BACKSEAMED CASING AND PACKAGED PRODUCT INCORPORATING SAME

Abstract: A heat-shrinkable backseamed casing film (44) comprises a first layer (46), a second layer (48) and a third layer (50), with the first and third layers being outer layers and the second layer being between the first layer and the third layer. The first outer layer (46) serves as an inside casing layer, and comprises polyolefin; the second layer (48) comprises polyester and/or polyamide; the third layer (50) serves as an outside casing layer and comprises polyolefin, polystyrene and/or polyamide. The second layer (48) has a thickness of at least about 5 % of a total thickness of the heat-shrinkable casing film. Alternatively, the first layer (46) comprises polyolefin and has a surface energy level of less than about 34 dynes/cm; the second layer (48) comprises a polyamide having a melting point of at least 300 DEG F; and the third layer (50) comprises polyolefin, polystyrene and/or polyamide. A package comprises a cooked meat product within the backseamed casing. The second layer (48) of the casing film prevents or reduces necking down on the forming shoe during backseaming. The backseamed casing is especially useful for cook-in applications.

Description: BACKSEAMED CASING AND PACKAGED PRODUCT INCORPORATING SAME Cross-Reference to Related Application This appbcation is a continuation-in-part of copending U.S.S.N. 08/951,245, filed in the U.S. Patent and Trademark Office on September 25, 1992, in the name of R.K. Ramesh. Field of the Invention The present invention relates generally to multilayer films, and particularly to multilayer films suitable for use in backseamed casings for packaging meat products. The present invention is particularly related to backseamed casings suitable for packaging protein-containing food products in which the film adheres to the food product, and especially to those having a relatively high protein content, also called 'low-fat' food products, such as poultry, ham, roast beef, etc The present invention is also directed to packages. Background of the Invention Processed meat products, such as poultry and ham, are often packaged in a flexible, thermoplastic, heat-shrinkable film tubing commonly referred to as a casing. Although some casings have a lay-flat width of 6-20 inches, some products, such as ham, etc., are quite often packaged in a casing of smaller lay-flat width, e.g., a width of from about 3 to 6 mches. Such casings often may need to have a precisely-controlled width, because the packages are stated as havmg a given weight, which is uniform among packages, and the packages also have product sliced at uniform intervals, with each package contammg the same number of slices. Thus, variations in casing width can result in both an undesirable degree of variation in overall package weight, as well as an undesirable degree of variation in slice weights. Thus, there is a need for a casing havmg a small and uniform diameter However, it is relatively difficult to make a narrow width, heat-shrinkable seamless casing havmg a precisely controlled width, usmg a commercially feasible process. Consequently, there is a need for some other process for making a narrow-width, precisely-width-controlled casing Some backseamed casmgs are known to be casings of small and uniform diameter. Small-diameter backseamed casmgs are known which have a precisely controlled cas g width, i.e., a lay-flat width independent of film extrusion variations. In the production of backseamed casmgs (e.g., usmg a backseaming machine such as a Nishibe HSP-250-SA backseaming machine obtamed from Nishibe Kokai Co. Ltd. of Nagoya, Japan), a flat sheet of film is folded longitudmally by passage over a "forming shoe". A formmg shoe is a part of the backseaming machine which the film is passed under and around, i.e., so that the initially flat film is reconfigured as a tube, havmg a longitudmal overlap and seal therealong (lap-sealed backseamed casing), or with film longitudmal edges abutted against one another (butt-sealed backseamed casmg), with the width of the tube being determmed by the circumference of the formmg shoe. A longitudmal lap or butt seal is then appbed while the film is between the forming shoe and a sealmg device, resultmg in a lap-sealed backseamed casmg, or a butt-sealed backseamed casing Butt-seal casings utilize a butt-seal tape sealed to the mside or the outside surface of the casmg film, along both sides of the abuttmg longitudmal seam of the casing film, ln either event, the resultmg tubmg, termed a "backseamed casmg," is sealed or cbpped at its ends after bemg filled with a meat product. For some uses, the meat product is thereafter cooked while the backseamed casmg. It would be desirable to provide a highly uniform, small diameter backseamed casmg suitable for cook-m end use, the casmg bemg made from a film which adheres to high-protem meat products, such as certam grades of ham and turkey. Of course, it would also be desirable to provide the backseamed casmg with a backseam seal which survives the cook-m process. lt is known that a polar surface is needed for adhesion of a film to a meat product. Adhesion of the film to the meat is frequently needed m order to prevent "purge", i.e., "cook-out", which can occur durmg the cookmg of the meat packaged m the film if the film does adhere to the meat durmg cook-m. A polar film surface can be provided by usmg: (a) polar resm m the film layer m contact with the meat, and/ or (b) surface modification, such as corona treatment, of the film surface m contact with the meat. Typically, polar polymers used for meat adhesion mclude: ethylene/ unsaturated acid copolymer, anhydride-containing polyolefin, and polyamide. Film-to-meat adhesion is known to be enhanced by corona treatment of the surface of the film to which the meat is to be adhered However, corona treatment alters the film surface m a manner which can, on occasion, result m an inferior seal, i.e., a seal more likely to leak than if the film surface is not corona treated. This "leaky seal problem" can be avoided by "buffing off the corona treatment m the area of the seal, so that the advantageous effects of the corona treatment, i.e., greater meat adhesion, can be retamed on the majority of the meat-contact surface of the film, while at the same time avoidmg, in the area of the seal, the seal-quality problem caused by the corona treatment. However, the buffmg step is undesirable, as it is an additional processmg step which renders the casmg manufacture more complex and costly. Furthermore, the buffmg step is frequently mconsistent. Smce the backseammg process is generally carried out after the corona treatment, shrinkage of the film agamst the formmg shoe (durmg backseammg), coupled with forwardmg the film over the formmg shoe after shrmkage, results m the rubb g of the film agamst the formmg shoe edges. This rubbing reduces or destroys corona treatment, at least in the area in which the film rubs agamst the formmg shoe. As a result, backseamed casmgs contammg corona treated films can exhibit purge at the locations at which the film rubs agamst the forming shoe. Furthermore, corona treatment can be mconsistent, at least with respect to prevention of purge for products havmg an mtermediate protem content. It would be desirable that the casmg film has a consistent and adequate level of protem/ meat adhesion. As a result, it would be desirable to provide a corona-treatment-free backseamed casmg which prevents purge from products relatively high m protem, where the adhesion of the casmg film to the meat product is uniform over the film. Thus, it would be desirable to provide a backseamed casmg of small and uniform diameter which is heat-shrmkable and suitable for cook-m end use, exhibits good purge-resistance and good seal strength, can be economically manufactured, does not produce significant meat pull-off upon bemg stripped from a cooked meat product, and which provides a good oxygen barrier, m order to provide good shelf life to the cooked meat product. Heat-shrmkable films havmg an outer layer capable of providmg meat adhesion, which are otherwise suitable for use as backseamed casmgs, have been found to have the undesirable characteristic of neckmg down on the forming shoe durmg the backseammg process. The neckmg down on the formmg shoe is believed to be due to shrmkage of the film durmg the heat sealmg step of the backseammg operation. That is, the heat sealmg step can cause substantial film shrmkage an area extendmg outward from the seal, causmg the edges of the casmg to neck down on the formmg shoe. The result of neckmg down is a casmg havmg "ruffled edges", i.e., visible nonumformities in the casmg. In an extreme case, neckmg down results m the rupture of the film, as the shrinking of the film agamst the forming shoe places so much force on the film that the film ruptures. Thus, it would be desirable to provide a casmg film which does not shrmk down (i.e., "neck down") on the formmg shoe durmg the backseammg operation. Summary of the Invention It has been discovered that the presence of an mner layer compnsmg a polyamide, preferably a high modulus polyamide, provides, if the polyamide layer makes up at least 5 percent of the total film thickness, a film which does not neck down on the forming shoe dur g thp backseaming operation Although the reasons why the inner polyamide layer prevent neckmg down on the formmg shoe are not currently known with certamty, it is believed that various factors, mcludmg heat transfer, shrmk characteristics, etc. brmg about the discovered advantage of not neckmg down on the formmg shoe. Furthermore, the inner polyamide layer also helps to provide a better quabty casmg film by making the casmg film easier to orient, facibtahng faster backseaming speeds, and also imparting enhanced seal strength, toughness, pin-hole resistance and elastic recovery to the casmg film. It has also been discovered that tn the case of anhydride-containing polyolefin, if the anhydπde functionality is of the order of 1 weight percent or less, the polymer often does not provide adequate meat adhesion to lntermediate-protein-containing meat products, or low-protein-containing meat products. On the other hand, polymers such as polyamide can, m some instances, provide too much meat-adhesion and tend to pull meat off durmg unpackagmg of the meat, thereby destroying the smooth surface desired upon separatmg the casmg film from the cooked meat product, and also contributing to yield loss. Polyamides are also relatively expensive polymers. Thus, it would be desirable to provide a casmg havmg a film providmg adequate meat adhesion to prevent purge, while bemg able to strip the film from the meat without meat pull-off due to too much adhesion of the film to the cooked meat product However, it has been found that adequate meat adhesion can be obtamed usmg an anhvdride-contammg polyolefin havmg an anhydπde functionality of at least 1 percent. As a first aspect, the present mvention is directed to a backseamed casmg compnsmg a heat-shrmkable casmg film. The heat shrmkable film comprises a first layer, a second layer, and a third layer, with the first and third layers bemg outer layers and the second layer bemg between the first layer and the third layer. The hrst outer layer serves as an mside casmg layer, and comprises a hrst polyolefin. The hrst polyolefin comprises at least one member selected from the group consistmg of: (1) ethylene/ unsaturated acid copolymer, propylene/ unsaturated acid copolymer, and butene/ unsaturated acid copolymer, wherem the unsaturated acid is present m an amount of at least 4 weight percent, based on the weight of the copolymer; and (n) anhydnde-contammg polyolefin compnsmg an anhydπde-functionabty, wherem the anhydπde functionality is present m an amount of at least 1 weight percent, based on the weight of the anhydnde-contammg polyolefin. The second layer comprises at least one member selected from the group consistmg of polyester, and first polyamide. The third layer serves as an outside casmg layer, and comprises at least one member selected from the group consistmg of second polyolefm, polystyrene, and second polyamide. The second layer has a thickness of at least about 5% of a total thickness of the heat-shrmkable casing film. In the first layer, the first polyolefm preferably comprises an ethylene/ unsaturated acid copolymer havmg an unsaturated acid mer present an amount of at least 6 percent, based on the weight of the ethylene/ unsaturated acid copolymer; more preferably, the unsaturated acid is present in an amount of at least 9 weight percent, based on the weight of the ethylene/ unsaturated acid copolymer. The first layer preferably further comprises a third polyolefm compnsmg at least one member selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer. More preferably, the third polyolefm compnses at least one member selected from the group consisting of ethylene/ alpha-olefin copolymer, propylene/ alpha-olefin copolymer, butene/alpha- olefm copolymer, ethylene/unsaturated acid copolymer, and ethylene/ unsaturated ester copolymer. Still more preferably, the third polyolefm comprises at least one member selected from the group consisting of Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/ butene copolymer. Yet still more preferably, the third polyolefm comprises LLDPE. The second layer preferably comprises the hrst polyamide. More preferably, the first polyamide comprises at least one member selected from the group consistmg of polyamide 6, polyamide 66, polyamide 9, polyamide 10, polyamide 11, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, and copolymers thereof. Still more preferably, the first polyamide comprises at least one member selected from the group consisting of polyamide 6, polyamide 66 and copolyamide 6/66. The third layer preferably comprises the second polyolefin. Preferably, the second polyolefm has a vicat softenmg point of at least 80°C; more preferably, at least 90°C; and still more preferably, at least 100°C The softenmg pomt of the second polyolefin has to be high enough to undergo cook-m without causmg the seals to fail (if the polyolefm is used in a seal layer). In an alternative preferred embodiment, the third layer comprises the second polyamide, with or without the second polyolefin, more preferably, as an alternative to the second polyolefm. Preferably, the casmg film further comprises a fourth layer, the fourth layer being an mner layer servmg as an 0 2 -barπer layer, the fourth layer compnsmg at least one member selected from the group consistmg of ethylene/ vmyl alcohol copolymer, polyvinylidene chloride copolymer, polyethylene carbonate copolymer and polyamide. Preferably, the second layer and the fourth layer are directly adhered. Preferably, the casmg film further comprises a fifth layer and a sixth layer, wherem: (a) the fifth layer is between the first layer and the second layer, and the sixth layer is between the second layer and the third layer; (b) the fifth layer comprises at least one member selected from the group consistmg of fourth polyolefm, polystyrene and polyurethane; and (c) the sixth layer comprises at least one member selected from the group consisting of fifth polyolefin, polystyrene and polyurethane. Preferably, the fifth layer is a tie layer and comprises at least one member selected from the group consistmg of modified ethylene/ alpha-olefin copolymer, modified ethylene/ unsaturated ester copolymer, and modified ethylene/ unsaturated acid copolymer. Preferably, the sixth layer is a tie layer and comprises at least one member selected from the group consisting of modified ethylene/ alpha-olefin copolymer, modified ethylene/ unsaturated ester copolymer, and modified ethylene/ unsaturated acid copolymer. Preferably, the casmg film further comprises- (a) a seventh layer, the seventh layer bemg between the first layer and the second layer, the seventh layer compnsmg a sixth polyolefin; and (b) an eighth layer, the eighth layer being between the second layer and the third layer, the eighth layer compnsmg a seventh polyolefin. Preferably, a ratio of: (a) a sum of the thickness of the first layer and the fifth layer; to (b) a sum of the thickness of the third layer and the sixth layer is from about 0.7:1 to 1.3:1. Preferably the second layer has a thickness of from about 5 to 20 percent, based on a total thickness of the multilayer film; and preferably, the fourth layer has a thickness of less than about 15%, based on a total thickness of the multilayer film. Preferably, the heat-shrmkable casmg film has biaxial orientation. Preferably, the casmg film has a free shrmk, at 185°F, of at least 10% m at least one direction. Preferably, at least a portion of the casmg film comprises a crosslmked polymer network. The backseamed casmg accordmg to the present mvention can be either a lap- sealed backseamed casmg or a butt-sealed backseamed casmg. A butt-sealed casmg compnses both a casmg film and a butt-seal tape film. Preferably, the butt-seal tape film comprises at least one member selected from the group consisting of polyolefm, polyamide or polystyrene, and preferably the butt-seal tape film is heat-shrmkable. As a second aspect, the present mvention is directed to a package compnsmg a cooked meat product withm a backseamed casmg. The backseamed casmg is accordmg to the first or third aspects of the present invention described herem, and the cooked meat product is adhered to a meat-contact surface of the casmg film. Preferably, the meat product comprises at least one member selected from the group consistmg of poultry, ham, beef, lamb, fish, liver sausage, bologna, mortadella, braunschweiger, goat, and horse; more preferably, poultry, ham, beef, lamb, fish, liver sausage, bologna, and mortadella. Preferably, the meat-contact surface of the first layer is corona treated, and the meat product compnses at least one member selected from the group consisting of bver sausage, bologna and mortadella. Preferably, the outside surface of the casmg film is also corona treated. Preferably, the meat comprises from 0-30% fat, more preferably from 1-15% fat, still more preferably from 2-10% fat, and yet still more preferably from 3-7% fat. Preferred backseamed casmgs for use the package mclude the preferred backseamed casmgs in accordance with the present invention. If a non-corona treated backseamed casmg (or equivalent thereof) accordmg to the first aspect of the present aspect is used, the cooked meat product preferably comprises at least one member selected from the group consisting of turkey, ham, beef, and fish, wherein the meat product comprises fat m an amount of from about 2 to 10 weight percent, preferably 3 to 8 percent, and more preferably from about 4 to 6 percent. If a corona treated backseamed