Vacuum Skin Packaging Film

Abstract

A plastic film suitable for vacuum skin packaging application. The film is crosslinked and comprises ethylene acrylate copolymer.

Claims

1. A crosslinked multilayer film suitable for vacuum skin packaging, comprising at least 30% per volume of an ethylene acrylate copolymer.

2. A crosslinked multilayer film according to claim 1, wherein the film comprises from 40% to 90% per volume of an ethylene acrylate copolymer.

3. The crosslinked multilayer film according to claim 1, wherein the film further comprises an oxygen barrier copolymer.

4. The crosslinked multilayer film according to claim 3, wherein the oxygen barrier copolymer is selected from EVOH, PVDC and polyamide.

5. The crosslinked multilayer film according to claim 1, wherein the film comprises an outer sealing layer, another outer layer and a core layer between them.

6. The crosslinked multilayer film according to claim 5, wherein the film further comprises a first abuse layer between the outer layer and the core layer and a second abuse layer between the core layer and the outer sealing layer.

7. The crosslinked multilayer film according to claim 6, wherein the ethylene acrylate copolymer is comprised in the outer sealing layer and/or in an abuse layer of the film.

8. The crosslinked multilayer film according to claim 1, wherein the ethylene acrylate copolymer comprises at least 5% per mass acrylate.

9. The crosslinked multilayer film according to claim 8, wherein the ethylene acrylate copolymer comprises at least 10% per mass acrylate.

10. The crosslinked multilayer film according to claim 9, wherein the ethylene acrylate copolymer comprises at least 12% per mass acrylate.

11. The crosslinked multilayer film according to claim 1, wherein the ethylene acrylate copolymer has a melting point of less than 100° C.

12. The multilayer film according to claim 1, wherein the ethylene acrylate copolymer is EMA, EBA, EMMA or EEA.

13. The multilayer film according to claim 12, wherein the ethylene acrylate copolymer is EMA or EBA.

14. The multilayer film according to claim 1, wherein the film is produced by a hot blown film process.

15. Use of the multilayer film according to claim 1, in a vacuum skin packaging process.

Description

DETAILED DESCRIPTION

[0048] The present invention provides a crosslinked multilayer film suitable for vacuum skin packaging comprising at least 30% per volume of at least one ethylene acrylate copolymer and optionally further comprising at least one oxygen barrier polymer.

[0049] According to a preferred embodiment the film comprises from 40% to 90% per volume ethylene acrylate copolymer, more preferably from 50% to 80% per volume.

[0050] In a preferred embodiment of the film, the ethylene acrylate copolymer is EMA, EBA or EMMA.

[0051] In a further preferred embodiment, the acrylate content of the copolymer per mass is at least 5%, more preferably at least 10%, more preferably at least 12%.

[0052] In a preferred embodiment of the film, the ethylene acrylate copolymer has a melting point of less than 100° C.

[0053] In a preferred embodiment of the film the ethylene acrylate copolymer has a Melt Flow Index of less than 4 measured at 190° C./2.16 kg as per ASTM 1238.

[0054] The film can be produced by processes well known in the art. In a preferred embodiment, the film is produced by conventional air cooled hot blown film process.

[0055] In a preferred embodiment of the film, the film is irradiated by electron beam or by gamma radiation.

[0056] In a preferred embodiment of the film the total thickness of the film is from 50 to 300 microns, more preferably 70 to 250 microns.

[0057] Film Structure

[0058] The film is generally a film comprising 3 or more layers, such as 9 layers or more.

[0059] Such layers can be the outer sealing layer (in direct contact with the food), oxygen barrier layer (comprising for example polyamide and/or EVOH), abuse layers and adhesive tie layers (allowing bonding between layers that have no physical adhesion).

[0060] Outer Sealing Layer

[0061] The outer sealing layer of the film is preferably polyolefin based, more preferably ethylene copolymer based., even more preferably ethylene alpha olefin copolymer based or ethylene ester based (such as EVA and/or EMA). For being able to seal to more unconventional bottom sheets or trays like aluminium the outer sealing layer may comprise tackifiers or other compounds.

