RU2275811C2 - Film used as package and enclosure for meat, meat with bones and pasty food products, and bag manufactured from the film - Google Patents

Abstract

FIELD: food-processing industry, in particular, packaging of food products in meat industry.

SUBSTANCE: sleeved film has inner layer formed from at least one copolyamide and at least one amorphous polyamide and/or at least one homopolyamide and/or at least one modified polyolefin, intermediate polyolefin layer, and outer layer made from at least one homopolyamide and/or at least one copolyamide and/or at least one copolymer of ethylene and vinyl alcohol and/or one modified polyolefin. Adhesion promoting layer is positioned between inner layer and intermediate layer, and also between intermediate layer and outer layer. Welded seam of film has substantially higher strength and may be produced at much lower temperatures. Welded seam is characterized by increased puncture resistance.

EFFECT: improved qualities of film allowing it to be used for packaging of various products.

21 cl, 6 ex

Description

The present invention relates to a multilayer, biaxially elongated, shrinkable, heat sealable sleeve film and its use as a packaging and casing for meat, meat with bones and pasty foods.

A five-layer sleeve film based on polyamide is already known from DE 4339337 C2 and is used as a packaging and casing for pasty food products, especially for sausages. Such a sleeve film consists of an inner and an outer layer formed of the same polyamide material, a middle polyolefin layer, and also two layers formed of an adhesion promoter that serves the same material and located respectively between the inner and middle layers and between the middle and outer layers. The inner and outer layers are formed of at least one aliphatic polyamide and / or at least one aliphatic copolyamide, as well as at least one partially aromatic polyamide and / or at least one partially aromatic copolyamide, while partially aromatic polyamide and / or copolyamide accounts for from 5 to 60 wt.% in terms of the total weight of the polymer mixture of partially aromatic and aliphatic polyamides and copolyamides. Such a sleeve film produced by coextrusion, due to its biaxial stretching and heat setting, gives the ability to controlled shrinkage. Such a sleeve film does not fully meet all the requirements for its operational and technical properties, which are important for its use as a shell, respectively, packaging for meat, especially meat with bones. So, in particular, such a film has too little puncturing strength, and therefore when it is used as a packaging film for meat with bones, there is a danger of it being pierced by protruding bones after it is pulled hot on the packaged meat. In addition, such sleeve films, when used as packaging and shells for meat or meat with bones and for pasty food products, should also allow the possibility of their simple sealing by heat sealing. For bags made of sleeve films of this type, the strength of their heat-welded seam is a decisive factor determining the possibility of their use as packaging material. So, in particular, a bag made of a polymer film sealed from below with a heat-sealing seam when packaged into it through a packing tube, for example, a ham or meat cut into large pieces, is subjected to significant loads, which arise when the packaged piece falls into the bag and which, depending on its weight, can cause to rupture of the heat-welded seam and thereby to the full opening of the package from the bottom side. In addition, the heat-welded seam is subjected to exceptionally high loads and with subsequent evacuation and shrinkage of the packages. Another factor that determines the high requirements for the puncture strength of the film and the strength of its heat-welded seam are the loads to which the sealed bag with the product packaged in it is exposed during transportation and storage.

Based on the foregoing, the present invention was based on the task of developing a biaxially elongated, shrinkable, heat sealable sleeve film as a packaging and casing for meat, meat with bones and pasty food products, which, along with such requirements for such a packaging film, high impermeability to water vapor and oxygen, would have high puncturing strength, on the one hand, and would be characterized by high strength heat seal, on the other hand ones.

This problem is solved according to the invention using a multilayer, biaxially elongated, shrinkable, heat sealable sleeve film, the distinguishing features of which are presented in claim 1.

At least one heat sealable copolyamide is included in the inner layer of the tubular film of the invention. Such copolyamides, known per se, are obtained from monomers selected from the group consisting of caprolactam, laurinlactam, ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecandicarboxylic acid, terephthalic acid, isomethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine dimethylenediamine di octamethylene diamine and xylylenediamine. The thickness of the inner layer is from 5 to 16 microns.

