MXPA99010506A - Puncture resistant, high shrink films, blends, and process - Google Patents

Abstract

A polymer blend and mono-and multilayer films made therefrom having an improved combination of properties such as high shrinkage values and high puncture resistance wherein the blend has a first copolymer of ethylene and octene-1 having a copolymer melting point of from 55 to 95 DEG C, preferably of from 80 to 92 DEG C;a second copolymer of ethylene and at least one alpha -olefin having a copolymer melting point of from 115 to 128 DEG C:and a third copolymer of ethylene and a vinyl ester or alkyl acrylate and having a melting point of from 60 to 110 DEG C, and a process for making such films, which preferably have at least 45%shrinkage at 90 DEG C in at least one direction.

Description

FILMS. MIXES OF HIGH SHREDDING, RESISTANT TO DRILLING, AND PROCESS Cross Reference to Related Requests This application is a continuation in part of the patent applications of E.U.A. pending numbers: 09 / 192,845, filed on November 16, 1998; 09 / 168,282, filed on October 8, 1998; and 09 / 401,692, filed on December 22, 1999, which are incorporated herein by reference.

BACKGROUND OF THE INVENTION The invention relates to mixtures of C2-olefin thermoplastic copolymer resin and its flexible films having heat shrink / puncture resistance properties. Such mixtures are useful for making films, particularly oriented, heat sealing films for packaging items and for processing and / or packaging food items, especially cooked foods subjected to pasteurization processes as well as fresh, frozen or processed foods such as meat, Birds, or cheese. Manufacturers and wholesalers use thermoplastic packaging films, flexible to provide economic, sanitary containers, which help protect and / or preserve the freshness and healthiness of their products. These films are usually sold in the form of a bag. For example, a single or multi-layer film is made in the form of bags using a tubular film or one or more flat sheets or webs, through well-known processes involving, for example, cutting, bending and / or sealing of the film to form the bags. These films and bags can be printed and can also be uniaxial or biaxially oriented, heat shrinkable, irradiated, or they can contain layers that are resistant to abuse or puncture resistant or which are interlaced or that improve or delay or prevent transmission of light, gases or liquids through them. Frequently, multilayer films having one or more oxygen and / or moisture barrier layers, such as: sarán (a copolymer of polyvinylidene chloride); an improved saran, for example, containing methyl acrylate polymer units; ethylene vinyl alcohol copolymer; nylon; or acrylonitrile, can be used with a heat sealing layer, such as a copolymer of ethylene and vinyl acetate (EVA) to produce bags for packaging oxygen sensitive food and / or moisture, for example processed pork meat or red meat cool Said bags help to preserve the meat in its original condition avoiding or reducing the loss of moisture or chemical changes in the structure of the meat due to oxidation reactions. A typical packaging bag has 1-3 sides sealed with heat by the manufacturer of the bag, leaving an open side to be able to insert the product. For example, a processor can insert, fresh, frozen or processed, meat, ham, poultry, cheese, prime or semi-primordial cuts of meat, ground beef, fruits, vegetables, bread or other products, making a final stamp for tightly seal the product in the bag. This final seal can be followed by gas evacuation (i.e., vacuum removal) or replacement of the gaseous environment within the bag by one or more gases to provide some advantage, such as assisting in the preservation of the product. This final seal is often a heat seal similar to the initial seals produced by the manufacturer of the bag, although the actual heat sealing equipment may vary. In this way, the bags are made by: transversally sealing a monolayer or multi-layer tubular film material and cutting the portion of tube containing the sealed end; making two separate transverse seals on the tubular material and cutting to open the side of the tube; superimposing flat sheets of film and sealing all three sides; or by folding a flat sheet and sealing two sides. In general, heat seals are made by applying heat and sufficient pressure to the adjacent film layer surfaces for a sufficient time to cause a fusion bond between the layers of plastic film. A common type of seal used to make bags is known to those skilled in the art as a bar seal _ .: > hot. To make a hot bar seal, adjacent thermoplastic layers are gathered by opposing bars of which at least one is heated to cause the layers to fuse into a union through the application of heat and pressure through the area It will be sealed. For example, the bags can be made from a tubular material by making a hot bar bottom seal transverse to a tubular film. Once the bottom seal is made, the tubular material is transversely cut to form the mouth of the bag. After inserting a product, the bag is typically evacuated and the mouth of the bag is sealed to enclose the product. At one point, the standard method for sealing was to place a fastener around the mouth of the bag. However, heat sealing techniques are now commonly used to produce the final closure of the bag. For example, a bag mouth can be either sealed by hot rod or impulse sealed. An impulse seal is made through the application of heat and pressure using opposite bars similar to the hot bar seal, except that at least one of these bars has a covered wire or strip, through which electric current is passed for a very short period (hence, the name "impulse") to cause the adjacent film layers to merge. Following the heat pulse, the bars are typically cooled (for example, by circulating a coolant), while continuing to hold the inner surfaces of the bag together to obtain adequate sealing strength.

With regard to hot bar seals, impulse seals can be made faster due to the rapid cooling of the lath after the heat pulse. The impulse seals are also generally narrower, giving an improved appearance of packing, but the narrower seals also leave less margin for error in the production of continuous sealed edges. Usually, less area is attached in an impulse seal are related to a hot bar seal, in this way the operation of the sealing layer of the film is more critical. Disadvantageously, the film in the seal area is generally extruded during the impulse sealing of known films. This results in thinning of the film and a reduction in the strength of the film in the seal area. In extreme situations, the thin film is cut or separated. Those skilled in the art refer to severely extruded stamps as "burn" stamps. A "burned" seal does not have adequate strength or integrity to protect the packaged product. An attempt to solve this problem of "burning" is to irradiate the film before the manufacture of the bag. The irradiation of a film made of interlacing polymer resins causes the resin layers, in the film, to interlace. Under controlled conditions, the entanglement by irradiation arises and can also expand the temperature scale for heat sealing, and depending on the composition of the film can also improve the puncture resistance of the film. If the heat sealing layer of the thermoplastic film is too interlaced, fusion bonding which makes difficult stronger seals is more difficult, particularly through impulse sealing. All bag seals must maintain their integrity to preserve and protect enclosed products, especially food products. There must be a strong continuous seal to prevent the discharge and unwanted entry of gaseous materials, liquids or solids between the outside and inside of the bag. This is particularly necessary when the packaging is made of a heat-shrinkable film and is to be submerged in hot water to shrink the film against the packaged item, since such shrinkage increases the tension on these stamps. It is even more critical when the packages are going to be submerged during times and temperatures sufficient for pasteurization and cooking. In this way, there is a continuing need for films that can be made in bags having strong seals especially those formed by hot bar and / or impulse sealing. Said films must provide strong seals capable of withstanding a temperature scale and they must also be able to make said seals on a wide scale of sealing temperature without presenting the burning. It is known that there are variations in the temperatures, times and sealing pressure of one brand or type of sealant to another, and also between different sealing machines sold under the same brand. This increases the desire for films that can be usefully sealed in different sealing machines and over a wide variety of temperatures to produce strong integral seals. Another problem of heat sealing is that of inadvertent folding. Normally, a heat seal is made by applying heat and pressure through two portions of film, however, occasionally the area to be sealed will inadvertently be bent to produce a section of film having four or six portions of film, which they are compressed between the opposite sealing bars. In such situations, it is desirable to be able to seal the film without burning. A very wide heat seal temperature scale is indicative of a greater latitude in the seal through the bends than a narrower scale. "Another problem during heat sealing is that of excessively high rupture propagation resistances. The lower rupture propagation resistances are an advantage in heat sealing operations using impulse sealing technology, where the sealing apparatus both seals and cuts the film with the film flange being removed breaking at length of the cut. The low rupture propagation resistances allow rapid removal of the flange without damaging the seal, film or bag. A very demanding application for thermoplastic, heat-sealable flexible films is for processing meats. Bacterial contamination during food processing, for example, by monocytogenes is of great concern. To address health and safety issues with processed foods, some processors have adopted a surface heat treatment at elevated temperatures, sufficient to kill bacteria that are already in the cooked food. In some demand applications, a food product, such as ham, is sealed inside a plastic processing bag or film, where the ham is cooked, refrigerated, shipped and subsequently displayed for retail sale. In a more common demand application, the food, such as turkey breast, ham or meat, is cooked in a pan, or the processing film from which the cooked food is removed for further processing, such as slicing.; smoked in a smoking station; treatment with dyes and / or flavorings such as caramel, spices, liquid smoked or honey; glazed; and / or liquid removal (known as purging) resulting, for example, in the cooking process. After this additional processing, the food product is packaged, usually in a printed bag, for shipment and sale. The cooked food is typically placed in a heat-shrinkable, heat-sealable bag, which is then emptied of the atmospheric gases through vacuum, heat-sealed and subjected to a film shrink operation usually in a water tank. a high temperature for a short period to produce attractive, compact packaging. During these steps that follow the cooking and occur before packing for shipment and sale, the surface of the food product is subject to environmental contamination, for example, through particles that are carried by air, microbes and dust, the risk of contamination after packing it can be minimized by pasteurizing the sealed sealed package over the surface, for example, in a water bath or steam chamber, maintained at elevated temperatures for a sufficient time to provide the desired degree of contamination protection and microbial growth. The time and temperatures of this post-cooking pasteurization step can vary widely. Significantly, this surface treatment is additional to the cooking, cooking or pasteurization process and follows the hermetic sealing of cooked or pasteurized food in a plastic packaging film. In this demanding use, this surface treatment of "post-cooking pasteurization" is carried out after placing the food in the packaging film that will remain in the pasteurized product through sale to a last customer. In general, the films are printed with consumer information and brand identification and frequently at least a portion of the film is transparent to be able to see the product enclosed. Therefore, the optical properties and the appearance of the films are important for the perception and sale to the client. This "post-pasteurization" film must also perform a variety of functions. It must be resistant to perforation and have strong seals at the elevated temperatures found in the shrink operation, and also with the post-cooking pasteurization process. It should also maintain a tight conformation of the film around the product at cooling temperatures with an attractive appearance and act as a good barrier to oxygen, moisture and environmental contaminants. Various polymers, mixtures thereof and multi-layer films have been employed in an attempt to address the market's prior needs. Previously ethylene vinyl ester copolymers, such as vinyl acetate, have been described as materials, useful in monolayer and multilayer thermoplastic films and are known to provide heat sealing properties. An example of a bag for fresh red meat currently in the trade is a film that has three layers, which are coextruded and oriented. The core or middle layer of the film is a barrier material for oxygen and moisture, the outer layer provides abrasion resistance and is formulated to provide support for the film during the expansion of the primary tube for orientation, and the inner layer provides properties seal with heat and contributes to the resistance to perforation. The core or barrier layer of this film is a relatively small percentage of the total film thickness and is made of a polyvinylidene chloride-vinyl chloride copolymer (PVDC or VDC-VC) or vinylidene chloride-acrylate copolymer. methyl (VDC-MA or MA-saran). The outer layer is thicker than the core layer and is a mixture of very low density polyethylene (VLDPE) and EVA. The VLDPE, also called ultra low density polyethylene (ULDPE) is a class of ethylene-alpha olefin copolymers having a density ranging from less than 0.915 g / cm3 to less than approximately 0.860 g / cm3, and many VLDPE resins are available having densities from 0.900 to 0.915 g / cm3. The EVA and VLDPE components contribute to the shrinkage properties of the film and the VLDPE component contributes to the g, abrasion and perforation resistance. VLDPE also adds resistance to orientation to minimize ruptures of the secondary bubble during expansion of the softened primary tube. By far, the thickest film layer is the inner or heat seal layer. In the above film, this layer is more than 60% of the total film thickness and comprises a mixture of VLDPE and EVA. The seal layer with heat significantly contributes to the puncture resistance of this film. Another desirable feature provided by this layer is the heat seal temperature scale. It is preferred that the temperature scale for heat sealing the film is as wide as possible. This allows a greater variation in the operation of the heat sealing equipment in relation to a film having a very narrow scale. For example, it is desirable that a suitable film be heat sealed on a temperature scale of 176.6 ° C to 287.7 ° C, providing a heat sealing window of 93.3 ° C. Films similar to the general structure and composition described above have been in commercial use for many years, but efforts are still being made to increase drilling resistance while maintaining processability, a wide heat seal temperature scale and a high degree of heat resistance. high degree of shrinkage both in the machine direction (MD) and in the transverse direction (TD). Recent developments to improve the properties of a shrinkable film with heat include the US patent. No. 5,272,016 (Ralph). The '016 patent improves the properties of a multilayer non-oxygen barrier film through the use of a mixture of EVA, VLDPE and Plastomer. The patent of E.U.A. No. 6,635,261 (Georgelos et al.), Said application is incorporated herein by reference, discloses useful EVA blends for their heat sealing properties. The patent of E.U.A. No. 5,397,640 (Georgelos et al.) Discloses a multilayer oxygen barrier film using a mixture of three components of VLDPE, EVA, and a Plastomer. (See, for example, Example 7). The patent of E.U.A. No. 5,403,668 (Wilhoit) discloses a multi-layer heat shrinkable oxygen barrier film using a four component mixture of VLDPE, LLDPE, EVA, Plastomer. The patent of E.U.A. No. 5,759,648 (Idlas) discloses a five layer film having a heat sealing layer of C3C2, a VEO layer, and a surface layer of VLDPE connected through special adhesive blend layers. This film is particularly useful in cooked processing and / or packaging applications. The patent of E.U.A. No. 5,928,740 (Wilhoit et al.) Discloses a flexible film having a mixture of an ethylene alpha-olefin copolymer (EAO) having a melting point (m.p.) of between 55 to 75 ° C.; a second EAO having a p.f. between 85 to 110 ° C; and an unmodified thermoplastic polymer of EAO, LDPE, HDPE or propylene copolymers, having a m.p. between 115 to 130 ° C. These films may be heat-shrinkable, multi-layered, biaxially stretched films. Recent changes in polymer manufacturing in catalysts and processes have proven increasing numbers of polymeric resins having different melting characteristics, melting points and narrow molecular weight distributions (MWD). The MWD is the ratio of Mw / Mn, where Mw is the average molecular weight of the resin and Mn is the number average molecular weight. For example, the oldest EAO and VLDPE resins have a MWD on the scale of about 3.5 to 8.0. Improvements in catalysis technology have been able to produce many resins, where this ratio has been reduced below 3, usually on the scale of about 1.5 to about 2.5, and very typically about 2.0. A narrower MWD means that the polymer chains of these resins are more uniform in length. A resin with a higher MWD can be said to comprise polymer chains of more varied lengths. Other changes in resin properties have been attributed to differences in the distribution of alo long comonomer structure of ethylene resulting in materials produced from single site catalysts having a melting point lower than a polymer produced from multi-site catalyst of comparable density and melt index. Also, in the case of the above commercial film, wherein the seal layer heat is primarily a blend of EVA and VLDPE, it was found that using a VLDPE with a Mw / Mn narrower, having a melting point lower instead of a VLDPE with a wider Mw / Mn, having a higher melting point, the sealing scale with operable heat was considerably reduced. For example, when ia sealing layer used only in the mixture, a VLDPE point lower melting, with a Mw / Mn very narrow, the seal temperature heat was on the order of 204.4 ° to about 246.1 ° C , giving a sealing window of only 23.8 ° C. Past attempts to provide improved puncture resistance and heat sealing in films, while making some progress, left much to be desired. Variability in its heat sealing and process parameters continue to produce bags with weak seals, which are subjected to breakage and stress on the seals during cutting operations, the with which are subjected to burning, which fail to seal folds , and that produce leaking bags having discontinuous seals and that are not sufficiently resistant to perforations. It would be highly desirable to have films and biaxially stretched, shrinkable bags with heat, which are highly puncture resistant and / or whose seal layer heat in particular and film construction in general allow flexibility and greater variability in the parameters of the sealing process, while more continuous, integral, strong and with a lower failure rate relative to films and bags of the prior art occurring more rapidly. Accordingly, an object of the present invention is to provide a novel polymer blend having an improved combination of properties. It is another object to provide a film of sufficient integrity to withstand the firing process with intact seals and film layers. It is another object to provide a film with sufficient integrity to withstand post-cooking pasteurization with intact seals and film layers.

Another object is to provide a flexible film having improved heat sealing properties. Another object is to provide a heat-shrinkable, biaxially oriented monolayer or multi-layer film having a high puncture and / or energy absorption resistance. Another object is to provide a monolayer or multi-layer heat-shrinkable, biaxially oriented film having a high puncture resistance. Another object is to provide a heat-shrinkable, biaxially oriented monolayer or multi-layer film having high values in shrinkage. Another object is to provide a heat-shrinkable monolayer or multilayer film having an improved combination of high puncture resistance and high shrinkage values. Still another object is to provide a heat-shrinkable, multilayer film having puncture resistance and a heat seal scale suitable for use in fresh bone meat packaging. Yet another object is to provide a heat shrinkable multilayer film having a combination of hot water puncture resistance and heat seal resistance suitable for use in meat pasteurization processing and having low turbidity and a high brightness suitable for retail packaging. A further object is to provide a heat-shrinkable film having an improved combination of optical properties and heat sealing, and resistance to puncture and abrasion. It is an object of the invention to provide a film for packaging food such as turkey breasts, meat or hams, which are cooked and shipped in the same film. It is another object of the invention to provide a process for making a multi-layer film of processing or packaging, of oxygen barrier having excellent optical properties, strong seals, puncture resistance in hot water and at room temperature, and high values of Shrinkage at 90 ° C. The above objects and others, benefits and advantages of the invention will be apparent from the description that follows, which is illustrative and not limiting. It is not necessary that each of the objects listed above in find in all embodiments of the invention. It is sufficient that the invention be usefully employed.

