Multiple layer film with amorphous polyamide layer

Information

  • Patent Grant
  • 6500559
  • Patent Number
    6,500,559
  • Date Filed
    Monday, May 4, 1998
    26 years ago
  • Date Issued
    Tuesday, December 31, 2002
    21 years ago
Abstract
A film includes a core layer having an amorphous polyamide; two intermediate layers, disposed on opposite surfaces of the core layer, including a semicrystalline polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, including a polymeric adhesive; and two outer layers, each disposed on a surface of a respective adhesive layer, including an ethylene/alpha olefin copolymer, propylene homopolymer, or propylene/alpha olefin copolymer; and a second outer layer, disposed on a surface of a respective adhesive layer, including amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, or propylene/alpha olefin copolymer. The film can alternatively have a core layer including a polymeric adhesive, and two intermediate layers each having an amorphous polyamide. A method of packaging a product using these films, and a package, are also disclosed.
Description




FIELD OF THE INVENTION




The present invention relates to a thermoplastic film that can be used to make packages for a wide variety of food and non-food products.




BACKGROUND OF THE INVENTION




Vertical form/fill/seal (VFFS) packaging systems have proven to be very useful in packaging a wide variety of flowable products. An example of such systems is the Onpack™ flowable food packaging system sold by W. R. Grace & Co.-Conn. through its Grace Packaging group. The VFFS process is known to those of skill in the art, and described for example in U.S. Pat. No. 4,589,247 (Tsuruta et al), incorporated herein by reference. A flowable product is introduced through a central, vertical fill tube to a formed tubular film having been sealed transversely at its lower end, and longitudinally. The pouch is then completed by sealing the upper end of the tubular segment, and severing the pouch from the tubular film above it.




The choice of packaging materials is important, and should be matched to the intended end use of the pouch.




Several properties are often desirable in such pouches.




Dimensional stability is of great importance in VFFS systems. In such systems, the equipment fills a pouch to a certain level. If the film stretches, too much product is put into the pouch. This phenomenon makes it difficult to standardize pouch dimensions, which leads for example to difficulty in packing off of pouches in shipping boxes of pre-determined size.




Sometimes a pouch material is used to package a product, such as an aqueous liquid food product, at an elevated temperature of 170 to 210° F. This is known as a hot fill process. Sometimes the pouch, after filling, is exposed to retort conditions. In either case, the dimensional stability of the package is severely tested, and the possibility of package distortion increases.




The package material is preferably stiff (i.e. has a high modulus), especially at high temperatures. This is often necessary because the film tracks more easily on a packaging machine. Also, a hot fin seal can stretch undesirably; therefore, to preserve seal integrity, the ability to package at high speeds is limited by the degree to which hot seals will elongate or stretch. If a heavy load, e.g. 5 to 20 pounds of shredded cheese, is thrust into a pouch with transverse seals just formed, these seals are still hot and the pouch, or the seal area of the pouch, can deform. More uniform package length is related to more uniform package weight, which is important to the food processor in order to provide packages with consistent weights.




Good tensile strength is necessary in films used for such applications. Where flowable foods are packaged, as in many VFFS applications, the hydrostatic pressure of many oil and water based foods requires a tough, impact and abuse resistant packaging material that will maintain its structural integrity during the packaging process, and subsequent distribution and storage.




For hot fill and retort applications, heat resistance is essential to avoid package distortion or degradation of the film itself, or of the transverse and longitudinal seals associated with the VFFS process.




Oxygen barrier properties are also essential in end-uses where the product is susceptible to oxidative degradation.




Depending on the packaging process, form of the package, and nature of the product, physical properties such as barrier to ultraviolet light, surface printability, clarity, flatness, thermoformability, and low tear initiation and propagation (for easy-open packages) may become significant.




The inventors have found that a combination of many of these properties is possible through the use of at least one layer consisting essentially of amorphous polyamide in a multilayer thermoplastic film.




SUMMARY OF THE INVENTION




In a first aspect, a multilayer film comprises a core layer consisting essentially of an amorphous polyamide; two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer.




In a second aspect, a multilayer film comprises a core layer comprising an amorphous polyamide adhesive; two intermediate layers, disposed on opposite surfaces of the core layer, consisting essentially of an amorphous polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of the respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer.




In a third aspect, a method of packaging a food product comprises providing a rollstock film, the film comprising a core layer consisting essentially of an amorphous polyamide; two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer; forming the film into a tube in a vertical/form/fill/seal process; filling the tube with a food product; and closing the tube to form a sealed pouch containing the food product.




In a fourth aspect, a package comprises a flowable food product; and a pouch containing the food product, the pouch made from a film comprising a core layer consisting essentially of an amorphous polyamide; two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer.




In a fifth aspect, a method of packaging a food product comprises providing a rollstock film, the film comprising a core layer comprising an amorphous polyamide adhesive; two intermediate layers, disposed on opposite surfaces of the core layer, consisting essentially of an amorphous polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of the respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer; forming the film into a tube in a vertical/form/fill/seal process; filling the tube with a food product; and closing the tube to form a sealed pouch containing the food product.




In a sixth aspect, a package comprises a flowable food product; and a pouch containing the food product, the pouch made from a film comprising a core layer comprising an amorphous polyamide adhesive; two intermediate layers, disposed on opposite surfaces of the core layer, consisting essentially of an amorphous polyamide; two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and two outer layers, each disposed on a surface of the respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer; forming the film into a tube in a vertical/form/fill/seal process; filling the tube with a food product; and closing the tube to form a sealed pouch containing the food product.




Definitions




“Adhesive” herein refers to polymeric adhesive, more preferably an olefin polymer or copolymer having an anhydride functionality grafted thereon and/or copolymerized therewith and/or blended therewith.




“Amorphous polyamide” herein refers to those polyamides which are lacking in crystallinity as shown by the lack of an endotherm crystalline melting peak in a Differential Scanning Calorimeter (DSC) test (ASTM D-3417). Examples of such polyamides include those amorphous polymers prepared from the following diamines: hexamethylenediamine, 2-methylpentamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4- trimethylhexamethylenediamine, bis(4-aminocyclohexyl)methane, 2,2-bis(4-aminocyclohexyl)isopropylidine, 1,4-diaminocyclohexane, 1,3-diaminocyclohexane, meta-xylylenediamine, 1,5-diaminopentane, 1,4-diaminobutane, 1,3-diaminopropane, 2-ethyldiaminobutane, 1,4-diaminomethylcyclohexane, p-xylylenediamine, m-phenylenediamine, p-phenylenediamine, and alkyl substituted m-phenylenediamine and p-phenylenediamine. Examples of polyamides that can be used include those amorphous polymers prepared from the following dicarboxylic acids: isophthalic acid, terephthalic acid, alkyl substituted iso- and ter-ephthalic acid, adipic acid, sebacic acid, butane dicarboxylic acid, and the like. The diamines and diacids mentioned above can be combined as desired, provided the resulting polyamide is amorphous. That is, an aliphatic diamine can generally be combined with an aromatic diacid, or an aromatic diamine can generally be combined with an aliphatic diacid to give suitable amorphous polyamides. Preferred amorphous polyamides are those in which either the diamine or the diacid moiety is aromatic, and the other moiety is aliphatic. The aliphatic groups of these polyamidesides preferably contain between 4 and 12 carbon atoms in a chain or an aliphatic cyclic ring system having up to 15 carbon atoms. The aromatic groups of the polyamides preferably have mono or bicyclic aromatic rings which may contain aliphatic substituents of up to about 6 carbon atoms.




“Amorphous polyamide adhesive” herein refers to those polymeric materials which bond a layer of amorphous polyamide to a layer comprising another polymer or blend of polymers. Preferred polymeric materials include semicrystalline polyamide; anhydride grafted polymers such as anhydride grafted ethylene/1-butene copolymer, anhydride grafted ethylene/1-hexene copolymer, and anhydride grafted ethylene/1-octene copolymer; ethylene/acrylic acid copolymer; and ethylene/methacrylic acid copolymer.




“Anhydride functionality” herein refers to any form of an hydride functionality, such as the anhydride of maleic acid, fumaric acid, etc., whether grafted onto a polymer, copolymerized with a polymer, or blended with one or more polymers, and is also inclusive of derivatives of such functionalities, such as acids, esters, and metal salts derived therefrom.




