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US 6,444,302 B1Granted
Breathable films and method for making
AssigneeExxonMobil Chemical Patents Inc.
InventorsSrivatsan Watson Srinivas, Patrick Brant, Francois Henri Chambon, James Peter Stokes
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Abstract
The present invention relates to a cold-drawn breathable film formed from a blend of a soft polymer component and a hard polymer component. The soft polymer component (SPC) is a copolymer of a major olefinic monomer and a minor olefinic monomer. The major olefinic monomer is either ethylene or propylene and forms the majority of the SPC. Preferred films after cold-drawing exhibit a water vapor transmission rate (WVTR) of at least 100 g-mil/m2-day.
Claims28
A cold-drawn film comprising a blend of
- a) a semi-crystalline copolymer component of a major olefinic monomer and a minor olefinic monomer having a melting point greater than 25° C. and a flexural modulus less than 100 MPa, wherein said major olefinic monomer is ethylene or propylene and said minor olefinic monomer is different from said major olefinic monomer and is selected from the group consisting of linear, branched, or ring-containing C2 to C30 olefins, capable of insertion polymerization, and combinations thereof, and
- b) a polystyrene component having a flexural modulus greater than 200 MPa,
- wherein said copolymer is present in said film as a continuous phase and said film has a tensile modulus of less than 160 MPa.
A cold-drawn film comprising a blend of
- a) a first polymer component selected from
- i) one or more thermoplastic copolymers each comprising between 49 and 90 mole % propylene and at least one of ethylene or a C4 to C20 α-olefin, said thermoplastic copolymer having a melting point of 25° C. or more, an MWD of from 1.5 to 4.0, crystallinity of from 5 to 40 weight %, and a flexural modulus less than 100 MPa,
- ii) one or more thermoplastic copolymers each comprising between 84 and 98 mole % ethylene and at least one C3 to C20 α-olefin, said thermoplastic copolymer having a melting point of 25° C. or more, an MWD of from 1.5 to 4.0, a narrow compositional distribution, and a flexural modulus less than 100 Mpa, and
- iii) blends of i) and ii), and
- b) a polystyrene component having a flexural modulus greater than 200 MPa,
- wherein said film has a tensile modulus of less than 160 MPa and a water vapor transmission rate of at least 100 gm-mil/m2-day.
3 more elements
A method for producing a film, formed from a blend of two incompatible polymer components, said film having a higher WVTR than a film from either of said polymer components, said method comprising the steps of
- a) forming a film from a blend of a semi-crystalline first polymer component with a second polymer component in amounts and at conditions sufficient to produce a blend wherein said first polymer component is a continuous phase, and
- b) drawing said film at a temperature sufficient to cause less than 100% melting of the crystallinity of said soft polymer component to a stretched dimension sufficient to produce separation of at least a portion of the interface between said first and second polymers,
- wherein said first polymer component is selected from
- i) one or more thermoplastic copolymers each comprising between 49 and 90 mole % propylene and at least one C2 to C30 olefinic monomer other than propylene, capable of insertion polymerization, said thermoplastic copolymer having a melting point of 25° C. or more, an MWD of from 1.5 to 4.0, crystallinity of from 5 to 40 weight %, and a flexural modulus less than 100 MPa,
- ii) one or more thermoplastic copolymers each comprising between 84 and 98 mole % ethylene and at least one C3 to C30 olefinic monomer, capable of insertion polymerization, said thermoplastic copolymer having a melting point of 25° C. or more, an MWD of from 1.5 to 4.0, a narrow compositional distribution, and a flexural modulus less than 100 Mpa, and
- iii) blends of i) and ii),
- and said second polymer component is a polystyrene polymer having a flexural modulus greater than 200 MPa.
4 more elements
A cold-drawn film comprising a blend of
- a) a semi-crystalline copolymer component of a major olefinic monomer and a minor olefinic monomer having a melting point greater than 25° C. and a flexural modulus less than 100 MPa, wherein said major olefinic monomer is propylene and said minor olefinic monomer is one or more selected from ethylene and C4 to C20 alpha olefins capable of insertion polymerization, and combinations thereof, and
- b) a polyethylene homopolymer or copolymer component having a density of 0.93 or more and a flexural modulus greater than 200 MPa,
- wherein said semi-crystalline copolymer is present in said film as a continuous phase and said film has a tensile modulus of less than 160 MPa.
A cold-drawn film comprising a blend of
- a) a semi-crystalline copolymer component of a major olefinic monomer and a minor olefinic monomer having a melting point greater than 25° C. and a secant modulus less than 350 MPa, wherein said major olefinic monomer is ethylene or propylene and said minor olefinic monomer is different from said major olefinic monomer and is selected from the group consisting of linear, branched, or ring-containing C2 to C30 olefins, capable of insertion polymerization, and combinations thereof, and
- b) a polystyrene component having a flexural modulus greater than 400 MPa,
- wherein said copolymer is present in said film as a continuous phase and said film has a tensile modulus of less than 375 MPa.
Dependencies are inferred from the claim text.