MXPA97005065A - A multi-layer plastic film, uses to pack a coo food material - Google Patents

Abstract

A multilayer film, preferably biaxially oriented, suitable for processing and / or packing cooked foods indoors, such as ham, beef, and poultry, which has an excellent combination of oxygen barrier properties, heat seal , and optical, comprising at least five essential layers in sequence, with a first layer of a propene copolymer and at least one alpha-olefin of 2 to 8 carbon atoms having a propene content of at least 60 weight percent , and that preferably has a melting point -140 ° C, a second layer of (1) a first copolymer of ethylene and at least one alpha-olefin of 4 to 8 carbon atoms having a density of 0.900 to 0.915 grams / cubic centimeter , and a melting point less than 1.0 decigram / minute, (2) a second ethylene copolymer with 4 to 18 percent, preferably 4 to 12 percent, of vinyl ester or alkyl acrylate, (3) a third snowflake ethylene polymer with at least one alpha-olefin, vinyl ester, or an alkyl acrylate, modified with anhydride, and (4) optionally a fourth copolymer of ethylene and at least one alpha-olefin of 3 to 8 carbon atoms having one density less than 0.900 grams / cubic centimeter, and a melting point less than 85 ° C, a third layer of EVOH, a fourth layer as the second layer, and a fifth layer of a first ethylene copolymer with at least one alpha-olefin 4 to 8 carbon atoms having a density of 0.900 to 0.915 grams / cubic centimeter, and a melting index of less than 1.0 decigram / minute, and a second ethylene copolymer with 4 to 18 percent, preferably of 4 to 12 percent , of a vinyl ester or alkyl acrylate, and optionally a third copolymer of ethylene and at least one alpha-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85.

Description

A MULTI-LAYER PLASTIC FILM. USEFUL TO PACK A COOKED FOOD MATERIAL Background of the Invention The present invention relates to improvements in the technique of packaging food materials, especially cooked foods, such as for example ham, beef, and turkey breasts. In the discussion of plastic film packaging, different polymer acronyms are used herein, and are mentioned immediately. Also, when referring to polymer blends, two points will be used (:) to indicate that the components are mixed to the left and to the right of the two points. When referring to a film structure, a diagonal "/" will be used to indicate that the components to the left and right of the diagonal are in different layers, and the relative position of the components in the layers can be indicated in this way by using the diagonal to indicate the limits of the film layer. Acronyms commonly used herein include: PP - polypropylene homopolymer. PE-polyethylene (a homopolymer and / or copolymer of ethylene and a greater part of ethylene with one or more α-olefins).

EVA - ethylene copolymer with vinyl acetate. PVDC-polyvinylidene chloride (also includes copolymers of vinylidene chloride, especially with vinyl chloride). EVOH - a saponified or hydrolyzed copolymer of ethylene and vinyl acetate. EAA - ethylene copolymer with acrylic acid.

Different published patent documents describe different types of packaging films for applications in cooked foods and in other processing or packaging applications. U.S. Patent No. 4,724,185 (Shah) discloses a five-layer co-extruded oriented film having a core layer of an EVOH-nylon blend bonded to outer layers of a linear low density polyethylene linear polyethylene blend. of medium density, and EVA, using intermediate layers of an adhesive resin modified with acid anhydride. The film radiates. U.S. Patent No. 4,726,984 (Shah) discloses a shrinkable film co-extruded into five layers having an EVOH core layer bonded by adhesive layers to the opposite outer layers of an ethylene-propylene copolymer blend (2). -5 weight percent C), and polypropylene. U.S. Patent No. 4,469,742 (Oberle) discloses a six-layer heat shrinkable film for cooking, which has examples including a random copolymer structure C3C2 / EVA / anhydride-grafted adhesive / EVOH / anhydride-grafted adhesive /EVE. The EVA can be replaced with homopolymer or ethylene copolymer, such as linear low density polyethylene. The film can be cross-linked by irradiation and extrusion. A comparative example of a five layer film having a random copolymer structure C3C2 / EVA / adhesive or grafted with anhydride / EVOH / EVA is also presented. U.S. Patent No. 4,857,399 (Vicik) discloses a four-layer shrinkable film comprising a random copolymer of ethylene-propylene as a first layer in contact with meat, a mixture of EVA and an anhydride-modified adhesive resin as a second intermediate layer, a barrier core layer of EVOH-nylon blend, and a mixture of anhydride-modified adhesive and EVA as a fourth layer. U.S. Patent No. 5,382,470 (Vicik) discloses a heat shrinkable, cross-oriented, stretch film, for food packaging, having a core layer of EVOH-nylon 6/66 copolymer connected by intermediate adhesive layers to the opposite outer layers. It is described that the adhesive layers are specific mixtures of resins, including very low density polyethylene, EVA, and adhesive resins. PE or EVA modified with anhydride. The outer layers may comprise a mixture of very low density polyethylene, EVA, and plastomeric ethylene-α-olefin copolymer. U.S. Patent No. 5,397,613 (Georgelos) discloses a heat-shrinkable film of at least one 50 percent shrinkage, which has a C2 α-olefin layer (p = .88-0.905; p.f. < 100; w / Mn < 3) that can have EVA and another α-olefin C2 mixed in it. This film can have on both sides a barrier layer that can be EVOH. The Patent of the United States of North America Number 4,888,223 (Sugimoto et al.) Discloses a heat-shrinkable, multilayer tubular film having a possible polyolefin / modified polyolefin / gas barrier / modified polyolefin / polyolefin structure, wherein the inner contact layer with the meat it is treated with a crown at a level of at least 35 dynes / centimeter ro. The inner layer may be a polypropylene copolymer. The modified polyolefin can be a linear low density polyethylene grafted with maleic anhydride. The gas barrier can be EVOH.

European Patent Number EP 561,428 (Fant et al.) Claims a multilayer film comprising a core layer of an ethylene-vinyl alcohol copolymer; two external polymeric layers; two internal layers of a polyolefin adhesive polymeric material modified with acid or with acid anhydride to bond the outer layers with the core layer. A dependent claim specifies that both outer layers may comprise C3C2 copolymer. European Patent Number EP 457,598 (Shah et al.) Describes a multilayer film based on polyamide to pack cheese. This polyamide film is described as having "an oxygen transmission rate of not more than 500 cubic centimeters / square meter, 24 hours, atmosphere." Example 5 purportedly describes a biaxially oriented film of one thousandth (25.4 microns) thick, having a core layer comprising a mixture of about 70 percent EVOH and about 30 percent of a polyamide in combination with external layers based on polypropylene or propylene copolymer, and this film has a shrinkage reported at 220 ° F (104 ° C) of 24 percent in two directions Patent Number PCT 94/07954 (Kaeding), assigned to DuPont, has extensive claims which relate to a shrink film comprising a mixture of a first polyolefin (p. = 0.92 grams / cubic centimeter; Mw / n of 1-4; pf <115 ° C; a single narrow pf) with a second polyolefin having a melting point that is 10 ° C higher than the melting point of the first polyolefin, and an orientation temperature at least 2 ° C lower than its melting point. Multilayer structures having a core layer of the above with an outer layer of C3C2 copolymer or polypropylene are also described. Different multilayer thermoplastic films have been marketed to pack meats, cheeses, and cooked food materials. Films of three to six layers are common. Typical structures include: PP / adhesive / nylon, EVA / PVDC / EVA: PE, PE: EVA / PVDC / PE: EVA, Ionomer / EVA / adhesive / EVOH / adhesive / EVA, PE: EVA / PE: adheSive: EVA / EVOH / PE: adhesive: EVA / PE: EVA, Nylon / EVA / adhesive or / EVOH / adhesive / EVA, copolymers C3C2 / EVA / adhesive / EVOH / adhesive / EVA, and variations thereof, where they are mixed polyethylene copolymers in one or more layers of EVA. Some packaging films can shrink by heat at 90 ° C, and others can not. Some are cross-linked by irradiation and / or corona treated or not. Some of the non-shrink films have an oxygen barrier comprising one or more layers of nylon or EVOH, or a mixture of EVOH with nylon. These non-shrink films are known structures include EVA: PE / nylon, EVA: PE / Nylon / EVOH / EVA: PE, EVA: PE / PVDC / Nylon, EVA: PE / EVOH / Nylon, and EVA: PE / Nylon / EVA. Films containing EVOH that are not shrinkage generally have a relatively thick EVOH-containing layer, generally more than 0.5 mil (12.7 microns). Thin, heat shrinkable, multilayer EVOH barrier oriented films have been taught in U.S. Patent No. 5,382,470 and in the U.S. patent application serial number 08 / 191,886, filed on February 3, 1994, both of which are incorporated herein by reference in their entirety. Of the non-shrink films above, those containing EVOH have a typical oxygen permeability of less than 10 cubic centimeters per square meter at one atmosphere, at a relative humidity of 0 percent and at 23 ° C, and are considered to be high barrier. The terms "barrier" or "barrier layer", as used herein, mean a layer of a multilayer film that acts as a physical barrier to gaseous oxygen molecules. Physically, a barrier layer material will reduce the oxygen permeability of a film (used to form the bag) to less than 70 cubic centimeters per square meter in 24 hours at one atmosphere, at 73 ° F (23 ° C) and with a relative humidity of 0 ° C.

These values should be measured in accordance with the ASTM D-1434 standard. Suitable films are also known for packaging food materials that can be heat shrunk at 90 ° C, which contain nylon or a mixture of EVOH and nylon. Axially stretched films, especially biaxially stretched, which are "heat shrinkable" as that term is used herein, have at least an unrestrained shrinkage of 10 percent at 90 ° C (10 percent both in the direction of machine (MD) as in the transverse direction (TD) for biaxially stretched films). These known films include structures of the following types: Ionomer / PE / Nylon, Ionomer / EVA / Nylon, EAA / Nylon: EVOH / Ionomer, and PE / EVOH: Nylon / PE. Some of these heat shrinkable films containing EVOH have an oxygen permeability in the high barrier range. Also, the recycling of PVDC polymers is difficult, particularly where the waste polymer is mixed with other polymers having different melting points. Attempts to remelter the PVDC-containing film often result in degradation of the PVDC component. For this reason, EVOH has been used as an alternative barrier layer. However, the use of EVOH in multilayer structures often leads to undesirably poor optimum properties, especially high haze, and to film structures that are difficult to process and orient. EVOH is a very rigid material, and layers containing EVOH often delaminate from the adjoining layers, or crack during processing and orientation, thereby exhibiting undesirable lines, lines, and other optical properties. Commercially available bags are made by transversally sealing a tubular material of either a single layer or multilayer film, and cutting the tube portion containing the sealed end, or by making two separate transverse seals on a tubular material, and cutting to open the side of the tube, or superimposing flat sheets of the film, and sealing on three sides, or bending at the end the flat sheets and sealing two sides. In general, the heat sealing of the thermoplastic film is carried out by applying sufficient heat and pressure to the adjacent surfaces of the film layer, for a time sufficient to cause a fusion bond between the layers. A common type of seal used in the manufacture of bags is known to the experts in this field as a hot rod seal. By making a hot bar seal, the adjacent thermoplastic layers are stopped together by opposite rods, at least one of which is heated to cause the adjacent thermoplastic layers to be melt bonded by the application of heat and pressure through the area that is going to seal. For example, bags can be manufactured from a tube supply by making a hot rod seal transverse to the tube. This seal can also be referred to as a lower seal. Once the lower seal is applied, the tube supply can be cut transversely to form the mouth of the bag. Once a food product, such as meat or poultry, is inserted into the bag, the package is typically evacuated, and the mouth of the bag is sealed. At some time, the conventional method of sealing a bag was to put a fastener around the mouth of the bag. Although this method is still used, more recently heat sealing techniques have been used to seal the bags. For example, the mouth of a bag can be sealed with a hot bar, or it can be sealed by another type of heat seal known as an impulse seal. An impulse seal is made by the application of heat and pressure, using opposite bars similar to the hot bar seal, with the exception that at least one of these bars has a covered wire or ribbon through which electric current is passed during a very short period of time (hence the name "impulse"), to make adjacent film layers bond by fusion. Following the heat pulse, the rods are cooled (eg, circulating coolant), while continuing to hold the inner surfaces of the bag together, to achieve adequate seal strength. One problem that arises during the heat seal of the known films is that the film that is in the area of the seal frequently becomes extruded during sealing. This results in a thinning of the film in the area of the seal, and therefore, reduces the strength of the film in the seal, or in extreme situations, allows the thin film to be cut or separated too easily. Experts in this field refer to severely extruded stamps as "burned" stamps. Therefore, a "burned" seal does not have adequate strength or integrity to seal or protect the packaged product. An attempt to solve this problem of "burning" is to irradiate the film before making the bag. The irradiation of a multilayer film causes the different irradiated layers of the film to crosslink. Under controlled conditions, crosslinking by irradiation elevates and can also extend the temperature range for heat sealing, and can also improve the puncture resistance of the film. In an inconvenient manner, if the heat sealing layer of the thermoplastic film is too crosslinked, the highly crosslinked layer is more difficult to melt bond, which makes it difficult to achieve strong seals, particularly by the impulse sealing of the mouths. the bags after filling with meat or poultry. All bag seals (including those made by both bag manufacturers and the food processor, and by any means, including hot-rod seals and impulse seals) must maintain their integrity to preserve and protect the enclosed food product. . There must be a strong continuous seal to prevent discharge and unwanted entry of gaseous, liquid, or solid materials between the outside and the inside of the bag. This is particularly necessary when the package containing food is made of heat-shrinkable film, and must be cooked in steam or hot water, and / or submerged in hot water, to shrink the film against the packaged food, since this shrinkage increases the tension on these seals. Accordingly, there is a continuing need for multilayer films that can be formed into bags having strong seals, especially when formed by hot bar sealing or impulse sealing. These films must provide strong seals capable of withstanding a range of temperatures, and they must also be capable of producing these seals over a wide unburned sealing temperature range. It is known that there are variations in temperatures, times, and sealing pressures, not only of one brand and / or type of sealants to others, but also between different sealing machines sold by the same manufacturer under the same brand identification. These variations, which may be due to factors such as the variation in the manufacturer's product, or the variation in the establishments or installation of the equipment, increase the desire for films that can be sealed by heat to produce strong integral seals over a wide range of temperatures, and therefore, that are sealingly sealed in different sealing machines. Another problem encountered during heat sealing is that of inadvertent bending. Normally, a heat seal is made by applying heat and pressure through two sheets or portions of film, for example, the two opposite sides of a flattened tube, - however, occasionally the area to be sealed is Inadvertently bends to produce a section of film having four or six sheets or portions of film that are compressed between the opposing sealing bars. In those situations, it is desirable to be able to seal the film without burn. A wider pulse heat seal temperature range indicates a greater latitude in the seal through the bends than a narrower range.

