Abstract:
A breathable film involving at least one polymeric layer of 100% neutralized ionomer containing sufficient aliphatic, mono-functional organic acid salt to essentially triple the oxygen transmission value (OTV) and/or at least one polymeric layer of metallocene polyethylene (mPE) optional blended with low density polyethylene and preferably in combination with one or more outer layers of highly neutralized ionomer (e.g., Surlyn®). Such polymeric film and polymeric film structure has sufficient oxygen permeability, water vapor transmission, formability, and structural strength to be useful in wrapping food products requiring breathable films such as case ready meat, fish, sausage, fresh produce, and the like.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/373,798, filed Apr. 19, 2002; herein incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a polymeric film and polymeric film structure having sufficient oxygen permeability, water vapor transmission, formability, and structural strength to be useful in wrapping food products requiring breathable films such as case ready meat, fish, sausage, fresh produce, and the like. More specifically but not by way of limitation, the present invention relates to the incorporation of a polymeric film layer involving a blend of an ionomer and fatty acid salt, metallocene polyethylene (mPE), and combinations involving the same to improve oxygen transmission through the film. 
     2. Description of the Related Art 
     The fresh red meat industry is moving towards centralized processing and packaging. This trend cuts costs and improves food safety by reducing the number of steps that the meat is handled through the value chain. The pre-packaging of fresh red meat (known as Case Ready Meat) requires special packaging considerations. Several systems are under consideration. One system involves vacuum skin-packaging whole muscle cuts and placing the individual packages into a barrier “master pack”. The master pack prevents oxygen from spoiling the meat, allowing for longer distribution times associated with centralized packaging. Once the master packs reach the grocery store, personnel open the master pack and remove the individual packages. The color of fresh meat changes with concentration of oxygen. The meat is purple in the oxygen-starved environment of the master pack. Consumers prefer a bright red color that occurs with a high oxygen concentration. Thus, once the individual packages are removed from the master pack, the oxygen transmission into the package must be rapid to allow the meat to turn red quickly. 
     Partially neutralized ethylene/(meth)acrylic acid copolymers (e.g., Surlyn® ionomers) have superior forming properties for vacuum skin packaging, but the oxygen transmission rate through Surlyn® ionomers is too slow for this application. If the thickness of the Surlyn® film is reduced, the correct oxygen transmission rate can be achieved, but the physical properties are not good enough to ensure package integrity. Metallocene PE (especially grades with densities less than 0.91 g/cc) have high oxygen transmission rates but have poor formability and puncture resistance. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above-mentioned problems, it has now been discovered that a one hundred percent neutralized blend of a fatty acid and ethylene acid copolymer (i.e., a blend of a fatty acid salt and 100% neutralized ionomer) will exhibit an oxygen transmission rate (OTR) and moisture vapor transmission rate (MVTR) up to six times that of a corresponding film of highly neutralized ethylene acid copolymer (i.e., ionomer film). Such fatty acid ionomer film layers, optionally in combination with other highly permeable film layers such as metallocene polyethylene having a density of less than 0.91 g/cc, result in breathable film structures. Such a film layer when combined with one or more highly neutralized ionomer film layers results in film structure having sufficient oxygen permeability, water vapor transmission, formability, and structural strength to be useful in wrapping food products requiring breathable films such as case ready meat, fish, sausage, fresh produce, and the like. 
     Thus, the present invention provides a packaged food product comprising an article of food requiring an oxygen and/or moist atmosphere selected from the group consisting of case ready meat, fish, sausage and fresh produce enclosed in a multilayer polymer film, wherein at least one layer of the multilayer polymeric film consists essentially of a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein greater than 90% of all the acid moieties of (a) and of (b) are neutralized. 
     Preferably the aliphatic, mono-functional organic acid is selected from the group consisting of palmitic acid, stearic acid, oleic acid, and mixtures thereof and 100% of all acid moieties are nominally neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof. 
     The present invention further provides a packaged food product comprising an article of food requiring an oxygen and/or moist atmosphere selected from the group consisting of case ready meat, fish, sausage and fresh produce enclosed in a multilayer polymer film, wherein at least one layer of the multilayer polymeric film consists essentially of:
         (i) a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is a softening comonomer or ionomers of the E/X/Y copolymers wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all acid moieties of (a) and of (b) are nominally neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof;   (ii) a metallocene polyethylene having a density of less than 0.91 g/cc; or   (iii) a blend of a metallocene polyethylene having a density of less than 0.91 g/cc and a low density polyethylene,
 
and wherein at least one outer layer of the multilayer polymeric film consists essentially of an E/X/Y copolymer where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein from 15% to 80% of the acid moieties are neutralized.
       

     The invention also provides an oxygen permeable polymeric film consisting essentially of a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all the acid moieties of (a) and of (b) are nominally neutralized. Preferably the acids are neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof and the oxygen permeation rate of the permeable film normalized to one mil thickness is greater than 800 cc-mil/100 in 2 ·day atm. 
     One embodiment of the invention provides an oxygen- and moisture-permeable multilayer polymeric film comprising:
         (i) at least one polymeric layer consisting essentially of an E/X/Y copolymer where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein from 15% to 80% of the acid is neutralized;   (ii) at least one other polymeric layer consisting essentially of a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all acid moieties of (a) and of (b) are nominally neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof; and   (iii) at least one additional polymeric layer consisting essentially of a metallocene polyethylene having a density of less than 0.91 g/cc; or a blend of a metallocene polyethylene having a density of less than 0.91 g/cc and a low density polyethylene.       

     Another specific embodiment provides an oxygen- and moisture-permeable multilayer polymeric film comprising:
         (i) at least one polymeric layer consisting essentially of a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all acids of (a) and of (b) are nominally neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof; and   (ii) at least one additional polymeric layer consisting essentially of a metallocene polyethylene having a density of less than 0.91 g/cc; or a blend of a metallocene polyethylene having a density of less than 0.91 g/cc and a low density polyethylene.       

     Still another embodiment provides an oxygen and moisture permeable multilayer polymeric film comprising:
         (i) at least one polymeric layer consisting essentially of an E/X/Y copolymer where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein from 15% to 80% of the acid is neutralized; and   (ii) at least one other polymeric layer consisting essentially of a blend of (a) one or more aliphatic, mono-functional organic acids having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymers where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all acid moieties of (a) and of (b) are nominally neutralized to the corresponding salts of magnesium, sodium, zinc or mixtures thereof.       

     Most preferably this embodiment comprises three polymeric layers wherein both outer layers consist essentially of the E/X/Y copolymer of (i) and a middle layer consists essentially of the blend of E/X/Y copolymer and aliphatic, mono-functional organic acid 100% nominally neutralized of (ii). 
     And still another embodiment provides an oxygen and moisture permeable multilayer polymeric film comprising:
         (i) at least one polymeric layer consisting essentially of an E/X/Y copolymer where E is derived from ethylene, X is derived from C 3  to C 8  α,β ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein from 15% to 80% of the acid moieties are neutralized; and   (ii) at least one additional polymeric layer consisting essentially of a metallocene polyethylene having a density of less than 0.91 g/cc; or a blend of a metallocene polyethylene having a density of less than 0.91 g/cc and a low density polyethylene.       

