Process for the production of polytetrafluoroethylene porous mem

Details Process for the production of polytetrafluoroethylene porous mem Process for the production of polytetrafluoroethylene porous mem

1986-05-15

1987-12-01

Lowe, James

Plastic and nonmetallic article shaping or treating: processes

Pore forming in situ

264127, 264158, 2642888, B29C 5504, B29C 5512, B29C 6720

Patent

active

047103310

ABSTRACT:
A process for the production of PTFE porous membranes is provided wherein a PTFE preform is prepared by compression molding a PTFE molding powder of 1-90 .mu.m obtained by suspension polymerization of tetrafluoroethylene, the preform is sintered at a temperature above 327.degree. C., followed by skiving the heated preform into a film form. The thus-obtained film is heat treated at a temperature above 327.degree. C., the heat treated film is slowly cooled at a cooling rate of less than 70.degree. C./hr so as to adjust the crystallinity of PTFE in the sintered film to 60-75% and the film is stretched either uniaxially or biaxially to 1.3 to 6.5 times while heating at a temperature of 100.degree.-320.degree. C.

REFERENCES:
patent: 2642625 (1953-06-01), Peck
patent: 2781552 (1957-02-01), Gray
patent: 2819209 (1958-01-01), Pall et al.
patent: 3152082 (1964-10-01), Davis et al.
patent: 4110392 (1978-08-01), Yamazaki

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