SUMMARY OF THE INVENTION It is an object of the invention to provide a multilayer film having a low oxygen permeability. It is still another object of the invention to provide a film having a low water vapor permeability. It is another object of the invention to provide a multilayer film having a controllable meat adhesion. It is another object of the invention to provide a multilayer film containing EVOH that is resistant to delamination. It is another object of the invention to provide a film of sufficient integrity to support the cooking process with intact film seals and layers. It is another object of the invention to provide a heat sealable film capable of forming high strength melt bonds. It is another object of the invention to provide a multilayer film containing EVOH, which has high shrinkage values at 90 ° C or less. It is a further object of the invention to provide a multilayer film crosslinked by irradiation, having an EVOH core layer, having a wide impulse heat sealing voltage range. It is still another object of the invention to provide a multilayer film containing EVOH, which has good optical properties. It is a further object of the invention to provide a chlorine-free packaging film. It is an object of the invention to provide a film for packaging food, such as hams, that are cooked and shipped in the same film. It is another object of the invention to provide a cooked food material packaged using a multilayer film having an oxygen barrier layer. The foregoing and other objects, benefits, and advantages of the invention will become clearer from the following description, which is exemplary and not limiting. It is not necessary that each and every object mentioned above be found in all the embodiments of the invention. It is sufficient that the invention can be usefully employed. According to the present invention, an article, such as a food material, especially ham, is packaged in a flexible, thermoplastic, multilayer film of at least five layers configured in sequence (first, second, third, fourth, fifth). ) and in contact with each other. The first layer comprises at least 50 weight percent of a propene copolymer, and at least one α-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1. , and mixtures thereof, having a propene content of at least 60 weight percent. The second layer is comprised of a mixture of: (i) at least 10 percent of a first copolymer of ethylene, and at least one α-olefin of 4 to 8 carbon atoms having a copolymer density of 0.900 to 0.915 grams / cubic centimeter, and a melt index less than 1.0 decigram / minute, and (ii) at least 10 percent of a second ethylene copolymer with 4 to 18 percent vinyl ester or alkyl acrylate, and ( iii) at least 10 percent of an ethylene copolymer with at least one α-olefin, a vinyl ester, or an alkyl acrylate, modified with anhydride, and optionally from 0 to 30 percent of a fourth ethylene copolymer and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85 ° C. The second layer may also optionally contain a propene copolymer as described above for the first layer. The third layer is a core layer comprising at least 80 percent by weight, preferably at least 90 percent by weight of ethylene-vinyl alcohol copolymer, having an ethylene content of about 38 mole percent or higher In a preferred embodiment, this third layer can have a thickness of approximately 0.05 to 0.3 thousandths (from 1.7 to 7.62 microns), and preferably from 0.14 to 0.2 thousandths (from 4.1 to 5.1 microns). The fourth layer may be the same as or different from the second layer, but is comprised of a mixture of resins as described above for the second layer. The coating layer comprises a mixture of: (i) at least 30 percent of a first copolymer of ethylene with at least one α-olefin of 4 to 8 carbon atoms having a copolymer density of 0.900 to 0.915 grams / centimeter , and a melt index of less than 1.0 decigram / minute, - (ii) at least 10 percent of a second ethylene copolymer with 4 to 18 percent of an alkyl vinyl ester or alkyl acrylate; and (iii) optionally from 0 to 30 percent of a third copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a lower melting point of 85 ° C. Preferably, the film of the invention may be sealed by heat, having at least one layer that is crosslinked, preferably by irradiation. In a highly useful embodiment of the invention, the film may be shrunk by heat at temperatures such as 90 ° C or lower, and may have shrinkage values in the machine direction and in the transverse direction of the machine when less about 20 percent, and, conveniently, for example, to pack cooked foods such as ham or chicken breasts, can be at least 30 percent. In one embodiment of the invention, a process for manufacturing the above-described film is claimed. The film is useful for processing and / or packaging items, especially food materials such as ham, beef, poultry, or processed meat, which can be cooked inside the film.

Detailed Description of the Invention The film, bag, process, and package of the present invention can be used as a heat-sealable oxygen and moisture barrier film to contain a food material during cooking and / or to pack for the sale of said food material after a period of pasteurization or cooking. The present invention is particularly suitable for processing and packaging pasteurizable foods, and has a particular utility in packing cooked hams indoors. "Cooked inside" is the term used to indicate a film or bag in which the food material is pasteurized or cooked. This film or bag is used to hold together, protect, and / or shape the food material by means of a food processor (manufacturer) during the cooking or pasteurization process, after which the film can be removed (sometimes called "separate"), or can be left on top as a protective barrier during shipment, and optionally left over during retail sale. Some of the benefits of the film of the invention include: a relatively low permeability to oxygen and water vapor; a high resistance to delamination, and an unexpectedly good combination of resistance to delamination, especially at elevated temperatures that simulate the cooking conditions inside, and possibility of orientation which results in a good possibility of shrinkage by heat at low temperature; resistance to degradation by acids from food, salts, and fat; high shrinkage values at low temperatures (90 ° C or lower); residual shrink force that forms and maintains a compact product; an adherence to controllable meat; a possibility of heat sealing from good to excellent, especially over a wide voltage range in commercial sealants; low levels of extractables, with compliance with government regulations for contact with food, - low nebulosity; High brightness; does not impart bad tastes or smells to packaged food; good tensile strength, - a surface that can be printed; high resistance to heat seal, and a durable seal, especially at cooking temperatures inside, - and good machinability. Conveniently, a preferred embodiment of the invention has low permeabilities to 02 and water vapor in combination with a high adhesion to the meat, which prevents the undesirable cooking of liquid outside during processing, a good possibility of seal by heat, and high values of shrinkage at low temperature (90 ° C or less). In an especially preferred embodiment, the film of the invention has shrinkage values of at least 20 percent (more preferably about 30 percent or higher) in at least one direction at 90 ° C or less, and preferably at least 25 percent in both directions. Also, preferred films can be heat sealed over a wide voltage range, and can preferably be heat shrunk at low temperatures in combination with that possibility of heat sealing over a wide range. Also, the oxygen barrier properties of the film of the invention reduce or eliminate the losses by decomposition, for example, by rancidity due to oxidation. The films and bags of the invention are particularly useful for packing food materials baked in, but they can also be used to pack a wide variety of food and non-food items. The present invention can be used as bags in the different typical sizes. "Flat width" means the transverse width of a flattened tubular film. The flat width is also equal to half the circumference of the tubular film. The invention, in all its embodiments, comprises or utilizes a multilayer thermoplastic polymer flexible film of 10 thousandths (254 microns) or less, having a propene-based copolymer layer for good contact, which provides a good possibility of heat sealing , an EVOH gas barrier layer, an abuse resistant outer layer, and adhesive layers using a combination of high molecular weight, low molecular weight, highly branched, and substantially linear polymers to produce a surprisingly orientable film that It has a high resistance to delamination, even under cooking conditions inside. The layer containing EVOH controls the gas permeability of the film. The propene-based copolymer-containing layer controls the possibility of adhesion of the film to an enclosed food, which for meat is called "meat adhesion", and also controls the possibility of heat sealing and seal resistance, particularly at temperatures elevated and through time. The adhesive layers control the delamination resistance of the core layer of EVOH, and in a beneficial way improve the possibility of orientation. These films will preferably have a thickness of approximately 2 to 3 thousandths (from 50.8 to 76.2 microns), although suitable films can be made to pack food materials as thick as 4 thousandths (101.6 microns), or as thin as one thousandth (25.4 microns). Typically, the films will be between approximately 1.5 and 3 thousandths (from 38.1 to 76.2 microns). They are especially preferred for use as films for packing cooked meats indoors, the films wherein the multilayer film has a thickness between about 2 and 3 mils (50.8 to 76.2 microns). These films have a good resistance to abuse and machinability. Films thinner than 2 thousandths 50.8 microns are less resistant to abuse and more difficult to handle in packaging processes. Conveniently, preferred films can be shrunk by heat. Preferred films can also provide a beneficial combination of one or more or all of the properties, including low haze, high gloss, high shrinkage values at 90 ° C or less, good machinability, good mechanical strength and good barrier properties, including high barriers to oxygen, and water permeability. Suitable films of the present invention may have a low nebulosity and a high gloss, for example, a haze of less than 20 percent, and a brightness greater than 50 Hunter Units (H.U.) at 45 °. Conveniently, some preferred embodiments of the present invention may have cloudiness values of less than 10 to 12 percent, and preferably less than 6 percent, and very high brightness values, eg, greater than 65 Hunter Units, and preferably Greater than 75 Hunter Units. The article of the invention is preferably a multilayer film that can be shrunk by heat, which must have at least five layers. These five essential layers are called the first layer, the second layer, the third layer, the fourth layer, and the fifth layer. The first layer and the fifth layer are disposed on the opposite sides of the third layer, and preferably joined thereto by the second and fourth adhesive layers, respectively. These five layers are essential for the film of this invention. When the film is in the form of a tube or a bag, these layers comprise the wall of the tube or bag. This wall, in cross section, has the first layer comprising an outer layer disposed closer to the inner surface of the tube (or bag), the fifth layer being an opposite outer layer typically disposed closer to the outer surface of the tube (or the bag). In accordance with the present invention, it is contemplated that tubular films having more than five layers can be constructed, and that these additional layers can be arranged as additional intermediate layers remaining between the third layer (also called the core layer), and either or both of the first and fifth layers, or these additional layers may comprise one or more surface layers, and may comprise either or both of the inner or outer surfaces of the tube. Preferably, the first layer will comprise the inner surface layer of the tube, where in use, it will contact a food material enclosed by the tube. Beneficially, this first layer will be sealable by heat to facilitate the formation of hermetically sealed bags and packages. Conveniently, the first layer as the inner surface layer, when used to pack food materials, will be suitable for contact with food materials containing protein, water, and fat, without releasing or imparting harmful materials, off-flavors or smells to the food material. Beneficially, the first layer may be the inner surface layer, and may consist essentially of a propene-to-olefin copolymer. If desired, an ionomeric resin may be used, either alone or mixed in one or more of the layers, but this use is unnecessary to produce a suitable film for packing cooked food materials therein. Conveniently, the heat seal layer, and really the entire film, may be free of ionomer polymer, and yet provide an entirely satisfactory performance without the added expense of using the expensive ionomer resin. Also, it is preferred that the fifth layer comprises the outer surface of the tube or bag. Like the outer surface layer of the tube or bag, the fifth layer must be resistant to abrasions, abuse, and stress caused by handling, and must also be easy to machine (ie, it must be easy to feed to through, and manipulated by, machines, for example, to be transported, packaged, printed, or as part of the manufacturing process of the film or the bag). It should also facilitate stretch orientation where a high shrink film is desired, particularly at low temperatures such as 90 ° C and lower. Conveniently, the first layer will be predominantly comprised of propylene copolymers having a propylene content (propene) of 60 weight percent or more. This layer is preferably an inner surface layer of the tube or bag. The surface layers function to protect the core layer from abuse, and may also protect it from contact with moisture, which may impact or may alter the gas barrier properties of the EVOH and / or nylon core layer. Beneficially, in the present invention, there are intermediate adhesive layers on either side of the EVOH core layer (third layer). The second layer of this film is generally an unusually thick adhesive layer, which, in addition to providing resistance to delamination between the adjacent EVOH layer and the opposing layer, also contributes to facilitate orientation, and facilitates the formation of a film biaxially stretched having high shrinkage values, particularly at low temperatures (90 ° C or lower) in combination with optical properties that are superior to those of many films of the prior art. The use of an adhesive layer directly adhered to either side of the core layer, produces a film that is extremely resistant to desiamination, and that can be oriented to produce a film that has a high shrinkage of 30 percent or higher. 90 ° C or less. In a preferred embodiment, the core layer of EVOH adheres directly to the second and fourth layers, which function as adhesive layers, and in turn, optionally adhere directly, respectively, to any of the layers (or preferably both ) internal (first) and external (fifth). In a more preferred embodiment, the film article consists essentially of five polymeric layers, i.e., the inner layer (first), the adhesive layer (second), the core layer (third), the adhesive layer (fourth), and the outer layer (fifth). This preferred embodiment provides a desirable combination of properties, such as low moisture permeability, low slurry permeability, controllable meat adhesion, high gloss, good mechanical strength, chlorine-free construction, and desirable shrinkage forces in a film of multilayer packaging, shrinkage by heat at low temperature, which is resistant to delamination, heat sealable, and which can be oriented biaxially. The core layer optionally may have processing aids or plasticizers. Optionally, nylon can be incorporated in amounts of up to 20 weight percent. Typical layer thicknesses for the essential layers of the heat-shrinkable film of the invention may be from about 5 to 40 percent of the first layer (typically the inner surface), from 25 to 70 percent of the second layer (adhesive), from 3 to 13 percent of the third layer (core), from 1 to 35 percent of the fourth layer (adhesive), and from 10 to 50 percent of the fifth layer (external), although films with different thicknesses are possible in the proportion of layers. The first layer is typically an outer surface layer of the film, and in a tubular construction, it is the inner surface layer of the tube. The function of the first layer is to provide a layer having a controllable meat adhesion, and a surface that can be sealed by heat with itself (or with the second outer layer if an overlapped seal is desired), in the commercially available equipment , and (for food packaging), provide a hygienic surface for contact with food material. In the present invention, to satisfy these functions, the thickness of the first layer need not be large, but for a convenient combination of ease of processing and operation of the seal, this layer will preferably be 0.1 to 1.2 thousandths (from 2.54 to 30.40 thick). It is important that this heat sealable layer be continuous eg on the inner surface of the tube, and that it be extruded in sufficient thicknesses to allow heat sealing (if desired). Preferably, the first layer is an outer heat sealing layer that allows the film to be formed into bags. The term "heat sealing layer" means a layer that can be heat sealed with itself, that is, capable of melt bonding by a conventional indirect heating element that generates sufficient heat on at least one contact surface with the film to conduct itself to the contact surface with the adjacent film, and the formation of a link interface between them without losing the integrity of the film. Conveniently, the bonded interface must be sufficiently thermally stable to prevent leakage of gas or liquid therethrough when exposed to higher or lower ambient temperatures during food processing inside the tube when sealed at both ends, that is, in a sealed bag form. For use in indoor cooking applications, heat seals must withstand elevated temperatures of up to approximately 160 ° F to 180 ° F (71 ° C to 82 ° C) or higher for extended periods of time, for example, up to 4 to 12 hours, in environments that can range from humidified and heated air or steam, to immersion in heated water. Finally, the interfaced interface between the adjacent inner layers must have sufficient physical strength to withstand the stress resulting from stretching or shrinkage due to the presence of a food body sealed inside the tube, and optionally subjected to temperatures and conditions of pasteurization or cooking inside. Unless indicated otherwise in the present application, the percentages of the materials used in the individual layers are based on the weight of the indicated layer. The percentage of the comonomer content of a particular polymer is based on the weight of the indicated polymer. The first layer, especially as the inner surface layer of a tube in accordance with the present invention, also provides good machinability, and facilitates the passage of the film on the equipment (for example, to insert food materials). This layer can be coated with a powder against blocking. Also, conventional blocking additives, polymeric plasticizers, or skimming agents may be added to the first outer layer of the film, or may be free of those additional ingredients. When this layer is corona treated, optionally and preferably no slip agent will be used, but it will contain or be coated with a blocking powder or agent, such as silica or starch. In one embodiment of the invention, the first outer layer consists essentially of a propene copolymer, or mixtures thereof. Propene copolymer resins suitable for use in the first layer have a propene content of at least 60 weight percent, optionally at least 80 weight percent. Optionally and preferably, these copolymers will have a content of at least 90 weight percent propene. Copolymerized with the propene will be at least one α-olefin selected from the group consisting of ethylene, butene-1, hexene-1, methylpentene-1, octene-1, and mixtures thereof, in an amount up to 40%. cent in weight. The propene and ethene bipolymers (^ C2 copolymers), as well as the C3C4 bipolymers and the C3C2C4 terpolymers are preferred. More preferred are C3C2 copolymers, especially bipolymers. A preferred C3C2 copolymer can have a propene content of at least 90 percent, and optionally at least 95 percent by weight. Preferred propene copolymers have a melting point between about 126 ° C and 145 ° C, more preferably between about 129 ° C and 136 ° C. The propylene random copolymers are preferred. A preferred copolymer is commercially available at Solvay &; Cié as a bioriented film-grade resin under the registered trademark Eltex P KS 409. As reported, this resin is a random copolymer of propylene and ethylene that has a melting point lower than 136 ° C, a density (p) of approximately 0.895 grams / cubic centimeter, a Vicat softening point of approximately 120 ° C (ASTM 1525 (l Kg) and a melt index of 230 ° C and 2.16 kilograms of approximately 5 decigrams / minute. of the invention comprises a propene copolymer, and has an adhesion to controllable meat.The adhesion attribute to the meat of the film can be controlled by the absence, the presence, and / or the degree of surface energy treatment, by example, by corona discharge The films of the present invention that had not been corona treated on their inner surface layer (first layer), they will have a typical surface energy of at least 29 dynes per centimeter, and typically less than 33 dynes per centimeter. The corona treatment of the first layer can raise the surface energy to levels of at least 33 dynes / centimeter, preferably at least 34 dynes / centimeter. More preferably, levels of about 35 to 38 dynes / centimeter will normally be employed to produce films of the invention having a high adhesion to the meat. Films that have a high adhesion to the meat lessen the external cooking of the juices of the meat, which, if not prevented, can lead to weight loss of the product. Also, external cooking can produce an undesirable appearance of the package for applications where the processing / packaging film is intended to be left on the product for sale and use after processing. Films of the invention with low meat adhesion will find use in cooking and separation applications, where the film is typically removed from the food material enclosed directly after cooking or pasteurization. The product, after removing the film, is further processed or repacked. The low adhesion films to the meat of the invention will typically have a surface energy less than 33 dynes / centimeter. The core layer functions as a barrier to controlled gas, and provides the barrier to the 02 necessary to preserve the item to be packed. It should also provide good optical properties when it is oriented in a straight line, including a low nebulosity and a stretching behavior compatible with the surrounding layers. It is desirable that the thickness of the core layer be less than about 0.45 mils (10.16 microns), and greater than about 0.05 mils (1.27 microns), to provide the desired combination of the desired performance properties, for example, with respect to oxygen permeability, shrinkage values, especially at low temperatures, ease of orientation, resistance to delamination, and optical properties. Suitable thicknesses are less than 15 percent, for example, from 3 to 13 percent of the total thickness of the film. Preferably, the thickness of the core layer will also be less than about 10 percent of the total thickness of the multilayer film. The core layer comprises EVOH, which will control the oxygen permeability of the film. For the packaging of perishable foods, oxygen permeability (02) should desirably be minimized. Typical films will have an oxygen permeability of less than about 20 cubic centimeters / square meter for a period of 24 hours at one atmosphere, a relative humidity of 0 percent, and 23 ° C, and preferably less than 15 cubic centimeters / meter square, more preferably less than 10 cubic centimeters / square meter. The EVOH is prepared by the hydrolysis (or saponification) of an ethylene-vinyl acetate copolymer, and it is well known that to be an effective oxygen barrier, the hydrolysis-saponification must be almost complete, i.e. to the degree of at least 97 percent (whose use in the same way is preferred for the present invention). EVOH is commercially available as a resin with different percentages of ethylene, and there is a direct relationship between the ethylene content and the melting point. In the practice of this invention, the EVOH component of the core layer has a melting point of about 175 ° C or lower. This is characteristic of commercially available EVOH materials having an ethylene content of about 38 mole percent or higher. Suitable EVOHs having an ethylene content of 38 mole percent have a melting point of about 175 ° C. As the ethylene content increases, the melting point is lowered. A melting point of about 158 ° C corresponds to an ethylene content of 48 molar percent. The preferred EVOH materials will have an ethylene content of 44 mole percent. EVOH copolymers having higher ethylene contents can be used, and it is expected that processability and orientation would be facilitated, - however, gas permeabilities, particularly with respect to oxygen, can become undesirably high for certain applications of packaging that are sensitive to the degradation of the product in the presence of oxygen. The amount of EVOH in the core layer can be adjusted by mixing in nylon to vary the orientation parameters or the gas permeability, for example, to O2, of the films of the invention. The thickness of the core layer can also be varied from about 0.05 to about 0.30 thousandths (from 1.3 to 7.62 microns). Also, while it is preferred that the core layer consists essentially of EVOH, the present invention recognizes the possibility not only that up to 20 percent nylon is present, but also that other additives, including polymers, can be mixed into the layer of the core, to purposely affect the properties of the core layer, such as gas permeability or resistance to moisture in smaller quantities.