     Most preferably this embodiment comprises three polymeric layers wherein both outer layers consist essentially of the E/X/Y copolymer of (t) and a middle layer consists essentially of the metallocene polyethylene or blend of metallocene polyethylene and low density polyethylene of (ii). 
     DETAILED DESCRIPTION OF THE INVENTION 
     In this disclosure, the term “copolymer” is used to refer to polymers containing two or more different monomers. The phrase “copolymer of various monomers” means a copolymer whose units are derived from the various monomers. “Consisting essentially of” means that the recited components are essential, while smaller amounts of other components may be present to the extent that they do not detract from the operability of the present invention. The term “(meth)acrylic acid” means methacrylic acid and/or acrylic acid. Likewise, the term “(meth)acrylate” means methacrylate and/or acrylate. 
     All references identified throughout this Specification including those in the Description of Related Art and those to which this case claims priority are incorporated by reference as if fully set forth herein. 
     Acid Copolymers 
     The acid copolymers used in the present invention to make the ionomers are preferably ‘direct’ acid copolymers. They are preferably alpha olefin, particularly ethylene, C 3-8  α,β-ethylenically unsaturated carboxylic acid, particularly acrylic and methacrylic acid, copolymers. They may optionally contain a third softening monomer. By “softening”, it is meant that the crystallinity is disrupted (the polymer is made less crystalline). Suitable “softening” comonomers are monomers selected from alkyl acrylate, and alkyl methacrylate, wherein the alkyl groups have from 1 to 8 carbon atoms. 
     The acid copolymers can be described as E/X/Y copolymers where E is ethylene, X is the α,β-ethylenically unsaturated carboxylic acid, and Y is a softening comonomer. X is preferably present in 3 to 30 (preferably 4 to 25, most preferably 5 to 20) wt. % of the polymer, and Y is present in 0 to 30 (preferably 0 to 25 or alternatively 0) wt. % of the polymer. 
     The ethylene acid copolymers with high levels of acid (X) are difficult to prepare in continuous polymerizers because of monomer-polymer phase separation. This difficulty can be avoided however by use of “co-solvent technology” as described in U.S. Pat. No. 5,028,674 or by employing somewhat higher pressures than those at which copolymers with lower acid levels can be prepared. 
     Specific acid copolymers include ethylene/(meth)acrylic acid copolymers. They also include ethylene/(meth)acrylic acid/n-butyl (meth)acrylate, ethylene/(meth)acrylic acid/iso-butyl (meth)acrylate, ethylene/(meth)acrylic acid/methyl (meth)acrylate, and ethylene/(meth)acrylic acid/ethyl (meth)acrylate terpolymers. 
     Ionomers 
     The unmodified, melt processible ionomers used in this invention are prepared from acid copolymers as described above. They include partially neutralized acid copolymers, particularly ethylene/(meth)acrylic acid copolymers. The unmodified ionomers may be neutralized to any level that does not result in an intractable (not melt processible) polymer without useful physical properties. Preferably, about 15 to about 80%, preferably about 50 to about 75% of the acid moieties of the acid copolymer are neutralized by an alkali metal or an alkaline earth cation. For acid copolymers having a high acid level (for example over 15 wt. %), the percent neutralization must be lower to retain melt processibility. 
     Cations useful in making the unmodified ionomers are lithium, sodium, potassium, magnesium, calcium or zinc, or combinations of such cations. 
     Ionomers can be neutralized to levels higher than 80%, particularly when blended with the organic acids as described in this invention. For the purposes of this invention, high levels of neutralization (over 80%) are provided by adding the stoichiometric amount of a cation source needed to neutralize the target amount of acid moieties in the acid copolymer and organic acid(s) in the blend (hereinafter referred to as Nominal % Neutralization or “nominally neutralized”). One skilled in the art will appreciate that in cases of very high levels of neutralization (over 90% and especially at or near 100%), it can be difficult to determine analytically whether all of the individual acid moieties in the blend are neutralized. Similarly, it can also be difficult to determine whether any individual acid moiety is not neutralized. However, sufficient cations are made available in the blend so that, in aggregate, the indicated level of neutralization is achieved. 
     Organic Acids and Salts 
     The organic acids employed in the present invention are aliphatic, mono-functional (saturated, unsaturated, or multi-unsaturated) organic acids, particularly those having fewer than 36 carbon atoms. Also salts of these organic acids may be employed. The salts may be any of a wide variety, particularly including the barium, lithium, sodium, zinc, potassium, strontium, magnesium or calcium salts of the organic acids. 
     While it may be useful for the organic acids (and salts) to have a low volatility when being melt-blended with acid copolymer or ionomer, volatility has been found to not be limiting when neutralizing the blend to high levels, particularly near to or at 100%. At 100% neutralization (i.e., all acid moieties in the copolymer and organic acid are nominally neutralized), volatility simply is no longer an issue. As such, organic acids with lower carbon content can be used. It is preferred, however, that the organic acid (or salt) be non-volatile and non-migratory. It is preferred that they are agents that effectively plasticize ionic arrays and/or remove ethylene crystallinity from ethylene, C 3-8  α,β-ethylenically unsaturated carboxylic acid copolymers or ionomers thereof. By non-volatile, it is meant that they do not volatilize at temperatures of melt blending of the agent with the acid copolymer. By non-migratory, it is meant that the agent does not bloom to the surface of the polymer under normal storage conditions (ambient temperatures). Particularly useful organic acids include C 4  to less than C 36  (say C 34 ), more particularly C 6  to C 26 , even more particularly C 6  to C 18 , and most particularly C 6  to C 12 , organic acids. Specific organic acids useful in the present invention include, but are not limited to, caproic acid, caprylic acid, capric acid, lauric acid, stearic acid, behenic acid, erucic acid, oleic acid, and linoleic acid. Most preferably the naturally derived organic fatty acids such as palmitic, stearic, oleic, and mixtures thereof can be conveniently employed. 
     Additional optional additives useful in the practice of the subject invention include acid copolymer wax (e.g., Allied wax AC143, which is believed to be an ethylene/16-18% acrylic acid copolymer with a number average molecular weight of 2,040) that assists in preventing reaction between the filler materials (e.g., ZnO) and the acid moieties in the ethylene copolymer. Other optional additives include TiO 2 , which is used as a whitening agent; optical brighteners; surfactants; processing aids; etc. 
     Of notes are optional antioxidant additives that are useful in modifying the organoleptic properties (e.g. reducing odor or taste) of the blends of fatty acid and ethylene copolymers used in this invention. Antioxidants are available under the trade name Irganox as from Ciba Geigy Inc. Tarrytown, N.Y. For example, phenolic antioxidants such as IRGANOX E201, CAS Number 10191-41-0) or its derivatives may be added to the blend. IRGANOX 1010 is another antioxidant suitable for use in this invention. Thus, this invention provides packaged food products and oxygen permeable polymeric films wherein the blends of (a) one or more aliphatic, mono-functional organic acid having fewer than 36 carbon atoms or salts thereof and (b) one or more E/X/Y copolymer where E is derived from ethylene, X is derived from C 3  to C 8  α,β-ethylenically unsaturated carboxylic acids, and Y is derived from a softening comonomer, or ionomers of the E/X/Y copolymers, wherein X is about 3 to 30 wt. % of the E/X/Y copolymer, and Y is 0 to about 30 wt. % of the E/X/Y copolymer and wherein 100% of all acid moieties of (a) and of (b) are neutralized to the corresponding salts of magnesium, sodium, zinc and mixtures thereof further comprise an antioxidant. 
     The melt-processible, highly-neutralized acid copolymer ionomer of the present invention can be produced by
         (a) Melt-blending ethylene α,β-ethylenically unsaturated C 3-8  carboxylic acid copolymer(s) or ionomer(s) thereof that are not neutralized to the level that they have become intractable (not melt-processible) with one or more aliphatic, mono-functional, saturated or unsaturated organic acids having less than 36 carbon atoms or salts of the organic acids, and concurrently or subsequently   (b) Adding a sufficient amount of a cation source to increase the level of neutralization of all the acid moieties (including those in the acid copolymer and in the organic acid) to greater than 90%, preferably near 100%, more preferably to 100%.       

