Abstract:
An oxygen scavenger film includes a layer including an oxygen scavenger, and a layer including a cyclic olefin copolymer. An oxygen scavenger film includes a layer including a blend of an oxygen scavenger, and a cyclic olefin copolymer. A method of triggering an oxygen scavenger film includes providing an oxygen scavenger film including a layer including an oxygen scavenger, and a layer including a cyclic olefin copolymer; and subjecting the oxygen scavenger film to a dosage of actinic radiation effective to trigger the oxygen scavenger. A method of triggering an oxygen scavenger film includes providing an oxygen scavenger film including a layer including a blend of an oxygen scavenger and a cyclic olefin copolymer; and subjecting the oxygen scavenger film to a dosage of actinic radiation effective to trigger the oxygen scavenger.

Description:
[0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/566211 filed Apr. 28, 2004, the contents of which are hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates to oxygen scavenging film with cyclic olefin copolymer.  
       BACKGROUND OF THE INVENTION  
       [0003]     It is known that many oxygen sensitive products, including food products such as meat and cheese, smoked and processed luncheon meats, as well as non-food products such as electronic components, pharmaceuticals, and medical products, deteriorate in the presence of oxygen. Both the color and the flavor of foods can be adversely affected. The oxidation of lipids within the food product can result in the development of rancidity. These products benefit from the use of oxygen scavengers in their packaging.  
         [0004]     One particular oxygen scavenger that has proved useful commercially is poly(ethylene/methyl acrylate/ cyclohexene methyl acrylate) (abbreviated as EMCM). Although EMCM containing oxygen scavenging films have excellent cold seal strength, an EMCM layer tends to delaminate from adjacent layers at temperatures of 100 to 150 °C. These temperatures are typical of those encountered during, or immediately after, heat sealing of the film to itself or another material. Delamination can occur in packaging applications where vertically formed and filled packages are loaded before the heat seals are able to cool substantially. Due to poor interlayer adhesion at these elevated temperatures, the films delaminate at the EMCM interface when seals are pulled before they are totally cooled.  
         [0005]     In packaging applications such as vertical form fill seal pouch packaging, where transverse heat seals are used, poor interlaminar bond strength will be manifested as a low hot tack value ( below 4 newtons/inch at 1 30° C.). The failure mode is typically one of delamination at the interface of the sealant layer and the EMCM layer, and/or the EMCM layer and the next adjacent (internal) layer.  
         [0006]     A target hot tack value, which will represent a value typically minimally acceptable for many packaging applications, is at least 4 newtons/inch at 130° C. Desirable values include from 4 to 10 newtons/inch, such as 4.5 to 9.5 newtons/inch, such as 5 to 9, and 5.5 to 8.5, and 6 to 8 newtons/inch at 130° C. Hot tack is measured in accordance with ASTM F 1921-98.  
         [0007]     In addition, EMCM containing oxygen scavenging films can sometimes exhibit undesirable organoleptic characteristics depending on the product being packaged in the film, conditions of packaging or storage, etc.  
         [0008]     It has now been found that cyclic olefin copolymers (COC) in a film structure having an oxygen scavenger such as EMCM offers a means for providing adequate interlaminar bond strength between the oxygen scavenger and adjacent layers, and good hot tack seals.  
         [0009]     It is believed that cyclic olefin copolymers (COC) in a film structure having an oxygen scavenger such as EMCM also offers a means for providing a functional barrier that can reduce adverse organoleptic qualities in the film.  
       SUMMARY OF THE INVENTION  
       [0010]     In a first aspect of the present invention, an oxygen scavenger film comprises a layer comprising an oxygen scavenger, and a layer comprising a cyclic olefin copolymer.  
         [0011]     In a second aspect of the present invention, an oxygen scavenger film comprises a layer comprising a blend of an oxygen scavenger and a cyclic olefin copolymer.  
         [0012]     In a third aspect of the present invention, a method of triggering an oxygen scavenger film comprises providing an oxygen scavenger film comprising a layer comprising an oxygen scavenger, and a layer comprising a cyclic olefin copolymer; and subjecting the oxygen scavenger film to a dosage of actinic radiation effective to trigger the oxygen scavenger.  
