초록 ▼

This invention relates to oriented porous films having cells with polygonal cross sections and average pore diameters of about 5 to about 30 microns and interconnecting pores between the cells which have a diameter of about 0.2 to about 20 microns which are formed from a polypropylene-based resin an

This invention relates to oriented porous films having cells with polygonal cross sections and average pore diameters of about 5 to about 30 microns and interconnecting pores between the cells which have a diameter of about 0.2 to about 20 microns which are formed from a polypropylene-based resin and a process for forming the film which comprises the steps of forming a film containing beta-spherulites, selectively extracting a portion of the beta-spherulites to form a porous film and stretching the porous film in at least one direction to form the oriented polymeric porous film.

대표청구항 ▼

An oriented polymeric porous film with polygonal cells having average diameters of about 5 to about 30 microns and interconnecting pores between the cells having average diameters of about 0.2 to about 20 microns prepared from a polypropylene-based resin having at least 40% crystallinity by a proces

An oriented polymeric porous film with polygonal cells having average diameters of about 5 to about 30 microns and interconnecting pores between the cells having average diameters of about 0.2 to about 20 microns prepared from a polypropylene-based resin having at least 40% crystallinity by a process comprising the steps of: (a) dispersing in said polypropylene-based resin a nucleating agent capable of producing beta-spherulites; (b) extruding the nucleating agent-containing polypropylene-based resin into a film; (c) cooling said film below the crystallization temperature of said polypropylene-based resin to form at least 20 weight percent of beta-spherulites in the film; (d) extracting selectively said beta-spherulites in an amount corresponding to at least 15 weight percent of the polypropylene-based resin from the cooled film with an extraction solvent to form a porous film; and (e) orienting the porous film by heating the porous film at a temperature of about 115°to about 135°C. for a time period of about 2 to about 20 seconds and stretching the heated porous film in at least one direction at a stretch ratio of about 1.5 to about 7.5 to form said oriented polymeric porous film.