     Preferably the aliphatic, mono-functional, saturated or unsaturated organic acids having less than 36 carbon atoms or salts of the organic acids are present in a range of about 5 to about 150 parts (alternatively, about 25 to about 80) parts per hundred (pph) by weight of the ethylene α,β-ethylenically unsaturated C 3-8  carboxylic acid copolymer(s) or ionomer(s) thereof. Most preferably the acid is oleic acid or stearic acid. 
     Neutralization of acid copolymers and organic acids in this manner (concurrently or subsequently) has been found to be the only way without the use of an inert diluent to neutralize the copolymer without loss of processibility or properties such as toughness and elongation to a level higher than that which would result in loss of melt processibility and properties for the ionomer alone. For example, an acid copolymer blended with organic acid(s) can be neutralized to over 90%, preferably to about 100% or to 100% nominal neutralization without losing melt processibility as can occur with acid copolymers neutralized to greater than 90%. In addition, neutralizing to about 100% or to 100% reduces the deposits of the organic acids on the mold vent observed upon molding mixtures with less than 100% neutralization. 
     The acid copolymer(s) or unmodified, melt-processible ionomer(s) can be melt-blended with the organic acid(s) or salt(s) in any manner known in the art. For example, a salt and pepper blend of the components can be made and the components can then be melt-blended in an extruder. 
     The still melt-processible, acid copolymer/organic-acid-or-salt blend can be neutralized or further neutralized by methods known in the art. For example, a Werner &amp; Pfleiderer twin-screw extruder can be used to neutralize the acid copolymer and the organic acid at the same time. 
     Depending on the acid level of the co- or ter-polymer, the level of organic acid that controls processibility can be determine based on the disclosures herein. The percent organic acid needs to be higher for higher acid levels in the backbone of the co- or ter-polymer to achieve similar melt indices. See for example the following table (Table A) comparing melt indices (M.I.) obtained for various acid levels in an E/AA/14-16% nBA terpolymer modified with stearic acid. Typically, less of a lower molecular weight organic acid is needed to have the same effect as a higher amount of a higher molecular weight organic acid. 
     Preferably, the process employs an ethylene α,β-ethylenically unsaturated carboxylic acid copolymer or a melt-processible ionomer thereof that is an E/X/Y copolymer or melt-processible ionomer of the E/X/Y copolymer where E is ethylene, X is derived from a C 3  to C 8  α, β-ethylenically unsaturated carboxylic acid, and Y is derived from a softening comonomer wherein X is about 4-25 wt. % of the E/X/Y copolymer and Y is about 0-25 wt. % of the E/X/Y copolymer. Of particular note are copolymers wherein Y is 0 wt. % of the copolymer. 
     
       
         
               
             
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE A 
               
             
             
               
                   
               
               
                 Comparing M.I. To Stearic Acid Level and % AA 
               
             
          
           
               
                   
                 M.I. of Base 
                 Stearic Acid Level 
               
             
          
           
               
                 Acid Level 
                 Resin 
                 20% 
                 30% 
                 35% 
                 40% 
                 45% 
               
               
                   
               
             
          
           
               
                 8.1% AA 
                 67.9 
                   
                   
                 1.8 
                 2 
                 6 
               
               
                 About 8.3% AA 
                 62.5 
                   
                   
                 1.08 
                 1.13 
                 2.25 
               
               
                 10.1% AA 
                 66.8 
                   
                   
                 0.62 
                 1.55 
                 2.22 
               
               
                 About 6.8% AA 
                 75 
                 1.25 
                 1.92 
                   
                 6.52 
               
               
                 About 4.9% AA 
                 86 
                 4.9 
                 9.7 
                   
                 23.2 
               
               
                   
               
             
          
         
       
     
     Three other resins with the compositions recited in Table B were reacted with stearic acid and magnesium hydroxide. However, in this case, enough magnesium hydroxide was added to neutralize up to 100% of the combined acid moieties available in the copolymer and the stearic acid modifier. Ionomer/organic acid blends nominally neutralized to 100%, runs 1c and 1d, are listed in Table B. In specifically naming the E/X/Y resins the softening comonomer (e.g., nBA below) is identified second as commonly practiced in the art. 
                                                                         TABLE B                   Magnesium Stearate Modified Magnesium Ionomers                        Organic   Nominal %   M.I.       Run   Resin       Acid   Neutraliza-   (g/10       No   Composition   Cation   (%)   tion   min)                    1a   E/23nBA/9.6MAA   Mg   Stearic(40)   90   5.2       1b   E/23nBA/9.6MAA   Mg   Stearic(40)   95   3.6       1c   E/15nBA/8.5AA   Mg   Stearic(40)   100   1.15       1d   E/16nBA/12AA   Mg   Stearic(40)   100   0.09                    
Metallocene Polyethylene
 
     The metallocene polyethylene (mPE) employed in the present invention can be any such polyethylene as generally known in the art provided the oxygen permeability and/or the water vapor permeability are sufficiently high to afford the requisite breathability necessary for the intended film and film structure applications of interest. More specifically, the metallocene polyethylene should have a density less than 0.91 g/cc at which densities the normalized oxygen transmission rate (OTR) at 23° C. and 50% relative humidity will be greater than about 800 cc-mil/100 in 2 ·day·atm. This mPE can optionally be blended with other low crystalline polyolefin or amorphous polyethylenes (such as low density polyethylene, LDPE; linear low density polyethylene, LLDPE; other mPE and the like) provided the blend retains significantly high permeability. 
     The oxygen permeability of a multilayer film is related to the thickness and permeability of each of the layers in the following manner: 
                     1     OPV   package       =         x   1       OPV   1       +       x   2       OPV   2       +             (   1   )               
where OPV package  is the permeability of the package normalized to 1 mil, OPV 1  is the permeability of layer  1 , OPV 2  the permeability of layer  1 , x 1  is the fraction of the film thickness that comprises layer  1 , and x 2  is the fraction of the film thickness that comprises layer  2 .
 
     By using formula (1), one can find combinations of highly permeable and less permeable materials that will achieve the desired permeability requirements of the application, while maintaining the strength and forming properties. 
     For example, a 2-layer film comprised of a standard ionomer and a metallocene polyethylene (mPE) with density 0.88 g/cc will have the oxygen permeability values indicated:
 
 OPV   Ionomer =350 cc-mil/100 in 2 -day
 
 OPV   mPE =2000 cc-mil/100 in 2 -day.
 
     Using formula (1), the permeability of two-layer films with different layer ratios can be determined. Example permeabilities are reported in Table C. 
     
       
         
               
               
               
             
               
               
               
             
           
               
                 TABLE C 
               
               
                   
               
               
                 X Ionomer   
                 X mPE   
                 OPV package   
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 0 
                 1 
                 2000 
               
               
                 0.2 
                 0.8 
                 1029 
               
               
                 0.4 
                 0.6 
                 693 
               
               
                 0.6 
                 0.4 
                 522 
               
               
                 0.8 
                 0.2 
                 419 
               
               
                 1 
                 0 
                 350 
               
               
                   
               
             
          
         
       
     
     Thus, it is possible to achieve a highly permeable multilayer film by combining a skin layer of a standard ionomer with a layer of mPE. For example, a two-layer film with an OPV of 800 cc-mil/100 in 2 -day can be prepared with a layer of ionomer 0.32 times the total thickness of the film and a layer of mPE 0.68 times the total thickness. A three-layer structure with the same OPV can be prepared using an inner layer of mPE 0.68 times the total thickness and two outer layers of ionomer, each 0.16 times the total thickness. 
     Furthermore, blends of highly neutralized ionomers and organic acids, as described herein, allow much more flexibility in designing a multilayer structure with the desired high permeability properties because they have three to six times the permeability of standard ionomers. 
     Film Manufacture 
     The actual making of the film, multi-layer film, and corresponding film structures according to the instant invention can generally be by any such method as practiced in the art. As such, the film and film structures can be typically cast, extruded, co-extruded and the like including orientation (either axially or biaxially) by various methodologies (e.g., blown film, bubble techniques, mechanical stretching or the like, or lamination). It should be appreciated that various additives as generally practiced in the art can be present in the respective film layers including the presence of tie layers and the like, provided their presence does not substantially alter the properties of the breathable film or film structure. Thus, it is contemplated that various additives such as antioxidants and thermal stabilizers, ultraviolet (UV) light stabilizers, pigments and dyes, fillers, anti-slip agents, plasticizers, other processing aids, and the like may be advantageously employed. 
     The following examples are presented to more fully demonstrate and further illustrate various aspects and features of the present invention. As such, the showings are intended to further illustrate the differences and advantages of the present invention but are not meant to be unduly limiting. 
    
