FR2541181A1 - POLYOLEFIN THERMORETRACTABLE MULTILAYER FILM - Google Patents

Abstract

THE INVENTION RELATES TO A HEAT-SHRINKABLE MULTI-LAYER POLYOLEFIN FILM. ACCORDING TO THE INVENTION, IT HAS A SOUL LAYER WHICH INCLUDES A LINEAR POLYETHYLENE AND TWO SKIN LAYERS INCLUDING AN ETHYLENE-VINYL ACETATE COPOLYMER, AND THE FILM HAS AN EXTENSION TOWARDS THE MACHINE OF AT LEAST ABOUT 189 AND A CROSS-DIRECTIONAL ELONGATION OF AT LEAST ABOUT 129; AT ABOUT 185C, THE FILM HAS A FREE MACHINE-DIRECTIONAL SHRINKAGE OF AT LEAST 19 AND A FREE CROSS-DIRECTIONAL SHRINKAGE OF AT LEAST 22. THE INVENTION APPLIES IN PARTICULAR TO THE PRODUCTION OF PACKAGING FILMS .

Description

This invention relates to dandruff

  heat-shrinkable and thermoplastic packaging.

  In particular, the present invention is directed to retractable films using linear low density polyethylene or linear medium density polyethylene resins as a component of a

  core layer in a multilayer film.

  The present invention is directed to new

  useful formulas of heat-shrinkable films.

  A feature distinguishing a shrink wrap is the ability of the film, upon exposure to a certain temperature, to shrink or, if it is

  prevented from shrinking, producing a tension of

curing in the film.

  The manufacture of shrink films, as is well known, can generally be accomplished by extrusion of soft materials which have been heated to their pour point or melt from an extrusion die in tubular or planar form (sheet) After post-extrusion quenching for cooling, the extrudate is then warmed to its orientation temperature range. The orientation temperature range for a given film will vary with the different resinous polymers and their film-forming mixtures. Orientation temperature range can generally be reported as being above ambient temperature and below the melting point of the film. The orientation temperature range for a given film can easily be determined by a skill

  ordinary in the art, without undue experimentation.

  The terms "oriented" or "orientation" are used herein to describe the processes and characteristics of the resulting product obtained by stretching and immediate cooling of a resinous polymeric material which has been heated to its orientation temperature range. in order to revise the molecular configuration of the material by physical alignment of the molecules to improve the mechanical properties of the film such as, for example, the narrowing tension and stress relaxation d-Lorientation These two properties can be mpoured Q according to the American standard ASTM D 2838-69 (re-approved in 1975) When the drawing force is applied in one direction, the result is a uniaxial orientation. When the drawing force is applied in two directions, the result is a biaxial orientation.

  used interchangeably with "heat shrink

  These terms refer to a material which has been stretched and maintained by cooling to its dimensions

  "Oriented material" (that is, heat shrink

  table) will tend to return to its original unstretched dimensions when heated to an appropriate temperature below its temperature range.

fusion -

  Referring again to the basic process for

  the manufacture of film as described above

  above, it can be seen that the film once extruded and initially quenched for cooling is then reheated to its orientation temperature range and is oriented. The draw for orientation can be accomplished in many ways such as, for example, by These terms are well known and indicate orientation steps where the material is stretched in a cross-directional or cross-sectional direction.

  (TD) and / or in longitudinal direction or machine (MD).

  After being stretched, the film is quickly quenched to cool, and thus maintain or

  take the molecular oriented configuration.

  After maintaining the oriented molecular configuration, the film can then be rolled and used for very tight packaging of a wide variety of articles.

  pack is first enclosed in the heat shrink material

  The film itself is subjected to high temperatures, for example, by passing the product through a hot-air or hot-water tunnel. This causes the film to shrink from the shrink film itself when necessary. shrink around the product to produce a tight wrap that conforms very precisely to the product outline. The above general pattern of film making is not fully described, as this process is well known to those skilled in the art. For example, US Pat. Nos. 4,247,400, 4,229,241, 419,4039, 4,388,443, 40,448,428; 3821182; 3022543 These patents are indicated

here for reference.

  Many variations of the general treatment theme described above are available to those who are competent depending on the end use for which the film is intended and the characteristics that it is desired to give it. For example, the molecules of the film may be crosslinked. during treatment to improve the resistance to film breaking and other characteristics Crosslinking and cross-linking methods are well known Crosslinking

  can be accomplished by irradiating the film or

  it can be accomplished chemically by using

peroxides.