When creating the invention, it was unexpectedly found that the formation of the inner layer of the sleeve film from copolyamide with the addition of amorphous polyamide, and / or homopolyamide, and / or a modified polyolefin, can significantly increase the strength of the heat-seal joint compared to the strength of the heat-seal joint characteristic of the film, the inner the layer of which is formed from pure copolyamide, respectively, to achieve high strength values of the heat seal even at a lower temperature of heat sealing. In accordance with this, the film of the invention has significant operational and technical advantages over the known films.

As amorphous polyamides for forming the inner layer, polyamides are used, the glass transition temperature of which in the dry state is from 50 to 200 ° C. Examples of such polyamides are polyamide 6I / 6T, polyamide 6-3-T and polyamide 6I.

As homopolyamides for the formation of the inner layer, polyamides are used, which can be obtained from the same monomers as the copolyamides described above. Such homopolyamides can be aliphatic as well as partially aromatic compounds.

The modified polyolefins used to form the inner layer are copolymers of ethylene or propylene and optionally other linear α-olefins containing from 3 to 8 C atoms, with α, β-unsaturated carboxylic acids, preferably with acrylic acid, methacrylic acid, and / or their salts with metals, and / or their alkyl esters, or the corresponding graft copolymers of these monomers grafted onto polyolefins, or partially saponified ethylene vinyl acetate copolymers, which are optionally subjected The chickpeas are grafted copolymerization with α, β-unsaturated carboxylic acid and are characterized by a low degree of saponification, or a mixture thereof. The modified polyolefins can also be modified homo- or copolymers of ethylene and / or propylene and optionally other linear α-olefins with 3-8 C atoms, containing grafted monomers selected from the group of α, β-unsaturated dicarboxylic acids, preferably maleic acid, fumaric acid, itaconic acid or their anhydrides, esters, amides or imides.

The main component of the inner layer is heat-sealable copolyamide or a mixture of heat-sealable copolyamides, while the amount of such a main component is from 50 to 95 wt.%. Each of the other components, which are amorphous polyamide and / or homopolyamide and / or modified polyolefin, can be added to the main component in an amount of from 1 to 30 wt.%, Preferably from 5 to 25 wt.%, Calculated on the whole weight inner layer.

Both formed from the adhesion promoter preferably have the same composition and are made from functional groups modified polyolefins. Such modified polyolefins include modified homo- or copolymers of ethylene and / or propylene and optionally other linear α-olefins with 3-8 C atoms containing grafted monomers selected from the group of α, β-unsaturated dicarboxylic acids, preferably maleic acid , fumaric acid, itaconic acid or their anhydrides, esters, amides or imides. The thickness of each of the layers of the adhesion promoter is from 3 to 10 μm.

The middle layer in the packaging film according to the invention is a polyolefin layer, preferably formed from homopolymers of ethylene or propylene and / or copolymers of linear α-olefins with 2-8 C-atoms. To form this middle layer, it is preferable to use linear low density polyethylene, high density polyethylene, polypropylene homopolymer, polypropylene block copolymer and random polypropylene copolymer. The thickness of this middle layer is from 6 to 22 microns.

Various materials can be used to form the outer layer, namely homopolyamides individually or in mixtures with each other, copolyamides individually or in mixtures with each other, as well as mixtures of homo and copolyamides. Additionally, copolymers of ethylene with vinyl alcohol and / or modified polyolefins may also be included in the composition of the material for forming the outer layer. The thickness of the outer layer is from 12 to 43 microns.

Homo- and copolyamides suitable for use for the above purposes are known and can be obtained from the corresponding monomers, such as, for example, caprolactam, laurinlactam, ω-aminoundecylic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecandicarboxylic acid, terephthalic acid, isophthalic acid, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylene diamine and xylylenediamine.

Preferred homo- and copolyamides are polyamide 6, polyamide 12, polyamide 610, polyamide 612, polyamide MXD6, polyamide 6/66, polyamide 6/12 and polyamide 6I / 6T.

Copolymers of ethylene and vinyl alcohol are obtained by complete saponification of ethylene vinyl acetate copolymers. In general, ethylene in its copolymers with vinyl alcohol accounts for 27 to 48 mol%. To the material used to form the outer layer, it is preferable to add copolymers of ethylene and vinyl alcohol, in which ethylene accounts for from 27 to 38 mol.%.