When the EVOH of the oxygen barrier layer is mixed with nylon, the preferred polyamide is nylon 6/66 in the mixture. Nylon 6/66 is a copolymer of nylon 6 and nylon 66. Nylon 6 is poly-epsilon-caprolactam. Nylon 66 is the polymer derived from adipic acid and hexamethylene diamine. Nylon 6/66 is manufactured by different companies, in some cases by different percentages of the two monomers, possibly by different methods, and presumably with different operating parameters. In accordance with the above, the properties of the different nylon 6/66 copolymers can be significantly different. For example, the melting temperature decreases as the nylon 66 content increases from 5 percent to 20 mole percent. When other nylons are used, such as type 6.12, such as the polyamide in the polymer mixture of the oxygen barrier layer, numerous gels of the core layer of the film of the coating layer are developed, and in some cases Cracks develop. The gels may be due to the incompatibility of the EVOH-nylon 6,12, or the chemical reaction between the two polymers. Cracks probably develop because the polymer mixture is not stretching evenly during orientation. These numerous gels and cracks are undesirable in films for commercial use for packaging food materials, and indicate potential weaknesses in the integrity of the film and in the permeability properties. A preferred nylon is a 6/66 nylon copolymer having a melting point of about 195 ° C, having a reported nylon component content of about 85 mole percent, and a content of nylon component 66 of about 15 mole percent, and which is commercially available from Allied Chemical Co. of Morristown, New Jersey, USA, under the registered trademark CAPRON XTRAF0RMMR 1539F. The core layer must be at least 80 weight percent EVOH, and optionally may contain 0 to 20 weight percent nylon. The use of higher amounts of nylon (eg, more than 10 percent, and particularly more than 20 percent) results in undesirably high oxygen permeability. The second and fourth layers are disposed on either side of the core layer, and provide good interlayer adhesion characteristics to the multilayer structure. Either or both of these layers may also contribute to the shrinkage and / or optical possibilities of the film of the invention. The composition of each of the second and fourth layers comprises at least 10 percent of a first copolymer of ethylene, and at least one α-olefin of 4 to 8 carbon atoms, this copolymer having a density of 0.900 to 0.915 grams. / cm3, and a melt index of less than 1.0 decigrams / minute or. This first copolymer is a very low density polyethylene. The expression polyethylene of very low density ("VLDPE") sometimes called ultra low density polyethylene ("ULDPE"), as used herein, refers to substantially linear polyethylenes having densities less than about 0.915 grams / cm 3, and possibly as low as 0.86. grams / cm3, and having at least a melting point of at least 90 ° C. This expression does not include ethylene-to-olefin copolymers of densities less than about 0.90 grams / cm 3, with elastomeric properties and referred to as elastomers. Some elastomers are also referred to by at least one manufacturer as "ethylene-to-olefin plastomer", but other manufacturers have characterized very low density polyethylene as an ethylene-to-olefin with plastomeric properties. However, as explained hereinafter, ethylene-α-olefin elastomers or plastomers may conveniently be used in the practice of this invention as a minor constituent in certain layers of this multilayer film. Very low density polyethylene does not include linear low density polyethylene (LLDPE), which have densities in the range of 0.915 to 0.930 grams / cm, but it is contemplated that optionally linear low density polyethylene can be mixed in one or more of the layers. Very low density polyethylene, as this term is used herein, can be made by a variety of processes, including solution or fluidized bed processes, using a variety of catalysts, including traditional Ziegler-Natta, geometry catalysts Limited of a single site, or of metallocene. Very low density polyethylene comprises copolymers (including terpolymers) of ethylene with α-olefins, usually 1-butene, 1-hexene, or 1-octene, and in some cases terpolymers, such as for example ethylene, 1-butene, and 1-hexene. A process for making very low density polyethylenes is described in European Patent Document Publication Number 120,503, the text and drawing of which are hereby incorporated by reference herein. As described, for example, in Ferguson et al., U.S. Patent Number 4,640,856, and in Lustig et al., U.S. Patent Number 4,863,769, very low density polyethylenes can be used in biaxially films. oriented, and have superior properties to comparably made films that have low density linear polyethylenes. These superior properties include higher shrinkage, higher tensile strength, and greater puncture resistance. Suitable very low density polyethylenes include those manufactured by Dow Chemical Company, Exxon Chemical Company, and Union Carbide Corporation. The composition of each of the second and fourth layers also comprises at least 10 percent of a second copolymer of ethylene with 4 to 18 percent of a vinyl ester or alkyl acrylate, and at least 10 percent of a third copolymer of ethylene with at least one α-olefin, a vinyl ester, or an alkyl acrylate modified with anhydride, and 0 to 30 percent of a fourth copolymer of ethylene and at least one α-olefin of 3 to 8 atoms carbon that has a density lower than 0.900 grams / cm3, and a melting point lower than 85 ° C. The second preferred copolymer is an ethylene-vinyl acetate copolymer. The term "ethylene-vinyl acetate copolymer" (EVA), as used herein, refers to a copolymer formed from ethylene and vinyl acetate monomers, wherein the units derived from ethylene (monomer units) in the copolymer they are present in larger amounts (by weight), and the units derived from vinyl acetate (monomer units) in the copolymer are present in minor amounts by weight. The composition of the second layer can be identical or different from that of the fourth layer, within the parameters of the structure defined above. For example, the first, second, and third specific polymers used may differ from one layer to the other, or may be partially or completely the same, or may be in the same or in different amounts. Also, the optional fourth polymer and other ingredients not required by this invention may also be present in one or both layers, and the relative thicknesses of each layer may vary. Beneficially, the second layer will often be thicker than the fourth layer, to provide good moisture barrier properties in addition to a good chance of shrinkage. The optional fourth component is often referred to as a "plastomer". The first copolymer of either or both of the second and fourth layers may comprise from 10 to 70 percent of each respective layer. The second copolymer of either or both of the second and fourth layers may comprise from 10 to 40 percent of each respective layer. The third copolymer of either or both of the second and fourth layers may comprise from 10 to 60 percent of each respective layer. The fourth copolymer of either or both of the second and fourth layers may comprise at least 10 percent of each respective layer. The fifth layer provides mechanical strength, possibility of shrinkage, resistance to abrasion, and resistance to burning during heat sealing. This fifth layer is typically thick enough to provide support, possibility of heat shrinkage, and impart resistance to the wall of the packing film in order to withstand shrinkage operation, handling pressures, abrasion, and packing with a food material. As an outer surface layer of the film, the fifth layer provides a desirable glossy appearance. Conveniently, the fifth layer comprises at least 30 percent, preferably at least 40 percent, of a first copolymer of ethylene with a minor proportion of one or more α-olefins of 4 to 8 carbon atoms, which It can provide a barrier to water vapor, which resists moisture permeation. High moisture barrier properties are desirable to avoid weight loss and undesirable drying of the enclosed food product. This first copolymer has a density of 0.900 grams / cm3 at 0.915 grams / cm3, and a melt index of less than 1.0 decigram / minute, and is often called a very low density polyethylene. The fifth layer further comprises at least 10 weight percent of a second ethylene copolymer with 4 to 18 percent (based on the weight of the second copolymer) of a vinyl ester or alkyl acrylate. Preferably, this second copolymer comprises EVA. Optionally, in this fifth layer is included 0 to 30 percent of a third ethylene copolymer and at least one α-olefin of 3 to 8 carbon atoms having a density less than 0.900 grams / cm, and a melting point lower than 85 ° C. This third copolymer is often called a "plastomer", and may also have an average molecular weight distribution (Mw / Mn) of less than 3, for example of about 2. Processing aids, such as slip agents, may also be incorporated. , anti blocking agents, and the like, in the fifth layer, as well as in other layers. These processing aids are typically used in amounts less than 10 percent, and preferably less than 5 percent of the weight of the layer. A preferred processing aid for use in the outer layer of the film is a fluoroelastomer. The above ingredients are mixed together, and extruded to provide a uniformly mixed layer having good strength, processability, high shrinkage characteristics, and good optimum properties, including high gloss. The addition of the third copolymer, in particular, contributes to good optical and shrinkage properties. Conveniently, the fifth layer may consist essentially of the first and second copolymers with or without the third copolymer, and with or without a minor amount (<10 percent) of processing aid. The multilayer film of the invention can be made by conventional processes, including, for example, slot casting or blown film processes, but preferably will be done by an orientation process, especially under conditions to produce a film that can be Shrink by heat at 90 ° C or less. For example, a packaged food material having a heat-shrinkable film enclosure according to the invention will conveniently adhere to the food material even after it is opened. Bags that do not have shrinkage have a tendency to fall off the sides of the enclosed product once the vacuum is broken either by intentional or accidental opening. Once the film is separated from the surface of the enclosed article, the oxygen comes into contact with the surface of the article, and product defects can occur in susceptible products such as ham. Some prior art films and bags are non-shrinkable bags that suffer from this defect, thereby causing spoilage and spoilage when used to pack perishable food materials. The fifth layer film of this invention can be manufactured by co-extrusion of all the layers simultaneously, for example, as described in U.S. Patent No. 4,448,792 (Schirmer), or by a coating lamination process, such as described in U.S. Patent No. 3,741,253 (Brax et al.) to form a relatively coarse primary multilayer extrudate, either as a flat sheet, or, preferably, as a tube. This sheet or tube is oriented by stretching at the orientation temperatures which are generally lower than the melting points for the predominant resin comprising each oriented layer. Stretching orientation can be performed by different known methods, for example, tensioning commonly used to orient sheets, or by the well-known technique of trapped bubble or double bubble to orient tubes, as for example described in the US Pat. United States of America Number 3,456,044 (Pahlke). In this bubble technique, an extruded primary tube exiting from a tubular extrusion die is cooled, collapsed, and then preferably oriented by reheating and inflation to form an expanded secondary bubble, which again cools and collapses. Preferred films are stretched biaxially. The orientation in the transverse direction (TD) is performed by the aforementioned inflation to radially expand the heated film, which is cooled to set the film in an expanded form. The orientation in the machine direction (MD) preferably is made with the use of sets of tightening rollers rotating at different speeds to stretch the film tube in the machine direction, thus causing an elongation in the direction of the machine, which is set by cooling. The orientation can be in either or both directions. Preferably, a primary tube is biaxially stretched simultaneously radially (transversally) and longitudinally (machine direction) to produce a multilayer film that is heat shrinkable at temperatures lower than the melting points of the main polymeric components , for example, at 90 ° C or less. Axially stretched films, especially biaxially stretched, which are "heat shrinkable", as that term is used herein, have at least an unrestricted shrinkage of 10 percent at 90 ° C (10 percent both in the direction of the machine (MD) as in the transverse direction (TD) for biaxially stretched films). In accordance with the present invention one or more of the five essential film layers can be oriented, either uniaxially or biaxially, by axial stretching at sufficiently low temperatures to produce high-shrink high-shrink multilayer films. These multi-layer heat-shrinkable films will have a shrinkage of at least 10 percent in at least one direction at 90 ° C, but preferably will have a shrinkage of at least 20 percent at 90 ° C in at least one direction (preferably in both directions), and conveniently can have at least a shrinkage of 30 percent at 90 ° C in at least one direction, and preferably can have at least 25 percent in both directions MD and T.D., and beneficially can have a shrinkage of at least 10 percent at 74 ° C in both directions M.D. and T.D., and preferably at least 15 percent (more preferably at least about 20 percent) in at least one direction at 74 ° C. The general tempering process by which shrinkable heat-biaxially stretched films are heated under controlled tension to reduce or eliminate shrinkage values is well known in the art. If desired, the films of the present invention are tempered to produce lower shrinkage values, as desired for the particular temperature. The stretch ratio during orientation should be sufficient to provide a film with a total thickness of between about 1.0 and 4.0 thousandths (from 25.4 to 101.6 microns). The stretch ratio in the machine direction is typically 2 ^ -6, and the stretch ratio in the transverse direction is also typically 2 ^ -6. A ratio of overall stretching (stretching in the machine direction multiplied by stretching in the transverse direction) of about 6 \ xx-36x is adequate. The preferred method for forming the multilayer film is the coextrusion of the primary tube, which is then biaxially oriented in a manner similar to that widely described in the aforementioned US Pat. No. 3,456,044, wherein the tube The primary leaving the die is inflated by the admission of a volume of air, cooled, collapsed, and then preferably oriented by reinflation, to form a secondary tube called a "bubble", with reheating to the temperature scale of orientation (stretching) of the film. The orientation in the machine direction (MD) is produced by pulling or stretching the film tube, for example, by using a pair of rollers running at different speeds, and in the orientation in the transverse direction (CD) obtained by radial bubble expansion. The oriented film is set by rapid cooling. In the following examples, the five layers were co-extruded as a primary tube that was cooled off the die by spraying with tap water. This primary tube was then reheated by radiant heaters, with further heating at the stretching temperature (also called the orientation temperature), for the biaxial orientation made by an air cushion, which itself was heated by transverse flow through the one tube for another heated concentrically placed around the primary tube in motion. The cooling was performed by means of a concentric air ring. In a preferred process for manufacturing the films of the present invention, the resins and any additives are introduced to an extruder (generally an extruder by layer), wherein the resins are melt-plasticized by heating, and then transferred to a die. extrusion (or coextrusion) to be formed in a tube. The temperatures of the extruder and the die will generally depend on the particular resin or the resin-containing mixtures that are being processed, and suitable temperature scales are generally known in the art. for commercially available resins, or are provided in the technical bulletins made available by resin manufacturers. Processing temperatures may vary depending on other process parameters selected. However, variations are expected, which may depend on factors such as variation of polymer resin selection, the use of other resins, etc., by mixing, or in separate layers in the multilayer film, of the manufacturing process used. and of the particular equipment, and of other process parameters used. Actual process parameters, including process temperatures, are expected to be established by an expert in this field, without undue experimentation in view of the present disclosure. As is generally recognized in the art, the properties of the resin can be further modified by mixing two or more resins with each other, and it is contemplated that different resins can be mixed in individual layers of the multilayer film, or that they can be added as additional layers, and these resins include ethylene-unsaturated ester, especially vinyl ester copolymers such as EVA, or other ester polymers, very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), nylons, ionomers, polypropylenes, or mixtures thereof. These resins and others can be mixed by well known methods, using commercially available tumblers or mixers. Also, if desired, well-known additives, such as processing aids, slip agents, blocking agents, pigments, etc., and mixtures thereof, may be incorporated into the film. In some preferred embodiments of the invention, it is preferred to crosslink the entire film to extend the range of heat sealing. This is preferably done by irradiating with an electron beam at dosage levels of at least about 2 megarads (MR), and preferably on the scale of 3 to 8 MR, although higher dosages may be employed. The irradiation can be done on the primary tube, or after the biaxial orientation. The latter, called posterior irradiation, is preferred, and is described in United States Patent Number 4,737,391 (Lustig et al.). An advantage of the subsequent irradiation is that a relatively thin film is treated in place of the relatively thick primary tube, thereby reducing the energy requirement for a given treatment level. Alternatively, the crosslinking can be achieved by the addition of a chemical crosslinking agent, or by the use of irradiation in combination with a crosslinking enhancer added to one or more of the layers, as for example described in the US Pat. United States of America Number 4,055,328 (Evert et al.). The most commonly used crosslinking improvers are organic peroxides, such as trimethylpropane and trimethylacrylate. These performance levels are desirable to shrink food materials, such as beef, chicken breasts, and ham, which are susceptible to discoloration and decomposition in the presence of oxygen. The following are examples and comparative examples given to illustrate the present invention. The experimental results and reported properties of the following examples are based on the following test methods, or on substantially similar test methods, unless noted otherwise.