  The radiation doses are given here in terms of the "jdd" radiation unit, with one million rads or a megarad designated "M rd". The degree of molecular crosslinking is expressed in terms of the radiation dose that induces cross-linking. "Radiation" as used herein generally means ionizing radiation such as X-rays, gamma-rays, and electrons that directly induce molecular cross-linking. (However, when used in conjunction with dispersive agents dispersed in a material, heat and light can be considered as

  forms of radiant energy inducing crosslinking).

  Electrons are the preferred form of radiant energy and they are preferably produced by accelerators marketed between 0.5 and 2.0 me V. Another possible variant of treatment is the application of a fine fog of a jet of silicone inside the freshly extruded material for

  improve the greater ability to process the material.

  One method for accomplishing such internal application is disclosed in European Patent Application No. 82,303,495, published February 9, 1983, under EP publication No. 00 713 49 A2. Alternatively, an anti-fog agent may be applied to the The anti-fog agents have also been found to be of beneficial use in improving the processability. In addition to the materials disclosed in European Patent Application No. 082303 495, materials have demonstrated the ability to eliminate the internal ribbon weld

an extended tube.

  The family of polyolefins and, in particular, the family of polyethylenes for retractable films has a wide range of physical characteristics and performance such as the shrink force (the amount of force a film exerts per unit

  surface of its cross-section during shrinkage

  the degree of free shrinkage (the linear dimension reduction in a specified direction that a material undergoes when subjected to high temperatures while not retained), the tensile strength (the highest strength that can be applied to a unit of film surface before it begins to tear) sealability

  shrinkage temperature (the shrinkage

  temperature), tear initiation and tear resistance (the strength at which a film will begin to tear and continue to tear), the optical properties (gloss, veil and transparency of the material), and the dimensional stability (the ability of the film to retain its original dimensions under different types of storage conditions) The characteristics of the film play an important role in the choice of a film

  particular and they differ for each type of application

  packaging packaging and for each package Consider the size of the product, its weight, shape, stiffness, the number of components of the product, other packaging materials that can be used with the film and the packaging. type of packing equipment

available.

  Given the many physical characteristics described above that are associated with polyethylene film and more in view of the many applications with which these films have already been associated and those with which they will be associated in the future, it is easy to discern that the need for improvement of all or part of the above described physical characteristics of

  these dandruff is strong and naturally goes ahead.

  Accordingly, it is a general object of the present invention to provide a heat-shrinkable polyo-olefin film capable of forming an improvement by

  compared to film already used in the prior art.

  It is another object of the present invention to provide a polyolefin film having improved bursting property. The present invention further provides a polyolefin film having a high elongation. According to another object of the invention, there is provided an improved shrink film made of polyolefin having

better optical qualities.

  Another object of the present invention is a polyolefin shrink film having a wide range of

shrinkage temperatures.

  Another object of the present invention is an improved shrink film of polyolefin having

  better sealability

  Another object of the present invention is a polyolefin shrink film having

  improved resistance to tear propagation.

  Another object of the present invention is a polyolefin shrink film having improved

machinability.

  Another object of the present invention is an improved retractable polyethylene film using either a linear low density polyethylene or a linear medium density polyethylene

  as a constituent of a core layer.

  Another subject of the present invention is a process

  advanced film manufacturing.

  These objects and others are affected by the

  retractable polyolefin film which is disclosed herein.

  Unless specifically indicated and defined or limited, the terms "polymer" or "polymer resin" used herein generally include homopolymers, copolymers, terpolymers, polymers, and the like.

  sequences, grafted, alternate gt statistics.

  The polyolefin or polymer or polymers of

  The terms used herein include not only unsaturated aliphatic hydrocarbon polymers of the general formula CNH 2 N but also copolymers of olefins with other monomers such as ethylene and acetate.

of vinyl.

  The term "melt flow" used herein or "melt flow index" is the grammage amount of a thermoplastic resin that can be forced through a given orifice under pressure and temperature. specified, in ten minutes, like this

  is described in US ASTM D 1238.

  The term "core" or "core layer" as used herein means a layer in a multilayered film

  which is surrounded on both sides by additional layers.

  The term "skin" or "skin layer" as used herein means an outer layer (i.e., surface) of a

multilayer film.

