Packaging films containing coextruded polyester and nylon layers

Background of the invention

The present invention relates to flexible coextruded multilayer films used as packaging films or as a component thereof. In particular, the present invention relates to coextruded multilayer films, suitable for thermoforming, which have oxygen barrier properties.

Flexible multilayer films, suitable for thermoforming, are used for packaging food and medical items, thus protecting these items against external contamination and misuse, providing attractive packaging for the item for sale. The film structure, providing better mechanical strength, better optical and gas barrier properties, and especially improved thermoformability, is a great commercial gain for the packaging industry.

US 5,139,878 discloses the construction of a multilayer film comprising at least one fluoropolymer film, at least one thermoplastic polymer film, and at least one adhesive layer selected from the group consisting of alkyl ester copolymers and olefins, α, β-ethylenically unsaturated carboxylic acids, modified polyolefins and mixtures thereof.

US 6,037,063 describes a multilayer film comprising at least one barrier layer and at least one polyester layer that can be bonded together with an adhesive resin.

EP 0 638 487 A1 relates to a plastic multilayer container comprising an inner layer and an outer layer constituting a moisture resistant thermoplastic resin and a gas barrier resin layer sandwiched between these two layers.

Summary of the Invention

The present invention relates to a coextruded thermoformable multilayer film comprising at least a first layer of polyethylene terephthalate; a second layer of a first adhesive comprising a blend of at least an acrylate based resin and a modified polyolefin or a modified acrylate based resin, preferably a blend containing 25-99% (by weight based on the total weight of the second layer), more preferably 25-60% acrylate based resin ; wherein said blend contains 1-75% (by weight relative to the total weight of the second layer), preferably 10-75% of a modified polyolefin or modified acrylate based resin; wherein said blend also contains 0-30% (by weight relative to the total weight of the second layer) of unmodified polyolefin; a third layer, which includes an oxygen barrier thermoplastic polyamide, ethylene / vinyl alcohol copolymer, polyvinylidene chloride or a blend thereof, and more preferably a blend of polyamides.

Preferably, the thermoformable multilayer film is co-oriented.

The first surface of the second layer directly adheres to the first layer and the second surface of the second layer directly adheres to the third layer. The first layer of film is a layer with an expanded surface.

The acrylic-based resin from the first adhesive may preferably be selected from the group consisting of ethylene / vinyl acrylate copolymer (EVA), ethylene / methacrylate copolymer (EMA), ethylene / butyl acrylate copolymer (EBA) or mixtures thereof. The modified polyolefin in the first adhesive may preferably be an anhydride modified polyolefin, and the modified acrylic based resin of the first adhesive may be an anhydride modified acrylic based resin. More preferably, the anhydride-modified polyolefin may comprise a polyolefin selected from the group consisting of polyethylene, ethylene / α-olefin copolymer or mixtures thereof, and the anhydride-modified acrylate resin can be selected from the group consisting of anhydride-modified ethylene / vinyl acrylate (EVA) copolymer, anhydride modified ethylene / methacrylate (EMA) copolymer, anhydride modified ethylene / butyl acrylate (EBA) copolymer or mixtures thereof. Preferably, the unmodified polyolefin may comprise a material selected from the group consisting of polyethylene, ethylene / α-olefin copolymer, polypropylene, polybutylene or mixtures thereof.

The third layer may contain any suitable oxygen barrier thermoplastic e.g. polyamide, ethylene / vinyl alcohol copolymer, poly (vinylidene chloride) or mixtures thereof. Preferably, the oxygen barrier thermoplastic comprises a mixture of polyamides, more preferably a mixture comprising 71-99% by weight of crystalline polyamide and 1-29% by weight of amorphous polyamide, and most preferably 85% by weight of crystalline polyamide and 15% by weight of amorphous polyamide.

According to the present invention, a three-layer coextruded multilayer film suitable for thermoforming can be used individually, i.e. as a film for food packaging and / or non-food items. For some applications, it may be advantageous to include a three-layer film as a substructure of a larger flexible multi-layer film in the package. In such an arrangement, a larger multilayer film incorporating a three-layer structure as a substructure may advantageously have the properties and advantages of a three-layer film structure as discussed herein, but may also have additional features and advantages resulting from additional layers.

Large multi-layer film structures that incorporate a three-layer film structure as a substructure may have at least one additional layer adhered to this substructure by various methods known to the skilled person, which include thermal lamination, adhesive lamination, co-coating, lamination by coextrusion.

In another embodiment of the present invention, the coextruded film suitable for thermoforming may also include a fourth and a fifth layer. In one embodiment of this embodiment, the fourth layer may comprise a second adhesive, which is free of acrylate-based resin, and the fifth layer may comprise a sealant, preferably selected from the group consisting of polyethylene, ethylene / α-olefin, propylene / α-olefin, butylene / α-olefin, ionomer, acrylate resin or mixtures thereof. In another example of a five-layer embodiment, each second layer and fourth layer may comprise a first adhesive comprising an acrylate-based resin and a modified polyolefin or a modified acrylate-based resin, wherein the acrylate-based resin is selected from the group consisting of ethylene / vinyl acrylate copolymer ( EVA), ethylene / methacrylate copolymer (EMA), ethylene / butyl acrylate (EBA) copolymer or mixtures thereof, and the fifth layer may contain polyester, preferably selected from the group consisting of poly (ethylene terephthalate) poly (butylene terephthalate), poly (naphthalene terephthalate) and copolymers or mixtures thereof.

Preferably, the five-layer embodiment of the present invention is non-oriented.

In yet another embodiment, the five-layer coextruded film, suitable for thermoforming, may be a packaging film or a component thereof for stored food and / or non-food items.

In yet another embodiment of the present invention, the film may also include a sixth layer and a seventh layer, but is not limited to seven layers. In the first example of a seven-layer embodiment, each second and sixth layer may comprise a second adhesive, which is free of acrylate-based resin, and the seventh layer may contain a sealant, preferably selected from the group consisting of polyethylene, ethylene / α-olefin, propylene -olefin, butylene / α-olefin, ionomer, acrylate resin or mixtures thereof.

In a second example of a seven-layer embodiment of the present invention, the second layer may comprise a first adhesive comprising an acrylate-based resin and a modified polyolefin or a modified acrylate-based resin, wherein the acrylate-based resin is selected from the group consisting of ethylene / vinyl acrylate (EVA) copolymer , ethylene / methacrylate copolymer (EMA), ethylene / butyl acrylate copolymer (EBA) or mixtures thereof, the sixth layer may contain a second adhesive, which is free of acrylate-based resin, and the seventh layer may contain a sealant, preferably selected from the group consisting of polyethylene, ethylene / α-olefin, propylene / α-olefin, butylene / α-olefin, ionomer, acrylate resin or mixtures thereof .

In the third example of a seven-layer embodiment, each second and sixth layer may comprise a first adhesive comprising an acrylate based resin and a modified polyolefin or modified acrylate based resin, wherein the acrylate based resin is selected from the group consisting of ethylene / vinyl acrylate (EVA) copolymer , ethylene / methacrylate copolymer (EMA), ethylene / butyl acrylate copolymer (EBA) or mixtures thereof, and the seventh layer may contain polyester, preferably selected from the group consisting of poly (ethylene terephthalate), poly (butylene terephthalate), poly (naphthalene terephthalate) and their copolymers or mixtures.

