Microporous film battery separator
The microporous film described has a matrix comprising 40 to 90 vol. % of a polyolefin having a number average molecular weight of 15,000 or more and 10 to 60 vol. % of an inorganic filler, said matrix having therein void spaces at a rate of 30 to 75 vol. % based on the volume of the film; and 2 to 20 wt % based on the total weight of the polyolefin and the inorganic filler, of an organic substance which is substantially insoluble in and inert to sulfuric acid and has a solubility parameter ranging from 7.3 inclusive to 8.4 exclusive; said organic substance, in its majority, adhering to the overall surface of the film including the outer surfaces of the film and the surfaces of the polyolefin walls defining said void spaces in cooperation with said inorganic filler; said microporous film being prepared by a method comprising blending said polyolefin, said inorganic filler, and an organic liquid having a solubility parameter ranging from 4 to 9.9 inclusive in amounts of 10 to 60 vol. %, 7 to 42 vol. % and 30 to 75 vol. %, respectively, based on the whole volume of the polyolefin-filler-organic liquid composition, the amount of the polyolefin being 2/3 to 9 multiple of the amount of the inorganic filler; subjecting the resulting blend to molding to form a film; extracting from said film the organic liquid to form a matrix which comprises 40 to 90 vol. % of the polyolefin and 10 to 60 vol. % of the inorganic filler and having therein void spaces at a rate of 30 to 75 vol. % based on the volume of the film; and applying to the matrix the organic substance which is substantially insoluble in and inert to sulfuric acid and has a solubility parameter ranging from 7.3 inclusive to 8.4 exclusive so that said organic substance adheres to the overall surface of the film in an amount of 2 to 20 wt % based on the total weight of the polyolefin and the inorganic filler.
- Assignee:
- Asahi Kasei Kogyo K K (Japan)
- Patent Number(s):
- US 4210709
- OSTI ID:
- 5142200
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
250903* -- Energy Storage-- Batteries-- Materials
Components
& Auxiliaries
ANTIOXIDANTS
BATTERY SEPARATORS
CHEMICAL PREPARATION
FILLERS
FILMS
MATERIALS
MATRIX MATERIALS
MECHANICAL PROPERTIES
ORGANIC COMPOUNDS
ORGANIC POLYMERS
POLYMERS
POLYOLEFINS
POROUS MATERIALS
SYNTHESIS
WEAR RESISTANCE