Process for producing fluorocarbon membranes and membrane produc

Details Process for producing fluorocarbon membranes and membrane produc Process for producing fluorocarbon membranes and membrane produc

1990-08-17

1991-07-16

Foelak, Morton

Liquid purification or separation

Filter

Material

21050023, 521 61, 521 64, 521134, B01D 7132

Patent

active

050322745

ABSTRACT:
Microporous or open ultrafiltration poly (tetrafluoroethylene-co-perfluoro-(alkyl vinyl ether)) (PFA) or poly (tetrafluoroethylene-co-hexafluoropropylene) (FEP) film membrane or hollow fibers having open pores are formed from a melt blend of 10 to 35 weight percent of the PFA or FEP and a chlorotrifluoroethylene oligomer solvent. The melt blend is shaped and one or more surfaces of the shaped melt blend are coated with the solvent prior to phase separation of the melt blend. Coating the membrane with solvent during shaping results in membrane having larger pores on that membrane surface as compared to membranes not coated with solvent. The shaped melt blend is cooled to effect phase separation and crystallization of the PFA or FEP from the blend. The solvent is separated from the PFA or FEP by extraction and the porous PFA or FEP is heat set under restraint to prevent shrinkage. In one embodiment of this invention the dry film membrane recovered after extraction or the membrane wet with extraction liquid is stretched in the cross-web direction to below its breaking limit, dried restrained and then heat-set.

REFERENCES:
patent: 2915483 (1959-12-01), Barnhart
patent: 3379658 (1968-04-01), Kemper
patent: 3518332 (1970-06-01), Sklarchuk et al.
patent: 3536796 (1970-10-01), Rock
patent: 4181983 (1980-01-01), Kulkarni
patent: 4623670 (1986-11-01), Mutoh et al.
patent: 4702836 (1987-10-01), Mutoh et al.

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