SUMMARY OF THE INVENTION According to the present invention, a novel flexible, biaxially stretched, heat-shrinkable, thermoplastic film is provided, comprising at least one layer and is suitable for use in the manufacture of bags for packaging, for example, food items such as primordial or subprofessional cuts of meat. A special blend of the invention of at least three copolymers is suitable to be formed into a wide variety of articles including packaging films useful for packaging food and articles other than food and the like. In these various embodiments, the mixture of the invention can be used to make films of the invention of superior properties and combinations of properties with respect to the films of the prior art. These films of the invention can have excellent properties in relation to: heat shrinkability, optical properties, puncture and abrasion resistance, flexibility, heat sealing properties, and / or lower breaking strengths, as well as good combinations of said properties. Turbidity values of 10% or less can be obtained with various embodiments of the present invention. The film of the invention comprises a mixture having a first polymer having a melting point of 55 to 95 ° C, preferably 80-85 ° C, comprising a copolymer of ethylene and octene-1; a second polymer having a melting point of 115 to 128 ° C comprising ethylene and at least one α-olefin; and a third polymer having a melting point of 60 to 110 ° C comprising an ethylene copolymer, unmodified or modified with anhydride, with an alkyl acrylate, acrylic acid, methacrylic acid, or vinyl ester; and optionally a fourth polymer having a melting point of between 91 to 110 ° C (preferably 91 to 105 ° C), preferably selected from the group of ethylene homopolymers such as HDPE and LDPE, and copolymers of ethylene with minus one α-olefin. Beneficially, the present invention provides a biaxially stretched film having an improved combination of properties especially high puncture resistance values, for example, maximum puncture forces of at least 65 Newtons and usually at least 90 Newtons or more, and high values of shrinkage at low temperatures of 90 ° C or 80 ° C, for example, at least 45% shrinkage at 90 ° C in at least one, and preferably both machine and transverse directions, and excellent optical properties . Also various embodiments of the invention may have desirable rupture strengths, for example, an "x" rupture strength such as 15 < x = 70 grams per thousand., either in any or in each of the directions of the machine and transversal, or of x < 40 grams per thousand., In at least one of the directions of the machine and crosswise, without sacrificing high shrinkage at 90 ° C and other desirable properties. In some embodiments of the invention, films having break strengths of about 0.59 to 1.38 g / μ are obtained in either or both of the machine and transverse directions. Additional embodiments of the invention include films that achieve: a puncture resistance by hot water using a metal probe of at least 25, preferably at least 40, and most preferably at least 100 seconds at 95 ° C; a seal resistance against hot water of at least 100, preferably at least 200, most preferably at least 300 seconds at 95 ° C; a seal resistance to the tension of at least 400, preferably of at least 600 g / cm at 88 ° C; a maximum drilling force of at least 65 Newtons, preferably at least 80 Newtons; a shrinkage value at 90 ° C of at least 40% in at least one direction; a shrinkage value at 80 ° C of at least 35% in at least one direction; a turbidity value of less than 10%; and / or a brightness value at 45 ° C of at least 70 Hunter Units; and preferably combinations of several of these properties. A preferred four-layer embodiment of the invention that is well suited for processing and / or packaging pasteurization in cooking or post-cooking has: (a) a heat sealing surface layer of at least 50% by weight of, (i) a copolymer of propene 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% by weight, or (ii) at least 50% by weight of an ethylene copolymer and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene -1, octene- 1, and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm 3, (b) a second polymeric layer having (i) of 25 a 85% of a first polymer having a melting point of 55 to 95 ° C of ethylene and octene-1, (ii) of 5 to 60% of a second polymer having a melting point from 115 ° C to 128 ° C of ethylene and at least one C4-C8 α-olefin, and (iii) from 0 to 50% of a third copolymer unmodified or modified with anhydride having a melting point of 60 to 110 ° C of ethylene with a vinyl ester, acrylic acid, methacrylic acid, or alkyl acrylate, wherein the first and second copolymers have a combined weight percentage of at least 50% by weight, this weight percentage based on the total weight of the layer; (c) a third layer having at least 80% by weight (based on the weight of the third layer) of either the ethylene vinyl alcohol copolymer or at least one vinylidene chloride copolymer with 2 to 20% by weight (based on the weight of said copolymers) of vinyl chloride and / or methyl acrylate; and (d) a fourth polymeric layer having (i) from 10 to 85% of a first polymer having a melting point of 55 to 95 ° C of ethylene and an α-olefin (preferably octene-1), (ii) from 5 to 60% of a second polymer having a melting point of 115 ° C to 128 ° C of ethylene and at least one C4-C8 α-olefin, and (iii) from 0 to 50% of a third copolymer unmodified or modified with anhydride having a melting point of 60 to 110 ° C of ethylene with a vinyl ester or alkyl acrylate, wherein the combined weight percentage of the first and second copolymers is at least 50% by weight , based on the total weight of this layer; and wherein the film has a shrinkage value in the machine direction and / or in the transverse direction at 90 ° C of at least 40%, and a seal strength of at least 400 g / cm at 88 °. C. Advantageously, the process of the present invention produces films and bags, which are easy to make, while having a greater resistance to perforation, excellent high values of shrinkage a. ajas temperatures (80 ° C) and excellent optical properties compared to commercially available prior art films. For example, a process for making a shrinkable film with heat, biaxially stretched and involves the steps of: (a) extruding a melt-plated primary tube comprising, for example, 25 to 85% by weight of a first polymer having a melting point of 55 to 95 ° C comprising at least one ethylene-octene copolymer; 1; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer not modified or modified with ethylene anhydride and a vinyl ester, acrylic acid, methacrylic acid or an alkyl acrylate; wherein the first and second polymers have a combined weight percentage of at least 50% by weight, the weight percentage based on the total weight of said first, second and third polymers; (b) cooling the primary tube; (c) reheating the cooled tube to a drag point temperature of 68 to 88 ° C; biaxially stretching said tube to a circumference of at least 2 '/ 2 times the circumference of the primary tube, and (e) cooling the biaxially stretched tube to form a heat-shrunk, biaxially stretched film.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view of a ram drilling tester. Figure 2 is an exploded view of a specialty film holder. Figure 3 is a schematic view illustrating the impact geometry trigger with the film. Figure 4 is a schematic view of the film tube expansion.

Detailed Description of the Invention The film, bag, process and packaging of the present invention can be used as a heat-sealable barrier film of oxygen and moisture to carry a food product during cooking and / or packaging for sale. food product before or after a period of pasteurization or cooking. The present invention is particularly well suited for processing and packaging pasteurized foods, and has particular utility for packing cooked hams, turkey breasts and meat. "Cooking" is the term used to indicate a film or bag in which a food product is pasteurized or cooked. This film or bag is used to jointly maintain, protect and / or shape the shape of the food product through a food processor (manufacturer) during the cooking or pasteurization process, after which the film can be removed (sometimes called "separation"), or can be left as a protective barrier during shipment, and optionally left during retail sale. The benefits of the film of the invention include: a relatively low permeability to oxygen and water vapor; high resistance to delamination and unexpectedly good combinations of shrinkage capacity, seal strength, puncture resistance and optical properties especially at elevated temperatures simulating cooking conditions. The films of the invention are easily oriented and can have high shrinkage values at low temperatures (90 ° C or less); excellent resistance to degradation by acids of food, salts and fat; a sufficient force of residual shrinkage to form and maintain a compact product; a controllable adhesion of the meat; a good to excellent sealing capacity over a wide temperature range; low levels of extractable products in accordance with government food contact regulations; a low turbidity; high gloss, without imparting bad tastes or smells to the packaged food; good resistance to tension; a surface that can be printed; high seal strength at room temperature under atmospheric conditions and in contact with water at elevated temperatures for prolonged periods, for example 30 minutes at 96 ° C, and a long-life seal under especially demanding conditions, for example, at temperatures of cooking Advantageously, a preferred embodiment has low O 2 permeabilities and water vapor in combination with high meat adhesion, which prevents undesirable cooking of the liquid during processing. In an especially preferred embodiment, the film has at least 40% (preferably 45% or more) of shrinkage values in at least one direction at 90 ° C. Also, the oxygen barrier properties of the film of the invention reduce or eliminate waste losses, for example, by rancidity due to oxidation. The films and bags of the invention are particularly useful for processing and / or packaging cooked food products, but they can also be used as packages for a wide variety of food and non-food items. The invention in all its forms comprises or utilizes a monolayer or multiple layer thermoplastic polymer film of 254 microns or less. The invention can be used as bags in various typical sizes. By "flat width" is meant the transverse width of a flattened tubular film. The flat width is also equal to half the circumference of the tubular film. In certain preferred embodiments very suitable for use with cooked food or for post-cooking pasteurization processing. and packing, the inner heat sealing layer comprises a propene-based copolymer. This layer makes contact with and therefore controls the adhesion of the film to an enclosed food (referred to as, for example, "meat adhesion"), and also controls the heat seal capacity and seal resistance, particularly at temperatures elevated with time. Typical films of the invention for a variety of use can advantageously have a thickness of about 50.8 76.2 microns, although advantageously suitable film can be employed to pack food products as thick as 127-178 microns or as thin as 25.4 microns. Typically, the films will be between approximately 38.1-88.9 microns. Especially preferred for use as films to pack cooked meats are films wherein the multilayer film has a thickness of between about 50.8-76.2 microns). These films have a good resistance to abuse. Films thinner than 50.8 microns are less resistant to abuse and more difficult to handle in packaging processes. 102-178μ films have extremely good abuse resistance and puncture resistance and a surprisingly good sealing ability. Films greater than 178μ can be advantageous in some demanding applications. Preferred films are shrinkable with heat. Preferred films also provide a beneficial combination of one or more or all of the above properties and which are presented afterwards, including strong seals, puncture resistance, low breaking strength, low turbidity, high gloss, high shrinkage values at 90 ° C or less, good machinability, good mechanical strength and good barrier properties, including high oxygen barriers and water permeability. Suitable films of the present invention can have low turbidity and high glass, for example, less than 20% turbidity and a brightness greater than 50 Hunter Units (H.U.) at 45 °. Advantageously, some embodiments may have turbidity heats of less than 10-12%, and most preferably less than 6%, and very high brightness values, for example greater than 65 H.U. and preferably greater than 75 H.U.

The term "heat shrink layer" represents a layer which is heat shrinkable, preferably to itself, ie capable of fusion bonding through conventional indirect heating means, which generate sufficient heat on at least one surface of film contact for conduction to the adjoining film contact surface and the formation of an adjoining bond between them without loss of film integrity. Advantageously, the abutting junction surface must be sufficient and thermally stable to prevent the leakage of gas or liquid therethrough when exposed to temperatures above or below ambient during food processing inside the tube when it is sealed at both ends, that is, in the form of a bag. Finally, the abutting junction surface between the contiguous inner layers must have sufficient physical strength to withstand the stress that results from stretching or shrinkage due to the sealed food body within the tube. Various copolymers of ethylene and at least one alpha olefin are used in the invention. The term "ethylene copolymer" means that the copolymer is composed predominantly of ethylene and that at least 50% by weight of the copolymer is derived from ethylene monomer units. Suitable alpha olefins include C3 to C10 alpha-olefins such as propene, butene-1, pentene-1, hexene-1, methylpentene-1. octene-1, decene-1 and combinations thereof. The invention contemplates the use not only of bipolymers, but also of copolymers of multiple monomers such as terpolymers, for example, ethylene-butene-1-hexene-1-terpolymer terpolymer, ethylene-butene-1-octene-1 or terpolymer of ethylene-hexene-1-ketene-1. Terpolymer means 3 or more copolymerized monomers. The ethylene α-olefin copolymers (EAOs) used can have various molecular weights, molecular weight distributions (Mw / Mn) and melt indexes. The first and second polymers used, ie, the ethylene-octene copolymer and the ethylene α-olefin copolymers will have a melt index of less than 2.5 dg / min. (ASTM D-1238, condition E 190 ° C), preferably 1.5 dg / min or less, most preferably 0.3 to 1.0 dg / min. Some embodiments of the invention may use a first polymer having a melt index of 0.3 to 1.5 dg / min, while other embodiments may utilize first polymers having a melt index of 1.5 to 3.0 dg.min or more. Advantageously, the first polymer can also have an Mw / Mn of 1.5 to 3.0, preferably 2.2 to 2.7, but polymers of higher or lower ratio can be used. The invention in a very preferred embodiment uses at least three different polymers. These polymers are defined in part by their melting point. The term "melting point" means the peak melting temperature of the dominant melting phase as measured by Differential Scanning Calorimetry (DSC) with a heating rate of 10 ° C / min, according to ASTM D-3418. Two of the polymers required of the mixture of the preferred invention are ethylene α-olefin copolymers and one is a copolymer of ethylene with vinyl ester, acrylic acid, methacrylic acid or an alkyl acrylate. Either or these three polymers can be grafted with portions of anhydride or can be released from said grafts, i.e., unmodified. Unless otherwise indicated herein, the polymers are unmodified. It is preferred that the three polymers required of the named embodiment be present in an amount of at least 10% by weight in each mixture, and that the blend comprises at least 50% by weight of at least one layer. When the interpolymers are specified, the interpolymer has at least two distinct melting points, which have a separation of at least 5 ° C and an individual interpolymer it can comprise two or more of the required polymers. By "interpolymer" is meant a polymer mixture that has been formed in situ by an individual polymerization reactor using catalysts and / or process conditions or by sequential reactors using different catalysts and / or process conditions. It is believed that the heat sealing scale is improved by selecting different polymers having melting points that are at least 5-10 ° C to provide melting characteristics over a wide temperature range leading to a wide range of sealing per heat and properties improvements. The first and third polymers have peak melting points that are at least 5 to 17 ° C of the second polymer.

The first polymer of the film blend of the invention has a melting point of 55 to 95 ° C, preferably 80 to 85 ° C and comprises an ethylene-octene-1 copolymer. The first suitable, illustrative polymers can have a density of 0.900 g / cm3 or less, a melt index of about 2.5 or less, preferably 1.5 dg / min or less, and most preferably 0.3 to 1.0, as measured by ASTM D-1238, at 190 ° C under a total load of 2.16 kg (condition E), an Mw / Mn of 3 or less, preferably from 1.5 to 3.0 and most preferably from 2.2 to 2.6. in a preferred embodiment, the first polymer will advantageously have a melt index of less than 1.0 dg / min. For the present invention, it is preferred that the first polymer comprises an ethylene and an octene-1 having a melt index (M.I.) of about 0.3 and 1 (most preferably less than 1.0) dg / min. A commercially available first preferred polymer is sold under the trademark of AFFINITY VP 8770. AFFINITY is a trademark of The Dow Chemical Company, Midland, Michigan, USA, for its ethylene α-olefin polymers produced using single-catalysts. metallocene site. These resins typically have a low level of crystallinity; 10-15% is typical. The first polymer may comprise at least 10%, and preferably 20, and most preferably from 25 to 85% by weight of the total weight of the first, second and third polymer components in the layer comprising the preferred mixture, and preferably of the total polymer content of the layer. The use of smaller amounts reduces the shrinkage capacity in those embodiments where the heat shrink capacity is desired. Higher amounts make the orientation more difficult and can increase the extrapy portions to amounts that are undesirable for certain food contact applications. Various embodiments use the first polymer in an amount of 25 to 45% by weight or 30 to 40% by weight, or 45 to 85% by weight based on the total weight of the first, second or third polymers in the layer . When an optional four polymer component mixture is used, the first polymer will preferably be present in an amount of about 20 to 35% based on the weight of the ca comprising the mixture. The second polymer of the mixture of the invention has a melting point of 115 to 128 ° C and comprises a copolymer of ethylene and at least one alpha olefin. Examples of suitable second copolymers include copolymers of ethylene and at least one C3 to C10 alpha olefin, such as copolymers of C2C4, C2C6, C2C8 and C2C4C6, for example, copolymer of ethylene octene-1, copolymer of ethylene hexene-1, ethylene octene-1 copolymer and ethylene butene-1 hexene-1 copolymer. The second illustrative polymers can have a density of 0.900 g / cm3 and more, preferably 0.900 to 0.915 g / cm3; a melt index preferably of 2.5 dg / min or less, most preferably 0.5-1.0 dg / min; and an Mw / Mn preferably of about 4.0 to 5.0.

The second preferred copolymers include ATTANE ™ XU 61509.32, and XU 65120.01. ATTANE ™ is a trademark of Dow Chemical Co. of Midland, Michigan, E.U.A. for its ethylene polymers ULDPE (VLDPE). It is preferred that the second polymer of the film of the The invention comprises an ethylene copolymer having a melt index (Ml) of about 0.25 and 2.5 (most preferably 0.7 to 1.5) dg / min, as measured by ASTM D-1238 at 190 ° C under a total load. of 2.16 kg (condition E). The second polymer may comprise at least 5%, preferably from 5 to 35% by weight of the total weight of the first, second and third polymer components, and preferably of the total polymer content of the film layer. The use of smaller quantities reduces the scale of heat sealing temperature. When a mixture of four components is used, the second polymer will preferably be present in an amount of 15 to 30%, most preferably greater than 20%, based on the total weight of the layer comprising the mixture of four polymers.

The third polymer of the mixture of the preferred invention has a melting point of 60 to 110 ° C and comprises a copolymer of ethylene and a vinyl ester, acrylic acid, methacrylic acid, or an alkyl acrylate. Preferred third copolymers include ethylene copolymers and unsaturated esters having adhesive and / or heat sealing properties. Said copolymers are predominantly ethylene (< 50% by weight). Suitable copolymers include ethylene vinyl esters, ethylene acrylic acid copolymers, ethylene-methacrylic acid copolymers and ethylene-alkyl acrylates such as ethylene vinyl acetate (EVA), ethylene-acrylic acid acrylic copolymer, ethylene-methacrylic acid, ethylene vinyl propionate, ethylene-methyl methacrylate, ethylene-ethyl methacrylate, ethylene-ethyl acrylate and ethylene-n-butyl acrylate. Preferred copolymers are ethylene vinyl esters such as EVA, ethylene vinyl formate, ethylene vinyl propionate, and ethylene vinyl butylate. Especially preferred is EVA. Many different EVA resins are commercially available having a wide variety of vinyl acetate contents and melt flow rates. Suitable contents of vinyl ester or alkyl acrylate of the preferred third polymer components used include 4-28% (preferably 4-18) by weight of vinyl ester or alkyl acrylate based on the total weight of the copolymer. It is preferred that the third polymer comprises a copolymer of ethylene and a vinyl ester having a melt index (Ml) of 0.1 to 2 (most preferably 0.1 to 0.5) dg / min, as measured by ASTM D-1238 to 190 ° C under a total load of 2.16 kg (condition E).

A highly preferred EVA sold as ESCORENE ™ 701 by Exxon Chemical Company of Houston, Texas has a density of 0. 93 g / cm 3, a vinyl acetate content of 10.5% by weight, a melt index of approximately 0.19 dg / min, and a melting point of approximately 97 ° C.

