Stretched porous polytetrafluoroethylene membrane, air-permeable medium using the same, and filter member using the same

Patent metadata

Field	Value
Publication number	US-12397250-B2
Application number	US-202017781905-A
Country	US
Kind code	B2
Filing date	Dec 3, 2020
Priority date	Dec 5, 2019
Publication date	Aug 26, 2025
Grant date	Aug 26, 2025

Abstract

A provided stretched porous polytetrafluoroethylene membrane has an air permeability of 4 cm 3 /(sec·cm 2 ) or more, as expressed in terms of Frazier air permeability, in a thickness direction, and has a total cohesion of 1.9 (N/20 mm) 2 or more, the total cohesion being expressed by a product of a peel cohesion in a first in-plane direction and a peel cohesion in a second in-plane direction perpendicular to the first direction. The above stretched porous membrane is highly air-permeable and, for example, when included in a filter member, being less likely to suffer breakage at the time of handling the member or placing the member on a housing or the like.

First claim

The invention claimed is:

1. A stretched porous polytetrafluoroethylene membrane,
having an air permeability of 4 cm 3 /(sec·cm 2 ) or more, as expressed in terms of Frazier air permeability, in a thickness direction, and
having a total cohesion of 1.9 (N/20 mm) 2 or more, the total cohesion being expressed by a product of a peel cohesion in a first in-plane direction and a peel cohesion in a second in-plane direction perpendicular to the first direction.

2. The stretched porous polytetrafluoroethylene membrane according to claim 1 , having a mass per unit area of 7.0 g/m 2 or more.

3. The stretched porous polytetrafluoroethylene membrane according to claim 1 , having a thickness of 30 μm or more.

4. An air-permeable medium,
having air permeability in a thickness direction,
preventing a foreign matter from passing therethrough in the thickness direction, and
comprising the stretched porous polytetrafluoroethylene membrane according to claim 1 .

5. The air-permeable medium according to claim 4 , further comprising an air-permeable supporting member laminated on the stretched porous polytetrafluoroethylene membrane.

6. A filter member comprising
an air-permeable medium having air permeability in a thickness direction and preventing a foreign matter from passing therethrough in the thickness direction, wherein
the air-permeable medium is the air-permeable medium according to claim 4 .

7. The stretched porous polytetrafluoroethylene membrane according to claim 1 ,
wherein the stretched porous polytetrafluoroethylene membrane satisfies an inequality: C T ≥−0.33× P T +3.67, wherein C T is the total cohesion and P T is the air permeability.

Assignees

• Nitto Denko Corp

Inventors

• Takamura Yuichi
• Kigami Hiroki
• KUROGI Eisuke
• Ueda Kodai

Classifications

• C08J2327/18

  Homopolymers or copolymers of tetrafluoroethylene · CPC title

• C08J9/28

  by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum · CPC title

• B01D2239/1291

  Other parameters · CPC title

• B01D2239/1258

  Permeability · CPC title

• B01D46/543

  using membranes · CPC title