 2/3 to 9 times the amount of the inorganic filler; (b) molding the blend to form a film; and (c) extracting said organic liquid from the molded film.

Microporous film, particularly battery separator, and method of making

A microporous film which comprises a matrix comprising 40 to 90 volume percent of a polyolefin having a number average molecular weight of 15,000 or more and 10 to 60 volume percent of an inorganic filler, said matrix having therein void spaces at a rate of 30 to 75 volume percent based on the volume of the film; and 2 to 20 weight percent, based on the total weight of the polyolefin and the inorganic filler, of an organic substance which is substantially insoluble in and inert to sulfuric acid and has a solubility parameter ranging from 7.3 inclusive to 8.4 exclusive; said organic substance, in its majority, adhering to the overall surface of the film including the outer surfaces of the film and the surfaces of the polyolefin walls defining said void spaces in cooperation with said inorganic filler.

Method for manufacturing a microporous film having low electrical

Microporous film battery separator

Growing community of inventors

Tokyo, Japan

Shigeo Kaneko