casing (or equivalent thereof) accordmg to the first aspect of the present aspect is used, the cooked meat product preferably comprises at least one member selected from the group consistmg of ham, beef, liver sausage, bologna, mortadella, horse, and goat; more preferably, the meat product comprises at least one member selected from the group consistmg of ham, liver sausage, bologna, and mortadella; preferably, the cooked meat product comprises fat m an amount of from about 3 to 40 weight percent, preferably 5 to 30 percent, and more preferably from about 10 to 15 percent. If a non-corona treated backseamed casmg (or equivalent thereof) accordmg to the third aspect of the present aspect is used, the cooked meat product preferably comprises at least one member selected from the group consisting of turkey and fish, wherem the meat product comprises fat m an amount of from about 1 to 10 weight percent, preferably 2 to 6 percent, and more preferably from about 3 to 5 percent As a third aspect, the present mvention is directed to a backseamed casmg compnsmg a heat-shrmkable casmg film compnsmg: (A) a first outer layer servmg as an mside casmg layer, the first outer layer compnsmg a first polyolefm, the first outer layer having a surface energy level of less than about 34 dynes/cm; (B) a second layer comprising a first polyamide having a meltmg pomt of at least 300°F; (C) a third layer serving as an outside casmg layer, the third outer layer compnsmg at least one member selected from the group consistmg of a second polyolefin, polystyrene and second polyamide. The second layer is between the hrst layer and the third layer, and the second layer has a thickness of at least about 5% of a total thickness of the heat- shrmkable casmg film. In a lap-sealed backseamed casmg accordmg to this third aspect of the present invention, preferably the first polyolefm has a vicat softenmg pomt of at least 70°C, more preferably at least 80°C, m order to provide a desired level of seal strength However, m a butt-sealed backseamed casmg accordmg to this third aspect of the present mvention, the vicat softenmg pomt of the hrst polyolefm may be less critical. More preferably, the first polyolefm is a relatively non-polar polymer, preferably havmg a surface energy level of less than 32 dynes/ cm. Brief Descπption of the Drawmgs Figure 1 illustrates a cross-sectional view of a lap-seal backseamed casmg m accord with the present invention. Figure 2 illustrates an enlarged cross-sectional view of a first preferred casmg film suitable for use m the lap-seal backseamed casing illustrated in Figure 1. Figure 3 illustrates an enlarged cross-sectional view of a second preferred casmg film suitable for use m the lap-seal backseamed casmg illustrated in Figure 1. Figure 4 illustrates an enlarged cross-sectional view of a third preferred casmg film suitable for use m the lap-seal backseamed casmg illustrated in Figure 1. Figure 5 illustrates a cross-sectional view of a butt-seal backseamed casmg m accord with the present mvention. Figure 6 illustrates an enlarged cross-sectional view of a first preferred casing film suitable for use in the butt-seal backseamed casmg illustrated in Figure 5 Figure 7 illustrates an enlarged cross-sectional view of a first preferred butt-seal tape film suitable for use in the butt-seal backseamed casmg illustrated in Figure 5. Figure 8 illustrates a schematic view of a process for making a preferred heat- shrinkable casmg film and/ or butt-seal tape film, for use m a backseamed casmg m accord with the present mvention. Figure 9 illustrates a perspective view of a first package accordmg to the present invention. Figure 10 illustrates a perspective view of a second package accordmg to the present invention. Detailed Descπption of the Invention As used herem, the term "package" and the phrase "packaged product" refer to an article m which a product (preferably a food product, more preferably a meat- containing food product) is encased m a packagmg film. As used herem, the phrase "lay-flat film" refers to a film that has been extruded as a wide, thin-walled, circular tube, usually blown, cooled, then gathered by convergmg sets of rollers and wound up in flattened form. The phrase "lay-flat width", refers to half of the circumference of the mflated film tube. As used herem, the phrase "backseamed casmg" refers to any casmg (a tubular film) having a longitudmal seal For example, a lap-seal backseamed casmg can be formed: by foldmg a film strip over a formmg shoe of a horizontal sealmg machme, and applymg a longitudmal seal thereto where the film overlaps, e.g. usmg a Nishibe Model HSP-250-SA sealmg machme; or a Totani Model FD-350C sealmg machme obtamed from Totani Giken Kogyo Co., Ltd., of Kyoto, Japan; or, by foldmg a film stπp over a formmg shoe of a vertical form fill and seal machme, and applymg a longitudmal seal thereto where the him overlaps, e.g., usmg an ONPACK-2002 (TM) sealmg machme, obtamed from Orihiro Company, Ltd., of Tomioka City, Japan. A lap-sealed casmg could also use a tape-film between the areas where the film overlaps, to facilitate sealmg. A butt-seal backseamed casmg can be formed: by foldmg a film stπp over a forming shoe of a horizontal sealing machme, with opposmg longitudmal edges abuttmg one another, i.e., m non-overlappmg relation to one another; and thereafter, by applymg a butt-seal tape film over the abuttmg edges, followed by sealmg the butt-seal tape film across and along the abuttmg edges, so that a sealed tube is formed. For the backseamed casmgs accordmg to the present mvention, the composition m the second layer can be present either in one or more layers of the casmg film If the composition is present m more than one layer, the layers are preferably so positioned as to provide reasonable symmetry to the film, thus providmg a relatively flat, curl-free film. Preferably, the backseamed casmg accordmg to the present mvention has a lay- flat width of at less than about 10 mches; more preferably, from about 1 to 10 mches, still more preferably, from about 2 to 8 inches; yet still more preferably, from about 3 to 7 mches, and yet still even more preferably, from about 4 to 6 mches. lt is believed that for any given film to be backseamed, the problem of neckmg down on the forming shoe becomes worse as the lay-flat width of the casmg is reduced. Heat-shrmkable multilayer films of the mvention preferably have a substantially symmetrical cross-section, with respect to both layer thickness and layer chemical composition, in order to provide the film with relatively low curl. For example, for a 3- layer casmg film accordmg to the backseamed casmg of the present mvention, the ratio of a/b is preferably from about 0.7-1.3, more preferably from about 0.8-1.2, and even more preferably from about 0.9-1.1; wherem, 'a' is the thickness of the hrst outer layer and 'b' is the thickness of the second outer layer For a preferred six-layer casmg film accordance with the backseamed casmg of the present mvention, the ratio of the sums of the thickness of the hrst layer plus the fifth layer to the sum of the second layer plus the sixth layer is preferably from about 0.7-1.3; more preferably from about 0.8 to 1.2; and still more preferably, from about 0.9 to 1.1. The heat-shrmkable casing film accordmg to the present mvention preferably has a free shrmk of from about 5-70 percent m one or both directions (i.e., longitudinal direction "L", also referred to as "machme direction", and transverse direction, "T") at 185° F, determined accordmg to ASTM D 2732; more preferably, from about 10-50 percent at 185 C F; still more preferably, from about 15-35 percent at 185°F. Preferably, the casmg film is biaxially oriented, and preferably the film has a free shrmk, at 185 C F, of at least 10 percent m each direction (L and T); more preferably, at least 15 percent m each direction. Preferably, the casing film has a total free shrink of from about 30 to 50 percent (L+T) at 185°F. For a butt seal backseamed casmg, the butt seal tape film can be either a heat-shrmkable film or a non-heat-shrinkable film. As used herem, the term "sealed" refers to any and all means of closmg a package, such as heat sealing via hot air and/ or heated bar, ultrasonic, radio frequency sealmg, and even the use of cbps on, for example, a shirred casmg, etc. As used herem, the phrase "heat seal" refers to a seal formed by contacting the film with a hot element, e.g., usmg a hot bar, hot wire, hot air, etc. Preferably, the seal in the backseamed casmg accordmg to the present mvention has a seal strength of at least 3 pounds per mch (as measured on an Instron, per ASTM F88); more preferably, from about 5 to 100 lb/in; still more preferably, from about 7 to 50 lb/ in; yet still more preferably, from about 10 to 30 lb/m; and yet still more preferably, from about 15 to 20 lb/in. As used herem, the phrase "butt seal" refers to a seal formed by butting opposmg film edges together and thereafter sealmg regions the vicinity of the abutted edges to a butt seal tape, as shown in Figure 5. As used herem, the phrase "lap seal" refers to a seal formed by lapping a film over itself to form a package by seabng an mside surface of the film to an outside surface of the film, as shown Figure 4. As used herem, the phrase "meat-contact layer", refers to a layer of a multilayer film which is in direct contact with the meat-containing product packaged the film. The meat- contact layer is an outer layer, in order to be in direct contact with the meat product. The meat-contact layer is an mside layer in the sense that in the packaged meat product, the meat-contact layer is the innermost film layer in direct contact with the food. As used herem, the phrase "meat-contact surface" refers to a surface of a meat-contact layer which is in direct contact with the meat the package. As used herem, the phrase "meat-adhesion", and "adhered", refer to maintaining direct contact between the meat surface and the meat-contact surface of the film, so that there is an absence of fat or a substanhal amount of free moisture, e.g., j uices emitted outside of the meat product, commonly referred to as "purge". In general, there is an absence of a substantial amount of free moisture if the level of free moisture is from about 0 to 2%, based on the weight of the meat product before cooking. Preferably the amount of free moisture is from about 0 to 1%, more preferably, 0 to 0.5%, and still preferably from 0 to 0.1 percent based on the weight of the meat product before cooking. As used herein, the phrase "cook-m" refers to the process of cooking a product packaged in a matenal capable of withstanding exposure to long and slow cooking conditions while contammg the food product, for example cooking at 57°C to 121°C (i.e, 135°F-250°F) for 2-12 hours, preferably 57°C to 95°C (i.e, 135°F-203°F) for 2-12 hours. Cook- in packaged foods are essenhally pre-packaged, pre-cooked foods which may be directly transferred to the consumer this form. These types of foods may be consumed with or without waπrung. Cook-in packaging mateπals mamtam seal integnty, and m the case of multilayer films are delamination resistant. Cook-m films may also be heat-shrmkable under cook-m conditions so as to form a tightly fitting package. Cook-m films preferably have a tendency for adhesion to the food product, thereby preventing "cook-out", i.e., "purge", which is the collection of juices between the outer surface of the food product and the meat- contact surface of the film, i.e., the surface in direct contact with the meat. Additional optional charactenstics of films for use in cook-m appbcations mclude delamination- resistance, low 0 2 permeabibty, heat-shπnkabibty representing about 20-50% biaxial shnnkage at about 85°C (185°F), and optical clanty. As used herem, "EVOH" refers to ethylene vmyl alcohol copolymer. EVOH mcludes saponified or hydrolyzed ethylene vmyl acetate copolymers, and refers to a vinyl alcohol copolymer havmg an ethylene comonomer, and prepared by, for example, hydrolysis of vmyl acetate copolymers, or by chemical reactions with polyvinyl alcohol. The degree of hydrolysis is preferably at least 50% and more preferably at least 85% As used herein, the term "barrier", and the phrase "bamer layer", as appbed to films and/ or film layers, is used with reference to the abibty of a film or film layer to serve as a bamer to O? As used herem, the term "lamination", and the phrase "laminated film", refer to the process, and resulting product, made by bonding together two or more layers of im or other matenals. Lamination can be accompbshed by jommg layers with adhesives, jommg with heat and pressure, corona treatment, and even spread coating and extrusion coating. The term laminate is also inclusive of coextruded multilayer films compnsmg one or more tie layers. As used herem, the term "onented" refers to a polymer-containing matenal which has been stretched at an elevated temperature (the onentation temperature), followed by bemg "set" in the stretched configuration by cooling the matenal while substantially retaining the stretched dimensions. Upon subsequently heatmg unrestrained, unannealed, oriented polymer-containing material to its onentation temperature, heat shnnkage is produced almost to the original unstretched, i.e., pre-oπented dimensions. More particularly, the term "oriented", as used herein, refers to oriented films, wherem the onentation can be produced in one or more of a vanety of manners. As used herem, the phrase "onentation ratio" refers to the multipbcation product of the extent to which the plastic film matenal is expanded several directions, usually two directions perpendicular to one another. Expansion in the machme direction is herem referred to as "drawing", whereas expansion in the transverse direction is herem referred to as "stretching". The degree of onentation is also referred to as the onentation ratio, or sometimes as the "racking ratio". As used herem, the term "monomer" refers to a relatively simple compound, usually contammg carbon and of low molecular weight, which can react to form a polymer by combmmg with itself or with other similar molecules or compounds. As used herem, the term "comonomer" refers to a monomer which is copolymerized with at least one different monomer m a copolymerization reachon, the result of which is a copolymer. As used herem, the term "polymer" refers to the product of a polymerization reachon, and is inclusive of homopolymers, copolymers, terpolymers, etc. In general, the layers of a film can consist essenhally of a smgle polymer, or can have still additional polymers blended therewith. As used herem, the term "homopolymer" is used with reference to a polymer resulting from the polymerization of a smgle monomer, i.e., a polymer consistmg essentiaby of a smgle type of repeating unit. As used herem, the term "copolymer" refers to polymers formed by the polymenzahon reachon of at least two different monomers For example, the term "copolymer" mcludes the copolymerization reaction product of ethylene and an alpha-olefin, such as 1 -hexene However, the term "copolymer" is also mclusive of, for example, the copolymerization of a mixture of ethylene, propylene, 1-hexene, and 1-octene. As used herem, the term "polymenzahon" is mclusive of homopolymenzahons, copolymenzahon5, terpolymenzations, etc., and mcludes all types of copolymenzahons such as random, graft, block, etc. ln general, the polymers, in the films used in accordance with the present mvention, can be prepared accordance with any suitable polymenzahon process, mcludmg slurry polymenzahon, gas phase polymenzahon, and high pressure polymenzahon processes. As used herem, the term "copolymerization" refers to the simultaneous polymerization of two or more monomers. As used herem, a copolymer identified in terms of a plurabty of monomers, e.g., "propylene/ethylene copolymer", refers to a copolymer in which either monomer copolymenzes m a higher weight or molar percent. However, the first bsted monomer preferably is polymerized in a higher weight percent than the second bsted monomer, and, for copolymers which are terpolymers, quadnpolymers, etc., preferably, the first monomer copolymenzes m a higher weight percent than the second monomer, and the second monomer copolymenzes a higher weight percent than the third monomer, etc. As used herem, terminology employmg a "/" with respect to the chemical identity of a copolymer (e.g., "an ethylene/ alpha-olefin copolymer"), identifies the comonomers which are copolymerized to produce the copolymer. Such phrases as "ethylene alpha-olefin copolymer" is the respective equivalent of "ethylene/ alpha-olefin copolymer." As used herem, the phrase "heterogeneous polymer" refers to polymenzahon reachon products of relahvely wide vanahon in molecular weight and relahvely wide vanahon in composihon distnbution, i.e., polymers made, for example, usmg conventional Ziegler-Natta catalysts. Heterogeneous polymers are useful vanous layers of the film used in the present mvenhon. Such polymers typicaUy contain a relahvely wide vanety of cham lengths and comonomer percentages. As used herem, the phrase "heterogeneous catalyst" refers to a catalyst suitable for use m the polymenzahon of heterogeneous polymers, as defmed above. Heterogeneous catalysts are comprised of several kmds of active sites which differ in Lewis acidity and stenc environment. Ziegler-Natta catalysts are heterogeneous catalysts. Examples of Ziegler- Natta heterogeneous systems mclude metal habdes activated by an organometalhc co¬ catalyst, such as titanium chlonde, optionally contammg magnesium chlonde, complexed to tnalkyl aluminum and may be found in patents such as U.S. Patent No. 4,302,565, to GOEKE, et. al., and U.S. Patent No. 4,302,566, to KAROL, et. al., both of which are hereby mcoφorated, m their entireties, by reference thereto. As used herem, the phrase "homogeneous polymer" refers to polymenzahon reachon products of relahvely narrow molecular weight distribution and relahvely narrow composihon distribution. Homogeneous polymers are useful in vanous layers of the multilayer film used the present mvenhon. Homogeneous polymers exhibit a relahvely even sequencmg of comonomers within a cham, the mirronng of sequence distribution in all chams, and the sim-lanty of length of all chams, and are typicaUy prepared usmg metaUocene, or other single-site type catalysis. More particularly, homogeneous ethylene/ alpha-olefin copolymers may be characterized by one or more methods known to those of skiU in the art, such as molecular weight distribution (M w /M n ), composihon distribution breadth mdex (CDBI), and narrow melting pomt range and single melt pomt behavior. The molecular weight distnbution (Mw/Mn), also known as polydispersity, may be determined by gel permeation