Asahi Kasei Kogyo Kabushiki Kaisha

Asahi Kasei Kogyo

Yoshinao Doi

Shigeo Kaneko

Takeo Hanamura

Mitsuo Kohno

Osamu Fujii

Katsumi Yoshitake

Takashi Nohmi

Kazuo Matsuda

Takao Yamada

Haruo Matsumura

Tetsuhiko Hirata

Yasuhiro Tanabe

Osamu Fugii

A porous membrane comprising a polyvinylidene fluoride resin and having a uniform, three-dimensional, network pore structure. The membrane has excellent chemical resistance, excellent filtering characteristics and excellent mechanical properties. The porous membrane can be produced by blending a polyvinylidene fluoride resin, an organic liquid and a powdery hydrophobic silica, subjecting the resultant blend to melt-molding to form a membrane, and extracting the organic liquid and the hydrophobic silica from the melt-molded membrane.

Polyvinylidene fluoride porous membrane and a method for producing the

A sulfonated polyolefin porous membrane containing sulfonic groups in an amount, in terms of exchange capacity, of 0.05 to 1 milliequivalent per gram of the sulfonated polyolefin and having a porosity of 30 to 85% and an average pore diameter of 0.05 to 1.mu. has been found to be excellent in water permeability, removal capability, water-permeability retention, mechanical strength and elongation, etc. The porous membrane of the present invention may advantageously be employed as a fine microfilter or the like. The porous membrane of the present invention may be easily prepared by treating with a sulfonating agent a polyolefin porous membrane preferably containing an inorganic filler which is subsequently extracted from the membrane.

Hydrophilic sulfonated polyolefin porous membrane and process for

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

A specific porous membrane is found to be extremely useful for permeation-separation of an oil from an oil-containing emulsion. By contacting a stable oil-containing emulsion of either water-in-oil type or oil-in-water type with the surface of a specific porous membrane having at its surface a critical surface tension of less than 35 dynes/cm to not less than 20 dynes/cm and having an average pore diameter of 0.03 .mu.m to 5 .mu.m, a pore radius distribution of not more than 1.5 and a porosity of 1 to 85%, only the oil can be permeation-separated, without permeation of the liquid immiscible with the oil, with high selectivity and high oil permeation.

Method of separating oil from oil-containing liquid

Microporous film battery separator

An alkaline battery separator made of a porous film which consists substantially of a polyolefin having a weight average molecular weight of less than 300,000 and a number average molecular weight of 15,000 or more and which has a thickness of 0.025 to 1 mm, a porosity of 50 to 80%, an average pore diameter of 0.05 to 0.5.mu. and an average ratio of the larger dimension to the smaller dimension of the pore opening of not more than 2. The alkaline battery separator has not only an extremely low electrical resistance and a high alkali resistance but also a transmission-inhibitive ability for the active materials of battery and is excellent in mechanical strength and flexibility. It does not show appreciable shrinkage by heat. For producing such an alkaline battery separator, 10 to 50 volume percent of a polyolefin, 7 to 42 volume percent of an inorganic filler and 30 to 75 volume percent of an organic liquid having a solubility parameter of from 8.6 to 9.9 inclusive are blended, the amount of the polyolefin being 2/3 to 9 multiple of the amount of the inorganic filler, and the resulting blend is subjected to melt-molding to form a film, followed by extraction of the organic liquid and the inorganic filler from the film. In the extraction of the organic liquid and the inorganic filler, the film does not undergo shrinkage to provide a separator having excellent characteristics.

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Kawasaki, Japan

Yoshinao Doi