# US 11,305,520 B2 · High-shrink, high-strength multilayer film

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- Number: US 11,305,520 B2
- Document ID: US11305520B2
- Status: Granted
- Kind: B2
- Application number: 16/604,090
- Filed: 2018-04-13
- Published: 2021-04-08
- Granted: 2022-04-19
- Earliest claimed: 2017-04-13
- Assignees: Cryovac, Inc.
- Applicants: Cryovac, LLC
- Inventors: Ashley Wynne; Kelly Ahlgren; Miles Johnston; Rebecca Kersey
- Web page: https://patentgrep.com/patent/US11305520B2

## CPC

- B32B 27/08: of synthetic resin
- B32B 7/028: Heat-shrinkability
- B32B 27/18: characterised by the use of special additives
- B32B 27/304: {comprising vinyl halide (co)polymers, e.g. PVC, PVDC, PVF, PVDF}
- B32B 27/306: {comprising vinyl acetate or vinyl alcohol (co)polymers}
- B32B 27/32: comprising polyolefins {(comprising vinyl (co)polymers or acrylic (co)polymers B32B27/30)}
- B32B 27/36: comprising polyesters
- B65B 9/073: the web having intermittent motion (B65B9/08 takes precedence)
- B65B 31/024: {specially adapted for wrappers or bags (B65B31/021, B65B31/022 take precedence)}
- B65B 51/30: Devices, e.g. jaws, for applying pressure and heat, e.g. for subdividing filled tubes
- B65B 53/04: supplied by liquids
- B65B 53/063: {Tunnels}
- B65D 65/40: Applications of laminates for particular packaging purposes {(B65D1/0215, B65D1/28, B65D3/22, B65D5/0281, B65D5/563, B65D9/30, B65D29/02, B65D31/02, B65D75/26, B65D77/2024, B65D81/1275, B65D81/3811, B65D81/3823, B65D81/3834, B65D81/3846, B65D81/3858, B65D81/3874, B65D81/3886, B65D81/3897 take precedence; laminates per se or laminated packages characterised by the composition or)}
- B65D 75/002: {in shrink films (B65D71/08 takes precedence)}
- B32B 2250/03: 3 layers
- B32B 2250/04: 4 layers
- B32B 2250/05: 5 or more layers
- B32B 2250/24: All layers being polymeric
- B32B 2307/30: having particular thermal properties
- B32B 2307/31: Heat sealable
- B32B 2307/54: Yield strength; Tensile strength
- B32B 2307/558: Impact strength, toughness
- B32B 2307/7244: Oxygen barrier
- B32B 2307/7246: Water vapor barrier
- B32B 2307/736: Shrinkable
- B32B 2323/046: LDPE, i.e. low density polyethylene
- B32B 2327/00: Polyvinylhalogenides
- B32B 2331/00: Polyvinylesters
- B32B 2367/00: Polyesters, e.g. PET, i.e. polyethylene terephthalate
- B32B 2439/06: Bags, sacks, sachets
- B32B 2439/70: Food packaging
- B32B: LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
- B65B: MACHINES, APPARATUS OR DEVICES FOR, OR METHODS OF, PACKAGING ARTICLES OR MATERIALS; UNPACKING (bundling and pressing devices for cigars A24C1/44; devices for tensioning and securing binders adapted to be supported by the article or articles to be bound B25B25/00; applying closure members to bottles, jars or similar containers B67B1/00-B67B6/00; concurrent cleaning, filling and closing of bottles B67C7/00; emptying bottles, jars, cans, casks, barrels or similar containers B67C9/00)
- B65D: CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES

## Abstract

A multilayer, heat-shrinkable film has a first portion containing an outer heat seal layer and a second portion containing a PVDC barrier layer and a second outer layer comprising polyester. Both film portions comprise polymer networks which are strained by solid-state orientation, but only the first portion contains a crosslinked polymer network. The film has (i) a total free shrink at 85° C. of at least 90% and (ii) an instrumented impact energy-to-break of at least 0.0.65 J/mil and/or an instrumented impact peak load of at least 70 N/mil. The film is primarily made from ethylene-based polymers. Packaging articles can be made by sealing the film to itself. The film comprises no polyamide or polyamide in an amount up to 10 wt %, on a total film weight basis.

