Oriented polymeric microporous films

• US 5,176,953 A
• Filed: 08/23/1991
• Issued: 01/05/1993
• Est. Priority Date: 12/21/1990
• Status: Expired due to Term

• Current Assignee: Rkw Se (JM Holding GmbH & Co. KGaA)
• Original Assignee: Amoco Corporation (BP PLC)
• Inventors: Tapp, Willilam T., Clingman, Scott R., Jacoby, Philip, Bauer, Charles W.
• Primary Examiner(s): Lesmes, George F.
• Assistant Examiner(s): RAIMUND, CHRISTOPHER W
• Application Number:
  US07/749,213
• Time in Patent Office: 501 Days
• Field of Search: 521/84.1, 521/90, 521/128, 521/143, 428/308.4, 428/318.4, 428/319.9, 428/315.5, 428/500
• US Class Current: 428/315.5
• CPC Class Codes: C08J 2323/10 Homopolymers or copolymers of propene
• CPC Class Codes: C08J 5/18 Manufacture of films or sheets
• CPC Class Codes: C08L 2205/02 containing two or more polymers of the same C08L -group
• CPC Class Codes: C08L 2205/03 containing three or more polymers in a blend
• CPC Class Codes: C08L 2205/035 containing four or more polymers in a blend
• CPC Class Codes: C08L 2205/242 Beta spherulite nucleating agents
• CPC Class Codes: C08L 23/10 Homopolymers or copolymers of propene
• CPC Class Codes: C08L 23/12 Polypropene
• CPC Class Codes: C08L 23/14 Copolymers of propene C08L23/16 takes precedence
• CPC Class Codes: C08L 23/20 having four to nine carbon atoms
• CPC Class Codes: C08L 2666/02 Organic macromolecular compounds, natural resins, waxes or and bituminous materials
• CPC Class Codes: C08L 2666/04 Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• CPC Class Codes: C08L 2666/24 Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
• CPC Class Codes: C08L 51/06 grafted on to homopolymers or copolymers of aliphatic hydrocarbons containing only one carbon-to-carbon double bond
• CPC Class Codes: C08L 53/00 Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
• CPC Class Codes: Y10T 428/249978 Voids specified as micro
• CPC Class Codes: Y10T 428/249986 Void-containing component contains also a solid fiber or solid particle

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 α-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.

Claims

1. 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/m² /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 α

-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^-1 and 190°

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.

2. The oriented microporous film of claim 1 wherein said polymeric composition comprises:

about 40 to about 90 parts by weight of component A

about 5 to about 40 parts by weight of component B

about 1 to about 10 parts by weight of component C

about 5 to about 30 parts by weight of component D

about 0.1 to 10 ppm by weight of component E

and wherein the beta spherulite nucleating agent comprises a red quinacridone dye having the following structural formula;

##STR3## and wherein the low molecular weight polypropylene has a melt viscosity of about 70 to about 550 poise measured at a shear rate of 136 sec^-1 and 190°

C., and wherein said ethylene-propylene block copolymer has an ethylene content of about 30 to about 40 wt%.

3. 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/m² /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 α

-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^-1 and 190°

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°

to about 135°

C., and

(3) stretching said heated film in at least one direction at a stretch ratio of about 1.5 to about 10.

4. The oriented microporous film of claim 3 wherein said beta-spherulite nucleating agent comprises a red quinacridone dye having the structural formula:

##STR4##

5. The oriented microporous film of claim 4 wherein said ethylene-propylene block copolymer has an ethylene content of about 30 to about 45 wt%.

6. The oriented microporous film of claim 5 having a moisture vapor transmission rate as determined according to ASTM E-96, procedure E, of about 2,500 g/m² /24 hr or greater.