“Core layer” herein refers to the central layer of a multi-layer film.




“Ethylene/alpha-olefin copolymer” (EAO) herein refers to copolymers of ethylene with one or more comonomers selected from C


4


to C


10


alpha-olefins such as butene-1 (i.e., 1-butene), hexene-1, octene-1, etc. in which the molecules of the copolymers comprise long chains with relatively few side chain branches or cross-linked structures. This molecular structure is to be contrasted with conventional low or medium density polyethylenes which are more highly branched than their respective counterparts. EAO includes such heterogeneous materials as linear medium density polyethylene (LMDPE), linear low density polyethylene (LLDPE), and very low and ultra low density polyethylene (VLDPE and ULDPE); as well as homogeneous polymers (HEAO) such as TAFMER™ ethylene/alpha olefin copolymers supplied by Mitsui Petrochemical Corporation and metallocene-catalyzed polymers such as EXACT™ resins supplied by Exxon and AFFINITY™ resins supplied by the Dow Chemical Company. EAO includes long chain branched homogeneous ethylene/alpha-olefin copolymer. An EAO can for example, have a density of between 0.916 and 0.945 grams/cc.




“Ethylene/vinyl ester copolymer” (E/VE) herein refers to a copolymer derived from ethylene and an ester such as vinyl acetate, alkyl acrylate, methyl methacrylate, or other monomers, wherein the ethylene derived units in the copolymer are present in major amounts and the ester derived units in the copolymer are present in minor amounts.




“Flowable materials” herein means food or non-food items which are flowable under gravity, or can be pumped, as defined in U.S. Pat. No. 4,521,437 (Storms), incorporated by reference herein in its entirety.




“Heat shrinkable” herein is a property of a material which, when heated to an appropriate temperature above room temperature (for example 96° C.), will have a free shrink of 5% or greater in at least one linear direction.




“High density polyethylene” (HDPE) herein has a density of 0.94 grams per cubic centimeter to 0.96 grams per cubic centimeter.




“Intermediate” herein refers to a layer of a multi-layer film which is between an outer layer and core layer of the film.




“Linear low density polyethylene” (LLDPE) herein has a density in the range of from 0.916 to 0.925 grams per cubic centimeter.




“Linear medium density polyethylene” (LMDPE) herein has a density from 0.926 grams per cubic centimeter to 0.939 grams per cubic centimeter.




“Outer layer” herein refers to what is typically an outermost, usually surface layer of a multi-layer film, although additional layers and/or films can be adhered to it.




“Polyamide” herein refers to both polyamides and copolyamides, and means a polymer in which amide linkages (—CONH—) occur along the molecular chain. Examples are nylon 6, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 612, nylon 6/66, and amorphous polyamide.




“Polymer” herein refers to homopolymer, copolymer, terpolymer, etc. “Copolymer” herein includes copolymer, terpolymer, etc.




“Propylene/alpha-olefin copolymer” herein refers to copolymers of propylene with one or more comonomers selected from ethylene, and butene-1 (i.e., 1-butene).




“Semicrystalline polyamide” herein refers to polyamides having readily determined crystalline melting points, for example, nylon 6, 9, 11, and 12. Such nylons may also have amorphous regions, and may even have measurable glass transition temperatures.




All compositional percentages used herein are calculated on a “by weight” basis.




“LD” or “MD” herein refers to longitudinal direction or machine direction respectively, synonymous terms for the direction of the film parallel to the path of extrusion. “TD” or “CD” herein refers to transverse or cross direction respectively, synonymous terms for the direction of the film transverse to the path of extrusion.











BRIEF DESCRIPTION OF THE DRAWINGS




A detailed description of preferred embodiments of the invention follows, with reference to the attached drawings, wherein:





FIG. 1

is a cross-sectional view of a seven layer film.





FIG. 2

illustrates a vertical form fill and seal apparatus which can be used in connection with the film and method of the present invention, to make a package of the present invention.





FIG. 3

is a cross-sectional view of an eight layer film.





FIG. 4

is a cross-sectional view of a nine layer film.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring to

FIG. 1

, which is a cross-sectional view of a seven layered embodiment of the present invention, a film


20


comprising a core layer


27


, two intermediate layers


26


and


28


, two polymeric adhesive layers


22


and


23


, and two outer layers


24


and


25


. Outer layers


24


and


25


are preferably surface layers.




Core layer


27


consists essentially of an amorphous polyamide. Preferred amorphous polyamides include Grivory™ G21 nylon from EMS, Selar™ PA 3426 from DuPont, and Novatec™ X21 from Mitsubishi Chemical. These commercial materials are nylon 6I/6T.




Small amounts of additives such as slip or antiblock agents, pigments, processing aids and the like can be included in core layer


27


, as long as they do not materially affect the basic and novel characteristics of the film. Semi-crystalline polyamide is not present in core layer


1


.




Intermediate layers


26


and


28


comprise semicrystalline polyamide. Preferred semicrystalline polyamides include nylon 6, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 612, nylon 6/66, nylon 6/12 copolymer, nylon 6/66 copolymer, nylon 66/610 copolymer, nylon 6/69 copolymer, and blends of any of the above.




Polymeric adhesive layers


22


and


23


comprise a polymeric adhesive, and more specifically an olefin polymer or copolymer having an anhydride functionality grafted thereon and/or copolymerized therewith and/or blended therewith. Preferred polymeric adhesives are anhydride grafted ethylene/1-butene copolymer, anhydride grafted ethylene/1-hexene copolymer, and anhydride grafted ethylene/1-octene copolymer. Amorphous polyamide adhesives include semicrystalline polyamide, and anhydride grafted polymers.




Outer layers


24


and


25


each comprise a polymer selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha-olefin copolymer, propylene homopolymer, and propylene/alpha-olefin copolymer. Preferred materials, depending on the desired end-use application, are amorphous polyamide, semicrystalline polyamide, linear low density polyethylene (linear ethylene/C


4


-C


10


alpha-olefin copolymer), metallocene-catalyzed ethylene/C


4


-C


10


alpha-olefin copolymer, and propylene/ethylene copolymer.




In an alternative embodiment, a film is like that just described and shown in

FIG. 1

, except that the core layer comprises an amorphous polyamide adhesive, and the two intermediate layers


26


and


28


consist essentially of amorphous polyamide. The polymeric adhesive and the amorphous polyamide can be any of those disclosed herein. In this alternative embodiment, the two outer layers both comprise any of the materials disclosed above.




In the alternative embodiment just described, semi-crystalline polyamide is not present in intermediate layers


26


and


28


.




In

FIG. 2

, a vertical form fill and seal apparatus


40


is schematically illustrated. Vertical form fill and seal equipment and processes are well known to those of skill in the packaging art. The following documents disclose a variety of equipment suitable for vertical form fill and seal: U.S. Pat. Nos. 2,956,383; 3,340,129 to J. J. Grevich; U.S. Pat. No. 3,611,657, to Kiyoshi Inoue, et. al.; U.S. Pat. No. 3,703,396, to Inoue, et. al.; U.S. Pat. No. 4,103,473, to Bast, et. al.; U.S. Pat. No. 4,589,247; U.S. Pat. No.4,532,752, to Taylor; U.S. Pat. No. 4,532,753, to Kovacs; and U.S. Pat. No. 4,571,926, to Scully, all incorporated by reference herein in their entirety. Apparatus


40


utilizes multilayer film


41


according to the present invention. Thus, film


41


can be any of films


20


,


60


,


70


as described herein. Product


42


, to be packaged, is supplied to apparatus


40


from a source (not illustrated), from which a predetermined quantity of product


42


reaches upper end portion of forming tube


44


via funnel


43


, or other conventional means. The packages are formed from the film in a lower portion of apparatus


40


, and flexible sheet material


41


from which the bags or packages are formed is fed from roll


51


over certain forming bars (not shown for the sake of clarity), is wrapped about forming tube


44


, and is provided with longitudinal seal


47


by longitudinal heat sealing device


46


, resulting in the formation of vertically-oriented tube


48


. End seal bars


45


operate to close and seal horizontally across the lower end of vertically-sealed tube


48


, to form pouch


50


which is thereafter immediately packed with product


42


. A means for advancing and/or voiding a portion of the tube


48


, such as film drive rollers


52


, advance tube


48


and pouch


50


a predetermined distance, after which end seal bars


45


close and simultaneously seal horizontally across the lower end of vertically-sealed tube


48


as well as simultaneously sealing horizontally across upper end of sealed pouch


49


, to form a product packaged in sealed pouch


49


. The next pouch


50


, thereabove, is then filled with a metered quantity of product


42


, advanced, and so on. It is also conventional to incorporate with the end seal bars a cut-off knife (not shown) which operates to sever a lower sealed pouch


49


from the bottom of upstream pouch


50


.