In the fourth example of the seven-layer embodiment, all layers may be identical to the layers of the second example of this embodiment except the fourth layer, which may include a second acrylic-free resin adhesive.

In yet another embodiment of the present invention, the seven-layer coextrudable thermoformable film may be a packaging film or a component thereof for stored food and / or non-food items.

The seven-layer embodiment of the present invention is preferably not oriented.

Preferably, the films of the present invention may have a total thickness equal to or less than 0.4064 mm (16 mils).

Preferably, the films of the present invention may have a total thickness equal to or less than 0.254 mm (10 mils). Preferably, the films of the present invention may have ca^LKowit^{ą g}ru^babout^SC about^{d 0.0762 d}about ^0,1778 mm (3^-7 mils).

Preferably, the films of the present invention may have a free linear thermal shrinkage in the longitudinal or transverse direction of less than 5% at 90 ° C ^dLand ^pomcaru from methods^and tes^tthat^and AND^STM D-2:⁷³².

The films of the present invention may preferably have free linear thermal shrinkage in the longitudinal direction or transverse direction less than 2% at 90 ° C for measurement according to ASTM test method D-2732.

Preferably, the films of the present invention may contain less than 500 ppm transition metal salts selected from the group consisting of manganese II, manganese III, iron II, iron III, cobalt II, cobalt III, nickel II, nickel III, copper I, copper II, rhodium II, family III, family IV and ruthenium.

Preferably, the films of the present invention may have a gloss value greater than 65 Hunter Units (HU) ^dLand the measure from^gref^andwith the toast method^and ASTM D-²²44-⁸⁵.

Preferably, the films of the present invention may have an oxygen permeation rate of less than 15.5 cm³/ m²(1.0 cm3 / 100 inch2) for measurement according to ASTM test method D-3985-81.

The films of the present invention may preferably exhibit elongation at break in longitudinal direction and transverse direction greater than 250% at room temperature for measurement according to ASTM test method D-882-95.

Short description of the drawings

Fig. 1 is a cross-sectional view of a three-layer structure with three layers according to the present invention.

Fig. 2 is a cross-sectional view of a multi-layer structure with five layers in accordance with the present invention.

Fig. 3 is a cross-sectional view of a multi-layer structure with seven layers according to the present invention.

Detailed description of the invention

As used herein, the term "multilayer" refers to a plurality of layers in a single film structure generally in the form of a sheet or roll, which can be made of a polymeric or non-polymeric material bonded together by conventional means known in the art, i.e. by coextrusion, extrusion coating , lamination, vacuum coating, solvent coating, emulsion coating or suspension coating, or a combination of one or more of these methods. The multilayer film of the present invention may comprise as many layers as needed, preferably at least three layers.

As used herein, the term "thermoformable" refers to films that are capable of forming into the desired shape by applying heat and are thermally shaped on the product on the support element using heat and differential pressure. In the thermoforming process, all air is removed from the inside of the packaging, so that the foil corresponds very closely to the contour of the packaged product. Heat is generally used to cause the film to bond to the support member outside the product circumference or by forming the film and support member from materials that are otherwise compatible with the application of heat, e.g. by using similar, heat-sealable polymeric materials, on the interface during welding, which bind to each other when heated, or by using heat activated glue on the interface of the film and the carrier.

As used herein, the term "thermoplastic material" refers to a polymer or mixture of polymers that soften when exposed to heat and returns to its original state when cooled to room temperature. Typically, thermoplastic materials include, but are not limited to, synthetic polymers such as like polyamides, polyolefins, alkyl polyacrylates, polyesters, ethylene / vinyl alcohol copolymers etc. Thermoplastic materials may also include any synthetic polymer that has been crosslinked by radiation or by a chemical reaction during the manufacturing process operations.

As used herein, the term "polymer" refers to a polymerization reaction product and includes homopolymers, copolymers, terpolymers, etc. Typically, film layers may consist essentially of a single polymer, or may also include additional polymers with it, i.e. mixed with it. .

The expression "copolymer" refers to polymers formed by the polymerization reaction of at least two different monomones. For example, the expression "copolymer" includes the product of a copolymerization reaction of ethylene and α-olefin, such as 1-hexene. The expression "copolymer" also includes, e.g., copolymerization of a mixture of ethylene, propylene, 1-propene, 1-butene, 1-hexene and 1 octene. As used herein, a copolymer defined in terms of most monomers, e.g. "Propylene / ethylene copolymer" refers to a copolymer in which one monomer can copolymerize in a greater weight or molar percentage than other monomer or monomers.

However, the first mentioned monomer preferably polymerizes in a greater weight or molar percentage than the second mentioned monomer.

The terminology using "/" for identifying the copolymer (e.g., a chemical poly (vinylidene chloride) / methyl acrylate copolymer)) defines comonomers that are copolymerized to make a copolymer.

The term "polyester" as used refers to homopolymers or copolymers having an ester bond between monomer moieties that can form, e.g., between dicarboxylic acid and glycol by condensation polymerization. The dicarboxylic acids may be linear aliphatic, i.e. include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like; or they may be aromatic or aromatic substituted with alkyl, i.e. include various isomers of phthalic acid, such as paraphthalic acid (i.e. terephthalic acid), isophthalic acid and naphthalic acid. Specific examples of alkyl substituted aromatic acids are various isomers of dimethylphthalic acid, such as dimethylisophthalic acid, dimethylorthophthalic acid, dimethyl terephthalic acid, various isomers of diethylphthalic acid, such as diethylisophthalic acid, dimethylorthophthalic acid, various isomers of dimethylnaphthalic acid, and 2,5-dimethaphthalene dimethylnaphthalic and various isomers of diethylnaphthalic acid. Glycols can be linear or branched. Specific examples include ethylene glycol, propylene glycol, trimethylene glycol, 1,4-butanediol, neopentyl glycol, etc. In one example of a preferred embodiment of this invention, the first layer comprises a poly (ethylene terephthalate) copolymer and biaxially oriented poly (ethylene terephthalate) copolymer

The term "biaxially oriented" as used herein refers to a coil or sheet of polymer forming a film structure whose coil is elongated in two directions at elevated temperature, then "cured" in an elongated configuration by cooling the material, whereby the extended dimensions generally remain. The combination of elongation at elevated temperature and subsequent cooling results in the ordering of polymer chains to obtain a more parallel configuration, thereby improving the mechanical properties of the polymer web. By subsequently heating a given free, unheated, biaxially oriented polymer sheet to its orientation temperature, thermal shrinkage can be produced.

After orientation, the biaxially oriented polymer web is preferably cooled and then heated to an elevated temperature, more preferably to an elevated temperature, which is higher than the glass transition temperature and lower than the melting point of the polymer crystals.

This reheating step, which can be considered to be annealing or heat curing, is performed to obtain a polymer coil with a uniform plane width. In accordance with the present invention, a biaxially oriented polymer web that can be used to form the film layer is heated to an elevated temperature to give the packaging film having free linear thermal shrinkage in the longitudinal direction and transverse direction less than 5%, preferably less than 2%, at a temperature of 85 ° C, for measurement according to ASTM D-2732-96 test method, which is incorporated herein by reference. This biaxially oriented polymer web can be annealed or heated to an elevated temperature either simultaneously (and then) or outside (in a separate process) of the orientation process. However, the annealing process which is carried out simultaneously with the orientation process is preferred.