    
     EXAMPLE 1 
     In order to illustrate the enhanced oxygen transmission rates associated with a film layer involving a highly neutralized blend of ionomer and fatty acid, two ten-mil thick cast films were prepared. The first film involved Ionomer 1, a terpolymer of ethylene, iso-butyl acrylate, and methacrylic acid (E/10 wt % iBA/10 wt % MAA) that was 67% neutralized to the zinc salt (commercially available from E. I. du Pont de Nemours and Company under the Surlyn® tradename). The second cast film was a blend of a terpolymer of ethylene, n-butyl acrylate, and acrylic acid (E/15 wt % nBA/8.3% AA) containing 24 wt % oleic acid with 100% of all acid functionality being neutralized to the corresponding magnesium salts. The oxygen permeation value (OPV) was measured for each cast film at 23° C. and 50% relative humidity. The resulting data expressed as a normalized oxygen permeation rate at one mil thickness are presented in Table 1 below. The results show that a film of a highly neutralized fatty acid ionomer blend has over three times the oxygen permeability value of the Ionomer 1 film. 
     
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 Ionomer 1 
                 414 cc-mil/100 in 2  · day · atm 
               
               
                 Blend of (E/15 wt % nBA/8.3% AA) 
               
               
                 copolymer with 24 wt % oleic acid 
                 1,336 cc-mil/100 in 2  · day · atm 
               
               
                 blend and 100% Mg neutralization 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 2 
     Thirteen 3-layer coextruded blown films were prepared on a blown film line using a 5 cm (2-inch) diameter Brampton die. Monolayer films (i.e., all three layers compositionally of the same material) as well as various 3-layer combinations of ionomer, fatty acid ionomer blends, metallocene polyethylene (mPE), and metallocene polyethylene/low density polyethylene blend were prepared using the following materials: 
     fatty acid ionomer blend A: (E/10% iBA10% MAA), 30% oleic acid, 6% magnesium hydroxide; 100% neutralized 
     fatty acid ionomer blend B: (E/10% iBA/10% MM), 34% stearic acid, 6% magnesium hydroxide; 100% neutralized 
     Ionomer 2: (E/10% MM); 54% neutralized with Na 
     Ionomer 3: (E/15% MM); 58% neutralized with Zn 
     Ionomer 4: (E/10% MAM/10% iBA); 73% neutralized with Zn, 
     Metallocene polyethylene (mPE 1): octene-mPE, 0.879 g/cc, 1.0 Ml (available from Dow Chemical Company) 
     Low-density polyethylene (LDPE 1): 0.923 g/cc, 4 Ml 
     The processing temperature for the 3-layer blown film line was 210° C. but adjusted when needed to achieve nominal 3-layer target thickness of outer layer=1.2 mil, middle layer=1.6 mil, and inner layer=1.2 mil. The respective 3-layer films were tested for tensile strength properties (both in the transverse, TD, and machine, MD, direction), secant modulus, haze, gloss, static puncture resistance, slow puncture resistance, heat seal strength, thermoformability, oxygen permeation value (OPV), and water vapor transmission rate (WVTR). The resulting data are presented in the following Tables 2 through 6 below. 
     
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Tensile Strength Properties 
               
             
          
           
               
                   
                 Secant 
                   
                   
                   
                 % E- 
               
               
                   
                 Modulus 
                   
                   
                 Tensile at 
                 longation at 
               
               
                   
                 (psi) 
                 Yield (psi) 
                 Tensile (psi) 
                 Break (psi) 
                 Break (psi) 
               
             
          
           
               
                   
                 mean 
                   
                 Mean 
                   
                 mean 
                   
                 mean 
                   
                 Mean 
                   
               
               
                 Composition 
                 Stdev 
                   
                 Stdev 
                   
                 Stdev 
                   
                 Stdev 
                   
                 Stdev 
               
               
                   
               
             
          
           
               
                 Ionomer 2/Ionomer 2/Ionomer 2 (MD) 
                 30275 
                 1206 
                 74 
                 28 
                 4484 
                 148 
                 4484 
                 148 
                 1063 
                 45 
               
               
                 Ionomer 2/Ionomer 2/Ionomer 2 (TD) 
                 31203 
                 1215 
                 1724 
                 19 
                 4317 
                 309 
                 4310 
                 319 
                 1103 
                 59 
               
               
                 Ionomer 3/Ionomer 3/Ionomer 3 (MD) 
                 56256 
                 2348 
                 2807 
                 34 
                 5264 
                 321 
                 5227 
                 348 
                 741 
                 44 
               
               
                 Ionomer 3/Ionomer 3/Ionomer 3 (TD) 
                 53550 
                 1006 
                 2769 
                 44 
                 4756 
                 853 
                 4747 
                 872 
                 695 
                 151 
               
               
                 Blend A/Blend A/Blend A (MD) 
                 21173 
                 1469 
                 1749 
                 34 
                 2914 
                 117 
                 2907 
                 129 
                 1156 
                 51 
               
               
                 Blend A/Blend A/Blend A (TD) 
                 14964 
                 5507 
                 1571 
                 97 
                 2562 
                 367 
                 2560 
                 370 
                 1214 
                 224 
               
               
                 Blend B/Blend B/Blend B (MD) 
                 35144 
                 1677 
                 2391 
                 36 
                 2680 
                 180 
                 2679 
                 159 
                 856 
                 137 
               
               
                 Blend B/Blend B/Blend B (TD) 
                 33349 
                 2371 
                 2346 
                 65 
                 2511 
                 130 
                 2502 
                 137 
                 865 
                 82 
               
               
                 Ionomer 3/Blend A/Ionomer 3 (MD) 
                 42666 
                 2492 
                 91 
                 51 
                 4106 
                 326 
                 4084 
                 317 
                 782 
                 66 
               
               
                 Ionomer 3/Blend A/Ionomer 3 (TD) 
                 37887 
                 2006 
                 2219 
                 45 
                 3912 
                 205 
                 3900 
                 217 
                 813 
                 50 
               
               
                 Ionomer 3/Blend B/Ionomer 3 (MD) 
                 50014 
                 2222 
                 2669 
                 86 
                 4523 
                 156 
                 4521 
                 156 
                 828 
                 16 
               
               
                 Ionomer 3/Blend B/Ionomer 3 (TD) 
                 48196 
                 1245 
                 2471 
                 73 
                 4155 
                 221 
                 4155 
                 221 
                 827 
                 45 
               
               
                 Ionomer 3/mPE 1/Ionomer 3 (MD) 
                 36675 
                 535 
                 1989 
                 66 
                 3657 
                 113 
                 3627 
                 107 
                 710 
                 44 
               
               
                 Ionomer 3/mPE 1/Ionomer 3 (TD) 
                 38479 
                 2782 
                 1987 
                 43 
                 3666 
                 340 
                 3661 
                 339 
                 725 
                 55 
               
               
                 Ionomer 3/(mPE 1/20% LDPE 1)Ionomer 
                 38643 
                 2501 
                 48 
                 20 
                 3608 
                 145 
                 3587 
                 126 
                 733 
                 27 
               
               
                 3 (MD) 
               
               
                 Ionomer 3/(mPE 1/20% LDPE 1)Ionomer 3 
                 35415 
                 2553 
                 1899 
                 74 
                 3728 
                 330 
                 3685 
                 344 
                 748 
                 60 
               
               
                 (TD) 
               
               
                 (mPE 1/20% LDPE 1)/Same/Same (MD) 
                 3977 
                 113 
                 57 
                 21 
                 2498 
                 322 
                 2498 
                 323 
                 1762 
                 94 
               
               
                 (double gauge due to blocking) (TD) 
                 3936 
                 121 
                 67 
                 12 
                 2166 
                 432 
                 2166 
                 432 
                 1718 
                 101 
               
               
                 Blend A/(mPE 1/20% LDPE 1)/Blend A (MD) 
                 13091 
                 536 
                 1321 
                 35 
                 2149 
                 273 
                 2141 
                 274 
                 1055 
                 154 
               
               
                 Blend A/(mPE 1/20% LDPE 1)/Blend A (TD) 
                 12044 
                 845 
                 1256 
                 142 
                 2336 
                 202 
                 2329 
                 210 
                 1207 
                 56 
               
               
                 Blend B/(mPE 1/20% LDPE 1)/Blend B (MD) 
                 29509 
                 767 
                 1808 
                 33 
                 2375 
                 112 
                 2375 
                 112 
                 1025 
                 44 
               