Referring to

FIG. 3

, which is a cross-sectional view of an eight layered embodiment of the present invention, a film


60


comprises a core layer


65


, two intermediate layers


64


and


66


, and two outer layers


62


and


68


. Adhesive layers


63


and


67


bond outer layers


62


and


68


respectively to intermediate layers


64


and


66


respectively. The layers for this film can comprise the same materials as disclosed for the equivalent layers in

FIG. 1

, in either the first embodiment or alternative embodiment discussed above. Thus, core layer


65


can have the same materials as disclosed above for core layer


27


(i.e. an amorphous polyamide or polymeric adhesive); intermediate layers


64


and


66


can comprise the same materials as disclosed above for intermediate layers


26


and


28


; and so on.




In

FIG. 3

, an additional layer


61


is shown adhered to layer


62


at interface


69


. This additional material can be any suitable polymeric material, and is preferably a discrete film adhered to layer


62


by a suitable adhesive such as polyurethane. Layer


61


can comprise e.g. a saran, polyester, or nylon film. This film


61


can be unoriented, or monoaxially or biaxially oriented. If layer


61


is intended to function as a sealant, it preferably comprises a polyolefin such as EAO, ionomer, or propylene homopolymer or copolymer. Layer


61


can also be coextruded with the other layers of the film.




Referring to

FIG. 4

, which is a cross-sectional view of a nine layered embodiment of the present invention, a film


70


comprising a core layer


75


, two intermediate layers


74


and


76


, and two outer layers


72


and


78


. Adhesive layers


73


and


77


bond outer layers


72


and


78


respectively to intermediate layers


74


and


76


respectively. An additional layer


71


is shown adhered to layer


72


, and an additional layer


79


is shown adhered to layer


78


. The layers for this film can comprise the same materials as disclosed for the equivalent layers in

FIG. 1

, in either the first embodiment or alternative embodiment discussed above. Thus, core layer


75


can comprise the same materials as disclosed above for core layer


27


; intermediate layers


74


and


76


can comprise the same materials as disclosed above for intermediate layers


26


and


28


, and so on.




The additional layers


71


and


72


can comprise the same materials as those of layer or film


61


. In each case, the additional layer or layers can be a discrete film adhered to the adjacent layer by gluing, heat and pressure, or other appropriate bonding technique; or can be made with the remainder of the film in a coextrusion process. Layers


71


and


72


are preferably the same, but can be different from each other.




The invention can be further understood by reference to the examples given below. Final film thicknesses can vary, depending on process, end use application, etc. Typical thicknesses range from 0.1 to 20 mils, more preferably 1 to 10 mils, and especially 2 to 7 mils.




Table 1 identifies the materials used in the examples and comparative examples. The remaining tables describe the formulations and/or properties of films made with these materials.
















TABLE 1











Material




Tradename




Source



























1




ADH1
















2




ION1




Surlyn ™1650




DuPont






3




PO1




Escorene ™ PP-4292.E1




Exxon






4




ADH2




Plexar ™PX 114




Quantum/USI






5




PET1




Melinex 800




ICI






6




MB1




1080864S




Reed Spectrum






7




NY1




Capron ™B100WP




Allied Signal






8




ADH3






9




NY2




Ultramid ™KR-4407




BASF






10




PET2




48 LB Mylar ™




DuPont






11




MB2




Grilon ™XE 3361




EMS






12




ADH4




Tymor ™1203




Morton International






13




PO2




Dowlex ™2244A




Dow






14




PO3




Exact ™ 3027




Exxon






15




PO4




Escorene XW 70.AV




Exxon






16




EVOH1




LC-H101BD




EVALCA






17




NY3




Ultramid ™ B 35 Natural




BASF






18




PO5




Elvax ™ EP 6449




DuPont






19




PO6




Dowlex NG 3347A




Dow






20




PO7




SLX-9103




Exxon






21




PO8




Exceed ™ECD-401A




Exxon






22




ADH5




Plexar ™PX 107 A




Millenium






23




PO9




Escorene ™LD-134.09




Exxon






24




ADH6




Tymor ™1228B




Morton International






25




PO10




Escorene ™LD-200.48




Exxon






26




MB3




10853




Ampacet






27




ADH7




Coreactant 9L23




Morton International






28




MB4




FSU 255E




A. Schulman






29




ANY1




Grivory ™ G21




EMS






30




EVOH2




Soarnol ™ ET




Nippon Gohsei






31




PO11




Attane ™4201




Dow






32




PET3




Shinplex ™ Polyester PET-SK




Phoenix Films






33




ADH8
















34




PET4




EG Polyester Film (48 gauge)




STC Films






35




Add 1




Micromark #20 Powdered




W-R Industries








Starch






36




MB5




Conpol ™ 13B




DuPont






37




PO12




PE1042CS15




Rexene






38




ADH9




Bynel ™CXA 3095




DuPont






39




PO14




Escorene ™LD-733.66




Exxon






40




PO15




STS-33C




MSI Technology














ADH1 is the equivalent of a mixture of 100 pounds (11.4 gallons) ADH3, 4 pounds (0.4 gallons) ADH7, and enough ADH8 to result in a mixture containing 35% solids.




ION1 is a zinc salt of ethylene/methacrylic acid copolymer.




PO1 is a propylene homopolymer.




ADH2 is an anhydride grafted ethylene/vinyl acetate copolymer.




PET1 is an uncoated, non-formable polyethylene terephthalate (polyester) film with a thickness of 0.48 mils.




MB1 is a masterbatch having 70% nylon 6, 20% antiblocking (diatomaceous earth), and 10% slip agent (erucamide).




NY1 is nylon 6 (polycaprolactam).




ADH3 is a urethane with 39.7% ethyl acetate, and 5.0% methylene bisphenyl isocyanate, with a solids content of 59 to 61%.




NY2 is nylon 6 (polycaprolactam).




PET2 is an uncoated polyethylene terephthalate (polyester) film with thickness of 0.48 mils.




MB2 is a masterbatch having nylon 6, with a small amount of an antiblocking agent, and a slip agent.




ADH4 is a major amount of a linear ethylene/butene-1 copolymer blended with a maleic anhydride modified polyethylene and an ethylene/propylene rubber.




PO2 is an ethylene/octene-1 copolymer with a density of 0.916 grams/cc.




PO3 is a single site catalyzed ethylene/butene copolymer with a density of 0.900 grams/cc.




PO4 is a low density polyethylene resin.




EVOH1 is an ethylene/vinyl alcohol copolymer with 38 mole percent ethylene.




NY3 is nylon 6 (polycaprolactam).




PO5 is a blend of 75% ethylene/vinyl acetate copolymer having a vinyl acetate content of 12% by weight of the polymer, 5% propylene homopolymer, and 20% butylene/ethylene copolymer.




PO6 is an ethylene/octene copolymer with a density of 0.917 grams/cubic centimeter.




PO7 is a single site catalyzed ethylene/hexene/butene terpolymer with a density of 0.901 grams/cc.




PO8 is a single site catalyzed ethylene/hexene copolymer with a density of 0.917 grams/cc.




ADH5 is an anhydride modified polyolefin in ethylene/vinyl acetate copolymer.




PO9 is a low density polyethylene resin.




ADH6 is a major amount of ethylene/butene copolymer blended with a maleic anhydride grafted polyethylene.




PO10 is low density polyethylene with a density of 0.917 grams/cc.




MB3 is a masterbatch having linear low density polyethylene and an antiblocking agent (diatomaceous earth).




