Plastic and nonmetallic article shaping or treating: processes – Pore forming in situ – By treating occluded solids
Patent
1989-06-13
1993-03-30
Dawson, Robert A.
Plastic and nonmetallic article shaping or treating: processes
Pore forming in situ
By treating occluded solids
264 41, 264 461, B29C 6720
Patent
active
051981629
ABSTRACT:
A microporous polymeric film of high porosity comprises a halopolymer in which the repeating units are --(C.sub.n H.sub.2n)-- and --(C.sub.m X.sub.2m)-- in which each X independently represents fluorine or chlorine and the values of n and m are greater than one and less than six. The film is the result of firstly melt processing a mixture of the halopolymer, more than 150 parts by weight of an extractable salt and not more than 80 parts by weight of an extractable polymer per 100 parts by weight of the halopolymer, the extractable polymer not being completely and homogeneously mixed with the halopolymer and being less viscous than the halopolymer when both are molten so that the surfaces of the film resulting from melt processing are rich in the extractible polymer, and secondly extracting at least some of the extractable salt to render the film porous and extracting at least some of said polymer to impart surface porosity to the film. The film has a porosity of more than 50% by volume and more usually 60-70%. The film may be used as the separator of an electrochemical cell e.g. a battery having a lithium anode and a thionyl chloride electrolyte.
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Barker David J.
Cook John A.
Dorling Mike G. L.
McLoughlin Robert H.
Park George B.
Dawson Robert A.
Kuhns Allan R.
Scimat Limited
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