         [0013]     In a fourth aspect of the present invention, a method of triggering an oxygen scavenger film comprises providing an oxygen scavenger film comprising a layer comprising a blend of an oxygen scavenger and a cyclic olefin copolymer, and subjecting the oxygen scavenger film to a dosage of actinic radiation effective to trigger the oxygen scavenger.  
         [0000]     Definitions  
         [0014]     “Cyclic olefin copolymer” and the like herein means a composition such as ethylene/norbornene copolymer, such as that supplied by Ticona under the trademark TOPAS™.  
         [0015]     “Oxygen scavenger”, “oxygen scavenging”, and the like herein means or refers to a composition, compound, film, film layer, coating, plastisol, gasket, or the like which can consume, deplete or react with oxygen from a given environment.  
         [0016]     “Ethylene/alpha-olefin copolymer” (EAO) herein refers to copolymers of ethylene with one or more comonomers selected from C 3  to C 10  alpha-olefins such as propene, butene-1, hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long polymer chains with relatively few side chain branches arising from the alpha-olefin which was reacted with ethylene. This molecular structure is to be contrasted with conventional high pressure low or medium density polyethylenes which are highly branched with respect to EAOs and which high pressure polyethylenes contain both long chain and short chain branches. EAO includes such heterogeneous materials as linear medium density polyethylene (LMDPE), linear low density polyethylene (LLDPE), and very low and ultra low density polyethylene (VLDPE and ULDPE), such as DOWLEX™ or ATTANE™ resins supplied by Dow, and ESCORENE™ or EXCEED™ resins supplied by Exxon; as well as linear homogeneous ethylene/alpha olefin copolymers (HEAO) such as TAFMER™ resins supplied by Mitsui Petrochemical Corporation, EXACT™ resins supplied by Exxon, or long chain branched (HEAO) AFFINITY™ resins supplied by the Dow Chemical Company, or ENGAGE™ resins supplied by DuPont Dow Elastomers.  
         [0017]     “Ethylene homopolymer or copolymer” herein refers to ethylene homopolymer such as low density polyethylene; ethylene/alpha olefin copolymer such as those defined herein; ethylene/vinyl acetate copolymer, ethylene/alkyl acrylate copolymer, ethylene/(meth)acrylic acid copolymer; or ionomer resin.  
         [0018]     “Film” herein means a film, laminate, sheet, web, coating, or the like, which can be used to package an oxygen sensitive product. The film can be used as a component in a rigid, semi-rigid, or flexible product, and can be adhered to a non-polymeric or non-thermoplastic substrate such as paper or metal. The film can also be used as a coupon or insert within a package.  
         [0019]     “Functional barrier” herein means a polymeric material which acts as a selective barrier to by-products from the oxygen scavenging reaction, but is not itself a significant barrier to oxygen.  
         [0020]     “Polymer” and the like herein means a homopolymer, but also copolymers thereof, including bispolymers, terpolymers, etc.  
         [0021]     “Trigger” and the like herein means that process defined in U.S. Pat. No. 5,211,875, whereby oxygen scavenging is initiated (i.e. activated) by subjecting an article such as a film to actinic radiation, having a wavelength of less than about 750 nm at an intensity of at least about 1.6 mW/cm 2  or ionizing radiation such as an electron beam at a dose of at least 0.2 megarads (MR), or gamma radiation, wherein after initiation the oxygen scavenging rate of the article is at least about 0.05 cc oxygen per day per gram of oxidizable organic compound for at least two days after oxygen scavenging is initiated. A method offering a short “induction period” (the time that elapses, after exposing the oxygen scavenging component to a source of actinic radiation, before the oxygen scavenging activity begins) is useful in situations where the oxygen scavenging component is desirably activated at or immediately prior to use. Triggering can thus occur during filling and sealing of a container, which is made wholly or partly from the article, and containing an oxygen sensitive material.  