The expression "glue" refers to a polymer material that serves the primary purpose of the function of attaching two surfaces to each other. In the present invention, the adhesive may attach one surface of the film layer to another surface of the film layer or one area of ​​the surface of the film layer to another area of ​​the same surface film layers. The adhesive may contain any polymer, copolymer or mixture of polymers having a polar group or any other polymer, homopolymer, copolymer or mixture of polymers, including modified and unmodified polymers e.g. graft copolymers that provide sufficient adhesion of the interlayer to adjacent layers containing otherwise non-adhesive polymers. The adhesive compositions of the present invention may include, but are not limited to, modified and unmodified polyolefins, preferably polyethylene, most preferably ethylene / α-olefin copolymer, modified and unmodified acrylate resin, preferably selected from the group consisting of ethylene / vinyl acrylate copolymer, ethylene / copolymer ethyl acrylate, ethylene / butyl acrylate copolymer or mixtures thereof.

The expression "oxygen barrier thermoplastic" refers to a polymeric material that controls the oxygen permeability of the entire film. For perishable food packaging applications, the oxygen permeation rate (OTR) should preferably be minimized. The expression "oxygen permeation rate" is defined herein as the amount oxygen in cubic centimeters (cm³), which passes through 0, 064516 m² (100 inches²) for 24 hours at 0% relative humidity at 23 ° C (or cm3 / 100 inches2 for 24 hours at 0% relative humidity and at 23 ° C). The thickness (nominal thickness) of the film is directly related to the rate of oxygen permeation. Packaging films, useful as an oxygen barrier, are required to have an OTR value of 0 to¹⁵⁵ cm^3/m² (^0-10,0 cm^3/100 inches²) on ^{24 g}about^dZTO^ypgovernment^{y 0}% relative humidity and at 23 ° C, for 0.025 mm (1.0 mils) or less. Oxygen penetration can be measured according to the ASTM D-3985-81 method, which is incorporated herein by reference.

The oxygen barrier thermoplastic of the present invention may include, but is not limited to, polyamides, ethylene / alcohol alcohol copolymers, polyvinylidene chlorides or mixtures thereof. Preferably, the oxygen barrier thermoplastic of the present invention may comprise a mixture of polyamides. More preferably, the oxygen barrier thermoplastic comprises a mixture containing about 71-99% by weight of a crystalline polyamide selected from the group consisting of nylon 4.6 (polytetramethylene adipinoamide), nylon 6 (polycaprolactam), nylon 6.6 (polyhexamethylene adipinoamide), nylon 6.9 (polyhexamethyleneonanediamide) ), nylon 6.10 (polyhexamethylene sebacinamide), nylon 6.12 (polyhexamethylenedodecanediamide), nylon 6/12 copolymer (polycaprolactam / dodecanediamide), nylon 6.6 / 6 copolymer ((polyhexamethylene adipinoamide / caprolactam), nylon 11 (polyunecanolactam), nylon 12 (polyylauryl lactam) or mixtures thereof and about 1-29% by weight of amorphous polyamide.

Most preferably, the oxygen barrier thermoplastic may comprise a mixture of polyamides of about 85% by weight of a polyamide selected from the group consisting of nylon 4.6 (polytetramethylene adipinoamide), nylon 6 (polycaprolactam), nylon 6.6 (polyhexamethylene adipinoamide), nylon 6.9 (polyhexamethyleneonanediamide), nylon 6.10 (polyhexamethylene sebacinamide), nylon 6.12 (polyhexamethylenedodecanediamide), nylon 6/12 copolymer (polycaprolactam / dodecanediamide), nylon 6.6 / 6 copolymer ((polyhexamethylene adipinoamide / caprolactam), nylon 11 (polyiuecolactam), nylon 12 (polyauryl lactam) or mixtures thereof and 15% by weight amorphous polyamide.

As used herein, the term "polyamide" refers to homopolymers, copolymers or terpolymers that contain an amide bond between monomer moieties that can be formed by methods known to those skilled in the art. Useful polyamide homopolymers include nylon 6 (polycaprolactam), nylon 11 (polyundecanolactam), nylon 12 (polylauryl lactam) etc. Other useful polyamide homopolymers include nylon

4.2 (poly-tetramethylene ethylenediamide), nylon 4.6 (polytetramethylene adipinoamide), nylon 6.6 (polyhexamethylene adipinoamide), nylon 6.9 (polyhexamethylene azelaic diamide), nylon 6.10 (polyhexamethylene sebacinamide), (polyhexamethylenedodecanedimethylene), methylenediamine), nylon 6.12 (polyhepta (polyocta (polinonanylone 7.7

9, 9 methylene azelaide), nylon 10.9 (polydecamethylene azelaide), 12.12 nylon (polydecamethylene dodecanediamide), etc. Useful polyamide copolymers include nylon 6.6 / 6 copolymer (polyhexamethylene adipinoamide / caprolactam copolymer), nylon 6 / 6.6 copolymer (polycaprolactam / hexamethylene adipinoamide copolymer), nylon 6.2 / 6.2 copolymer (polyhexamethyleneethyleneenediamide copolymer), hexamethylene diamide 6.6 / 6.9 / 6 (polyhexamethylene adipinoamide / hexamethyleneazelainamide / caprolactam copolymer), as well as other nylons which are not specifically listed here. Examples of even more suitable polyamides include nylon 8, I, nylon 6, I, nylon 6,6 / 6I copolymer, nylon 6,6 / 6T copolymer, MXD6 (poly-m-xylylene adipinoamide), nylon 6T / 6I copolymer, ^knylon opolymer ^{6 / MXDT /}And, nylon ^MXDI ^pabout^li-pxylylene adipinoamide, polyhexamethylene terephthalamide, polydodecamethylene terephthalamide, etc.

The expression "amorphous polyamide" refers to polyamides or nylons without a regular three-dimensional arrangement of molecules or subunits of molecules covering distances that are large in relation to atomic sizes. However, structure regularity exists on a local scale. See, "Amorphous Polymers" in Encyclopedia of Polymer Science and engineering 2nd, pp. 789-842 (J.Wiley & Sons, Inc. 1985). This document has a catalog card number in the Congress Bible Bible nu 84-17113. In particular, the expression "amorphous polyamide" as used in connection with the present invention refers to a material recognized by a person skilled in the art on the basis of differential scanning calorimetry (DSC) as having an immeasurable melting point (below 0.5 inch / g) or a lack of heat of fusion for measurement DSC, using the ASTM 3417-83 method. Such nylons include amorphous nylons formed by condensation polymerization reactions of diamines with dicarboxylic acids. For example, an aliphatic diamine combines with an aromatic dicarboxylic acid or an aromatic diamine with an aliphatic dicarboxylic acid to form the corresponding amorphous nylons.

The expression "ethylene / vinyl copolymer" or "EVOH" refers to polymerized ethylene and vinyl alcohol. The ethylene / vinyl alcohol copolymer includes saponified or hydrolyzed ethylene / vinyl acrylate copolymers and refers to a vinyl alcohol copolymer containing ethylene as a comonomer, and prepared e.g. by hydrolysis of vinyl acrylate copolymers or by chemical reaction with vinyl alcohol. The degree of hydrolysis is preferably at least 50% and more preferably at least 85%. Preferably, the ethylene / vinyl alcohol copolymers contain 28-48 mole% ethylene, more preferably 32-44 mole% ethylene, and even more preferably 38-44 mole% ethylene.

