Polyolefin porous film, method for producing the same and apparatus for producing the same

Patent metadata

Field	Value
Publication number	US-9546253-B2
Application number	US-201113075519-A
Country	US
Kind code	B2
Filing date	Mar 30, 2011
Priority date	Aug 5, 2010
Publication date	Jan 17, 2017
Grant date	Jan 17, 2017

Abstract

The present invention relates to a method for producing a polyolefin porous film, the method including the steps of: (a) melt-kneading a solution containing a polyolefin having a weight average molecular weight of 500,000 or more and a solvent to obtain a kneaded product; (b) extruding and cooling the kneaded product to obtain a gel-like molded product; (c) drawing the gel-like molded product to obtain a drawn sheet; (d) removing the solvent from the drawn sheet, followed by drying to obtain a film in which fine pores are formed; (e) conducting heat treatment, while fixing the film in both directions of a MD and a TD thereof and drawing the film at a draw ratio of exceeding 0% to less than 0.1% in at least one direction of the MD and the TD thereof; and (f) conducting heat treatment while decreasing a width of the film in at least one direction of the MD and the TD of the film.

First claim

What is claimed is:

1. A method for producing a polyolefin porous film, said method comprising the steps of:
(a) melt-kneading a solution consisting of an ultrahigh molecular weight polyethylene having a weight average molecular weight of 500,000 or more, a solvent and an antioxidant to obtain a kneaded product;
(b) extruding and cooling the kneaded product to obtain a gel molded product;
(c) drawing the gel molded product to obtain a drawn sheet;
(d) removing the solvent from the drawn sheet, followed by drying to obtain a film in which fine pores are formed;
(e) conducting heat treatment, while fixing the film in both directions of a MD and a TD thereof and drawing the film at a draw ratio of exceeding 0% up to 0.05% in at least one direction of the MD and the TD thereof; and
(f) conducting heat treatment while decreasing a width of the film in at least one direction of the MD and the TD of the film,
wherein the polyolefin porous film has an air permeability of 280 sec/100 cc·20 μm or less.

2. The method for producing a polyolefin porous film according to claim 1 , wherein the solution substantially consists of ultrahigh molecular weight polyethylene having a weight average molecular weight of 500,000 or more and the solvent.

3. The method for producing a polyolefin porous film according to claim 1 , wherein a polymer-type hindered phenol-based antioxidant is added to the solvent in the step (a).

Assignees

• Noumi Shunsuke
• Tadokoro Kouji
• Kondou Yoshihiko
• Kawamura Masatoshi
• Nitto Denko Corp

Inventors

• Noumi Shunsuke
• Tadokoro Kouji
• Kondou Yoshihiko
• Kawamura Masatoshi

Classifications

• C08J2323/06

  Polyethene · CPC title

• B29K2105/04

  cellular or porous · CPC title

• B29K2023/0683

  UHMWPE, i.e. ultra high molecular weight polyethylene · CPC title

• B29C55/143

  firstly parallel to the direction of feed and then transversely thereto · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title