ADH7 is a urethane with 25.0% ethyl acetate, 9.4% gamma-aminopropyltriethyoxysilane, and 9.4% diethylene glycol.




MB4 is a masterbatch having 67.9% low density polyethylene, 25% diatomaceous earth, 5/0% erucamide, and 0.1% stabilizer.




NY1 is an amorphous copolyamide (6I/6T) derived from hexamethylene diamine, isophthalic acid, and terephthalic acid.




EVOH2 is an ethylene/vinyl alcohol copolymer with 38 mole percent ethylene.




PO11 is an ethylene/octene copolymer with a density of 0.912 grams/cc.




PET3 is an uncoated, non-formable polyethylene terephthalate (polyester) film with a thickness of 0.48 mils.




ADH8 is ethyl ester of acetic acid.




PET4 is an uncoated, biaxially oriented polyethylene terephthalate (polyester) film with a thickness of 0.48 mils.




Add1 is food starch with a small percentage of additives.




MB5 is an ionomer-based anti-block concentrate.




PO12 is a low density polyethylene with a density of 0.922 grams/cc.




ADH9 is an anhydride grafted polyolefin in ethylene/vinyl acetate copolymer.




PO14 is ethylene/vinyl acetate copolymer having a vinyl acetate content of 19.3% by weight of the polymer, and a melt index of 30.




PO15 is a compounded ethylene/vinyl acetate copolymer having a density of 0.916 grams/cc, and a melt index of 1.6.




EXAMPLES




Three film structures containing an amorphous polyamide core were tested on a Hayssen Ultima™ packaging machine. This type of equipment is intended for the packaging of non-flowable dry goods such as IQF applications, cake mixes, shredded cheese, confections, etc.




The films, and the comparative examples (“Comp” in the Tables) discussed below, had the structures shown in Table 2. These were each made by a coextrusion of the layers. The gauge (in mils) of each layer of each film structure is shown below each respective structure in the various tables. The layer farthest to the right in Table 2 and the remaining tables would preferably form the food or product contact layer in a typical packaging application. Examples 1 and 2 a had a total thickness of 4.0 mils. Example 2, and Comp. Example 3, had a total thickness of 4.5 mils. Comp. Example 2 had a total thickness of 3.5 mils. A mil is equal to 0.001 inches, or 25.4 micrometers.













TABLE 2









Example




Structure































1




96% NY2




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




48% PO8







 2% MB2





20%





20%





10%




48% PO7







 2% MB1





aNY1





aNY1





PO10




 4% MB4







0.52




0.76




0.26




0.8




0.26




0.32




0.76




0.32






2




96% NY2




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




48% PO8







 2% MB2





20%





20%





10%




48% PO7







 2% MB1





aNY1





aNY1





PO10




 4% MB4







0.59




1.08




0.29




0.45




0.29




0.36




1.08




0.36






2a




96%




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




48% PO8







aNY1





20%





20%





10%




48% PO7







 2% MB2





aNY1





aNY1





PO10




 4% MB4







 2% MB1







0.52




0.76




0.26




0.8




0.26




0.32




0.76




0.32






Comp.




96% NY2




ADH9




80% NY1




ADH6




80% NY1




ADH6




90% PO8




48% PO8






2




 2% MB2





20%





20%





10%




48% PO7







 2% MB1





aNY1





aNY1





PO10




 4% MB4







0.46




0.87




0.23




0.28




0.23




0.28




0.87




0.28






Comp.




96% NY2




ADH9




85% NY3




ADH6




85% NY3




ADH6




90% PO2




96% PO8






3




 2% MB2





15%





15%





10%




 4% MB4







 2% MB1





aNY1





aNY1





PO10







0.59




1.12




0.29




0.45




0.29




0.36




1.04




0.36














Examples 1, 2, and 2a were evaluated for their machinability characteristics versus Comp. Examples 2 and 3. Example 2a contained an amorphous polyamide outer layer as well as a core layer of amorphous polyamide. This film did not “machine”, i.e. track on the package machine, very well. The amorphous polyamide outer layer, in this case a surface layer of the film, resulted in sticking along the horizontal jaws of the machine. This problem prevented any extended runs. Example 1, with an amorphous polyamide core forming 20% of the total film thickness, ran without any problems at 40 packages/minute. The added stiffness provided by the amorphous polyamide appeared to assist with cutting and any stretching resulting at the horizontal jaws. In order to attain the optimum vertical seal appearance, the platen seal bar of the machine was coated with Teflon™ tape. The Teflon along with the 20% amorphous polyamide core did result in higher operating temperatures; however, this did not adversely affect the seals or the machining of this structure. Example 2, with an amorphous polyamide core forming 10% of the total film thickness, ran very similar to Example 1, showing no signs of any problems. Teflon tape was still needed to attain the optimum vertical seal appearance.




All three film structures exhibited significant abuse and puncture resistance which was tested on an Burst Tester. The Burst Tester is constructed as follows. Upper and lower rectangular metal plates are mounted on a two-piece hinged welded aluminum frame. Upper and lower “arms” of the framework are each about 26″ long and form a rigid “lever arm” for the mounting of the two rectangular plates. The plates are mounted so that their surfaces will mate when the “arms” are brought together. The plates are positioned about 3″ from the hinge on the arms of the welded frame leaving about 12″ to 14″ protruding on the opposite side of the plates for extra leverage. The upper plate measures 15″×8¾″; the lower plate measures 14″×8″. In the exact centroid of the upper plate is a circular opening covered by a rubber diaphragm to which a pressure-transducing tube is attached, and in turn connected to an Aschcroft™ pressure gauge which protrudes above the top plate. The purpose of this arrangement is to generate a hydrostatic or pneumatic pressure within sealed, filled test pouches by squeezing the lever arms together in a bellows fashion. The induced pressure in the test sample is in turn transferred through the pressure transducing tube mounted in the circular opening drilled in the upper plate, to the pressure gauge, allowing a quantitative psig reading to be taken.




In operation, a fluid-filled (air) heat sealed pouch was in each test sequence placed squarely between two plates mounted on the two-piece, bellows-like hinged frame. The test unit was placed on the floor and pressure applied by hand or foot until a rupture-type failure occurs. Maximum hydrostatic pressure generated is then recorded from a sliding needle-stop marker which is part of the pressure gauge. Some pouches exceeded the maximum graduation on the pressure gauge, which was 15 psig, i.e. some pouches withstood, without failure, the force exerted by an adult human standing at the end of the lever arm.




The results are shown in Table 3 below. The structure of Comp. 5 can be found in Table 4.















TABLE 3












Burst Test Results







Example




(psig)



























1




>15







2




>15







2a




>15







Comp. 2




6







Comp. 5




8.5















It can be seen from Table 3 that films of the invention reached the limits of the tester without any failures resulting. Beneficial attributes of Examples 1, 2, and 2a are their resistance to stretching, ease of cutting, and the added stiffness for advancing the film over the spreaders. In comparison, both of the comparative films tested failed well below the 15 psig threshold.




A separate study was conducted to measure the flex crack resistance of amorphous polyamide containing structures. One additional film of the invention was evaluated (Example 3). Several Comparative Examples were used as controls for this evaluation. These are identified in Table 4.













TABLE 4









Example




Structure































3




96% NY2




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




48% PO8







 2% MB2





20%





20%





10%




48% PO7







 2% MB1





aNY1





aNY1





PO10




 4% MB4







0.40




0.72




0.19




0.30




0.19




0.24




0.72




0.24






Comp.




96% NY2




ADH9




85% NY3




ADH6




85% NY3




ADH6




90% PO2




96% PO8






4




 2% MB2





15%





15%





10%




 4% MB4







 2% MB1





aNY1





aNY1





PO10







0.45




0.87




0.23




0.35




0.23




0.28




0.81




0.28






Comp.




96% NY2




ADH9




80% NY1




ADH6




80% NY1




ADH6




90% PO8




48% PO8






5




 2% MB2





20%





20%





10%




48% PO7







 2% MB1





aNY1





aNY1





PO10




 4% MB4







0.60




1.12




0.29




0.36




0.29




0.36




1.12




0.36






Comp.




