Process for preparing a microporous polymer film

Details Process for preparing a microporous polymer film Process for preparing a microporous polymer film

1975-09-08

1979-02-06

Lowe, James B.

Plastic and nonmetallic article shaping or treating: processes

With severing, removing material from preform mechanically,...

Making hole or aperture in article

264288, 264342RE, 264DIG47, B29C 1702, B29D 724, B29D 2700

Patent

active

041384598

ABSTRACT:
A process for the preparation of an open-celled microporous, polymer film. The improved process comprises the heat relaxing of a microporous polymer film which is formed from a non-porous, crystalline, elastic polymer film which has been uniaxially cold stretched at a temperature in the range of between about -20.degree. C. and a temperature 25.degree. C. below the crystalline melting temperature of the polymer film, followed by hot stretching, in the same direction, the cold-stretched film at a temperature in the range of between about 25.degree. C. below the crystalline melting temperature of the polymer film and 5.degree. C. below the crystalline melting temperature of the polymer film. The heat relaxing step comprises exposing the film under tension to a temperature in the range of between about 40.degree. C. below the crystalline melting temperature of the polymer film and 5.degree. C. below the crystalline melting temperature of the polymer film, such that the maximum dimension in the direction of stretch, of the cold and hot stretched microporous film is reduced.

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patent: 3843761 (1974-10-01), Bierenbaum et al.
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