Multi-layer polyolefin shrink film

Claim 2

A multi-layer, flexible, heat shrinkable thermoplastic packaging film comprising: (a) at least three layers including (i) a core layer located between the other layers and (ii) an auxiliary layer which is stretch oriented; (B) said core layer comprising a polymeric blend, 70% to 90% by weight of said blend being selected from the group consisting of homopolymers and copolymers of ethylene and 30% to 10% by weight of said blend being selected from the group consisting of homopolymers and copolymers of butylene; and, (c) said auxiliary layer comprising a polymer selected from the group consisting of homopolymers and copolymers of propylene.

Claim 3

The multi-layer film of claim 1 including an auxiliary layer on each side of said layer and said core layer comprises 30% to 80% of the thickness of said film and the total of the auxiliary layers comprise 70% to 20% of the thickness.

Claim 4

The multi-layer film of claim 1 wherein 0.1% to 15% of one of the polymeric constituents of the blend of the core layer is blended with the polymer selected for the auxiliary layer to form said auxiliary layer.

Claim 5

The multi-layer film of claim 1 wherein 70% to 90% by weight of said core layer is polyethylene.

Claim 6

The multi-layer film of claim 1 wherein 70% to 90% by weight of said core layer is an ethylene-vinyl acetate copolymer.

Claim 7

The multi-layer film of claim 1 wherein at least one layer of said film is cross-linked.

Claim 8

The multi-layer film of claim 1 including an additional polymeric layer selected from the group consisting of polyesters, polycarbonates, ionomers, vinylidene chloride copolymers, and hydrolyzed ethylene vinyl acetate copolymers.

Claim 9

A multi-layer, flexible, thermoplastic packaging film comprising: (a) a core layer comprising a blend wherein 70% to 90% by weight is an ethylene-vinyl acetate copolymer having a melt flow less than 5.0 and 30% to 10% by weight is selected from the group consisting of butylene homopolymers and copolymers; (b) at least one auxiliary layer on each side of said core layer, said auxiliary layer comprising a polymer selected from the group consisting of propylene homopolymers and copolymers; (c) said multi-layer film being biaxially oriented and heat shrinkable; (d) the thickness of the core layer being 30 to 80% of the total thickness of said multi-layer film and the total thickness of the auxiliary layers being 70% to 20% of the total thickness of the multi-layer film; and, (e) all layers of said multi-layer film having been coextruded.

Claim 10

A multi-layer, flexible, thermoplastic packaging film comprising: (a) a core layer comprising a blend wherein 70% to 90% by weight is an ethylene-vinyl acetate copolymer having a melt flow less than 5.0 and 30% to 10% by weight is selected from the group consisting of butylene homopolymers and copolymers; (b) at least one auxiliary layer on each side of said core layer, said auxiliary layer comprising a polymer selected from the group consisting of propylene homopolymers and copolymers; (c) said multi-layer film being biaxially oriented and heat shrinkable; (d) the thickness of the core layer being 30 to 80% of the total thickness of said multi-layer film and the total thickness of the auxiliary layers being 70% to 20% of the total thickness of the multi-layer film; and, (e) all layers of said multi-layer film having been coextruded.

Claim 11

The multi-layer film of claim 8 wherein the core layer comprises about 80% by weight of an ethylene-vinyl acetate copolymer blended with about 20% by weight of an ethylene-butylene copolymer and the core layer comprises about 60% of the total thickness of the multi-layer film and each auxiliary layer comprises about 20% of the total thickness of the film.

Claim 12

The multi-layer film of claim 8 wherein the core layer comprises 70% to 90% by weight ethylene-vinyl acetate copolymer and 30% to 10% by weight ethylene-butylene copolymer.

Claim 13

The multi-layer film of claim 8 wherein said film has three layers with the ratio of thicknesses of said layers being 1/3/1.

Claim 14

The multi-layer film of claim 8 wherein said film has three layers with the ratio of thicknesses of said layers being 1/4/1.

Claim 15

A multi-layer, flexible, thermoplastic packaging film including a core layer which comprises a blend having 70% to 90% by weight of ethylene-vinyl acetate copolymer and 30% to 10% by weight of a butylene polymer.

Claim 16

A multi-layer, flexible, thermoplastic packaging film including a core layer which comprises a blend having 70% to 90% by weight of ethylene-vinyl acetate copolymer and 30% to 10% by weight of a butylene polymer.

Claim 17

A multi-layer, flexible, heat shrinkable, thermoplastic packaging film including a hot blown core layer consisting of a blend of ethylene vinyl acetate copolymer and polybutylene and a thin, oriented layer on each side of said core layer, said thin layer comprising a polymer selected from the group consisting of polypropylene and ethylene-propylene copolymers, said thin layer having a thickness in the range from about 0.05 mil to about 0.38 mil.

Claim 18

A multi-layer, flexible, heat shrinkable, thermoplastic packaging film including a hot blown core layer consisting of a blend of ethylene vinyl acetate copolymer and polybutylene and a thin, oriented layer on each side of said core layer, said thin layer comprising a polymer selected from the group consisting of polypropylene and ethylene-propylene copolymers, said thin layer having a thickness in the range from about 0.05 mil to about 0.38 mil.

Claim 19

The multi-layer, flexible film of claim 14 wherein the core layer is 1 to 8 times the thickness of each of said thin, oriented layers.

Claim 20

The multi-layer, flexible film of claim 14 wherein the thin layers are biaxially oriented.

Claim 21

A multi-layer, flexible, thermoplastic packaging film comprising: (a) a central layer selected from the group consisting of polyesters, polycarbonates, ionomers, vinylidene chloride copolymers, and hydrolyzed ethylene vinyl acetate copolymers; (b) a core layer on each side of said central layer, said core layers being of approximately the same thickness and the core layers comprising a polymeric blend, the 70% to 90% by weight of said blend being selected from the group consisting of homopolymers and copolymers of ethylene and 30% to 10% by weight of said blend being selected from the group consisting of homopolymers and copolymers of butylene; and, (c) an auxiliary layer on the outer side of each core layer, said auxiliary layers comprising a polymer selected from the group consisting of homopolymers and copolymers of propylene.

Claim 22

A multi-layer, flexible, thermoplastic packaging film comprising: (a) a central layer selected from the group consisting of polyesters, polycarbonates, ionomers, vinylidene chloride copolymers, and hydrolyzed ethylene vinyl acetate copolymers; (b) a core layer on each side of said central layer, said core layers being of approximately the same thickness and the core layers comprising a polymeric blend, the 70% to 90% by weight of said blend being selected from the group consisting of homopolymers and copolymers of ethylene and 30% to 10% by weight of said blend being selected from the group consisting of homopolymers and copolymers of butylene; and, (c) an auxiliary layer on the outer side of each core layer, said auxiliary layers comprising a polymer selected from the group consisting of homopolymers and copolymers of propylene.

Claim 23

The multi-layer film of claim 17 wherein the film has five layers and the ratio of the thicknesses of the film is 1/2/1/2/1.