88% PO8




ADH4




75% NY2




EVOH




75% NY2




ADH9




98% NY2






6




10%





25%




2




25%





 2% MB2







PO10





aNY1





aNY1







 2% MB3







1.24




0.32




0.26




0.40




0.26




1.0




0.52






Comp.




88% PO8




ADH4




75% NY2




EVOH




75% NY2




ADH9




98% NY2






7




10%





25%




2




25%





 2% MB2







PO10





aNY1





aNY1







 2% MB3







0.93




0.24




0.19




0.30




0.20




0.75




0.39




















Comp.




97% PO7




ADH5




ADH4




EVOH




ADH4




ADH5




PO12




ADH1




PET1






8




 3% MB4






2







1.00




0.20




0.13




0.25




0.13




0.17




0.62




0.02




0.48














The samples were subjected to ASTM F392-74-D (Gelbo flex test) which subjects the film through 20 cycles on a Model 100 Flex Tester (Manufactured by Rogers International). After completion of the flex testing, samples were tested for oxygen transmission in accordance with ASTM 3985. The results are shown in Table 5.












TABLE 5











Oxygen Transmission Rate Results (cc/sq. m./day/)
















Sample ID




Sample 1




Sample 2




Average




















Example 1




18.7




18.8




18.75







Example 2




24.4




24.6




24.5







Example 3




35.4




33.3




34.35







Comp. 4




40.1




41.9




41.0







Comp. 5




35.2




36.0




35.6







Comp. 6




1.35




1.29




1.32







Comp. 7




3.43




2.75




3.09







Comp.8




1.69




1.52




1.6















These results indicate that all of the films tested withstood the flex crack test without showing any signs of barrier loss. This also confirms that no pinholes were found in the stressed area subjected to the oxygen transmission rate testing. These results are unexpected, in that the conventional commercial understanding is that films containing amorphous polyamide have poor flex crack resistance.




Some commercial films can undesirably stretch while being filled in a VFFS system with a high temperature food product such as hot tomato sauce. This stretching is believed to be a significant factor in weight variation among pouches. Developmental vertical form/fill/seal (VFFS) structures which should exhibit increased performance in this area were made and needed to be evaluated for fitness-for-use (FFU). Evaluation of oxygen barrier properties was necessary before the other FFU criteria—abuse resistance, stretch-resistance, sealability, machinability, etc.—could be tested in a commercial setting. Two additional films in accordance with the invention, and five comparative Examples, were thus evaluated using a low oxygen transmission imaging system (LOTIS) for estimated oxygen transmission rates (OTR's) under hydrating conditions. The LOTIS methodology is described in U.S. Pat. No. 5,316,949 (Bull et al.), U.S. Pat. No. 5,483,819 (Barmore et al.), and U.S. Pat. No. 5,583,047 (Blinka et al.) , all incorporated by reference herein in their entirety. Low oxygen transmission imaging system (LOTIS) testing was used based on its speed and the ability of the system to mimic real package hydration conditions. The objective of this evaluation was to obtain a relative measure of the oxygen barrier properties of each of the materials, under actual use conditions, to determine the effect of partial hydration on each formulation.




The films are identified in Table 6. Comparative Examples 9 and 10 were made by conventional tubular coextrusion as blown films. The remaining films were made by tubular cast coextrusion.













TABLE 6









Example




Structure






























 4




70% PO8




ADH6




NY3




aNY1




NY3




ADH6




70% PO8







30% PO4









30% PO4







1.38




0.38




0.44




1.10




0.44




0.38




1.38






 5




70% PO6




ADH6




80% NY3




aNY1




80% NY3




ADH6




70% PO6







30% PO4





20% aNY1





20% aNY1





30% PO4







1.38




0.38




0.71




0.55




0.71




0.38




1.38






Comp.




70% PO6




ADH6




80% NY3




EVOH2




80% NY3




ADH6




70% PO6






 9




30% PO4





20% aNY1





20% aNY1





30% PO4







1.38




0.38




0.71




0.55




0.71




0.38




1.38






Comp.




70% PO6




ADH6




80% NY3




EVOH2




80% NY3




ADH6




70% PO6






10




30% PO4





20% aNY1





20% aNY1





30% PO4







0.87




0.25




0.35




0.56




0.35




0.25




0.87






Comp.




70% PO8




ADH4




ANY1




EVOH2




aNY1




ADH4




70% PO8






11




30% PO4









30% PO4







1.65




0.38




0.44




0.55




0.44




0.39




1.65






Comp.




70% PO8




ADH6




NY3




60%




NY3




ADH6




70% PO8






12




30% PO4






aNY1






30% PO4










40%










EVOH2







1.38




0.38




0.44




1.10




0.44




0.38




1.38






Comp.




70% PO8




ADH6




NY3




EVOH2




NY3




ADH6




70% PO8






13




30% PO4









30% PO4







1.59




0.37




0.72




0.55




0.71




0.37




1.19






Comp.




70% PO8




ADH4




ANY1




ADH4




70% PO8






14




30% PO4







30% PO4







1.81




0.39




1.10




0.39




1.81














The evaluation was conducted as follows. A 5″×8″ piece of LOTIS paper was placed on a 10″×10″ glass plate, a thin bead of vacuum grease was placed just off the edge of the paper, and a 7″×10″ specimen of sample material was positioned on top of the glass plate such that it covered both the paper and the bead of vacuum grease. The “plated” sample then was put in a pouch made by Cryovac, Inc. under the commercial designation P640B. This material is a multilayer laminate having the general construction:




LLDPE/LLDPE+LDPE/LLDPE/adhesive/saran coated nylon 6.




This pouch was evacuated (60 second cycle) and sealed on a Koch X200™ tabletop vacuum chamber packaging machine. The plates were photo-reduced under fluorescent light, held in the over-pouch in the dark overnight, and photo-reduced again the next morning prior to beginning the actual oxygen transmission testing. Estimated oxygen transmission rates (OTR's) were determined using the methodology described in U.S. Pat. No. 5,316,949 (Bull et al.), U.S. Pat. No. 5,483,819 (Barmore et al.), and U.S. Pat. No. 5,583,047 (Blinka et al.). Samples were checked on Days 2, 12, and 26 after plating to simulate product hydration effects on the test materials during approximately the first month of storage.




Additional samples of Example 5, and Comp. Examples 9 and 12, were plated. These materials were stored underneath water-filled pouches of the same materials. These storage conditions were designed to simulate the hydration that the middle packages of column-stacked product in a case would experience under actual conditions.




All of the materials were subjected to conditions simulating hydration due to the packaged product (water activity ≈0.930) with normal external humidity levels (duplicated hydrating conditions of upper side of top package in a case). Comp. Ex 12, Comp. Ex. 9, and Example 5 also were tested simulating hydration due to packaged product plus hydration due to contact with another package (duplicated hydrating conditions of the middle package in a column stack in a case).




All of the materials exposed to normal external humidity levels had estimated oxygen transmission rates of between 6 and 10 cc/m


2


/24 hrs. after two days of hydration. After 12 days of hydration, Comp. Examples 9, 10, and 11 had estimated oxygen transmission rates less than 3.0, while all other materials had estimated oxygen transmission rates greater than 15.0. Comp. Examples 9 and 11 had estimated oxygen transmission rates less than 7.0 after 26 days of hydration, while all other materials tested had estimated oxygen transmission rates greater than 13 at the same time period. Twenty-six days was thought to be adequate to establish a hydration equilibrium in the materials under the test conditions.




The three materials tested under extreme hydrating conditions showed dramatically different estimated oxygen transmission rates after two days of hydration—6.7 cc (Comp. Example 12), less than 1 cc (Comp. Example 9), and 24.4 cc (Example 5), but these differences decreased as storage time, and, therefore, hydration time increased. After 43 days of hydration the estimated oxygen transmission rates of all three of these materials were practically equal: in the mid-40 cc range.




The results in Table 7 show little difference in the estimated oxygen transmission rates of the materials after two days of simulated product contact, with only Example 4 having a considerably higher oxygen transmission rate than the other materials. By Day 12 hydration effects were clearly being seen with Examples 4 and 5, and Comp. Examples 12 and 13 having appreciably higher oxygen transmission rates than the other three test materials. After 26 days of hydration Comp. Examples 9 and 11 still had oxygen transmission rates estimated as being equal to, or slightly lower than, that of the control after two days of hydration. The cast films do not, as a group, stand out from the blown films, either as being better or as being worse.




