Porous polymeric films
AssigneeStandard Oil Company (Indiana)
InventorPhilip Jacoby
Life of this patent
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Abstract
This invention relates to porous films having pores with polygonal cross sections and average pore diameters of about 3 to about 100 microns and the method for preparing these films. More particularly this invention relates to a porous film having pores with polygonal cross sections and average pore diameters of about 3 to about 100 microns formed from a resinous polymer of propylene and the process for forming the film which comprises the steps of (a) forming a film containing beta-spherulites and (b) selectively extracting the beta-spherulites.
Claims7
A porous film with a thickness of about 0.010 to about 0.25 millimeters comprising a resinous polymer of propylene having alpha-form spherulites and polygonal pores with average diameters of about 3 to about 100 microns said pores corresponding to the location of beta-form spherulites.
A porous film having polygonal pores with average pore diameters from about 3 to about 100 microns said film prepared from resinous polymers of propylene capable of having at least 40% crystallinity by a process comprising the steps of
- (a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;
- (b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);
- (c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites;
- and
- (d) selectively extracting said beta-spherulites from the cooled film product of step (c) with an extracting solvent to form the porous film product.
A process for preparing a porous film having polygonal pores with average pore diameters from about 3 to about 100 microns from resinous polymers of propylene capable of having at least 40% crystallinity said process comprising the steps of
- (a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;
- (b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);
- (c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites;
- and
- (d) selectively extracting said beta-spherulites from the cooled film product of step (c) with an extracting solvent to form the porous film product.
A process for preparing a porous film from resinous polymers of propylene capable of having at least 40% crystallinity said process comprising the steps of
- (a) dispersing in said resinous polymer a nucleating agent capable of producing beta-spherulites;
- (b) forming by extrusion a film with a thickness of about 0.010 to about 0.25 millimeters from the molten product of step (a);
- (c) cooling said film below the crystallization temperature of said polymer to form beta-spherulites;
- and
- (d) contacting the film of step (c) with an extracting solvent at a temperature of about 95.degree. C. to about 100.degree. C. to selectively extract at least a portion of said beta-spherulites to form the porous film having polygonal pores with average pore diameters from about 3 to about 100 microns.
Dependencies are inferred from the claim text.