The term "polyolefin" as used refers to homopolymers, copolymers, including, e.g., bipolymers, terpolymers, etc., containing a methylene bond between monomer moieties that can be prepared by any method known to a person skilled in the art. Suitable examples of polyolefins include polyethylene, low density polyethylene, linear low density polyethylene, very low density polyethylene, ultra low density polyethylene, medium density polyethylene, high density polyethylene, polyethylenes including copolymers of ethylene with one or more alpha-olefins (a- olefins), such as 1-butene, 1-hexene, 1-octene, or similar as a comonomer, copolymers of linear low density polyethylene, very low density polyethylene, ultra-low density polyethylene, ethylene / propylene copolymers, polypropylene, propylene / ethylene copolymer, polyisoprene, polybutylene, polybutene, poly-3-methylbuten-1, poly-4-methylpentene-1, ionomers, etc.

The expression "ethylene / α-olefin" as used refers to a modified or unmodified copolymer prepared by copolymerization of ethylene and one or more α-olefins. The α-olefin in the present invention may contain 3-20 hanging carbon atoms.

The copolymerization of ethylene and α-olefin can be carried out using heterogeneous catalysis, i.e. copolymerization reactions with a Ziegler-Natta catalyst system, e.g. metal halides activated by an organometallic catalyst, i.e. titanium chloride, optionally containing magnesium chloride, complexed with trialkylaluminum and can be found in patents like US No. 4^,3°^2,56^5, Goe^ke ⁱⁱn. ^and No. ^US 4^,302,566^{, K}Aroi. ⁱⁱn.

Copolymers of ethylene and heterogeneously catalyzed α-olefins may include linear low density polyethylene, very low density polyethylene and ultra low density polyethylene. Such copolymers of this type are available, e.g., from the Dow Chemical Company, Midland, MI, USA and sold under the trademark DOWLEX ™ resins.

In addition, the copolymerization of ethylene and α-olefin can also be carried out using homogeneous catalysis, e.g. copolymerization reactions with a metallocene catalyst system, which includes a forced geometry catalyst, i.e. transition metal and monocyclopentadiene complexes, given in US Pat. No. 5,026,798, Canich, information from which are included here as a reference. Homogeneously catalyzed ethylene and α-olefin copolymers may include modified and unmodified ethylene / α-olefin copolymers having a long branched chain (8-20 hanging carbon atoms) from α-olefin as comonomer, available from Dow Chemical Company, known as^kabout ^foovice versa AFFINITY ™ ^and ATTANE ™ ,. TAFMER ™ secondary copolymers, available from Mitsui Petrochemical Corporation, Tokyo, Japan, and modified or unmodified ethylene / α-olefin copolymers having a short branched chain (3-6 hanging carbon atoms) with α-olefin as comonomer, known as EXACT ™ resins, to be obtained from Exxon Mobil Chemical Company, Houston, TX, USA.

Generally, homogeneously catalyzed ethylene and α-olefin copolymers can usually be characterized by one or more methods known to the skilled person, such as molecular weight distribution (M_in/ M_n), composition distribution index (CDBI), narrow melting range and single melting point demonstration. Molecular weight distribution (M_in/ M_n) also known as "polydispersity" can be determined by gel permeation chromatography (GPC), where M_in is indicated by the weight average molecular weight and M_n is defined as the number average molecular weight. The molecular weight of polymers and copolymers can be determined by the ASTM D-3593-80 method, which is incorporated herein by reference in its entirety. The ethylene / α-olefin copolymers of the present invention may be homogeneously catalyzed ethylene and α-olefin copolymers which may exhibit Mw / M_n less than 2.7. The composition distribution ratio (CDBI) of ethylene-α-olefin copolymers homogeneously catalysed is generally greater than 70%. This contrasts with ethylene and α-olefin copolymers heterogeneously catalyzed, which have a composition distribution ratio generally less than 55%. CDBI is defined as the weight percentage of copolymer particles having a comonomer content within 50% (i.e. plus or minus 50%) of the average molar content of the total comonomer. The composition distribution index (CDBI) can be determined using the Rising Elution Fractionation (TREF) method described by Wild et al., Journal of Polymer Science, Po^ly.P^hyp.^Ed.^, volume ^20, s^tr.44¹(¹98²) ^and about^pis ^pand^ten^tthat^s U No.^S4, 798, 081, both of which are incorporated herein by reference in their entirety.

In general, homogeneously catalyzed ethylene / α-olefin copolymers may have the essential property of a single melting point, at the melting point (T_m) determined by differential scanning calorimetry (DSC). The term "essential property of a single melting point" means that at least about 80% by weight of the material corresponds to a single Tm peak. DSC measurement can be performed on a Perkin Elmer apparatus^System ⁷ Ifermal Ana^lys^ands ^Systamp according to^g methodology^dy AND^STM D^-3418,which is incorporated herein by reference in its entirety.

The term "modified" as used refers to crotonic, fumaric, copolymerized, etc., a chemical derivative, e.g. having an anhydride function, such as maleic anhydride, citraconic acid, itaconic acid, an acid that has been grafted into a polymer, polymer or mixed with one or many polymers and also includes derivatives with functions such as acids, esters and their metal salt derivatives.

The term "acrylate-based resin" as used refers to homopolymers, copolymers, including, e.g., bipolymers, terpolymers, etc., having an acrylate portion in at least one of the repeating moieties forming the main polymer chain. In general, an acrylate-based resin is also known as poly (alkyl acrylates) Acrylate resins or poly (alkyl acrylates) can be prepared by any method known to a person skilled in the art. Suitable examples of these resins for use in the present invention include ethylene / vinyl acrylate (EVA) copolymers, ethylene / methacrylate (EMA) copolymers, ethylene / butyl acrylate (EBA) copolymer, etc.

The expression "outer surface layer" as used refers to each layer of film in a multilayer film having less than two of the major surfaces immediately adjacent to another film layer. The term "sealant" refers to a layer that is heat-sealable, i.e., capable of being bonded after melting by conventional direct heating means that generate sufficient heat on at least one contact surface of the film to conduct to the adjacent contact surface of the film and creating a binding surface between them without losing the integrity of the film. Preferably, the binding surface must have sufficient heat resistance to prevent gas or liquid from escaping from it. Suitable examples of sealants for the present invention include, but are not limited to, polyolefins, including polyethylenes, polypropylenes, polybutylenes, ionomers, ethylene / α-olefin copolymers and the like.

The multilayer films of the present invention can be made by any suitable and known film making process, e.g., by casting or blowing through an annular or slot die, and are preferably fully coextruded. As used herein, the term "coextruded" refers to the process of extruding two or more materials through a single nozzle with two or more holes arranged so that the extrudate products combine and bond together into a laminated structure before cooling and hardening. The film of the present invention they can generally be made from dry resins that are melted in an extruder and pass through a die to form the primary film material, usually in the form of a tube. The well-known two-stage double bubble or trapped bubble process can be used to make the multilayer film of the present invention. One embodiment of the double bladder method is described in US Patent No. 3,456,044 to Pahlke, which is incorporated herein as a reference. In the Pahlke-type double bladder method, the original tube is extruded, cooled, reheated and the tube is simultaneously stretched in the longitudinal direction by longitudinally arranged rollers operating at different speeds, and in the transverse direction by the blown air inside the tube. Suitable stretching ratios are 2-6, with a preferred ratio of 35. In the multilayer films of the present invention, all layers were simultaneously coextruded, cooled with water, cooled with a metal roller or with air-cooling, after which they could again be heated for biaxial orientation.