         [0022]     Thus, “trigger” refers to subjecting an article to actinic radiation as described above; “triggered” refers to an article that has been subjected to such actinic radiation; “initiation” refers to the point in time at which oxygen scavenging actually begins or is activated; and “induction time” refers to the length of time, if any, between triggering and initiation. The onset of oxygen scavenging can be measured by any convenient means such as a reduction in headspace oxygen concentration, or an increase in barrier property as in the case of an active oxygen barrier system. One useful technology is the use of certain porphyrins as an oxygen indicator in a solid article such as a film, as disclosed in U.S. Pat. No.______, incorporated herein by reference in its entirety.  
         [0023]     All compositional percentages used herein are presented on a “by weight” basis, unless designated otherwise. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     An oxygen scavenger film of the invention can include multiple layers, dependent upon the properties required of the film. For example, layers to achieve appropriate slip, modulus, oxygen or water vapor barrier, meat adhesion, heat seal, or other chemical or physical properties can optionally be included. The film may be manufactured by a variety of processes including, extrusion, coextrusion, lamination, coating, and the like.  
         [0025]     An outer layer of the film, such as a layer that will function as a sealant layer of the film, can comprise one or more polymers. Polymers that may be used for the surface layer include any resin typically used to formulate packaging films with heat seal properties such as various polyolefin copolymers including ethylene polymer or copolymer, ethylene/alpha olefin copolymer, ethylene/vinyl acetate copolymer, ionomer resin, ethylene/ acrylic or methacrylic acid copolymer, ethylene/ acrylate or methacrylate copolymer, low density polythylene, or blends of any of these materials.  
         [0026]     Additional materials that can be incorporated into an outer layer of the film include antiblock agents, slip agents, etc.  
         [0027]     Oxygen Barrier Film  
         [0028]     High oxygen barrier films can be made from materials having an oxygen permeability, of the barrier material, less than 500 cm 3 O 2 /m 2  ·day ·atmosphere (tested at 1 mil thick and at 25° C. according to ASTM D3985), such as less than 100, more preferably less than 50 and most preferably less than 25 cm 3 O 2 /m 2 ·day·atmosphere such as less than 10, less than 5, and less than 1 cm 3 O 2 /m 2 ·day·atmosphere. Examples of polymeric materials with low oxygen transmission rates are ethylene/vinyl alcohol copolymer (EVOH), polyvinylidene dichloride (PVDC), vinylidene chloride/ methyl acrylate copolymer, polyamide, and polyester.  
         [0029]     Altematively, metal foil or SiOx compounds can be used to provide low oxygen transmission to the container. Metalized foils can include a sputter coating or other application of a metal layer to a polymeric substrate such as high density polyethylene (HDPE), ethylene/vinyl alcohol copolymer (EVOH), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyamide (PA).  
         [0030]     Altematively, oxide coated webs (e.g. aluminum oxide or silicon oxide) can be used to provide low oxygen transmission to the container. Oxide coated foils can include a coating or other application of the oxide, such as alumina or silica, to a polymeric substrate such as high density polyethylene (HDPE), ethylene/vinyl alcohol copolymer (EVOH), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyamide (PA).  
         [0031]     Multilayer films of the invention can be made using conventional extrusion, coextrusion, and/or lamination processes. Likewise, conventional manufacturing processes can be used to make a pouch, a bag, or other container from the film.  
         [0032]     Hermetic sealing of a pouch, bag, or other container made from the film of the invention will typically be preferable.  
         [0033]     The exact requirements of a container made from the film will depend on a variety of factors, including the chemical nature of the oxygen scavenger, amount of the oxygen scavenger, concentration of the oxygen scavenger in a host material or diluent, physical configuration of the oxygen scavenger, presence of hermetic sealing, vacuumization and/or modified atmosphere inside the container, initial oxygen concentration inside the container, intended end use of the oxygen scavenger, intended storage time of the container before use, level of initial dose of actinic radiation, etc.  
         [0034]     Polymeric adhesives that can be used in embodiments of the present invention include e.g. ethylene/vinyl acetate copolymer; anhydride grafted ethylene/vinyl acetate copolymer; anhydride grafted ethylene/alpha olefin copolymer; anhydride grafted polypropylene; anhydride grafted low density polyethylene; ethylene/ methyl acrylate copolymer; and anhydride grafted ethylene/ methyl acrylate copolymer.  