Modified polyolefins are copolymers of ethylene or propylene and optionally other linear α-olefins containing from 3 to 8 C atoms, with α, β-unsaturated carboxylic acids, preferably with acrylic acid, methacrylic acid, and / or their salts with metals, and / or their alkyl esters, or the corresponding graft copolymers of these monomers grafted on polyolefins, or partially saponified copolymers of ethylene and vinyl acetate, which are optionally grafted with α, β-unsaturated arbonovoy acid and have a low saponification level, or mixtures thereof. The modified polyolefins can also be modified homo- or copolymers of ethylene and / or propylene and optionally other linear α-olefins with 3-8 C atoms, containing grafted monomers selected from the group of α, β-unsaturated dicarboxylic acids, preferably maleic acid, fumaric acid, itaconic acid or their anhydrides, esters, amides or imides.

The main component of the outer layer are homopolyamides used individually or mixed with each other, copolyamides used individually or mixed with each other, or a mixture of homo- and copolyamides, with the amount of such a main component being from 50 to 100 wt.%. When other components, such as ethylene vinyl alcohol copolymers and / or modified polyolefins, are included in the material of the outer layer, each of them can be added to the main component in an amount from 0 to 40 wt.%, Calculated on the whole weight of the outer layer.

In addition to the materials discussed above, the composition of the sleeve film may also include conventional auxiliary substances, for example, anti-sticking agents, stabilizers, antistatic agents or softeners. Such excipients are usually added in an amount of from 0.1 to 5 wt.%. In addition, the film can also be dyed in a specific color by the addition of pigments or mixtures thereof.

The sleeve films according to the invention are obtained by coextrusion, for which the individual polymers intended to obtain different layers are plasticized and homogenized in five extruders, and then each of the five polymer melts obtained is fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, receiving an initial sleeve at the head output, which is then subjected to biaxial stretching and heat setting.

The total thickness of the proposed invention in the sleeve film is from 30 to 100 microns, preferably from 50 to 90 microns.

The sleeve films according to the invention, as it was unexpectedly found, are significantly superior to the sleeve films known from DE 4339337 C2 both in terms of weld strength and puncturing strength.

To determine the strength of heat-welded seams, each of the tested sleeve films was welded from the inside perpendicular to the direction of their formation using a laboratory welding machine SGPE 20 from W. Kopp Verpackungsmaschinen. After welding, samples in the form of strips 25 mm wide were cut off from such sleeve films so that the weld was perpendicular to the longitudinal extent of the strip. Then these strips were stretched on an Instron tensile testing machine with a drawing speed of 500 mm / min until the weld severed. The maximum force at which the test film is torn along the weld is indicated below as the strength of the weld.

When testing sleeve films for puncturing, the measure of their piercing strength is the work of fracture.

The fracture work was determined in accordance with DIN 53373, however, in contrast to this standard, a hardened cylindrical rod of form A with a diameter of 3 mm according to DIN EN 28734 was used as a punch at a feed speed during testing of 500 mm / min. The work of destruction corresponds to the energy expended until the first tear appears in the sample.

The sleeve film known from DE 4339337 C2 (comparative example 1) did not lend itself to heat sealing at temperatures of 140 and 200 ° C, while the sleeve films proposed in the invention, heat sealing of which was already possible at a temperature of 140 ° C, had a weld that could rate it satisfactory to good. The strength of the heat-welded joints obtained at a temperature of 200 ° C in the sleeve films proposed in the invention was at least 15% higher than the strength of the welded joints in comparative films.

In the puncturing test, the values of the fracture work obtained for the sleeve films of the invention are also several, respectively, significantly exceeding the values obtained for the comparative films.

Below the invention is described in more detail by examples.

Example 1

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average total thickness of its entire multilayer structure of 0.49 mm. Then this initial sleeve was heated by infrared radiation to 109 ° C and subjected to stretching with a multiplicity of two-dimensional drawing equal to 9.7. The sleeve obtained after such biaxial stretching was thermofixed, pulled together in a double flat film and wound into a roll. The average total sleeve thickness was 50 μm. The width of the sleeve pulled into a double flat film was 209 mm.

