# US 11,439,958 B2 · Porous polytetrafluoroethylene membrane, and waterproof air-permeable membrane and waterproof air-permeable member including the same

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- Number: US 11,439,958 B2
- Document ID: US11439958B2
- Status: Granted
- Kind: B2
- Application number: 16/470,894
- Filed: 2017-12-18
- Published: 2020-03-19
- Granted: 2022-09-13
- Earliest claimed: 2016-12-19
- Assignees: Nitto Denko Corporation
- Applicants: Nitto Denko Corporation
- Inventors: Teppei Tezuka; Youzou Yano; Kazuhiro Omura; Tomoyuki Kasagi
- Web page: https://patentgrep.com/patent/US11439958B2

## CPC

- C08J 5/18: Manufacture of films or sheets
- B01D 53/268: {by diffusion}
- B01D 67/0027: {by stretching}
- B01D 67/0086: {Mechanical after-treatment}
- B01D 69/02: characterised by their properties
- B01D 69/107: {Organic support material}
- B01D 69/108: {Inorganic support material}
- B01D 71/36: Polytetrafluoroethylene
- B29D 99/005: {Producing membranes}
- C08J 3/11: from solid polymers
- C08J 9/228: Forming foamed products
- H05K 5/0215: {with semi-permeable membranes attached to casings}
- B01D 2325/0281: Fibril, or microfibril structures
- B01D 2325/38: Hydrophobic membranes
- B29K 2027/18: PTFE, i.e. polytetrafluoroethylene {, e.g. ePTFE, i.e. expanded polytetrafluoroethylene}
- C08J 2327/18: Homopolymers or copolymers of tetrafluoroethylene
- Y02E 60/10: Energy storage using batteries
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- B29D: PRODUCING PARTICULAR ARTICLES FROM PLASTICS OR FROM SUBSTANCES IN A PLASTIC STATE (making granules B29B9/00; making preforms B29B11/00)
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- B29K: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR {MOULDS, } REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A porous polytetrafluoroethylene (PTFE) membrane of the present disclosure has a water vapor permeability, as measured according to Japanese Industrial Standard (JIS) L 1099 (method B-1), of 150000 g/(m2·day) or more in a thickness direction of the membrane. The porous PTFE membrane of the present disclosure, when attached as a waterproof air-permeable membrane to a housing of an electrical component or electrical device, allows water vapor residing inside the housing to be quickly discharged out of the housing.

## Claims

### Claim 1

A porous polytetrafluoroethylene membrane having a water vapor permeability, as measured according to JIS L 1099 (method B-1), of 150000 g/(m2·day) or more in a thickness direction of the membrane, and having an average tortuosity of 1.5 or less in the thickness direction of the membrane, having an average fibril length of 50 μm or more, having an average node length 5 or more times larger than the average fibril length, and having an average node area ratio of 5% or less.

### Claim 2 (depends on 1)

The porous polytetrafluoroethylene membrane according to claim 1, wherein the average node area ratio is 3% or less.

### Claim 3 (depends on 1)

The porous polytetrafluoroethylene membrane according to claim 1, having a water entry pressure, as measured according to method B (high hydraulic pressure method) of water penetration test specified in JIS L 1092, of 10 kPa or more.

### Claim 4 (depends on 1)

The porous polytetrafluoroethylene membrane according to claim 1, having a porosity of 90% or more.

### Claim 5 (depends on 1)

A waterproof air-permeable membrane comprising the porous polytetrafluoroethylene membrane according to claim 1.

### Claim 6 (depends on 5)

A waterproof air-permeable member comprising the waterproof air-permeable membrane according to claim 5 and a support joined to the waterproof air-permeable membrane.