         [0035]     The Oxygen Scavenger  
         [0036]     Oxygen scavengers suitable for commercial use in articles of the present invention, such as films, are disclosed in U.S. Pat. No. 5,350,622, and a method of initiating oxygen scavenging generally is disclosed in U.S. Pat. No 5,211,875. Suitable equipment for initiating oxygen scavenging is disclosed in U.S. Pat. No. 6,287,481 (Luthra et al.). These patents are incorporated herein by reference in their entirety. According to U.S. Pat. No. 5,350,622, oxygen scavengers are made of an ethylenically unsaturated hydrocarbon and transition metal catalyst. The ethylenically unsaturated hydrocarbon may be either substituted or unsubstituted. As defined herein, an unsubstituted ethylenically unsaturated hydrocarbon is any compound that possesses at least one aliphatic carbon-carbon double bond and comprises 100% by weight carbon and hydrogen. A substituted ethylenically unsaturated hydrocarbon is defined herein as an ethylenically unsaturated hydrocarbon which possesses at least one aliphatic carbon-carbon double bond and comprises about 50%-99% by weight carbon and hydrogen. Suitable substituted or unsubstituted ethylenically unsaturated hydrocarbons are those having two or more ethylenically unsaturated groups per molecule, e.g. a polymeric compound having three or more ethylenically unsaturated groups and a molecular weight equal to or greater than 1,000 weight average molecular weight.  
         [0037]     Examples of unsubstituted ethylenically unsaturated hydrocarbons include, but are not limited to, diene polymers such as polyisoprene, (e.g., trans-polyisoprene) and copolymers thereof, cis and trans 1,4-polybutadiene, 1,2-polybutadienes, (which are defined as those polybutadienes possessing greater than or equal to 50% 1,2 microstructure), and copolymers thereof, such as styrene/butadiene copolymer and styrene/isoprene copolymer. Such hydrocarbons also include polymeric compounds such as polypentenamer, polyoctenamer, and other polymers prepared by cyclic olefin metathesis; diene oligomers such as squalene; and polymers or copolymers with unsaturation derived from dicyclopentadiene, norbomadiene, 5-ethylidene-2-norbomene, 5-vinyl-2-norbomene, 4-vinylcyclohexene, 1,7-octadiene, or other monomers containing more than one carbon-carbon double bond (conjugated or non-conjugated).  
         [0038]     Examples of substituted ethylenically unsaturated hydrocarbons include, but are not limited to, those with oxygen-containing moieties, such as esters, carboxylic acids, aldehydes, ethers, ketones, alcohols, peroxides, and/or hydroperoxides. Specific examples of such hydrocarbons include, but are not limited to, condensation polymers such as polyesters derived from monomers containing carbon-carbon double bonds, and unsaturated fatty acids such as oleic, ricinoleic, dehydrated ricinoleic, and linoleic acids and derivatives thereof, e.g. esters. Specific examples also include esters or polyesters of functionalized unsaturated hydrocarbons such as hydroxy terminated polybutadiene. Such hydrocarbons also include polymers or copolymers derived from (meth)allyl (meth)acrylates. Suitable oxygen scavenging polymers can be made by trans-esterification. Such polymers are disclosed in U.S. Pat. No.5,859,145 (Ching et al.) (Chevron Research and Technology Company), incorporated herein by reference as if set forth in full. The composition used may also comprise a mixture of two or more of the substituted or unsubstituted ethylenically unsaturated hydrocarbons described above. While a weight average molecular weight of 1,000 or more is beneficial, an ethylenically unsaturated hydrocarbon having a lower molecular weight is also usable, especially if it is blended with a film-forming polymer or blend of polymers.  
         [0039]     An additional example of oxygen scavengers which can be used in connection with this invention are disclosed in PCT patent publication WO 99/48963 (Chevron Chemical et al.), incorporated herein by reference in its entirety. These oxygen scavengers include a polymer or oligomer having at least one cyclohexene group or functionality. These oxygen scavengers include a polymer having a polymeric backbone, cyclic olefinic pendent group, and linking group linking the olefinic pendent group to the polymeric backbone.  
         [0040]     An oxygen scavenging composition suitable for use with the invention comprises: 
    (a) a polymer or lower molecular weight material containing substituted cyclohexene functionality according to the following diagram:  
                         