Tensile strength: ASTM D-882, Method A. Elongation percentage: ASTM D-882, Method A. Nebulosity: ASTM D-1003-52 Brightness: ASTM D-2457, 45 ° angle.

Percent drying module: ASTM D-882, Method A. Oxygen gas transmission speed (02GTR): ASTM D-3985-81 Water vapor transmission rate (VTR): ASTM F 1249-90 Resistance to Elmendorf tear: ASTM D-1992 Caliber: ASTM D-2103 melt index: ASTM D-1238, Condition E (190 ° C) (with the exception of propene-based polymers) C3 content of > 50%) tested in Condition L (230 ° C)). Melting point: ASTM D-3418, differential scanning calorimetry with heating rate of 5 ° C / minute. Surface energy (wetting tension): ASTM D-2578-84.

Shrinkage values: Shrinkage values are defined as the values obtained by measuring the unrestricted shrinkage of a square 10-cm sample immersed in water at 90 ° C (or at the indicated temperature if different) for 5 seconds. Four test samples are cut from a given sample of the film to be tested. Samples are cut into 10-centimeter-long squares in the machine direction by 10 centimeters in length in the transverse direction. Each sample is completely immersed for 5 seconds in a water bath at 90 ° C (or at the indicated temperature if different). The sample is then removed from the bath, and the distance between the ends of the sample shrunk for both the machine direction and the transverse direction is measured. The difference in the distance measured for the shrunken sample and the original 10 cm side, multiply by 10, to obtain the percentage of shrinkage for the sample in each direction. The shrinkage of four samples is averaged for the shrinkage value in the machine direction of the given film sample, and shrinkage is averaged for the four samples for the shrinkage value in the transverse direction. As used herein, the term "heat-shrinkable film at 90 ° C" means a film having an unrestricted shrinkage value of at least 10 percent in at least one direction.

Shrinkage Strength: The shrinkage force of a film is the force or tension required to prevent shrinkage of the film, and was determined from film samples taken from each film. Four film samples were cut 1 inch (2.54 centimeters) wide by 7 inches (17.8 centimeters) long in the machine direction, and 1 inch (2.54 centimeters) wide by 7 inches (17.8 centimeters) long in the transversal. The average thickness of the film samples was determined and recorded. Then each film sample was secured between two separate fasteners at 10 centimeters. One fastener is in a fixed position, and the other is connected with a voltage measuring transducer. The secured film sample and the fasteners were then immersed in a bath of silicone oil held at a constant elevated temperature for a period of 5 seconds. During this time, the force in grams at the elevated temperature was recorded. At the end of this time, the film sample was removed from the bath, and allowed to cool to room temperature, on which, the force in grams at room temperature was also recorded. Then, the shrink force for the film sample was determined from the following equation, where the results are obtained in grams per thousandth (25.4 centimeters) of film thickness (grams / 25.4 microns): Shrinkage Strength (g / 25.4 microns) = F / T where F is the force in grams, and T is the average thickness of the film samples in thousandths (microns).

Impulse Seal Range: The impulse seal range test determines the acceptable voltage ranges for impulse sealing plastic films. A Sentinel Model 12-12AS laboratory sealer manufactured by Packaging Industries Group, Inc., Hyannis Massachusetts, E.U.A. This impulse sealer is equipped with a replacement sealing strip for a Multivac AG100 packaging machine. The ribbon is available at Koch Supplies of Kansas City, Missouri. In this test, two samples of 4 inches (10.16 centimeters) wide (in the transverse direction) are cut from a tubular film. The impulse sealer is equipped with controls for coolant flow, impulse voltage, and time, and pressure of the seal bar. These controls, with the exception of impulse voltage, are established under the following conditions: impulse time of 0.5 seconds (upper bar only). Cooling time of 2.2 seconds. Jaw pressure of 50 psi (345 kPa). Coolant water flow (approximately 75 ° F (22 ° C)) of 0.3 gallons per minute (1 liter per minute).

One of the samples is folded in half for use in determining a minimum sealing voltage. This fold simulates the fold that can occur inadvertently during conventional bag sealing operations. The bent sample now has four sheets or portions of film (hereinafter referred to as "sheet portions"), and is placed in the sealant, and by trial and error, the minimum voltage is determined to seal the two portions of sheet inferior with each other. Then the maximum voltage is determined for a sample that has two portions of sheet, placing it in the sealant, and then activating the seal bar. The film sample is manually pulled with a force of approximately 226.8 grams, and the voltage that causes no burn or significant distortion of the seal is determined.