Table 8 shows the results for the selected materials that were tested under the extreme hydration conditions (plated samples held under water-filled pouches). This table shows marked differences between the materials during the first couple of weeks of storage, but an apparent equilibration of OTR's at the same point as storage time increased.




The results of these tests indicate that under conditions of a very high moisture moderate moisture gradient there are differences in ultimate oxygen transmission rates of the various materials tested; while under conditions of a very high moisture very high moisture system (practically no moisture gradient) the ultimate oxygen transmission rates may be essentially the same.












TABLE 7











Estimated OTR values for several vertical form-fill-seal






materials subjected to conditions simulating product-induced






hydration with normal external humidity levels.













Hydration Time (days)
















Example




2




12




26




















4




10.1




31.8




42.4







5




8.4




20.0




26.5







Comp. 9




<7.0*




2.6




6.8







Comp. 10




7.0




<1




13.8







Comp. 11




7.0




<1




5.9







Comp. 12




7.2




16.3




19.9







Comp. 13




7.0




13.4




26.2























TABLE 8











Estimated OTR values for several vertical form-fill-seal materials






subjected to conditions simulating product-induced hydration with






package-to-package contact.














Hydration Time (days)


















Example




2




11




26




43





















5




24.4




33.2




47.2




43.1







Comp. 9




<1




<1




34.5




43.6







Comp. 12




6.7




33.7




54.5




46.4















The physical properties of film structures of the invention produced for hot fill stretch resistance film development were determined. These film structures were made using a blown process, and/or were made with amorphous polyamide. Both the blown process and the addition of amorphous polyamide were demonstrated to impart hot fill stretch resistance to films used in vertical form/fill/seal applications, thereby improving pouch weight control.




The results are summarized in Tables 9 and 10. General trends noted from the results include a decrease in room temperature elongation when substituting amorphous polyamide for EVOH as well as when the EVOH layer is thickened; and an increase in modulus when using the blown process and when using amorphous polyamide instead of EVOH. The hot elongation results provide a measure of the hot fill stretch resistance of these films for reference and for comparison to applications test results. The tear propagation and instrumented impact resistance of the different structures varied and should be considered during qualification of a stretch resistant film with respect to easy-openability and abuse resistance. “L” refers to longitudinal direction; “T” to transverse direction; “Dir.” refers to direction.

















TABLE 9













Example 4




Example 5




Comp. 9




Comp. 10




















L




T




L




T




L




T




L




T























T & E:














Tensile at




3100




3130




3490




3440




3390




3470




3560




3600






Yield (psi)


1








Elong. at




16.1




16.2




16.7




16.5




16.6




16.7




16.4




15.9






Yield (%)


1








Tensile at




5110




5240




5170




5110




6790




7160




6420




6280






Break (psi)


1








Elong. At




321




331




322




327




495




520




440




466






Break (%)


1








Elastic




81.2




82.4




85.6




85.6




90.2




95.9




112.4




114.5






Modulus






(psi ×






1000)


1








Thickness




5.25




5.26




5.46




5.30




5.37




5.11




3.34




3.27






(mil)






Hot Elong.


8


:






Stress at




745




693




426




522




384




401




432




453






5% Strain






Stress at




817




767




556




635




582




604




625




643






10% Strain






Stress at




837




784




609




676




651




672




695




703






15% Strain






Stress at




843




797




643




704




680




702




720




717






25% Strain






Thickness




5.07




5.19




5.56




5.32




5.40




5.51




3.31




3.31






(mil)






Tear Prop.


2


:






Max Load




117




123




146




149




477




488




148




187






(g)






Load at




90




97




112




118




448




474




120




150






Break (g)






Thickness




5.31




5.52




5.57




5.69




5.46




5.41




3.46




3.47






(mil)















Instr. Impact


3


:










Peak Load




112




121




121




76






(N)






Gradient




10.4




13.2




12.9




8.4






(N/mm)






Energy to




0.89




0.88




1.04




0.51






Break (J)






Thickness




5.30




5.58




5.50




3.48






(mil)






Optics:






Total




93.0




92.9




92.6




93.1






Trans-






mission






(%)


4








Haze (%)


5






8.1




27.4




27.7




19.8






Clarity (%)


6






21.0




16.4




20.5




26.4






Gloss




80




52




52




56






(45°)


7








Thickness




5.24




5.48




5.42




3.43






(mil)


























TABLE 10













Comp. 12




Comp. 13




Comp. 14


















L




T




L




T




L




T





















T & E:












Tensile at




2630




2560




2790




2740




3260




3250






Yield (psi)






Elong. At




16.3




15.8




16.5




16.7




15.6




15.3






Yield (%)






Tensile at




4910




4610




8360




7740




4270




4250






Break (psi)






Elong. At




375




342




545




518




264




261






Break (%)






Elastic




70.0




72.3




69.8




68.6




98.1




97.5






Modulus (psi ×






1000)






Thickness




5.70




5.41




5.78




5.57




5.11




5.12






(mil)






Hot Elong.:






Stress at 5%




369




392














767




795






Strain






Stress at




509




526














674




694






10% Strain






Stress at




559




570














664




681






15% Strain






Stress at




591




603














664




679






25% Strain






Thickness




5.36




5.20














5.10




4.97






(mil)






Tear Prop.:






Max. Load




204




224




429




421




1466




1435






(g)






Load at




157




194














1076




1027






Break (g)






Thickness




5.62




5.39




5.48




5.53




5.22




5.28






(mil)














Instrumented









Impact






Peak Load




71




153




123






(N)






Gradient




10.6




10.6




9.3






(N/mm)






Energy to




0.44




1.24




1.11






Break (J)






Thickness




5.53




5.67




5.25






(mil)






Optics:






Total Trans-




88.8




93.4




92.6






mission (%)






Haze (%)




28.2




5.5




28.9






Clarity (%)




0.9




23.9




20.8






Gloss (45°)




66




82




52






Thickness




5.82




5.59




5.13






(mil)














Additional films were tested. The results are summarized in Table 11 below. General trends noted from the results include seal strengths improved over most of the comparative examples on a per mil basis. Comparative Examples 15 and 16 are identified in Table 12 below.












TABLE 11











Physical Property Data



















Property




Dir.




Ex. 1




Ex. 3




Comp. 1




Comp. 2




Comp. 5




Comp. 15




Comp. 16






















Gauge





4




3




4




3.5




4.5




15




3.5






(mils)






Modulus




MD




149100




101500




167900




68000




73600




127800




96900






(psi)







TD




142100




106000




175000




67200




74100




122800




78700






Ultimate




MD




7000




5400




8000




5300




5300




6300




5600






Tensile






(psi)







TD




6700




5400




7700




4700




5100




6200




4700






Ultimate




MD




400




430




370




590




630




400




540






Elongation






(%)







TD




390




460




370




530




610




430




480






Energy




MD




42




37




40




39




40




41




42






To Break






(lbs-in/






mil)







TD




40




39




40




33




39




45




33






Tear




MD




66




108




74






na






Resist-






Ance






(gm/ mil)







TD




78




112




82






na






Seal




MD




21.3




15




26




10.3




11.9




64.8




10.2






Strength




Peel






(lbs/






in)























TABLE 12









Example




Structure































Comp.




96% aNY1




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




48% PO8






15




 2% MB2





20% aNY1





20% aNY1





10% PO10




48% PO7







 2% MB1










 4% MB4







1.95




2.85




0.98




3.0




0.97




1.2




2.85




1.2






Comp.




96% NY2




ADH9




80% NY1




EVOH2




80% NY1




ADH6




90% PO8




88% PO08






16




 2% MB2





20% aNY1





20% aNY1





10% PO10




10% PO10







 2% MB1










 2% MB3







0.46




0.87




0.23




0.28




0.23




0.28




0.87




0.28














The heat seal results were measured as a maximum force/linear inch of seal width, required to separate a heat seal of two plies of the film sample sealed to each other at a temperature of 370° F., for 0.5 seconds dwell time (3 seconds for the film of Comp. 15), cut in the machine direction. An Instron™ tester was used, with a 2 inch jaw separation, at a crosshead speed of 10 inches/minute.