 
 where A may be hydrogen or methyl and either one or two of the B groups is a heteroatom-containing linkage which attaches the cyclohexene ring to the said material, and wherein the remaining B groups are hydrogen or methyl; 
    (b) a transition metal catalyst; and     (c) a photoinitiator.    
 
         [0044]     The compositions may be polymeric in nature or they may be lower molecular weight materials. In either case, they may be blended with further polymers or other additives. In the case of low molecular weight materials, they will most likely be compounded with a carrier resin before use.  
         [0045]     Also suitable for use in the present invention is the oxygen scavenger of U.S. Pat. No. 6,255,248 (Bansleben et al.), incorporated herein by reference in its entirety, which discloses a copolymer of ethylene and a strained, cyclic alkylene, preferably cyclopentene; and a transition metal catalyst.  
         [0046]     Another oxygen scavenger which can be used in connection with this invention is the oxygen scavenger of U.S. Pat. No. 6,214,254 (Gauthier et al.), incorporated herein by reference in its entirety, which discloses ethylene/vinyl aralkyl copolymer and a transition metal catalyst.  
         [0047]     Transition Metal Catalysts  
         [0048]     As indicated above, the ethylenically unsaturated hydrocarbon is combined with a transition metal catalyst. Suitable metal catalysts are those that can readily interconvert between at least two oxidation states.  
         [0049]     The catalyst can be in the form of a transition metal salt, with the metal selected from the first, second or third transition series of the Periodic Table. Suitable metals include, but are not limited to, manganese II or III, iron II or III, cobalt II or III, nickel II or III, copper I or II, rhodium II, III or IV, and ruthenium II or III. The oxidation state of the metal when introduced is not necessarily that of the active form. Suitable counterions for the metal include, but are not limited to, chloride, acetate, stearate, palmitate, caprylate, linoleate, tallate, 2-ethylhexanoate, neodecanoate, oleate or naphthenate. Useful salts include cobalt (II) 2-ethylhexanoate, cobalt stearate, and cobalt (II) neodecanoate. The metal salt may also be an ionomer, in which case a polymeric counterion is employed. Such ionomers are well known in the art.  
         [0050]     Any of the above-mentioned oxygen scavengers and transition metal catalyst can be further combined with one or more polymeric diluents, such as thermoplastic polymers, which are typically used to form film layers in plastic packaging articles. In the manufacture of certain packaging articles well known thermosets can also be used as the polymeric diluent.  
         [0051]     Further additives can also be included in the composition to impart properties desired for the particular article being manufactured. Such additives include, but are not necessarily limited to, fillers, pigments, dyestuffs, antioxidants, stabilizers, processing aids, plasticizers, fire retardants,etc.  
         [0052]     The mixing of the components listed above can be accomplished by melt blending at a temperature in the range of 50° C. to 300° C. However, altematives such as the use of a solvent followed by evaporation may also be employed.  
         [0053]     Photoinitiators Some of the materials useful in connection with the invention include:  
         [0054]     1,3,5-tris(4-benzoylphenyl)benzene (BBP 3 )  
         [0055]     isopropylthioxanthone (ITX)  
         [0056]     bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (IRGACURE®819) 2,4,6-trimethylbenzoyldiphenylphosphine oxide  
         [0057]     ethyl-2,4,6-trimethylbenzoylphenyl phosphinate  
         [0058]     bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide  
         [0059]     4,4′-benzoylmethyl diphenyl sulfide (BMS)  
         [0060]     The amount of photoinitiator can depend on the amount and type of unsatu ration present in the polymer, the wavelength and intensity of radiation used; the nature and amount of antioxidants used; and the type of photoinitiator used.  
       EXAMPLES  
       [0061]     Several film structures in accordance with the invention are identified below. “COC” is a cyclic olefin copolymer; “OS” is an oxygen scavenger; “EAO” is ethylene/alpha olefin copolymer; “OB” is oxygen barrier; “PE” is ethylene homopolymer or copolymer, such as low density polyethylene or ethylene/alpha olefin copolymer; “ADH” is adhesive, such as polymeric adhesive; and “NYLON” is a polyamide or copolyamide.  
                                             Film Structure A.                COC   OS                       0.50   0.50                      
 