  The term "low density polyethylene" (LDPE) used herein denotes homopolymers of ethylene having a density of 0.910 to 0.925. The term "linear low density polyethylene" (LLDPE) used herein indicates an ethylene copolymer and 8% There is less butene, octene or hexene having a density of 0.910 to 0.925 and the molecules comprise long chains with little or no branching or crosslinked structures. The term linear polyethylene of density The LMDPE used herein indicates a copolymer of ethylene oxide of less than 8% butene, octene or hexene having a density of 0.926 to 0.940 and where the molecules include long chains with little or no The term "ethylene-vinyl acetate copolymer" (EVA) as used herein refers to a copolymer of monomer ethylene and divinyl acetate, wherein the units derived from ethylene are present in major quantities and derived units

  vinyl acetate are present in minor amounts.

  The preferred ethylene-vinyl acetate copolymers are those having 212% units derived from the acetate

of vinyl.

  The term "gauge" used idi indicates the thickness dimension of a 100 gauge film is equal to 0.025 mm. The term "draw ratio" as used herein indicates the ratio of expansion (i.e., stretching), during the orientation of a film. For example, a draw ratio of four (4) or four ( 4) to one (1) will mean that the film has been stretched to four times its size

  not stretched originally during orientation.

  It has been found that a flexible, heat-shrinkable and thermoplastic packaging film having a desirable combination of physical characteristics such as shrinkage tension, optical characteristics, cutability, sealability, shrinkage temperature range and resistance to

  tear was obtained by the thermal film

  This multilayer film has a core layer which comprises a linear low density linear or linear density polyethylene resin. A preferred three layer embodiment comprises, in addition to the identified above layer of "soul", two layers

  each comprising a copolymer of ethylene-

  vinyl acetate Preferably, the multi-layer film

  layer is irradiated It is also better

  to direct the film so that it is thermo-

  retractable in at least one direction.

  The multilayer film may be combined with other polymeric materials for specific applications. For example, relatively thin layers may be added on one or both sides of the preferred three-layer base structure, to improve joint strength or to lower the

  permeability to gases and moisture.

  The present invention also relates to a

  an improved process for making the film.

  An important aspect of the improved process is the use of draw ratios between 2.5 and 4.2 to 1 in the transverse direction and 2.5 to 4.2 in the longitudinal direction. The present invention will be better understood and other purposes, details, features and advantages thereof will become more clearly apparent in the course of

  explanatory description which will follow made reference

  to the accompanying schematic drawings given solely by way of example illustrating several embodiments of the invention and in which: Figure 1 is a cross-sectional view of a preferred embodiment with three layers according to the invention; and FIG. 2 is a schematic representation of a preferred method of manufacturing the film of the

present invention.

  Referring to FIG. 1, which is a cross-sectional view of a preferred three-layer embodiment of the present invention, it can be seen that this embodiment comprises a core layer 2 and skin layers 1 and 3 A thickness ratio of the three 1/2/1 layers is shown in FIG. 1 However, the thickness of each skin layer may be between 10 and 30% of the total thickness of the film, as well as the thickness of the layer of the soul can be understood

  between 40 and 80% of the total thickness of the film.

  A preferred component of the core layer 2 comprises

  a low density linear polyethylene polymer.

  However, a medium density linear polyethylene polymer can be substituted as a constituent of the core layer, without any appreciable change in characteristics.

of the final film produced.

  LLDPE is used herein as an abbreviation for low density linear polyethylene as defined above. LMDPE is used herein as an abbreviation for a linear medium density polyethylene as defined above. Nosex experiences have revealed that a particularly preferred core layer formulation included

  essentially a linear low density polyethylene.

  This material can be obtained at the Dow Chemical Company under

  the Dow X 2045 trade designation.

  Referring again to Figure 1, and more particularly to skin layers 1 and 3, the experiments also determined that a particularly preferred skin layer formulation comprised essentially an ethylene-vinyl acetate copolymer. The material can be obtained from the bridge firm under the designation Elvax 3128 Elvax 3128 is a copolymer of ethylene and vinyl acetate having from 8.4 to 9.4% vinyl acetate having a 2. Alternatively, the material can be obtained from the company El Paso (previously Rexen) under the name PE 204-C 595 PE 204-C 595 is a copolymer of ethylene and vinyl acetate having 3.3 to 4.1% vinyl acetate, having a melt index of 2.0

  + 0.5 and a density of 0.9232-0.9250.

  Throughout this description, all

  percentages are percentages by weight.