Below are the polymers from which the layers were formed on the finished sleeve, and the thickness values of each such layer:

1st layer (outer): polyamide 6, which is a product of Ultramid B4 F company BASF AG, 20 microns 2nd layer: adhesion promoter, which was used as a modified polyethylene, representing the product Admer NF 478 E company Mitsui Chemicals Inc., 5 μm 3rd layer: polyethylene (LDPE), which is a product of Lupolen 1804 N company BASF AG, 10 μm 4th layer: adhesion promoter (similar to the 2nd layer), 5 μm 5th layer (inner): a mixture of 90% polyamide 6/12, which is a product of Grilon CF6S from EMS-Chemie, and 10% polyamide 12, which is a product of UBE Nylon 3030 B from UBE Industries Ltd., 10 μm

When determining the strength of the weld, the following results were obtained:

welding temperature 140 ° C: 7 N / 25 mm

welding temperature 200 ° C: 95 N / 25 mm

When tested for piercing strength, the fracture work 10 was 380 mJ.

Example 2

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average total thickness of its entire multilayer structure of 0.48 mm. Further, this initial sleeve was heated by infrared radiation to 108 ° C and subjected to stretching with a multiplicity of two-dimensional drawing equal to 9.6. The sleeve obtained after such biaxial stretching was thermofixed, pulled together in a double flat film and wound into a roll. The average total sleeve thickness was 50 μm. The width of the sleeve pulled into a double flat film was 209 mm.

Below are the polymers from which the layers were formed on the finished sleeve, and the thickness values of each such layer:

1st layer (outer): polyamide 6/66, representing the product Ultramid C35 company BASF AG, 18 microns 2nd layer: adhesion promoter, which was used as a modified polyethylene, representing the product Admer NF 478 E company Mitsui Chemicals Inc., 6 μm 3rd layer: polyethylene (LDPE), which is a product of Lupolen 1804 N company BASF AG, 10 μm 4th layer: adhesion promoter (similar to the 2nd layer), 6 μm 5th layer (inner): a mixture of 90% polyamide 6/12, which is a product of Grilon CF6S from EMS-Chemie, and 10% of an ionomer resin, which is a product of Surlyn 1652 from Du Font de Nemours GmbH, 10 μm

When determining the strength of the weld, the following results were obtained:

welding temperature 140 ° C: 75 N / 25 mm

welding temperature 200 ° C: 93 N / 25 mm

In the puncture strength test, the fracture work was 455 mJ.

Example 3

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average total thickness of its entire multilayer structure of 0.50 mm. Further, this initial sleeve was heated by infrared radiation to 109 ° C and subjected to stretching with a multiplicity of two-dimensional drawing equal to 10.0. The sleeve obtained after such biaxial stretching was thermofixed, pulled together in a double flat film and wound into a roll. The average total sleeve thickness was 50 μm. The width of the sleeve pulled into a double flat film was 210 mm.

Below are the polymers from which the layers were formed on the finished sleeve, and the thickness values of each such layer:

1st layer (outer): polyamide 6/66, representing a product of Ultramid C35 from BASF AG, 20 μm 2nd layer: adhesion promoter, which was used as a modified polyethylene, representing the product Admer NF 478 E company Mitsui Chemicals Inc., 5 μm 3rd layer: polyethylene (LLDPE), which is a Dowlex 2049 E product from DOW Chemical Company, 10 μm 4th layer: adhesion promoter (similar to the 2nd layer), 6 μm 5th layer (inner): a mixture of 85% polyamide 6/12, representing the product of Grilon CF6S from EMS-Chemie, 5% polyamide 6I / 6T, representing the product of Grivory G21 from EMS-Chemie, and 10% of the ionomer resin, representing the product of Surlyn 1652 from Du Pont de Nemours GmbH, 9 μm

When determining the strength of the weld, the following results were obtained:

welding temperature 140 ° C: 12 N / 25 mm

welding temperature 200 ° C: 96 N / 25 mm

In the puncture strength test, the fracture work was 460 mJ.

