Soft Multi-Layer Shrink Films
OwnerPang-Chia LUinventor
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Abstract
Disclosed is a multi-layer heat shrink film and a method of making the film comprising a core layer comprising at least one α-olefin copolymer selected from propylene-based elastomers, ethylene plastomers, metallocene catalyzed linear low density polyethylenes, and blends thereof, and an equal or lesser amount of a polypropylene having a melting point higher than α-olefin copolymer; at least one skin layer comprising a cyclic olefin copolymer (COC); and at least one tie layer between at least one skin layer and the core layer, the tie layer comprising a material or blend of soft materials having a Hardness (ISO 7619, Type A) of from 45 to 100; and a Tensile Strength (ISO 37) of from 10 MPa to 30 MPa.
Claims26
A multi-layer heat shrinkable film comprising:
- a) a core layer comprising:
- (i) from 5 wt % to 50 wt % of a polypropylene, and
- (ii) an α-olefin copolymer selected from at least one of propylene-based elastomers, ethylene plastomers, metallocene catalyzed linear low density polyethylenes, and blends thereof, the α-olefin copolymer having a melting point lower than the polypropylene;
- b) at least one skin layer comprising a cyclic olefin copolymer (COC);
- and
- c) at least one tie layer between at least one skin layer and the core layer, the tie layer comprising a material or blend of materials having a Hardness (ISO 7619, Type A) of from 45 to 100;
- and a Tensile Strength (ISO 37) of from 10 MPa to 30 MPa.
A method of forming a TD shrinkable film comprising coextruding at least three layers of material comprising:
- a) a core layer including at least:
- (i) from 5 wt % to 50 wt % of a polypropylene, and
- (ii) an α-olefin copolymer selected from at least one of propylene-based elastomers, ethylene plastomers, metallocene catalyzed linear low density polyethylenes, and blends thereof, the α-olefin copolymer having a melting point lower than the polypropylene;
- b) at least one skin layer comprising a cyclic olefin copolymer (COC);
- and
- c) at least one tie layer between at least one skin layer and the core layer, the tie layer comprising a material or blend of materials having a Hardness (ISO 7619, Type A) of from 45 to 100;
- a Tensile Strength (ISO 37) of from 10 MPa to 30 MPa;
- forming an at least a three-layer film therefrom;
- stretching the film in the machine direction (MD) at a temperature that is within a range of from 4° C. below the Tg of the COC in the skin layer(s) to a temperature greater than or equal to the Tg of the COC in the skin layer(s) at a stretching ratio within the range of from 1.05 to 2.8, at a stretching time within the range of from 1 to 10 seconds;
- and
- stretching in the transverse direction (TD) at a temperature within the range of from 70° C. to 120° C. at a stretching ratio within the range of from 4 to 10.
Dependencies are inferred from the claim text.