chromatography. The homogeneous ethylene/ alpha-olefin copolymers useful this mvenhon wdl have a (M w /M n ) of less than 2.7. Preferably, the (M w /M n ) will have a range of about 1.9 to 2.5. More preferably, the (M w /M n ) wiU have a range of about 1.9 to 2.3. The composition distnbution breadth mdex (CDBI) of such homogeneous ethylene/ alpha-olefin copolymers wiU generally be greater than about 70 percent The CDBI is defined as the weight percent of the copolymer molecules havmg a comonomer content withm 50 percent (i.e., plus or minus 50%) of the median total molar comonomer content The CDBI of bnear polyethylene, which does not contain a comonomer, is defined to be 100% The Composihon Distnbution Breadth Index (CDBI) is determmed via the technique of Temperature Rising Eluhon Fractionation (TREF) CDBI determmation clearly distinguishes the homogeneous copolymers used in the present mvenhon (narrow composihon distribution as assessed by CDBI values generally above 70%) from heterogeneous polymers such as VLDPEs available commerciaUy which generally have a broad composihon distnbution as assessed by CDBI values generaUy less than 55%. The CDBI of a copolymer is readily calculated from data obtamed from techniques known in the art, such as, for example, temperature nsing elution -ractionation as described, for example, Wild et. al., j\ Poly. Sci. Poly. Phys. Ed., Vol. 20, p.441 (1982). Preferably, the homogeneous ethylene/ alpha-olefin copolymers have a CDBI greater than about 70%, i.e., a CDBI of from about 70% to 99%. In general, the homogeneous ethylene/alpha-olehn copolymers the multilayer films of the present mvenhon also exhibit a relahvely narrow meltmg pomt range, comparison with "heterogeneous copolymers", i.e., polymers havmg a CDBI of less than 55%. Preferably, the homogeneous ethylene/alpha-olehn copolymers exhibit an essenhaUy singular meltmg pomt charactenshc, with a peak meltmg pomt (T m ), as determined by Differential Scanning Colonmetry (DSC), of from about 60°C to 110°C Preferably, the homogeneous copolymer has a DSC peak T m of from about 90°C to 110°C As used herem, the phrase "essenhaUy smgle meltmg point" means that at least about 80%, by weight, of the material coπesponds to a smgle T m peak at a temperature within the range of from about 60°C to 110°C, and essenhally no substanhal fraction of the matenal has a peak melting pomt in excess of about 115°C, as determined by DSC analysis. DSC measurements are made on a Perkm Elmer System 7 Thermal Analysis System. Meltmg mformahon reported are second meltmg data, i.e., the sample is heated at a programmed rate of 10°C./mm. to a temperature below its critical range. The sample is then reheated (2nd meltmg) at a programmed rate of 10°C/mιn. A homogeneous ethylene/alpha-olehn copolymer can, in general, be prepared by the copolymerization of ethylene and any one or more alpha-olefin. Preferably, the alpha- olefin is a CvC 2 o a-monoolefin, more preferably, a C4-Q2 a-monooleftn, stib more preferably, a Cj-Cβ a-monoolefin. StiU more preferably, the alpha-olefin compnses at least one member selected from the group consistmg of butene-1, hexene-1, and octene-1, ι.e., 1-butene, 1- hexene, and 1-octene, respectively. Most preferably, the alpha-olefin compnses octene-1, and/or a blend of hexene-1 and butene-1. Processes for preparmg homogeneous polymers are disclosed m U.S. Patent No. 5,206,075, U.S. Patent No. 5,241,031, and PCT International Appbcation WO 93/03093, each of which is hereby mcoφorated by reference thereto, in its entirety. Further details regarding the production and use of one genus of homogeneous ethylene/alpha-olehn copolymers are disclosed in U.S. Patent No. 5,206,075, to HODGSON, Jr., U.S Patent No. 5,241,031, to MEHTA; PCT Internationai Pubhcation Number WO 93/03093, in the name of Exxon Chemical Company; PCT International Pubbcahon Number WO 90/03414, in the name of Exxon Chemical Patents, Inc., all four of which are hereby incoφorated in their entireties, by reference there. S U another genus of homogeneous ethylene/alpha-olehn copolymers is disclosed m U.S. Patent No. 5,272,236, to LAI, et. al., and U.S. Patent No. 5,278,272, to LAI, et. al., both of which are hereby mcoφorated m their entireties, by reference thereto. As used herem, the term "polyolefm" refers to any polymerized olefin, which can be bnear, branched, cycbc, abphahc, aromatic, substituted, or unsubstituted. More specificaUy, included m the term polyolefin are homopolymers of olefins, copolymers of olefins, copolymers of an olefin and an non-oleπnic comonomer copolymenzable with the olehn, such as vmyl monomers, modihed polymers thereof, and the bke. Specific examples mclude polypropylene homopolymers, polyethylene homopolymers, poly-butene, propylene/ alpha-olefin copolymers, ethylene/alpha-olehn copolymers, butene/ lpha-olehn copolymers, ethylene/ vmyl acetate copolymers, ethylene/ ethyl acrylate copolymers, ethylene/ butyl acrylate copolymers, ethylene/ methyl acrylate copolymers, ethylene/ aery be acid copolymers, ethylene/ methacry be acid copolymers, modihed polyolefin resms, ionomer resms, polymethylpentene, etc. The modihed polyolefm resms mclude modified polymers prepared by copolymerizing the homopolymer of the olehn or copolymer thereof with an unsaturated carboxyhc acid, e.g., maleic acid, fumanc acid or the like, or a denvahve thereof such as the anhydnde, ester or metal salt or the like. It could also be obtamed by incoφorating mto the olefin homopolymer or copolymer, an unsaturated carboxylic acid, e.g., maleic acid, fumaric acid or the bke, or a denvahve thereof such as the anhydride, ester or metal salt or the like As used herem, terms identifying polymers, such as "polyamide", "polyester", "polyurethane", etc., are mclusive of not only polymers compnsmg repeating units derived from monomers known to polymerize to form a polymer of the named type, but are also mclusive of comonomers, denvahves, etc., which can copolymenze with monomers known to polymerize to produce the named polymer. Denvahves also mclude ionomers of the polymer(s). For example, the term "polyamide" encompasses both polymers compnsmg repeahng units denved from monomers, such as caprolactam, which polymerize to foπn a polyamide, as weU as copolymers derived from the copolymenzahon of caprolactam with a comonomer which when polymerized alone does not result the formahon of a polyamide. Furthermore, terms identifying polymers are also mclusive of "blends" of such polymers with other polymers of a different type. As used herem, the phrase "anhydride funchonahty" refers to any form of anhydnde funchonahty, such as the anhydnde of maleic acid, fumaric acid, etc., whether blended with one or more polymers, grafted onto a polymer, or copolymerized with a polymer, and, in general, is also mclusive of denvahves of such funchonabhes, such as acids, esters, and metal salts derived therefrom. As used herem, the phrase "modified polymer", as weU as more specific phrases such as "modified ethylene vmyl acetate copolymer", and "modified polyolefin" refer to such polymers havmg an anhydride functionabty, as defined immediately above, grafted thereon and/ or copolymerized therewith and/ or blended therewith. Preferably, such modihed polymers have the anhydnde functionabty grafted on or polymerized therewith, as opposed to merely blended therewith. As used herem, the phrase "anhydπde-modihed polymer" refers to one or more of the followmg: (1) polymers obtamed by copolymerizing an anhydnde-contammg monomer with a second, different monomer, and (2) anhydπde grafted copolymers, and (3) a mixture of a polymer and an anhydnde-contammg compound. As used herem, the phrase "ethylene alpha-olefin copolymer", and "ethylene/alpha- olehn copolymer", refer to such heterogeneous matenals as bnear low density polyethylene (LLDPE), and very low and ultra low density polyethylene (VLDPE and ULDPE); and homogeneous polymers such as metaUocene catalyzed polymers such as EXACT (TM) matenals suppbed by Exxon, and TAFMER (TM) materials suppbed by Mitsui Petrochemical Coφoration. These materials generaUy mclude copolymers of ethylene with one or more comonomers selected from Q to Cm alpha-olefins such as butene-1 (i.e., 1- butene), hexene-1, octene-1, etc. in which the molecules of the copolymers compnse long chams with relahvely few side cham branches or cross-linked structures This molecular structure is to be contrasted with convenhonal low or medium density polyethylenes which are more highly branched than their respective counterparts. LLDPE, as used herem, has a density usuaUy in the range of from about 0.91 grams per cubic centimeter to about 0.94 grams per cubic cenhmeter. Other ethylene/alpha-olehn copolymers, such as the long cham branched homogeneous ethylene/alpha-olehn copolymers available from the Dow Chemical Company, known as AFFINITY (TM) resms, are also included as another type of ethylene alpha-olefin copolymer useful in the present mvenhon. ln general, the ethylene/alpha-olehn copolymer comprises a copolymer resulting from the copolymeπzahon of from about 80 to 99 weight percent ethylene and from 1 to 20 weight percent alpha-olefin Preferably, the ethylene alpha-olehn copolymer compnses a copolymer resultmg from the copolymerization of from about 85 to 95 weight percent ethylene and from 5 to 15 weight percent alpha-olehn As used herem, the phrases "inner layer" and "internal layer" refer to any layer, of a multilayer im, havmg both of its principal surfaces directly adhered to another layer of the him. As used herem, the phrase "outer layer" refers to any film layer of a multilayer film havmg only one of its principal surfaces directly adhered to another layer of the film As used herem, the phrase "mside layer" refers to the outer layer, of a multilayer him packaging a product, which is closest to the product, relative to the other layers of the multilayer him As used herein, the phrase "outside layer" refers to the outer layer, of a multilayer film packaging a product, which is furthest from the product relahve to the other layers of the multilayer him As used herem, the phrase "directly adhered", as appbed to film layers, is defined as adhesion of the subject film layer to the object film layer, without a he layer, adhesive, or other layer therebetween. In contrast, as used herem, the word "between", as appbed to a film layer expressed as bemg between two other specified layers, mcludes both direct adherence of the subject layer between to the two other layers it is between, as weU as mcludmg a lack of direct adherence to either or both of the two other layers the sub j ect layer is between, i.e., one or more additional layers can be imposed between the sub j ect layer and one or more of the layers the subject layer is between As used herem, the term "core", and the phrase "core layer", as appbed to multilayer films, refer to any internal film layer which has a pπmary function other than serving as an adhesive or compahbibzer for adhermg two layers to one another. UsuaUy, the core layer or layers provide the multilayer film with a desired level of strength, e.g , modulus, and/ or optics, and/ or added abuse resistance, and/or specific lmpermeabibty As used herem, the phrases "seal layer" and "sealant layer", with respect to multilayer films, refers to an outer film layer, or layers, involved the sealmg of the film to itself or another layer. It should also be recognized that in general, the outer 0.5 to 3 mils of a film can be involved in the sealmg of the film to itself or another layer With respect to packages havmg only hn-type seals, as opposed to lap seals, the phrase "sealant layer" generally refers to the mside film layer of a package, as well as supporting layers adjacent this sealant layer often being sealed to itself, and frequently serving as a food contact layer in the packaging of foods. As used herem, the phrase "tie layer" refers to any internal layer havmg the primary puφose of adheπng two layers to one another. As used herem, the phrase "skin layer" refers to an outside layer of a multilayer film in packaging a product, this skin layer bemg subject to abuse. As used herem, the phrase "bulk layer" refers to any layer of a film which is present for the puφose of mcreasmg the abuse-resistance, toughness, modulus, etc., of a multilayer film. Bulk layers generally comprise polymers which are inexpensive relahve to other polymers in the film which provide some specific puφose unrelated to abuse- resistance, modulus, etc. As used herem, the term "extrusion" is used with reference to the process of forming continuous shapes by forcmg a molten plashc material through a die, foUowed by coolmg or chemical hardening. Immediately prior to extrusion through the die, the relahvely high- viscosity polymenc material is fed into a rotahng screw of variable pitch, which forces it through the die. As used herem, the term "coextrusion" refers to the process of extruding two or more mateπals through a smgle die with two or more orifices aπanged so that the extrudates merge and weld together mto a laminar structure before chilling, i.e., quenchmg. Coextrusion can be employed him blowmg, free film extrusion, and extrusion coatmg processes. As used herem, the phrase "machme direction", herem abbreviated "MD", refers to a direction "along the length" of the im, i.e., in the direction of the film as the him is formed duπng extrusion and/or coatmg. As used herem, the phrase "transverse direction", herem abbreviated "TD", refers to a direction across the him, peφendicular to the machme or longitudmal direction. As used herem, the phrase "free shrmk" refers to the percent dimensional change a 10 cm x 10 cm specimen of film, when subjected to selected heat, as measured by ASTM D 2732, as known to those of skiU m the art Accordmg to the first aspect of the present invention as set forth above, if the first polyolefm comprises ethylene/ unsaturated acid, propylene/ unsaturated acid, and/ or butene/ unsaturated acid, preferably the unsaturated acid mer is present in an amount of from about 4 to 30 weight percent, based on the weight of the copolymer; more preferably, from about 7 to 20 percent; still more preferably, from about 8 to 15 percent; and, yet still more preferably, from about 9 to 13 percent. Depending upon the meat product, if the unsaturated acid mer is present m an amount less than 6 weight percent, sufficient purge-resistance may not be achieved upon cookmg the meat product in the casmg. On the other hand, if the amount of unsaturated acid mer is present in an amount greater than about 20 weight percent, the softenmg pomt of the unsaturated acid copolymer may be too low to facilitate film produchon and/or obtain satisfactory seal strength for cook-in end use. Thus, the ophmal level of unsaturated acid mer depends on the manner m which the film is produced, and the particular end-use of the film, e.g., the type of meat bemg packaged, and the cook-in conditions. If the first polyolefin comprises anhydnde-contammg polyolefin comprising an anhydride-functionality, preferably the anhydride functionality is present in an amount of from about 1 to 10 weight percent, based on the weight of the anhydnde-contammg polyolefm; more preferably, from about 2 to 5 weight percent. In a lap-sealed backseamed casing accordmg the present mven on, preferably the hrst polyolefm has a vicat softening point of at least 70°C, more preferably at least 80°C, and still more preferably at least 90°C, m order to provide a desired level of seal strength. However, m a butt-sealed backseamed casmg accordmg to the present invention, in which a butt-tape film is sealed to the outer surface of the third film layer, the lower-limit of the softenmg pomt of the first polyolefin may be less critical. Preferably, the first polyolefm is present m the first outer layer in an amount of from about 10 to 50 weight percent, based on the weight of the hrst layer; more preferably, m an amount of from about 10 to 30 percent; and still more preferably, in an amount of from about 15 to 25 percent. As the third polyolefin, LLDPE is more preferred than propylene/ ethylene copolymer because LLDPE produces a seal havmg less "pucker", if the second polyolefin also comprises LLDPE and the casmg is a lap-seal backseamed casmg. The third polyolefin provides the first layer with a high melting point resm, which is advantageous for cook-in end use, where the casing is subjected to relatively high temperatures for a relahvely long period of time. Preferably, the third polyolefin has a melting pomt less than 160°C; more preferably, less than 140°C, and still more preferably, less than 130°C. Preferably, the third polyolefm has a vicat softenmg point of at least 80°C, more preferably, at least 90°C, and still more preferably, at least 100°C In the second layer, the first polyamide preferably comprises at least one member selected from the group consisting of polyamide 6, polyamide 66, polyamide 9, polyamide 10, polyamide 11, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, and copolymers thereof; more preferably, at least one member selected from the group consistmg of polyamide 6, polyamide 66 and polyamide 6/66. Preferably, the first polyamide has a meltmg pomt of at least 350°F; more preferably, at least 370°F; still more preferably, at least 390°F. Preferably, the second layer further comprises a third polyamide havmg a melting pomt of less than about 350°F. Preferably, the second layer comprises: (a) polyamide 6 m an amount of from about 40 to 90 weight percent, based on the weight of the second layer; and (b) copolyamide 6/12 in an amount of from about 10 to 60 weight percent, based on the weight of the second layer, wherein the copolyamide 6/12 comprises caprolactam mer in an amount of from about 30 to 70 weight percent (more preferably, 40 to 60 weight percent). Preferably, the first polyamide has a meltmg pomt above 350°F, and the third polyamide has a meltmg pomt below 350° F, as this combination has been found to produce a combmahon of modulus, oπentabihty, seal strength, and pmhole-resistance which is preferred. Preferably, the second polyolefin comprises at least one member selected from the group consistmg of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer. More preferably, the second polyolefm comprises at least one member selected from the group consisting of ethylene/alpha-olehn copolymer, propylene/ alpha-olehn copolymer, butene/ alpha-olefin copolymer, ethylene/ unsaturated ester copolymer, and ethylene/ unsaturated acid copolymer. Still more preferably, the second polyolefin comprises at least one member selected from the group consisting of Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/ butene copolymer. Yet still more preferably, the second polyolefm comprises LLDPE. In a lap-seal