Microwaveability studies were conducted using the Example 1 film structure. This structure lends itself to thermoforming with the property of reduced memory of the original shape of the material before it was formed.




Testing was also done on semi-rigid thermoformed trays containing PVC, and semi-rigid thermoformed trays containing amorphous polyester The results achieved with this product demonstrate that there is a significant difference from, and improvement over, the results experienced with semi-rigid materials made with PVC (poly(vinyl chloride)) or A-Pet (amorphous polyester).




The material of Example 1 retained the formed shape overall maintaining sides and a bottom while both the PVC and A-Pet trays lost the formed shape and the bottom would actually rise above the sides in some of the tests.




The ability of the film of the present invention to hold the formed shape during reheating of the product is a definite advantage and adds to the unique properties of the product.




Results are shown in Tables 13 to 15.




With respect to the data in Tables 13 to 15, note that:




All packages were filled with 250 ml of water.




“Form. Temp.” is the forming temperature, i.e. the temperature at which the film was formed on a Multivacrm R7000 using 5×7 inch , 4 pocket tooling.




There were two forming depths used (1¼″ and 2⅛″) indicated by the initial volume held of approximately 650 ml and 1150 ml respectively.




The plug system on the Multivac™ R7000, available on this system to assist in forming the film and relaxing the memory, was not used in any of the samples shown in the Tables.




Cook Time: Time set on the microwave at full power. If more than one time is listed then microwave was set for subsequent times on the same package.




Boil Time: For the samples cooked for 5 minutes the products began boiling around the two minute mark and were considered to reach ˜212° F. and held for two minutes at that temperature.




Cook Temperature: This is the temperature of the water as measured by inserting a probe of a Dickson™ 2500 Thermocouple Thermometer into the water after the microwave was shut off and the door was opened.




Vent and Open: A corner of the top was peeled back for the vented packages, whereas the top was completely removed on the open top packages.




Initial Volume: This is the Kg. of water held when the pocket was completely filled before cooking.




Final Volume: This is the Kg. of water held after the cook cycle with the pocket completely filled with water. These measurements were taken with the tray sitting on a scale as opposed to hanging in a form.




Percent loss: The amount of volume loss from the initial measurement to the measurement taken after the cook cycle.




Thus, film of the invention lends itself very well to microwaving, and forms easily in a thermoforming machine, and then retains its shape very well when heated to 200° F. in a microwave.




The PVC and A-Pet trays were formed at 115° and 125° C. respectively.




An attempt was made to establish a time that the material would last in the microwave, and so the test was started with a 2 minute microwave cycle. This proved to be disastrous for the PVC package with the distortion of the tray at about 90%, while the distortion of the A-Pet tray was at about 65%.












TABLE 13











Microwave Data: Example 1














FORMING




COOK




COOK




VOLUME
















TEMP




TIME




TEMP.




Initial




Final







(° C.)




(min:sec)




(° F.)




Volume




Volume




% LOSS



















100




2:00




171




1.145




0.96




16.2






120




2:00




176




1.155




0.895




22.6






120




2:00




184




1.085




0.885




18.5






130




2:00




177




1.2




0.945




21.3






130




2:00




181




1.22




1.015




16.9






140




2:00




175




0.685




0.655




4.4






140




2:00




178




1.125




0.955




15.2






140




2:00




184




1.27




1.075




15.4






140




2:00




197




0.705




0.605




14






150




2:00




179




0.735




0.68




7.5






150




2:00




180




0.66




0.635




3.8






160




2:00




185




0.68




0.64




5.9






160




2:00




186




0.68




0.68




0






100




5:00




212




1.055




0.515




51.2






120




5:00




212




1.085




0.585




46.1






130




5:00




212




1.115




0.73




34.6






140




5:00




212




0.695




0.455




34.5






140




5:00




212




1.225




0.76




38






150




5:00




212




0.68




0.415




39






160




5:00




212




0.65




0.485




25.4











Notes:










Example 1 is a totally coextruded structure, i.e. not adhesively laminated.










Example 1 has a core consisting essentially of amorphous polyamide. This core layer makes up 20% of the film structure's total thickness.





















TABLE 14











Microwave Data: Control APET film














FORM




COOK




COOK




VOLUME

















TEMP




TIME




TEMP.




Initial




Final




%







(° C.)




(min:sec)




(° F.)




Vol.




Vol.




LOSS




Comments




















130




1:00




117




0.69




0.365




48.2




Sides down to ⅓












original height






115




1:00




126




0.69




0.145




79




No gross change












of shape






130




1:00




162




nd




Nd




Nd






115




1:00




177




nd




Nd




Nd




Water ran out












side






130




1:00




190




nd




Nd




Nd






115




1:00




198




nd




Nd




Nd




Both sides down






130




2:00




167




0.73




0.59 




19.2






115




2:00




170




0.74




0.52 




29.8




Sides down ½






115




5:00




205




0.72




0   




100




Sides down at












2:00 minutes






130




5:00




209




0.75




0.235




68.7




Sides down to ⅓






















TABLE 15











Microwave Data: Control PVC film














FORM




COOK




COOK




VOLUME

















TEMP




TIME




TEMP.




Initial




Final




%







(° C.)




(min:sec)




(° F.)




Vol.




Vol.




LOSS




Comments









130




1:00




116




0.74 




0.285




nd







115




1:00




120




Nd




Nd




nd




Slightly deformed






130




1:00




160




Nd




Nd




  61.5






115




1:00




165




Nd




Nd




nd




No Change






115




1:00




187




0.715




0   




100




Sides down 100%






130




1:00




188




nd




Nd




nd






130




5:00




205




0.755




0




100




Sides down 100%












at 3:25 minutes.






115




5:00




210




0.76 




0




100




No sides left











Notes:










The PVC control is a 14 mil thick PVC film adhesively laminated to a 2 mil blown sealant having the structure:










Sealant/adhesive/Nylon/EVOH/Nylon/adhesive/bulk










The total gauge of the PVC control was thus 16 mil.










The “APET” control is 11 mil amorphous polyester film adhesively laminated to 2 mil P363. Total gauge = 13 mil.










nd = not determined













A film of the invention, and comparative films, were evaluated for their moisture vapor transmission rate (MVTR), and their oxygen transmission rate (OTR) under wet (100% RH) and dry (0% RH) conditions, where “RH” is relative humidity. The results are shown in Table 17. WVTR was measured according to ASTM F 1249-90. OTR was measured according to ASTM D 3985-95.




The films not already identified hereinabove are identified in Table 16.













TABLE 16









Example




Structure






























Comp.




70% PO8




ADH6




NY3




ADH6




NY3




ADH6




70% PO8






17




30% PO4









30% PO4







1.25




0.35




0.65




0.50




0.65




0.35




1.25






Comp.




70% PO8




ADH6




NY3




ADH6




NY3




ADH6




70% PO8






18




30% PO4









30% PO4







1.25




0.35




0.65




0.50




0.65




0.35




1.25






Comp.




70% PO8




ADH6




NY3




EVOH1




NY3




ADH6




70% PO8






19




30% PO4









30% PO4







1.38




0.38




0.71




0.55




0.71




0.38




1.38

























TABLE 17










MVTR









(grams/100 in


2


-




OTR (0% RH)




OTR (100% RH)






Example




day-atm.)




(cc/m


2


-day-atm.)




(cc/m


2


-day-atm.)


























5




0.23




27.5




16.9






Comp. 13




0.31




1.17




70.6






Comp. 17




0.35




37.2




129






Comp. 18




0.34




53.0




177






Comp. 19




0.27




3.26




62.6














Additional OTR testing was done on several films. For each case, the film was tested on a Mocon™ analyzer with the humidity at 100% RH on the N


2


side of the sample, and 50% RH on the O


2


side of the sample.




The films not already identified hereinabove are identified in Table 18. Comp. 22 is a 5.5 mil thick blown film with a core layer of a polymeric adhesive, a first intermediate layer, on a first side of the core layer, of a nylon 6, and a second intermediate layer, on the second side of the core layer, of an EVOH. Thus, Comp. 22 is asymmetric in construction. Table 19 shows this material tested in each of the two possible orientations: the EVOH “side” of the film oriented toward the 100% RH (N2) side of the sample (“Orient


1


” in the table), and the EVOH “side” of the film oriented toward the 50% RH (O


2


) side of the sample (“Orient


2


” in the table).