Unless otherwise stated, the thermoplastic resins used in the present invention are generally commercially available in the form of granules and as generally known in the art, can be mixed after melting or mechanically mixed by well known methods using commercially available devices including drums, mixers or automatic dosing mixers. Also, if desired, well-known additives such as process aids, glidants, anti-blocking agents, pigments and mixtures thereof can be incorporated into the film by mixing prior to extrusion. Resins and additives are introduced into an extruder, where the resins are plasticized after melting by heating and then sent to an extrusion (or co-extrusion) die to form into a tube. Extruder and nozzle temperatures generally depend on the particular resin or resin mixture involved, and suitable temperature ranges for commercially available resins are generally known in the art or are provided in technical bulletins provided by resin factories. Process temperatures may vary depending on other selected process parameters.

In the practice of this invention, it may be desirable to irradiate the entire film to crosslink at least one layer of the film to improve resistance to misuse and / or puncture and other physical properties of the film. Cross-linking is the dominant reaction that occurs when many polymers are irradiated and is the result of the formation of carbon-carbon bonds between polymer chains. Crosslinking can be done e.g. by irradiation with high energy electrons, gamma rays, beta particles, etc. The source of radiation can be any electron beam generator operating in the 150-6000 kilovolts (6 megawolts) range with an output power capable of delivering the desired dose. The voltage can be set to an appropriate level, which can be e.g. 1-6 million volts or more or less. Experts know many apparatus for irradiating films. The most favorable amount of radiation depends on the film and its final use.

The present invention will now be further described in more detail with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be presented in various forms and should not be construed as limited to the forms represented herein; rather, these forms are given so that this disclosure is accurate and complete and fully expresses the scope of the invention to the skilled person. Similar numbers refer to similar elements in their entirety.

Referring now to Fig. 1, film 10 illustrates one example of a three-layer embodiment of the present invention. The film 10 is shown to have a first layer 11, a second layer 12 sandwiched between the first layer 11 and the third layer 13. The first layer 11, the second layer 12 and the third layer 13 all contain the materials mentioned above.

Referring now to Figure 2, film 20 illustrates one example of a five-layer embodiment of the present invention. The film 20 is shown having a first layer 21, a second layer 22 sandwiched between the first layer 21 and the third layer 23, the fourth layer 24 and the fifth layer 25. The first layer 11, the second layer 12, the third layer 13, the fourth layer 24 and the fifth layer 25 , all contain the materials listed above.

Referring now to Figure 3, film 30 illustrates one example of a seven-layer embodiment of the present invention. The film 30 is shown having a first layer 31, a second layer 32 sandwiched between the first layer 31 and the third layer 33, the fourth layer 34, the fifth layer 35, the sixth layer 36 and the seventh layer 37. First layer 11, second layer 12, third layer 13, fourth layer 24, fifth layer 25, sixth layer 36 and seventh layer all contain the materials mentioned above.

Examples Example 1-2

It should be understood that the scope of the present invention is not limited to the following examples.

Tables 1-2 below illustrate the coextruded three-layer film of the present invention. Tables 1-2 provide details of the identity of the different materials present in each film layer, the positioning of each film layer, and the thickness of each film layer.

this^blica 1

<td rowspan="2">Foil layer</td><td colspan="2">Example 1</td>

<td>Material</td><td>Thickness</td>

<td>First</td><td>Poly (ethylene terephthalate) (PET-1)</td><td> 20%</td>

<td>Second</td><td>Ethylene / methacrylate mixture + modified polyethylene + unmodified polyethylene (Adhesive-1)</td><td> 55%</td>

<td>third</td><td>Polyamide blend (Barrier agent-1)</td><td> 25%</td>

Table 2

<td rowspan="2">Foil layer</td><td colspan="2">Example 2</td>

<td>Material</td><td>Thickness</td>

<td>First</td><td>^Pabout^l (tereftakn ethknu) (ΕΈΤ^-1)</td><td> 20%</td>

<td>Second</td><td>Ethylene / methacrylate mixture + modified polyethylene + unmodified polyethylene (Kl^ej-2)</td><td> 55%</td>

<td>third</td><td>Ethylene / vinyl alcohol copolymer (Barrier agent-2)</td><td> 25%</td>

In the above Tables 1-2, Examples 1-2 may have a first layer comprising a poly (ethylene terephthalate) (PET-1) copolymer and poly (ethylene terephthalate) additives that are dried prior to mixing. Poly (ethylene terephthalate) is a copolymer having a specified density of about 1.27 g / cm³, intrinsic viscosity about 0.70, gloss 45 ° 108 units

Hunter (HU) and is available under the trade name EASTAR ™ Copolyester 6763 from Eastman Chemical Company, Kingsport,

Tennessee, USA.

For examples 1-2, the second layer may be an adhesive (Glue1) containing a 60% mix (by weight relative to the total weight of the second layer) of ethylene / methacrylate copolymer (EMA), having a 22% methyl acrylate content, density of about 0.948 g / cm3, index flow rate 2.0 g / 10 minutes and available under the product name SP 1330 z

Eastman Chemical Company, Kingsport, TN, USA, 10% (by weight relative to the total weight of the second layer) low density linear anhydride modified polyethylene, density 0.92 g / cm3, melting point 125 ° C, melt flow index 1 , 5 g / 10 minutes, sold under the name ^han^dLthat^and BY^NEL ® ^41E712, available^goz ^E.AND. ^de ^pont ^de

Nemours and Company, Wilmington, DE, USA and 30% (by weight relative to the total weight of the second layer) of ultra-low density polyethylene, having a density of 0.912 g / cm3, a flow rate of 1.0 g / 10 minutes and a melting point of 123 ° C , sold under the product name ATTANE® 4201G and available from Dow Chemical Company, Midland, MI, USA.

In Example I, the third layer contains an oxygen barrier agent from a polyamide mixture (Barrier Agent-1) in an amount of 85% (by weight relative to the total weight of the third layer) of nylon 6 with a density of 1.12 g / cm3, melting point 220 ° C, recrystallization temperature 176 ° C (when measured by differential scanning calorimetry (DSC)) ^, dos^tepAD^gabout ^pfrom han^dLthat^and names^and ULTRAMID ™ B36 from BASF

Corporation, Mount Olive, New Jersey, USA; and 15% (by weight relative to the total weight of the third layer) amorphous nylon with a density of 1.19 g / cm3³, glass transition temperature 127 ° C, heat deflection temperature 126 ° C at 455 kPa (66 psi) sold under the name ^han^dLthat^{ą S}E^LAR™ ^{PA 3426 p}slaughter ^E.this ^Phe^tde ^Nemours and. Company, Wilmington, Delaware, USA.