Comparative Example 1

According to DE 4339337 C2, a five-layer sleeve film was produced which had the following structure:

1st layer (outer): a mixture of 95% polyamide 6, which is a product of Durethan B40 F from Bayer AG, and 5% polyamide 6I / 6T, which is a product of Grivory G21 from EMS-Chemie, 20 μm 2nd layer: adhesion promoter, which was used as a modified polyethylene, representing the product Admer NF 478E company Mitsui Chemicals Inc., 4 μm 3rd layer: polyethylene (LLDPE), which is a product of Dowlex 2049 E company DOW Chemical Company, 14 μm 4th layer: adhesion promoter (similar to the 2nd layer), 4 μm 5th layer (inner): a mixture of 95% polyamide 6, which is a product of Durethan B40 F from Bayer AG, and 5% polyamide 6I / 6T, which is a product of Grivory G21 from EMS-Chemie, 8 microns

When determining the strength of the weld, the following results were obtained:

welding temperature 140 ° С: the film did not give in to welding

welding temperature 200 ° C: the film could not be welded

When tested for piercing strength, the fracture work was 315 mJ.

Reference Example 2

Analogously to example 1, a five-layer sleeve film was made, with the only difference being that pure 6/12 polyamide, which is a product of Grilon CF6S from EMS-Chemie, was used to form the 5th layer (inner).

When determining the strength of the weld, the following results were obtained:

welding temperature 140 ° C: 35 N / 25 mm

welding temperature 200 ° C: 81 N / 25 mm

In the puncture strength test, the fracture work was 375 mJ.

Example 4

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average thickness of its entire multilayer structure of 0.49 mm. Further, this initial sleeve was heated by infrared radiation to 110 ° C and stretched with a stretch ratio of 9.7. The sleeve obtained after such biaxyl stretching was thermofixed, pulled together in a flat film and wound into a roll. The average total sleeve thickness was 50 μm, and the width of the sleeve drawn into a flat film was 209 mm.

Below are the polymers from which the finished sleeve and its thickness values for each layer were formed:

1st layer (outer): polyamide 6, which is a product of Ultramid B4F, Fa. BASF AG, 18 μm 2nd layer: adhesion promoter, which was used as a modified polyethylene, representing the product Admer NF 478 E, Fa. Mitsui Chemicals Inc., 6 μm 3rd layer: polyethylene (LDPE), which is a product of Dowlex 2049 V, Fa. DOW Chemical Company, 10 μm 4th layer: adhesion promoter (like layer 2), 6 μm 5th layer (inner): a mixture of 90% polyamide 6/99, which is a product of Grilon CF62BS, Fa. EMS Chemie, and 10% ionomer resin, product of Surlyn 1652, Fa. DuPont de Nemours GmbH, 10 μm

The following heat seal weld strength was determined:

Welding temperature 140 ° C: 32N / 25mm

Welding temperature 200 ° C: 96 N / 25 mm

In the puncture strength test, the fracture work was 390 mJ.

Example 5

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average thickness of its entire multilayer structure of 0.48 mm. Further, this initial sleeve was heated by infrared radiation to 109 ° C and stretched with a stretch ratio of 9.6. The sleeve obtained after such biaxyl stretching was thermofixed, pulled together in a flat film and wound into a roll. The average total sleeve thickness was 50 μm, and the width of the sleeve drawn into a flat film was 210 mm.

The following are the polymers from which the finished sleeve and its thickness values for each layer were formed:

1st layer (outer): polyamide 6, representing a product of Durethan B40 F, Bayer AG, 20 μm 2nd layer: adhesion promoter, which was used as a modified polypropylene, representing the product Admer QF 580 E, Fa. Mitsui Chemicals Inc., 5 μm 3rd layer: a polypropylene copolymer representing the product Appryl 3020 GN 3, Fa. Appryl S.N.C., 10 μm 4th layer: adhesion promoter (like layer 2), 5 μm 5th layer (inner): a mixture of 90% polyamide 6/12, which is a product of Grilon CF6S, Fa. EMS Chemie, and 10% ethylene acrylic acid copolymer, Primacor 1320, DOW Chemical Company, 10 μm

The following heat seal weld strength was determined:

Welding temperature 140 ° C: 71 N / 25 mm

Welding temperature 200 ° C: 98 N / 25 mm

In the puncture strength test, the fracture work was 350 mJ.