  Throughout the description, all references

  the density is in g / cc at 230 ° C. In summary, experience has determined that a particularly preferred embodiment of the present invention comprises a core layer consisting essentially of low density linear polyethylene and layers

  of skin consisting essentially of a copolymer of ethylene-

vinyl acetate.

  Although the above-described three-layer formulas are generally preferred over structures having more than three layers for reasons of economy of manufacture, various five-layer formulas have also been produced which are also satisfactory. However, the cost of manufacturing a five-layer film is generally higher than that of

three layers.

  Those skilled in the art will readily recognize that all weight percentages revealed

  above may be subject to slight variations.

  In addition, these percentages may vary slightly as a result of the inclusion or application of additives such as silicone fog and antifoggants.

  described above or slip and antiblocking agents.

  A preferred antiblocking agent is silica which is commercially available

  The preferred slip agents are Erucamide (marketed by Humlco Chemical under the trade name Kemamide E), and Stearamide (marketed by Humko Chemical Company under the trade name Kemamide S) and NN '- dioleoylethylenediamine (marketed by Glyco Chemical under the trade name Acrawax C) A preferred silicone fog is a liquid polyorganosiloxane manufactured by General Electric under the designation General Electric SF 18 polydimethylsiloxane. The general ranges for the application of these additives are as if: (1) Silica: 250 3000 ppm (2) Acrawax C: 200 4000 ppm (3) Erucamide: 200 5000 ppm (4) Stearamide: 200 5000 ppm

  (5) Silicone fog: 5.38 mg / m and more.

  In this description, the term "consistent

  essentially "is not intended to exclude slight variations in percentage or additives and agents of

this kind.

  Additional layers of polyolefin and / or minor amounts of additives of the types described above may be added to the three-layer structure of the present invention if desired, but care must be taken not to adversely modify. the desirable properties of tensile stress, shrinkage, optical and other characteristics of

  the multilayer film of the present invention.

  In the preferred method for producing the low density or linear density linear low density linear polyethylene shrink film of the present invention, the basic steps are to mix the polymers for the various layers, coextrude the layers to form a multilayer film.

  then stretch the film to orient it biaxially.

  These additional steps and desirable steps will be

  explained in detail in the following paragraphs.

  The process begins with mixing the raw materials (i.e., the polymeric resins) to the desired proportions and ranges as described above. The resins are usually purchased from a pellet supplier and can mix them in one of the many mixers marketed as is well known During the mixing process, any additive and / or agent that one wishes to use are

also incorporated.

  The mixed resins as well as the additives and / or applicabl E agents are then fed into the hoppers of the extruders which feed the coextrusion die. For the three-layer film, at least three extruders must be used if each layer must have a composition. Different extruders receive the desirable materials for the inner and outer skin layers and the other extruder receives the linear polyethylene of

  low or medium density that is desired for use

  in the core layer Extruders

  may be used, if desired.

  Preferably, the materials are coextruded as a tube having a diameter. The final diameter of the coextruded film will depend on the original diameter of the extruded tube and the draw ratio subsequently applied. The coextruded tube is relatively thick-and is called "tape." Circular or tubular coextrusion dies are well known and can be purchased from a number of manufacturers. In addition to bead coextrusion, slot dies can be used to coextrude the material. in planar form Well known extrusion coating methods of one or more layers can also be employed if

we wish it.

  A further step in the method that can be used is to irradiate the ribbon or unexpanded tube or sheet by electron bombardment.

  high energy from an accelerator to re-

  The crosslinking strongly increases the structural strength of the film or the force at which the material can be stretched before tearing when the film materials are predominantly ethylene such as polyethylene or polyethylene. ethylene-vinyl acetate Irradiation also improves the optical properties of the film and changes the properties of the film at higher temperatures. If an irradiation step is employed, a preferred dose of irradiation is between 0.5 Mrd and 12, O Mrd Mrd is the abbreviation for megarad A megarad represents 1 x 106 rads, one rad being the amount of ionizing radiation resulting in the absorption of 100 ergs of energy per gram of irradiated material regardless of the source of radiation In some cases, it may be desirable to stretch the multilayer film first and then irradiate it or if a sequential coating l is used, a layer or group of layers

41181

  can be irradiated and then another layer or more layers can be added before the final stretching and orienting step. As noted above, an optional additional step of the method is to apply a fine silicone mist to the interior of the newly extruded ribbon. Details of this step are disclosed in US Patent Application No. 289 018 filed

  July 31, 1981 and incorporated herein by reference.