backseam casing accordmg to the present mvenhon, preferably the second polyolefm and the third polyolefm are the same polymer. If the fifth and sixth layers each comprise polystyrene or polyurethane, they may be the same polystyrene and/ or polyurethane, or different polystyrenes and/ or polyurethanes. In serving as he layers, preferably the fifth and sixth layers each assist the adhesion of the preferably polyole nic first and third layers to the polyamide layer, as well as to the 0 2 -barner layer, if present. The butt-seal tape film is chosen so that it is seal-compatible with the sealant surface of the casmg film. Preferably, the butt-seal tape film comprises polyolefm as an outer sealing layer. More preferably, the butt-seal tape him further comprises an 0 2 - barπer layer. Still more preferably, the butt-seal tape film further comprises two tie layers, i.e., a he layer between the 0 2 -barπer layer and each of the two outer layers, each of which comprise polyolefin. Preferably, the butt-seal tape film is heat-shrmkable, and preferably, the butt-seal tape film comprises an outer sealmg layer compnsmg polyolefin havmg a melting pomt of from about 90°C-150°C; more preferably, from about 100°C-130°C. The seal layer of the butt-seal tape film is an outer film layer which preferably comprises at least one member selected from the group consistmg of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer; more preferably, ethylene/ alpha-olehn copolymer, propylene/ alpha-olefin copolymer, butene/ alpha- olefin copolymer, ethylene/ unsaturated ester copolymer, and ethylene/ unsaturated acid copolymer; still more preferably, Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/butene copolymer. In the casmg film accordmg to the third aspect of the present mvention, all of the various polymers present m each of the film layers are preferably as described above accordmg to the first aspect of the present mvenhon, except that the first polyolefin of the hrst layer has surface energy of less than 34 dynes/ cm, more preferably, less than 32 dynes/cm. Thus, the third aspect of the present mvention, the hrst polyolefm preferably comprises at least one member selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer. More preferably, the first polyolefin comprises at least one member selected from the group consistmg of ethylene/ alpha-olehn copolymer, propylene/ alpha-olehn copolymer, butene/ alpha-olefin copolymer, ethylene/ unsaturated acid copolymer, and ethylene/ unsaturated ester copolymer Still more preferably, the first polyolefm comprises at least one member selected from the group consisting of Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/butene copolymer. Yet still more preferably, the hrst polyolefm comprises LLDPE. Preferably, the multilayer film has a shrink tension of at least about 10 psi, more preferably, from about 20-1000 psi, shll more preferably, from about 100 to 600 psi; and yet still more preferably, from about 300 to 500 psi. A preferred backseamed casmg according to the present invention comprises a multilayer heat shrmkable film compnsmg a meat-adhesion layer compnsmg a polar polymer, which provides a high level of meat adhesion, especially to m termed ιate/ high protein-containing meat products. Although this film can be corona treated, the film of the invention does not require corona treatment m order to exhibit a desired level of meat adhesion with products such as turkey, good-to-mtermediate quality ham. and roast beef. However, the backseamed casmg film of the present mvenhon can be corona treated in order to provide an enhanced level of adhesion, especially with high fat products. Typically, films which by themselves have a relatively low level of meat- adhesion exhibit the 'bufftng-off problem described above, at least at the backseamed edges thereof. However, the films of the present mvenhon have an advantage that respect. Because the untreated films already have an acceptable level of meat-adhesion to intermediate-quality meat products, even when the corona treatment is buffed-off the surface durmg the backseammg operation, there is sufficient protem-adhesion from the polymer to prevent purge or fatting-out. Thus, the ultimate package still has an acceptable level of adhesion. Optionally, corona treatment could also be carried out after the backseamed tubmg is made. Here, too, if a relahvely low-meat-adheπng- polymer is used as the inside casmg layer and the resultmg backseamed tubmg is then corona treated, substantial purge (also known as cook-out and fatting-out) can occur on a strip at the edge of the backseamed tubmg, where there is msufficient corona treatment (inherent in the process used to internally corona treat). However, the corona treatment of a film surface which already has an enhanced level of meat-adhesion (as is the case in the present invention) reduces or eliminates the purge or cook-loss at the casmg lay flat edges (which, as described above, have not been substantially treated). Thus, the backseamed casmg of the present mvention avoids the "buffing off problem" associated with corona treatment, while at the same time achieving a satisfactory level of meat adhesion to various different kinds of protein-containing meat products. As described above, the second layer of the casmg him must have a thickness of at least about 5% of a total thickness of the heat-shrmkable casmg film. That is, if the thickness of the second layer is less than about 5 percent of the total thickness of the film, the second layer may not perform adequately prevenhng the film from shrmkmg down agamst the forming shoe. If the heat-shrinkable casing him m the backseamed casmg is made by orienting a tape which is heated over a very short hme peπod, such as a tape heated by mfrared radiation, the thickness of the second layer could be as high as 70%, based on the thickness of the multilayer him. However, if the film is heated over a relatively long time period, such as bemg heated in hot water, the preferred polyamides tend to crystallize to a relatively high level before the orientation step, which produces problems durmg the orientation step (the rate of crystallization depends on the type of polyamide used). In this latter situation, typically, the greater the thickness of the second layer, the more difficult it is to orient to obtam the resultmg casmg film. This forces a practical limit on the maximum percentage thickness of the second layer (especially when the most preferred polyamides are used), based on the total thickness of the multilayer casmg film. Thus, if hot-water is used as the orientation medium, the second layer of the casmg film preferably has a thickness of from about 5 to 50 percent of the total thickness of the casmg film; more preferably, from about 5 to 40 percent; still more preferably, from about 10 to 30 percent; and yet still more preferably, from about 10 to 20 percent, based on a total thickness of the multi-layer him. It has been discovered that the second layer, which preferably compnses polyamide, serves to prevent neckmg down on the forming shoe dunng the backseammg process. Neckmg down typicaUy occurs dunng the backseammg process when the him is drawn so hghtly around the forming shoe (as a result of the film shrmkmg due to the heat generated outwards from the seal area duπng the backseammg process) that it cannot be forwarded. The presence of the second layer, significantly reduces the neckmg down of the him by reducing that region of the film which shrinks due to the propagation of heat outward from the heat seal bar. Preferably, the backseamed casmg of the present invention comprises a casing fibn havmg from 3 to 20 layers; more preferably, from 4 to 12 layers; still more preferably, from 6 to 10 layers. Preferably, the multilayer casmg film used m the backseamed casmg accordmg to the present mvenhon can have any total thickness desired, so long as the film provides the desired properties for the particular packaging operation in which the film is used. Preferably, the casmg fibn used in the present mvenhon has a total thickness, i.e., a combmed thickness of aU layers, of from about 0.5 to 10 mils (1 mil equals 0.001 mch); more preferably, from about 1 to 8 mils; and shll more preferably, from 2 to 4 mils It should be noted that the modulus of the casmg film should be high enough that so that the film does not stretch to an undesirable degree durmg the backseammg process. Preferably, the casmg film has a modulus of at least 20,000 psi; more preferably, from about 30,000 to 250,000 psi; shll more preferably, from about 40,000 to 150,000 psi.; yet still more preferablv, from about 45,000 to 120,000; and even yet still more preferably, from about 50,000 to 70,000 psi. lt should be kept m mmd that if the modulus of the casmg him is too high, problems could occur after backseammg, e.g., the film could flex-crack when bemg wound up after backseammg or cause difficulty m tracking. Furthermore, too high a modulus is especially undesirable if the film is to be used as a casmg which is to undergo shirrmg, as films of too high a modulus may flex- crack durmg shirrmg. On the other hand, if the modulus of the him is too low, the film tends to stretch too much durmg backseammg, thereby producmg backseamed casmg of low quality m that it does not backseam acceptably, has a wavy appearance, and/or has ruffled edges, and/ or seal pucker, and/ or does not track well through the machme. Figure 1 iUustrates lap-seal backseamed casmg 11 accordmg to the present mvention Lap-seal backseamed casmg 11 comprises heat-shrmkable casmg film 12, which is sealed to itself at backseam lap-seal 13. Figure 2 illustrates an enlarged cross-sectional view of heat-shrinkable casmg him 12, which is especiaUy suited to the packaging of meat. In Figure 2, casmg film 12 compnses: hrst layer 14, second layer 16, third layer 18, fourth layer 20, fifth layer 22, sixth layer 24, seventh layer 26, and eighth layer 28. First layer 14 is an outer im layer which serves as an mside layer of the casmg film First layer 14 has outer meat-contact surface 15 for direct contact, and adhesion to, the meat bemg packaged m casmg 11. Preferably, first layer 14 has a thickness of from about 0.1 to 3 mils; more preferably, from 0.2 to 1 mil; still more preferably, from 0.3 to 0.8 mil; and yet shll more preferably, about 0.5 mils. First layer 14 comprises a polar polymer which preferably has a surface energy greater than 32 dynes/cm, more preferably greater than 34 dynes/cm, and still more preferably greater than 36 dynes/ cm. Preferably, first layer 14 comprises a first polyolefin compnsmg at least one member selected from the group consistmg of: (I) ethylene/ unsaturated acid copolymer, propylene/ unsaturated acid copolymer, and butene/ unsaturated acid copolymer, wherem the unsaturated acid (mer) is present an amount of at least 4 weight percent, based on the weight of the copolymer; and (n) anhydnde-contammg polyolefm compnsmg an anhydride-functionality, wherem the anhydride functionality is present an amount of at least 1 weight percent, based on the weight of the anhydnde-contammg polyolefin; More preferably, first layer 14 comprises a first polyolefin compnsmg at least one member selected from the group consisting of: (l) ethylene/ unsaturated acid copolymer, propylene/ unsaturated acid copolymer, and butene/ unsaturated acid copolymer, wherem the unsaturated acid (mer) is present m an amount of from about 6-30%, more preferably from about 7-20%, shll more preferably from about 8-15%, and yet still more preferably, from about 9-13%, based on the weight of the copolymer; and (π) anhydnde-contammg polyolefin compnsmg an anhydride-functionality, wherem the anhydride funchonahty is present m an amount of from about 1 to 10 weight percent, based on the weight of the anhydnde-contammg polyolefm; more preferably from about 2 to 5 weight percent. If the first polyolefm comprises unsaturated acid copolymer, if the unsaturated acid mer is present in an amount less than 6 weight percent, sufhcient purge resistance may not be achieved. On the other hand, if the amount of unsaturated acid (mer) in the copolymer is greater than about 20 weight percent, the softenmg pomt of the unsaturated acid copolymer may be too low to facilitate processmg mto film and/or obta sahsfactory seal strength durmg cooking. The preferred unsaturated acid (mer) level may vary depending on the end appbcation, i.e., the type of meat product to be adhered to. In any backseamed casmg accordmg to the present mvenhon, preferably, the mside film layer (which serves as a food-contact layer, and, m the lap seal backseamed casmg accordmg to the present mvenhon also serves as a sealant layer) does not comprise a blend of propylene/ ethylene copolymer and homogeneous ethylene/alpha-olehn copolymer havmg a density of less than 0.90. That is, if this blend makes up the majonty of the seal layer, the seal strength may be less than preferred. Furthermore, if this blend makes up the majonty of the seal layer, no core layer of polyester and/ or hrst polyamide is required in order to backseam the film without a detnmental degree of neckmg down on the forming shoe. Multilayer film 12 may be used m either a lap-seal backseamed casmg or a butt- seal backseamed casmg. ln a lap-seal backseamed casmg such as casmg 11, preferably the first polyolefin has a vicat softenmg point of at least 70°C, more preferably at least 80°C, m order to retam good seal strength durmg cook-m. However, for a butt-sealed backseamed casmg, the lower-limit of the softening pomt of the first polyolefin may be less critical, as it is both the softenmg pomt of the third layer of the casmg film, as well as the softening pomt of the sealant layer of the butt-seal tape film, which govern sealabihty and seal strength durmg cookmg Preferably, first layer 14 further comprises a third polyolefin compnsmg at least one member selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer. More preferably, the third polyolefin comprises at least one member selected from the group consistmg of ethylene/alpha-olehn copolymer, propylene/ alpha-olehn copolymer, butene/ alpha- olefin copolymer, ethylene/ unsaturated acid copolymer, and ethylene/ unsaturated ester copolymer. Even more preferably, the third polyolefm comprises at least one member selected from the group consistmg of Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/ butene copolymer. Preferably, the third polyolefm has a vicat softenmg pomt of at least 80°C, more preferably, at least 90°C, and even more preferably at least 100°C. Preferably, the hrst polyolefm is present in an amount of from about 10-50%, more preferably, in an amount of from about 10- 30%, and even more preferably, in an amount of from about 15-25%, based on the composition of the first outer layer. The third polyolefm provides hrst layer 14 with a higher softenmg pomt polymer to enhance the stability of the film, and seals thereof, durmg cook-m. Furthermore, the dilution of the polar polymer with a relatively non-polar polymer, i.e., the third polyolefin, does not significantly decrease the purge-resistance characteristics of the first layer of the casing film Preferably, hrst layer 14 comprises a blend of 80 weight percent LLDPE and 20 weight percent ethylene/ unsaturated acid copolymer Second layer 16 is an inner him layer which is between first layer 14 and third layer 18. Second layer 16 provides casmg him 11 with the charactenshc of undergoing the backseaming opera hon without neckmg down on the formmg shoe. Second layer 16 also helps to provide a better quality casing film by mak g casmg im 12 easier to oπent, and facibtating faster backseaming speeds, and also imparting enhanced seal strength, toughness, pin-hole resistance and elashc recovery to casmg film 12. Second layer 16 preferably compnses at least one member selected from the group consistmg of polyester, and first polyamide, i.e., polymers havmg relatively high modulus and/ or relahvely high elashc recovery. More preferably, second layer 16 compnses the first polyamide; still more preferably, at least one member selected from the group consistmg of polyamide 6, polyamide 66, polyamide 9, polyamide 10, polyamide 11, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, as well as copolymers prepared from copolymerization of any one or more of the monomers used the preparation of any of these polyamides; and yet shll more preferably, at least one member selected from the group consisting of polyamide 6, polyamide 66 and polyamide 6/66. Preferably, the first polyamide has a melting pomt of at least 350°F; more preferably, at least 370°F; even more preferably, at least 390°F. Preferably, second layer 16 has a thickness of from about 0.05 to 1 mil; preferably, from 0.1 to 0.5 mil; more preferably, from about 0.2 to 0.4 mil, and shll more preferably, about 0.3 mils. Preferably, second layer 16 further comprises a third polyamide having a meltmg pomt of less than about 350°F. Preferably, second layer 16 comprises: (a) polyamide 6 m an amount of from about 40 to 90 weight percent, based on the weight of the hrst mner layer; and (b) copolyamide 6/12 m an amount of from about 10 to 60 weight percent, based on the weight of the first mner layer, wherem the copolyamide 6/12 compnses caprolactam (mer) m an amount of from about 30 to 70 weight percent, based on the weight of the copolyamide; more preferably, from about 40 to 60 weight percent. Third layer 18 is an outer him layer which serves as an outside abuse-resistant and heat-seal layer of casmg 11. Preferably, third layer 18 has a thickness of from about 0.1 to 3 mils; more preferably, from about 0.2 to 1 mil; still more preferably, from about 0.3 to 0.8 mil; and, yet still more preferably, about 0.35 to 0.65 mil Preferably, third layer 18 compnses at least one member selected from the group consisting of second polyolefin, polystyrene, second polyamide, polyester, polymenzed ethylene/ vmyl alcohol copolymer, polyvinyhdene chlonde, polyether, polyurethane, polycarbonate, and starch-containing polymer; more preferably, third layer 18 comprises the second polyolefm; stiU more preferably, at least one member selected from the group consisting of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer; yet still more preferably, third layer 18 comprises at least one member selected from the group consistmg of ethylene/ alpha-olefin copolymer, propylene/ alpha-olefin copolymer, butene/ alpha-olefin copolymer, ethylene/ unsaturated ester copolymer, and ethylene/ unsaturated acid copolymer; and yet still even more preferably, third layer 18 comprises at least one member selected from the group consistmg of Imear low density polyethylene (LLDPE), propylene/ ethylene copolymer, and propylene/ butene copolymer. In a lap-seal backseam