Example 6

Separate polymers intended for various layers were plasticized and homogenized in five extruders. Then, each of the five obtained polymer melts was fed in a separate stream to an extrusion die designed to form five layers with the required thickness of each of them, obtaining an initial sleeve at the outlet of the die, which was then subjected to biaxial stretching and heat setting. The diameter of such an initial sleeve was 45.5 mm with an average thickness of its entire multilayer structure of 0.50 mm. Further, this initial sleeve was heated by infrared radiation to 110 ° C and stretched with a stretch ratio of 10.0. The sleeve obtained after such biaxyl stretching was thermofixed, pulled together in a flat film and wound into a roll. The average total sleeve thickness was 50 μm, and the width of the sleeve drawn into a flat film was 209 mm.

Below are the polymers from which the finished sleeve and its thickness values for each layer were formed:

1st layer (outer): a mixture of 80% polyamide 6/66, representing the product Ultramid C35, Fa. BASF AG and 20% copolymer of ethylene and vinyl alcohol, representing the product EVAL EP H101, Fa. Kuraray Co., 16 μm 2nd layer: adhesion promoter, which was used modified polyethylene, which is a product of Admer NF 478 E, Fa. Mitsui Chemicals Inc., 6 μm 3rd layer: polyethylene (LDPE), which is a product of Dowlex 2049 E, Fa. DOW Chemical Company, 12 μm 4th layer: adhesion promoter (like layer 2), 6 μm 5th layer (inner): a mixture of 90% polyamide 6/69, which is a product of Grilon CF62BS, Fa. EMS Chemie, and 10% ionomer resin, product of Surlyn 1652, Fa. DuPont de Nemours GmbH, 10 μm

The following heat seal weld strength was determined:

Welding temperature 140 ° C: 28 N / 25 mm

Welding temperature 200 ° C: 94 N / 25 mm

In the puncture strength test, the fracture work was 410 mJ.

Claims (21)