Seal Resistance Test: Cut five identical samples of film 1 inch (2.54 centimeters) wide, and at least 5 inches (77 centimeters) long, with a 1 inch (2.54 centimeters) wide seal portion centrally and transversely arranged. Opposite end portions of a film sample are secured in opposite fasteners, in a temperature controlled chamber of an Instron 4501 Universal Testing Instrument. The film is secured in a comfortable taut fit between the fasteners without stretching before starting the test. The door of the test chamber is closed, and the chamber is heated up to the test temperature, at which time the instrument is activated to pull the film by means of the fasteners, transverse to the seal, at a uniform speed of 5 inches ( 127 centimeters) per minute, until the film breaks (breaking of the film or stamp, or delamination and loss of film integrity). Grams are measured and recorded at break. The test is repeated for five samples, and the average grams are reported at break. Unless stated otherwise, the impulse seals tested by the seal resistor were made using the equipment described in the test description of the previous impulse seal range, with the controls similarly established, but with a time of cooling of approximately 8 seconds. The hot bar seals and different tested films were made similar to each other, using the conditions of 500 ° F (60 ° C), and residence time of 0.5 seconds.

Seal Drag: The Seal Drag Test until the Break is designed to be an accelerated cooking drill to determine the seal breaking strength and / or the loss of integrity of the film, from a processing film through weather. In the test, five film samples of% inch (12.7 millimeters) wide are cut from one or more similar sealed films, the cuts being made perpendicular to the seal, such that each film sample contains a seal of 3. inch (12.7 millimeters) wide, and 5 inches (12.7 centimeters) of film on either side of the seal This produces samples that are each 10 inches (25.4 centimeters) long by% inch (12.7 millimeters) wide, with a seal in half The opposite upper and lower long portions of a film sample containing a centrally disposed seal securely join the respective flat plate fasteners which extend over the width of the end of the film. Upper film is attached to an attachment, while the opposite lower fastener has a joined weight (for a total weight of approximately 1 pound (454 grams)). The heavy fastener and the lower film portion that includes the seal area, are submerge in a controlled temperature water circulation bath set at 165 ° F (74 ° C) .The seal area of the film is placed approximately 5.08-7.62 centimeters below the surface of water, and the film strip with the attached weight is perpendicular to the surface of the water. When submerging, a stopwatch is started, and the film and the weight are observed, and the time in which the weight falls is recorded, meaning the rupture of the seal of the film and / or the loss of the integrity of the film. Film and weight are continuously observed during the first 15 minutes, and then verified at least every 15 minutes thereafter, up to a total test period of 180 minutes. The average is reported for five test samples. You can also report the minimum and maximum values measured for the set. Below are the examples and comparative examples given to illustrate the invention. In all of the following examples, unless otherwise indicated, the film compositions were generally produced using the apparatus and method described in U.S. Patent No. 3,456,044 (Pahlke), which describes a method of double bubble of coextrusion type, and in addition in accordance with the detailed description above. All percentages are by weight, unless otherwise indicated.

Examples 1-6 In Examples 1-3, three biaxially stretched, heat shrinkable multilayer films of the present invention were made. The layers of each multilayer film were coextruded and biaxially stretched according to a tubular orientation process of the coextrusion type. Examples 1-3 are five layer films. However, the present invention also contemplates films of six or more layers. The multilayer films of the invention may include additional layers or polymers to add or modify different properties of the desired film, such as the possibility of sealing by heat, the adhesion between layers, the superficial adhesion to the food, the possibility of shrinkage, the force of shrinkage, the resistance to wrinkles, the resistance to perforation, the possibility of printing, the hardness , gas or water barrier properties, abrasion resistance, and optical properties such as brightness, haze, that is free of lines, streaks, or gels. These layers can be formed by any suitable method, including coextrusion, extrusion coating, and lamination. For Examples 1-3, an extruder was used for each layer, and the heat-plasticized resins from each extruder were placed in a 5-layer spiral plate coextrusion die, from which the resins were coextruded in a proportion of first / second thickness / -third / fourth / fifth layers of approximately 16: 43: 11: 9: 21 for Examples 1-3. In Examples 1-3, for each layer, the resin or resin mixture was fed from a hopper to a single screw extruder attached, where the resin and / or the mixture was heat-laminating, and extruded through of a five layer coextrusion spiral plate die in a primary tube. Barrel temperatures of the extruder for the third layer (core), were approximately 350 ° F to 400 ° F (from 177 ° C to 204 ° C), - for the first (internal) and second (intermediate) layers was of approximately 300 ° F (149 ° C); for the fourth (intermediate) layer it was approximately 340 ° F (171 ° C), and for the fifth (external) layer it was approximately 300 ° F-340 ° F (166 ° C to 171 ° C). The extrusion die had an annular exit opening with a diameter of 7.62 centimeters, with a gap of 1524 millimeters (7.62 centimeters x 0.152 centimeters). The temperature profile of the coextrusion die was set from approximately 340 ° F to 410 ° F (from 171 ° C to 210 ° C). The extruded multilayer primary tube was cooled by spraying with cold tap water (from about 7 ° C to 14 ° C). The cooled primary tube was flattened by passing it through a pair of clamping rollers, whose speed was controlled to make a neck in the primary tube to adjust the circumference of the tube or the flat width. In Examples -1 to 3, a flat tube of approximately 4% (10.5 centimeters) flat width was produced. The cooled, flattened primary tube was reheated, biaxially stretched, and cooled. The cooled film was flattened, and the biaxially stretched and biaxially oriented film was wound onto a spool. The ratio of stretching or orientation in the machine direction (MD) was from about 3.7: 1 to 3.8: 1, and the proportion of bubble or orientation in the transverse direction (TD) was about 2.8: 1 to 2.9 : 1 for all movies. The stretch point or the orientation temperature was below the predominant melting point for each oriented layer, and above the glass transition point of this layer. Stretch point temperature, bubble heating and cooling rates, and orientation ratios are generally adjusted to maximize bubble stability and production for the desired amount of stretch or orientation. The resulting films of Examples 1 to 3, which have an average caliber of 2.5 to 2.7 thousandths (64.3 to 70.4 microns) (see Table 2) were oriented biaxially, and had an excellent appearance. Examples 4 and 5 were made by irradiation at a 4 Mrad level, by electron beam after orientation, and in accordance with methods well known in the art to cause crosslinking, especially of the second and fourth adhesive layers. polymeric, and the outer polymeric layer (guinta). These Examples (4 and 5) are also treated with corona, to make the first layer have adhesion to proteinaceous food materials such as meat. This property, called "meat adhesion" is important for applications where it is desirable to retain the juices inside the meat during cooking or pasteurization while in the bag. This is called preventing "outward cooking," where pockets of fat and juices can form, causing an undesirable appearance, loss of juices, and weight loss. In other applications (often referred to as "cooking and separation"), it is desirable to be able to easily remove the bag from a product following cooking or pasteurization; and in these applications, the film is not treated with a crown, and the inner layer conveniently does not adhere to the enclosed food material, e.g., meat. In these applications, a worker can easily remove the bag after processing, for further processing, repackaging for retail sale, or for use. For all Examples 1 to 3 (the first layer which was the inner surface of the tubular film) comprised a random copolymer of propene and ethene, with a melting point of differential scanning calorimetry of 133 ° C, a reported density of 0.895 grams / cm3, a melt index of 5 grams / 10 minutes, and which is commercially available under the registered trademark Eltex P KS 409 from Solvay & Cié de Bruselas, Belgium. In Examples 1, 2, and 3, the first layer comprised respectively, 100 percent, 90 percent, and 80 percent by weight of the propene-ethene random copolymer, and 0 percent, 10 percent, and 20 percent by weight of a polyethylene-based adhesive linear low density. The adhesive based on linear low density polyethylene was a bonding layer resin based on linear polyethylene of low density extrudable, modified with rubber, and modified with anhydride, which had the following properties reported: density of 0.912 grams / cm3, index of fusion of 1.5 decigram / minute, a Vicat softening point of 98 ° C, a melting point of about 125 ° C, and is available under the registered trademark Plexar® PX380 from Quantum Chemical Corporation, Cincinnati, Ohio, USA The fifth layer of Examples 1-3 (which was the outer surface of the tube) contained a very low density polyethylene ethylene-α-olefin copolymer sold by Dow Chemical Company of Midland, Michigan, USA, under the registered trademark Attane XU 61509.32, which is a copolymer of ethylene and octene-1, which reportedly has a melt index of approximately 0.5 decigrams / minute, and a density of approximately 0.912 grams / cm3, with a Vicat softening point of 95 ° C, and a melting point of about 122 ° C. Also, in the fifth layer was a copolymer of ethylene and vinyl acetate (EVA) as a component of the resin mixture. This EVA is available from Exxon Chemical Company of Houston, Texas, E.U.A., under the registered trademark Escorene LD 701.06, and has the following reported properties: a content of 10.5 percent vinyl acetate; density of 0.93 grams / cm3, - melting index of 0.19 decigrams / minute, - and a melting point of approximately 97 ° C. In Examples 1, 2, and 3, the compositions of the fifth (outer) layer were identical, and comprised 70.6 percent of the ethylene-α-olefin copolymer that was mixed with 25 percent of the EVA copolymer and 4.4 percent by weight of a skid processing aid sold under the registered trademark Ampacet 100031 by Ampacet Corp. of Tarrytown, New York, USA For Examples 1-3, the second and fourth layers (intermediate), were each identical mixtures that comprised 17.5 percent of the same EVA copolymer used in the fifth layer, with 42.5 percent of the same very low density polyethylene used in the fifth layer, and 40 percent of the same bonding layer adhesive resin based on linear extrudable low density polyethylene, modified with rubber, and modified with anhydride (PlexarR PX380) used in the first layer. The second and fifth layers of each of Examples 1 to 3 were identical to one another, with the exception that the fourth layers of Examples 1 to 3 were all thinner than the corresponding second layers. For Examples 1 to 3, each core layer comprised a mixture of 90:10 weight percent of a saponified ethylene-vinyl acetate copolymer (EVOH) with a nylon. A premix was formed by mixing 90 percent EVOH with 10 percent nylon. This premix was then added to an extruder hopper for extrusion as the core layer. EVOH was a commercially available copolymer sold by Eval Company of America of Lisie, Illinois, USA, under the registered trademark EVAL E105A, and had the following reported properties: an ethylene content of 44 weight percent, a melt index of 5.5 decigrams / minute, a density of 1.14, and a melting point of 165 ° C. The nylon was a commercially available nylon 6/66 copolymer sold by Allied Chemical Company under the registered trademark CAPRON XTRAFORM 1539F, and had a reported nylon content of 85 mole percent, and a nylon 66 content of 15 percent. molar, with a differential scanning calorimetry melting point of approximately 195 ° C, and a density of 1.13 grams / cm3. The comparative example 6 is not of the invention, but is an example of the prior art of a commercial film used for packaging cooked inside, for example, hams. The comparative film of Example 6 is believed to be a six layer film of the 3 carbon atom / α-olefin / adhesive / EVOH (44 molar percent ethylene) / adhesive / EVA copolymer structure. All the examples, including the comparative example, can be shrunk by heat at 90 ° C. It is believed that Example 6 has a composition and layer thicknesses of about 12.7 microns for the first layer (copolymer C3), - 15.24 microns for the second layer (EVA) and third layer (adhesive) combined; 5.08 microns for the fourth layer (EVOH); and 30.48 microns for the fifth (adhesive) and sixth (EVA) combined layers. The layer formulations of Examples 1 to 5 are reported in Table 1. The physical properties of the films of Examples 1 to 6 were measured and reported in Tables 2 to 4.

TABLE 1 Composition of the layers The adhesive is a linear modified low density polyethylene adhesive modified with anhydride and modified with rubber (Plexar PX 380).

TABLE 2 ND = NOT DETERMINED. TA = AMBIENT TEMPERATURE (approximately 20-23 ° C).

TABLE 3 ND = Not determined. TA = Ambient temperature (approximately 20-23 ° C) HR = Relative humidity. Transmission rate of oxygen gas (0GTR) in units of cm 3 t = x m2 x 24 hours at one atmosphere for the film tested.

* = For 02GTR the thickness of the film is below the speed in microns (μ.). ** - Average of 5 values; a sixth value greater than 120 seconds was also obtained for a film of 89 microns TABLE 4 ND = Not determined. TA = Ambient temperature (approximately 20-23 ° C). * = This was a factory seal, and the sealing method was not determined.

The results of Table 2 show that the films according to the present invention have good physical properties. Elongation to breakage, tensile strength, shrinkage without restrictions, and shrink force properties of Examples 1 to 5 of the invention, are comparable to commercially available films for packing cooked foods indoors, as exemplified by comparative example 6. Aungue Comparative Example 6 has slightly better shrinkage values than the films of Examples 1 to 5, all films of The invention has shrinkage values without suitable restrictions and excellent for many utilities, including packing of food materials. The values of elongation at break and tensile strength of Examples 4 and 5 are generally as good or better than those reported for the comparative film of Example 6. For packing articles, the reported elongation values at breaking for the films of Example of the invention, has very good extensibility, which is suitable to accommodate any stretch found under the typical conditions of empague and process. The shrinkage values for Examples 1 to 5 are good for a film containing EVOH. The values in the transverse direction are all greater than 30 percent at 90 ° C, and those in shrinkage at temperatures lower than 74 ° C are similar to the values of shrinkage at 74 ° C for the comparative example 6. The present invention can produce films with even higher shrink values in both directions at the test temperatures. Accordingly, the films of the invention may have desirably high shrinkage values, which may be greater than 20 percent in either or both directions at 90 ° C, and may beneficially be greater than 30 percent. High shrinkage, especially at 90 ° C or less, is an advantage when packing items to provide close contact between the film and the surface of the enclosed article, which prevents or minimizes the damage that can be caused by contact with oxygen or by the movement of the item in the pagúete. A further advantage is that good shrinkage values can be obtained at a lower temperature, thus utilizing a shrinkage process having lower energy regurgitations. Also, the shrinkage forces reported for Examples 1 to 5, especially the residual shrinkage forces, are at desirable levels to keep the film in close contact with the enclosed article, not only during possible processing subsequent to packing, for example, pasteurization, but also at room temperature. The strength of residual shrinkage at room temperature is important, for example, when a payment can be opened by exposing one end to the detrimental effects of exposure to the environment. Films and bags having a high residual shrinkage force, such as the values reported for Examples 1 to 5 of the invention, have a continuous closed contact between the film and the article, even after opening. The measured values of Examples 1 to 5 indicate that the film would remain in close contact with an enclosed article, and continue to maintain its protective functions. Referring now to Table 3, the films of the invention of Examples 4 and 5 demonstrate lower modulus values, indicating a smoother film, and yet having a tear strength superior to the commercially tested comparative film sample. available, and similar drilling resistance values. The oxygen barrier properties of the test films are all excellent for applications that would provide a low permeability (a high barrier) to oxygen. The optical properties of Examples 1 to 5 show that the films of the invention of Examples 1 and 4, which have a first unmixed layer consisting essentially of a propene copolymer, have a low nebulosity and a high glossiness in comparison with the mixed structures of Examples 2, 3, and 5. The comparative example 6 is also believed to have a first layer not mixed; however, the comparative example has a much more nebulous appearance and less glossy than the examples of the invention which have a first unmixed layer. Referring now to Table 4, the film samples of Examples 4 and 5 were corona treated, where Examples 1 to 3 were not corona treated. The difference in surface energy or wetting tension is shown by the values of dynes per centimeter. The surface energy values obtained for the films of Examples 1 and 3 indicate films suitable for cooking and separation applications, or films to be used where adhesion to the meat is not a desired or desired property. The surface energy value for comparative example 6 suggests that this film has been treated with corona. The range of the impulse seal for Examples 4 to 5 crosslinked by irradiation is sufficiently broad to be used in sealing by a commercially available sealing sealant, including hot or impulse bar sealers. The seal-to-rupture and seal-resistance data show a film having strong seals and a high resistance to superior delamination in relation to the film of the comparative example.