In Example 2, the third layer may comprise an oxygen barrier agent from an ethylene / vinyl alcohol copolymer (barrier agent 2), preferably an ethylene / vinyl alcohol copolymer having a bulk density of 0.64-0.74 g / cm3, relative density 1, 13-1.22 g / cm3, melting point 164¹⁸⁸° it's me^k sold^ypabout^d names^{ą h}an^dLthat^{ą SOARNOL}™ ^{ET3803 and}available from Nippon Synthetic Chemical Industry Company, Ltd (Nippon Gohsei), Osaka, Japan.

In Examples 1-2 of the present invention, multilayer structures suitable for thermoforming are formed into foil in the following procedure: Each layer is plasticized after melting in a separate extruder connected to an annular coextrusion die which coextruds the plasticized layers under the influence of heat, forming tube or bladder. The bladder has a first layer, a second layer and a third layer. The first layer and the third layer are directly related to opposite sides of the second core layer.

For each layer, the resin or resin mixture is supplied from the feed hopper to the associated single screw extruder, where the resin or resin mixture is plasticized under the influence of heat and extruded through a three-layer coextrusion die as a tube or a single bladder. The extruder body temperature for the first layer is 260 ° C (500 ° F) and for the second and third layers is 271 ° C (520 ° F). The bladder width is kept below 1.346 m (53 inches). The extruded multilayer bladder cools quickly against a cooled solid surface. The cooled bladder is flattened with a pair of rollers and the films obtained from examples 1-2 have an average nominal thickness of 0.127 mm (5 mils).

Examples 3-4

Tables 3-4 below illustrate the coextruded five-layer film of the present invention. Tables 3-4 give details of the identity of the different materials present in each layer of foil1, the setting of each layer of foil and the thickness of each layer of foil.

Table 3

<td rowspan="2">Foil layer</td><td colspan="2">Example 3</td>

<td>Material</td><td>Thickness</td>

<td>First</td><td>^Pabout^l (^tere^ftand^lan e^backenu) (PE^T1)</td><td> 25%</td>

<td>Second</td><td>Polyethylene / methacrylate mixture + modified polyethylene + unmodified polyethylene (Adhesive-1)</td><td> 17%</td>

<td>third</td><td>Polyamide blend (Barrier agent-1)</td><td> 15%</td>

<td>Fourth</td><td>Modified polyethylene (Glue-2)</td><td> 18%</td>

<td>^Piand^tand</td><td>ionomer</td><td> 25%</td>

<td colspan="3">^Tand^blica ⁴</td>

<td>Foil layer</td><td>Example 4 Material</td><td>Thickness</td>

<td>First</td><td>^Pabout^l (tereftahn etyhnu) (RET^-1)</td><td> 25%</td>

<td>Second</td><td>Mixture: ethylene / methacrylate + modified polyethylene + unmodified polyethylene (Adhesive-1)</td><td> 17%</td>

<td>third</td><td>Ethylene / vinyl alcohol (Barrier agent-2)</td><td> 15%</td>

<td>Fourth</td><td>Mixture: ethylene / methacrylate + modified polyethylene + unmodified polyethylene (Glue-1)</td><td> 18%</td>

<td>^Piand^tand</td><td>^Pabout^l (tereftahn etyhnu) (ΕΈΤ^-1)</td><td> 25%</td>

In the above tables 3-4 the first layer from the examples

3-4 contains poly (ethylene terephthalate) copolymer (PET-1) and poly (ethylene terephthalate) additives that are dried before mixing. The poly (ethylene terephthalate) copolymer has a density of about 1.27 g / cm³, intrinsic viscosity about 0.70, gloss 45 ° 108 Hunter units (HU) and is available under the trade name EASTAR ™ Copolyester 6763 from Eastman Chemical Company, Kingsport, Tennessee, USA.

The second layer in Examples 3-4 may contain an adhesive (Glue-1) comprising a 60% mix (by weight relative to the total weight of the second layer) ^ ethylene / methacrylate (EMA) having a methyl acrylate content of 22%, density about 0.948 g / cm3, melt flow rate 2.0 g / 10 minutes and available under the product name SP 1330 from Eastman Chemical Company, Kingsport, TN, USA, 10% (by weight based on the total weight of the second layer) of low-polyethylene linear density anhydride modified 0.92 g / cm3 melting point 125 ° C, melt flow rate 1.5 g / 10 minutes, sold under the trade name BYNEL® 41E712, available from EI de Pont de Nemours and Company, Wilmington, DE, USA and 30% (by weight relative to the total weight of the second layer) of polyethylene, having a density of 0.918 g / cm3, a flow rate of 1.0 g / 10 minutes and a melting point of 120 ° C , sold under the product name LL 1001 and available from Exxon Mobil Chemical Company of Houston, TX, USA.

In Example 3, the third layer contains an oxygen barrier agent from a polyamide mixture (barrier agent-1) in an amount of 85% (by weight relative to the total weight of the third layer) of nylon 6 with a density of 1.12 g / cm3, melting point 220 ° C, recrystallization temperature 176 ° C (when measured by differential scanning calorimetry (DSC)) ^, dos^tepAD^gabout ^pfrom han^dLthat^and names^and ULTRAMID ™ B³6 from BASF

Corporation, Mount 01ive, New Jersey, USA; and 15% (by weight relative to the total weight of the third layer) amorphous nylon with a density of 1.19 g / cm3³, glass transition temperature 127 ° C, heat deflection temperature 126 ° C at 455 kPa (66 psi) sold under the trade name SELAR® PA 3426 by EI de Pont de Nemours and Company, Wilmington, Delaware, USA.

In Example 4, the third layer contains an oxygen barrier agent from an ethylene / vinyl alcohol copolymer (Barrier Agent-2), preferably an ethylene / vinyl alcohol copolymer having a bulk density of 0.64-0.74 g / cm3, relative density 1.13- 1.22 g / cm3, melting point 1641.88^k s^psculpture^dawan^ypabout^d names^{ą h}andlow^{ą S}CA^RN0^L™ ^{ET3803 and}available from Nippon Synthetic Chemical Industry Company, Ltd (Nippon Gohsei), Osaka, Japan.

In Example 3, the fourth layer may be an adhesive (Glue-2), which contains anhydride-modified polyethylene, density 0.941 g / cm3, flow rate 5.0 g / 10 minutes, softening point according to Vicat 48 ° C and ^dost^ęavailable ^pabout^d names^{ą h}andlow^and YOU^M0R™ ^72X06 from ^Rabout^hm and. Haas Company, Philadelphia, Pennsylvania, USA.

In example 4, the fourth layer may be the same as the second layer of this example described above.

In Example 3, the fifth layer includes an ionomer containing a partial zinc salt of ethylene / methacrylic acid copolymers with a density of 0.940 g / cm3, a melt flow rate of 1.30 g / 10 minutes at 190 ° C, a softening point of Vicat 73.9 ° C (165 ° F) and sold under the trade name SURLYN ™ ¹⁶⁰¹ from EI Mon^tde Nemours and.

Company, Wilmington, Delaware, USA.

In Example 4, the fifth layer may contain polyethylene terephthalate (PET-1) the same as in the first layer of this example as described above.

The films of example 3-4 have an average nominal thickness of ^{0.1016 d}about ^0,127 mm (^4-5 m^ilica^l).

^{10 P}government^YKLad^{y 5-}8

Tables 5-8 below illustrate the coextruded seven-layer film of the present invention. Tables 5-8 give details of the identity of the different materials present in each film layer, the setting of each film layer, and the thickness of each film layer.