         [0062]     The total gauge of Film Structure A is 1.0 mil, with the thickness of each layer, in mils, as indicated above.  
                                             Film Structure B.            EAO   COC   OS               0.25   0.50   0.50                  
 
         [0063]     The total gauge of Film Structure B is 1.25 mils, with the thickness of each layer, in mils, as indicated above.  
                                                     Film Structure C.                EAO   COC   OS   OB                       0.25   0.50   0.50   0.25                      
 
         [0064]     The total gauge of Film Structure C is 1.5 mils, with the thickness of each layer, in mils, as indicated above.  
                                                     Film Structure D.            EAO   COC   OS   OB   PE               0.25   0.50   0.50   0.25   0.25                  
 
         [0065]     The total gauge of Film Structure D is 1.75 mils, with the thickness of each layer, in mils, as indicated above.  
                                                             Film Structure E.            EAO   COC   OS   OB   ADH   PE   PET               0.25   0.50   0.50   0.25   0.20   0.25   0.50                  
 
         [0066]     The total gauge of Film Structure E is 2.45 mils, with the thickness of each layer, in mils, as indicated above. A film comprising PET (poly(ethylene terephthalate) is shown adhered by lamination, such as adhesive lamination, or any other suitable means to the PE layer of the film.  
                                                                         Film Structure F.                            NY-       NY-                   EAO   COC   OS   ADH   LON   OB1   LON   ADH   PE   PET               0.25   0.50   0.50   0.20   0.20   0.25   0.20   0.20   0.25   0.50                  
 
         [0067]     The total gauge of Film Structure F is 3.05 mils, with the thickness of each layer, in mils, as indicated above.  
         [0068]     The COC can be blended with the oxygen scavenger layer instead of, or in addition to, being present in a layer separate from the oxygen scavenger layer.  
         [0069]     The COC can be blended with the sealant (EAO) layer instead of, or in addition to, being present in a layer separate from the sealant layer.  
         [0070]     The COC layer can be used “neat”, i.e. without the addition of significant amounts of other materials in the same layer, or can be blended with a polyolefin such as ethylene homopolmer or copolymer. When EMCM or other oxygen scavengers are used to scavenge oxygen from the headspace of a package or container, it is sometimes important that the COC layer have a sufficient high oxygen permeability (oxygen transmission rate) to allow the oxygen from the headspace to move through the film structure to the oxygen scavenger layer at a sufficient rate to effect the oxygen scavenging functionality of the film. With increasing thickness of the COC layer, the presence of increasing amounts of blended polyolefin will aid in controlling the overall oxygen transmission rate of the COC layer.  
         [0071]     The sealant layer can comprise, instead of EAO, a propylene polymer or copolymer, such as ethyene/propylene copolymer, or an ethylene homopolymer or copolymer, such as low density polyethylene or ethylene/vinyl acetate copolymer, or ethylene/acrylic or methacrylic acid copolymer, or ionomer.  
         [0072]     Additional materials, including polymeric materials or other organic or inorganic additives, can be added to any or all of the layers of the above structures as needed, and additional film layers can be included either within the film structure, or adhered to an outer layer thereof.  
         [0073]     Film as described herein can be produced by any suitable method, including coextrusion, extrusion coating, lamination, extrusion lamination, etc.  
         [0074]     The sealant side of the PE layer of structures E and F, i.e. that side of the layer that will adhere to the PET film, can altematively be adhered to another polymer, to paperboard, or to foil such as metal foil.  
         [0075]     Films useful in connection with the invention can have any suitable number of layers, such as a total of from 2 to 20 layers.  
         [0076]     In general, the film can have any total thickness desired, and each layer can have any thickness desired, so long as the film provides the desired properties for the particular packaging operation in which the film is used. Typical total thicknesses are from 0.5 mils to 15 mils, such as 1 mil to 12 mils, such as 2 mils to 10 mils, 3 mils to 8 mils, and 4 mils to 6 mils.  
         [0077]     In the above film structures, the interface between the oxygen barrier layer and the oxygen scavenger layer will typically include an adhesive or tie layer, such as one of the polyermic adhesives described herein.  
         [0078]     The invention is not limited to the illustrations described herein, which are deemed to be merely illustrative, and susceptible of modification of form, size, arrangement of parts and details of operation.  
         [0079]     The following film structures in accordance with the invention were made by a conventional coextrusion process.  
         [0080]     Materials used were as follows.  
       Resin Identification  
       [0081]    
       