The first seal resistance data set demonstrates that the impulse seals of the films of the invention can be made over a range of voltages from 40 to 49 volts, which are unexpectedly higher than elevated temperatures to the prior art film of the invention. comparative example 6. The second seal resistance data set examines hot rod seals made at 500 ° F (260 ° C) and with a residence time of 0.5 seconds relative to the factory seal of the commercially available bag of Example 6. Again, the films of the invention exhibit an unexpectedly high and superior seal strength. Surprisingly, the seal drag test until the breakage demonstrates the dramatic superiority of the hot bar seals of the films of the present invention, to the factory seal of the comparative example, at a typical cooking temperature of 165 ° in. F (74 ° C). The unexpectedly good seal strength, particularly under simulated cooking conditions and temperatures, is believed to be due to the particular formulation-structure combination of the invention employed in the multilayer film. The films of Examples 4 and 5 were bagged to process and pack cooked food indoors. These bags, together with the bags of comparative example 6, were stuffed with ground meat, and baked at 165 ° F (74 ° C) in steam heat for 8 hours, followed by cooling overnight. All the characteristics of adhesion to the meat, purge control, resistance to delamination, and seal resistance of the films were evaluated. The films of Examples 4 and 5 were as good or better than the comparative example in all of the above characteristics, and demonstrated good purge control, high delamination resistance, good adhesion to the meat, and good water resistance. seal. None of the tested films of Examples 4 and 5 were delaminated during thermal processing or after removal of the film of the cooked product indoors. None of the films of Examples 4 and 5 exhibited seal failure during the 8 hour cooking period or after cooling overnight. The bags of Examples 4 and 5 were also subjected to a more severe cooking and baking method at a temperature of 180 ° F (82 ° C) in steam heat for 8 hours, to further test the seals by heat, and none of these bags showed seal failure. 1i! 1tmF? - '7-19 A five layer tubular film designated herein as Example 7 was made by a biaxial stretching orientation process. This process was similar to that described above for making the films of Examples 1 to 3, except as noted below. Example 8 is the film of Example 7 which has been irradiated by an electron beam to a level of about 4 Mrad. Example 9 is the irradiated film of Example 8 which has also been corona treated. Example 10 is a comparative example (not of the invention) which is described further below. These examples demonstrate the effect of certain properties of irradiation and corona treatment to, respectively, crosslink and surface treat (incorporate polar groups in) the movie. It also demonstrates the use of a core layer which consists essentially of EVOH, and the use of a sealer layer using a higher melting point propene copolymer. In all of the following examples, a 100 percent by weight core layer of EVOH (EVAL E105A), which had an ethylene content of 44 mole percent, was used. The films of Examples 7 to 9 each had an internal heat sealable layer comprising 100 percent by weight of a propylene-ethylene copolymer sold by FINA Oil and Chemical Company of Dallas., Texas, USA, under the registered trademark FINA 7371. This C3C2 copolymer reportedly had a melting point of approximately 143 ° C (measured by differential scanning calorimetry (DSC)), and a reported melting rate of 3.5 grams / 10 minutes (at 230 ° C / 2.16 Kg). This resin also had a reported density (p) of 0.9 grams / cm3. Barrel temperatures of the extruder for the third layer (core), were approximately 355 ° F to 365 ° F (179 ° C to 185 ° C); for the first (internal) and fourth (intermediate) layers, it was approximately 350 ° F to 375 ° F (from 177 ° C to 191 ° C); for the second (intermediate) layer it was approximately 320 ° F (160 ° C), and for the outer (outer) layer it was approximately 340 ° F (171 ° F). The temperature profile of the coextrusion die was set from approximately 350 ° F to 365 ° F (from 177 ° C to 185 ° C). For Examples 7 to 9, the second and fourth (intermediate) layers were each identical blends comprising 17 percent of the same EVA copolymer with 53 percent of the same very low density polyethylene used in Example 1, and 30 percent of a bonding layer adhesive resin based on linear anhydride-modified, low density polyethylene (Plexar® PX 360), with a melt index of 2 grams / minute, a density of 0.925 grams / cm3, and a melting point of approximately 125 ° C. The clear coat of Examples 7 to 9 (which was the outer surface of the tube) contained 73.1 weight percent of a very low density polyethylene ethylene-c-olefin copolymer sold by the Dow Chemical Company of Midland, Michigan, USA, under the registered trademark Attane XU 61509.32, which is an ethylene-octene copolymer which reportedly has a melt index of approximately 0.5 decigrams / minute, and a density of approximately 0.912 grams / cm3, with a softening point Vicat of 95 ° C, and a melting point of approximately 122 ° C. Also 22.5 weight percent EVA (LD 701.06) and 4.4 weight percent of the fluoroelastomeric skimming processing aid described in Example 1 were mixed in the same layer as in Examples 1 to 5, the first ( internal) and guinta (external) layers were connected to the opposite sides of a third layer (core) (comprising EVOH), by the second and fourth (intermediate) layers, which act in part as adhesive layers. The EVOH core layer controlled the permeability of the film with respect to gases such as oxygen. The films of the invention of Examples 7 to 9 have a five-layer structure which, if one refers to the Plexar resin containing layers such as the Adhesive layers (Ad), can generally be identified as 100 percent C3C2. / Ad / 100 percent EVOH / Ad / 73.1 percent EVA: 22.5 percent very low density polyethylene: 4.4 percent processing aid. The 100 percent layer of C3C2 is the inner layer of the tubular film. This film has relative layer thicknesses (from the first to the next layers) of 8.3 percent / 63.7 percent / 8.4 percent / 3 percent / 16.6 percent (the fourth and fourth combined layers were measured at 19.6 percent, and it is believed that the fourth layer is about 3 percent). For Example 10, the layers and their composition were identical to those of Example 7, with the exception that a very low ethylene-α-olefin polyethylene with a higher melt index was used for 0.5 M.I. VLDPE (XU61509.32). The components were described more fully in the foregoing with respect to Examples 3 and 7. The very low density polyethylene (XU61520.02) used in the first, second, and fourth layers of Example 10, was an ethylene-copolymer. octene-1, which had a reported density of 0.912 grams / cm3, a melt index of 1.0 decigrams / minute, and a melting point of approximately 123 ° C, which was available from the Dow Chemical Company under the registered trademark ATTANE XU 61520.01. The film of Example 10 was extruded very poorly, and could not be formed into a tubular film. The absence in the formulation of at least 10 percent of the ethylene copolymer and at least one α-olefin of 4 to 8 carbon atoms with a melt index of less than 1.0 decigram / minute, and a density of 0.900 to 0.915 grams / cm3, produced an unstable primary tube which had poor dimensional stability and low melt strength, which was insufficient to make a biaxially stretched tubular film. A movie could not be made, and consequently, no results are reported. Different properties of the films of Examples 7 to 9 were measured, and reported in the following Tables 5 and 6.

TABLE 5 ND = Not determined. TA = Ambient temperature (approximately 20-23 ° C). t = Rate of transmission of oxygen gas (0 GTR) in units of cm x square meter x 24 hours at one atmosphere, and relative humidity of 0 percent for the film tested. The film thickness of 0 GTR is mentioned below the speed in my ras (/ i).

TABLE 6 Referring to Tables 5 and 6, good physical properties are shown. Strong oxygen barrier films were made which had excellent optical properties. Values of very low cloudiness and high brightness are demonstrated. The surface energy values reflect that the film of Example 9 has been corona treated to provide a surface capable of high adhesion to the meat. The range of the impulse seal is peculiarly high and is outside the test scale, and it is believed that this is due to a combination of sealing through a relatively thick film (ie, a film of more than 2.6 thousandths (66 microns)), coupled with the use of a high melting point propene copolymer to form the first layer (sealer). Good shrinkage values are demonstrated both at 90 ° C and 74 ° C, with good values of shrinkage force both at high temperature and at room temperature. The hot bar seals were made from the irradiated films of Examples 8 and 9, and again demonstrate unexpectedly strong seals over a wide range of elevated temperatures. g-i «*" "11-16 Five-layer tubular films designated here as Examples 11, 12, and 14-16 were made by a biaxial stretching orientation process. This process was generally similar to that described above for making the films of Examples 1 to 3, except as noted below. The layer formulations of the film examples are mentioned in Table 7. The resins used in these examples were the same as those used in Examples 1 to 3, with the exception that the second, fourth, and second layers all included a resin designated in Table 7 as "Plastomer". This plastomeric resin was a copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms, with a density of less than 0.900 grams / cm 3, and a melting point of less than 85 ° C. In particular, the plastomeric resin used was a commercially available copolymer predominantly of ethylene copolymer with butene-1 monomer, and a component having a reported density of about 0.885 grams / cm 3, a melt index of 0.5 decigram / minute, and a melting point of 68 ° C, and available under the registered trademark Tafmer A0585X from Mitsui Petrochemical Industries, Ltd. of Tokyo, Japan. Examples 11 and 12 were similarly made films, which were processed to slightly different widths. Both films were irradiated by electron beam to a level of approximately 4 Mrad, and no film was corona treated. Examples 14-16 were irradiated to different levels of 4 Mrad, 5 Mrad, and 6 Mrad, respectively. The films of Examples 14-16 were all corona treated. Example 13 is a comparative example (not of the invention) which is described further below. These examples demonstrate the effect of the addition of the optional plastomeric component to the film, as well as the effect on certain properties of irradiation and corona treatment for, respectively, crosslinking and surface treating (incorporating polar groups in) the film. It also demonstrates the use of a core layer consisting essentially of EVOH, and the use of a sealant layer using a preferred low melting point propene copolymer. In all of the following examples, a 100 percent by weight core layer of EVOH, with an ethylene content of 44 mole percent, was used.

As in Examples 1 to 5, the first (internal) and guinta (external) layers were connected to the opposite sides of a third layer (core) (comprising EVOH), by the second and fourth (intermediate) layers, which act in part as adhesive layers. The EVOH core layer controlled the permeability of the film with respect to gases such as oxygen. The films of the invention of Examples 11, 12, and 14-16 each have a five-layer structure, with the 100 percent layer of C3C2 being the inner layer of the tubular film. These films have relative layer thicknesses (from the first to the next layers) of 11.8 percent, 43.1 percent, 7.3 percent, 3 percent, 34.8 percent (the fourth and fourth combined layers were measured at 37.8 percent , and it is believed that the fourth layer is approximately 3 percent). Example 13 is a comparative example of the prior art, a commercially available film which is believed to have a six layer structure as described above for comparative example 6, with the exception that comparative example 13 is not corona treated . Different properties of the films of Examples 11-16 were measured, and reported in the following Tables 8, 9, and 10.

TABLE 7 Coaposition of the Layers It is believed that the comparative example was irradiated, but not treated with corona. The adhesive is a linear modified low density polyethylene adhesive modified with anhydride and modified with rubber (Plexar PX 380). The outer layer for Examples 11 to 17, with the exception of comparative example 13, which is believed to be a six layer film, with the sixth layer as the outer layer.

TABLE 8 ND = Not determined. TA = Ambient temperature (approximately 20-23 ° C).

TABLE 9 ND Not determined. TA Ambient temperature (approximately 20-23 ° C). HR Relative humidity. t Oxygen gas transmission rate (02GTR) in units of cm x square meter x 24 hours at one atmosphere for the film tested.

For 02GTR, the thickness of the film is below the speed in my flush (/ - Values for the film coated with powder (the values for Example 13 after dusting were 11 and 65), respectively. of three values, other three values obtained were greater than 120 seconds for the film that had an average thickness of 80 TABLE 10 ND = Not determined. TA = Ambient temperature (approximately 20-23 ° C). * The seal tested was a factory seal, and the factory seal method was not determined.