casmg, the second polyolefm and the third polyolefin are preferably the same polymer. Preferably, the second polyolefm has a vicat softenmg pomt of at least 80°C, more preferably, at least 90°C, and even more preferably at least 100°C. The softenmg pomt of the second polyolefin needs to be high enough for the casmg to survive cook-m. Fourth layer 20 is an internal layer which is between hrst layer 14 and third layer 18, and preferably comprises a polymer havmg relahvely high oxygen bamer charactenstics. Preferably, fourth layer 20 has a thickness of from about 0.05 to 2 mils; more preferably, from 0.05 to 0.5 mil; shll more preferably, from 0.1 to 0.3 mil; and yet shll more preferably, from about 0.12 to 0.17 mils. In general, fourth layer 20 compnses at least one member selected from the group consistmg of polymerized ethylene vmyl alcohol (EVOH), polyvinylidene chlonde, fourth polyamide, polyalkylene carbonate, and polyester; preferably, at least one member selected from the group consistmg of polymerized ethylene vmyl alcohol and fourth polyamide; more preferably, polymenzed ethylene vmyl alcohol; stiU more preferably, polymenzed ethylene vmyl alcohol havmg about 44 mole percent ethylene. Fifth layer 22 and sixth layer 24 are he layers m casing him 12. Fifth layer 22 is between first layer 14 and second layer 16; sixth layer 24 is between second layer 16 and third layer 18. As a general rule, he layers should have a relatively high degree of compahbibty with barner layers, such as polymenzed EVOH, or the polyamide layer, as weU as non-barner layers, such as polymerized ethylene alpha-olehn copolymer The composihon, number, and thickness of he layers is as known to those of skill in the art. Preferably, fifth layer 22 and sixth layer 24 each have a thickness of from about 0.05 to 2 mils, more preferably, from about 0.05 to 0.5 mil; still more preferably, from about 0.1 to 0.3 mil; and yet shll more preferably, from about 0.12 to 0.17 mils. Preferably, fifth layer 22 comprises at least one member selected from the group consistmg of fourth polyolefin, polystyrene and polyurethane; more preferably, at least one member selected from the group consisting of modified ethylene/alpha-olehn copolymer, modihed ethylene/ unsaturated ester copolymer, and modified ethylene/ unsaturated acid copolymer. Preferably, sixth layer 24 comprises at least one member selected from the group consisting of fifth polyolefm, polystyrene and polyurethane; more preferably, at least one member selected from the group consistmg of modified ethylene/alpha-olefin copolymer, modified ethylene/ unsaturated ester copolymer, and modihed ethylene/ unsaturated acid copolymer Seventh layer 26 is a core layer between first layer 14 and second layer 16. Seventh layer 26 provides the multilayer casmg him 12 im with desired abuse, shrink, and optical characteristics, and preferably compnses a polymer havmg relahvely low cost while providmg these characteristics Preferably, seventh layer 26 has a thickness of from about 0.1 to 3 mils; more preferably, from 0.2 to 1.5 mils; shll more preferably, from 0.3 to 1 mil; and yet shll more preferably, from about 0.50 to 0.80 mils. Preferably, seventh layer 26 compnses at least one member selected from the group consistmg of polyolefm, polyamide, polyester, and polyurethane; more preferably, polyolefin; shll more preferably, at least one member selected from the group consisting of ethylene/alpha-olehn copolymer, propylene/ alpha- olefin copolymer, butene/ alpha-olehn copolymer, ethylene/ unsaturated ester copolymer, and ethylene/ unsaturated acid copolymer; and yet shll more preferably, a blend of 80 weight percent ethylene vmyl acetate copolymer (havmg 6 weight percent vmyl acetate mer) with 20 weight percent high density polyethylene. Eighth layer 28 is a core layer between second layer 16 and third layer 18. Eighth layer 18 also provides the multilayer film with desired abuse, shrink, and optical charactenstics, and preferably compnses a polymer havmg relahvely low cost while providmg these attributes. In general, eighth layer 18 can have a thickness of from about 0 1 to 3 rruls; preferably, from 0.2 to 1.5 mil; more preferably, from 0.3 to 1 mil; and sbll more preferably, from about 0.50 to 0.80 mils. In general, eighth layer 18 comprises at least one member selected from the group consistmg of polyolefm, polyamide, polyester, and polyurethane; preferably, polyolefm, more preferably at least one member selected from the group consistmg of ethylene/alpha-olehn copolymer, propylene/ alpha-olefin copolymer, butene/ alpha-olefin copolymer, ethylene/ unsaturated ester copolymer, and ethylene/ unsaturated acid copolymer; shll more preferably, a blend of 80 weight percent ethylene vmyl acetate copolymer (havmg 6 weight percent vmyl acetate) with 20 weight percent ethylene/ unsaturated acid copolymer. Seventh layer 26 and eighth layer 28 are typically chosen in composihon and layer thickness so as to provide a relahvely flat, curl-free, heat-shrinkable casmg film. Preferably, seventh layer 26 and eighth layer 28 have a composihon and thickness so as to provide the multilayer film with as much cross-sechonal symmetry as possible. Cross-sectional symmetry provides the him with the desired characteπshcs of low curl and low floppmess. If "a" represents a sum of the thicknesses of the first, fifth, and seventh layers, and "b" represents a sum of the thicknesses of the second, sixth, and eighth layers, then preferably, a:b is from about 0.5:1 to 1.5:1, more preferably 0.71 to 1.3.1, shll more preferably, from about 0.8:1 to 1.2:1. In casmg 11, backseam seal 13 can be formed usmg any one or more of a wide vanety of sealmg devices, as known to those of skiU in the art, such as heat sealmg via hot air and/ or heated bar and/ or hot wire, ultrasonic sealmg, radio frequency sealing, etc. However, a preferred sealmg mechanism is the use of a heated seal bar which provides for better sealabibty and can provide better ultimate seal strength, thus providmg seals capable of surviving the cooking process. Figure 3 iUustrates alternative preferred six-layer, heat-shrmkable casmg film 30 suitable for use as a lap-seal casmg as iUustrated in Figure 1, as weU as a butt-seal casmg as illustrated m Figure 5. As with multilayer im 12 of Figure 2, multilayer him 30 is also especially suited to the packaging of meat products which are thereafter subjected to cook-m. Casmg film 30 compnses first layer 32, second layer 34, third layer 36, fourth layer 38, fifth layer 40, and sixth layer 42. First layer 32 is an outer film layer which serves as an mside casmg film layer, and accordmgly is a meat-contact layer which is analogous to first layer 14 of Figure 2. When in the form of casmg, first layer 32 has mside meat-contact surface 33 for direct contact with, and adhesion to, the meat within the casing. If casmg him 30 is used to make lap-seal casmg 11 as illustrated m Figure 1, first layer 32 is sealed to second layer 34 at backseam lap seal 13, this seal bemg located where a portion of outer surface 33 overlaps outside surface 35 of casmg film 30. First layer 32 has the same general and preferred thickness and chemical composihon as hrst layer 14 of Figure 2 However, first layer 32 most preferably has a thickness of 0.8 mils. Second layer 34 is a core layer between first layer 32 and third layer 36, and m general is analogous to second layer 16 of Figure 2. Second layer 34 has the same general and prefeπed thickness and chemical composihon as second layer 16 of Figure 2. Third film layer 36 is an outer film layer which serves as an outside, abuse-resistant heat-seal layer of casmg 11. Preferably, third layer 36 is analogous to third layer 18 of Figure 1. Third layer 36 has the same general and preferred thickness and chemical composihon as third layer 18 of Figure 1. However, third layer 36 most preferably has a thickness of about 0.8 mils. Fourth layer 38 is an inner layer between hrst layer 32 and third layer 36, and in general is analogous to fourth layer 20 of Figure 2. Fourth layer 38 has the same general and prefened thickness and chemical composition as fourth layer 20 of Figure 2. Fifth layer 40 is a he layer between first layer 32 and second layer 34, and m general is analogous to fifth layer 22 of Figure 2. Fifth layer 40 has the same general and prefeπed thickness and chemical composihon as fifth layer 22 of Figure 2. Sixth layer 42 is a he layer between second layer 34 and third layer 36, and m general is analogous to sixth layer 24 of Figure 2. Sixth layer 42 has the same general and prefened thickness and chemical composition as sixth layer 24 of Figure 2. Figure 4 illustrates an alternative preferred three-layer, heat-shrmkable, multi-layer casmg film 44 suitable for use as a lap-seal casmg 11 as illustrated m Figure 1. As with multilayer film 12 of Figure 2, multi-layer film 44 is also especiaUy suited to the packaging of meat products which are thereafter subjected to cook-m. Casmg film 44 compnses first layer 46, second layer 48, and third layer 50. First layer 46 is an outer him layer which serves as an mside casmg film layer, and is a meat-contact layer which is analogous to first layer 14 of Figure 2. When m the form of a casmg, first layer 46 of multilayer film 44 has mside meat-contact surface 47 for direct contact with, and adhesion to, the meat within the casing If casmg him 44 is used to make lap-seal casmg 11 as iUustrated in Figure 1, hrst layer 46 is sealed to third layer 50 at backseam lap seal 13, this seal bemg located where a porhon of mside surface 47 overlaps a portion of outside surface 51 of casmg film 44 Preferably, hrst layer 46 has the same thickness and chemical composihon as first layer 14 of Figure 2; more preferably, hrst layer 46 comprises a modihed polyolefin for improved bonding to second layer 48; stiU more preferably, hrst layer 46 compnses anhydnde-modihed LLDPE as the third polyolefin. Also, more preferably, first layer 46 has a thickness of 1.0 mil. Second layer 48 is a core layer between hrst layer 46 and third layer 50, and general is analogous to second layer 16 of Figure 2. Second layer 48 has the same general and preferred thickness and chemical composihon as second layer 16 of Figure 2. Third layer 50 is an outer abuse-resistant layer and heat-seal layer, which is analogous to third layer 18 of Figure 2. Preferably, third layer 50 has the same thickness and chemical composihon as third layer 18 of Figure 2. However, third layer 50 further compnses a modified polyolefin for improved bonding to second layer 48; more preferably, third layer 50 compnses, as the second polyolefin, 100 weight percent anhydnde-modihed LLDPE Also, more preferably, third layer 50 has a thickness of 1.0 mil. Figure 5 iUustrates a cross-sectional view of butt-seal backseamed casing 52, in accordance with the present mvenhon. Butt-seal backseamed casmg 52 compnses heat- shnnkable casmg film 54 havmg abutting longitudmal edges 56 and 58, and butt-seal tape 60, one side of which is sealed to outside surface 55 of casing film 54, seals 59 and 61 bemg in regions adjacent to and along longitudmal edges 56 and 58. In this manner, a tubular casmg is provided which a product can be packaged, especiaUy a meat product which is thereafter subjected to cook-m while packaged m butt-seal backseamed casmg 52. Figure 6 iUustrates prefeπed heat-shnnkable, multilayer him 62 for use as casmg him 54 m butt-seal backseamed casmg 52 iUustrated m Figure 5. Multilayer film 62 comprises first layer 64, second layer 66, third layer 68, fourth layer 70, hfth layer 72, and sixth layer 74. First film layer 64 is a meat-contact and meat adhesion which is analogous to first layer 32 of the film of Figure 3. First film layer 64 serves as an mside casmg layer, and provides meat-contact surface 65 for direct contact with, and adhesion to, meat packaged m the casmg which is thereafter subjected to cook-in. Preferably, hrst layer 64 has the same thickness and chemical composihon as first layer 32 of Figure 3. Second layer 66 is an inner film layer which serves as a casmg core layer which reduces or ehminates neckmg down on the forming shoe durmg the backseaming operation. Second layer 66 is between first layer 64 and third layer 68, and is analogous to second layer 34 of the film of Figure 3. Preferably, second layer 66 has the same thickness and chemical composihon as second layer 34. Third layer 68 is an outer film layer which serves as an outside casmg abuse- resistance and heat-seal layer, and is analogous to third layer 36 of the him of Figure 3 Preferably, third layer 68 has the same thickness and chemical composihon as third layer 36 Fourth layer 70 is an inner film layer which serves as an Cvbaπier layer, is between first film layer 64 and third fibn layer 68, and is analogous to fourth layer 38 in film 30 of Figure 3. Preferably, fourth layer 70 has the same thickness and chemical composihon as fourth layer 38. Fifth layer 72 is an inner him layer which serves as a he layer, and is between first film layer 64 and second film layer 66, and is analogous to fifth layer 40 in film 30 of Figure 3. Preferably, fifth layer 72 has the same thickness and chemical composihon as fifth layer 40. Sixth layer 74 is an inner film layer which serves as a tie layer, and is between second him layer 66 and third film layer 68, and is analogous to sixth layer 42 in film 30 of Figure 3 Preferably, sixth layer 74 has the same thickness and chemical composition as sixth layer 42. Figure 7 iUustrates prefeπed heat-shrmkable, multilayer film 76 for use as butt-seal tape him 60 in butt-seal backseamed casmg 52 illustrated in Figure 5 Multilayer im 76 compnses first layer 78, second layer 80, third layer 82, fourth layer 84, and fifth layer 86. First layer 78 is an outer film layer which serves as a heat-seal layer, and is analogous to third layer 68 of film 62 dlustrated m Figure 6. First layer 78 serves as the outer layer of butt-seal tape film 60 which is sealed to outside surface 55 of casmg film 54, ι.e., to form seals 59 and 61 (see Figure 5). Preferably, first layer 78 has the same thickness and chemical composihon as third layer 68. Second layer 80 is an inner him layer between first layer 78 and third layer 82, serves as an Gvbarner layer, and is analogous to fourth layer 38 of multilayer film 30 illustrated m Figure 3. Preferably, second layer 80 has the same thickness and chemical composition as fourth layer 38. Third layer 82 is an outer film layer which serves as a butt-seal taf>e abuse-resistance layer, and is analogous composihon to third layer 68 of film 62 illustrated m Figure 6. Preferably, third layer 82 has the same thickness and chemical composihon as third layer 68. Fourth layer 84 is an inner im layer which serves as a tie layer, is between first layer 78 and second layer 80, and is analogous to fifth layer 40 of im 30 dlustrated m Figure 3 Preferably, fourth layer 84 has the same thickness and chemical composihon as fifth layer 40 Fifth layer 86 is an inner him layer which serves as a he layer, is between second layer 80 and third layer 82, and is analogous to sixth layer 42 of him 30 dlustrated m Figure 3. Preferably, hfth layer 86 has the same thickness and chemical composihon as sixth layer 42. lt should be noted that the butt-seal tape him need not have a core layer of polyamide or polyester which prevents the butt-seal tape fibn from neckmg down on the forming shoe. This is due to the fact that the butt-seal tape occupies so bttle of the overaU structure of the butt-sealed backseamed casmg, that the shnnkage of the tape film dunng the backseammg operahon has bttle tendency to cause neckmg down on the forming shoe. Backseamed casmgs 11 and 52 (dlustrated in Figures 1 and 5, resp>echvely) which use films 12, 30, 44, 62, and 76 (illustrated in Figures 2, 3, 4, 6, and 7, respectively), are suited to many different forms of packaging in accordance with the present mvenhon, mcludmg shiπed casmgs, bags, etc. Figure 8 illustrates a preferred process for makmg casmg film and/ or butt-seal tape film for m accordance with the present mvenhon. For example, Figure 8 illustrates a preferred process for makmg the hlms illustrated m Figures 2, 3, 4, 6, and 7. In the process dlustrated m Figure 8, sobd polymer beads (not dlustrated) are fed to a plurahty of extruders (for simpbciry, only extruder 88 is dlustrated). Inside extruders 88, the polymer beads are degassed, foUowing which the resultmg bubble-free melt is forwarded mto die head 90, and extruded through an annular die, resultmg m tubmg tape 92 which is preferably from about 15 to 30 rruls thick, and preferably has a lay-flat width of from about 2 to 10 mches. After cooling or quenching by water spray from cooling nng 94, tubmg tape 92 is coUapsed by pinch roUs 96, and is thereafter fed through irradiation vault 98 suπounded by shielding 100, where tubmg tubmg 92 is uradiated with high energy electrons (i.e., ionizing radiahon) from iron core transformer accelerator 102. Tubmg tape 92 is guided through mediation vault 98 on roUs 104 Preferably, tubmg tape 92 is irradiated to a level of from about 40-100 kGy, resultmg in uradiated tubmg tape 106. Iπadiated tubmg tape 106 is wound upon w dup roU 108 upon emergence from iπadiahon vault 98, formmg irradiated tubmg tape cod 110. After irradiation and w dup, windup roU 108 and irradiated tubmg tape cod 110 are removed and installed as unw d roll 112 and unwind tubmg tape cod 114, on a second stage in the process of making the him as ultimately desired Irradiated tubmg 106, bemg unwound from unwmd tubmg tape cod 114, is then passed over guide roU 116, after which irradiated tubmg 106 is passed through hot water bath tank 118 contammg hot water 120. Iπadiated tubmg 106 is then immersed m hot water 120 (preferably havmg a temperature of about 185-210°F) for a penod of about 20-60, i.e., for a time period long enough to bring the im up to the desired temperature for biaxial orientation. Thereafter, hot, lπadiated tubular tape 122 is directed through nip roUs 124, and bubble 126 is blown, thereby transversely stretching hot, irradiated tubular tape 122 so that an oriented film tube 128 is formed. Furthermore, whde bemg blown, i.e., transversely stretched, nip rolls 130 have a surface speed higher than the surface speed of nip roUs 124, thereby resulting m longitudmal onentation. As a result of the transverse stretching and longitudmal drawing, onented film tube 128 is produced, this blown tubmg preferably havmg been both stretched in a raho of from about 1:1.5 to 1:6, and drawn in a raho of from about 1:1.5 to 1:6. More preferably, the stretching and draw g are each performed at a raho of from about 1:2 to 1:4. The result is a biaxial onentation of from about 1:2.25 to 1:36, more preferably, 1:4 to 1:16. Whde bubble 126 is