         
               
               
               
             
           
               
                   
               
               
                   
               
               
                 Material 
                 Tradename Or 
                   
               
               
                 Code 
                 Designation 
                 Source(s) 
               
               
                   
               
             
             
               
                   
                 PE4517 
                 Chevron 
               
               
                 AB 
                 10853 
                 Ampacet 
               
               
                 mPE 
                 metallocene catalyzed ethylene/ 
                 Dow 
               
               
                   
                 alpha olefin copolymer 
               
               
                 COC1 
                 TOPAS ™ 9506X1 
                 Ticona 
               
               
                 COC2 
                 TOPAS ™ 6013 
                 Ticona 
               
               
                 COC3 
                 TOPAS ™ 8007 
                 Ticona 
               
               
                 EVA 
                 ESCORENE ™ LD-318.92 
                 ExxonMobil 
               
               
                 EVA2 
                 EVA blend (see below) 
               
               
                 EVA tie 
                 Ethylene/vinyl acetate copolymer 
               
               
                 OS1 
                 OSP500R ™ or DS4713R ™ 
                 Chevron Phillips 
               
               
                 OSM1 
                 OSP100M 
                 Chevron Phillips 
               
               
                 PP 
                 polypropylene 
               
               
                   
               
             
          
         
       
     
         [0082]     AB is a masterbatch having about 80% linear low density polyethylene, and about 20% of an antiblocking agent (diatomaceous earth).  
         [0083]     COC1 is an ethylene/norbomene copolymer.  
         [0084]     COC2 is an ethylene/norbomene copolymer.  
         [0085]     COC3 is an ethylene/norbomene copolymer.  
         [0086]     OS1 is an oxygen scavenger resin, poly(ethylene/methyl acrylate/ cyclohexene methyl acrylate) (abbreviated as EMCM).  
         [0087]     EVA is ethylene/vinyl acetate copolymer with 9 weight % vinyl acetate comonomer.  
         [0088]     EVA2 is blend of 70% ethylene/vinyl acetate copolymer, 10% EVA processing aid, and 20% zeolite.  
         [0089]     OSM1 is a masterbatch produced from a carrier resin (ethylene/methyl acrylate), with 1%, by weight of the masterbatch, of cobalt present in a prill (solid) cobalt oleate, and 1%, by weight of the masterbatch, of tribenzoyl triphenyl benzene (1 ,3,5-tris(4-benzoylphenyl)benzene).  
         [0090]     PE 4517 is a low density polyethylene resin.  
         [0091]     All compositional percentages given herein are by weight, unless indicated otherwise.  
         [0092]     Hot tack values are reported in Newtons/inch at 130° C., per ASTM F 1921-98.  
                                                                                                                                 