Table 5

<td>Foil layer</td><td>Example 5 Material</td><td>Thickness</td>

<td>First</td><td>Poly (ethylene terephthalate) (PET-1)</td><td> 20%</td>

<td>Second</td><td>Modified polyethylene (Kl^ej-2)</td><td> 13%</td>

<td>third</td><td>Polyamide blend (Barrier agent-1)</td><td> 14%</td>

<td>Fourth</td><td>Ethylene / vinyl alcohol (Barrier agent-2)</td><td> 9%</td>

<td>^Piand^tand</td><td>Polyamide blend (Barrier agent-1)</td><td> 14%</td>

<td>sixth Seven</td><td>Modified polyethylene (Kl^ej-2) ionomer</td><td> 12% 18%</td>

<td colspan="3">^Tand^blica 6</td>

<td></td><td>Example 6</td><td></td>

<td>Foil layer</td><td>Material</td><td>Thickness</td>

<td>First</td><td>Poly (ethylene terephthalate)</td><td> 20%</td>

<td></td><td>(PET-2)</td><td></td>

<td>Second</td><td>Modified polyethylene</td><td> 13%</td>

<td></td><td>(Kl^ej-2)</td><td></td>

<td>third</td><td>Polyamide blend</td><td> 14%</td>

<td></td><td>(Barrier agent-1)</td><td></td>

<td>Fourth</td><td>Ethylene / vinyl alcohol</td><td> 9%</td>

<td></td><td>(Barrier agent-2)</td><td></td>

<td>^Piand^tand</td><td>Polyamide blend</td><td> 14%</td>

<td></td><td>(Barrier agent-1)</td><td></td>

<td>sixth</td><td>Modified polyethylene</td><td> 12%</td>

<td></td><td>(Kl^ej-2)</td><td></td>

<td>Seven</td><td>ionomer</td><td> 18%</td>

Table 7

<td>Aeolian layer</td><td>Example 7 Material</td><td>Thickness</td>

<td>First</td><td>Poly (ethylene terephthalate)</td><td> 20%</td>

<td></td><td>(PET-2)</td><td></td>

<td>Second</td><td>Mixture: ethylene / methacrylate</td><td> 13%</td>

<td></td><td>+ fashioned polyethylene</td><td></td>

<td></td><td>+ unmodified polyethylene</td><td></td>

<td></td><td>(Adhesive-1)</td><td></td>

<td>third</td><td>Polyamide blend</td><td> 14%</td>

<td></td><td>(Barrier agent-1)</td><td></td>

<td>Fourth</td><td>Ethylene / vinyl alcohol</td><td> 9%</td>

<td></td><td>(Barrier agent-2)</td><td></td>

<td>^piand^tand</td><td>Polyamide blend</td><td> 14%</td>

<td></td><td>(Barrier agent-1)</td><td></td>

<td>sixth</td><td>Modified polyethylene</td><td> 12%</td>

<td></td><td>(Kl^ej-2)</td><td></td>

<td>Seven</td><td>ionomer</td><td> 18%</td>

<td colspan="3">Tabrtca 8</td>

<td></td><td>Example 8</td><td></td>

<td>Aeolian layer</td><td>Material</td><td>Thickness</td>

First Poly (ethylene terephthalate) 20% (PET-2)

Second Mix: 13% ethylene / methacrylate + modified polyethylene + unmodified polyethylene (Glue-1)

<td>third</td><td>Polyamide blend (Barrier agent-1)</td><td> 14%</td>

<td>Fourth</td><td>Ethylene / vinyl alcohol (Barrier agent-2)</td><td> 9%</td>

<td>^pithat rectangle</td><td>Polyamide blend (Barrier agent-1)</td><td> 14%</td>

<td>sixth</td><td>Mixture: ethylene / methacrylate + modified polyethylene + unmodified polyethylene (Adhesive-1)</td><td> 13%</td>

<td>Seven</td><td>Poly (ethylene terephthalate) (PET-2)</td><td> 17%</td>

Table 9

<td rowspan="2">Foil layer</td><td colspan="2">Example 9</td>

<td>Material</td><td>Thickness</td>

<td>First</td><td>Poly (ethylene terephthalate) (PET-2)</td><td> 20%</td>

<td>Second</td><td>Mixture: ethylene / methacrylate + modified polyethylene + unmodified polyethylene (Adhesive-1)</td><td> 13%</td>

<td>third</td><td>Polyamide blend (Barrier agent-1)</td><td> 14%</td>

<td>Fourth</td><td>Modified polyethylene (Kl^ej-2)</td><td> 12%</td>

<td>^Piand^tand</td><td>Polyamide blend</td><td> 14%</td>

<td></td><td colspan="2">(Barrier agent-1)</td>

<td>sixth</td><td>Modified polyethylene (Kl^ej-2)</td><td> 12%</td>

<td>Seven</td><td>ionomer</td><td> 15%</td>

In Table 5 above, the first layer of Example 5 may comprise a poly (ethylene terephthalate) (PET-1) copolymer and poly (ethylene terephthalate) additives that are dried prior to mixing. The poly (ethylene terephthalate) copolymer has a density of 1.27 g / cm³, intrinsic viscosity about 0.70, gloss 45 ° 108 Hunter units (HU) and is available under the trade name EASTAR ™ Copolyester 6763 from Eastman Chemical Company, Kingsport, Tennessee, USA.

In Tables 6-9 above, the first layer of Examples 6-9 contained a copolymer of polyethylene terephthalate and ethylene glycol (PET-2) with the specified crystal density of approximately 1.4 g / cm3, intrinsic viscosity 0.80, gloss 45 ° 108 Hunter units (HU), available under the trade name ^EASTApAK™ ^pabout^lymayor ⁹⁹²¹ from ^Eastman demical Com^pany Kingsport, Tennessee, USA.

In Examples 5-6, the second layer and sixth layer were identical adhesives (Glue-2) and contained anhydride-modified polyethylene having the specified density of 0.88 g / cm3, flow rate 1.0 g / 10 minutes at temperature ¹⁹⁰°^ ^dost^ęavailable ^pabout^d name^{ą A}DM^ER® ^SF700 from M.^itsu^andPetrochemical Industries, Ltd, Tokyo, Japan.

In Examples 7-9, the second layer may comprise an adhesive (Glue-1) being a 25-99% blend, preferably 25-60% (by weight relative to the total weight of the second layer) of an ethylene / methacrylate (EMA) copolymer having a methyl acrylate content of 22 %, density 0.948 g / cm³, melt flow rate 2.0 g / 10 minutes and available under the product name SP 1330 from Eastman Chemical Company, Kingsport, TN, USA, 1-75%, preferably 175% (by weight relative to the total weight of the second layer) of linear polyethylene with low density, anhydride-modified 0.92 g / cm3, melting point 125 ° C, melt flow rate 1.5 g / 10 minutes, sold under the trade name BYNEL® 41E712, available from EI de Pont de Nemours and Company, Wilmington, DE, USA and 0-30% (by weight relative to the total weight of the second layer) polyethylene, having a density of 0.918 g / cm3, a flow rate of 1.0 g / 10 minutes and a melting point of 120 ° C, sold under the product name LL 1001 and available from Exxon Mobil Chemical Company from

Houston, TX, USA.