               
                 Blend B/(mPE 1/20% LDPE 1)/Blend B (TD) 
                 28551 
                 858 
                 1697 
                 41 
                 2325 
                 73 
                 2325 
                 73 
                 1081 
                 43 
               
               
                 Ionomer 4/Ionomer 4/Ionomer 4 (MD) 
                 19625 
                 850 
                 106 
                 26 
                 5037 
                 362 
                 5035 
                 362 
                 965 
                 43 
               
               
                 Ionomer 4/Ionomer 4/Ionomer 4 (TD) 
                 19029 
                 863 
                 1622 
                 32 
                 4636 
                 375 
                 4636 
                 375 
                 950 
                 61 
               
               
                 Ionomer 3/Ionomer 4/Ionomer 3 (MD) 
                 42074 
                 1093 
                 91 
                 54 
                 5001 
                 449 
                 4994 
                 456 
                 795 
                 72 
               
               
                 Ionomer 3/Ionomer 4/Ionomer 3 (TD) 
                   
                   
                 2266 
                 101 
                 4718 
                 285 
                 4683 
                 270 
                 788 
                 40 
               
               
                   
               
               
                 *ASTM D 822; Sample Width = 2.54 cm (1 inch), 5.1 cm (2 inch) Jaw Separation; X-head = 51 cm (20 inch)/minute. 
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
               
                   
               
               
                 Static Puncture Test 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 011007-1, State 1 
                 011007-2, State 2 
                 011207-4, State 3A 
                 011307-2, State 4A 
                 011107-2, State 5A 
                 011107-3, State 6A 
               
               
                   
                 Ionomer 2/Ionomer 2/ 
                 Ionomer 3/Ionomer 3/ 
                 Blend A/Blend A/ 
                 Blend B/Blend B/ 
                 Ionomer 3/Blend A/ 
                 Ionomer 3/Blend B/ 
               
               
                   
                 Ionomer 2 
                 Ionomer 3 
                 Blend A 
                 Blend B 
                 Ionomer 3 
                 Ionomer 3 
               
               
                   
               
               
                 Film Thick- 
                 3.75 
                 3.45 
                 4.95 
                 4.7 
                 4.15 
                 4.1 
               
               
                 ness (mils) 
               
               
                 200 g Force 
                 3.7 
                 29.1 
                 15.3 
                 118.3 
                 1800+ 
                 1800+ 
               
               
                 (seconds to 
                 6.3 
                 899.1 
                 15.3 
                 125.6 
                 1800+ 
                 1800+ 
               
               
                 penetrate) 
               
               
                   
                 0 
                 1800+ 
                 15.4 
                 66.7 
                 1800+ 
                 1800+ 
               
               
                   
                 0 
                 1800+ 
                 1 
                 290.2 
                 1800+ 
                 1800+ 
               
               
                   
                 15.2 
                 1800+ 
                 3.6 
                 815 
                 1800+ 
                 1800+ 
               
               
                 Average 
                 5.04 
                 1265.6 
                 10.1 
                 283.2 
                 1800+ 
                 1800+ 
               
               
                 Std Dev 
                 6.3 
                 794 
                 7.2 
                 309 
                 0 
                 0 
               
               
                 150 g Force 
               
               
                 (seconds to 
               
               
                 penetrate) 
               
               
                 Average 
               
               
                 Std Dev 
               
               
                 300 g Force 
                   
                   
                   
                   
                 1255.1 
                 1285.1 
               
               
                 (seconds to 
                   
                   
                   
                   
                 90.2 
                 1026.3 
               
               
                 penetrate) 
                   
                   
                   
                   
                 415.1 
                 90.7 
               
               
                   
                   
                   
                   
                   
                 370.8 
                 126.2 
               
               
                   
                   
                   
                   
                   
                 132.9 
                 169.9 
               
               
                 Average 
                   
                   
                   
                   
                 452.8 
                 539.6 
               
               
                 Std Dev 
                   
                   
                   
                   
                 470 
                 570 
               
               
                   
               
             
          
           
               
                   
                 011007-3, State 7 
                 011107-1, State 
                 011207-2, State 8A 
                 011207-3, State 
                 011307-1, State 
                 011207-1, State 
                 011107-4, State 
               
               
                   
                 Ionomer 3/ 
                 7A Ionomer 3/ 
                 (MPE 1/20% LDPE 
                 9A Blend A/ 
                 10A Blend B/ 
                 11A Ionomer 
                 12A Ionomer 3/ 
               
               
                   
                 MPE 1/ 
                 (MPE 1/20% LDPE 
                 1)/Same/Same 
                 (MPE 1-20% 
                 (MPE 1/20% 
                 4/Ionomer 
                 Ionomer 
               
               
                   
                 Ionomer 3 
                 1)/Ionomer 3 
                 double gauge 
                 LDPE 1)/Blend A 
                 LDPE 1)/Blend B 
                 4/Ionomer 4 
                 4/Ionomer 3 
               
               
                   
               
               
                 Film Thick- 
                 3.8 
                 4.55 
                 7.5 
                 4.35 
                 4.1 
                 3.7 
                 3.6 
               
               
                 ness (mils) 
               
               
                 200 g Force 
                 44.4 
                 1800+ 
                 54.6 
                 0 
                 9 
                 0.7 
                 1800+ 
               
               
                 (seconds to 
                 27.7 
                 1800+ 
                 28.7 
                 0 
                 252.6 
                 90.5 
                 1800+ 
               
               
                 penetrate) 
               
               
                   
                 57.2 
                 1800+ 
                 50.7 
                 0 
                 39.5 
                 248.4 
                 1800+ 
               
               
                   
                 94.5 
                 1800+ 
                 10.7 
                 0 
                 8.4 
                 11.8 
                 1800+ 
               
               
                   
                 167.3 
                 1800+ 
                 7 
                 0 
                 83.1 
                 0.5 
                 1800+ 
               
               
                 Average 
                 78.2 
                 1800+ 
                 30.3 
                 0 
                 78.5 
                 70.4 
                 1800+ 
               
               
                 Std Dev 
                 55.5 
                 0 
                 22 
                 0 
                 102 
                 106 
                 0 
               
               
                 150 g Force 
                   
                   
                   
                 4.4 
               
               
                 (seconds to 
                   
                   
                   
                 16.7 
               
               
                 penetrate) 
                   
                   
                   
                 8.1 
               
               
                   
                   
                   
                   
                 14.9 
               
               
                   
                   
                   
                   
                 8.6 
               
               
                 Average 
                   
                   
                   
                 10.5 
               
               
                 Std Dev 
                   
                   
                   
                 5 
               
               
                 300 g Force 
                   
                 309 
                   
                   
                   
                   
                 270.7 
               
               
                 (seconds to 
                   
                 70.6 
                   
                   
                   
                   
                 40.7 
               
               
                 penetrate) 
                   
                 123.4 
                   
                   
                   
                   
                 37.8 
               
               
                   
                   
                 59.9 
                   
                   
                   
                   
                 35.6 
               
               
                   
                   
                 115.6 
                   
                   
                   
                   
                 74.4 
               
               
                 Average 
                   
                 135.7 
                   
                   
                   
                   
                 91.8 
               
               
                 Std Dev 
                   
                 101 
                   
                   
                   
                   
                 101 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 4 
               
               
                   
               
             
             
               
                   
                   
                   
                   
                   
                 011107-2, State 
                 011107-3, State 
                 011107-3, State 
               
               
                   
                 011007-1, State 1 
                 011007-2, State 2 
                 011207-4, State 
                 011307-2, State 
                 5A Ionomer 3/ 
                 6A Ionomer 3/ 
                 7 Ionomer 3/ 
               
               
                   
                 Ionomer 2/Ionomer 
                 Ionomer 3/Ionomer 
                 3A Blend A/ 
                 4A Blend B/ 
                 Blend A/ 
                 Blend 
                 (mPE 
               
               
                   
                 2/Ionomer 2 
                 3/Ionomer 3 
                 Blend A/Blend A 
                 Blend B/Blend B 
                 Ionomer 3 
                 B/Ionomer 3 
                 1/Ionomer 3 
               
               
                   
               
               