The third polymer may comprise at least 10%, preferably from 10 to 50% by weight of the total weight of the first, second and third polymer components, and preferably of the total polymer content of the film layer mixture. The use of lower quantities reduces the properties of heat sealing (in those embodiments where the mixture is used as the heat sealing surface layer and the heat sealing capacity is desired) and the use of higher amounts reduces the puncture resistance and undesirably can reduce the optical properties. When an optional four component mixture is used, the third polymer will be present in an amount of 10 to 30% based on the weight of the layer comprising the mixture. The fourth optional polymer is a thermoplastic polymer, preferably a copolymer of ethylene and at least one alpha olefin. Examples of the fourth suitable optional polymer include copolymers of ethylene and at least one C3 to C10 alpha olefin, such as copolymers of C2C4, C2C6, C2C8 and C2C4C6, for example, ethylene butene-1 copolymer, ethylene hexene-1 copolymer ethylene octene-1 copolymer and ethylene butene-1 hexene-1 copolymer; VLDPE; LLDPE; LDPE; HDPE; and propylene copolymers (ie, copolymers having at least 50% by weight of propylene units). The fourth illustrative suitable polymers may have a density of at least 0.900 g / cm3, preferably from 0.900 to 0.930 g / cm3, most preferably from 0.900 to 0.915 g / cm3; a melt index of 2.5 dg / min or less, preferably 1.0 dg / min or less, and a ratio of Mw / Mn of 1.5 to 12 or more. Suitable fourth polymers that can be used in the heat sealing layer of the films of the present invention include AFFINITY ™ PL 1840, PL 1880, Exceed ™ 350D60 and Exact ™ 3032. AFFINITY ™ is a trademark of Dow Chemical Co. of Midland, Michigan, USA, for their ethylene polymers produced using restricted geometry catalysts. Exact ™ and Exceed ™ are trademarks of Exxon Chemical Co. of Houston, Texas, E.U.A. for some of its polymers produced by a metallocene catalyst. Preferably, the fourth polymer, when present, comprises from about 0 to 30% by weight of the total weight of the four polymer components, and preferably of the total polymer content of the polymer blend. The melt indexes reported above for the various resins used as the first, second, third and fourth polymer are initial melt index values for pelletized resins as received by the manufacturer. Such "as received" values are intended when the term "melt index" is used herein, unless otherwise indicated. Entanglement, especially irradiation entanglement, is known to increase the average molecular weight through the formation of longer chains of molecules than those originally present. Therefore, the entanglement will also reduce the melt index of a polymer from its initial value to a lower value, since the melt index is not only a measure of viscosity but is also an indirect measure of molecular weight. Also, the molten mixed material will have its own melt index, which should not be confused with that of the original copolymer components of the blend. The custom of the industry is that the term, melt index, refers to the resin (usually in pellet or powder form) as received from the polymer manufacturer, unless otherwise indicated. Advantageously, the invention uses a polymer blend material in at least one layer, which has unexpected and surprising combinations of properties. Beneficially, said polymic material can provide a broad combination of desirable properties with important commercial advantages for the production and use of thermoplastic films, in particular biaxially stretched films with properties of heat shrinkability at 90 ° C. Advantageously, said films have an excellent puncture resistance, a moderate resistance to the propagation of rupture, a high capacity of shrinkage, high tensile strengths, a good modulus, a low turbidity, a high gloss, excellent optical properties, a Wide sealing scale and good seal strength. Beneficially, combinations of these desirable attributes are present in various embodiments of the invention. The mixture has a sufficient film strength to resist orientation (especially a biaxial double tubular bubble type orientation process). The mixture also resists "burning" during heat sealing operations and produces strong fusion bonds. Said polymer blend films provide a material having suitable chain lengths for diffusion and entanglement between the adjacent layers during heat sealing operations to form strong integral melt bonds. In one embodiment, the invention comprises a polymer blend of at least three copolymers comprising: (a) from 25 to 85% by weight of a first polymer having a melting point of 55 to 95 ° C comprising minus one copolymer of ejylene and octene-1; (b) from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and (c) from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer of ethylene and a vinyl ester, acrylic acid, methacrylic acid, or an acrylate of I rent; wherein the first and second polymers have a combined weight percentage of at least 50% by weight, the weight percentage based on the total weight of said first, second and third polymers. Various embodiments of the mixtures of the invention use from 25 to 45% by weight or from 30 to 40% by weight of the first polymer. These mixtures are capable of producing films with very good properties of resistance to rupture. Other embodiments of the mixture of the invention use from 45 to 85% by weight of the first polymer. These embodiments are capable of producing films having exceptionally high puncture resistance values, especially high maximum puncture forces and total energy absorption values. Advantageously, one or more of the first, second and third polymers may comprise an interpolymer. In particular, an ether polymer of the first and second polymers can be used. This interpolymer, which combines the first and second polymers could have at least two melting points, n, a melting point of 55 to 95 ° C and a second melting point of 115 to 128 ° C. The mixture may contain other components, for example, other polymer and / or processing aids. Preferably, the mixture of the first, second and third polymers will comprise at least 50% by weight of a total mixture of which it is a part. In this manner, a layer of film comprising the mixture of the invention will advantageously have at least 50% by weight of the composite layer of the aforementioned first, second and third polymers, although several embodiments may use less than 50%. In another embodiment, the above mixture is. used to produce flexible films, which can be, for example, blown, cast, stretched or stretched, either uniaxially or biaxially. These films can be manufactured as bags or purse like tubes. The film layer of the invention can be interlaced by irradiation by known methods. It can also be the innermost heat sealable layer of a tubular film. Still another embodiment uses the above mixture to produce flexible, thermoplastic, biaxially stretched, heat shrinkable films. These heat-shrinkable films can beneficially have a ram piercing force of at least 65, preferably at least 70 Newtons, a ram drilling voltage of at least 100 MPa, a total energy absorption of at least 0.60 Joules , preferably at least 0.780 Joules, and preferably at least 0.90 Joules, and / or an "X" breaking strength such as 10 < x < 50 grams per thousand., In each of the directions of both the machine and transversal or x < 40 grams per thousand., In at least one of the directions of both the machine and transverse (as measured by the Elmendorf Rupture Resistance Test). In another embodiment, a film is made having at least one layer comprising the blend of the invention having at least one thermoplastic layer, and in a preferred embodiment having at least three or four additional layers. These additional layers can be added in sheet or tubular form and can be produced through multi-layer manufacturing techniques including coating lamination or coextrusion. In one embodiment, at least one additional layer comprises a polymer blend of at least three copolymers having an ethylene α-olefin copolymer (EAO) "A" having a melting point of between 55 to 75 ° C; an EAO "B" having a melting point between 85 to 110 ° C; and a thermoplastic polymer, for example, EVA, having a melting point of between 115 to 130 ° C. The additional layer is further described in PCT Application No. US 98/03914, entitled "Thermoplastic C2-a-Olefin Copolymer Blends and Films" (Mixtures and Films of α-Olefin Copolymer of C2 Thermoplastic), filed on 27 February 1998, claiming priority with Series No. 08 / 808,093, filed on February 28, 1997, now US patent No. 5,928,740, said applications and descriptions are incorporated herein by reference in their entirety. The mixture of the invention will find utility as a very internal heat sealing layer of a tubular film in many multilayer embodiments. Films are contemplated having 3 to 5 or more layers with at least one layer comprising the mixture, especially films having a layer comprising at least 50% by weight of the copolymer of ethylene with at least one alpha-olefin or at least one vinyl ester or mixtures thereof, and / or a layer comprising a copolymer of vinylidene chloride, a nylon or a copolymer of ethylene with a vinyl alcohol. In a preferred embodiment of three, four or five layers, an oxygen barrier layer of a vinylidene chloride copolymer, a nylon or a copolymer of ethylene with a vinyl alcohol is between the layer of the invention and either a layer comprising at least 50% by weight of the copolymer of ethylene with at least one alpha-olefin or at least one vinyl ester or mixtures thereof, or another layer comprising the mixture of the invention. Films having exceptionally high puncture resistance values, especially high maximum puncture forces and total energy absorption values, can be produced according to the present invention. With the films of the invention, maximum arched drilling forces of at least 65 to 70 to 90 to 100 Newtons or higher, preferably of at least 110 Newtons, can be obtained. Films of the invention can be obtained with maximum water-drilling tension values of at least 110 MPa, preferably at least 140 MPa, and most preferably at least 200 MPa. Also, films of the invention having total energy absorption values (at a maximum piercing force) of "at least 0.50 Joules, preferably at least 0.60, most preferably at least 0.70 or at least 0.80 Joules, beneficially at least 0.90 Joules, and most preferably at 1.0 Joules, are polymers of broad molecular weight or polymodal in molecular weight distribution, since they are mixtures having very narrow molecular weight distributions. of the present invention is that the use of the currently described mixtures facilitates a wide scale of heat sealing and improves the bio-orientation ability for the irradiated films.After exposure to sufficient irradiation to cause entanglement, the sealable layers with heat they tend to decrease in their heat sealing ability, however, an antioxidant can be added to the layer heat sealable inner of the tubular article to inhibit entanglement within the polymer, thus reducing the adverse effects of over-irradiation on the heat sealing properties. The addition of an antioxidant further allows an irradiation dose to be sufficiently high for other layers of a multilayer film to retain the beneficial effects of irradiation. The films can be entangled through chemical agents or through irradiation, preferably at a level between 1 and 10 Mrad, most preferably 2-6 Mrad. As generally recognized in the art, the properties of the resin can be modified by mixing resins or additional additives such as colorants, processing aids, anti-blocking agents and slip agents, etc. The specific polymer blends described above can also be mixed with additional resins such as very low density polyethylene (VLDPE), linear low density polyethylene (LLDPE), low density polyethylene (LDPE), high density polyethylene (HDPE), Onomers. polyamides, polypropylenes, ethylene acrylates or esters, various olefinic polymers or copolymers, adhesive resins; or they can be formed into multi-layer films with one or more additional layers of said resins or mixtures thereof. The resins and others can be mixed by well known methods using mixers or mixers. Also, if desired, well-known additives such as processing aids, slip agents, antiblocking agents, pigments, and mixtures thereof, can be incorporated into the film in any or all layers. In one embodiment of the present invention there is provided a polymeric film, which comprises a mixture of: (a) a first polymer having a melting point of 55 to 95 ° C, preferably 80 to 85 ° C, which comprises a copolymer of ethylene and octene-1; 15 (b) a second polymer having a melting point of 115 to 128 ° C, which comprises an ethylene copolymer and at least one olefin; and (c) a third polymer having a melting point of 60 to 110 ° C, which comprises a copolymer of ethylene and a vinyl ester (preferably from 4 to 18% by weight of said copolymer), acrylic acid (preferably from 4 to 30% by weight of said copolymer), methacrylic acid or an alkyl acrylate; and when the first polymer has a melting point greater than 92 ° C, the mixture may otherwise: i) be free of α-olefin copolymers having a __; > melting point lower than 90 ° C or from 55 to approximately 85 ° C; ii) having less than 30% by weight of ethylene α-olefin copolymers having a melting point of less than 90 ° C or of 55 to about 85 ° C; iii) having more than 50% ethylene α-olefin copolymers having a melting point of less than 90 ° C or of 55 to about 85 ° C; or iv) having from 30% to 50% of ethylene α-olefin copolymers having a melting point lower than 90 ° C or from 55 to approximately 85 ° C, based on the total weight of the blend layer. In a preferred process for making films, the resins and any of the additives are introduced into an extruder (generally an extruder by layer), where the resins are plasticized under melting heating and then transferred to an extrusion die (or co-extrusion) for the formation to a tube. Extruder and die temperatures will generally vary depending on the particular resin or resin containing mixtures that are processed and suitable temperature scales for commercially available resins are generally known in the art, or are provided in technical bulletins available from the manufacturers of the resin. Processing temperatures may vary depending on other process parameters chosen. For example, in accordance with the present invention, in the extrusion or coextrusion of the polymer blends of the invention, the barrel and die temperatures may vary from about 140 ° C to 185 ° C. However, variations are expected, which may depend on factors such as variation in the selection of the polymer resin, the use of other resins, for example, in the mixture or in separate layers in a multilayer film, the manufacturing process used, and the particular equipment and other parameters of. process used. Current process parameters including process temperatures are expected to be set by one skilled in the art without undue experimentation in view of the present disclosure. The blends of the present invention can be made into various useful articles, for example, cast films, using for example a slot die followed by laying to achieve biaxial orientation, or tubular films using an annular die followed by bubble expansion. trapped to achieve the bjaxial stretch. In a preferred embodiment, extrusion is used through a trapped bubble or double bubble process of the type described in the U.S.A. 3,456,044. in a preferred process for making a film oriented or shrinkable with heat. A primary tube comprising the plastic mixture of the invention is extruded, and after exiting the die is inflated through the addition of air, cooled and crushed, and then preferably oriented by re-inflating to form a secondary bubble with reheating to the Orientation temperature scale (extraction) of the film. The direction of the machine direction (MD) is produced by pulling or pulling out the film tube, for example, using a pair of rollers traveling at different speeds, and the transverse direction orientation (TD) is obtained through expansion of radial bubble. The oriented film is fixed through rapid cooling. Advantageously, the stretching ratios of the machine direction and the transverse direction are from about 3: 1 to about 5: 1, with a preferred ratio of about 4: 1. Films of various embodiments of the present invention may have shrinkage values at 90 ° C of up to 45% or more in either or both directions, of the machine and transversal. Some preferred films have shrinkage values of at least 45% at 90 ° C. The films of the present invention may be monolayer or multilayer films of 254 microns or less, most preferably, of 127 microns or less. Multilayer films have the following preferred layer thicknesses. The thickness of the first heat-sealable internal thermoplastic layer is typically about 5-51 μ. Thinner layers can perform the functions described above, in particular in structures of 5 or more layers. In gas barrier films (generally providing a barrier to oxygen transmission), the thickness of the barrier layer is preferably 2.5-12.7 μ. The thinner barrier layers can not perform the intended functions and the thicker layers appreciably do not improve the operation. As used herein, the term "barrier layer" means "an oxygen gas barrier layer", unless otherwise indicated.

In a barrier layer embodiment of this invention, the external thermoplastic layer of the enclosed multilayer film is on the opposite side of the core layer from the inner layer, and in direct contact with the environment. In a preferred three layer embodiment, this outer layer is directly adhered to the core layer. Since it is seen by the user / consumer, it must improve the optical properties of the film. Also, it must resist contact with sharp objects and provide resistance to abrasion that is usually referred to as the abuse layer. The outer layer is preferably formed of a mixture similar to that of the inner layer, so that both layers use the first, second and third polymers defined above, preferably a mixture of: (i) EVA; (ii) EAO (such as VLDPE); and (iii) an ethylene-octene-1 copolymer having a melting point of 55 to 95 ° C, preferably 80 to 85 ° C. The three polymers each typically comprise from 20 to 40% by weight of the layer. EVA when used in the outer layer, preferably has between about 3% by weight and about 18% by weight of vinyl acetate content to provide good shrinkability. EAO mixtures are also usefully employed in the outer layer. Alternatively, the inner, outer or intermediate layers can be formed of other thermoplastic materials, for example, polyamides, styrenic copolymers, for example, styrene-butadiene copolymer, polypropylenes, ethylene-propylene copolymers, onomers, or alpha-polymers. olefin and in particular members of the polyethylene family such as linear low density polyethylene (LLDPE), very low density polyethylene (VLDPE and ULDPE), HDPE, LDPE, ethylene-vinyl ester copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer or ethylene-alkyl acrylate copolymer or various mixtures of two or more of these materials. The thickness of the thermoplastic outer layer is typically 12.7 to 25.4 microns. Thinner layers may be less effective for abuse resistance, however, thicker layers, although more expensive, may be advantageously used to produce having unique properties of puncture resistance and / or abuse resistance, desirably high Films with heavy gauges, typically from 127 to 177.8 microns or more, are necessary in demanding applications, which are usually satisfied by very expensive and complex laminated film structures and / or secondary packaging materials such as bone protectors, pads and overwrap Unless otherwise indicated, the following physical properties are used to describe the present invention films and seals. These properties are measured either through the test procedures described below or tests similar to the following methods. Average Caliber: ASTM D-2103 Tensile Strength: ASTM D-882, Method A 1% Secant Module: ASTM D-882, Method A Gas Oxygen Transmission Rate (O2GTR): ASTM D-3985-81 Resistance to Elmendorf Rupture: ASTM D-1922 Rupture Elongation Percentage: ASTM D-882, Method A Molecular Weight Distribution: Gel Penetration Chromatography Gloss: ASTM D-2457, 45 ° angle Turbidity: ASTM D-1003-52 Melt index: ASTM D-1238, Condition E (190 ° C) (except for propene-based polymers (> 50% content of C3) tested to Condition L (230 ° C)). Fusion Point: ASTM D-3418, p.f. peak determined by DSC with a heating rate of 10 ° C / minute. Vicat Softening Point (Vsp): ASTM D-1525-82 All of the ASTM test methods noted herein are incorporated herein by reference.

Shrinkage values: shrinkage values are obtained by measuring the unrestricted shrinkage of a 10 cm2 sample submerged in water at 90 ° C (or the indicated temperature), it is different) for ten seconds. Four test specimens are cut from a given sample of the film to be tested. The specimens are cut to a length of 10 cm in the direction of the machine and a length of 10 cm in the transverse direction. Each specimen is completely immersed for 10 seconds in a water bath at 90 ° C (or the indicated temperature, if different). The specimen is then removed from the bath and the distance between the ends of the shrunk specimen is measured both in the machine direction and in the transverse direction. The difference in distance measured for the shrunken specimen and the original 10 cm side is multiplied by ten to obtain the shrinkage percentage for the specimen in each direction. The shrinkage of 4 specimens is averaged and the average shrinkage values in the machine direction and cross direction are reported. The term "shrinkable film with 90 ° C heat" represents a film having an unrestricted shrinkage value of at least 10% in at least one direction at 90 ° C.

Shrinkage Strength: The shrinkage force of a film is that force or tension required to prevent shrinkage of the film and was determined from two samples taken from each film. Each film sample was cut to a width of 2.54 cm by a length of 17.8 cm in the machine direction and to a width of 2.54 cm by a length of 17.8 cm in the transverse direction. The average thickness of the film was determined and recorded. Then each film sample was secured between the two fasteners separated at 10 cm. One fastener is in a fixed position and the other is connected to a voltage indicator transducer. The secured film sample and the fasteners are then immersed in a bath of silicone oil held at an elevated temperature, constant 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 per l, which also recorded the force in grams at room temperature. The shrink force for the film sample was then determined from the following equation, where the results are obtained in grams per thousand. Film thickness (g / mil): Shrinkage Strength (g / thousand) = F / T Where F is the force in grams and T is the average thickness of the number of samples in millimicrons.

Impulse Seal Scale: Impulse Seal Scale Test determines acceptable voltage ranges for plastic impulse seal films. A Sentinel Model 12-12AS laboratory sealer manufactured by Packing Industries Group, Inc., Hyannis Massachusetts, E.U.A. The impulse sealer is equipped with a replacement sealing strip (available from Koch Supplies of Kansas City, Missouri) for a Multivac AG100 packaging machine. in this test two samples with a width of 10.16 cm (transverse direction) of a tubular film were cut. The impulse sealer has controls for coolant flow, impulse voltage and time, and seal bar pressure. These controls, except for the impulse voltage, are set to the following conditions: 0.5 pulse time, seconds (only on the top rail) 2.2 cooling time, 50 seconds jaw pressure, 345 kPa 0.3 1 liter per minute flow of cooling water (22 ° C) One of the samples was bent in half for use in determining a minimum sealing voltage. This fold simulates a fold, which can occur inadvertently during conventional bag sealing operations. The bent sample, which now has four sheets or portions of film (hereinafter referred to as "sheet portions") is placed in the sealant and through a trial and error analysis the minimum voltage to seal the bottom was determined of the two sheet portions together. The maximum voltage was determined through 2 pieces of sheet placed in the sealer and activating the seal bar. The film sample is manually pulled with a force of approximately 0.227 kilograms and the voltage is determined, which does not cause burning or significant deformation of the seal.

Hot Water Seal Resistance Test (HWSS): In commercial use, food packaging bags are filled with food products, for example, poultry, then evacuated through the mouth end of the bag and sealed, for example through an impulse sealing machine. The resistance of heat shrinkable bag seals is measured by determining the time for a seal to fail, when, under certain circumstances, the seal is submerged in hot water, for example at 95 ° C. The HWSS test is designed to test the integrity of the seal of a bag seal by simulating an application of shrinking and / or cooking of food in a bag. The seal resistance with hot water is measured through the test described as the "seal resistance test to restricted shrinkage" in the patent of E.U.A. No. 3,900,635 to Funderburk et al., Which is incorporated herein by reference. The seal strength of the sealed test bags is determined using a metal frame fabricated from wire to simulate the contours of a bulky food such as an entire bird, and the frame is placed inside the test bag. The bag is thus opened and the test frame is then immersed in water at 95 ° C + .0.5 ° C, with the seal at the bottom end, and the seal failure time is measured for ten bags and the average is reported along with the minimum and maximum time of the failure. The times are measured in seconds up to a maximum of 300 seconds. After 300 seconds, the test of each sample is discontinued, without considering the failure and the averages were calculated using 300 seconds for intact bags. The maximum and minimum sealing temperatures, for which the bags can be effectively sealed, were determined through trial and error to provide information regarding the sealing scale on which the test bags can be sealed. A wide sealing scale is desired to minimize operator error and seal failure due to, for example, displacement of temperature control and environmental conditions and other process variations, such as film thickness.

