Method of producing highly permeable microporous polyolefin membrane
US6153133A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 23, 1999 |
| Grant date | Nov 28, 2000 |
| Priority date | — |
| Expiry date | Jun 23, 2019 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB29K2995/0065
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
A method for producing a highly permeable microporous polyolefin membrane including the steps of preparing a polyolefin solution containing 5-40 weight % of a polyolefin or a polyolefin composition and 95-60 weight % of a solvent, the polyolefin having a weight-average molecular weight of not less than 3.times.10.sup.5 and less than 1.times.10.sup.6 and a weight-average molecular weight/number-average molecular weight of 5-300, and the polyolefin composition having a weight-average molecular weight of not less than 3.times.10.sup.5 and less than 1.times.10.sup.6 and a weight-average molecular weight/number-average molecular weight of 5-300 as a whole, extruding the polyolefin solution, stretching the extrudate uniaxially at a draft ratio of 3-50 in a molten state, cooling the stretched extrudate to solidify to a gel-like sheet, removing residual solvent, drying the resultant sheet, and heat-setting at a temperature of 80.degree. C. or higher and its melting point or lower. A polyolefin or its composition is uniaxially stretched before it is cooled to a gel-like sheet. Uniaxial stretching of a viscous polyolefin solution allows micropores to have a large average diameter, thereby im…
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