maintained between pinch roUs 124 and 130, onented him tube 128 is coUapsed by roUers 132, and thereafter conveyed through pinch roUs 130 and across guide roU 134, and then roUed onto wmd-up roU 136. Idler roU 138 assures a good wmd-up. The resultmg multilayer him can be used to form backseamed casmgs, etc., which, m turn, can be used for the packagmg of meat products, in accordance with the present mvenhon. The films of the examples set forth below were prepared accordmg to the process descnbed immediately above. These examples provide additional detads on the backseamed casmgs, their use the packagmg of a meat product, and the unexpected results obtamed from the use of the casmg film dunng the backseammg process, and subsequent packagmg and cook-m of the meat product. The polymer components used to fabricate multilayer casmg film and butt-seal tape film accordmg to the present mvenhon may also contain appropnate amounts of addihves typicaUy mcluded in such compositions. These addihves mclude sbp agents such as talc, antioxidants, fillers, dyes, pigments, radiahon stabilizers, antistatic agents, elastomers, and bke addihves known to those of skill m the art of packagmg films The backseamed casmgs accordmg to the present mvenhon comprise casmg films and butt-seal tape films which can be prepared by any means known to those of skill m the art, e.g., via coextrusion and/or extrusion coating, and/or lamination However, preferably the films are produced by coextrusion The backseamed casmg accordmg to the present mvenhon preferably compnses a casmg film (and butt-seal tape him) which compnses a crosslmked polymer network Although the crosslmked polymer network can be produced one or more of a vanety of manners, such as chemical crosslinking and/ or uradiahon, preferably the crosslmked polymer network is produced by the irradiation of a tape or film. Either some or aU of the layers of the multdayer fdm can compnse crosslmked polymer networks. In the irradiation process, the film is subjected to an energetic radiahon treatment, such as high energy electron treatment, which mduces cross-bnkmg between molecules of the uradiated matenal. The uradiahon of polymenc fdms is disclosed U.S. Patent NO. 4,064,296, to BORNSTEIN, et. al., which is hereby incoφorated in its entirety, by reference thereto. BORNSTEIN, et. al. discloses the use of ionizing radiahon for crosslinking the polymer present m the film. Radiahon dosages are refened to herem terms of the radiahon unit "RAD", with one mdJion RADS, also known as a megarad, bemg designated as "MR", or, terms of the radiahon unit kiloGray (kGy), with 10 kiloGray representing 1 MR, as is known to those of skdl in the art. A suitable radiahon dosage of high energy electrons is m the range of up to about 16-166 kGy, more preferably about 44-139 kGy, and shll more preferably, 50-80 kGy. Preferably, uradiahon is earned out by an electron accelerator and the dosage level is determined by standard dosimetry methods. As used herem, the phrases "corona treatment" and "corona discharge treatment" refer to subjectmg the surfaces of thermoplastic mateπals, such as polyolefins, to corona discharge, ι.e., the loruzahon of a gas such as au m close proximity to a film surface. The ionization is initiated by a high voltage passed through a nearby electrode, causing oxidahon and other changes to the film surface. Corona treatment of polymenc matenals is disclosed in U.S. Patent No. 4,120,716, to BONET, issued October 17, 1978, which is hereby -ncoφorated in its entirety by reference thereto. BONET discloses improved adherence charactenshes of polyethylene, by subjectmg of the polyethylene to corona treatment, in order to oxidize the surface thereof. U.S. Patent No. 4,879,430, to HOFFMAN, also hereby mcoφorated m its entirety by reference thereto, discloses the use of corona discharge for the treatment of plashc webs for use meat cook-m packagmg, with the corona treatment of the mside surface of the web mcreasmg the adhesion of the film to the proteinaceous material. Although corona treatment is a method of treatment of the multdayer film of the present mvenhon, plasma freatment of the him may also be used. Figure 9 illustrates a perspective view of package 140 accordance with the present mvenhon, and Figure 10 iUustrates a cross-sectional view through section 10-10 of Figure 9. Package 140 compnses lap-seal casmg 144 which encases meat product 146, with casmg 144 bemg closed at both ends by cbps 142, with only one cbp bemg dlustrated m Figure 9. The lap seal porhon of casmg 144 compnses longitudmal outer casmg film edge 148 and longitudmal inner casmg film edge 150, as weU as overlap region 152 which contams the backseam seal. Casmg 144 compnses a multdayer casmg film m accordance with the backseamed casmg of the present mvenhon. The casmg film can be, for example, any one or more of prefeπed multdayer films 12, 30, 44, or 62, as descnbed m detad above Furthermore, although package 140 as dlustrated comprises a lap-seal casmg, altemahvely the package can comprise a butt-seal casmg (preferably, as dlustrated m Figure 5), m which latter mstance the casmg further comprises a butt-seal tape, preferably as described above and as iUustrated in Figures 5 and 7. In Figures 9 and 10, product 146 the package is preferably meat, more preferably cooked meat, and preferably mside surface 154 of casmg 144 is adhered to the meat product dunng cook-m. The packaged product can be made by a process compnsmg: (A) filling a backseamed casmg with a meat product, whereby a filled casmg is formed; (B) closmg the ends of the filled casmg so that the meat product is encased by the backseamed casmg, whereby a chub is formed; and (C) cooking the meat product encased m the backseamed casmg by subjectmg the chub to cook-m, so that the meat product adheres to the mside surface of the casmg. The backseamed casmg is a backseamed casmg accordmg to the present mvenhon, preferably a preferred backseamed casmg accordmg to the present mvenhon. Although in general the product in the package can be any cooked meat product, preferably the cooked meat product comprises at least one member selected from the group consistmg of poultry, ham, beef, lamb, goat, horse, hsh, bver sausage, mortadeUa, and bologna; more preferably, poultry, ham, beef and bologna; even more preferably, ham and roast beef. The mvenhon is dlustrated by the foUowmg examples, which are provided for the purpose of representation, and are not to be construed as limiting the scope of the mvenhon Unless stated otherwise, aU percentages, parts, etc. are by weight. EXAMPLE 1 A 3-3/4 mch wide (lay flat dimension) tube, called a "tape", was produced by the coextrusion process descnbed above and dlustrated m Figure 8, wherem the tape cross- section (from mside of tube to outside of tube) was as foUows: 3.0mιls of LLDPE#1 (80%) and lonomer #1 (20%) / 3.2 mils of a blend of EVA#1 (80%) and LMDPE#1 (20%) / 1.8 mil of anhydride grafted LLDPE#2 / 1.6 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 0.8 mils of anhydride grafted LLDPE#2 / 2.7 mils of a blend of EVA#1 (80%) and LMDPE#1 (20%) / 3.5 mils of LLDPE #3.; wherem: LLDPE#1 was DOWLEX" 2045.03 bnear low density polyethylene, obtamed from Dow Plashes, of Freeport, Texas; Ionomer#l was SURLYN' 6 1650 z c-based ionomer of ethylene/ methacry be acid copolymer, obtamed from E.I. DuPont de Nemours, of Wilmington, Delaware; LLDPE#2 was TYMOR* 1203 bnear low density polyethylene havmg an anhydnde funchonahty grafted thereon, obtamed from Morton International, of Chicago, Illinois; EVA#1 was PE 5269T (TM) ethylene vmyl acetate copolymer, obtamed from Chevron Chemical Company of Houston, Texas; EVOH was EVAL 1 *' LC-E105A polymenzed ethylene vmyl alcohol, obtained from Eval Company of America, of Lisle, Illinois; LMDPE#1 was DOWLEX" 2037 bnear medium density polyethylene, obtamed from Dow Plashes, of Freeport, Texas; NYLON#l was ULTRAMID " " B4 polyamide 6, obtamed from BASF corporation of Parsippany, New Jersey; NYLON#2 was GRILON" CF6S polyamide 6/12, obtamed from EMS-Ameπcan Gπlon Inc., of Sumter, S.C; LLDPE#3 was DOWLEX* 2244A bnear low density polyethylene, obtamed from Dow Plashes of Freeport, Texas; AU the resms were extruded between 380°F and 500°F, and the die was heated to approximately 420°F. The extruded tape was cooled with water and flattened, the flattened width bemg 3-3/4 mches wide in a lay-flat configuration. The tape was then passed through a scanned beam of an electronic cross-linking unit, where it received a total dosage of 64 kdo Grays (kGy), which is the equivalent of 4.5 mega Rads (MR). After madiahon, the flattened tape was passed through hot water for about a thud of a minute, the hot water having a temperature of from about 208°F to 210°F. The resultmg heated tape was mflated mto a bubble and onented mto a him tubmg havmg a lay-flat width of 9-3/4 mches and a total thickness of 2.3 mils. The bubble was very stable and the ophcs and appearance of the film were good. The film tubmg was determined to have 18% free shnnkage in the longitudmal direction and 29% free shnnkage in the transverse duection, when immersed in hot water for about 8 seconds, the hot water bemg at a temperature of 185°F, ι.e., usmg ASTM method D2732-83. The film tubmg, made as descnbed immediately above, was then slit so that it was converted mto film sheet. The film sheet was folded longitudmaUy around a formmg shoe with opposmg lengthwise film sheet edges bemg overlapped. Thereafter, a lap-seal backseam casmg was made by applymg a heat seal (usmg a hot seal bar, more particularly a Nishibe Model HSP-250-SA sealmg machme) longitudmaUy over the overlappmg regions of the film sheet. Dunng the backseammg operation, the film was posihoned so that the outside layer of the film tubmg (before it was sbt) formed the outside layer of the backseamed casmg, with the mside layer of the film tubmg formmg the mside layer of the backseamed casmg. The film backseamed well, i.e., without neckmg down around the formmg shoe to the extent that the film ruptured or the process was mterrupted. The resulting backseamed casmg, havmg with a lay-flat width of about 4 mches, was then cbpped at one end and hlled with chopped ham emulsion from the open end. The casmg was then closed with a second metal cbp and the section of meat-hlled casmg was cut free of the remamder of the casmg, forming a package which compnses the la j seal backseamed casing and the ham emulsion encased m the casmg. Several such packages were produced, and were thereafter cooked for about 4 hours at from about 145°F -170°F in a high humidity environment. The cooked casmgs were then cooled m a cooler kept at 32°F for several hours. The resulting chdled packages were then examined for purge and found to have no purge between the cooked meat product and the casmg film. Also, several samples of backseamed casmg were made, each contammg water as the packaged medium, and a mixture of 0.1% mmeral oil and 99.9% water. These casmgs were evaluated for seal strength survivability by cooking at 180°F for 12 hrs, and were found to have acceptable seal strength. The backseamed casing was also shined. The shirred casmgs were found to have acceptable seal strength, with very few or no pinholes bemg detected. EXAMPLE 2 A 3-3/4 mch wide (lay flat dimension) tape is produced by the coextrusion process descnbed above in Figure 8, wherem the tape cross-section (from mside to outside) is as foUows: 6.0 mils of LLDPE#3 (80%) and lON#1 (20%) / 1.1 mil of anhydride grafted LLDPE#2 / 2.0 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 1.1 mils of anhydnde grafted LLDPE#2 / 6.0 mils of LLDPE #3, wherem all the resms are as identified m Example 1 above. AU the resms are extruded at a temperature of from about 380°F to 500°F, and the die is at approximately 420°F. The extruded tape is cooled with water and flattened, the flattened width bemg 3-3/4 mches wide, m a lay-flat configuration. The tape is then passed through a scanned beam of an electronic cross-bnkmg unit, where it receives a total dosage of 64 kdo Grays (kGy), which is the equivalent of 4.5 mega Rads (MR). After uradiahon, the flattened tape is passed through hot water at 208°F to 210°F for a period of about a thud of a mmute, immediately after which the heated tape is mflated mto a bubble, and is onented mto tubmg havmg a lay-flat width of 9-3/4 mches and a total thickness of 2.3 mils. The bubble is stable and the ophcs and appearance of the film are good. The resultmg film has 18% free shnnkage m the longitudinal direction and 29% free shnnkage the transverse duection when it is immersed hot water at 185°F, i.e., usmg ASTM method D2732-83. The film tubmg, made as described immediately above, is then sbt lengthwise, converting the him tubmg mto film sheet. The him sheet is folded longitudmaUy around a forming shoe with longitudmaUy opposmg edges bemg overlapped, with the overlappmg regions thereafter bemg jomed by applymg a heat seal, usmg a hot-seal bar, longitudmally over the overlap, to form a lap seal usmg a Nishibe Model HSP-250-SA sealmg machme. Dunng the backseammg operahon, the fdm is posihoned so that the outside layer of the him tubmg (before it is sbt) coπesponds with the outside layer of the backseamed casmg, with the mside layer of the film tubmg coπesponding with the mside layer of the backseamed casmg. The film backseams well. The resulhng backseamed casmg, havmg a lay-flat width of about 4 mches, is then cbpped at one end and lled with chopped ham emulsion from the open end. The tubmg is then closed with a second metal cbp and the section of meat-fdled casmg is cut free of the remamder of the casmg, forming a package which compnses the lap-seal backseamed casmg and the ham emulsion encased m the casmg. Several packages are so made. Each of the packages is cooked for about 4 hours from 145°F -170°F m a high humidity envuonment. The cooked packages are then cooled a cooler kept at 32°F for several hours. The resulhng cooked, chilled packages are examined for purge and found to have no purge between the cooked meat product and the mside surface of the backseamed casmg. Several additional packages are made from the backseamed casmg, each of these packages contammg a product compnsmg 99.9% water and 0.1 % mmeral oil. These casmgs are evaluated for seal strength survivabibty by cookmg at 180°F for 12 hours, and are found to have acceptable seal strength. EXAMPLE 3 A 3-3/4 mch wide (lay flat dimension) tubular tape is produced accordmg to Example 1. The tape cross-section (from mside of tube to outside of tube) is as foUows: 6.0 mils of Terpolyolefrn# 1/ 1.1 mil of anhydride grafted LLDPE#2 / 2.0 mils of a blend of Nylon# 1 (50%) and Nylon#2 (50%) / 1.1 mils of anhydride grafted LLDPE#2 / 6.0 mils of LLDPE #3, wherem. Terpolyolehn#l is LOTADER' 6 3210 ethylene/butyl acrylate/ maleic anhydnde terpolymer, compnsmg about 3% anhydride functionality, obtamed from Elf Atochem North America, Inc., of Phdadelphia, PA, and all the other resms are as identified m Example 1 above. AU the resms are extruded between 380°F and 500°F, and the die is at approximately 420°F. The extruded tape is cooled with water and flattened, the flattened width bemg 3-3/4 mches wide, in a lay-flat configuration The tape is then passed through a scanned beam of an electronic cross-bnkmg unit, where it receives a total dosage of 64 kdo Grays (kGy), which is the equivalent of 4.5 mega Rads (MR) After uradiahon, the flattened tape is passed through hot water at 208°F to 210°F, mflated mto a bubble, and onented mto tubmg havmg a lay-flat width of 9-3/4 mches and a total thickness of 2.3 mls. The bubble is stable and the ophcs and appearance of the resulhng tubmg film are good. The tubmg fdm has 18% free shnnkage m the longitudmal duection and 29% free shnnkage m the transverse duection, when immersed m hot water for 8 seconds at 185°F, ι.e., accordmg to ASTM method D2732- 83. The tubmg him is then sbt mto film The film is folded longitudmally around a formmg shoe with opposmg longitudmal edges bemg overlapped, with the overlappmg regions then bemg joined by applying a heat seal (usmg a hot-seal bar) longitudmaUy over the overlap, to form a lap-seal backseamed casmg, usmg a Nishibe Model HSP-250-SA sealmg machme. Dunng the backseaming operahon, the film is posihoned so that the layer which corresponds with the outside layer of the film tubmg (before it is sbt) forms the outside layer of the resulhng backseamed casmg, with the layer which coπesponds with the mside layer of the film tubmg forms the mside layer of the resulhng lap-seal backseamed casmg. The film backseams well, i.e., without neckmg down on the formmg shoe to the extent that the film either ruptures or interrupts the process. This resultmg backseamed casmg, havmg a lay-flat width of about 4 mches, is then cbpped at one end and filled from the open end with chopped ham emulsion. The tubmg is then closed with a second metal cbp, resulhng m a package, with the package thereafter bemg cooked for about 4 hours from 145°F -170°F m a high humidity envuonment. The packages contammg cooked ham emulsion are then cooled in a cooler for several hours, the cooler havmg a temperature of about 32°F. The resulhng chdled packages are then examined for purge and found to have no purge between the product and the plashc matenal. Several other backseamed casmgs are fdled with a mixture of 99.9% water and 0.1% mmeral od. These casmgs are evaluated for seal strength survivabibty by cookmg at 180°F for 12 hrs, and are found to have acceptable seal strength. EXAMPLE 4 A 3-3/4 mch wide (lay flat dimension) annular tape, was produced by the coextrusion process descnbed above and dlustrated m Figure 5, wherem the tape cross- section (from mside to outside) was as follows. 