                 Film Thickness 
                 3.66 
                 3.8 
                 4.78 
                 4.8 
                 4.52 
                 4.34 
                 3.84 
               
               
                 (mils) 
               
               
                 Slow Puncture 
                 4082 
                 4717 
                 3856 
                 3357 
                 5579 
                 4218 
                 5579 
               
               
                 resistance 
               
               
                 Instron Probe, 
                 4763 
                 6033 
                 3583 
                 5307 
                 4717 
                 5579 
                 4128 
               
               
                 sharp tip 
               
               
                 Max. Load 
                 4354 
                 9752 
                 3901 
                 3084 
                 5488 
                 4400 
                 3856 
               
               
                 (gms) 
                 4264 
                 5942 
                 4581 
                 4808 
                 5171 
                 6940 
                 6124 
               
               
                   
                 4309 
                 5625 
                 3946 
                 3084 
                 5579 
                 4264 
                 4082 
               
               
                 Average 
                 4355 
                 6414 
                 3973 
                 3928 
                 5307 
                 5080 
                 4754 
               
               
                 Std Dev 
                 250 
                 1937 
                 368 
                 1052 
                 370 
                 1181 
                 1026 
               
               
                 Comments: 
                 E/B 
                 E/B 
                 E/B 
                 E/B 
                 E/B 
                 E/B 
                 E/B 
               
               
                 E = elong. 
               
               
                 B = break, 
               
               
                 NB = no break 
               
               
                 Gloss @ 20 
                 72.5 
                 75 
                 54.6 
                 39.4 
                 45.3 
                 71.4 
                 73.4 
               
               
                 deg. 
                 74.5 
                 72.3 
                 49.3 
                 38.1 
                 39 
                 72.6 
                 69.2 
               
               
                   
                 77.6 
                 78 
                 52.1 
                 44.2 
                 38.5 
                 65.3 
                 66.1 
               
               
                 Average 
                 74.87 
                 75.1 
                 52 
                 40.57 
                 40.93 
                 69.77 
                 69.57 
               
               
                 Std Dev 
                 2.57 
                 2.85 
                 2.65 
                 3.21 
                 3.79 
                 3.91 
                 3.66 
               
               
                 Total Haze 
                 4.37 
                 4.25 
                 9.52 
                 15.6 
                 5.71 
                 7.12 
                 4.14 
               
               
                   
                 3.66 
                 4.21 
                 10.1 
                 15.4 
                 5.4 
                 6.64 
                 3.58 
               
               
                   
                 4.34 
                 4.09 
                 10.3 
                 15.4 
                 5.93 
                 6.38 
                 3.54 
               
               
                 Average 
                 4.12 
                 4.18 
                 9.97 
                 15.47 
                 5.68 
                 6.71 
                 3.75 
               
               
                 Std Dev 
                 0.4 
                 0.08 
                 0.41 
                 0.12 
                 0.27 
                 0.38 
                 0.34 
               
               
                 Internal Haze 
                 0.71 
                 0.98 
                 6.38 
                 26.8 
                 2.52 
                 3.04 
                 0.53 
               
               
                   
                 0.5 
                 1.91 
                 6.79 
                 23.6 
                 2.08 
                 3.18 
                 0.56 
               
               
                   
                 0.45 
                 1.36 
                 5.52 
                 21.3 
                 1.56 
                 3.69 
                 0.74 
               
               
                 Average 
                 0.55 
                 1.42 
                 6.23 
                 23.9 
                 2.05 
                 3.3 
                 0.61 
               
               
                 Std Dev 
                 0.14 
                 0.47 
                 0.65 
                 2.76 
                 0.48 
                 0.34 
                 0.11 
               
               
                   
               
             
          
           
               
                   
                 011107-1, State 
                 011207-2, State 
                   
                   
                 011207-1, State 11A 
                   
               
               
                   
                 7A Ionomer 3/ 
                 8A (MPE 1/20% 
                 011207-3, State 9A 
                 011307-1, State 10A 
                 Ionomer 4/ 
                 011107-4, State 12A 
               
               
                   
                 mPE 1/20% LDPE 
                 LDPE 1)/ 
                 Blend A/(MPE 1-20% 
                 Blend B/(MPE 1-20% 
                 Surlyn ® 9020/ 
                 Ionomer 3/Ionomer 
               
               
                   
                 1)/Ionomer 3 
                 Same/Same-double 
                 LDPE 1)/ Blend A 
                 LPDE 1)/Blend B 
                 Surlyn ® 9020 
                 4/Ionomer 3 
               
               
                   
               
               
                 Film Thickness 
                 4.22 
                 3.58 
                 4.38 
                 4.24 
                 3.88 
                 3.78 
               
               
                 (mils) 
               
               
                 Slow Puncture 
                 4354 
                 5352 
                 2948 
                 2268 
                 5216 
                 5443 
               
               
                 resistance 
               
               
                 Instron Probe, 
                 4536 
                 4854 
                 2948 
                 3765 
                 6214 
                 5488 
               
               
                 sharp tip 
               
               
                 Max. Load 
                 3992 
                 5080 
                 3583 
                 2449 
                 6668 
                 5126 
               
               
                 (gms) 
                 3992 
                 5262 
                 3493 
                 2177 
                 6260 
                 5171 
               
               
                   
                 3357 
                 4990 
                 3266 
                 2132 
                 4990 
                 6895 
               
               
                 Average 
                 4046 
                 5108 
                 3248 
                 2558 
                 5870 
                 5625 
               
               
                 Std Dev 
                 452 
                 202 
                 297 
                 685 
                 726 
                 728 
               
               
                 Comments: 
                 E/B 
                 E/NB 
                 E/B 
                 E/B 
                 E/B 
                 E/B 
               
               
                 E = elong. 
               
               
                 B = break, 
               
               
                 NB = no 
               
               
                 break 
               
               
                 Gloss @ 20 
                 71.4 
                 xxx 
                 60.6 
                 34.8 
                 45.2 
                 51.2 
               
               
                 deg. 
                 71.5 
                 xxx 
                 62.4 
                 34.9 
                 44.4 
                 49.2 
               
               
                   
                 71.2 
                 xxx 
                 56.9 
                 36.5 
                 42.1 
                 56.8 
               
               
                 Average 
                 71.37 
                 xxx 
                 59.97 
                 35.4 
                 43.9 
                 52.4 
               
               
                 Std Dev 
                 0.15 
                 xxx 
                 2.8 
                 0.95 
                 1.61 
                 3.94 
               
               
                 Total Haze 
                 4.83 
                 xxx 
                 10.3 
                 13.6 
                 5.29 
                 4.2 
               
               
                   
                 5.36 
                 xxx 
                 9.08 
                 13.1 
                 6.55 
                 4.53 
               
               
                   
                 5.07 
                 xxx 
                 9.78 
                 13.5 
                 4.83 
                 4.39 
               
               
                 Average 
                 5.09 
                 xxx 
                 9.72 
                 13.4 
                 5.56 
                 4.37 
               
               
                 Std Dev 
                 0.27 
                 xxx 
                 0.61 
                 0.26 
                 0.89 
                 0.17 
               
               
                 Internal Haze 
                 0.89 
                 xxx 
                 4.14 
                 28.2 
                 0.53 
                 0.62 
               
               
                   
                 1.39 
                 xxx 
                 4.78 
                 27.7 
                 1.13 
                 0.65 
               
               
                   
                 1.07 
                 xxx 
                 4.52 
                 19.9 
                 1.18 
                 0.55 
               
               
                 Average 
                 1.12 
                 xxx 
                 4.48 
                 25.27 
                 0.95 
                 0.61 
               
               
                 Std Dev 
                 0.25 
                 xxx 
                 0.32 
                 4.65 
                 0.37 
                 0.05 
               
               
                   
               
             
          
         
       
     
     
       
         
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 5 
               
             
             
               
                   
                   
               
               
                   
                 Heat Seal Data (max. force gm/in) 
               
             
          
           
               
                   
                 Ionomer 
                   
                   
                   
               
               
                 Seal 
                 2/Ionomer 
                 Blend A/Blend 
                 Blend B/Blend 
               
               
                 Temp 
                 2/Ionomer 2 
                 A/Blend A 
                 B/Blend B 
               
             
          
           
               
                 ° C. 
                 peel str. 
                 std. dev. 
                 peel str. 
                 std. dev. 
                 peel str. 
                 std. dev. 
               