## Claims

### Claim 1

A multilayer, heat-shrinkable film comprising a first film portion laminated to a second film portion, wherein:
A) the first film portion comprises a first layer which is a first outer layer and which is a heat-seal layer comprising a blend of a homogeneous ethylene/alpha-olefin copolymer and a heterogeneous ethylene/alpha-olefin copolymer, the first film portion comprising a cross-linked polymer network which has been formed by irradiating the first film portion at 16 to 166 kGy and which has been strained by solid-state orientation;
B) the second film portion comprises (b)(i) a second layer which is a second outer layer and which comprises polyester, and (b)(ii) a third layer which is an oxygen barrier layer comprising polyvinylidene chloride, the third layer being between the first layer and the second layer, the third layer having no crosslinked-polymer network, the second film portion having a polymer network which has been strained by solid state orientation, but the second film portion does not contain a crosslinked polymer network;
wherein the multilayer, heat-shrinkable film has a total free shrink at 85° C. of at least 90% measured in accordance with ASTM D2732, and an instrumented impact energy-to-break of at least 0.65 J/mil, measured in accordance with ASTM D3763, with the film comprising polyamide in an amount of less than 10 wt %, on a total film weight basis.

### Claim 2 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the polyester in the second outer layer makes up from 2 to 20 wt % based on total film weight, and the polyvinylidene chloride in the oxygen barrier layer makes up from 2 to 20 wt % based on total film weight, and the film further comprises an ethylene-based polymer having a peak melting point ≥95° C. and at least one ethylene/unsaturated ester copolymer, the ethylene-based polymer making up from 30 to 80 wt %, based on total film weight, and the ethylene/unsaturated ester making up from 10 to 55 wt %, based on total film weight.

### Claim 3 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the polyester in the second outer layer makes up from 2 to 10 wt % based on total film weight, and the polyvinylidene chloride in the oxygen barrier layer makes up from 5 to 15 wt % based on total film weight, and the film further comprises an ethylene-based polymer having a peak melting point ≥95° C. and at least one ethylene/unsaturated ester copolymer, the ethylene-based polymer making up from 40 to 70 wt %, based on total film weight, and the ethylene/unsaturated ester making up from 25 to 45 wt %, based on total film weight.

### Claim 4 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the homogeneous ethylene/alpha-olefin copolymer is present in the heat seal layer in an amount of from 60 to 95 wt %, based on layer weight, and the heterogeneous ethylene/alpha-olefin copolymer is present in the heat seal layer in an amount of from 5 to 40 wt %, based on layer weight.

### Claim 5 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the film further comprises a core layer in the first film portion, the core layer being between the heat seal layer and the oxygen barrier layer, the core layer comprising a blend of ethylene/unsaturated ester copolymer and at least one member selected from the group consisting of very low density polyethylene, ultra low density polyethylene, and homogeneous ethylene/alpha-olefin copolymer having a peak melting point of at least 95° C.

### Claim 6 (depends on 1)

The heat-shrinkable film according to claim 1, further comprising:
a first tie layer between the oxygen barrier layer and the core layer, with the first tie layer comprising at least one member selected from the group consisting of an ethylene/carboxylic acid copolymer, an ethylene/ester copolymer, anhydride-modified ethylene/ester copolymer, and anhydride-modified ethylene/alpha-olefin copolymer; and
a second tie layer between the oxygen barrier layer and the second outer layer comprising polyester, the second tie layer comprising at least one member selected from the group consisting of an ethylene/carboxylic acid copolymer, an ethylene/ester copolymer, anhydride-modified ethylene/ester copolymer, and anhydride-modified ethylene/alpha-olefin copolymer; and
a third tie layer between the second tie layer and the second outer layer comprising polyester, the third tie layer comprising at least one member selected from the group consisting of anhydride-functional polyolefin, anhydride-functional ethylene/unsaturated acid copolymer, anhydride-functional ethylene/unsaturated ester copolymer, cyclic olefin copolymer, acrylate-based polymer, polyurethane, styrene-based polymer.

### Claim 7 (depends on 1)

The heat-shrinkable film according to claim 1, wherein the multilayer film has a total free shrink at 85° C. of at least 95%.

