HIGH ABUSE HEAT SHRINKABLE FILM

Abstract

The present invention refers to a multilayer heat shrinkable film characterized by a combination of desirable properties, such as high shrinkage, good optical properties, excellent sealability, high abuse and high puncture resistance. The invention further is directed to a method of producing said film. The invention is further directed to the use of said film or bags and pouches made thereof for packaging goods as for example food products. The invention also refers to tubes made with the film.

Claims

1. A heat shrinkable film, wherein the film comprises at least one layer comprising a blend of a first copolyamide and a second copolyamide, wherein the second copolyamide is a polyamide 6/66/12.

2. The film of claim 1, wherein the film has a further layer comprising a high oxygen barrier material.

3. The film of claim 1, wherein the blend of the two copolyamides comprises also a clay-modified polyamide.

4. The film of claim 1, wherein the film comprises a sealing layer.

5. The film of claim 4, where the sealing layer comprises a polyolefin or a blend of polyolefins.

6. The film of claim 5, where the sealing layer comprises a homogeneous polyolefin.

7. The film of claim 1, where the film comprises an intermediate layer between the sealing and the layer of the blend of copolyamides.

8. The film of claim 7, where the intermediate layer comprises an adhesive tie material.

9. A bag made from the film claim 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0047] According to a first aspect the present invention is directed to a heat shrinkable film, where the film comprises at least one layer comprising or consisting of a blend of a first copolyamide and a copolyamide 6/66/12. The film has a shrinkage of at least 10% measured according to ASTM 2732 in water at 90 C. in at least one of MD, TD directions.

[0048] According to a preferred embodiment of the invention, the first copolyamide is a 6/66 copolyamide.

[0049] According to a further preferred embodiment, the percentage ratio (per weight) of the first and the second copolyamide is from 90/10 to 10/90.

[0050] In a further preferred embodiment, the film comprises a sealing layer. This layer allows the film to be heat sealed to itself or to another film thus allowing it to form a hermetically closed container (e.g. a bag).

[0051] In the film according to the present invention, the heat sealing layer may comprise a single polyolefin or a blend of different polyolefins. In a preferred version of the structure, the sealing layer comprises at least one homogeneous polyolefin.

[0052] In another embodiment, the sealing layer comprises heterogeneous ethylene alpha olefin copolymer with density less than 0.920 g/cm.sup.3.

[0053] In a further embodiment the sealing layer comprises a homogeneous polyolefin produced with metallocene catalysts.

[0054] In a preferred embodiment of the invention, the multilayer film comprises an oxygen barrier material, preferably PVDC, EVOH, polyamide or polyester.

[0055] In another preferred version of the invention, the polyamide blend comprises a percentage of clay modified polyamide (nano-modified). The percentage of clay-modified masterbatch is for example from about 0.5 to 10%.

[0056] Between the sealing layer and the oxygen barrier layer, a tie layer could be used. Preferred materials for this tie layer may be ethylene ester copolymers, such as ethylene vinyl acetate copolymers, ethylene methyl acrylate copolymers and other materials well known in the art. A preferred version might include maleic anhydrite modified ethylene ester copolymers or maleic anhydrite modified LLDPE. Commercial trademarks are for example BYNEL from Dupont and ADMER from Mitsui.

[0057] The outer layer according to the present invention comprises preferably polyethylene or polypropylene copolymers. Especially preferred are ethylene octene copolymers with a melting point from about 90 to about 130 C. Blends with EVA are also possible.

[0058] Another preferred material for the outer layer is styrene based copolymer, such as styrene butadiene copolymer.

[0059] Between the outer and the barrier layer there may be another layer incorporating a tie layer. Preferred materials for this tie layer may be ethylene ester copolymers, such as ethylene vinyl acetate copolymers, ethylene methyl acrylate copolymers and other materials well known in the art. A preferred version might include maleic anhydrite modified ethylene ester copolymers or maleic anhydrite modified LLDPE. Commercial trademarks are for example BYNEL from Dupont and ADMER from Mitsui.

[0060] Any of the layers described above may also include additives well known in the art such as slip agents, antiblock, polymer processing aids, antistatic, antifog, acid scavengers, odor scavengers and the like. A person skilled in the art may select the right additives according to any particular needs.

[0061] In one preferred embodiment, the multilayer film is irradiated. The irradiation may be a beam, gamma radiation, UV radiation or other.

[0062] According to a further aspect, the present invention discloses a bag or pouch comprising a film according to the present invention.

[0063] In a further aspect, the invention is directed to the use of the films or the bag or pouch of the invention for packaging food. For example, the food item is putted inside the bag and the air is removed (vacuumising) with the help of a vacuum device. Subsequently, the open end of the bag is sealed and the vacuum pack is placed in a heat shrinking media such as hot water under a temperature that ensures the shrink of the pack (e.g. 90 C.). The pack than is ready and is characterized by appealing appearance and long shelf life because of the absence of oxygen.

[0064] The present invention is now described by the following Examples:

EXAMPLES

Example 1

[0065] A 5 layer film is produced in a double bubble (the double bubble method is described in U.S. Pat. No. 3,456,044) commercial line with the following recipe:

TABLE-US-00001 Inner (sealing layer) 100% E1 Adjacent layer 100% M1 Barrier layer 70% PA1 + 30% PA2 Adjacent layer 100% M1 Outer layer 100% E2

[0066] See table 1

[0067] The thickness of the structure is 35/8/40/8/9 starting from the inner and going to the outer layer.

[0068] The processability of the film was unexpectedly good. There was stable orientation and the line speed could be increased much more than if instead of the blend a pure copolyamide 6/66 was used.

[0069] As comparison, tests were done with commercial product with thickness 100 microns. The product is marketed as high abuse, meaning it targets the same potential market as the film of the invention.

Example 2

[0070] A 5 layer film is produced in a double bubble commercial line with the following recipe

TABLE-US-00002 Inner (sealing layer), 100% E1 Adjacent layer 100% M1 Barrier layer 70% PA1 + 28% PA2 + 2% nano modified polyamide 6 Adjacent layer 100% M1 Outer layer 100% E2

[0071] See also table 1

TABLE-US-00003 TABLE 1 Melting Melt Index Density point Type Description Manufacturer g/10 min g/cm.sup.3 C. E1 ATTANE 4100 DOW 1 0.912 122 E2 Elite 5400G DOW 1 0.917 122 M1 MODIFIED Dupont 2 0.95 EVA P2 AFFINITY PL Dow 1 0.902 100 1880 PA1 POLYAMIDE Ube 196 6/66 PA2 POLYAMIDE Ube 190 6/66/12

[0072] Tests

1. Haze measurement. The haze measurement was done according to ASTM D 1003.
2. Gloss measurement. This was done according to BS 2782.
3. Shrinkage measurement done according to ASTM 2732 at 90 C.
4. Puncture resistance

[0073] The puncture resistance was measured with a Versa Test instrument from company Mecmesin.

[0074] The results are displayed on table 2

TABLE-US-00004 TABLE 2 PUNCTURE SHRINKAGE FORCE HAZE GLOSS (MD/TD) in kilos Example 1 12 90 30/23 5 Example 2 15 85 28/20 4.5 Commercial 12 85 27/22 3 material