               
                   
               
             
          
           
               
                 120 
                  32 
                 19 
                  155 
                 108 
                  135 
                 23 
               
               
                   
                 No Seal 
                   
                 Peel 
                   
                 Peel 
               
               
                 130 
                  221 
                 178 
                  234 
                 129 
                  441 
                 103 
               
               
                   
                 Peel 
                   
                 Peel 
                   
                 Peel 
               
               
                 140 
                  531 
                 311 
                  473 
                 90 
                 1202 
                 244 
               
               
                   
                 Peel 
                   
                 Peel 
                   
                 Peel 
               
               
                 150 
                  774 
                 354 
                  632 
                 95 
                  980 
                 185 
               
               
                   
                 Peel 
                   
                 Peel 
                   
                 Peel 
               
               
                 160 
                  907 
                 396 
                 1065 
                 161 
                 1778 
                 272 
               
             
          
           
               
                   
                 Peel 
                   
                 Peel 
                   
                 Peel, Peel/Tear 
               
             
          
           
               
                 170 
                 1456 
                 504 
                 1120 
                 220 
                 1892 
                 402 
               
             
          
           
               
                   
                 Peel, Peel/Tear 
                 Peel 
                   
                 Peel, Peel/Tear 
               
             
          
           
               
                 180 
                 1990 
                 692 
                 1448 
                 221 
                 2433 
                 597 
               
             
          
           
               
                   
                 Peel, 
                 Peel 
                   
                 Peel/Tear, 
               
               
                   
                 El/Peel/Tear 
                   
                   
                 El/Peel/Tear 
               
             
          
           
               
                 190 
                 2967 
                 119 
                 1989 
                 452 
                 2705 
                 418 
               
             
          
           
               
                   
                 Peel/El, 
                 Peel, Peel/Tear 
                 Peel/ 
                   
               
               
                   
                 El/Peel/Tear 
                   
                 Tear 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Thermoformability 
               
             
          
           
               
                   
                 Oven 
                   
                 Sheet 
                   
                   
                 Final TH 
                 Depth of 
               
               
                   
                 Temp 
                 Time in 
                 Temp 
                 Total 
                 Final 
                 as % of 
                 Cavity @ 
               
               
                 Composition 
                 (° F.) 
                 Oven (s) 
                 (° F.) 
                 TH (mils) 
                 TH (mils) 
                 Total TH 
                 Failure 
               
               
                   
               
               
                 Ionomer 2/Ionomer 2/Ionomer 2 
                 265 
                 25 
                 134 
                 3.39 
                 0.67 
                 20 
                 1.0″ 
               
               
                 Ionomer 3/Ionomer 3/Ionomer 3 
                 265 
                 25 
                 139 
                 3.48 
                 0.76 
                 22 
                 1.0″ 
               
               
                 Blend A/Blend A/Blend A 
                 265 
                 25 
                 139 
                 4.34 
                 1.29 
                 30 
                 1.4″ 
               
               
                 Blend B/Blend B/Blend B 
                 265 
                 25 
                 136 
                 4.65 
                 1.15 
                 25 
                 1.2″ 
               
               
                 Ionomer 3/Blend A/Ionomer 3 
                 265 
                 25 
                 139 
                 3.86 
                 0.82 
                 21 
                 1.2″ 
               
               
                 Ionomer 3/Blend B/Ionomer 3 
                 265 
                 25 
                 138 
                 3.71 
                 0.59 
                 16 
                 1.4″ 
               
               
                 Ionomer 3/MPE 1/Ionomer 3 
                 265 
                 25 
                 142 
                 3.4  
                 0.67 
                 20 
                 1.2″ 
               
               
                 Ionomer 3/(MPE 1/20% LDPE 1)Ionomer 3 
                 250 
                 25 
                 138 
                 3.84 
                 0.78 
                 20 
                 1.2″ 
               
               
                 Blend A/(MPE 1/20% LDPE 1)/Blend A 
                 265 
                 25 
                 137 
                 3.84 
                 1.03 
                 27 
                 1.2″ 
               
               
                 Blend B/(MPE 1/20% LDPE 1)/Blend B 
                 265 
                 25 
                 139 
                 3.98 
                 0.92 
                 23 
                 1.2″ 
               
               
                 Ionomer 4/Ionomer 4/Ionomer 4 
                 265 
                 25 
                 146 
                 3.53 
                 0.65 
                 18 
                 1.2″ 
               
               
                 Ionomer 3/Ionomer 4/Ionomer 3 
                 265 
                 25 
                 138 
                 3.52 
                 0.68 
                 19 
                 1.2″ 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 7 
               
               
                   
               
               
                 Permeability 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   
                   
                   
                   
                 Normalized 
               
               
                   
                   
                   
                   
                   
                 to 1 mil 
               
               
                   
                   
                 Time 
                 H 2 O 
                 H 2 O 
                 H 2 O 
               
               
                   
                 Thick 
                 Min- 
                 g/m 2 / 
                 g/100 in 2 / 
                 g-mil/ 
               
               
                 Composition 
                 mils 
                 utes 
                 Day 
                 Day 
                 100 in 2 /Day 
               
               
                   
               
               
                 Ionomer 3/Ionomer 
                 3.85 
                 177 
                 4.782 
                 0.30852 
                 1.19 
               
               
                 3/Ionomer 3 
               
               
                 Ionomer 3/Ionomer 
                 3.6 
                 328 
                 5.089 
                 0.32832 
                 1.18 
               
               
                 3/Ionomer 3 
               
               
                 Average 
                 3.725 
                 252.5 
                 4.9355 
                 0.31842 
                 1.19 
               
               
                 Blend A/Blend A/ 
                 4.95 
                 227 
                 23.671 
                 1.52716 
                 7.56 
               
               
                 Blend A 
               
               
                 Blend A/Blend A/ 
                 3.9 
                 253 
                 19.302 
                 1.24529 
                 4.86 
               
               
                 Blend A 
               
               
                 Average 
                 4.425 
                 240 
                 21.4865 
                 1.386225 
                 6.13 
               
               
                 Blend B/Blend B/ 
                 4.9 
                 177 
                 9.046 
                 0.58361 
                 2.86 
               
               
                 Blend B 
               
               
                   
                 4.5 
                 202 
                 9.396 
                 0.60619 
                 2.73 
               
               
                 Average 
                 4.7 
                 189.5 
                 9.221 
                 0.5949 
                 2.80 
               
               
                 Ionomer 3/(MPE 
                 3.6 
                 429 
                 6.865 
                 0.4429 
                 1.59 
               
               
                 1/20% LDPE 1) 
               
               
                 Ionomer 3 
               
               
                   
                 3.5 
                 455 
                 6.933 
                 0.44729 
                 1.57 
               
               
                 Average 
                 3.55 
                 442 
                 6.899 
                 0.445095 
                 1.58 
               
               
                 (MPE 1/20% LDPE 
                 7.4 
                 126 
                 6.961 
                 0.4491 
                 3.32 
               
               
                 1)/Same/Same 
               
               
                 (double gauge due 
                 7.05 
                 152 
                 7.631 
                 0.49232 
                 3.47 
               
               
                 to blocking) 
               
               
                 Average 
                 7.225 
                 139 
                 7.296 
                 0.47071 
                 3.40 
               
               
                   
               
               
                   
                   
                 Time 
                 OTR 
                 OTR 
                 OPV cc- 
               
               
                   
                 Thick 
                 Min- 
                 cc/m 2 / 
                 cc/100 in 2 / 
                 mil/100 in 2 / 
               
               
                 Composition 
                 mils 
                 utes 
                 Day 
                 Day 
                 Day · atm 
               
               
                   
               
               
                 Ionomer 3/Ionomer 
                 3.6 
                 535 
                 1659.42 
                 107.059 
                 385.41 
               
               
                 3/Ionomer 3 
               
               
                 Ionomer 3/Ionomer 
                 xxxx 
                 xxxx 
                 xxxxx 
                 xxxxx 
               