Referring now to Tables 8, 9, and 10, the films of Examples 11-12 and 14-16 have very good physical properties, typically as good or better than those measured for Comparative Example 13. The comparison film had values of shrinkage slightly higher, but these values for all films were acceptable for commercial applications. Surprisingly, in connection with Comparative Example of commercial film 13, the films of the invention all demonstrate a much improved tear strength, and a better appearance, including lower nebulosity, higher brightness, and have better resistance to perforations by hot water. All films demonstrate adequate oxygen barrier properties. The surface energy measurements indicate adequate values for a high adhesion to the meat for Examples 14-16, and that Comparative Example 13 was not corona treated. This Comparative Example and the Examples not treated with corona 11-12 are suitable for use in applications without adhesion, such as in cooking and separation process applications. The films of Examples 14-16 had all similar broad planes of approximately 240 millimeters. The pulse seal ranges of the films of the invention 14-16 were measured, and it was determined that they are desirably large and sufficient for commercial heat sealing operations. Also, the maximum voltage for the impulse seals was measured using a residence time of one second for the films of Examples 14-16. The results indicate that the higher irradiation levels raise the maximum resistance to the burn of the film of the invention. For a comparison, the maximum impulse seal voltage was measured with a residence time of 1 second for the film of Comparative Example 6, and a maximum value of 39 volts was obtained. The seal resistances of hot bar seals made at 260 ° C with a residence time of 0.5 seconds for the films of the invention of Examples 11 and 12, are unexpectedly superior to the factory seals of the commercially suitable comparative film In addition, the seal resistances of the impulse seals of Examples 14-16 are surprisingly and unexpectedly superior to those measured for the six layer film of Example 6.

Example 17-23 Tubular films of 5 layers designated herein as Examples 17-22 were made by a biaxial stretching orientation process. This process was generally similar to that described above for making the films of Example 1-3. Layer formulations of the Film Examples are mentioned in Table 11. In Examples 17-19, the resins used in layers 2-5 were the same as those used in Examples 1-3, with the exception that the second, fourth, and fifth layers all included a resin designated in Table 11 as "Plastomer." The plastomer resin used in this set of examples was a copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms with a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85 ° C. . In particular, the plastomeric resin used was a commercially available copolymer predominantly of ethylene with a minor proportion of butene-1. This plastomeric copolymer has a reported density of about 0.888 grams / cubic centimeter, a melt index of 0.8 decigram / minute, and a melting point of 68 ° C. It is also believed that the plastomer has a narrow molecular weight distribution (N ^ / MJJ) of about 2, and was available from Exxon Chemical Company of Houston, Texas, USA, under the registered trademark Exact 9036. Examples 17-19 they were similarly made films, with the same formulations and structures, with the exception that the composition of the first layer was varied. In Example 17, the first layer (inner surface layer of the tube) was made 100 percent by weight of a propylene terpolymer. This C3C2C4 terpolymer was commercially available from Sumitomo Chemical Company, Limited of Tokyo, Japan, under the registered trademark Excellen WS 709N, and reportedly had minor proportions of ethylene (1.5 percent) and butene-1 (14.7 percent); a melt index of 8 decigrams / minute (230 ° C / 2.16 kg); and a melting point of about 133-134 ° C. In Example 18, a film similar to that of Example 17 was made, with the exception that the first layer was replaced by C3C4 bipolymer which had a reported melt index of 6.5 decigrams / minute (at 230 ° C / 2.16 kg); a melting point of approximately 131 ° C; and a butene-1 content of 14 weight percent. This copolymer was commercially available from Shell Oil Company, Atlanta, Georgia, E.U.A. under the registered trademark CEFOR SRD4-141. In Example 19, the first layer of the Example 18 to comprise a 70 percent by weight blend of the noted C3C4 polymer, with 30 percent by weight of an anhydride modified linear low density polyethylene adhesive, having a reported melt index of 2 decigram / minute; a density of 0.925; a melting point of about 125 ° C, and was commercially available from Quantum Chemical Company, Cincinnati, Ohio, E.U.A., under the registered trademark Plexar PX360. Examples 17-19 were each irradiated at 4 Mrad, and the surface of the first layer was corona treated. Examples 20 and 21 are Comparative Examples (not of the invention) which are described further below. Examples 17-23 demonstrate a variation of the compositions of the first and second layers, as well as the effect of the addition of an optional plastomeric component to the film. The effect on certain properties of irradiation and corona treatment for, respectively, crosslinking and superficially treating (incorporating polar groups) the film, is also evidenced. Also, Examples 17-19 demonstrate the use of a core layer consisting essentially of a mixture of EVOH and nylon 6/66 copolymer, and the use of a sealant layer using a preferred low melting point propene copolymer. . In each of Examples 17-19 and 22-23, an EVOH core layer having an ethylene content of 44 mole percent was used, - a melt index of 5.5 decigrams / minute, - and a point of fusion of approximately 165 ° C. This EVOH copolymer is commercially available from Eval Company of America of Lisie, Illinois, USA, under the registered trademark EVALCA E 105A. In each of Examples 20-21, an EVOH core layer having an ethylene content of 44 molar percent, - a melt index of 1.6 decigram / minute, - and a melting point of about 165 was used. ° C. This EVOH copolymer is commercially available from Eval Company of America of Lisie, Illinois, USA under the registered trademark EVALCA E 151B. Examples 20 and 21 each used the same copolymer C3C2 in the first layer, and the same very low density polyethylene, EVA, and auxiliary processing in the fifth layer, and the same adhesive in the second and fourth layers that were described for Examples 1-3. The second and fourth layers of Examples 20 and 21 used different EVA resins. The second and fourth layers of Example 20 used 60 percent of an EVA copolymer (EVA A) having a content of 6.1 weight percent vinyl acetate (VA), a density of 0.928 grams / cubic centimeter, - a melting index of 0.3 decigram / minute, - and a melting point of 102 ° C in combination with 40 percent adhesive. This EVA A copolymer is commercially available from EXXON under the registered trademark ESCORENE LD317.09. The second and fourth layers of Example 21 used 55 percent EVA A in combination with 15 percent of the same EVA LD701 (EVA B) used in the fifth layer, - and 30 percent adhesive.

As in Example 1-5, the first (internal) and fifth (external) layers were connected to opposite sides of a third (core) layer (comprising EVOH), by the second and fourth (intermediate) layers that act on part as adhesive layers. The EVOH core layer controlled the permeability of the film with respect to gases such as oxygen. The films of the invention of Examples 17-22 each had a five-layer structure, the layer containing the propene copolymer being the inner layer of the tubular film. These films have stretched biaxially to a proportion of orientation (stretching) in the machine direction (M.D.) of about 31/2: 1, and up to an orientation ratio in the radial or transverse direction (T.D.) of about 3: 1. The relative layer thicknesses (first to fifth layers) of the extruded primary film and any film resulting from Examples 17-19, is believed to be 14.1 percent / 49.7 percent / 9.6 percent / 7.2 percent / 19.4 percent. The relative layer thicknesses (first to fifth layers) of the extruded primary film and any film resulting from Examples 20-23, are believed to be 12.8 percent / 51.3 percent / 6.4 percent / 3 percent / 26.6 percent. Examples 20-21 are Comparative Example of a five layer structure that was biaxially stretched, as described above for Examples 17-19, and had the formulations indicated in Table 11. Example 22 is a similar Example of the invention to Example 14, except that it was not irradiated or treated with corona. Example 23 is a Comparative Example (not of the invention), wherein the formulation was identical to that of Example 22, with the exception that the first layer was modified using 100 weight percent polypropylene homopolymer (PP) (EscoreneMR PP 4092 available from Exxon Chemical Co.), to replace the propene copolymer of Example 22. The PP had a density of about 0.90 grams / cubic centimeter; and a melt index (condition L) of 2.3 decigrams / minute. Referring now to a comparison of the examples, it was determined that the film of the invention of Example 22 was extruded and processed very well, forming a bubble of stable orientation, resulting in a biaxially stretched film of good appearance. The film made in Example 22 had an average caliber of 2.11 mils (53.6 microns); a flat width of 15-7 / 8 inches (40 centimeters), and a shrinkage value M.D. /T.D at 90 ° C of 30 percent / 39 percent. Attempts to process the formulation of Example 23 in a biaxially stretched film failed. The polypropylene homopolymer layer appeared to be very hard. Although a primary tube was well extruded, attempts to orient the film biaxially from the primary tube resulted in a bubble breakage, since the composition of the first layer was changed to a polypropylene homopolymer. Subsequent attempts to form a stable bubble from primary tubes of the test formulation failed due to the bubble breaking during inflation. This demonstrates the low property and undesirability of the polypropylene homopolymer as the main or sole constituent of the film layer, especially the first layer. Different properties of the films of Example 17-22 were measured, and reported in the following Tables 12-14.

TABLE 11 Composition of Layers Ex. No. First Layer Second Layer Third Layer Fourth Layer Fifth Layer (Internal) (core) (external) 17 100% C3C2C4 37.5% VLDPE 90% EVOH Same as 2 to layer 55.6% VLDPE 17.5% EVA 10% Nylon 25% EVA 30% Adhesive 4.4% Processing Aid 15% Plastomer 1 15% Plastomer 18 100% C3C4 Same as Ex. 17 Same as Ex.17 Same as Ex. 17 Same as Ex. 17 19 70% C3C4 Same as Example 17 Same as Example 17 Same as Example 17 Same as Example 17 30% adhesive 20 100% C3C2 60% EVA TO 100% EVOH Same as 2nd layer 70.6% VLDPE 40% Adhesive * 25% EVA 4.4% Auxiliary Processing 21 Same as Ex. 20 55% EVA A Same as Ex. 20 Same as Ex. 20 Same as Ex. 20 15% EVA B 30% Adhesive * 22 Same as Ex. 14 Same as Ex. 14 Same as Ex. 14 Same as Ex. 14 Same as Ex. 14 23 100% PP Same as Ex. 14 Same as Ex. 14 Same as Ex. 14 Same as Ex. 14 * The adhesive is an adhesive of linear polyethylene of low density modified with anhydride, and modified with rubber (Plexar PX 380). ** The Adhesive is an anhydride modified linear low density polyethylene adhesive (Plexar PX 360) TABLE 12 Ex. Caliber WIDTH ELONGATION RESISTENENCOGIENCOGIFERENCE OF FORCE OF No. Average PLANE TO ROMPICIA TO THE BREAST BREAK SHUTTER Thousands (mm) MINOR TRACTION 90 ° C At 74 ° C at 90 ° C at RT at 74 ° C at RT (microns)% XlO3 psi% gm / thousand gm / thousand gm / thousand gm / thousand at RT at RT. MD / TD MD / TD (kg / cm) (kg / cm) (kg / cm) (kg / cm) MD / TD (MPa) MD / TD MD / TD MD / TD MD / TD MD / TD 17 2.58 ND 202/192 8.7 / 7.3 26/39 13/24 110/156 77/134 85/157 67/139 (65.5) (60/50) (43/61) (30/53) (33/62) (26/55) 18 2.95 ND 139/165 7.7 / 6.9 33/40 16/24 133/138 86/118 102/150 83/137 (74.9) (53/48) (52/54) (34/46) (40/59) (33/54) 19 2.68 ND 208/213 9.1 / 7.2 26/36 12/22 121/148 84/136 89/138 73/129 (68.1) (62/49) (47/58) (33/54) (35/54) (29/51) 2.39 400 127/134 7.4 / 8.0 21/35 9/18 103/181 73/131 76/158 67/133 (60.7) (51/55) (41/71) (29/52) (30/62) (26/52) 21 2.15 406 117/134 7.5 / 7.9 19/34 9/18 100/179 66/128 78/155 70/136 (54.6) (52/55) (39/70) (26/50) (31/61) (28/54) ND = NOT DETERMINED TA = AMBIENT TEMPERATURE (approximately 20-23 ° C).

TABLE 13 Ex. Modulus RESISTANCE TO PERFORATION DRILLING WITH NEBULOSITY BRIGHTNESS IN A No. Drying of DYNAMIC WEIGHT H20 HOT TO% NUMBER OF 45 ° 1% MD / TD cmkg / μ 95 - C MD / TD glμ μ / seconds 17 310/504 1.1 / 1.4 0.04 64.5 / 24 6.4 64 18 311/314 1.4 / 1.3 0.06 75.2 / 38 '10.8 69 19 316/309 0.91 / 0.94 0.04 77.0 / 25 19.2 49 330/345 1.1 / 1.2 ND 64.3 / 28 '3.4 81 21 322/339 0.90 / 0.93 ND 61.0 / 20 5.4 81 ND = NOT DETERMINED The value reported is the average of 4 samples; Two other samples tested > 120 seconds for films with an average thickness of 86.1 microns. The reported value is the average of 5 samples; Another sample tested > 120 seconds for a film of average thickness of 66.3 microns.

TABLE 14 Ex. ENERGY SEAL RANGE SEAL RESISTANCE IMPROVED SURFACE NO. Hot Rod Seal Impulse Seal (dynes / cm) min / max. TA / 160 ° F (71 ° C) / 190 ° F (88 ° C) at 160 ° F (71 ° C) (volts) (cm) at 35 40v / 45v / 50v (g / cm) 17 36 43/47 1470/946/683 ND 18 36 43/50 2050/983/629 ND 19 36 42/49 ND ND ND ND 1240/883/760 290/252/270/357 21 ND ND 1590/770/713 309/256/266/304 ND = NOT DETERMINED TA = AMBIENT TEMPERATURE (approximately 20-23 ° C) The seal tested was a factory seal, and the factory seal method was not determined.

Referring now to Tables 11-14, Examples 17-19 show all test results demonstrating that the films produced have useful properties for packing articles. The Examples not only demonstrate that the first layer can utilize bipolymers and terpolymers, but that the core layer can be varied to include a nylon polymer such as a nylon 6/66 copolymer. Propene polymers suitable for use in the invention have at least 60 weight percent propene polymerized with different amounts of one or more α-olefin comonomers. Preferably, the melting point of these propene-based polymers is less than 140 ° C. It is seen that the addition of adhesive to the first layer of Example 19 produced a film with suitable properties, but the optical properties and tear resistance were not as good as those of the films of Example 17 and 18. The films of the Comparative Examples 20 and 21 demonstrate a lower pulse seal resistance, as seen by a comparison with the above samples 4-6 and 14-16 of the invention. This resistance of the lower impulse seal is believed to be due to the absence, in the second and fourth layers, of at least 10 weight percent of an ethylene copolymer with at least one α-olefin of 4 to 8 carbon atoms. carbon having a copolymer density of 0.900 to less than 0.915 grams / cubic centimeter, a melt index of less than 1.0 decigram / minute, and a melting point of at least 90 ° C. The films, bags and packages of the present invention may also employ combinations of features, as described in one or more of the claims, including in the dependent claims that follow this specification, and where they are not mutually exclusive, the characteristics and Limitations of each claim may be combined with the features or limitations of any of the other claims to further describe the invention. The above examples serve only to illustrate the invention and its advantages, and should not be construed as limiting, since other modifications of the invention described will be apparent to those skilled in the art in view of this teaching. All such modifications are considered within the scope of the invention as defined by the following claims.

