MULTILAYER FILM

Abstract

The invention relates to a multilayer plastic film with high permeability to oxygen, to the use of such films and to polymer packaging comprising said film.

Claims

1. A multilayer film comprising: an intermediate layer comprising an ethylene alpha olefin copolymer of density 0.855-0.895 in a blend with at least 10% LDPE per weight; an outer layer comprising an ethylene alpha olefin copolymer of density 0.92 to 0.950; and a sealing layer comprising EMA and/or EVA.

2. The multilayer film according to claim 1, wherein the density of the ethylene alpha olefin copolymer of the intermediate layer is in the range 0.860 to 0.885 g/cc.

3. The multilayer film according to claim 1, wherein the film comprises an additional intermediate layer of a blend of ethylene alpha olefin copolymer and LDPE.

4. The multilayer film according to claim 1, wherein the film has an oxygen permeability of more than 10,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

5. The multilayer film according to claim 4, wherein the film has an oxygen permeability of more than 11,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

6. A thermoforming process comprising using a multilayer film according to claim 1 as top lidding film and/or bottom film.

7. A method for providing a packaging, the method comprising using multilayer film according to claim 1, for packaging food, preferably sea food.

8. Polymer packaging comprising a top lidding film and a bottom film, wherein the top lidding film is a multilayer film according to claim 1, and the bottom film is also a multilayer film according to claim 1 or APET.

9. The multilayer film according to claim 2, wherein the film comprises an additional intermediate layer of a blend of ethylene alpha olefin copolymer and LDPE.

10. The multilayer film according to claim 2, wherein the film has an oxygen permeability of more than 10,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

11. The multilayer film according to claim 10, wherein the film has an oxygen permeability of more than 11,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

12. The multilayer film according to claim 3, wherein the film has an oxygen permeability of more than 10,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

13. The multilayer film according to claim 12, wherein the film has an oxygen permeability of more than 11,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

Description

DETAILED DESCRIPTION

[0052] The present invention provides a multilayer film comprising an intermediate layer comprising an ethylene alpha olefin copolymer of density 0.855-0.895 in a blend with at least 10% LDPE per weight, an outer layer comprising an ethylene alpha olefin copolymer of density 0.92 to 0.950, a sealing layer comprising EMA and/or EVA.

[0053] Preferably, the density of the ethylene alpha olefin copolymer of the intermediate layer is in the range 0.860 to 0.885 g/cc.

[0054] In a further preferred embodiment the multilayer film comprises an additional intermediate layer of a blend of ethylene alpha olefin copolymer and LDPE.

[0055] The multilayer film has preferably an oxygen permeability of more than 10,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity, and more preferably an oxygen permeability of more than 11,000 cc/m.sup.2*atm*24 h as measured according to ASTM D3985 at 23 C. and 0% relative humidity.

[0056] The present invention further relates to the use of the multilayer film according to the present invention as top lidding film and/or bottom film in a thermoforming process.

[0057] The present invention further relates to the use of the multilayer film according to the present invention for packaging food, preferably sea food.

[0058] In a further embodiment the present invention relates to a polymer packaging comprising a top lidding film and a bottom film, wherein the top lidding film is a multilayer film according to the invention, and as bottom film is also a multilayer film according to the present invention or APET.

[0059] Preferably the film is produced by the hot blown film method.

[0060] Preferably the film is of the structure:

OUTER LAYER/INTERMEDIATE LAYER/SEALING LAYER

[0061] or

OUTER LAYER/INTERMEDIATE LAYER1/INTERMEDIATE LAYER 2/INTERMEDIATE LAYER 3/SEALING LAYER

[0062] or

OUTER LAYER/INTERMEDIATE LAYER1/INTERMEDIATE LAYER 2/INTERMEDIATE LAYER 3/INTERMEDIATE LAYER 4/INTERMEDIATE LAYER 5/SEALING LAYER

[0063] or films with more than seven layers, e.g. up to 20 layers, comprising additional INTERMEDIATE LAYERs.

[0064] The intermediate layers may have the same or different compositions.

[0065] The film of the present invention may have a thickness from 14 to 120 microns, preferably 50 to 90 microns, even more preferably 60 to 80 microns.

Sealing Layer

[0066] The sealing layer comprises EVA and/or EMA. Appeel from Dupont or Lotryl Bestpeel from Arkema are preferred.

[0067] The sealing layer must be sealable to APET. This means that the heat seal strength of the film to APET trays must be more than 2N/15 mm in at least a temperature of range 120-200 C. under a typical heat seal time of 2 seconds and seal pressure of 3 bars. The two films are heat sealed and the seal strength is measured at a 15 mm width according to ASTM F88.