Tension Seal Strength Test (Seal Resistance): Five identical film samples with a width of 2.54 cm and a length of at least 77 cm were cut with a seal portion with a width of 2.54 cm centrally and transversely arranged. Opposite end portions of a film sample were secured in opposite fasteners in a temperature controlled chamber of an Instron 4501 universal test instrument. The film was secured in a tight forced fit between the fasteners with stretch before beginning the test. The door of the test chamber was closed and the chamber was heated to the test temperature at the time the instrument was activated to pull the film through the fasteners transverse to the seal at a uniform speed of 127 cm per minute until the failure of the film (breaking of the film or seal, or delamination and loss of the integrity of the film). The breaking force in kilograms was measured and recorded the test temperature. The test was repeated for four additional samples and the average kilograms were reported at break.

Hot Water Drilling Test: Hot water drilling values were obtained through a hot water drilling test as follows. The water was heated to 95 +1 ° C. A straight stainless steel bar with a diameter of 0.95 cm was formed to a probe by forming one end to a conical point. This sharp point has the configuration of a straight circular cone, and the angle between the axis of the cone and an element of the conical surface at the apex is 37 °. This sharp point was then rounded to a spherical point with a diameter of approximately 0.15875 cm. The pointed bar is attached to a block of wood, so that the rounded point projects 3.8 cm beyond the end of the rectangular wooden block with a length of 17.8 cm. A specimen with a width of approximately 7.6 cm in the transverse direction and a length of approximately 45.7 cm was cut from the test sample material. One end of the specimen was placed on the end of the block of wood opposite the pointed bar. The specimen wrapped around the end of the sharp bar and back to the block of wood on the opposite side, where it was secured. The thickness of the film in the area of contact with the sharp bar was measured in order to ensure that the thickness of the film specimen is in fact representative of the given test sample material. The specimen and the pointed bar were quickly submerged to 12.7 cm in the hot water and a chronometer was activated. The stopwatch stopped when the point pierced the film specimen or at 120 seconds without perforation, and time was recorded. The test procedure was repeated 5 times more with new specimens. The times required for penetration were then averaged for the six specimens in the transverse direction. Resistance to drilling times below 6-7 seconds is generally considered unacceptable, while times of 20 seconds or more are good, 60 seconds or more are very good and 120 seconds or more are excellent.

Water Drilling Test: The water hammer test was used to determine the maximum drilling load or force, and the maximum drilling tension of a flexible film, when struck with a hemispherically configured beating device. This test provides a quantitative measurement of the puncture resistance of thin plastic films. The values of this test will differ from those generated by a dynamic drilling test due to differences in the geometry of the striking apparatus, regime and charge geometry available energy. Referring to Fig. 1, a schematic drawing (not to scale) of a ram drilling tester 10 is illustrated, having a base 11 and a ledge 12 spaced apart by fixed abutments 13 forming a sample placement area 14. When driving the water hammer test, a film sample with a diameter of approximately 12.7 cm was obtained and its thickness was measured and recorded. This sample was held in place through a circular opening with a diameter of approximately 7.6 cm in a ring fitting 15 holding, in a taut manner, the film sample, but not stretched, between the circular ring attachment 15 having an O-shaped compressor ring and an opposing metal ring to secure the film in a circle. This accessory 15 is positioned to maintain the plane of the film perpendicular to the trajectory of the striker apparatus 16 located above the film. The striker apparatus 16 travels downward in the direction of and under the influence of the gravitational force of the Earth. The striker apparatus 16 has a steel ball 17 with a diameter of 3.95 mm welded to a steel arrow 18 with a length of 5 cm with a diameter of 0.24 cm. The arrow is attached to a piezoelectric load cell, Dytran ™, 22.7 kg full scale (available from Dytran Instruments, Inc., USA), which is fixed to an aluminum head 20. The interlaced assembly forms a mass of 3.00 kg, which travels vertically, under the influence of gravity, along two hardened steel guide shafts 21, which are held in a separate parallel position fixed through the joint to the shelf 12 in the lower plate and upper 22 at the top. The rear pillars 23 provide stability to the tester 10. Four linear bearings are compressively clamped on the head to provide a precise, repeatable, low friction path along the guide arrows 21 downwardly to collide with the absorber pads 24. The striker apparatus 16 can be operated by a lock release knob 25, and the load cell information is passed through the line 26 to a low impedance voltage mode (LIVM) (power supply not shown) , which is connected to a data acquisition system in a computer 27 having a monitor 28. The shelf 12 has a circular opening 29 that allows the striker apparatus 16 to make contact with the film sample contained in the accessory 15. Making Refer now to Figure 2, the films are tested by holding them circumferentially over a 7.62 cm diameter hole using a sopor fitting the specialty film 15. The film holder 15 is an aluminum tube 30 having a circular opening 31. the tube 30 has a circular machined slot 32 for accepting an O-shaped rubber ring 33 at one end. The film (not shown) is placed through the O-shaped ring 33 and a matching cylindrical upper section 34 having an opening 35 is firmly held without stretching against the film through fasteners (not shown). The attached film is then centered below the drill point at the base of the drop tower (see Figure 1). This places the plane of the film surface 28.4 cm below the tip 17 of the hemispherical striking apparatus (height of fall). The head 20 is released and driven by gravity towards the film fastened at a speed, V0, which is kinematically related to the height of fall. Referring now to Figure 3, when the arrow 18 of the striker apparatus pulls the tip 17 of the striker apparatus into contact with the film, the film deforms from the AA plane and resists the impact force through uniform multidirectional tensions. through the thickness of the film. The angle of deflection of the film, teta (?) Is defined by the angle between the film held in the clamping position (plane AA) and that of the stretched film (indicated as position BB) to the peak drilling load during the impact. This angle is always less than 90 °. It is automatically measured and registered by a computer data acquisition system (see Figure 1). The load cell force output is recorded at a frequency of 300 kHz, starting scarcely at 1 msec before impact and as the striking device impacts, penetrates and punctures the film sample. Assuming that the membrane tensions are in the plane of the film (without bending stresses), and that the measured load depends on the geometry of the beating device, then the maximum voltage s can be determined through the following equation: smax = Pmax / (2prT without?), Where Pma = maximum force or load; r = radius of the circle circumscribed by the circular cross section of the hemispherical striker apparatus as it is superimposed on the plane of the film; T = non-deformed film thickness; without ? is the sine of the angle between the plane of the sample holder and the film sample fully flexed at the time of perforation. The Total Energy Absorption "E" can be calculated by integrating the load displacement curve according to the following equation: where E is the total energy; v0 is the speed of the striking device at the moment of impact with the film sample; P is strength; t is the time from the impact of the striking device to the perforation of the film; g is the gravitational acceleration, and m is the mass of the head including the striking device. The test was repeated and an arithmetic mean was reported for 4 samples. If necessary, the dimensions of equipment such as the height of fall, the length of the arrow of the striking apparatus and / or the mass of the head assembly can be increased to test films that are resistant to perforation with the test apparatus sized . The above equations remain equal. 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 the U.S.A. No. 3,456,044 (Pahlke), which describes a type of coextrusion of a double bubble method and in addition according to the detailed description above. In the following examples, all the layers were extruded (co-extruded in the multilayer examples) as a primary tube, which was cooled after leaving the die, for example, by spraying with running water. This primary tube was then reheated through radiant heaters (although in the present invention alternative heating means such as conduction heating or convection can be used) with additional heating at the extraction temperature (orientation) for the biaxial orientation achieved by a air cushion, which itself was heated through a transverse flow by a hot porous tube concentrically placed around the primary tube in motion. The cooling was achieved through a concentric air ring. The drag point temperature, bubble heating and cooling rates and orientation ratios were generally adjusted to maximize bubble stability and production for the desired amount of stretch or orientation. The use of higher production speeds and lower dropping point temperatures is believed to provide films that have a higher puncture resistance in relation to the use of lower yields or higher orientation temperatures. All percentages are by weight, unless otherwise indicated.

EXAMPLES 1-7 In Examples 2, 3 and 5-7, heat shrinkable biaxially stretched monolayer films of the present invention were made and their physical properties were tested. Examples 1 and 4 are comparative examples of a biaxially stretched, heat shrinkable monolayer film of the present invention. For Comparative Example 1, the thermoplastic resins, generally in the form of pellets, were mixed together to form a mixture of: 35.0% by weight of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.902 g / cm3, and a melt index of 1.0 dg / min, a melting point of 100 ° C, which is available under the trademark Affinity PL1880 from Dow Chemical Company of Midland, Michigan, USA; a second polymer comprising 25.0% by weight of a very low density polyethylene ethylene-α-olefin copolymer sold by Dow Chemical Company of Midland, Michigan, USA, under the trademark of Attane XU 61509.32, which is a copolymer of ethylene and octene-1 having a melting index of approximately 0.5 dg / min and a density d approximately 0.912 g / cm3. and a melting point d about 122-123 ° C; and a third polymer comprising 38.0% by weight of an ethylene vinyl acetate copolymer (EVA) available from Exxon Chemical Company of Houston Texas, E.U.A. , under the trade name Escorene LD 701.06 and having the following properties reported: 10.5% vinyl acetate content, 0.93 g / cm3 density, melt index 0.19 dg / min, and a melting point of approximately 97 ° C; 2.0% by weight of a slip processing aid sold under the tradename TM 11384E118 by Techmer PM of Clinton, Tennessee, E.U.A .. The mixed resins were plasticized in an extruder and a monolayer thermoplastic tube was extruded. Due to the availability of equipment, three extruders and a three layer die were used, but all the layers had the same composition so three identical layers were coextruded together to produce a monolayer film. The profile of the extruder and extruder barrel temperature was set at approximately 166 ° C. The extruded primary plastic tube was then cooled, reheated, biaxially stretched, and cooled according to a double bubble process and the resulting biaxially stretched film was wound on a reel. The draw ratio or orientation in the machine direction (M.D.) was approximately 4.5: 1 and the bubble or orientation ratio in the transverse direction (T.D.) was approximately 4.0: 1. The drag point or orientation temperature is below the melting point for the layer to be oriented and above the Vicat softening point of the layer. The drag point temperature of the films of Examples 1-7 is believed to have been about 71-79 ° C. A second comparison film, Example 4, was similarly made, except as noted below. The film of Example 4 was a mixture of 70.0%) by weight of the first polymer (Affinity PL1880); 14.0% by weight of the second polymer (Attane XU61509.32); 14.0% by weight of the third polymer (Escorene LD 701.06); and 2.0% by weight of the processing aid (TM 11384E118). The conditions of processing and orientation were similar to those previously indicated, except that the orientation relationships of M.D. /T.D. were approximately 4.5: 1 and 3.7: 1, respectively. Examples 2,3 and 5-7 were all the films of the invention and were made as described above for Example 1 with similar processing and orientation conditions, except as noted below. Example 2 was a mixture of 35.0% by weight of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.895 g / cm3, a melt index of 1.6 dg / min, a melting point of 95 ° C, which is available under the tradename Affinity PF 1140 from the Dow Chemical Company of Midland, Michigan, USA; 25% by weight of a second polymer comprising Attane XU 61509.32; 38.0% of a third polymer comprising Escorene LD 701.06; and 2.0% by weight of the processing aid (TM 11384E118). The orientation relationships of M.D. /T.D. were approximately 4.5: 1 and 4.0: 1, respectively.

Example 3 was a mixture of 35.0% by weight of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.884 g / cm3, a melt index of 1 dg / min, a melting point of 83 ° C with a shoulder peak less than 72 ° C, which is available under the trade name Affinity VP 8770 from the Dow Chemical Company of Midland, Michigan, USA; 25.0% by weight of a second polymer comprising Attane XU 61509.32; 38.0% by weight of a third polymer comprising Escorene LD 70.06; and 2.0% by weight of the processing aid (TM 11384E118). The orientation relationships of M.D. /T.D. were approximately 4.6: 1 and 3.5: 1, respectively. The film of Example 5 was a mixture of 70.0% by weight of a first polymer comprising Affinity PF 1140; a second polymer comprising 14.0% by weight of Attane XU 61509.32; a third polymer comprising 14.0% by weight of Escorene LD 701.06; and 2.0% by weight of the processing aid (TM 11384E118). The orientation relationships of M.D. / T.D were approximately 4.8: 1 and 3.8: 1, respectively. Example 6 was a mixture of 70.0% by weight of a first polymer comprising Affinity VP 8770; 14.0% by weight of a second polymer comprising Attane XU 61509.32; 14.0% by weight of a third polymer comprising Escorene LD 701.06; and 2.0% by weight of the processing aid (TM 11384E118). The orientation relationships of M.D. /T.D. were approximately 4.6: 1 and 3.0: 1, respectively. The film of Example 7 was a mixture of 70.0% by weight of a first polymer comprising Affinity VP 8770; 14.0% by weight of a second polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.906 g / cm3, a melt index of 0.8 dg / min, a melting point of 122- 123 ° C, which is available under the trademark Atane 4203 from the Dow Chemical Company of Midland, Michigan, USA; 14.0% by weight of a third polymer, but comprising an ethylene vinyl acetate copolymer (EVA) available from Exxon Chemical Company of Houston, Texas, E.U.A., under the trade name Escorene LD 705 and having the following reported properties; 13.3% by weight of vinyl acetate content, 0.935 g / cm3 of density, a melt index of 0.4 dg / min, a Vicat softening point of 77 ° C, and a melting point of approximately 92 ° C; and 2.0% by weight of the processing aid (TM 11384E118). The orientation relationships of M.D. /T.D. were approximately 4.6: 1 and 2.8: 1, respectively. The resulting films were tested for various physical properties and these properties are listed in Table 1 below.

(I heard Oí Oí PICTURE BRIGHTNESS% of Drilling TEAR CALIBER to a Turbidity of Ariete Shrinkage Shrinkage STRENGTH Ex. AVERAGE Angle < at 90 ° C at 80 ° C g / rnil No. thousand at 45 ° Force Stress Energy%% (g / PL) (μ) Newtons MPa Total MD / TD MD / TD MD / TD Julios 1 2.34 77 1.2 91 249 0.92 31/39 16/25 17/24 (59.4) (0.67 / 0.94) 2 2.34 88 1.7 87 229 0.86 43/50 23/32 30/40 (59.4) (1.18 / 157) 3 2.42 88 1.5 80 210 0.90 52 / 54 28/37 39/44 s. (61.5) (1.54 / 1.73) 00 4 2.20 91 1.0 103 292 1.07 29/39 14/25 45/43 (55.9) (1.77 / 1.69) 5 2.41 91 1.2 92 234 1.14 55/57 35/40 37/47 (61.2) (1.46 / 1.85) 6 2.92 85 2.0 57 * 123 0.71 62/59 50/50 59/67 (74.1) (2.32 / 2.64) 7 2.60 87 1.4 67 * 143 0.90 * 66/66 54/54 50/51 (66.0) (1.97 / 2.01) * The film was not punctured, but was stretched until the transverse assembly made contact with the shock absorbing pads. The force and total energy represent values obtained at the maximum deformation of the film reached at the point of contact of the transverse assembly with the shock absorbing pads.

From the properties measured and listed in Table 1, it can be seen that the films of the invention of Examples 2, 3 and 5-7 have excellent optical properties, commercially acceptable, that is, high brightness values and low turbidity, which are comparable with those measured for the films comparatives of Examples 1 and 4. Also, the films of the invention have significantly higher shrink values at both 90 ° C and 80 ° C. The films of the invention also have very good puncture resistance properties, although slightly less than for the comparative examples. Referring now to the specific comparisons, the formulations of the film of Comparative Example 1 and Example 2 (of the invention) were identical, except that the composition of the first polymer of Comparative Example 1 differed from the first polymer of Example 2 of the invention . The Comparative Example used the ethylene-octene-1 copolymer having a higher melting point, a slightly higher density, and a lower melt index. The conditions of orientation were similar. The use of the lower density, lower melting material resulted in the production of a film with shrinkage values greatly exceeding 90 ° C and also at lower temperatures, such as 80 ° C. Example 2 of the invention had measured values of shrinkage at 90 ° C that were 28 to 39% higher than for Comparative Example 1; Shrinkage values at 80 ° C were 28 to 44% higher. For Example 2, the brightness values were significantly higher, and the maximum strength of the water hammer resistance was slightly lower (5%). The total energy absorbed at the maximum force was approximately 25% lower for the film of the invention, but, nevertheless, this was a very good value. Resistance to break propagation, as measured through the Elmendorf Rupture Resistance Test, were higher for the film of the invention, but acceptable for commercial applications. The lower breakdown propagation resistances are advantageous in heat sealing operations using impulse sealing technology, where the sealing apparatus both seals and cuts the film, with the rebord of the removed film breaking along the cut . The lower rupture propagation resistances allow the flange to be removed quickly and without damaging the seal or the film.

Example 3 of the invention was similar to the Comparative Example 1, except that the composition of the first polymer was changed by replacing an ethylene-octene-1 copolymer having a lower density (0.884 g / cm3), and a lower melting point (83 ° C). The amounts of the first polymer in the mixture remained the same. The results were similar to that reported for Example 2 of the invention, except that the shrinkage values were significantly higher, although the orientation ratio in the machine direction was only slightly higher (4.6: 1) and in the Cross direction was actually lower (3.5: 1). The previous film samples were not irradiated. However, they can also be usefully interlaced through irradiation, for example, at a level of 2-6 megarads (Mrad) after biaxial stretching (said irradiation process hereinafter referred to as post-irradiation), in the form generally described by Lustig and others, US patent No. 4,737,391, which is incorporated herein by reference.