3.3 mils of a blend of EVA#1 (80%) and HDPE#1 (20%) / 0.9 mils of anhydride grafted LLDPE#2 / 1.8 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 1.6 mils of anhydride grafted LLDPE#2 / 2.2 mils of a blend of EVA#1 (80%) and HDPE#1 (20%) / 3 1 mils of LLDPE #3, wherem. EMAA#1 was NUCREL" ARX 84-2 ethylene/ methacrylic acid copolymer, obtamed from E.I. DuPont de Nemours, of Wilmington, Delaware; HDPE#1 is FORTIFLEX*J60-500C-147 high density polyethylene, obtamed from Solvay Polymers, Inc., Deer Park, Texas; and all other resms are as identified m Example 1 above. AU the resms were extruded at a temperature of from about 380°F to 500° F, and the die was heated to approximately 420°F. The extruded tape was cooled with water and flattened, the flattened width bemg 3-3/4 mches wide, m a lay-flat configuration. The tape was then passed through a scanned beam of an electronic cross-bnkmg unit, where it received a total dosage of 64 kdo Grays (kGy), which is the equivalent of 4.5 mega Rads (MR). After uradiahon, the flattened tape was passed through hot water at 208°F to 210°F, inflated mto a bubble, and oriented mto film tubmg havmg a lay-flat width of 9-3/4 mches and a total thickness of 2.3 mds. The bubble was very stable and the ophcs and appearance of the fdm tubmg were good. The resulhng fdm tubmg had 18% free shnnkage in the longitudinal direction and 29% free shnnkage m the transverse duection, when immersed for 8 seconds hot water at 185°F, i.e., usmg ASTM method D2732-83. The film tubmg, made as described immediately above, was then sbt longitudmally, thereby converting the film tubmg mto im sheet The film sheet was folded longitudmaUy around a forming shoe, with opposmg longitudmal edges bemg overlapped, with the overlapping regions of the film sheet thereafter bemg jomed by applymg a heat seal (usmg a hot-seal bar) longitudmaUy over the overlap, usmg a Nishibe Model HSP-250-SA sealmg machme. Durmg the backseaming operahon, the film was posihoned so that the outside layer of the film tubmg (before it was sbt) coπesponds to the outside layer of the resulhng backseamed casing, with the mside layer of the film tubmg correspondmg to the mside layer of the backseamed casmg. The film backseamed well and appeared to have acceptable seal strength. The film was also evaluated for protem adhesion and found to have satisfactory purge resistance with an mtermediate quality ham product. EXAMPLE 5 A 5-3/4 inch wide (lay flat dimension) annular tape was produced by the coextrusion process described above and dlustrated Figure 8, wherem the tape cross- section (from mside the tube to outside the tube) was as follows- 3.0 mils of LLDPE#3 (80%) and EAA#1 (20%) / 3.4 mils of a blend of EVA#1 (60%), HDPE#1 (20%) and PIG#1 (20%)/ 1.2 mil of anhydride grafted LLDPE#2 / 1.7 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / l.lmils of anhydride grafted LLDPE#2 / 2.7 mils of a blend of EVA#1 (60%), EAA#1(20%) and PIG#1 (20%)/ 3.4 mils of LLDPE #3, wherem: EAA#1 is PRIMACOR" 1410 ethylene/ acrylic acid copolymer, obtamed from The Dow Chemical Company, of Midland, Michigan; PIG#1 is EPE 10214-C opaque white color concentrate, obtained from Teknor Color Company, of Pawtucket, R.I.; all other resms were as identified in Examples 1-4, above AU the resms were extruded at a temperature of from about 380°F to 500°F, and the die was heated to approximately 420°F The extruded tape was cooled with water and flattened, the flattened width being 5-3/4 mches, in a lay-flat configuration. The tape was then passed through a scanned beam of an electronic cross-bnkmg unit, where it received a total dosage of 64 kdo Grays (kGy), which is the equivalent of 4.5 mega Rads (MR). After uradiahon, the flattened tape was passed through hot water for about a thud of a mmute, the hot water havmg a temperature of from about 208°F to 210°F. Immediately upon emerging from the hot water bath, the heated tape was mflated mto a bubble, and onented mto a fibn tubmg havmg a lay-flat width of 15 inches and a total thickness of 2.3 mds. The bubble was very stable and the ophcs and appearance of the film tubmg were good. The resulhng him tubmg had 18% free shrmkage m the longitudmal direction and 29% free shnnkage the transverse direction when immersed in hot water at 185°F for 8 seconds, ι.e., usmg ASTM method D2732-83. The tubmg, made as descnbed immediately above, was then sbt mto him, and was converted mto a lap-seal backseamed casmg m the manner descnbed in Example 1, above. The film backseamed very well. The lap-seal backseamed casmg, havmg a lay-flat width of about 4 mches, was then clipped at one end and hUed with chopped ham emulsion from the open end. The casmg was then closed with a second metal cbp, and the section of meat-filled casmg is cut free of the remamder of the casing, forming a package which comprises the lap-seal backseamed casmg and the ham emulsion encased in the casmg. -several packages were produced m this manner, with the packages thereafter bemg cooked for about 4 hours at a temperature of from 145°F to 170°F, m a high humidity envuonment. The resulhng cooked casmgs were then cooled m a cooler kept at 32°F for several hours. The resulhng chdled casmgs were then examined for purge and found to have no purge between the product and the plastic matenal. Several addihonal packages were produced, these addihonal packages usmg the same backseamed casmg, but encasing a product contammg 99.9% water and 0.1 % mmeral oil. These casmgs were evaluated for seal strength survivabibty by cookmg at 180°F for 12 hrs, and were found to have acceptable seal strength. The slit film was also corona-treated to a surface energy level of 62 dynes/cm, and then immediately folded (and overlapped) longitudmally about a second formmg shoe havmg a size so that the resulting lap-seal backseamed casmg had a lay-flat width of about 5-1/4 mches. This backseamed casmg was then cbpped at one end and filled with liver sausage emulsion from the open end. The casmg was then closed with a second metal cbp, and the section of meat-fdled casmg was cut free of the remamder of the casmg, forming a package which compnsed the lap-seal backseamed casmg and the bver sausage emulsion encased in the casmg. Several packages were produced in this manner, with the packages thereafter bemg cooked for about 4 hours from 145°F -170°F in a high humidity envuonment. The resulhng packages contammg cooked meat were then cooled in a cooler kept at 32°F for several hours. The resulting chilled packages were then examined for purge and found to have good purge-resistance at the casing lay-flat edges, i.e., where the edges had rubbed against the formmg shoe. Thus, even though the corona treatment at the casmg lay-flat edges had been 'buffed off, there was still sufficient affmity of the untreated meat-contact surface of the casmg (compnsmg ethylene/ acrylic acid copolymer) to the liver sausage to prevent fattmg out at that locahon. The above backseamed casing was also sh red. The shured casmgs were found to have acceptable seal strength, with very few or no pinholes bemg detected. EXAMPLE 6 A 5-inch tape was produced by the coextrusion process described above and illustrated in Figure 8, wherein the tape cross-section (from mside of tube to outside of tube) was as follows: 3.0 mils of LLDPE #4 / 5.0 mils of a blend of EVA#2 (80%) and LLDPE #1 (20%) / 1.0 mil of anhydride grafted LLDPE#2 / 2.5 mils of Nylon#2 / 1.1 mds of EVOH / 1.6 mils of anhydnde grafted LLDPE#2 / 2.4 mils of a blend of EV A#2 (80% ) and LLDPE#1 (20% )/ 3.0 mils of LLDPE #3, and wherem: LLDPE#4 was PLEXAR" PX 360 anhydnde grafted Imear low density polyethylene, obtamed from Quantum Chemical Company, of Cmcmnah, Ohio; EVA#2 was ELVAX" 3128 ethylene/ vmyl acetate copolymer, obtamed from E.l. DuPont de Nemours & Co., of Wilmington, Delaware; and and all other the resms are as identified m Examples 1-5, above. The tape was made and oriented into 15-mch wide tubmg film the manner described m Example 1, above. One significant difference between this film and the films of Examples 1-5 is that the film of this example has a core layer comprising only Nylon #2, i.e., nylon 6/12, rather than contammg the blend of nylon 6 and nylon 6/12 The tape oriented acceptably, though it's onentabihry was/is significantly mfenor to that of the tapes of Examples 1-5. The film tubmg was converted mto film sheet, which m turn was converted mto lap- seal backseamed casmg m the manner described m Example 1, above. The film backseamed acceptably, though not as weU as the films of Examples 1-5. Also, when evaluated for seal strength, it was/ is discovered that, whde the backseamed tubmg of this example probably had acceptable seal strength, it's seal strength was/ is mfenor to that of the films of Examples 1-5. EXAMPLE 7 (Comparative) A 5-1/8 mch, lay-flat width, annular tape was produced by the coextrusion process described above and illustrated m Figure 8, wherem the tape cross-section (from mside the tube to outside the tube) was as follows: 3.2 mils of LLDPE #4 / 5.2 mils of a blend of EVA#2 (65%), LLDPE #1 (20%) and PIG#1 (15%) / 0.9 mils of anhydride grafted LLDPE#2 / 0.7 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 1.7 mils of anhydride grafted LLDPE#2 / 1.9 mils of a blend of EVA#2 (65%), LLDPE#1 (20%) and P1G#1 (15%)/ 3.2 mils of LLDPE#3, wherem all the resms are as identified m Examples 1-6 above. All the resms were extruded at a temperature of from about 380°F and 530°F, and the die was heated to approximately 420°F The extruded tape was cooled with water and flattened, and had a width of about 5-1/8 mches. This tape was then passed through the scanned beam of an electronic crosslmkmg unit where the tape received a total dosage of 64 kGy. After irradiation, the flattened tape was passed through hot water for about a third of a mmute, the hot water havmg a temperature of from about 204°F to 210°F. The resultmg heated tape was then mflated mto a bubble m a manner so that the heated tape was converted mto a biaxially oriented film tubmg. The oriented film tubmg had a lay-flat width of 15 inches The multilayer film havmg a total thickness of 2.3 mils, and a free shrmk in the longitudmal direction of about 18 percent, and 29 percent m the transverse direction. Free shrmk was determmed by immersmg the film m hot water at 185°F for about 8 seconds, i.e., usmg ASTM method D2732-83. The tubmg, made as described unmediately above, was then sbt mto film. The film was folded longitudmaUy about a forming shoe with opposed edges bemg j oined by applymg a heat seal longitudmaUy over the overlappmg regions of the film, m an attempt to form a lap seal usmg a Nishibe Model HSP-250-SA sealmg machme. Durmg the backseammg operahon, the film was posihoned so that the outside layer of the tubmg (before it was sbt) coπesponded with the outside layer of the backseamed tubmg, with the inside layer of the tubmg coπesponding with the mside layer of the backseamed tubmg. However, durmg this backseammg step, the film necked down a substanhal degree on the forming shoe, resultmg in mtermittent film rupture. Thus, the film was not backseamable. EXAMPLE 8 (Comparative) A 3-1/2 inch lay-flat annular tape was produced by the coextrusion process described above and illustrated in Figure 8, wherem the tape cross-section (from mside of tube to outside of tube) was as follows: 3.2 mils of LLDPE #4 / 4.9 mils of a blend of EVA#2 (65%), LLDPE #1 (20%) and PIG#1 (15%) / 1.0 mil of anhydride grafted LLDPE#2 / 2.5 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 1.6 mils of anhydride grafted LLDPE#2 / 1.9 mils of a blend of EVA#2 (65%), LLDPE#1 (20%), and PIG#1 (15%) / 3.2 mils of LLDPE #3, wherem all resms are as identified m Example 7 (Comparative), as set forth above. The tape was made and oriented mto 10 mch tubmg him m a manner as described above m Example 7 (Comparative). The only substanhal difference between the film of this example and the film of Example 7 (Comparative) is the thickness of the nylon core layer, i.e., this example, the nylon core layer was about 3 1 /2 times as thick as the thickness of the nylon core layer in the film of Example 7 (Comparative). The resulhng film tubmg was converted mto film sheet and was thereafter further converted mto a backseamed casmg, these conversion processes bemg earned out m the same manner as set forth in Example 7 (Comparahve), above. However, contrary to the film of Example 7 (Comparahve), this film did not undergo substanhal necking down on the formmg shoe, and underwent backseaming successfuUy. Nevertheless, the resulting backseamed casmg of this example is not an example of the present mvenhon because it does not have sufficient purge resistance. However, this example demonstrated that a mmunum thickness of the nylon core layer is enhcal to the backseamabihty of a heat-shrinkable film. The backseamed casmg was also shured. The shiπed casmgs were found to have acceptable seal strength, with very few or no pinholes bemg detected. EXAMPLE 9 (Comparahve) A 5-1/8 mch tubular tape was produced by the coextrusion process described above and illustrated m Figure 8, wherem the tape cross-sechon (from mside of tube to outside of tube) was as follows: 3.0 mils of a blend of LLDPE #4 (90%) and NYLON#2 (10%) / 5.2 mils of a blend of LLDPE #2 (80%) and EAO#l (25%) / 2.0 mil of anhydride grafted LLDPE#2 / 1.1 mil of EVOH / 1 7 mils of anhydride grafted LLDPE#2 / 3.2 mils of a blend of LLDPE#2 (80%) and EAO#l (20%) / 3.0 mils of LLDPE#3, wherem EAO#l was EXACT 4011 (TM) homogeneous ethylene/ alpha-olefin copolymer, obtamed from the Exxon Chemical Company, of Baytown, Texas; and all other resms are as identified m Examples 1-5 and Comparahves 1-2 above. All the resms were extruded at a temperature of from about 380°F to 530°F, and the die was at a temperature of about 420°F. The extruded tape was cooled with water and flattened, the flattened width bemg 5-1/8 mches. This tape was then passed through the scanned beam of an electronic crosslmkmg unit where it received a total dosage of 64 kGy. After irradiation, the flattened tape was passed through hot water for about a third of a minute, the hot water havmg a temperature of from about 204°F to 210°F. Upon emergmg from the hot water, the resultmg heated tape was immediately mflated mto a bubble, and oriented to result in an oriented film tube havmg a lay-flat width of 14 mches. This film had a total thickness of 2.3 mils. The tape did not orient as well as the films described m Example 1, 4, 5, 7 (comparahve), and 8 (comparative), due to the absence of the nylon core layer. The film had a free shrmk of about 25 percent m the longitudmal direction, and about 29 percent m the transverse direction. Free shrmk was determmed by immersmg the film m hot water for about 8 seconds, the water havmg a temperature of about 185°F, i.e., usmg ASTM method D2732-83. The tubmg film was converted into film sheet which was backseamed as descnbed m Example 1. However, durmg backseammg the him necked down severely on the formmg shoe (much more severely than in the case of Example 7 (Comparahve), thereby rupturmg itself and disrupting the process. Thus, this film was not a viable backseamable film Thus, not only did the absence of the nylon core layer affect oπentabihty of the film, but the resultmg him also was not backseamable This comparative example highlights the importance of the nylon core layer, for backseammg as well as oπentabihty. EXAMPLE 10 (Comparahve) A 5-1/8 mch tubular tape was produced by the coextrusion process as described above and illustrated m Figure 8, wherem the tape cross-sechon (from mside the tube to outside the tube) was as follows: 3.0 mils of a blend of LLDPE#4 (80%) and NYLON#2 (20%) / 6.0 mils of a blend of LLDPE#2 (80%) and EAO#l (20%) / 1.0 mil of anhydπde grafted LLDPE#2 / 1.6 mils of a blend of NYLON#l (50%) and NYLON#2 (50%) / 1.7 mils of anhydπde grafted LLDPE#2 / 3.0 mds of a blend of LLDPE#2 (80%) and EAO#l (20%) / 3.0 mils of LLDPE#3, wherem all resms are as identified m Examples 1-9 above. The tape was coextruded and oriented mto 14 mch wide tubmg film as described above m Example 9 (Comparahve). The only substantial difference between this film and the film of Example 9 (Comparative) was the incorporation of the nylon core layer m the film of this example The film oriented acceptably and far supenor to the film of Example 9 (Comparahve). The tubmg was then sbt into film and was backseamed by a process as described m Example 1 above. The im backseamed weU, and exhibited good seal strength. However, even though the film of this example backseamed acceptably, it is not a preferred film because it exhibited insufficient protem adhesion, i.e., msufficient purge- resistance. However, a compaπson of the backseamabdity of this fdm with the backseamabdity and onentabihty of the film of Example 9 (Comparahve), mdicate that the presence of the nylon core layer is cnhcal to both backseamabdity and onentabihty of the resulhng heat-shrinkable film. EXAMPLE 11 (Comparahve) A 5-mch tubular tape was produced by the coextrusion process described above and illustrated m Figure 8, wherem the tape cross-sechon (from mside the tube to outside the tube) was as follows: 3.2 mils of LLDPE #4 / 4.6 mils of a blend of EVA#2 (80%) and LLDPE #1 (20%) / 1.0 mil of anhydride grafted LLDPE#2 / 1.9 mils of a blend of Nylon#l (50%) and Nylon#2 (50%) / 1.9 mils of anhydride grafted LLDPE#2 / 3.2 mils of a blend of EVA#2 (80%) and LLDPE#1 (20%)/ 3.1 mils of LLDPE #3, and wherem all the resms are as identified in Example 7 (Comparahve), above. The tape was made and oriented mto 15 mch lay-flat width him tubmg the manner described above m Example 8 (Comparahve). The only substanhal difference between this film of this example and the film of Example 8 (Comparahve) is that the film of this example was pigmented. The film was converted mto film sheet and was backseamed as described m Example 1, above. The film sheet backseamed well. The backseamed casmg was then used to prepare a number of packages which contained intermediate quahty ham emulsion. The ham emulsion was prepared, cooked, and chdled the manner described m Example 1. The resulhng chdled packages were found to have signihcant and unacceptable purge between the meat-contact surface and the cooked meat product. Thus, this example mdicates that the protein-adhesion charactenshc of Plexar" PX 360 anhydnde- contammg polyolefin resm, which comprises less than about 1/2% anhydnde funchonahty, is insufficient for purge resistance with intermediate or poor quahty ham products, i.e., products which are relahvely low in protem, and are therefore more difficult for obtaining film-to-meat adhesion. The ham product was the same as the ham product used m Example 1. The film sheet was also corona-treated to a surface energy level of 62 dynes/cm, and thereafter backseamed, with the resultmg backseamed casmg being used as described immediately above, i.e., to package intermediate quality ham product. In an exammation of the chilled casmgs, purge was found at areas of the casing corresponding to the lay-flat edges, i.e., where the edges had rubbed agamst the formmg shoe, thereby causmg msufficient protem adhesion. The rubbmg of the edges on the forming shoe presumably "buffed" the corona treated surface at that location. The buffing off of the corona freatment by the formmg shoe resulted in too little purge resistance. Without corona treatment, the purge-resistance afforded by the anhydride- containing meat-contact resm (Plexar " PX360, which comprises less than 1 % anhydride functionality), without corona treatment (smce it had been buffed off), is msufficient to prevent fatting out. The bver sausage product used is the same product used in the liver sausage cook-testing of Example 5. The backseamed casmg was also shirred. The shiπed casmgs were