Intermediate Layers

[0068] The film comprises at least one intermediate layer comprising a blend of an ethylene alpha olefin copolymer of density 0.855-0.895 g/cc and at least 10% wt of low density polyethylene (LDPE). Preferably the density of the ethylene alpha olefin copolymer is from 0.860 to 0.885 g/cc.

[0069] Preferably, at least a second intermediate layer comprises an ethylene alpha olefin copolymer of density 0.855-0.895 g/cc in a blend with LDPE.

[0070] The film may comprise further intermediate layers comprising ethylene alpha olefin copolymer of density 0.855-0.895 g/cc, preferably the density is from 0.860 to 0.885 g/cc.

[0071] The use of LDPE in the blends with such low density alpha olefin copolymers improve [0072] the melt strength of the film [0073] processing of the film [0074] renders it somewhat stiffer, thus easier to handle in a VSP process

Outer Layer

[0075] The outer layer comprises an ethylene alpha olefin copolymer of density 0.920 to 0.950. Using an ethylene alpha olefin copolymer with said specific density of 0.920 to 0.950 the film works in the proximity of a heated dome (VSP process) while surprisingly the oxygen permeability is maintained at high levels.

[0076] Preferably the thickness of the outer layer is less than 5 microns, more preferably less than 3 microns.

Crosslinking of the Film

[0077] The film preferably undergoes ionizing radiation crosslinking in a dose of at least 5 megarads. Gamma radiation crosslinking is also possible.

[0078] Preferably the film is produced by the hot blown film method.

EXAMPLES

[0079] In a commercial blown film line, the following plastic films were produced

Example 1

[0080]

TABLE-US-00001 Outer layer 98% EAO1 + 2% slip 2 microns antiblock additives Intermediate layer 1 85% EAO2 + 15% LORE 30 microns Intermediate layer 2 95% EAO2 + 5% LORE 10 microns Intermediate layer 3 95% EAO2 + 5% LORE 3 microns Intermediate layer 4 100% EAO2 7 microns Intermediate layer 5 100% EAO2 7 microns Sealing layer EMA1 10 microns
EAO1=an ethylene hexene copolymer of density 0.934
EAO2=an ethylene octene copolymer of density 0.870
LDPE=a low density polyethylene of density 0.924
EMA1=An EMA based peel seal material

[0081] Production of the film (sample 1) was stable with no processing issues.

Example 2

[0082]

TABLE-US-00002 Outer layer 98% EAO1 + 2% slip 2 microns antiblock additives Intermediate layer 1 100% EAO2 30 microns Intermediate layer 2 95% EAO2 + 5% LORE 10 microns Intermediate layer 3 95% EAO2 + 5% LORE 3 microns Intermediate layer 4 80% EAO2 + 20% LORE 7 microns Intermediate layer 5 100% EAO2 7 microns Sealing layer EMA1 10 microns

[0083] Production of the film (sample 2) was stable with no processing issues.

Example 3

[0084] Same film as example 2 but all intermediate layers contained 100% EAO2 and no LDPE.

[0085] In Example 3 a deterioration of the processing behavior of the film was noticed. There were frequent breakages possibly due to the inadequate melt strength of the film. Further to this the extruder pressures increased substantially and the line productivity significantly decreased.

[0086] Prior to further testing both samples 1 and 2 were irradiated at a dose of 12 MRads.

Evaluation of Examples

[0087] The above irradiated samples were tested at a commercial thermoforming machine and a commercial VSP machine.

[0088] Both films were tested as both top lidding films and bottom films in thermoforming. Surprisingly, both films could function as both top lidding and bottom films.

[0089] Both films were tested as skin films with good results. Irradiated sample 1 was sealed to APET to form pack 1. Irradiated sample 2 was sealed to APET to form pack 2.

[0090] Sealing strength to APET sheet was measured in Instron machine per 15 mm width according to ASTM F88.

[0091] Seal strength of pack 1 and of pack 2 was average 6N/15 mm. There were no leakages and unsealed areas.

Organoleptic Test

[0092] A panel of five people evaluated the smell of the films in comparison to a commercial high barrier VSP film of FLEXION series. It was concluded that the organoleptic properties of the film were similar to the commercial film (acceptable).

Oxygen Permeability Test

[0093] Both films were tested as per oxygen permeability according to ASTM D3985 at conditions 23 C., 0% RH.

[0094] Film 1 had an oxygen permeability of 11,200 cc/m.sup.2*atm*24 h while film 2 showed an oxygen permeability of 11,800.