Claims (48)

1. A multilayer packaging film having at least five layers configured in sequence, and one in contact with the others, which comprises: a first layer comprising at least 50 weight percent of a propene copolymer, and when minus one α-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1, and mixtures thereof, which has a propene content of at least 60 percent in weigh; second and fourth layers, each comprising at least 10 percent of a first copolymer of ethylene and at least one α-olefin of 4 to 8 carbon atoms, this copolymer having a density of 0.900 to 0.915 grams / cubic centimeter, and a melt index of less than 1.0 decigram / minute, and at least 10 percent of a second ethylene copolymer with 4 to 18 percent of a vinyl ester or alkyl acrylate, and at least 10 percent of a third copolymer of ethylene with at least one α-olefin, one vinyl ester, or one alkyl acrylate, modified with anhydride, and from 0 to 30 percent of a fourth copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms that have a density less than 0.900 grams / cubic centimeter, and a melting point lower than 85 ° C; a third layer comprising at least 80 percent by weight of EVOH copolymer, having an ethylene content of at least 38 mole percent; and a fifth layer comprising at least 30 weight percent of a first copolymer of ethylene with at least one α-olefin of 4 to 8 carbon atoms, the first copolymer having a density of 0.900 to 0.915 grams / cubic centimeter, and a melt index of less than 1.0 decigrams / minute, and at least 10 percent of a second ethylene copolymer with 4 to 18 percent of a vinyl ester or alkyl acrylate, and 0 to 30 percent of a third copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85 ° C.

2. A film, as defined in claim 1, wherein the propene content of the copolymer of the first layer is at least 80 percent, based on the weight of this copolymer.

3. A film, as defined in claim 1, wherein the propene content of the copolymer of the first layer is at least 90 percent, based on the weight of this copolymer.

4. A film, as defined in claim 1, wherein the propene content of the copolymer of the first layer is at least 95 percent, based on the weight of this copolymer.

5. A film, as defined in claim 1, wherein the first layer comprises C3C2 copolymer.

6. A film, as defined in claim 1, wherein the first layer comprises at least 75 weight percent C3C2 copolymer.

7. A film, as defined in claim 1, wherein the first layer comprises random copolymer C3C2.

8. A film, as defined in claim 1, wherein the first layer comprises random copolymer C3C2 having a melting point of less than 140 ° C.

9. A film, as defined in claim 1, wherein the first layer comprises C3C2 copolymer polymerized from a process using a metallocene catalyst.

10. A film, as defined in claim 1, wherein the first layer consists essentially of C3C2 copolymer.

11. A film, as defined in claim 1, wherein an outer surface of the first layer has a surface energy of at least 29 dynes per centimeter.

12. A film, as defined in claim 11, wherein the surface energy of the first layer is from 35 to 38 dynes per centimeter.

13. A film, as defined in claim 1, wherein the first copolymer of the second, fourth, and fifth layers, comprises an ethylene-to-olefin copolymer having at least 80 percent of its polymer units derived from ethylene.

A film, as defined in claim 1, wherein the first copolymer of the second and fourth layers comprises from 10 to 70 percent of this layer.

15. A film, as defined in claim 1, wherein the second copolymer of the second layer and the fourth layer, each comprising 10 to 40 percent of said second and fourth respective layers.

16. A film, as defined in claim 1, wherein the third copolymer of the second and fourth layers comprises from 10 to 60 percent of each of these layers.

A film, as defined in claim 1, wherein the fourth copolymer of the second and fourth layers comprises at least 10 percent of each of these layers.

18. A film, as defined in claim 1, wherein the second layer of the film comprises a thickness of 25 to 70 percent of the thickness of the multilayer film.

19. A film, as defined in claim 1, wherein the second layer of the film further comprises a copolymer of propene and at least one α-olefin selected from the group consisting of ethylene, butene-1, methylpenteno- 1, hexene-1, octene-1 and mixtures thereof, which have a propene content of at least 60 weight percent.

20. A film, as defined in claim 1, wherein the third layer of the film comprises from 3 to 13 percent of the total film thickness.

21. A film, as defined in claim 1, wherein the EVOH copolymer has a melting point of about 175 ° C or less.

22. A film, as defined in claim 1, wherein the EVOH copolymer has a melting point of about 165 ° C or less.

23. A film, as defined in claim 1, wherein the third layer consists essentially of EVOH.

24. A film, as defined in claim 1, wherein the third layer comprises at least 10 weight percent nylon 6/66 copolymer.

25. A film, as defined in claim 1, wherein the third copolymer of the fifth layer comprises at least 10 percent of this layer.

26. A film, as defined in claim 1, wherein the EVOH has an ethylene content of at least 44 mole percent.

27. A film, as defined in claim 1, wherein the third layer consists essentially of EVOH and nylon.

28. A film, as defined in claim 1, wherein the third layer further comprises nylon 6/66 copolymer having a melting point of about 195 ° C.

29. A film, as defined in claim 1, wherein the fourth layer of the film comprises a thickness of 1 to 35 percent of the thickness of the multilayer film.

30. A film, as defined in claim 1, wherein the fifth layer is an outer surface layer.

31. A film, as defined in claim 1, wherein the first copolymer of the fifth layer comprises at least 40 to 75 percent; and the second copolymer comprises at least 10 to 40 percent of this layer.

32. A film, as defined in claim 1, wherein the film can be shrunk by heat at 90 ° C.

A film, as defined in claim 1, wherein the film has a shrinkage value of at least 20 percent at 90 ° C both in the machine direction and in the transverse direction.

34. A film, as defined in claim 1, wherein the film has a shrinkage value of at least 30 percent at 90 ° C at least in one direction.

35. A film, as defined in claim 1, wherein the film has a shrinkage value of at least 10 percent at 74 ° C at least in one direction.

36. A film, as defined in claim 1, wherein the film has a shrinkage value of at least 20 percent at 74 ° C, at least in one direction.

37. A film, as defined in claim 1, wherein the film is formed as a bag, the first layer being a heat-sealable inner surface layer of the bag, and the fifth layer being an outer surface layer of this bag .

38. A film, as defined in claim 1, wherein at least one of the layers further comprises polypropylene, a propylene-ethylene copolymer, an ionomer, nylon, polyethylene, an ethylene-vinyl ester, a polyolefin, a polyethylene linear low density, a linear polyethylene of medium density, a low density polyethylene, a high density polyethylene, an elastomer, a plastomer, or mixtures of one or more thereof.

39. A film, as defined in claim 1, wherein the film has an oxygen transmission rate of less than 20 cubic centimeters per square meter to 24 hours at one atmosphere, with relative humidity of 0 percent, and at about 73 ° F (approximately 23 ° C).

40. A film, as defined in claim 1, wherein the film is irradiated.

41. A film, as defined in claim 1, wherein the film is irradiated between about 2 and 8 Mrad.

42. A film, as defined in claim 1, wherein the fifth layer of the film is crosslinked.

43. A film, as defined in claim 1, wherein the film has a haze value of less than 12 percent.

44. A film, as defined in claim 1, wherein the film has a brightness at 45 °, is greater than 65 Hunter Units.

45. A process for manufacturing a biaxially stretched, heat-shrinkable, heat-sealable, multilayer oxygen film resistant to delamination, which comprises: (a) coextruding, in a tubular form, about one volume of air, molten plasticized polymeric resins, forming a primary tube having at least five, from the first to the fifth, concentric layers in sequence, one in contact with others, which include: (i) a first layer comprising at least one 50 weight percent of a propene copolymer, and at least one α-olefin selected from the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1, and mixtures thereof, having a propene content of at least 60 weight percent; (ii) second and fourth layers comprising at least 10 percent of a first copolymer of ethylene, and at least one α-olefin of 4 to 8 carbon atoms, this copolymer having a density of 0.900 to 0.915 grams / cubic centimeter , and a melt index of less than 1.0 decigram / minute, and at least 10 percent of a second ethylene copolymer with 4 to 18 percent of a vinyl ester or alkyl acrylate, and at least 10 percent of a third copolymer of ethylene with at least one α-olefin, a vinyl ester, or an alkyl acrylate, modified with anhydride, and from 0 to 30 percent of a fourth copolymer of ethylene and at least one α-olefin of 3 at 8 carbon atoms that has a density less than 0.900 grams / cubic centimeter, and a melting point lower than 85 ° C; (iii) A third layer comprising at least the 80 weight percent EVOH copolymer, which has an ethylene content of at least 38 mole percent; and (iv) A fifth layer comprising at least 30 percent of a first copolymer of ethylene with at least one α-olefin of 4 to 8 carbon atoms, this first copolymer having a density of 0.900 to 0.915 grams / cubic centimeter , and a melt index of less than 1.0 decigrams / minute, and at least 10 percent of a second ethylene copolymer with 4 to 18 percent of a vinyl ester or alkyl acrylate, and 0 to 30 percent of a third copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85 ° C; wherein the third layer comprises < . 13 percent of the total thickness of the primary tube, the second layer comprises from 25 to 70 percent of the total thickness of the primary tube, and the fourth layer comprises from 1 to 35 percent of the total thickness of the primary tube; (b) cooling and collapsing the primary tube; (c) reheating the primary tube to an orientation temperature (stretching); (d) biaxially stretching, in a simultaneous manner, the primary tube, forming an expanded, biaxially stretched secondary tube, having a continuous core layer of less than 3.3 microns thick; and (e) rapidly cooling the drawn film, thereby forming a heat-shrinkable film.

46. A process, as defined in claim 45, wherein the heat-shrinkable film is irradiated after the cooling step (e) of the stretched film.

47. A process, as defined in the claim 45, which further comprises heat sealing a portion of the first layer with itself or with an outermost one of this film, forming a heat seal, wherein the film has an average seal drag at the time of the largest rupture of the film. 60 minutes at 165 ° F (74 ° C).

48. A multilayer packaging film, which comprises a heat seal layer of at least 90 percent propylene-ethylene random copolymer, having a melting point of less than 140 ° C; a core layer having a thickness between about 1.27 microns and about 3.3 microns, comprising about 0 to 20 weight percent of nylon 6/66 copolymer, and about 80 to 100 weight percent of a copolymer of EVOH having an ethylene content of at least about 38 mole percent; an outer protective layer of at least 30 percent of a first ethylene copolymer with between 5 and 20 percent of at least one α-olefin of 4 to 8 carbon atoms, the first copolymer having a density of 0.900 to 0.915 grams / cubic centimeter, and a melt index of less than 1.0 decigram / minute, and at least 10 percent of a second ethylene copolymer with 4 to 18 percent of a vinyl ester or alkyl acrylate, and 10 at 30 percent of a third copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter, and a melting point of less than 85 ° C; and first and second adhesive layers; wherein the core layer is between the first and second adhesive layers, (1) adhering the first adhesive layer to a first surface of the core layer, the first adhesive layer being located between the heat seal layer and the core layer , and (2) adhering the second adhesive layer to a second opposing surface of the core layer, the second adhesive layer being located between the outer protective layer and the core layer, and these adhesive layers comprising at least 10 percent of the first ethylene copolymer with between 5 and 20 percent of at least one α-olefin of 4 to 8 carbon atoms, the first copolymer having a density of 0.900 to less than 0.915 grams / cubic centimeter, and a melt index of less than 1.0 decigrams / minute, and at least 10 percent of a second copolymer of ethylene with 4 to 18 percent of a vinyl ester or alkyl acrylate, and at least 10 percent of a third copolymer of ethylene with at least one α-olefin, one vinyl ester, or one alkyl acrylate, modified with anhydride, and 10 to 30 percent with a fourth ethylene copolymer and between 5 and 25 percent with less an α-olefin of 3 to 8 carbon atoms having a density less than 0.900 grams / cubic centimeter, and a melting point lower than 85 ° C; and wherein at least one of the layers is crosslinked. SUMMARY A multilayer film, preferably biaxially oriented, suitable for processing and / or packing cooked foods indoors, such as ham, beef, and poultry, which has an excellent combination of oxygen barrier properties, heat seal , and optics, comprising at least five essential layers in sequence, with a first layer of a propene copolymer and at least one α-olefin of 2 to 8 carbon atoms having a propene content of at least 60 percent by weight, and preferably having a melting point < 140 ° C; a second layer of (1) a first copolymer of ethylene and at least one α-olefin of 4 to 8 carbon atoms having a density of 0.900 to 0.915 grams / cubic centimeter, and a melting point of less than 1.0 decigram / minute , (2) a second ethylene copolymer with 4 to 18 percent, preferably 4 to 12 percent, of a vinyl ester or alkyl acrylate, (3) a third copolymer of ethylene with at least one α-olefin , a vinyl ester, or an alkyl acrylate, modified with anhydride, and (4) optionally a fourth copolymer of ethylene and at least one α-olefin of 3 to 8 carbon atoms having a density of less than 0.900 grams / cubic centimeter , and a melting point lower than 85 ° C; a third layer of EVOH; a fourth layer as the second layer; and a fifth layer of a first ethylene copolymer with at least one α-olefin of 4 to 8 carbon atoms having a density of 0.900 to 0.915 grams / cubic centimeter, and a melt index of less than 1.0 decigram / minute, and a second ethylene copolymer with 4 to 18 percent, preferably 4 to 12 percent, of a vinyl ester or alkyl acrylate, and optionally a third copolymer of ethylene and at least one α-olefin of 3 to 8 atoms carbon that has a density less than 0.900 grams / cubic centimeter, and a melting point lower than 85 ° C.