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. 05, 2018
Filed:
Oct. 07, 2015
Asahi Kasei E-materials Corporation, Tokyo, JP;
Miyuki Itou, Tokyo, JP;
Asahi Kasei E-materials Corporation, Tokyo, JP;
Abstract
A method for producing a polyolefin-based porous film includes an (A) step: a raw fabric forming step for forming a non-porous raw fabric from a polyolefin-based resin composition, a (B) step: an MD cold stretching step for cold stretching the non-porous raw fabric obtained in the (A) step at a temperature of −20° C. to (Tm−30)° C. (Tm is a melting point (° C.) of the non-porous raw fabric) in an extruding direction (MD) of the raw fabric to make the raw fabric porous; a (D) step: a TD cold stretching step for cold stretching a film processed in the (B) step in a direction (TD) perpendicular to the MD, and an (H) step: a thermal fixing step, in the above order. A thermal fixing temperature T(° C.) in the (H) step satisfies expressions (1) and (2) below; T>T(1), (Tm−3)≥T≥(Tm−40) (2) (in the expressions, Trepresents a stretching temperature (° C.) in the (D) step, and Tm represents the melting point (° C.) of the non-porous raw fabric). A polyolefin-based porous film made of a polyolefin-based resin composition has a pore surface area of 35.0 to 42.0 m/g and birefringence of 2.0×10to 4.0×10.