### Claim 8 (depends on 1)

The heat-shrinkable film according to claim 1, wherein the film has an instrumented impact energy-to-break ≥0.70 J/mil, measured in accordance with ASTM D3763.

### Claim 9 (depends on 1)

The heat-shrinkable film according to claim 1, wherein the film does not contain polyamide.

### Claim 10 (depends on 1)

The heat-shrinkable film according to claim 1, wherein the film contains polyester in an amount of from 1 to 40 wt %, based on total film weight.

### Claim 11 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the multilayer film further comprises a plastomer having a peak melting point ≤90° C. and a melt index of ≤1.1 g/10 min.

### Claim 12 (depends on 11)

The heat-shrinkable film according to claim 11, wherein the plastomer has a peak melting point ≤82° C.

### Claim 13 (depends on 11)

The heat-shrinkable film according to claim 11, wherein the plastomer has a density ≤0.908 g/cc3.

### Claim 14 (depends on 11)

The heat-shrinkable film according to claim 11, wherein the plastomer is present in the film in an amount of at least 2 wt %, based on total film weight.

### Claim 15 (depends on 11)

The multilayer, heat-shrinkable film according to claim 11, wherein the plastomer is present in the seal layer.

### Claim 16 (depends on 1)

The multilayer, heat-shrinkable film according to claim 1, wherein the polyester comprises at least one member selected from the group consisting of polyethylene terephthalate, polycyclohexane dimethylene terephthalate, polycyclohexanedimethanol terephthalic acid, polybutylene terephthalate, polynaphthalene terephthalate, and polyethylene furanoate, and the polyester has a melting point of from 80° C. to 270° C.

### Claim 17 (depends on 16)

The multilayer, heat-shrinkable film according to claim 16, wherein the polyester has a melting point of from 240° C. to 270° C.

### Claim 18

A multilayer, heat-shrinkable film comprising a first film portion laminated to a second film portion, wherein:
A) the first film portion comprises a first layer which is a first outer layer and which is a heat-seal layer comprising a blend of a homogeneous ethylene/alpha-olefin copolymer and a heterogeneous ethylene/alpha-olefin copolymer, the first film portion comprising a cross-linked polymer network which has been formed by irradiating the first film portion at 16 to 166 kGy and which has been strained by solid-state orientation;
B) the second film portion comprises (b)(i) a second layer which is a second outer layer and which comprises polyester, and (b)(ii) a third layer which is an oxygen barrier layer comprising polyvinylidene chloride, the third layer being between the first layer and the second layer, the third layer having no crosslinked-polymer network, the second film portion having a polymer network which has been strained by solid state orientation, but the second film portion not containing a crosslinked polymer network;
wherein the multilayer, heat-shrinkable film has a total free shrink at 85° C. of at least 90% measured in accordance with ASTM D2732, and an instrumented impact peak load strength of at least 70 Newtons/mil, measured in accordance with ASTM D3763, with the film comprising polyamide in an amount of less than 10 wt %, on a total film weight basis.

### Claim 19

A packaging article comprising a multilayer, heat-shrinkable film comprising a first film portion laminated to a second film portion, wherein:
A) the first film portion comprises a first layer which is a first outer layer and which is a heat-seal layer comprising a blend of a homogeneous ethylene/alpha-olefin copolymer and a heterogeneous ethylene/alpha-olefin copolymer, the first film portion comprising a cross-linked polymer network which has been formed by irradiating the first film portion at 16 to 166 kGy and which has been strained by solid-state orientation;
B) the second film portion comprises (b)(i) a second layer which is a second outer layer and which comprises polyester, and (b)(ii) a third layer which is an oxygen barrier layer comprising polyvinylidene chloride, the third layer being between the first layer and the second layer, the third layer having no crosslinked-polymer network, the second film portion having a polymer network which has been strained by solid state orientation, but the second film portion not containing a crosslinked polymer network;
wherein the multilayer, heat-shrinkable film has a total free shrink at 85° C. of at least 90% measured in accordance with ASTM D2732, and an instrumented impact energy-to-break of at least 0.65 J/mil, measured in accordance with ASTM D3763, with the film comprising polyamide in an amount of less than 10 wt %, on a total film weight basis, and the film is heat sealed to itself.