Solvent stretching procedures for the production of open-cell mikroporoesen from a polymer films which are not - porous polymeric film of a crystalline polymer

摘要

Microporous films having improved morphological structure are prepared by the "solvent stretch" method from an olefinic precursor film having a controlled crystalline structure. The crystalline structure of the precursor film is controlled by preparing said film from an olefinic crystalline homopolymer characterized as having a melt index of about 3 to about 20 in the absence of a nucleating agent and a molecular weight distribution ratio of about 3.8 to about 13. In another embodiment the crystalline structure of the precursor film is controlled by incorporating a nucleating agent into the crystalline polymer resin from which the precursor film is prepared which thereby permits a reduction in the melt index of the polymer to about 0.3.