  Following coextrusion, quenching to cool and if desired to eradicate, the

  extruded ribbon is heated again and is continuously

  It is then inflated by internal air pressure into a bubble to thereby convert the narrow, thick-walled ribbon into a thin-walled thin film having the desired thickness for the film. This process is sometimes referred to as a bubble bubble trapping technique. "stretching" After stretching, the bubble is then deflated

  and the film is wound on semi-finished rolls.

  The stretching process directs the film, stretching it transversely and, at a certain point, longitudinally to repack the molecules and thereby impart shrinkage capabilities to the film and modify its physical characteristics. Additional stretching in the longitudinal direction or machine can be accomplished by rotating deflating rollers that assist in slumping the "bubble puff" at a greater speed than the rollers that are used to carry the heated "ribbon" to the draw or bubble zen All these methods

orientation are well known.

  It has now been found that stretching ratio utilization of 2.5 and 4.2 transverse and 2.5 to 4.2 longitudinally results in films having lower degrees of orientation with better physical characteristics such as, for example, better elongation in

  measuring according to American standard ASTM 882.

  To better reveal and clarify the framework of

  the invention can be found in the examples which follow.

EXAMPLE 1

  A three-layer structure having an approximate 1/2: 1 layer thickness ratio was extruded feeding four extruders. The extruders NO 52 and 3 which fed the die orifice for the core layer were provided with linear density polyethylene with a density of 100% E Dow X 2045 (density 0.920, melt index 1.00 o Each extruder N s 1 and 4 fed a die orifice for a layer of skin

  and both provided a copolymer of ethylene-

  100% vinyl acetate having 3.3-4.1% vinyl acetate LPE 204 C 595 (density 0.9232 0.9250, melt index 2.0 + 0.5) The temperature of the extruder N 1 was set between 177 and 190 ° C. The extruder N 2 was maintained at a temperature range of 218 ° to 25 ° C. The extruder N 3 was maintained at a temperature range of 218 ° to 257 ° C. and the extruder N 4 was maintained at a temperature of 177 to 191 C The circular die was

  maintained at a temperature of the order of 204 C.

  The ribbon was extruded at 16.15 m / min.

  After extrusion of the layers through the 15.24 cm circular die orifice, the tubular extrudate which had a ribbon thickness of about 0.23 mm and a tubular width of about 14.29 cm was quenched to

  cool it by passing through a cold water bath.

  During extrusion of the ribbon, a thin silicone mist was applied to the inside of the extruded tube at 64.6 mg / m. The ribbon was then rolled up. irradiation at about 20.7 m / min to achieve a irradiation level of 6 mbar The radially extruded extrudate was then warmed to direct it by passage through a heating zone or furnace. Then, the film was cooled by quenching. with water to block the oriented molecular structure The final thickness of the film

was of a gauge of about 75.

EXAMPLE 2

  The compositions used were the same as in Example 1.

  All parameters were the same as in Example 1 except that the ribbon was extruded at 20.7 m / min and was 0.152 mm thick. The ribbon was transversely stretched at a ratio of 3.6. at 1 and longitudinally at a ratio of 3.14 to 1 The thickness

  The final film was 50 gauge.

EXAMPLE 3

  A three-layer structure having an approximate 1/4: 1 layer thickness ratio was extruded by feeding four extruders. No. 2 and No. 3 extruders which fed the die port for the core layer received linear polyethylene. Low density 100% lDow X 2045 (0.920 density, melt index 1, o). The extruders 1 and 4 each fed a die orifice for one skin layer and both received an ethylene-vinyl acetate copolymer. at 100% having 8.4 9.4% vinyl acetate

  and a melt flow of 2 + 0.2.

  The temperature of the extruder No. 1 was established between 177 and 1900 ° C. The extruder NO 2 was established between 218 and 2460 ° C. The extruder N 03 was established between 218 and 2570 ° C. The extruder NO 4 was established between 177 and 1900 C. The circular die was established at a temperature of 2040 C. After extrusion of the layers through the orifice of the 15.2 cm circular die, the extrudate which had a thickness of ribbon About 0.23 mm and a tubular width of 14.29 cm was quenched to cool by passing through a cold bath at about 14.63 m / min. Upon extrusion of the ribbon, a fine mist of silicone was applied inside the extruded tube

Because of 96.88 mg / m 2.

  The tube was then passed through an irradiation unit at about 14.63 m / min and irradiated at

a rate of 6 Mrd.