In examples 5-9, the third layer and the fifth layer were identical oxygen barrier agents (Barrier Agent-1) from a 85% (w / w) nylon 6 mixture with a density of 1.12 g / cm3, melting point 220 ° C, recrystallization temperature 176 ° C (when measured by differential scanning calorimetry (DSC)), available under the trade name ^ULTRAMID™ B³⁶ from ^BASF Corporation ^MCNS^t 01^andve^{, N}in Jersey, USA; and 15% (w / w) amorphous nylon with a density of 1.19 g / cm3, glass transition temperature 127 ° C, heat deflection temperature 126 ° C at 455 kPa (66 psi), sold under the trade name SELAR® PA 3426 by EI

Pont de Nemours and Company, Wilmington, Delaware, USA.

In Examples 5-8, the fourth layer contained an oxygen barrier agent (Barrier Agent-2) from an ethylene / vinyl alcohol copolymer having the specified bulk density ⁰,64^-0,74 ^{g /}cm^{3 Ge}s^tabout^SC W-Z cake^gLEDEn^{ą 1.13-1.22 g /}cm³mp 164-188 ° C, available under the name ^han^dLthat^and SOARNOL ™ ET³⁸⁰³ from ^NIPPon S^sn^the^tic Dark. in^dus^tr^sCompany, Ltd (Nippon Gohsei), Osaka, Japan.

In example 9, the fourth layer may be an adhesive (Glue-2) of anhydride-modified polyethylene, with a density of 0.88 g / cm³, melt flow rate 1.0 g / 10 minutes at 190 ° C, available under the trade name ^ANDDM^ER® SE⁷⁰⁰ from MAsui Petrosemical ^ANDndustries^{, Lt}^ ^Tabout^kiabout^,Japan.

In examples 5-7 and example 9, the sixth layer contained glue (Adhesive-2 from anhydride-modified polyethylene with the specified density of 0.88 g / cm3, flow rate 1.0 g / 10 minutes at 190 ° C, available under the trade name ADMER® SF700 from Mitsui Petrochemical Industries, Ltd, Tokyo, Japan.

In Example 8, the sixth layer may comprise adhesive material (Glue-1) as used in the second layer of the same example described above.

In Examples 5-7 and Example 9, the seventh layer contained a sealant of the partial zinc salt of ethylene methacrylic acid copolymers with a density of 0.940 g / cm3, a melt flow rate of 1.30 g / 10 minutes at temperature ¹⁹⁰° ^ softening temperature according to^g Vicat ^73,9° C (¹6⁵°^E)_/. sold under the trade name SURLYN® 1601 from EI Pont de

Nemours and Company, Wilmington, Delaware, USA.

In Example 8, the seventh layer may be identical to the polyethylene terephthalate used in the first layer of this example as described above.

In examples 5-9 one extruder could be used for each layer. Each extruder was connected to an annular coextrusion die that coextruded heat-plasticized resins to form a tube or single bladder with seven layers.

The resin or resin mixture was fed from the feed hopper to the associated single screw extruder, where it was plasticized under the influence of heat and extruded through a seven-layer coextrusion die as a tube or a single bladder. The extruder body temperature for the first layer was 260 ° C (500 ° F); for the second layer²66 ° C (⁵¹⁰F) ^{and for}and ^tsay^andabove ^daxis^iOin layers^{y 271}° C (5²°° F). The bladder width was kept below 1.346 m (53 inches). The extruded multilayer bladder was cooled on a cooled solid surface. The cooled bladder was flattened with a pair of rollers and each of the resulting films of Examples 5-9 had an average thickness in the range of 0.1016 to 0.1524 mm (4-6 mils).

Table 10 gives a comparison of the amount of elongation at break in the longitudinal direction and the transverse direction for a seven-layer film (Example 5) having different thicknesses according to the present invention. Table 11 shows a comparison of the magnitude of the free linear thermal shrinkage in the longitudinal direction and the transverse direction for a seven-layer film (Example 5) having different thicknesses according to the present invention.

Table 10

<td colspan="4">Comparison of% elongation at break for</td><td colspan="2">example 5</td>

<td>0, ° 762mm (3</td><td>mils)</td><td colspan="2">⁰, ¹²⁷mm (⁵to me^lica^land)</td><td>^{0 , 2 5 4} mm</td><td>¹⁰ to me^lica^land)</td>

<td>Along</td><td>IN</td><td>Along</td><td>Across</td><td>Along</td><td>Across</td>

<td> 3 8 6 ^, 8</td><td> 4 8 4 ^, 4</td><td> 519^,6</td><td> 575 ^,0</td><td> 643^,6</td><td> 612 ^, 9</td>

<td> 4 6 9 ^, 1</td><td> 4 3 4 ^, 1</td><td> 516^,8</td><td> 529,. 8</td><td> 630^,8</td><td> 600 ^,4</td>

<td> 412^,1</td><td> 4 5 9 ^, 3</td><td> 513^,4</td><td> 579^,2</td><td> 615^,2</td><td> 5 99 ^,2</td>

<td> 4 2 9 ^, 3</td><td> 4 5 8 ^, 7</td><td> 518^,9</td><td> 562^,3</td><td> 637^,1</td><td> 63 9 ^, 0</td>

<td> 4 0 6 ^, 1</td><td> 4 2 7 ^,1</td><td> 48 4 ^,0</td><td> 551^,8</td><td> 605^,1</td><td> 5 90 ^, 2</td>

<td>AVE 4 2 0 ^, 7</td><td> 4 5 2 ^, 7</td><td> 510^,5</td><td> 559^,l 6</td><td> 626^,4</td><td> 608 ^, 3</td>

Table 11

<td colspan="3">Comparison of% free linear heat shrinkage for example 5</td>

<td>Thickness</td><td>Longitudinal direction</td><td>Transverse direction</td>

<td>^{0, 07}62 mm (³ mMMaM)</td><td> 0, 0%</td><td> 0, 0%</td>

<td>^0,127 mm (⁵ m^ilica^l)</td><td> 1,5%</td><td> 0,5%</td>

<td>^0,254 mm (¹⁰ m^ilica^l)</td><td> 1, 0%</td><td> 0, 0%</td>

Unless otherwise noted, the physical and performance properties given herein were measured in test procedures similar to the following methods.

Density

ASTM D-1505

<td>Melting temperature</td><td>ASTM</td><td>D-3418</td>

<td>Melt flow rate</td><td>ASTM</td><td>D-1238</td>

<td>Molecular Weight</td><td>ASTM</td><td>D-3593-80</td>

<td>Oxygen penetration rate</td><td>ASTM</td><td>D-3985-81</td>

<td>Percentage of elongation at break</td><td>ASTM</td><td>D-638</td>

<td>Free linear thermal shrinkage</td><td>ASTM</td><td>D-2732-96</td>

<td>Softening point by the Vicat method</td><td>ASTM</td><td>D-1525</td>

One skilled in the art can develop many modifications and other embodiments of the invention to which this invention relates, using the information provided in the preceding description and the related drawings. Therefore, it should be understood that the invention is not limited to the specific embodiments disclosed and that the modifications and other embodiments should fall within the scope of the appended claims. Although specific terms are used herein, they are used only in a general and descriptive sense and not for limiting purposes.