found to have acceptable seal strength, with very few or no pinholes bemg detected. EXAMPLE 12 (Comparahve) A 4-inch tape was produced by the coextrusion process described above in Figure 8 wherein the tape cross-sechon (from mside of tube to outside of tube) was as follows: 3.0 mils of EPC#1 / 5.0 mils of a blend of EVA#3 (70%) and EA0#2 (30%) / 1.4 mil of anhydnde grafted LLDPE#2 / 1.2 mils of EVOH / 1.3 mils of anhydride grafted LLDPE#2 / 5.0 mils of EPC#1, and wherem: EPC#1 was ELTEX P KS409, a propylene/ ethylene copolymer, obtamed from from Solvay Polymers, Inc., of Deer Park, Texas. EVA#3 was PE1651CS28, 6.5% EVA copolymer, obtamed from Rexene Corporahon, of Dallas, Texas. EAO#2 was TAFMER (TM) P-0480, an ethylene/ propylene copolymer, obtamed from Mitsui Petrochemical Industries, Ltd., of Tokyo, Japan; and all the other resms are as identified Example 1 above. The tape was made and oriented mto 12 mch wide tubmg film m a manner as described m Example 1, above. The tape onented acceptably, though the onentabihty of the tape was mfenor to the onentabihty of the tape of Example 1, probably because the tape of Example 1 contamed a core layer compnsmg nylon. The casmg him, made as descnbed immediately above, was then sbt mto him sheet The film sheet was then corona treated on a flat-sheet corona treater to achieve a surface energy level of about 48 dynes/ cm on the mside layer of the tubmg film, i.e., the outer film layer which was to form the corona-treated mside layer of the casmg. After corona treating, the him sheet was folded longitudmaUy about a forming shoe with opposmg edges bemg overlapped as descnbed above. The resulhng overlappmg region of the him was then joined by applymg a heat seal longitudmally to the overlap, to form a lap seal, usmg a Nishibe Model HSP-250-SA sealmg machme. Durmg the backseammg operation, the film was positioned so that the corona-treated surface formed the mside layer of the resulting lap- seal casmg. Although the im did not contain a core layer compnsmg nylon and/or polyester, the fdm backseamed acceptably. It is bebeved that the presence of the outer film layers compnsmg propylene/ ethylene copolymer assisted in preventing the him from shrmkmg back so hghtly agamst the formmg shoe that the process would have been interrupted. The backseamed casmg was then used to prepare a number of packages which contamed bver sausage. The packages were prepared, cooked, and chilled m the manner descnbed m Example 1. Whde the lap-seal backseamed casmg was found to have reasonable seal strength, it was not as preferred as the casmg of the present mvenhon, due to less seal strength dunng cook-m, and more seal pucker after cook-m, compared with the casmg films of Examples 1 and 5. Furthermore, it was found that durmg cook-m fatting out occuπed at regions correspondmg with the casmg lay-flat edges, i.e., where the corona- treatment had been buffed off by the formmg shoe EXAMPLE 13 A 5-mch tape was produced by the coextrusion process described above and illustrated in Figure 8, wherein the tape cross-sechon (from inside of tube to outside of tube) was as follows: 3.7 mils of a blend of EPC#2 and EAO#3 / 2.7 mils of anhydπde grafted LLDPE#2 / 2.0 mils of Nylon#2/ 1.0 mils of EVOH / 2.6 mils of anhydride grafted LLDPE#2 / 4.0 mils of a blend of EPC#2 and E AO#3, and wherem: EPC#2 was NOBLEN (TM) W531D propylene/ ethylene copolymer, obtamed from Sumitomo Chemical Company, Limited, of Tokyo, Japan; EAO#3 was TAFMER (TM) A-4085, an ethylene-butene copolymer obtained from Mitsui Petrochemical Industries, Ltd., of Tokyo, Japan; and all the other resms are as identified Example 1 above. The tape was made and oriented mto 14-inch wide tubmg film a manner as described Example 1, above. The tape oriented acceptably, though the onentabihty of the tape was mfenor to the onentabihty of the tape of Example 1, probably because the tape of Example 1 contamed a core layer compnsmg a more prefeπed nylon composihon. The casmg him, made as descnbed immediately above, was then sbt mto im sheet and corona treated and backseamed m the manner descnbed in Example 12, above. The film backseamed acceptably. After makmg chubs from the casmg film packed with bver sausage and subjecting the chubs to cook-m as descnbed m Example 12, the lap-seal backseamed casmg was found to have reasonable seal strength, it was not as prefeπed as the casmg of the present mvenhon, due to less seal strength dunng cook-m, and more seal pucker after cook-m, compared with the casmg films of Examples 1 and 5. Furthermore, it was found that dunng cook-m fatting out occuπed at regions coπespondmg with the casmg lay-flat edges, i.e., where the corona-treatment had been buffed off by the forming shoe. EXAMPLE 14 A 5-1 /2-tnch tape was produced by the coextrusion process described above m Figure 8 wherein the tape cross-sechon (from mside of tube to outside of tube) was as follows: 5.9 mils of a blend of EVA#3 (70%) and EA0#2 (30%) / 1.5 mil of anhydride grafted LLDPE#2 / 1.2 mds of EVOH / 3.0 mils of NYLON#2/ 0.9 mils of anhydride grafted LLDPE#2 / 2.4 mils of a blend of EVA#3 (70%) and EA0#2 (30%) / 2.9 mils of EPC#1, and wherein- all the resms are as identified m Example 1 & 7 above. The tape was made and oriented mto 16-mch wide tubmg film by a process as described above in Example 1. Although the tape onented acceptably, the onentabihty of the tape was mfenor to the onentabihty of the tape of Example 1, probably because the tape of Example 1 contamed a core layer compnsmg a more prefeπed nylon composihon. The casmg film, made as described immediately above, was then sbt mto film sheet and corona treated and backseamed m the manner descnbed m Example 12, above. The film backseamed acceptably. The resulhng lap-seal backseamed casmg was then shured, with the shured casmg then bemg evaluated for seal strength. The results mdicated that whde the seal strength of the shirred casmgs was good, the shirring process resulted a low but more than preferred rate of formahon of pinholes alongside the backseam. The results obtamed from Examples 1-6, which are accordmg to the present mvenhon, as well as the results obtamed from Examples 7-14, reveal several important and unexpected results obtamed by the present mvenhon. First, it has been discovered that a core layer of nylon substantially reduces, or prevents, film neck-down on the formmg shoe durmg the backseammg process, so long as the nylon core layer has at least a certam mmimum thickness. While the amount of nylon needed probably depends on a variety of factors, such as composition of the remamder of the film, overall physical properties, etc., it appears that the nylon layer needs to have a thickness of at least about 5%, based on the total thickness of the multilayer film, if necking down on the formmg shoe is to be substantially reduced or prevented. Second, the selection of the type of nylon can have a significant impact on the performance of the film, not just with regard to backseamabdity, but also with regard to other desired characteristics, such as improved onentabihty, improved sealabihty, improved seal strength, and improved pinhole-resistance. Whereas seal strength is simply the strength of the seal as measured by ability to withstand cook-m, sealabihty is the ease of sealmg, i.e., incorporates a sealing wmdow temperature, seal consistency between batches, and seal reliability durmg cook-m. For example, a compaπson of the performance of the backseamed casmgs according to Example 6 versus Example 11 reveals that the core layer of a blend of nylon 6 (50%) and nylon 6/12 (50%), provides better tape onentabihty, better sealabihty, better backseamabdity, and better seal strength. The influence of the nylon core layer on backseamabdity is unexpected m that it cannot be explamed by the modulus, free shrmk, or shrmk force imparted by the nylon-contammg layer. Moreover, the significant influence of the nylon core layer on seal strength is unexpected m that the nylon core layer is not servmg as a sealant layer. Third, a comparison of Examples 12-14 with themselves and with Examples 1-11 mdicates several advantages of the backseamed casmg accordmg to the present mvention. First, although the core layer compnsmg polyester and/or hrst nylon, or first nylon havmg a meltmg point of at least 300°F, provides advantages m backseamabdity, i.e., of prevention of neckmg down on the formmg shoe, this advantage can m some cases (dependmg on the remamder of the fdm composihon) be obtamed even without the presence of such a core layer, as is apparent from a comparison of Example 12 (Comparahve) with Example 13 (Comparahve). Second, a compaπson of Example 13 (Comparahve) with Examples 1 and 5 mdicates that even if a nylon core layer is present and the film backseams acceptably, outer layers compnsmg propylene/ ethylene copolymers are associated with seal puckermg, which is aesthetically and commercially less than preferred, as well as a less than preferred level of seal cook-m survival. Third, a comparison of Example 14 with Examples 1 and 5 mdicates that the casmgs accordmg to Examples 1 and 5 shirred without detectable pmhole formation, m contrast to the comparative casmg of Example 14. Also, a comparison of Examples 6, 13, and 14 with Examples 1 and 5, mdicates that a more preferred nylon composihon can significantly enhance the onentabihty of the tape durmg the formation of the film tubmg. Although the present invention has been described with reference to the preferred embodiments, it is to be understood that modificahons and variahons of the invention exist without departing from the principles and scope of the invention, as those skilled in the art will readily understand. Accordingly, such modifications are in accordance with the claims set forth below.

Claims: WHAT IS CLAIMED IS: 1. A backseamed casmg compnsmg a heat-shrmkable casing film compnsmg: (A) a first outer layer servmg as an mside casmg layer, the hrst outer layer compnsmg a hrst polyolefm comprising at least one member selected from the group consistmg of: (l) ethylene/ unsaturated acid copolymer, propylene/ unsaturated acid copolymer, and butene/unsaturated acid copolymer, wherem the unsaturated acid is present m an amount of at least 4 weight percent, based on the weight of the copolymer; and (n) anhydride-containing polyolefm compnsmg an anhydride-functionality, wherem the anhydride funchonahty is present an amount of at least 1 weight percent, based on the weight of the anhydnde-contammg polyolefm; (B) a second layer compnsmg at least one member selected from the group consistmg of polyester, and first polyamide; and (C) a third layer servmg as an outside casmg layer, the third layer compnsmg at least one member selected from the group consistmg of second polyolefin, polystyrene, and second polyamide; and wherem the second layer is between the first layer and the third layer, and the second layer has a thickness of at least about 5% of a total thickness of the heat- shrmkable casmg film. 2. The backseamed casmg accordmg to claim 1, wherem the third layer compnses the second polyolefm. 3. The backseamed casmg accordmg to claim 2, wherem the second layer comprises the first polyamide. 4. The backseamed casmg according to claim 2, wherein the first layer further comprises a third polyolefin compnsmg at least one member selected from the group consistmg of polyethylene homopolymer, polyethylene copolymer, polypropylene homopolymer, polypropylene copolymer, polybutene homopolymer, and polybutene copolymer. 5. The backseamed casmg accordmg to claim 4, wherem the second polyolefin has a vicat softenmg pomt of at least 90°C, and the third polyolefin has a vicat softenmg pomt of at least 90°C. 6. The backseamed casmg accordmg to claim 5, wherem the first polyolefm comprises an ethylene/ unsaturated acid copolymer havmg an unsaturated acid mer present m an amount of at least 9 percent, based on the weight of the ethylene/ unsaturated acid copolymer. 7 The backseamed casing according to claim 5, wherein the third layer comprises the second polyamide. 8. The backseamed casmg accordmg to claim 2, wherem the hrst polyolefm comprises an ethylene/ unsaturated acid copolymer, the unsaturated acid is present in an amount of at least 6 weight percent, based on the weight of the ethylene/ unsaturated acid copolymer. 9 The backseamed casmg accordmg to claim 8, wherem the casmg film further comprises a fourth layer, the fourth layer bemg an mner layer servmg as an 0 2 -barπer layer, the fourth layer compnsmg at least one member selected from the group consistmg of ethylene/ vmyl alcohol copolymer, polyvinylidene chloride copolymer, polyethylene carbonate copolymer and polyamide. 10. The backseamed casmg accordmg to claim 9, wherem the second layer and the fourth layer are directly adhered. 11. The backseamed casmg accordmg to claim 9, wherem the casmg film further comprises a fifth layer and a sixth layer, wherem: the fifth layer is between the hrst layer and the second layer, and the sixth layer is between the second layer and the third layer; the fifth layer comprises at least one member selected from the group consistmg of fourth polyolefm, polystyrene and polyurethane; and the sixth layer comprises at least one member selected from the group consistmg of fifth polyolefm, polystyrene and polyurethane. 12. The backseamed casmg accordmg to claim 11, wherein a ratio of- (a) a sum of the thickness of the first layer and the hfth layer; to (b) a sum of the thickness of the third layer and the sixth layer is from about 0.7:1 to 1.3:1. 13. The backseamed casmg according to claim 11, wherem: the fifth layer is a he layer and comprises at least one member selected from the group consistmg of modified ethylene/ alpha-olefm copolymer, modified ethylene/ unsaturated ester copolymer, and modified ethylene/ unsaturated acid copolymer; and the sixth layer is a e layer and comprises at least one member selected from the group consistmg of modified ethylene/ alpha-olefm copolymer, modified ethylene/unsaturated ester copolymer, and modified ethylene/ unsaturated acid copolymer. 14. The backseamed casmg accordmg to claim 13, wherem: the second layer has a thickness of from about 5 to 20 percent, based on a total thickness of the multilayer film; and the fourth layer has a thickness of less than about 15%, based on a total thickness of the multilayer film. 15. The backseamed casmg accordmg to claim 13, wherem the hrst polyamide comprises at least one member selected from the group consistmg of polyamide 6, polyamide 66, polyamide 9, polyamide 10, polyamide 11, polyamide 12, polyamide 69, polyamide 610, polyamide 612, polyamide 61, polyamide 6T, and copolymers thereof. 16. The backseamed casmg accordmg to claim 15, wherem the first polyamide comprises at least one member selected from the group consistmg of polyamide 6, polyamide 66 and polyamide 6/66. 17. The backseamed casmg accordmg to claim 16, wherem the casmg film further comprises: a seventh layer, the seventh layer being between the first layer and the second layer, the seventh layer compnsmg a sixth polyolefin; and an eighth layer, the eighth layer bemg between the second layer and the third layer, the eighth layer compnsmg a seventh polyolefm. 18. The backseamed casing according to claim 17, wherem the heat-shrmkable casmg film has biaxial orientation. 19. The backseamed casmg accordmg to claim 17, wherein the casing film has a free shrmk, at 185°F, of at least 10% in at least one direction. 20. The backseamed casmg accordmg to claim 19, wherein at least a portion of the casmg film comprises a crosslmked polymer network. 21. The backseamed casmg accordmg to claim 1, wherem the backseam casmg is a lap- seal backseam casmg. 22. The backseamed casmg accordmg to claim 1, wherem the backseam casmg is a butt- seal backseam casmg compnsmg both the casmg film and a butt-seal tape him. 23. The backseamed casmg accordmg to claim 22, wherem the butt-seal tape film is heat-shrmkable. 24. A package compnsmg a cooked meat product withm a backseamed casmg compnsmg a casmg film, the cooked meat product bemg adhered to a meat-contact surface of the casmg film, wherem the casmg fdm compnses: (A) a hrst outer layer serving as an inside casmg layer and meat-contact layer, the first outer layer compnsmg a first polyolefin compnsmg at least one member selected from the group consistmg of. (l) ethylene/ unsaturated acid copolymer, propylene/ unsaturated acid copolymer, and butene/ unsaturated acid copolymer, wherem the unsaturated acid is present in an amount of at least 4 weight percent, based on the weight of the copolymer; and (n) anhydnde-contammg polyolefin compnsmg an anhydride-functionality, wherem the anhydride functionality is present m an amount of at least 1 weight percent, based on the weight of the anhydnde-contammg polyolefm; (B) a second layer compnsmg at least one member selected from the group consistmg of polyester and hrst polyamide; and (C) a third outer layer servmg as an outside casmg layer, the third layer compnsmg at least one member selected from the group consisting of a second polyolefin, polystyrene and second polyamide; and wherein the second layer is between the first layer and the third layer, and the second layer has a thickness of at least about 5% of a total thickness of the heat-shrmkable casmg film. 25. The package according to claim 24, wherem the meat product compnses at least one member selected from the group consistmg of poultry, ham, beef, lamb, fish, hver sausage, bologna and mortadeUa. 26. The package accordmg to claim 25, wherem the meat-contact surface of the first layer is corona treated, and the meat product compnses at least one member selected from the group consistmg of bver sausage, bologna and mortadeUa. 27. The package accordmg to claim 24, wherem an outside surface of the second layer is corona treated. 28. A backseamed casmg compnsmg a heat-shrmkable casing film compπsmg- (A) a first outer layer servmg as an mside casmg layer, the hrst outer layer comprising a first polyolefin, the first outer layer havmg a surface energy level of less than about 34 dynes/ cm; (B) a second layer compnsmg a first polyamide having a meltmg pomt of at least 300° F; (C) a third layer servmg as an outside casing layer, the third outer layer compnsmg at least one member selected from the group consisting of a second polyolefm, polystyrene and second polyamide; and wherein the second layer is between the first layer and the third layer, and the second layer has a thickness of at least about 5% of a total thickness of the heat-shrmkable casmg film.

Inventors: RAMESH RAM K, ROSINSKI MICHAEL J, RAMESH, RAM, K., ROSINSKI, MICHAEL, J.
Applicants: GRACE W R & CO, W.R. GRACE & CO.-CONN.
Application year: 1996
Main classification: B32B27
IPC codes: A22C13, B32B27, B65D75, B65D81