  The irradiated tube was then reheated to direct it through a heating zone or furnace. After heating, the tubular estruda was stretched transversely at a ratio of about 3: 7 to 1 and stretched longitudinally at about 4.2 to 1 Then the film was cooled by quenching with water to lock the orientation The final gauge of the film

was 75.

  The data obtained during the testing of these

  Materials are shown in Table I below.

TABLE I.

  Example I II III Layer Ratio 1/2/1 1/2/1 1/4/1 Tensile Strength (105 Pa)

MD 956-845-892

TD 2 1080 1104 1055

Lengthening (%)

MD 202 194 189

TD 5 3 129 179 197

Module (10 Pa)

MD 1772 1620 1558

TD 1779 1655 1455

Propagation of the tear (g)

MD 9.25 4.31 7.00

TD 4.31 2.81 8.38

Tear resistance (N)

MD 2.85 2.27 3.38

TD 3.07 1.96 3.83

  Ball burst at 23 C Sphere 12.7 mm in diameter (N-cm) 148 101 202 Shrinkage properties at 85 C Free shrinkage (%) 6

MD 20 19 22

TD 22 22 24

  Shrinkage tension 5 7 (10 Pa)

MD 21.37 16.20 23.17

TD 27.92 30.96 25.72

at 118 C

Free shrinkage (%)

MD 65 63 63

TD 67 68 63

  Shrinkage tension 5 7 (10 Pa)

MD 20.27 12.75 22.62

TD 8 26.48 24.96 22.75

  Optical properties Sailing (%) 0.9 1.2 0.7 Gloss (45%) 95 94 94 Total transmission 92.6 92.6 92.8 Notes from Table I.

1 ASTM D 882

2 ASTM D 882

3 ASTMD 882

4 ASTM D 1938

ASTM D 1004

6 ASTM D 2732

ASTM D 2838

8 ASTM D 1003

  In Table f above, the data are averages obtained by ASTM process

designated.

  For the implementation of the method according to the invention, use is made of an installation comprising an extrusion unit 1, an inventory unit 2, a dirradiation unit 3, another inventory unit 4, and a stretching machine 5; in addition, reference numeral 6 denotes a water ring, 7 a cold bath, 8 the extruded ribbon, 9 the film bubble,

  the film winder and the cooled air ring.

Claims (14)

  A multilayer heat-shrinkable polyolefin film, characterized in that it has a core layer comprising a linear polyethylene and two skin layers comprising an ethylene-vinyl acetate copolymer, said film having an elongation toward the machine of at least 189% and a transverse elongation of at least about 129%, and at about C, said film has a free shrinkage towards the machine of at least about 19% and a shrinkage   free in transverse direction of at least about 22%.   2 multilayer film according to claim 1, characterized in that it comprises a core layer   formed of a low density linear polyethylene.   3 multilayer film according to claim 1, characterized in that it comprises a forged core layer of a   linear polyethylene of medium density.   4 multilayer film according to any one of   of the preceding claims characterized in that   comprises a crosslinked core layer.   Multilayer film according to Claim 4, characterized in that it consists of the layers of the aforementioned soul and skin.   6 multilayer film according to claim   4, characterized in that the above-mentioned copolymer of ethylene-   vinyl acetate comprises from 2 to 12% vinyl acetate.   Multilayer film according to claim   4, characterized in that the above-mentioned copolymer of ethylene-   vinyl acetate comprises 3.3 to 4.1% vinyl acetate.   8 multilayer film according to claim   4, characterized in that the aforementioned copolymer of ethylene-   vinyl acetate comprises from 8.4 to 9.4% vinyl acetate.   9 multilayer film according to claim 4, characterized in that it has been soldered with 0.5 to 12.0 Mrd. Multilayer film according to the claim, characterized in that the ethylene-acetate copolymer   said vinyl comprises 2 to 12% vinyl acetate.   Multilayer film according to Claim 5, characterized in that the above-mentioned copolymer of ethylene-   vinyl acetate comprises 3.3 to 4.1% vinyl acetate.   12 multilayer film according to claim, characterized in that the above-mentioned copolymer of ethylene-   Devinyl acetate comprises from 8.4 to 9.4% vinyl acetate.   13 multilayer film according to claim, characterized in that it has been irradiated with 0.5 to 12.0 Mrd.   Multilayer film according to claim   13 characterized in that it has been irradiated with 6.0 million.