EXAMPLES 8-16 In Examples 10-16, biaxially stretched, heat-shrinkable, co-extruded films of the present invention were made and their physical properties were tested. Examples 8 and 9 are Comparative Examples that are not of the present invention. Examples 8-16 are three layer films. An extruder was used for each layer. Each extruder was connected to an annular coextrusion die from which the heat-plastified resins were co-extruded into a primary tube having a first inner layer, a second core layer and a third outer layer. The first and third layers being directly joined to the opposite sides of the second core layer. The thickness ratio of the first / second / third layers was approximately 62:10:28. In Examples 8-16, for each layer, the resin mixture was fed from a hopper to an attached single screw extruder, where the mixture was heat-laminating and extruded through a co-extrusion die of three layers to a primary tube. The barrel temperatures of the extruder for the second (core) layer were between 120-141 ° C; for the first (internal) layer and for the third (outer) layer they were approximately 149-160 ° C. The temperature profile of the coextrusion die was set at approximately 160-177 ° C. The extruded multilayer primary tube was cooled by spraying cold running water at about 10-20 ° C. In E ples 8-16, a cooled primary tube with a flat width of approximately 80 to 90 mm was produced by passing through a pair of pressure rollers. The cooled, inflated primary tub was inflated, reheated , biaxially stretched, and cooled again to produce a biaxially stretched and biaxially oriented film, which was wound on a reel. The orientation ratio in the machine direction was from about 4.5: 1 to 4.8: 1 and the orientation ratio in the transverse direction was from about 3.5: 1 to 4.7: 1 for all the films, the drag point or the orientation temperature was below the predominant melting point for each layer oriented and above the predominant vidri transition point of the layer and is believed to be approximately 68 85 ° C for Examples 8-16. The biaxially oriented films resulting from Examples 8-16 had an average caliber of 47.49 to 65.27 microns and had an excellent appearance. Examples 8 and 9 are the comparative examples of commercially successful multi-layer oxygen barrier films suitable for packaging a variety of items, including processed meat. For Example 8, the heat sealing layer was the first layer of the multi-layer film and the inner layer of the film layer. The first layer was composed of: about 32.0%) by weight of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.888 g / cm3, a melt index of 2.2 dg / min, a melting point of 70 ° C, which is available under the trade name Exact 4053 from Exxon Chemical Company of Houston, Texas, USA; a second polymer comprising 23.0% by weight of a very low density polyethylene ethylene-to-olefin copolymer sold by Dow Chemical Company of Midland, Michigan, USA, under the tradename SL4100, which is a copolymer of ethylene and octene-1 having a reported melting index of approximately 1.0 dg / min and a density of approximately 0.912 g / cm3, and a melting point of approximately 123 ° C; and a third polymer comprising 34.0% by weight of ethylene and vinyl acetate (EVA) available from Elf Atochem S.A. from Paris, France under the trade name Evatane 1002VN3 and having the following reported properties: 11% vinyl acetate content, density 0.93-0.94 g / cm3, melt index 0.28 dg / min, and a melting point of about 96 ° C; 4.0% of a stabilizing additive in an EVA carrier resin sold under the trade name of Ampacet 500301 by Ampacet Corp. of Tarrytown, New York, E.U.A .; 4.0% by weight of a slip agent in a polyethylene carrier resin sold under the trade name of Ampacet 10090, and 3.0% by weight of a processing aid, which is a fluoroelastomer and erucamide combined in a copolymer carrier resin of a -olefin sold under the trade name of Ampacet 500906. For Examples 8-16, each core layer was composed of a 5.5: 1 mixture of a copolymer of vinylidene chloride-methyl acrylate and a copolymer of vinylidene-chloride. vinyl chloride. For Comparative Example 8, the third (outer) layer used the polymers described above with respect to the first layer. The third layer comprised a mixture of: a first polymer of approximately 33.0% by weight of Exact 4053; a second polymer comprising 25.0% by weight of VLDPE (SL4100); and a third polymer comprising 39.1% by weight of EVA (Evatane 1002 VN3); 0.4% by weight of a slip agent (Ampacet 10090); and 2.5% by weight of a processing aid (Ampacet 500906). Comparative Example 9 was similar to Comparative Example 8, except that for the first polymer the Exact 4053 was replaced with a copolymer predomina of ethylene with a butene-1 monomer and having a reported density of about 0.885 g / cm3, an index melting point of 3.6 dg / min, a melting point of 71 ° C, which is available under the tradename of Tafmer A-4085 from Mitsui Petrochemical Comapany of Tokyo, Japan; the second polymer was replaced with an ethylene copolymer predomina of ethylene with an octene-1 monomer and having a reported density of about 0.912 g / cm 3, a melt index of 1.0 dg / min, with a Vicat softening point of 95 ° C and a melting point of about 122-123 ° C, which is available under the tradename Attane XU 61520.01 from the D ow Chemical Company of Midland, Michigan, USA; and the third polymer was replaced with LD 701.06. Equivalent additives were also used. For examples 10, 13 and 14, the heat sealing layer was the first layer of the multilayer film and the inner layer of the film tube. The first layer comprised a mixture of the invention of: about 32.0% by weight of a first polymer comprising a copolymer predomina of ethylene with an octene-1 monomer and having a reported density of about 0.884 g / cm3, a melt index of 1.3 dg / min, a melting point of 67-68 ° C, which is available under the trade name of DexPlas 2M042 from Dex-Plastomers VOF from Geleen, The Netherlands; a second polymer comprising 23.0% by weight of XU 61509.32; and a third polymer comprising 34.0% by weight of Evatane 1002 VN3; 4.0% by weight of a stabilizer additive Ampacet 500301; 4.0% by weight of a slip agent Ampacet 10090, and 3.0%) by weight of an Ampacet 500906 processing aid. For Examples 10, 13 and 14, the third (outer) layer used the polymers described above with respect to the first cap. The third layer comprised a mixture of the invention of: a first polymer of approximately 33.0% by weight of DexPlas 2M042; a second polymer comprising 25.0% by weight of Attane XU 61509.32; and a third polymer comprising 39.1% by weight of EVA Evatane 1002 VN3; 0.4% by weight of a slip agent (Ampacet 10090); and 2.5% by weight of a processing aid I? pacet 500906). For Examples 11, 12, 15 and 16 of the invention, the composition was as described for Examples 10, 13 and 14, except that in the inner and outer layers each respective first polymer was replaced with VP8770. The flat widths (half the circumference of the biaxially stretched film) of the tubular film were of a nominal value of 300 mm for the biaxially stretched films of Examples 8 to 12, and were 350 mm for the films of the Examples 13-16. The multilayer films of Examples 8 to 13 and 15 were irradiated after orientation through an electron beam in accordance with methods well known in the art.

The films of Examples 8, 11, 13 and 15 were irradiated at a level of 4.8 Mrad. The film of Example 9 was irradiated at a level of 3.8 Mrad. The films of Examples 10 and 12 were irradiated at a level of 4.0 Mrad. The films of Examples 14 and 16 were not irradiated. The physical properties of the multilayer films were tested and are reported in Tables 2 and 3 below.

K TABLE 2 Resistance to PEF AFORACIÓ. I DE ARIETE Stress Resistance Rupture CALIBER at RT Shrinkage Shrinkage% Brightness Eg PROM. X I O3, psi Strength Voltage Energy at 0 ° C to 80 ° C Turbidity of Angle g / thousand No. thousand (MPa) Newton MPa Total%% at 45 ° (g / μ) (μ) MD / TD Julios MD / TD MD / TD MD / TD 8 2.38 10.9 / 9.9 51 176 0.44 50/51 ND 7.1 78 32/59 (60) (75/68) (1.3 / 2.3) 9 2.30 1 1.3 / 1 1.3 60 213 0.37 46/50 ND 9.0 73 29/36 (58) (79/78) (1.1 / 1.4) 2.11 11.2 / 11.8 66 198 0.57 52/53 ND 8.2 77 35/58 (54) (77/81) (1.4 / 2.3) 1 1 2.21 1 1.2 / 12.6 84 242 0.78 51/53 ND 9.3 77 50/61? (56) (77/87) (2.0 / 2.4) °° 12 2.57 12.4 / 13.6 99 265 1.07 54/55 ND 11.1 76 63/87 (65) (86/93) (2.5 / 3.4) 13 1.87 11.4 / 13.5 77 273 0.74 54/55 37/42 8.4 78 38/52 (47) (85/93) (1.5 / 2.0) 14 2.12 ND 72 244 0.68 54/57 ND 4.6 78 ND (54) 15 2.17 12.6 / 14.7 95 278 0.94 51/54 32/39 8.5 75 64/60 (55) (87/101) (2.5 / 2.4) 16 2.32 ND 93 280 0.90 52/56 ND 4.6 78 ND (59) RT = Ambient temperature (~ 20-23 ° C) ND = Not determined NJ t O TABLE 3 STRENGTH OF IRRADIATION EXTENSION SCALE 1% OF MODULE SHRINK SHRINK SEAL OF A DRYING BREAK • At 90 ° C A RT ly- IMPULSE at RT at RT g / thousand g / thousand No. min./max. % MPa (g / μ) (g μ) Mrad volts MD / TD MD / TD MD / TD MD / TD 8 ND 237/31 1 227/267 124/75 74/55 4.8 (49 / 3.0) (2.9 / 2.2 ) 9 ND 237/295 225/220 147/1 13 42/38 3.8 (5.8 / 4.4) (1.7 / 1.5) 10 27-47 224/335 246/275 143/84 72/61 -0 (5.6 / 3.3) (2.8 / 2.4) 1 1 ND 181/274 246/229 139/120 61/90 4.8 (5.3 / 4.7) (2.4 / 3.5) 12 28-47 205/266 234/289 134/105 64/75 4.0 (5.3 /4.1) (2.9 / 3.0) 13 27-49 215/239 256/272 ND ND 4.8 14 ND ND ND ND ND 0 ND 206/232 242/265 ND ND 4.8 16 ND ND ND ND ND 0 RT = Ambient temperature (~ 20-23 ° C) ND = Not determined Referring to Tables 2 and 3, Comparative Examples 8 and 9 present physical property values, which are acceptable for food packaging films, which are commercially useful for packing processed meats. Examples 10-16 all have comparable or better values for shrinkage, gloss and tension properties. The puncture resistance properties were clearly superior for the films of the invention. This is remarkable because the increase in drilling resistance properties come without loss in shrinkage properties. The puncture resistance properties of the films of the invention are 11% to 80% higher for the maximum water hammering force, and 30% or 132% higher for the total energy measured, absorbed by the film with respect to the films of Comparative Examples 8 and 9. The shrinkage values for the films of the invention vary from being comparable to the comparative film of Example 8 being from 8% to 11 > higher for values measured at 90 ° C. The films also had very good shrinkage values at lower temperatures, ie 80 ° C, see, for example, the films of Examples 13 and 15. The multilayer films of the invention demonstrate excellent tensile strengths, and secant modulus values of 1%. The optical properties were also quite good; the turbidity and gloss values reflect measurements made on films that have been coated with an anti-block starch powder. The elongation at break is good. The films of the invention were processed well and had desirable sealing properties. The seal scale test of The pulse demonstrates a commercially acceptable and advantageously wide sealing scale. The above tests demonstrate that multi-layer films having a good good heat sealing layer can be made to produce high shrink films having superior puncture resistance properties and other commercially desirable physical properties. The films of the invention have strong seals and have a desirable combination of high shrinkage capacity at low temperatures, for example 80 or 90 ° C, high drilling resistance and good optical properties. The use of a lower melt index second polymer in the inventive blend of the film improves bubble stability during orientation and also positively contributes to superior shrinkage and improved puncture resistance. The use of the higher melting ethylene-octene-1 copolymer, lower melt index (higher molecular weight) as the first polymer of the mixture in Examples 11, 12, 15 and 16 produces films having properties of enormously superior perforations. The use of an ethylene-octene-1 copolymer having a lower melting point (but still higher than that of the first ethylene-octene-1 polymer of Comparative Examples 8 and 9), and having an index lower melting (higher molecular weight) as the first polymer in Examples 10, 13 and 14 results in properties that include perforation properties relative to the comparative films of Examples 8 and 9. Also, with respect to the Examples 11, 12, 15 and 16, these films have moderate tear propagation resistances and are less susceptible to degradation of optical properties through irradiation. The core layer of all the films of Examples 8-16 provided oxygen and moisture barrier properties.

EXAMPLES 17-25 In Examples 17-25, 3 layer films of the invention biaxially stretched, heat-shrinkable, co-extruded, as described above for the films of Examples 8-16 were made, except as noted below. Examples 17-25 are suitable for packing items such as fresh red meat or processed meat. For Examples 17-25, each second (core) layer comprised a 5.5: 1 mixture of a copolymer of vinylidene chloride-methyl acrylate and a copolymer of vinylidene chloride-vinyl chloride. The formulations of the first (internal) layer and the third (outer) layer were as follows. For Examples 17, the inner layer of the film comprised a mixture of: 33% by weight of a first polymer of Affinity PF 1140; 23% by weight of a second polymer, which was an ethylene copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.912 g / cm 3, a melt index of 1.0 dg / min, with a softening point of 95 ° C and a melting point of about 122-123 ° C, which is available under the tradename Attane XU 61520.01 from the Dow Chemical Company of Midland, Michigan, USA; 36% by weight of a third EVA polymer (Escorene LD 701.06); 4.0% of a stabilizing additive (Ampacet 500301); and 4% by weight of a processing aid (Ampacet 100594), which combines a fluoroelastomer processing aid with an oleamide slip additive in a carrier resin of ethylene α-olefin copolymer. For Example 17, the third (outer) layer used the polymers described above with respect to the first layer. The third layer comprised a mixture of the invention of: a prime polymer of about 33.0 wt.% Affinity PF 1140; a second polymer comprising 25.0% by weight of VLDPE Attan XU 61520.01; and a third polymer comprising 40.0% by weight of EVA (Escorene LD 701.06); and 2.0% of Ampacet 100510, which combines a fluoroelastomer processing aid with an oleamide slip additive in a carrier resin of ethylene α-olefin copolymer. The process conditions were as described above for the multilayer films of Example 8-16, except as described below. The ratio d thickness of the first / second / third layers was d approximately 62: 9: 29. With respect to the films of the invention of the Examples 18-25, the layer ratio was the same as for Example 17 and the process conditions were similar and the formulations were the same, except as follows. For Examples 18 and 19, the first polymer of the inner and outer layer of Example 17 was replaced with DexPla 2M042, which was described above. The amount of the first polymer used in the inner layer was changed to 35% by weight; The amount of the outer layer remained at 33% The second third polymers remained the same as for Example 17. In the inner layer, the stabilizer Ampacet 500301 was replaced with 2% of a similar stabilizer available from Techmer PM under the trade name of Techmer 11381E118 and auxiliary processing Ampacet 100594 was replaced with 4% of a similar processing aid (but having a slip agent d erucimide) available from Techmer PM under the trade name d Techmer 1141E118. process Ampacet 100510 was replaced with 2% of a similar processing aid (but using a ducucide slip agent), which is available from Techmer PM under the commercial name of Techmer 11378E118.

Example 20 had the same film formulation of Examples 18 and 19, except that the second polymer of the inner and outer layers was replaced with Attane XU61509.32. Eff. 21 had the same film formulation of Example 20, except that the amounts of the first, second and third polymers of the inner and outer layers were changed. The inner layer of the film of Example 21 used 45% / 19% / 30% of the respective first / second / third polymers. The outer layer used 45% / 20% / 33%, respectively. Examples 22 and 23 had the same formulation as for Example 20, except that the first polymer of the inner and outer layers was replaced by Affinity VP 8770. Both Aerosols 24 and 25 both used an internal layer mixing formulation of 32% of a first polymer of Affinity VP 8770; 23% of a second polymer of SL4100; 34%) of a third polymer of Evatane 1002 VN3; 4% by weight of a slip agent (Ampacet 10090); 3% by weight of a processing aid, which was combined with a fluoroelastomer and an erucamide in an ethylene α-olefin copolymer carrier resin sold under the trade name of Ampacet 10919, and 4% of AN 400, which is an anti-oxidant in the EVA carrier resin available from A. Schulman Inc. of Wales, Great Britain. The mixture formulation of the outer layer of the films of Examples 24 and 15 was equal to the inner layer, except that the amounts of the first, second and third polymer were adjusted to 33%, 25% and 39.1%, respectively, and the additives were replaced with 0.4% of Ampacet 10090 (slip agent) and 2.5% of Ampacet 10919 (processing aid). The films were all irradiated through an electron beam cure unit at varying levels to promote entanglement. The biaxially stretched films of Examples 17-25 were irradiated after orientation in the electron beam according to methods well known in the art at the levels indicated in Table 5 below. In Example 17, a flattened, biaxially stretched film tube with a circumference of approximately 66.04 cm was produced. In Examples 18-25, a flattened, biaxially stretched film tube with a circumference of about 76.83 cm was produced. The machine direction ratio was about 4.9: 1 and the ratio of the transverse direction was about 4.3: 1 to 4.4: 1 for all the films, except the cross-directional relationship for the film of Example 17 was of about 4.1: 1. The physical properties of the multiple layer films (films irradiated for Examples 17-23 and 25) were tested and reported in Tables 4 and 5. what Ul CUxADRO 4 Resistance to ARIETE PERFORATION Stress Resistance Rupture CALIBER at RT Shrinkage Shrinkage% Brightness Eg PROM. X I O3, psi Tension Force Energy at 90 ° C at 80 ° C Angle Turbidity g / thousand No. thousand (MPa) Newton MPa Total%% at 45 ° (g / μ) (μ) MD / TD Julios MD / TD MD / TD MD / TD 17 2.33 1 1.9 / 12.2 76 276 0.63 43/49 24/34 9.3 78 47/64 (59) (82/84) (1.9 / 23) 18 2.36 9.3 / 12.3 82 257 0.71 51/53 32/40 7.3 75 27/48 (60) (64/85) (1.1 / 1.9) 1 2.61 ND 79 254 0.66 50/53 32/40 6.1 74 35/56 (66) (1.4 / 2.2) 2.44 1 1.2 / 13. i 94 274 0.82 51/53 33/40 7.1 72 40/61 oo (62) (77/90) (1.6 / 2.4) "-1 21 2.61 11.0 / 12.5 95 243 0.97 53/56 37/42 7.8 74 38/45 (66) (76/86) (1.5 / 1.8) 22 2.37 1 1.1 / 14.6 107 309 0.99 51/54 32/39 6.7 76 37/48 (60) (77/101) (13/19) 23 2.66 ND 1 14 295 1.07 51/54 32/39 5.7 77 39/45 (68) (1.5 / 1.8) 24 2.05 ND 65 169 0.51 50/51 27/35 5.4 78 17/57 (52) (0.67 / 2.2) 1.98 13.3 / 10.8 63 163 0.52 47/48 25/34 6.3 73 ND (50) (92/74) ND ^ Not determined RT = Ambient temperature (~ 20-23 ° C) NJ NJ Ul O TABLE 5 SCALE OF IRRADIATION FORCE OF FORCE SHAFTING SEAL SHRINKLE SHRINK IMPULSE? L? RUPTURE I% * OF MODULE AT 90 ° C TO RT lij. min./max. Mrad to RT DRYER g / thousand g / thousand No. volts% MPa (g / μ) "(g / μ) MD / TD MD / TD MD / TD MD / TD 17 31-46 3.75 213/240 177/163 133 / 127 64/93 (5.2 / 5.0) (2.9 / 3.7) 18 27-48 3.75 155/270 201/180 127/101 21/39 (5.0 / 4.0) (0.8 / 1.5) 19 27-45 4.25 ND ND 142 / 120 29/29 oo (5.6 / 4.7) (1.1 / 1.1) oo 28-42 3.75 185/257 187/200 135/116 19/30 (5.3 / 4.6) (0.7 / 1.2) 21 27-40 3.75 204/274 182/171 128/1 14 25/37 (5.0 / 4.5) (1.0 / 13) 22 27-38 3.75 178/262 181/221 151/138 38/38 (5.9 / 5.4) (1.5 / 1.5) 23 28-50 + 4.25 ND ND 148/132 28/36 (5.8 / 5.2 ) (1.1 / 1.4) 24 ND 0 ND ND ND ND 25 19-22 3.95 156/276 192/201 ND ND RT = Ambient temperature (~ 20-23 ° C) ND = Not determined Referring now to Tables 4 and 5, the films of Examples 17-25 all have physical property values which are acceptable for plastic films, which are commercially useful for packing items, for example, fresh or processed meat. All the films of the invention had excellent shrinkage values at low temperatures, for example, 80 ° C or 90 ° C. The comparison of the film of example 17 with that of Example 18 shows that the substitution of an ethylene octene-1 copolymer having a lower melting point and a density as the first polymer in the mixture of the invention used in the first and third layer allows the production of biaxially-stretched film having higher shrinkage values, an improved puncture resistance and lower breaking strength values. Although a lower but adequate shrink force was obtained, advantageously so was a wider sealing scale. The films of Examples 18 and 19 were identical to each other except for the irradiation levels. Little irradiation was observed in the physical properties between the film of Example 18, the cu was irradiated at a level of 3.75 Mrad and the film of Example 19, which was irradiated at a level of 4.25 Mrad. The lower drilling voltage values for Example 19 are believed to be due to gauge variation. The film of Example 20 is similar to that of Example 1 • except that the second polymer of the mixture of the invention was replaced with an ethylene-octene-1 copolymer having a lower melt index (higher molecular weight). It is seen that the films produced in Example 20 have a higher maximum perforating force, a high voltage, and a higher total high absorbed energy without negatively impacting the shrinkage values or the optical properties. The highest, but acceptable, resistance to breakthrough propagation was also measured as a narrower sealing scale. The formulation of the film of Example 21 was similar to that of Example 20, except that the amount of the first polymer was increased, while the amounts of the second and third polymers were -reduced. The increased relative proportion of the ethylene-octene-1 polymer having a melting point of 55 to 95 ° C resulted in smoother, biaxially stretched more ductile films having a higher total energy absorption, a resistance to burst propagation lower, a higher shrinkage, and a narrower sealing scale. The film of Example 22 was similar to that of Example 20, except that the first polymer of the inventive mixture of the first and third layers was replaced with an ethylene-octene-1 copolymer of the same reported density but having a higher melting point and lower melting index (higher molecular weight). Much better puncture resistance values were measured for the film of Example 22, and also better optical properties, and better breakthrough resistances. The films of Example 22 had a narrower sealing scale. These films of the invention had higher shrinkage forces, which can beneficially result in more hermetic packages. The film of Example 23 was similar to that of Example 22, but was irradiated at a higher dose level (4.25 Mrad compared to 3.75 Mrad for Example 22). The measured physical properties were generally comparable with the wider sealing scale probably due to the increased entanglement of the highest irradiated level, and the slightly higher resistance values to the perforation. Probably due to the variation of caliber. The films of Examples 24 and 25 were made in a different orientation line and are believed to have been processed at higher orientation temperature conditions relative to the films of Examples 17-23. It can be seen that higher orientation temperatures tend to result in lower shrinkage values and puncture resistance for the formulations of the film of the invention. The non-irradiated film of Example 24 generally has lower shrinkage values and better optical properties. It is expected that the irradiation will expand the sealing scale of the films of the invention and the pulse scale for the film of Example 25 is seen as an anomaly.

