Oriented polymeric microporous films
AssigneeAmoco Corporation
InventorsPhilip Jacoby, Charles W. Bauer, Scott R. Clingman, Willilam T. Tapp
Life of this patent
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Abstract
Polyolefin resin compositions and oriented microporous films prepared from same comprising an ethylene-propylene block copolymer having an ethylene content of about 10 to about 50 wt %, a propylene homopolymer or random propylene copolymer having up to about 10 wt % of a comonomer of ethylene or an .alpha.-olefin of 4 to 8 carbon atoms, and components selected from a low molecular weight polypropylene, a beta-spherulite nucleating agent and an inorganic filler, and to processes for forming such films wherein the microporous films have improved breathability, strength, toughness and break elongation.
Claims6
A polymeric composition in the form of an oriented microporous film having microvoid cells and interconnecting pores between the cells and a moisture vapor transmission rate as determined according to ASTM E-96, procedure E, of about 500 g/m.sup.2 /24 hr or greater wherein the polymeric composition comprises:
- about 5 to about 95 parts by weight of a component A comprising an ethylene-propylene block copolymer having an ethylene content of about 10 to about 50 wt%,
- about 95 to about 5 parts by weight of a component B comprising a propylene homopolymer or random copolymer having up to about 10 wt% of a comonomer of ethylene of an .alpha.-olefin of 4 to 8 carbon atoms,
- 0 to about 20 parts by weight, per 100 parts by weight of components A and B, of a component C comprising a low molecular weight polypropylene having a melt viscosity of about 50 to about 1,000 poise measured at a shear rate of 136 sec.sup.-1 and 190.degree. C.,
- 0 to about 30 parts by weight, per 100 parts by weight of components A and B, of a component D comprising calcium carbonate, and
- 0 to about 50 ppm, per 100 parts by weight of components A and B, of a component E comprising a beta-spherulite nucleating agent with the proviso that when the weight ratio of component A/component B is about 5-30/95-70, component E is present at 0.1 to about 10 ppm, and that
- when the weight ratio of component A/component B is about 30-95/70-5, component C is present at
- (a) about 5 to about 20 parts by weight when the polymeric composition is substantially free of component D or of components D and E, and
- (b) about 1 to about 10 parts by weight when the polymeric composition has about 0.1 to about 10 ppm of component E and about 5 to about 30 parts by weight of component D.
An oriented microporous film having microvoid cells and interconnecting pores between the cells and a moisture vapor transmission rate as determined according to ASTM E-96, procedure E, of about 500 g/m.sup.2 /24 hr or greater prepared by a process comprising the steps of:
- (1) forming a film from a polymeric composition comprising
- about 40 to about 90 parts by weight of a component A comprising an ethylene-propylene block copolymer having an ethylene content of about 10 to about 50 wt%,
- about 5 to about 40 parts by weight of a component B comprising a propylene homopolymer or random copolymer of propylene having up to about 10 wt% of a comonomer of ethylene or an .alpha.-olefin of 4 to 8 carbon atoms,
- about 1 to about 20 parts by weight of a component C comprising a low molecular weight polypropylene having a melt viscosity of about 50 to about 1,000 poise measured at a shear rate of 136 sec.sup.-1 and 190.degree. C.,
- 0 to about 30 parts by weight, per 100 parts by weight of components A, B and C, of a component D comprising calcium carbonate, and
- 0 to about 50 ppm, per 100 parts by weight of components A, B and C, of a component E comprising a beta-spherulite nucleating agent with the proviso that component C is present at
- (a) about 5 to about 20 parts by weight when the polymeric composition is substantially free of component D or of components D and E, and
- (b) about 1 to about 10 parts by weight when the polymeric composition has about 0.1 to about 10 ppm of component E and about 5 to about 30 parts by weight of component D,
- (2) heating said film at a temperature of about 35.degree. to about 135.degree. C., and
- (3) stretching said heated film in at least one direction at a stretch ratio of about 1.5 to about 10.
Dependencies are inferred from the claim text.