Asymmetric porous film materials and process for producing same

Details Asymmetric porous film materials and process for producing same Asymmetric porous film materials and process for producing same

1977-09-02

1981-02-03

Ansher, Harold

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

210510, 2105002, 2642108, 2642888, 428227, 428305, 428317, 428422, B32B 2702, B01D 1304, D01D 512, B29D 2700

Patent

active

042489245

ABSTRACT:
Porous film materials composed of polytetrafluoroethylene having an asymmetric structure are produced by stretching the film using a pair of revolving rolls which are heated to a temperature lower than the melting point of the film. Stretching is produced by revolving the two rolls at different speed which also tends to produce a compressive force in the thickness of the film. The rolls are heated to different temperatures to produce a temperature difference of preferably 50.degree. C. or more. The combination of the compressive force and the temperature gradient in the thickness of the film is believed to produce the asymmetric structure in the resulting porous film materials which are characterized by a fiber structure in the front surface which is different from that in the back surface.

REFERENCES:
patent: Re27026 (1971-01-01), Alfrey et al.
patent: 3331772 (1967-07-01), Brownscombe et al.
patent: 3630800 (1971-12-01), Nash
patent: 3764363 (1973-10-01), Civardi et al.
patent: 3933653 (1976-01-01), Hashino et al.
patent: 4082893 (1978-04-01), Okita
patent: 4096227 (1978-06-01), Gore
patent: 4116892 (1978-09-01), Schwarz

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