The films of the present invention have desirable sealing properties. The impulse seal scale test demonstrates a commercially acceptable and advantageously wide sealing scale. Differences of 1 and 2 volts in the values of the sealing scale are important and the extension of 2 volts at either end of the scale is believed to translate to wider scales for many commercially available sealants than in Sentinel. Unless otherwise stated, the turbidity and gloss values reflect measurements made on films that have been coated with an anti-block starch powder. Examples 8-25 are three layer films. However, multi-layer films of two or four or more layers are contemplated in the present invention. The multilayer films of the invention can include bonding or adhesive layers, themselves with layers for adding or modifying various properties of the desired film such as heat sealing capacity, tension, abrasion resistance, rupture strength, drilling resistance, optical properties, water gas barrier properties, shrinkage capacity, and printability. These layers can be formed by any suitable method including coextrusion, extrusion coating and lamination. Biaxially stretched, heat shrinkable coextruded 5 layer films can also be made using similar equipment as for the previous examples, except that additional extruders and a five layer co-extrusion die can be used. Various dies known in the art can be used, including, for example, spiral dies. The films can be made under similar conditions and, for example, as noted below. The resins can be heat-laminated through extruders and extruded through the die into a primary tube having five sequential concentric layers (1, 2, 3, 4, 5), the first layer being the inner surface layer of the tube and the fifth layer being the outer surface layer of the tube. The ratio of the first / second / third / fourth / fifth layers can be, for example, 10/50/7/10/23.

EXAMPLES 26-79 Examples 26-79 are additional illustrative embodiments contemplated by the present invention. The structures of these examples are listed in Tables 10-13. These structures can be made as rocks, sheets, tubes, or films. The films of the invention having the indicated structures can be made through processes similar to those described above, including, without limitation, blown bubble, double bubble or trapped bubble, laying frame, co-extrusion and coating lamination processes (all these Processes are suitable for producing all films of the present invention, including unoriented, uni- or biaxially oriented films.

Shrinkable with heat or shrinkage without heat. The structures of the present invention may or may not be interwoven, for example, by irradiation at a level of 2-5 Mrad or higher, either before or after any stretching process or configuration or orientation. All films of the invention of these or any of the above-described embodiments can be used to pack materials, such as overwraps or bag-forming. These films or bags can be closed through fastening, but they also have excellent heat sealing properties. In Examples 26-37 and 57, the blends of the invention are shown as the first layer of a multi-layer structure, per. example, a film of at least 5 layers, while in Examples 38-56, the blends of the invention shown as an inner layer of a multilayer structure of at least 5 layers, however, will be appreciated. that the blend is of the invention in its own right and may comprise the monolayer structure or multiple layer structures of 2 or more layers as either or both of one or more surface or interior layers. Also, in Examples 58-79 monolayer structures are shown, but it should be appreciated that these described structures can form one or more layers of a multi-layer structure, for example, a heat-shrinkable film. Referring to Tables 6-9, several structures of the invention are shown.

I NJ Ul O TABLE 6 (O L / i Oí TABLE 7 VO ss t to o U) Ui TABLE 8 VD --4 TABLE 9 Referring to Tables 6 and 7, Component A comprises a first polymer having a melting point of 55 to 95 ° C comprising a copolymer predominantly of ethylene and at least one α-olefin comprising octene-1. Component B comprises a second polymer having a melting point of 115 to 128 ° C comprising a copolymer of ethylene and at least one α-olefin. Component C comprises a third polymer having a melting point of 60 to 110 ° C comprising a copolymer of ethylene and a vinyl ester (for example, EVA), an acrylic acid, a methacrylic acid, or an alkyl acrylate. Component D comprises a copolymer predominantly of ethylene and at least one α-olefin (preferably octene-1) having a melting point of 91 to ".10 ° C, and preferably having an Mw / Mp <3.5. Component E comprises a processing aid Component F comprises an interpolymer having at least two melting points, one of which is about 91 to 100 ° C, and the other is about 115 to 128 ° C. Component G comprises an interpolymer having at least two melting points, one of which is about 55 to 95 ° C and refers to one component which is a copolymer of ethylene and octene-1, and the other is of about 91 to 110 ° C and which relates to a component which is a copolymer of ethylene and at least one α-olefin (preferably octene-1) Component H comprises a polymer having at least two melting points , one of which is about 55 to 95 ° C and rel ation with a component that is an ethylene and octene-1 copolymer, and the other is about 115 to 128 ° C and is related to a component that is a copolymer of ethylene and at least one α-olefin (preferably octeno-1). Component I comprises an interpolymer having three melting points, the first of which is about 55 to 95 ° C and is related to a component which is a copolymer of ethylene and octene-1, the second of which is about 91. at 110 ° C and is related to a component which is a copolymer of ethylene and at least one α-olefin (preferably octene-1), and the third of which is about 15 to 128 ° C and is related to a component which is a copolymer of ethylene and at least one α-olefin (preferably octene-1), each of the three melting point peaks being at a separation of at least 5 ° C from each other. Referring to the embodiments of the invention described in Tables 6-9 and also the above embodiments described in all the Examples, the present invention contemplates the use of mixtures of the first, second and / or third polymer components, which are They are made in situ by polymer resin manufacturers, such as, for example, ether-polymers. In this way, the claimed and described mixtures can be of separate resins, for example, in the form of pellet or powder, which are combined through the manufacture of post-polymer dry-mix, wet or melt, for example through a converter or film maker, or alternatively one or more polymer components can be formed with an additional polymer by the resin manufacturer using a process involving monomer streams or components feeding a sequential or simultaneous catalyst system. In the present invention, interpolymerized products (ie, interpolymers) are contemplated and included within their definition. An interpolymer, as that term, is used herein and means a polymer product, which comprises at least two polymers, for example, ethylene copolymers, which is polymerized either in a single reactor or in separate multiple reactors operated in parallel or in series, for example, as described by Parikh et al., application, of PCT No. US92 / 11269 (Publication No. WO 93/13143) entitled "Ethylene Interpolymer Polymerizations" filed on December 29, 1992, claiming a US priority Series No. 07 / 815,716, filed on December 30, 1991, which are hereby incorporated by reference in their entirety. In another aspect of the invention, one or more alternative layers having gas barrier properties can be incorporated into a multilayer film either as an intermediate or surface layer, or both. For example, the ethylene-vinyl alcohol copolymer (VEO), vinylidene chloride-methyl acrylate copolymer, nylon such as nylon 6 or amorphous nylon, polyvinylidene chloride-vinyl chloride copolymer (pvdc). Acrylonitriles were other materials that have oxygen barrier properties can be used in one or more layers such as the core layer. It is also possible to use resin mixtures having gas barrier properties, for example, a mixture of nylon with EVOH. Typical gas barrier films will have a gas barrier layer having an oxygen transmission for 24 hours at 1 atmosphere of less than 233 cm3 / m2, preferably less than 45 cm3 / m2. In various multi-layer embodiments of the invention, well-known adhesive resins such as copolymers of EVAs modified with maleic anhydride or polyethylenes, or acrylic acid or methacrylic acid can be used, for example, with ethylene, in addition to or instead of the various polymers indicated above e, n the intermediate layers or in the outer layers to adhere to the adjacent layers. The use of such adhesives may be advantageous, for example, when the layers containing polymers such as EVOH are to be units to the ethylene polymer containing layers such as VLDPE. For preferred five layer film embodiments of the invention, the total thickness of the film is typically such that the first layer will typically comprise 10-50%, the second layer will comprise 10-50%, the third layer will comprise approximately 5-10%. %, the fourth layer will comprise 10-25%, and the fifth layer will comprise 10-25%) of the total film thickness. The puncture resistance of the composition formulations of the present invention when made with oriented films can be dramatically affected by adjusting the temperature of the drag point. The films of the invention can be made with surprisingly and unexpectedly high puncture resistance properties including a very high total energy absorption E and a maximum puncture force P by carefully controlling the drag point temperature. The unique formulations of the present invention result in dramatic property improvements. The values of shrinkage, shrinkage force and puncture resistance properties are all strongly affected by the drag point temperature. If the film is oriented at too high a temperature, these properties will be unnecessarily low and will not have all the advantages of the invention for some uses. The best drag point temperature can be experimentally determined without undue experimentation by those skilled in the art and may depend on the exact selected formulation, the number of layers, thicknesses, orientation speeds, etc. The puncture resistance values demonstrated by the present invention are vastly superior to many of the prior art films. The drag point temperature can be measured through an infrared pyrometer, which is directed as closely as possible to the real bubble expansion drag point. The point of drag is the point location on the primary tube that begins to stretch enormously as it passes into a secondary bubble. With reference to Figure 4 of the drawings, a schematic view of a primary tube 40 is shown with the point of drag indicated by the arrows d resulting in an expanded oriented film 41. The good films of the present invention can be made at orientation temperatures (point of entrainment) of 83.8. ° C and the like, but the films of the present invention allow the manufacture of extraordinary films having dramatically improved perforation properties using lower dropping point temperatures, especially drag point temperature in the range of 65 to 88 ° C, and preferably from 65 to 79 ° C. Those skilled in the art of manufacturing biaxially oriented films know different and various processes of said manufacturing and the films of the present invention include biaxially oriented or biaxially stretched films without considering the method used for their production as well as uniaxially oriented films and essentially no oriented including blown or heat blown films. In another embodiment of the invention, the second polymer of the mixture of the invention described above is replaced by a copolymer predominantly of ethylene with at least α-olefin, preferably octene-1, having a melting point of 91 to 110. ° C, and preferably has an Mw / Mn <; 3.5. Below are further examples of preferred embodiments, particularly useful, for example, for processing and packaging films in applications where the products undergo post-cooking surface pasteurization and / or are cooked foods, such as cooked turkey breasts, hams and / or meat.

EXAMPLES 80-82 In Examples 80-82, biaxially stretched, heat shrinkable, co-extruded, multi-layer films of the invention were made and tested. Examples 81-82 are essentially four layer films; however, due to the availability of equipment during the experimental operations, a five-layer die was used and the identical layer formulation was used for both the fourth and fifth layers (Example 80 is essentially a three-layer film since the first and second layers had identical formulations as well as the fourth and fifth layers). The use of the five-layer die to do what is the formula, a four-layer film (three layers for Example 80) is equivalent to using 4-layer or 3-layer dice, respectively. In these examples, an extruder was used for each layer. Each extruder was connected to the same annular coextrusion die from which the heat-plastified resins were co-extruded forming a primary tube having a first inner layer, a second intermediate layer, a third core layer, a fourth intermediate layer and a fifth layer external The first and fifth layers were directly joined to the opposite sides of the third core layer through the second and fourth intermediate layers, respectively. The thickness ratio of the first / second / third / fourth / fifth layers was approximately 10: 50: 6.6: 23.4: 10. In Examples 80-82, for each layer, the resin mixture was fed by a hopper to an attached single screw extruder, where the mixture was heat-plasticized and extruded through a five-layer co-extrusion die to a primary tube. The barrel temperatures of the extruder for the third layer (core) were approximately 132-146 ° C; and for the remaining layers were approximately 149-182 ° C. The temperature profile of the die was set at approximately 154-171 ° C. The co-extruded primary pipe f ß cooled by spraying cold running water at approximately 7-16 ° C. The cooled primary tube was flattened through the passage by a pair of pressure rollers. In Example 81, a flattened primary tube with a flat width of approximately 10.32 cm was produced. For Examples 81 and 82, the primary flat width was 10.16 cm and 10.24 cm, respectively. The cooled, flattened primary tube was reheated, biaxially stretched and cooled again. The stretched, cooled film was flattened and wound on a reel. The draw ratio in the machine direction was from about 4.4: to 4.6: 1 and the orientation ratio in the transverse direction was from about 3.3: 1 to 3.4: 1 for the films of Examples 80-82. The drag point or orientation temperature was below the predominant melting point for each layer oriented and above the predominant Tg of the layer and is believed to be approximately 68-85 ° C for Examples 80-82. The biaxially oriented films resulting from Examples 80-82 all had good shrinkage values at 90 ° C. For Examples 80-82, the film structures were as follows. The resulting heat sealing layer was the first layer of the multilayer film and the inner layer of the film tube. The layer compositions are presented below. The percentages are based on the weight for the indicated layer. For Examples 80-82, each core layer (the third layer) comprised a 5.5: 1 mixture of vinylidene chloride-methyl acrylate copolymer (vdc-ma) and vinylidene chloride-vinyl chloride copolymer (vdc-vc). Lesser amounts of lubricants and / or coloring additives of plasticizers such as ultramarine blue pigment were also used and were designated as PC additives in the frames. For these and other examples, a preferred mixture of vinylidene chloride-methyl acrylate copolymer (vdc-ma) and vinylidene chloride-vinyl chloride copolymer (vdc-vc) is described in US Pat. No. 4,798,751, which is incorporated herein by reference in its entirety. For Examples 80-82, layers 2, 4 and 5 comprised identical formulations of: 33% VP 8770; 38.75% of LD 701.06; 23% of XU 61509.32; 3.25% of TM 11384E118; and 2% of 11381 E118. For Example 80, the first inner layer also comprised the same formula as layers 2, 4 and 5 above. For Example 81, the first heat seal layer comprised 100% of a random copolymer of propylene and butene-1 having a melting point of about 144 ° C from Shell Oil Company, Atlanta, Georgia, under the trade name of CEFOR SRD4-131. For Example 82, the first heat sealing layer comprised 100% of a random copolymer of propylene and butene, having a butene-1 content of about 14% by weight, a melting point of about 131 ° C, and a Machine direction at 230 ° C and 2.16 kg at approximately 6.5 dg / min from Shell Oil Company, Atlanta, Georgia under the tradename of CEFOR SRD4-141. The previous film samples were not treated with irradiation. However, they can also be usefully interlaced through irradiation, for example, at a level of 2-6 megarads (Mrad) after biaxial stretching (said irradiation process hereafter referred to as post-irradiation), in the form generally described by Lustig and others, US patent No. 4,737,391, which is incorporated herein by reference. The physical properties of Examples 80-82 were tested and reported in Tables 10 and 11.