1. A multilayer, preferably five-layer, biaxially elongated, shrinkable heat sealable sleeve film used as a packaging and casing for meat, meat with bones or pasty food products, characterized in that it consists of an inner layer formed of at least one copolyamide and at least one amorphous polyamide, and / or at least one homopolyamide, and / or at least one modified polyolefin, middle polyolefin layer and outer layer, formed from at least one homopolyamide and / or at least one copolyamide and / or at least one copolymer of ethylene and vinyl alcohol and / or a modified polyolefin, as well as from two layers formed from an adhesion promoter, which preferably serves the same material, and located respectively between the inner layer and the middle layer and between the middle layer and the outer layer. 2. The sleeve film according to claim 1, characterized in that the copolyamides that make up the inner layer are obtained from monomers selected from the group consisting of caprolactam, laurinlactam, ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid, decandicarboxylic acid , dodecandicarboxylic acid, terephthalic acid, isophthalic acid, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, octamethylene diamine and xylylenediamine. 3. The sleeve film according to claim 2, characterized in that the content of copolyamides in the inner layer is from 50 to 95 wt.%. 4. The sleeve film according to any one of claims 1 to 3, characterized in that the inner layer contains amorphous polyamides, the glass transition temperature of which in the dry state is from 50 to 200 ° C. 5. The sleeve film according to claim 4, characterized in that the glass transition temperature of amorphous polyamides is preferably from 90 to 160 ° C. 6. The sleeve film according to any one of claims 1 to 5, characterized in that the inner layer contains homopolyamides obtained from monomers selected from the group consisting of caprolactam, laurinlactam, ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid, decandicarboxylic acid, dodecandicarboxylic acid, terephthalic acid, isophthalic acid, tetramethylenediamine, pentamethylenediamine, hexamethylene diamine, octamethylene diamine and xylylenediamine. 7. A sleeve film according to any one of claims 1 to 6, characterized in that the inner layer contains modified polyolefins, which are copolymers of ethylene or propylene and optionally other linear α-olefins containing from 3 to 8 C atoms, with α, β-unsaturated carboxylic acids, preferably with acrylic acid, methacrylic acid, and / or their salts with metals, and / or their alkyl esters, or the corresponding graft copolymers of these monomers grafted onto polyolefins, or partially saponified ethylene-wine copolymers acetate, which are optionally grafted with α, β-unsaturated carboxylic acid and are characterized by a low degree of saponification, or mixtures thereof. 8. The sleeve film according to any one of claims 1 to 7, characterized in that the amount of each of the other components that make up the inner layer, which are amorphous polyamide, homopolyamide and a modified polyolefin, is from 1 to 30 wt.%, Preferably 5 to 25 wt.%, In terms of the entire mass of the inner layer. 9. A sleeve film according to any one of claims 1 to 8, characterized in that the polyolefin middle layer is formed from homopolymers of ethylene or propylene and / or copolymers of linear α-olefins containing from 2 to 8 C atoms. 10. The sleeve film according to claim 9, characterized in that the polyolefins from which the middle layer is formed are preferably linear low density polyethylene, high density polyethylene, polypropylene homopolymers, polypropylene block copolymers and random polypropylene polymers. 11. The sleeve film according to any one of claims 1 to 10, characterized in that both layers of the adhesion promoter are formed from functional polyolefins modified by functional groups. 12. The sleeve film according to claim 11, characterized in that the modified polyolefins are modified homo- or copolymers of ethylene and / or propylene and optionally other linear α-olefins with 3-8 C atoms, containing grafted monomers selected from groups of α, β-unsaturated dicarboxylic acids, such as maleic acid, fumaric acid, itaconic acid, or their anhydrides, esters, amides or imides. 13. The sleeve film according to claim 11, characterized in that the modified polyolefins included in both layers of the adhesion promoter are copolymers of ethylene or propylene and optionally other linear α-olefins containing from 3 to 8 C atoms, with α, β-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and / or their salts with metals and / or their alkyl esters or the corresponding graft copolymers of these monomers grafted onto polyolefins, or partially saponified ethylene-vinyl copolymers ata, which is optionally subjected to graft copolymerization with the α, β-unsaturated carboxylic acid and have a low saponification level, or mixtures thereof. 14. A sleeve film according to any one of claims 1 to 13, characterized in that the outer layer is formed from a mixture containing at least one homopolyamide and / or at least one copolyamide obtained from monomers selected from the group consisting of caprolactam, laurinlactam , ω-aminoundecanoic acid, adipic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecandicarboxylic acid, terephthalic acid, isophthalic acid, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine diamide endiamine. 15. The sleeve film according to 14, characterized in that the composition of the outer layer in addition to homopolyamide and / or copolyamide also includes a modified polyolefin, which are copolymers of ethylene or propylene and optionally other linear α-olefins containing from 3 to 8 C- atoms, with α, β-unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, and / or their metal salts and / or their alkyl esters, or the corresponding graft copolymers of these monomers grafted onto polyolefins, or partially saponified e copolymers of ethylene with vinyl acetate, which are optionally grafted with α, β-unsaturated carboxylic acid and are characterized by a low degree of saponification, or mixtures thereof. 16. The sleeve film according to 14, characterized in that the composition of the outer layer in addition to homopolyamide and / or copolyamide also includes a copolymer of ethylene and vinyl alcohol, while ethylene in its copolymer with vinyl alcohol accounts for from 27 to 48 mol %, preferably from 27 to 38 mol%. 17. The sleeve film according to any one of paragraphs.14-16, characterized in that the share of the modified polyolefin and / or copolymer of ethylene and vinyl alcohol is in each case from 0 to 40 wt.% In terms of the entire mass of the outer layer. 18. The sleeve film according to any one of claims 1 to 17, characterized in that it is a coextruded and biaxially elongated sleeve film subjected to heat setting. 19. A sleeve film according to any one of claims 1 to 8, characterized in that its thickness is from 30 to 100 microns, preferably from 50 to 90 microns. 20. A package, characterized in that it is made of a sleeve film according to any one of claims 1 to 19 by welding or heat sealing of its inner layer with itself. 21. The package according to claim 20, characterized in that it is used as packaging for pasty foods, meat or meat with bones.