Layer   Total               Layer 1   Layer 2   Layer 3   Layer 4   5   Gauge   Hot Tack                                    Control   EAO   EAO   EVA tie   PP homo                           #1   0.25   0.75   0.2   0.75       1.95   mils   6.2   N/in       Control   EAO   90% OS1 &amp;   EVA tie   PP               3.0   N/in       #2       10% OSM1           0.25   0.75   0.2   0.75       1   mPE   EMCM   EVA tie   EMCM   PP           4.3   N/in           0.25   0.75   0.5   0.75   0.75   3.00       2   mPE   90% EMCM &amp;   EVA tie   90% EMCM &amp;   PP           4.4   N/in               10% OSM1       10% OSM1           0.25   0.75   0.5   0.75   0.75   3.00       3   80% mPE &amp;   90% EMCM &amp;   EVA tie   90% EMCM &amp;   PP           4.3   N/in           15% COC1 &amp;   10% OSM1       10% OSM1            5% AB/slip           0.25   0.75   0.5   0.75   0.75   3.00       4   80% mPE &amp;   EMCM   EVA tie   EMCM   PP           4.1   N/in           15% COC1 &amp;            5% AB/slip           0.25   0.75   0.5   0.75   0.75   3.00       5   80% mPE &amp;   80% EMCM &amp;   EVA tie   80% EMCM &amp;   PP           5.2   N/in            5% COC1 &amp;   10% OSM1 &amp;       10% OSM1 &amp;            5% AB/slip   10% COC1       10% COC1           0.25   0.75   0.5   0.75   0.75   3.00       6   80% mPE &amp;   90% EMCM &amp;   EVA tie   90% EMCM &amp;   PP           4.6   N/in           15% COC1 &amp;   10% COC1       10% COC1            5% AB/slip           0.25   0.75   0.5   0.75   0.75   3.00       7   80% mPE &amp;   90% EMCM &amp;   EVA tie   90% EMCM &amp;   PP           4.3   N/in           15% COC1 &amp;   10% COC2       10% COC2            5% AB/slip           0.25   0.75   0.5   0.75   0.75   3.00       8   mPE   90% EMCM &amp;   90% EMCM &amp;   90% EMCM &amp;   PP           3.1               10% OSM1   10% OSM1   10% OSM1           0.25   0.25   0.25   0.25   0.75   1.75       9   82% mPE &amp;   90% EMCM &amp;   90% EMCM &amp;   90% EMCM &amp;   PP           4           15% COC1 &amp;   10% OSM1   10% OSM1   10% OSM1            3% AB/slip           0.25   0.25   0.25   0.25   0.75   1.75       10   82% mPE &amp;   80% EMCM &amp;   80% EMCM &amp;   80% EMCM &amp;   PP           3.7           15% COC1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            3% AB/slip   10% COC1   10% COC1   10% COC1           0.25   0.25   0.25   0.25   0.75   1.75       11   82% mPE &amp;   80% EMCM &amp;   80% EMCM &amp;   80% EMCM &amp;   PP           4.6           15% COC1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            3% AB/slip   10% COC3   10% COC3   10% COC3           0.25   0.25   0.25   0.25   0.75   1.75       12   82% mPE &amp;   75% EMCM &amp;   75% EMCM &amp;   75% EMCM &amp;   PP           4.9           15% COC1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            3% AB/slip   15% COC3   15% COC3   15% COC3           0.25   0.25   0.25   0.25   0.75   1.75       13   82% mPE &amp;   75% EMCM &amp;   75% EMCM &amp;   75% EMCM &amp;   PP           6           15% COC3 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            3% AB/slip   15% COC3   15% COC3   15% COC3           0.25   0.25   0.25   0.25   0.75   1.75       14   82% mPE &amp;   75% EMCM &amp;   75% EMCM &amp;   75% EMCM &amp;   PP           4.7           15% COC3 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            3% AB/slip   15% PP   15% PP   15% PP           0.25   0.25   0.25   0.25   0.75   1.75       15   77% mPE &amp;   90% EMCM &amp;   90% EMCM &amp;   90% EMCM &amp;   PP           3.4           15% COC3 &amp;   10% OSM1   10% OSM1   10% OSM1            8% AB           0.25   0.25   0.25   0.25   0.75   1.75       16   77% mPE &amp;   80% EMCM &amp;   80% EMCM &amp;   80% EMCM &amp;   PP           3.9           15% COC3 &amp;   10% OSM1 &amp;   10% OSM1 &amp;   10% OSM1 &amp;            8% AB   10% COC1   10% COC1   10% COC1           0.25   0.25   0.25   0.25   0.75   1.75       17   92% PE4517 &amp;   COC1   90% OS1 &amp;   95% EVA &amp;   PET   1.62       4.3            8% AB       10% OSM1    5% EVA2           0.19   0.22   0.69   0.52           12%   12%   45%   30%       18   92% PE4517 &amp;   COC3   90% OS1&amp;   95% EVA &amp;   PET   1.57       4.9            8% AB       10% OSM1    5% EVA2           0.21   0.19   0.65   0.52           13%   13%   40%   33%