I-J Ui or TABLE 10 Resistance to PEP LFORACIÓr-, DE ARIETE Tension Perforation of CALIBER to RT ^ Hot Water Shrinkage% of Brightness 02GTRt * PROM, XI O3, psi Force Stress Energy 95 ° C at 0 ° C Angle Turbidity at RT thousand (MPa) Newton MPa Total seconds% at 45 ° 0% RH (μ) MD / TD Julios (micras) MD / TD 2.36 1 1.7 / 10.6 85 239 0.857 34 50/52 2.6 85 ND (59.9) (81/73) (75) 2.86 10.1 / 8.0 72 203 0.606 120+ 40/44 3.5 81 29 (72.6) (70/55) (69 ) (84) 2. 56 i 0.4 / 9.2 68 208 0.559 120+ 38/48 2.8 85 36 (65.0) (72/63) (67) (69) Ambient temperature (~ 20-23 ° C) ND = Not determined the oxygen gas transmission rate (O2GTR) in units of cm3 per meter2 per 24 hours an atmosphere for proven film. ra 02GTR, the thickness of the film is below the speed in microns (). 1 J? O Ul o TABLE 1 1 FORCE OF FORCE WIDTH ELONGATION 1% SHRINK MODULE SHRINK FLAT TO DRY BREAKING, AT 90 ° C AT RT Ex. Mm to RT to RT g / thousand g / thousand No.% MPa (g / μ) (g / μ) MD / TD MD / TD MD / TD MD / TD 80 333 215/399 26.8 / 25.6 159/95 70/77 (185/176) (6.3 / 3.7) (2.8 / 3.0) 81 343 338/282 41.5 / 36.3 ND ND (286/251) 82 356 296/271 29.0 / 28.8 ND ND (200/199) LT = Ambient temperature (~ 20-23 ° C) ND = Not determined 11 Referring to Tables 10 and 11, Example 80 has acceptable property values for commercially useful processed meat packaging films, but has a low resistance to hot water drilling. This short time for resistance to hot water drilling together with low hot water seal resistors makes this three layer film unsuitable for use in applications where the film and its heat seals are subject to cooking processes or of pasteurization, which can be long lasting, that is, minutes in contrast to the contact of 5-20 seconds with hot water that usually occurs with a shrinking operation. Examples 81-82 of the invention all have excellent hot water drilling values of at least 2 minutes at 95 ° C, while the three-layer film of Example 80 was measured at 34 seconds. The optical properties (low turbidity and high brightness) were excellent. Very good values for shrinkage, tension, brightness and turbidity properties for the films of the invention were coupled with the excellent properties of hot water. The elongation to the rupture of the film of the invention is also good and the film processed as well. The O2 barrier properties of the illustrated films are controlled by the core layer, which uses a copolymer mixture known to provide excellent oxygen and moisture barrier properties. In view of the same thickness core layer being used in all Examples 80-82, similarly excellent barrier properties are expected for all films. Examples 80-82 are expected to have desirable properties resistant to sealing and perforation. The multilayer films of the invention demonstrate an excellent combination of puncture resistance, optical properties, modulus, shrinkage values and tensile properties. In addition, the films of the invention are expected to have excellent seal strength properties including seal tensile strength values in excess of 400 g / cm at 88 ° C, and hot water seal resistance at 95 ° C. at least 100 seconds, preferably at least 200 seconds, and most preferably at least 300 seconds over a wide variety of sealing. In another preferred embodiment of the invention, the first layer may comprise LLDPE, propylene-ethylene copolymer or a mixture thereof. Preferred polymers of the first inner layer include: a linear low density polyethylene, which is a copolymer predominantly of ethylene with a hexene-1 monomer, having a reported density of about 0.917 g / cm3, a machine direction of 1.0 dg / min, an acute peak melting point of 120 ° C and a second melting point of 108.5 ° C, which is available under the Exceed ™ 350D60 trademark of Exxon Chemical Co. of Houston, Texas, and a random copolymer of propylene and ethylene having a melting point of <136 ° C, a p of approximately 0.895 g / cm3, a Vsp of approximately 120 ° C (ASTM 1525 (1 kg)) and a machine direction at 230 ° C and 2.16 kg of approximately 5 dg / min (available from Solvay &Cié as a bio-oriented film grade resin, under the trade name Eitex P KS 409). The present invention contemplates that films of four or more layers of structures having a heat sealing surface layer of at least 50% by weight of, (i) a copolymer of propene and at least one selected α-olefin of the group consisting of ethylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a propene content of at least 60% by weight, or (ii) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1 -, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm3 coextruded, laminated by coating or otherwise unitized to structures of three or more layers as defined in Examples 10-16 and 18-25 above and 85 -97 below. Especially preferred are oxygen barrier films of four or more layers having: a first heat sealing layer as defined above; a second and / or fourth intermediate layer comprising a mixture of at least three copolymers comprising: from 45 to 85% by weight, most preferably from 50 to 85%, of a first polymer having a melting point of 55 to 95 ° C that 14 it comprises at least one ethylene-octene-1 copolymer; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer of ethylene and a vinyl ester or an alkyl acrylate; wherein said first and second polymers have a combined weight percentage of at least 50% by weight, said weight percentage based on the total weight of said first, second and third polymers; a third core oxygen barrier layer comprising a nylon, EVOH or a vinylidene chloride copolymer; and a fourth layer comprising one or more of the following polymers: an ethylene-α-olefin copolymer, nylon, ionomer, an ethylene vinyl ester, an ethylene-acrylic acid copolymer, an ethylene-alkyl acrylate copolymer, an ethylene-methacrylic acid copolymer, a methyl ethylen-acrylate copolymer, an ethylene homopolymer, a propylene homopolymer or copolymer with ethylene, butene-1, methylpentene-1, hexene-1, octene-1 or mixtures thereof same. It is further contemplated that barrier films of four or more layers can be made having a heat sealing layer as defined above with an intermediate or outer layer comprising a mixture of at least three polymers comprising: from 25 to 85% by weight weight of a first polymer having a melting point of 55 to 95 ° C comprising at least one copolymer of ethylene and octene-1; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin, and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer of ethylene and a vinyl ester or an alkyl acrylate; wherein said first and second polymers have a combined weight percentage of at least 50% by weight, said percentage by weight based on the total weight of the first, second or third polymers. The invention contemplates that the individual interpolymer may comprise both the first and the second polymers of the mixture defined above, and that interpolymers of either or both of the first and second polymers may be made and used as defined above with respect to the polymers F, G, H and I in Tables 6-9 (see Examples 26-79) above.

EXAMPLES 83-88 In Examples 85-88, biaxially stretched, heat-shrinkable, coextruded, multi-layer films were made and tested. Examples 83 and 84 are comparative and not of the invention. Examples 83-88 are essentially three layer films; however, due to the availability of equipment during the experimental operations, a die was used in five layers and the identical layer formulation was used for both the first, second fourth and fifth layers. The use of a five-layer die to make what is a broad formula, a three-layer film is equivalent to using a three-layer die. In these examples, an extruder was used for each layer. Each extruder was connected to the same die of annular coextrusion from which heat-plastified resins were coextruded forming a primary tube having essentially Jres layers, with a ratio of internal layer thickness / core layer / outer layer of approximately 60: 6.6: 33.4. In Examples 83-88, for each layer, the resin mixture was fed via a hopper to an attached single screw extruder, where the mixture was heat-laminating and extruded through a five-layer co-extrusion die at a primary tube. The barrel temperatures of the extruder for the core layer were approximately 132-146 ° C; and for the remaining layers were approximately 163-171 ° C. The die temperature profile was set at approximately 154-166 ° C. The co-extruded primary tube was cooled by spraying with cold running water at about 7-16 ° C. The cooled primary tube was flattened through the passage by a pair of pressure roller. In Examples 83, 86 and 87, a flattened primary tube with a flat width of approximately 10.0 cm was produced. For Examples 84, 85 and 88, the primary flat width was 9.86 cm, 9.68 cm and 10.16 cm, respectively. The cooled flattened primary tube was reheated, biaxially stretched and cooled again. The cooled and stretched film was flattened and wound on a reel. The draw ratio in the machine direction was from about 3.9: 1 to 4.1: 1 for Examples 83, and 85-87, and was 3.6: 1 for Example 84, and 4.3: 1 for Example 88. The orientation ratio in the transverse direction was from about 3.6: 1 to 3.7: 1 for the films of Examples 83, 84, 87 and 88, and was 3.8: 1 for Examples 85, and 3.5 for Example 86. the drag point or orientation temperature was below the predominant melting point for each oriented layer and above that predominant Tg of the layer and is believed to be approximately 68-85 ° C for Examples 83-88 . The biaxially oriented films resulting from Examples 83-88 all had good shrinkage values at 90 ° C. For Examples 83-88, the film structures were as follows. The heat sealing layer was the first layer of the multi-layer film and the inner layer of the film tube. The compositions of the layer are presented below. The percentages are based on the weight for the indicated layer. For Examples 83-88, each core layer (the third layer) comprised a 5.5: 1 mixture of a copolymer of vinylidene chloride-methyl acrylate (vdc-ma) and a copolymer of vinylidene chloride-vinyl chloride (vdc-vc). Lesser amounts of lubricant and / or colorizing, plasticizing additives, such as ultramarine blue, were also used. For these and other examples, a preferred mixture of vinylidene chloride-methyl acrylate copolymer (vdc-ma) and vinylidene chloride-vinyl chloride copolymer (vdc-vc) is described in US Pat. No. 4,798,751, which is incorporated herein by reference in its entirety. For Examples 85 of the invention, the layers on both sides of the core layer comprised identical formulations of: 58% in g, that of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of approximately 0.884 g / cm3, a melt index of 1.3 dg / min, a melting point of 67 ° C with a peak less than 107 ° C, which is available under the trade name of DexPlas 2M054 from Dex -Plastomers VOF of Geleen, Netherlands; 19% by weight of 4203; 20% by weight of an ethylene vinyl acetate copolymer having a vinyl acetate content of 18%, a melting point of about 87 ° C, a density of 0.94 g / cm3, a melt index of 0.65 dg / min, which is commercially available from DuPont Company of Wilmington, Delaware, USA, under the trade name Elvax 3165; and 3% of 11416E118.

For Comparative Example 83, the layers comprised the same mixture as for Example 85 above, except that EVA was changed to 58% LD 705 and the amount of 2M1054 was changed to 19%.

For Comparative Example 84, the layers comprised the same mixture as for Example 85 above, except that the amounts changed to 19% of 2M054; 58% of 4203; 20% of 3165; and 3% of 11416E118. Example 86 was similar to Example 85, except that 3165 EVA was replaced with LD 705. Example 87 replaced the layers on both sides of the core layer with a mixture of 35% PF 1140; 25% of 4203; 37% > of LD; and 3% of 11384E118. Example 88 was similar to Example 87, except that the amounts changed to 60% of PF 1140; 19% of 4203; and 18% LD 705. Samples from the previous films were not treated with irradiation. However, they can also be usefully interlaced through irradiation, for example, at a level of 2-6 megarads (Mrad) after biaxial stretching (said irradiation process hereafter referred to as post-irradiation), in the form described by Lustig and others, US patent No. 4,737,392, which is incorporated herein by reference.

SJ Ul t o TABLE 12 Resistance PEF LFORACIÓJN? OF ARIETE Resistance to Tension Rupture Pierce CALIBER to RT Hot Water Shrinkage% of Brightness Cj. PROM. XI O3, psi Force Stress Energy 95 ° C at 0 ° C Angle Turbidity g / thousand No. thousand (MPa) Newton MPa Total seconds% at 45 ° (g / μ) (μ) MD / TD Julios (mieras) MD / TD MD / TD 83 2.15 8.8 / 11.0 62 174 0.65 11 52/60 34/45 84 2.9 (54.6) (61/76) (61) 84 2.73 10.912.1 82 161 1.06 50/57 37/44 53 1 1.5 (69.3) (75 / 84) (74) 85 2.54 1 1.4 / 13.3 71 160 0.93 16 59/64 53/61 86 2.6 NJ (64.5) (78/92) (66) 86 2.70 10.2 / 10.8 67 141 0.90 9 56/62 52 / 54 67 5.9 (68.6) (71/74) (64) 87 2.48 ND 82 209 0.96 ND 49/56 31/41 85 3.0 (63.0) 2.35 ND 86 206 1.07 ND 49/55 30/40 86 2.7 (59.7) RT = Ambient temperature (~ 20-23 ° C) ND = Not determined Referring to Table 12, Comparative Example 83 having a low amount (19%) of the first polymer and a high amount (58%) of EVA has a low puncture resistance as demonstrated by a low total energy absorbed at a maximum drilling value and a low drilling force. The films of the invention have a very good puncture resistance and good tensile strengths. All the films of the Examples had excellent shrinkage values at both 90 ° C and 80 ° C. Low values of temperature (80 ° C) and excess of 50 in either or both the direction of the machine and in the transverse direction for Examples 85 and 86 are remarkably high. The optical properties in general are also very good with the films of the invention of Examples 85, 87 88 having an excellent high brightness and low turbidity values. E Comparative Example 84 exhibits an extremely low brightness, a high turbidity that is 2 to 4 times as turbid as the films of the invention. All of these films of Examples 83 88 were made with powder formation, which may affect the optical properties. The combination of high shrinkage values, particularly at low temperatures, and optical excellent with high puncture resistance produces film suitable for packaging applications and having unique combinations of highly desirable physical properties. It is especially noteworthy that an EVA copolymer having high VA content (for example, 19% by weight) can be mixed with ethylene-to-olefin copolymers to produce films having both high shrinkage values at 90 and 80 ° C as excellent high gloss and low turbidity as it is seen in Example 85, with all values of shrinkage in excess of 45% and brightness in excess of 80% and a turbidity of less than 5%. It is surprising that the films having excellent optical properties with shrinkage values at 80 ° C in excess of 50% in a single direction were produced and in Example 85 the film of the invention had an excess of 50% shrinkage both in the Machine direction as in the transverse direction.

EXAMPLES 89-97 In Examples 89-97, biaxially stretched, heat-shrinkable, co-extruded multi-layer films were made and tested. Examples 89-97 are essentially three layer films; however, due to the availability of equipment during the experimental operations, a five-layer die was used and the identical layer formulation was used for both the first, second, fourth and fifth layers to make what is a formula, a film of three layers. In these Examples, an extruder was used for each layer. Each extruder was connected to the same annular coextrusion die from which heat-plastifed resins were co-extruded into a primary tube having essentially three layers with a ratio of internal layer thickness / core layer / outer layer of approximately 60: 6.6 : 33.4. In Examples 89-97, the films were made through a process and under conditions similar to those employed for Examples 83-88, except as follows. The barrel temperatures of the extruder for the core layer were approximately 121-135 ° C; and for the remaining layers were approximately 171-188 ° C. The die temperature profile was set from about 154 to 171 ° C. In Examples 89-91, a flattened primary tube with a flat width of about 8.1 cm (about 7.1 cm for Examples 92-97) was produced. The draw ratio in the machine direction was from about 4.9: 1 to 5: 1 for Examples 89-97. The orientation ratio in the transverse direction was approximately 4.1: 1 for the films of Examples 89-91, and was approximately 4.7: 1 for Examples 92-97. For Examples 89-97, the film structures were as follows. The heat sealing layer was the first layer of the multi-layer film and the inner layer of the film tube. The layer compositions are presented below. The percentages are based on the weight for the indicated layer. For Examples 89-97, each core layer (the third layer) was similar to that used in Examples 83-88 above. For Example 89, the layers on both sides of the core layer comprised identical formulations of: 35% by weight of a first polymer comprising a copolymer predominantly of ethylene with an octene-1 monomer and having a reported density of about 0.896 g / cm3, a melting index of 1.2 dg / min, a melting point of 90 ° C, which is available under the trade name of DexPlas 2M070 from Dex-Plastomers VOF from Geleen, The Netherlands; 23% by weight of 4203; 35% by weight of LD 705; 5% by weight of a processing aid, which was combined with a fluoroelastomer and erucamide in an ethylene-to-olefin copolymer carrier resin, sold under the trade name of Techmer PM 11506E12, and 2% of a stabilizing additive in an ethylene-to-oiefine copolymer carrier resin, sold under the trade name Ampacet 501234 by Ampacet Corp. of Tarrytown, New York, USA For Example 90, the layers comprised the same mixture as for Example 91 above, except that the amounts changed to 45% of 2Mo 70; 21% of 4203; 27% LD 705. Example 91 was similar to Example 89, except that LD 705 EVA was replaced with 18% of 3165, and the amounts of 2M070 and 4203 were changed to 58% and 17%, respectively. Examples 92 and 93 were similar to Example 91, except that in both Examples, 3165 EVA, 11506E12, and 501234 were replaced by LD 705, 11416E118 and 1138E118, respectively.

Examples 94 and 95 were similar to Example 93, except that 4203 and LD 705 were changed to XU 61509.32 and LD 701 in both Examples. Examples 96 and 97 were similar to Example 95, except that the amounts changed to 34% of 2M070; 23% of XU 61509.32; and 36% LD 701. Examples 89-92, 94 and 96 were not treated with irradiation. Examples 93, 95 and 97 were entangled through irradiation at a level of 4.0 megarads (Mrad) after biaxial stretching in the manner generally described by Lustig et al., U.S. Pat. No. 4,737,391, which is incorporated herein by reference. The physical properties of Examples 89-97 were tested and reported as shown in Table 13.

IJ lo i o CUADO 13 RESISTANCE RAM PUNCTURE TO THE TENSION CALIBER to RT Shrink Shrinkage% of Brightness to IRRADIATION Eg PROM. MPa Strength Voltage Energy at 90 ° C to 80 ° C Turbidity Angle (Mrad) No. (μ) MD / TD Newton MPa Total%% of 45 ° Julius MD / TD MD / TD 89 54 81/95 94 272 0.95 52/56 32/41 6.5 73 0 90 54 92/97 107 287 1.22 53/57 33/43 5.3 75 0 91 53 89/108 105 276 1.23 55/58 37/45 7.7 64 0 92 59 101/108 118 292 1.29 52/57 32/42 4.9 83 0 93 60 93/90 94 245 0.89 51/53 30/37 7.2 78 4 94 59 98/100 1 17 297 1.22 49/56 29/40 4.5 85 0 95 57 101/80 91 258 0.82 46/51 26/33 7.2 77 4 ¡3 96 54 84/95 99 297 1.23 43/51 25/36 4.9 79 0 ° " 97 53 94/99 86 295 0.73 43/48 22/32 7.3 76 4 RT = Ambient temperature (~ 20-23 ° C) Referring now to Table 13, in this group of Examples, a first polymer having a higher density and a melting point relative to the first polymer used in Examples 83-88, was used with several secondary polymers of ethylene-a- olefin and EVAs. The biaxially oriented films of Examples 89-97 all had excellent shrinkage values at both 90 ° C and 80 ° C, but less than those reported for Examples 83-88. Generally, these films had excellent puncture resistance and good tensile properties. The interlacing effect through irradiation is seen in the reduction of optical properties, shrinkage and puncture resistance, however, irradiation is typically performed for many applications, where a wide range of heat sealing is required , since the entanglement extends the sealing scale and raises the temperature resistance of the interlaced film. The films of these examples all have commercially acceptable desirable properties. Although this invention has been described with reference to certain specific embodiments, it will be recognized by those skilled in the art that many variations are possible without departing from the scope and spirit of the invention.

Claims (111)

1. - A flexible, thermoplastic, biaxially stretched, heat-shrinkable film having at least one layer comprising a mixture of at least three copolymers comprising: from 25 to 85% by weight of a first polymer having a melting point of 55 at 95 ° C comprising at least one copolymer of ethylene and octene-1; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 5% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer not modified or modified with ethylene anhydride and a vinyl ether, acrylic acid, methacrylic acid or an alkyl acrylate; e wherein the first and second polymers have a combined weight percentage of at least 50% by weight, the percentage in pes based on the total weight of said first, second and third polymers; and wherein said film has a shrinkage value at 90 ° C of at least 45% in at least one of the direction of the machine and the transverse direction, and said film has a ram perforation force of at least 65. Newtons.

2. A polymer film according to claim 1, wherein the first polymer has a melting point of 80-85 ° C.

3. A polymer film according to claim 1, wherein the first polymer is a bipolymer.

4. A polymer film according to claim 1, wherein the first polymer is a terpolymer comprising: ethylene, hexene-1 and octene-1; or ethylene, butene-1 and octene.

5. A polymer film according to claim 1, wherein the second polymer comprises a co-polymer of ethylene and octene-1. 6.- A polymer film according to the claim

1, wherein the third polymer is selected from the group consisting of ethylene-vinyl acetate copolymer, ethylene-methylstyrene-acrylate copolymer, ethylene-butyl-acrylate copolymer, and ethylene-ethyl-acrylate copolymer. 1.- A polymer film according to the claim

1, wherein the third polymer comprises a copolymer of ethylene and vinyl acetate.

8. A polymer film according to claim 1, further comprising a fourth polymer having a melting point of 91 to 110 ° C.

9. A polymer film according to claim 1, which has a turbidity value of less than 10%.

10. A polymer film according to the claim

1, wherein said film has a shrinkage value at 80 ° C of at least 30% in at least one of the directions of the machine and transverse.

11. A polymer film according to claim 1, wherein the film has a shrinkage value at 80 ° C of at least 35% in at least one of the directions of the machine and transverse.

12. A polymer film according to claim 1, wherein the film has a shrinkage value at 80 ° C of at least 35% in both the machine and transverse directions.

13. - A polymer film according to claim 1, wherein the film has a shrinkage value at 90 ° C of at least 45% in at least one of the directions of the machine and transverse. 14.- A ^ polymer film according to the claim

1, wherein the film has a shrinkage value at 90 ° C of at least 45% in both the machine and transverse directions.

15. - A polymer film according to claim 1, wherein the film has a total energy at a maximum drilling force of at least 0.60 Joules.

16. A polymer film according to claim 1, wherein the film has a total energy at a maximum drilling force of at least 0.80 Joules.

17. A polymer film according to claim 1, wherein the film has a total energy at a maximum drilling force of at least 1.0 Joules.

18. A polymer film according to claim 1, where the film has a maximum water hammer drilling force of at least 100 Newtons.

19. A polymer film according to claim 1, wherein the film has a maximum water hammering force of at least 110 Newtons.

20. A polymer film according to claim 1, wherein the film has a water drilling tension of at least 140 MPa.

21. A polymer film according to claim 1, wherein the first polymer has a Mw / Mn ratio of 1.5 to 3.0.

22. A polymer film according to claim 1, wherein the first polymer has a ratio of Mw / Mn from 2.2 to 2.7.

23.- A polymer film according to the claim

1, wherein the first polymer has a melt index of 1.5 to 3.0 dg / min.