               
                 3/Ionomer 3 
               
               
                 Average 
                 3.6 
                 535 
                 1659.42 
                 107.059 
                 385.41 
               
               
                 Blend A/Blend A/ 
                 4.95 
                 504 
                 8046.7 
                 519.141 
                 2569.75 
               
               
                 Blend A 
               
               
                 Blend A/Blend A/ 
                 3.9 
                 478 
                 7749.53 
                 499.969 
                 1949.88 
               
               
                 Blend A 
               
               
                 Average 
                 4.425 
                 491 
                 7898.115 
                 509.555 
                 2254.78 
               
               
                 Blend B/Blend B/ 
                 4.9 
                 525 
                 3295.8 
                 212.632 
                 1041.90 
               
               
                 Blend B 
               
               
                   
                 4.5 
                 488 
                 3287.98 
                 212.127 
                 954.57 
               
               
                 Average 
                 4.7 
                 506.5 
                 3291.89 
                 212.3795 
                 998.18 
               
               
                 Ionomer 3/(MPE 
                 4.6 
                 939 
                 2058.8 
                 132.826 
                 611.00 
               
               
                 1/20% LDPE 1) 
               
               
                 Ionomer 3 
               
               
                   
                 4.5 
                 992 
                 2083.23 
                 134.402 
                 604.81 
               
               
                 Average 
                 4.55 
                 965.5 
                 2071.015 
                 133.614 
                 607.94 
               
               
                 (MPE 1/20% LDPE 
                 7.15 
                 923 
                 5934.81 
                 382.89 
                 2737.66 
               
               
                 1)/Same/Same 
               
               
                 (double gauge due 
                 7.3 
                 981 
                 5788.01 
                 373.419 
                 2725.96 
               
               
                 to blocking) 
               
               
                 Average 
                 7.225 
                 952 
                 5861.41 
                 378.1545 
                 2732.17 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 3 
     In a manner analogous to the previous examples a series of six additional films of 100% neutralized fatty acid ionomer at various fatty acid loading and respective cation were prepared and tested. The resulting data are presented in Tables 8 and 9. 
     
       
         
               
             
               
               
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Film Composition 
               
             
          
           
               
                   
                   
                   
                 Nominal % 
                 Conc Fatty 
               
               
                 Blend 
                 Acid Copolymer 
                 Cation 
                 Neutralization 
                 Acid 
               
               
                   
               
               
                 C 
                 E/10% i BA/10% 
                 Mg 
                 100 
                 31% Oleic 
               
               
                   
                 MAA 
               
               
                 D 
                 E/10% i BA/10% 
                 Mg 
                 100 
                 36 Oleic 
               
               
                   
                 MAA 
               
               
                 E 
                 E/15% MAA 
                 Mg 
                 100 
                 31 Oleic 
               
               
                 F 
                 E/15% MAA 
                 Mg 
                 100 
                 38 Oleic 
               
               
                 G 
                 E/10% iBA/10% 
                 Zn 
                 100 
                 30 Oleic 
               
               
                   
                 MAA 
               
               
                 H 
                 E/15% MAA 
                 Zn 
                 100 
                 30 Oleic 
               
               
                   
               
             
          
         
       
     
     
       
         
               
             
               
               
               
             
           
               
                 TABLE 9 
               
             
             
               
                   
               
               
                 Permeability 
               
             
          
           
               
                   
                 WVTR (37.8° C., 
                 OPV (23° C., 
               
               
                   
                 100% RH) 
                 50% RH) 
               
               
                 Blend 
                 g-mil/100 in 2 /Day 
                 cc-mil/100 in 2 /Day · atm 
               
               
                   
               
               
                 C 
                 4.85 
                 2493 
               
               
                 D 
                 6.07 
                 2739 
               
               
                 E 
                 4.18 
                 2131 
               
               
                 F 
                 4.4  
                 2728 
               
               
                   
               
             
          
         
       
     
     EXAMPLE 4 
     A series of highly neutralized blends of ionomer and fatty acid were made from various ethylene-α,β ethylenically unsaturated carboxylic copolymers or ionomers. Reactant Resin “I” was a copolymer of ethylene and 15% methacrylic acid, neutralized 58% with Zn. Reactant Resin “J” was a copolymer of ethylene and 15% methacrylic acid. The reaction in an extruder involved various residence times in the extruder, magnesium or zinc neutralizations, and purity of oleic acid raw material. The oleic acid was either 70% pure (Technical Grade), 99.5% pure, or 99.5% pure and de-odorized as supplied by City Chemicals Inc. (West Haven, Connecticut). 300 ppm of the phenolic antioxidant IRGANOX E201 (available from Ciba Geigy Inc. Tarrytown, N.Y.) was blended into each of the oleic acid samples before the reaction. A total of 1000 ppm of IRGANOX 1010 was melt-blended into the total compositions during the reaction. Zinc was added as zinc oxide. Magnesium was added as magnesium hydroxide. The amount of zinc and magnesium were adjusted for 100% theoretical neutralization of the acid moieties on the ethylene-α,β ethylenically unsaturated carboxylic copolymers or ionomer plus the acid moieties of the added oleic acid. The amount of oleic acid in the reaction mixture was 25% and 30% for the zinc and magnesium neutralized systems respectively. The reaction was carried out at 255° C. melt temperature in a single screw extruder. The melt strand was water quenched, air-blow dried, pelletized and bagged. Immediately after bagging, 50 grams of sample pellets were placed into 8-ounce glass containers and sealed. The containers were aged 4 days at 70° C. 
     In a second test, the resin was extruded at 200° C. into monolayer films using a 100-second residence time. The film was blown into a tube such that the thickness of the film was 5 mils. A 13 cm×23 cm sample of film was immediately placed into a similar sized polyethylene bag for 1 week. 
     The samples were graded on a relative scale for odor wherein 10 indicates the highest odor and 0 indicates no odor. The results are reported in Table 10. 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 10 
               
               
                   
               
               
                   
                   
                   
                 Residence 
                 Odor in 
                   
               
               
                   
                   
                   
                 Time in 
                 pellets 
                 Odor of 
               
               
                 Carboxylic 
                 Neutral- 
                   
                 Reactive 
                 after 4 
                 film after 
               
               
                 acid 
                 izing 
                 Oleic Acid 
                 Extruder 
                 days at 
                 1 week at 
               
               
                 copolymer 
                 Cation 
                 Purity 
                 (seconds) 
                 70° C. 
                 22° C. 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 Resin I 
                 Zn 
                 99.5%, 
                 140 
                 1.5 
                 0.1 
               
               
                   
                   
                 deodorized 
               
               
                 Resin I 
                 Zn 
                 99.5%, 
                 178 
                 2 
                 0.5 
               
               
                   
                   
                 deodorized 
               
               
                 Resin I 
                 Zn 
                 99.5%, 
                 120 
                 2 
                 3 
               
               
                   
                   
                 deodorized 
               
               
                 Resin I 
                 Zn 
                 99.5%, 
                 98 
                 — 
                 0.5 
               
               
                   
                   
                 deodorized 
               
               
                 Resin J 
                 Mg 
                 99.5%, 
                 116 
                 1 
                 0.5 
               
               
                   
                   
                 deodorized 
               
               
                 Resin J 
                 Mg 
                 99.5%, 
                 226 
                 5 
                 0.1 
               
               
                   
                   
                 deodorized 
               
               
                 Resin J 
                 Mg 
                 99.5%, 
                 78 
                 1 
                 0.5 
               
               
                   
                   
                 deodorized 
               
               
                 Resin J 
                 Mg 
                 99.5% 
                 ~180 
                 0.5 
                 0.5 
               
               
                 Resin J 
                 Mg 
                   70% 
                 ~180 
                 4 
                 4 
               
               
                   
               
             
          
         
       
     
     The result shows the benefit of low odor for unsaturated fatty acids by use of high purity fatty acids in combination with stabilizers. 
     Having thus described and exemplified the invention with a certain degree of particularity, it should be appreciated that the following claims are not to be so limited but are to be afforded a scope commensurate with the wording of each element of the claim and equivalents thereof.