Claims
- 1. A method of making a microporous polyolefin membrane for use as a battery separator having a thickness ranging from about 0.33 mils to about 0.5 mils comprising the steps of:
- extruding a parison;
- collapsing the parison onto itself to form a flat sheet comprising two plies;
- annealing the flat sheet;
- stretching the flat sheet; and
- winding up the flat sheet, and adhesion force between the two plies being less than 8 grams per inch.
- 2. The method according to claim 1 wherein stretching comprises stretching in at least 2 steps, one a cold stretch step, and the other, a hot stretch step.
RELATED APPLICATIONS
This application is a divisional of U.S. application Ser. No. 08/896,513 filed Jun. 22, 1997 which was a continuation of U.S. application Ser. No. 08/650,210 filed May 20, 1996, now U.S. Pat. No. 5,691,077, which was a continuation of U.S. application Ser. No. 08/359,772 filed Dec. 20, 1994, now abandoned.
US Referenced Citations (9)
Non-Patent Literature Citations (1)
Entry |
"Characterization of Microporous Membrane Separators", Mar. 1-4, 1993 delivered at the Tenth International Seminar on Primary and Secondry Battery Technology and Application Coordinated by: Florida Educational Seminars, Inc. 2836 Banyan Blvd. Circle NW, Boca Raton, FL 33431. |
Divisions (1)
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Number |
Date |
Country |
Parent |
896513 |
Jun 1997 |
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Continuations (2)
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Number |
Date |
Country |
Parent |
650210 |
May 1996 |
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Parent |
359772 |
Dec 1994 |
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