24. A polymer film according to claim 1, wherein the first polymer has a melt index of 0.3 to 1.5 dg / min.

25. A polymer film according to claim 1, wherein the first polymer has a melt index of less than 2.5 dg / min.

26. A polymer film according to claim 1, further comprising at least one additional thermoplastic layer.

27.- A polymer film according to the claim

1, which further comprises at least three thermoplastic layers

• additional.

28.- A polymer film according to the claim

1, wherein the mixture containing the layer has been interlaced by irradiation.

29. A polymer film according to claim 1, wherein the layer is the innermost heat sealable layer of a tube formed of said film.

30. A polymer film according to claim 1, wherein the film is manufactured in bags.

31.- A polymer film according to claim 26, wherein the additional layer comprises a gas barrier layer and the film has an oxygen transmission ratio less than 233 cm3 / m2 at 1 atmosphere.

32.- A polymer film according to the claim

26, wherein the film is a multilayer tubular film formed by coextrusion or coating lamination and the mixture comprises a heat sealing layer, which is the inner layer of the tube.

33.- A polymer film according to claim 1, wherein the mixture comprises at least 50% by weight of the layer based on the total weight of the layer.

34.- A polymer film according to claim 1, wherein the first polymer is present in an amount of 2 to 45% by weight, based on the total weight of the first, second third polymers.

35.- A polymer film according to claim 1, wherein the first polymer is present in an amount of 3 to 40% by weight, based on the total weight of the first, second third polymers.

36.- A polymer film according to claim 1, wherein the first polymer is present in an amount of 4 to 85% by weight, based on the total weight of the first, second third polymers.

37.- A polymer film according to claim 1, wherein the first polymer is present in an amount of 5 to 85% by weight, based on the total weight of the first, second third polymers.

38.- A polymer film according to claim 1, wherein at least one of the first, second and third polymers comprises an interpolymer.

39.- A polymer film according to claim 1, wherein at least one interpolymer comprises the first second polymers.

40.- A polymer film according to claim 27, wherein the film comprises: a first heat sealing surface layer comprising a polymer selected from the group consisting of: (at least 50% by weight) a copolymer of propene 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 % by weight, and (b) at least 50% by weight of an ethylene copolymer and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene- 1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm 3, a second intermediate layer, a third core layer comprising at least 80% by weight ( based on the weight of said third layer) of at least one copolymer of vinylidene chloride with from 2 to 2 0% by weight (based on the weight of said copolymer) of vinyl chloride or methyl acrylate; and a fourth layer of surface; wherein at least one of the second and fourth layers comprises the three copolymer mixture defined in claim 1, said core layer is disposed between the second and fourth layers.

41. A polymer film according to claim 40, wherein said film has a shrinkage value at 80 ° C of at least 30% in at least one of the directions of the machine and transverse.

42.- A polymer film according to claim 40 or 41, wherein the film has a tensile seal strength of at least 400 g / cm at 88 ° C.

43.- A polymer film according to claim 40, wherein the film has a tensile seal strength of at least 600 g / cm at 88 ° C.

44. A polymer film according to claim 40 or 41, wherein the film has a resistance value to the hot water drilling of at least 40 seconds at 95 ° C.

45.- A polymer film according to claim 40, wherein the film has a resistance value to the perforation by hot water of at least 100 seconds at 95 ° C.

46. - A polymer film according to claim 40 or 41, where the film has an average hot water sell resistance value of at least 200 seconds at 95 ° C.

47.- A polymer film according to the claim

40 or 41, where the film has a resistance value of sell for hot water average of at least 300 seconds at 95 ° C.

48. A polymer film according to claim 1 or 40, wherein the film has a drilling tension of at least 200 MPa.

49.- A polymer film according to claim 40, wherein the melting point of the first layer polymer of heat sealing surface (b) is at least 115 ° C.

50.- A biaxially stretched, shrinkable film with heat comprising a mixture of: (i) an interpolymer comprising at least one ethylene-octene-1 copoiimer and having a first melting point of 55 to 95 ° C and a second melting point of 115 to 128 ° C, and (iii) a polymer having a melting point of 60 to 110 ° C comprising an unmodified or modified copolymer with ethylene anhydride and a vinyl ester, acrylic acid, methacrylic acid, or alkyl acrylate; the film having a shrinkage value at 90 ° C of at least 45% in at least one of the directions of the machine or transverse.

51.- A flexible, thermoplastic, biaxially stretched, heat-shrinkable film having at least one layer comprising a mixture of at least three copolymers comprising: 45 to 85% by weight of a first polymer having a melting point 55, at 95 ° C comprising at least one ethylene-octene-1 copolymer; from 5 to 355 by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer unmodified or modified with ethylene anhydride and a vinyl ester, acrylic acid, methacrylic acid, or an alkyl acrylate; wherein the first and second polymers have a combined weight percentage of at least 50% by weight, the percentage by weight based on the total weight of the first, second and third polymers; and wherein the film has a total energy absorption of at least 0.70 Joules and a shrinkage value at 90 ° C of at least 50% in at least one of the directions of the machine and crosswise.

52. A polymer film according to claim 51, wherein the mixture comprises from 50 to 85% by weight of the first polymer.

53. A polymer film according to claim 51, wherein the film has a maximum perforation force of at least 90 Newtons.

54.- A polymer film according to the claim

51, wherein the film has a shrinkage value at 80 ° C of at least 35% in at least one of the directions of the machine and transverse.

55.- A polymer film according to claim 51, wherein the film has a shrinkage value at 80 ° C of at least 35% in both directions of the machine and transverse.

56. - A polymer film according to claim 51, wherein the film has a shrinkage value at 80 ° C of at least 50% in at least one of the directions of the machine and transverse.

57.- A polymer film according to claim 51, wherein the film has a shrinkage value at 80 ° C of at least 50% in both directions of the machine and transverse.

58. - A polymer film according to claim 51, wherein the film has a total energy absorption of at least 0.90 Joules.

59.- A polymer film according to claim 51, wherein the film has a maximum tension of at least 200 MPa.

60.- A polymer film according to the claim

51 or 52, wherein at least one of the first, second and third polymers comprises an interpolymer.

61.- A polymer film according to claim 51, further comprising at least one additional thermoplastic layer.

62.- A polymer film according to claim 51, further comprising at least four additional thermoplastic layers.

63.- A polymer film according to claim 51 or 52, wherein the film comprises: a first heat sealing surface layer comprising a polymer selected from the group consisting of: a first sealing surface layer with heat comprising a polymer selected from the group consisting of: (a) at least 50% by weight 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% by weight, and (b) at least 50% by weight of an ethylene copolymer and at least one a olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm3; a second intermediate polymer layer; a third core layer comprising at least 80% by weight (based on the weight of said third layer) of at least one copolymer of vinylidene chloride with from 2 to 20% by weight (based on the weight of said copolymer) of vinyl chloride or methyl acrylate; and a fourth polymeric surface layer; wherein at least one of the second and fourth layers comprises said mixture of three copolymers defined in claim 5.1, and the core layer is disposed between the second and fourth layers.

64.- A polymer film according to the claim

63, wherein the film has a tensile seal strength of at least 400 g / cm at 88 ° C.

65.- A polymer film according to claim 63, wherein the film has a value of resistance to drilling by hot water of at least 40 seconds at 95 ° C.

66. - A polymer film according to claim 63, wherein the film has a puncture resistance value by hot water of at least 100 seconds at 95 ° C.

67. - A polymer film according to claim 63, wherein the film has an average hot water seal strength of at least 200 seconds at 95 ° C.

68.- A polymer film according to claim 63, wherein the film has an average hot water seal strength of at least 300 seconds at 95 ° C.

69.- A polymer film according to claim 63, wherein the melting point of said first heat sealing surface layer polymer (b) is at least 115 ° C.

70.- A biaxially stretched film, heat shrinkable, comprising at least three layers, wherein the first layer comprises a mixture of at least three polymers comprising: a first polymer having a melting point of 55 to 95 ° C comprising an ethylene-octene-1 copolymer; a second polymer having a melting point of 115 to 128 ° C comprising a copolymer of ethylene and at least one α-olefin; a third polymer having a melting point of 60 to 110 ° C comprising a copolymer of ethylene and a vinyl ester or alkyl acrylate; a third layer comprising at least 50% by weight of a copolymer of ethylene with at least one alpha-olefin or at least one vinyl ester or mixtures thereof, and a second layer between the first and third layers; the second layer comprises a copolymer of vinylidene chloride, a nylon or a copolymer of ethylene with a vinyl alcohol; the film having a maximum water hammer drilling force of at least 65 Newtons, a total energy absorption of at least 0.50 Joules and a shrinkage value at 90 ° C of at least 45% in at least one of the machine and cross directions.

71.- A polymer film according to claim 70, wherein the film has a shrinkage value at 90 ° C of at least 45% in both directions of the machine and transverse.

72.- A polymer film according to the claim

70, wherein said film has a shrinkage value at 80 ° C of at least 35% in at least one of the directions of the machine and transverse.

73.- A polymer film according to claim 70, wherein the film has a maximum perforation force of at least 90 Newtons.

74.- A polymer film according to claim 70, wherein the film has a total energy absorption of at least 0.9 Joules.

75.- A polymer film according to the claim

70, wherein at least one of the first, second and third polymers comprises an interpolymer.

76.- A polymer film according to claim 70, wherein at least one interpolymer comprises the first and second polymers.

77.- A polymer mixture of at least three copolymers comprising: from 25 to 85% by weight of a first polymer having a melting point of 55 to 95 ° C comprising at least one copolymer of ethylene and octene- 1;

from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer of ethylene and a vinyl ester or an alkyl acrylate; wherein the first and second polymers have a combined weight percentage of at least 50% by weight, said percentage based on the total weight of the first, second and third polymers.

78. A mixture according to claim 77, wherein the first polymer is present in an amount of 25 to 45% by weight, based on the total weight of the first, second and third polymers.

79. A mixture according to claim 77, wherein the first polymer is present in an amount of 30 to 40% by weight, based on the total weight of the first, second and third polymers.

80.- A mixture according to claim 77, wherein the first polymer is present in an amount of 45 to 85% by weight, based on the total weight of the first, second and third polymers.

81. A mixture according to claim 77, wherein the first polymer is present in an amount of 50 to 85% by weight, based on the total weight of the first, second and third polymers.

82. - A mixture according to claim 77, wherein at least said first, second and third polymers comprise an interpolymer.

83. A mixture according to claim 77, wherein an? -terpolymer comprises said first and second polymers.

84.- A flexible film comprising at least one layer comprising the mixture of claim 77.

85.- A flexible film according to claim 84, wherein the film comprises: a heat sealing surface layer comprising a polymer selected from the group consisting of: (a) at least 50% by weight 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% by weight, and (b) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group consisting of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm3: an intermediate layer; a core layer; an outer protective surface layer; wherein at least one of the intermediate and outer layers comprises a polymer blend of at least three copolymers comprising: from 25 to 85% by weight of a first polymer having a melting point of 55 to 95 ° C comprising at least one copolymer of ethylene and octene-1; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one copolymer not modified or modified with ethylene anhydride and a vinyl ester or an alkyl acrylate; wherein the first and second polymers have a combined weight percentage of at least

50% or by weight, said percentage by weight based on the total weight of the first, second and third polymers, and said core layer is disposed between the intermediate and outer protective layers.

86.- A process for making a biaxially stretched, heat-shrinkable film, comprising: extruding a melt-plastified primary tube comprising from 25 to 85% by weight of a first polymer having a melting point of 55 to 95 ° C comprising at least one ethylene and octene-1 copoiimer; from 5 to 35% by weight of a second polymer having a melting point of 115 to 128 ° C comprising at least one copolymer of ethylene and at least one α-olefin; and from 10 to 50% by weight of a third polymer having a melting point of 60 to 110 ° C comprising at least one ethylene copolymer and a vinyl ester or an alkyl acrylate; wherein the first and second polymers have a combined weight percentage of at least 50% by weight, said percentage by weight based on the total weight of the first, second and third polymers; cooling said primary tube; reheat the cooled tube to a drag point temperature of 68 to 88 ° C; biaxially stretching the tube to a circumference of at least two and a half times the circumference of the primary tube, and cooling the biaxially stretched tube to form a heat-shrinkable, biaxially stretched film.

87. A process according to claim 86, wherein said drag point temperature is 65 to 79 ° C.

88.- A process according to claim 86, wherein the resulting film has a maximum water hammer drilling force of at least 65 Newtons, a total energy absorption of at least 0.50 Joules, and a shrink value at 90 ° C of at least 45% in at least one of the directions, of the machine and crosswise.

89.- A process according to claim 86, wherein the mixture comprises at least 50% of the first polymer. 90.- A process according to claim 86, wherein the resulting film has a maximum water hammer drilling force of at least 90 Newtons, a total energy absorption of at least 0.

90 Joules, and a shrinkage value of 90 ° C of at least 50% in both directions, machine and transverse.

91.- A process according to claim 86, wherein a multilayer primary pipe is made through coextrusion or lamination by coating and said resulting biaxially stretched film comprises: a heat sealing surface layer comprising a polymer selected from the group consisting of: (a) at least 50% by weight 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% by weight, (b) at least 50% by weight of a copolymer of ethylene and at least one α-olefin selected from the group which consists of propylene, butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm3; an intermediate layer; a core layer comprising at least 80% by weight (based on the weight of the third layer) of at least one copolymer of: EVOH; or vinylidene chloride with from 2 to 20% by weight (based on the weight of the copolymer) of vinyl chloride or methyl acrylate; and an outer protective surface layer; wherein at least one of the outer intermediate and protective layers comprises the mixture defined in claim 77, and the core layer is disposed between the outer and outer protective layers, and the film has a maximum water hammer drilling force of at least 100 Newtons, a resistance to hot water drilling of at least 100 seconds at 95 ° C and a hot water seal resistance of at least 200 seconds at 95 ° C.

92.- A process according to claim 86, wherein at least one of the first and second polymers comprises: an ethylene terpolymer, butene-1 and octene-1; or ethylene, hexene-1 and octene-1.

93.- A biaxially stretched, heat shrinkable multilayer film for processing and packaging food having at least four layers, comprises: a first heat sealing surface layer comprising a polymer or mixture of polymers selected from the group consisting of of: (a) at least 50% is weight 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% by weight, and (b) at least 50% by weight of an ethylene copolymer and at least one α-olefin selected from the group consisting of propylene. butene-1, methylpentene-1, hexene-1, octene-1 and mixtures thereof having a melting point of at least 105 ° C and a density of at least 0.900 g / cm 3; a second polymeric layer comprising a mixture of: (a) 25 to 85% of a first polymer having a melting point of 55 to 95 ° C comprising a copolymer of ethylene and octene-1; (b) from 5 to 35% of a second polymer having a melting point of 115 ° C to 128 ° C comprising a copolymer of ethylene and at least one C4-C8 α-olefin; and (c) from 10 to 50% of a third polymer having a vinyl ester and a melting point of 60 to 110 ° C comprising a copolymer of ethylene with a vinyl ester (preferably from 4 to 18% by weight of said copolymer ), acrylic acid, methacrylic acid, or alkyl acrylate (preferably from 4 to 30% alkyl acrylate by weight of said copolymer), wherein the first and second copolymers have a weight percentage

15 combined of at least 50% by weight, said percentage by weight based on the total weight of the first, second and third polymers; a third layer comprising at least 80%) by weight (based on the weight of said third layer) of EVOH or at least

20 a vinylidene chloride copolymer with from 2 to 20% by weight (based on the weight of said copolymer) of vinyl chloride or methyl acrylate; and a fourth polymeric layer comprising, (a) from 10 to 85% of a first copolymer of ethylene and at least one α-olefin of C3

___) C8, said first copolymer having a melting point of 55 to 98 ° C, (b) from 5 to 60% of a second copolymer of ethylene and at least one C4-C8 α-olefin, said second polymer having a melting point of 115 ° C to 128 ° C, and (c) from 0 to 50% of a third copolymer having a melting point of 60 to 110 ° C of ethylene with a vinyl ester (preferably 4 to 18% ), acrylic acid (preferably 4 to 30%), methacrylic acid, or alkyl acrylate, wherein the first and second copolymers have a combined weight percentage of at least 50% by weight, said percentage by weight based on the total weight of the layer; and wherein the film has a shrinkage value at 90 ° C of at least 40%) in at least one of the directions, of the machine and transverse, and said film has a tensile seal strength of at least 400 g. / cm at 88 ° C.

94.- A film according to claim 93, wherein said film has a maximum water hammering force of at least 70 Newtons.

95.- A film according to claim 93, wherein the film has a maximum water hammering force of at least 110 Newtons.

96.- A film according to claim 93, wherein the film has a resistance to drilling by hot water of at least 25 seconds at 95 ° C.

97.- A film according to claim 93, wherein the film has a resistance to drilling by hot water of at least 40 seconds at 95 ° C

98. - A film according to claim 93, wherein the film has a resistance to drilling by hot water of at least 100 seconds at 95 ° C.

99.- A film according to claim 93, wherein the film has a hot water seal resistance of at least 200 seconds at 95 ° C.

100. A film according to claim 93, wherein the film has a hot water seal resistance of at least 300 seconds at 95 ° C.

101. A film according to claim 93, wherein said melting point of the first heat sealing surface layer polymer (b) is at least 115 ° C.

102.- A film according to claim 93, wherein the film has a thickness of less than 175 microns.

103. A film according to claim 93, wherein the film has a turbidity value of less than 10% and a brightness at 45 ° of at least 70 Hunter units.

104. A film according to claim 93, wherein the film has an oxygen transmission rate of less than 45 cm3 / m2 for 24 hours at 1 atmosphere at 23 ° C.

105. A film according to claim 93, wherein the first copolymer of at least one of the second and fourth layers has a density of less than 0.900 g / cm3.

106. A film according to claim 93, wherein the first copolymer of both the second and fourth layers has a density of less than 0.900 g / cm.

107. A film according to claim 93, wherein the third copolymer in both the second and fourth layers comprises from 4 to 18% (by weight of said copolymer) of a vinyl ester or from 4 to 30% of an alkyl acrylate.

108.- A film according to claim 93, wherein the fourth polymer layer comprises a mixture of: (a) 25 to 85%) of a first polymer having a melting point of 55 to 95 ° C comprising a copolymer of ethylene and octene-1; (b) from 5 to 35% of a second polymer having a melting point of 115 ° C to 128 ° C comprising a copolymer of ethylene and at least one α-olefin of C-C8; and (c) from 10 to 50% of a third polymer having a melting point of 60 to 110 ° C comprising a copolymer of ethylene with a vinyl ester, acrylic acid, methacrylic acid, or alkyl acrylate, wherein the first and second copolymers have a combined weight percentage of at least 50% by weight, said percentage by weight based on the total weight of the first, second and third polymers.

109. A film according to claim 93, wherein the melting point of the first heat sealing surface layer polymer (b) is at least 115 ° C.

110. A film according to claim 93, wherein the ethylene-octene-1 copolymer is present in an amount of 50 to 85% of the layer.

111. A film according to claim 93, wherein the copolymer of ethylene and octene-1 is present in an amount of 25 to 50%.