[0062] The thickness of the outer sealing layer is preferably from 5 to 100 microns, more preferably from 10 to 80 microns.

[0063] Core Layer

[0064] The film in one embodiment comprises in the core layer a high oxygen barrier material so that it protects the components of the pack from the detrimental effect of oxygen ingress. EVOH is a preferred option but also polyamide and PVDC are viable alternatives. The EVOH is preferably 24 to 50% ethylene per mol, more preferably 27 to 48% per mol. Even more preferably the EVOH is characterized by an ethylene content of 29 to 48% per mol.

[0065] The thickness of the core layer is preferably from 3 to 20 microns, with a more preferable thickness being 5 to 16 microns.

[0066] Abuse Layer(s)

[0067] Preferably, the abuse layer(s) comprise(s) an ethylene acrylate copolymer. This polymer can be alone in this layer or in a form of blend or compound. Suitable blending partners for the ethylene acrylate copolymer include ethylene alpha olefin copolymers, styrene polymers, LDPE, ionomers, EVA copolymers and others.

[0068] Tie Layer(s)

[0069] As well known in the art, there is often not enough natural adhesion between ethylene acrylate copolymers and high barrier polymers such as EVOH. Therefore, suitable adhesive resins can be used so that the film does not collapse under the oven heating.

[0070] Suitable materials for the tie layer process include maleic anhydride modified EVA, maleic anhydride modified polyethylene, maleic anhydride modified EMA, maleic anhydride modified elastomer, partially saponified EVA copolymer and polyurethane elastomer.

[0071] According to a preferred embodiment, the ethylene acrylate copolymer is comprised in the outer sealing layer and/or in an abuse layer of the film.

EXAMPLES

Example 1

[0072] Extrusion Process:

[0073] A 7 layer film is produced in an air cooled hot blown film line. The film structure is as follows:

[0074] Outer layer: 100% of linear low-density polyethylene material Dowlex® NG5056E from Dow Chemical company.

[0075] First abuse layer: EMA having 18% per mass methyl acrylate content.

[0076] First tie layer: Admer® 518E (LLDPE maleic anhydride grafted material).

[0077] Barrier Layer: EVOH 38% mol having a melt flow index of about 2 measured at 190° C., 2.16 kilos.

[0078] Second tie layer: LLDPE based tie layer same as first tie layer.

[0079] Second abuse layer: EMA having 18% per mass methyl acrylate content.

[0080] Sealing layer: 70% metallocene LLDPE+30% low density polyethylene.

[0081] Thickness of different layers are as follows:

[0082] 22/14/8/8/8/20/20 microns with total thickness 100 microns.

[0083] EMA content per volume is 34%.

[0084] Crosslinking:

[0085] The film was crosslinked at a radiation dose of 10 Mrads.

Example 2

[0086] The same film was produced but instead of the EMA copolymer an EBA copolymer was used. The EBA copolymer had 18% per mass butyl acrylate.

Example 3 (Comparative)

[0087] In the comparative example, the ethylene acrylate polymers were substituted by EVA copolymer with 18% vinyl acetate per mass. The EVA copolymer is used as prior art as per EP0243510.

[0088] Measurement of Vacuum Skin Packaging Performance.

[0089] The films were tested as per their vacuum skin packaging performance in a Sealpac machine. 25 dummy meat pieces were used for evaluation of each one having as reference the forming capabilities of each one and the presentation of the packs.

[0090] The dummies represented different levels of difficulty to pack but same for the three films so that comparison is fair.

TABLE-US-00001 NUMBER OF FILM TOTAL NUMBER ACCEPTABLE REFERENCE OF PACKS PACKS Example 1 25 21 Example 2 25 23 Example 3 25 19 (comparative)

[0091] The result shows that the substitution of EVA by ethylene acrylate copolymer giving such beneficial properties is surprising in view of the current prior art.