TABLE 18









Example




Structure






























Comp.




70% PO6




ADH6




NY3




EVOH2




NY3




ADH6




70% PO6






20




30% PO4









30% PO4







1.25




0.35




0.65




0.50




0.65




0.35




1.25






Comp.




70% PO6




ADH6




NY3




EVOH2




NY3




ADR6




70% PO6






21




30% PO4









30% PO4







1.12




0.32




0.58




0.46




0.58




0.32




1.12






Comp.




LLDPE




Adhe-




Nylon 6




EVOH1




Nylon 6




Adhe-




LLDPE






22





sive







sive

























TABLE 19












OTR (50% RH/100% RH)







Example




(cc/m


2


-day-atm.)



























5




10.61







Comp. 12




6.14







Comp. 13




6.49







Comp. 20




<0.2







Comp. 21




2.01







Comp. 22




3.08







(Orient


1


)







Comp. 22




1.76







(Orient


2


)















Films of the present invention are preferably made by tubular blown or cast coextrusion.




Films of the present invention are preferably not heat shrinkable, since this property would negate the dimensional stability at elevated temperatures which is required for the primary intended end-use applications, i.e. for vertical form/fill/seal uses. However, for other applications where dimensional stability at elevated temperatures is not required or desired, films can be stretch oriented by convention orientation processes well known in the art, such as the trapped bubble or tenter frame processes, to render the material heat shrinkable. In such cases, films of the present invention can optionally be crosslinked by irradiation, or chemically.




Internal fitments, such as the Asept™ fitment distributed in the U.S. by the assignee of the present application, and disclosed in U.S. Pat. No. 4,603,793 (Stern), can be optionally sealed to the interior surface of a pouch wall of a pouch made from the film of the present invention.




In general, the multilayer film used in the present invention can have any total thickness desired, so long as the film provides the desired properties for the particular packaging operation in which the film is used. Preferably, the film used in the present invention has a total thickness (i.e., a combined thickness of all layers), of from about 0.5 to 10 mils (1 mil equals 0.001 inch); more preferably, from about 1 to 6 mils; and still more preferably, from 3.5 to 5.5 mils.




The polymer components used to fabricate multilayer films according to the present invention can also contain appropriate amounts of other additives normally included in such compositions. These include slip agents, antioxidants, fillers, dyes, pigments, radiation stabilizers, antistatic agents, elastomers, and other additives known to those of skill in the art of packaging films.




It is to be understood that variations of the present invention can be made without departing from the scope of the invention, which is not limited to the specific embodiments and examples disclosed herein, but extends to the claims presented below.




The invention has described herein primarily with reference to vertical form/fill/seal (VFFS) packaging of flowable products such as water, milk, juices, sauces, soups, toppings, highly spiced products including ketchup and salsa, and the like, as well as non-flowable products such as bulk cheese, such as shredded cheese, and individual quick frozen (IQF) applications such as chopped meat for fahitas. Such applications benefit from reduced stretching of horizontal (transverse) seals which are still hot just after the sealing step. In conventional packaging materials, these hot seals sometimes undesirably stretch or elongate as a result of the weight of the product applying a load to the package. This phenomenon can adversely affect seal integrity, and package dimensional uniformity. The present invention demonstrates improvements in resistance to stretching of hot seals in VFFS applications. Conventional VFFS packages can also experience some overall package distortion or elongation as a result of the weight of the product, dependent on such variables as the nature, weight, and temperature of the product, and the type of packaging material. The present invention demonstrates improved resistance to stretching of the overall package. This dimensional stability results in more predictable packaging sizing and more uniform package weights, an advantage for the food processor. Also, good wet (high relative humidity) oxygen barrier, compared to conventional films containing EVOH, and good easy-tear (low tear propagation) is also obtained. Highly spiced products, e.g. the ketchup and salsa mentioned earlier, benefit from the aroma barrier properties of films of the present invention.




High seal strengths are obtained by the films of the present invention. These are further disclosed in Table 10 below.




The present invention also offers good aroma barrier in connection with the packaging of beverages, essential oils, fragrance, herbicides, pesticides, fertilizers, cosmetics, etc.




The high stiffness (high tensile modulus) of the present film makes it very suitable for end-uses where good machinability, i.e. ability to track well through a machine, especially a high-speed machine, is desirable.




The present invention is also useful in horizontal form/fill/seal (HFFS) end-uses, e.g. in packaging block cheese. In such uses, an ethylene/vinyl acetate copolymer sealant layer is a preferred outer layer or outer layers. An example of a film of the present invention especially useful in HFFS applications is shown as Example 6 in Table 20.




Also, films of the present invention can be used to make semi-rigid trays, and to make thermoformable film. The latter can be made with thicknesses of 4 to 30 mils, and possibly higher, thermoformable at temperatures of 80 to 180° C. These films show better stiffness (higher tensile modulus) than laminates of comparable gauge containing PVC. Non-forming webs, i.e. top webs to be used as lidstock with a trayed package, can also be made from films of the present invention. Products such as hot dogs can be packaged in a tray or other support, with films of the present invention as a non-forming top web.




The present film can be beneficially used to make a bottom web for vacuum skin packages (VSP). In non-forming end-uses, a preferred formulation includes a first outer layer (layer farthest away from the product to be packaged) comprising a nylon 6 or other semicrystalline polyamide, and a second outer layer (layer closest to the product to be packaged) comprising a polyolefin such as EAO, polypropylene, or propylene copolymer. The outer layer supplies abuse resistance; the inner layer supplies heat sealability. An example of a film of the present invention especially useful in VSP semi-rigid bottom web applications is shown as Example 7 in Table 20.













TABLE 20









Example




Structure































6




96% NY2




ADH9




80% NY1




aNY1




80% NY1




ADH6




90% PO8




PO14







 2% MB2





20% aNY1





20%





10%







 2% MB1







aNY1





PO10







0.40




0.72




0.19




0.30




0.19




0.24




0.72




0.24






7




96% NY2




ADH9




85% NY3




ADH




85% NY3




ADH6




90% PO2




50% PO10







 2% MB2





15% aNY1





15%





10%




35% PO15







 2% MB1






6




aNY1





PO10




15% PO1







1.04




1.92




0.52




0.80




0.52




0.64




1.92




0.64














A major advantage of the present invention is that the physical property of high stiffness, i.e. high tensile modulus, conventionally supplied by laminates having a coextruded substrate and, glued thereto, a biaxially oriented nylon or polyester film, can now be provided by a fully coextruded film without the need for additional discrete films to be glued thereto.




For stand-up pouches, high stiffness offered by the present films provides better package presentation on retail shelves. Aroma, oxygen, and ultraviolet barrier properties are also benefits of the present film useful in stand-up pouch applications.




The present invention is also useful in high strength industrial applications, e.g. as dunnage bags.




Films of the invention can be surface printed or trapped printed; can be symmetric or asymmetric in construction; and can be used to produce pouches with lap seals or fin seals. For example, the present invention can be used to make symmetric, seven layer (A/B/C/D/C/B/A) structures on VFFS packaging equipment such as the Onpack™ equipment supplied by Cryovac, Inc. Pouches thus made will typically have longitudinal lap seals. In contrast, the present invention can also be used to make asymmetric, seven layer (A/B/C/D/C/B/E) structures on VFFS packaging equipment such as the Ultimate™ equipment supplied by Hayssen. Pouches thus made will typically have longitudinal fin seals.




Films of the present invention also exhibit good deadfold properties at higher thicknesses. By “deadfold” herein is meant a fold that does not spontaneously unfold; a crease.



Claims
  • 1. A multilayer film comprising:a) a core layer consisting essentially of an amorphous polyamide; b) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; c) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and d) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer; wherein the film has a total thickness of between 0.5 and 10 mils; andwherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180° F.
  • 2. The film of claim 1 wherein the amorphous polyamide of the core layer is selected from the group consisting of nylon 6I/6T, nylon 6,6/6,9/6I, and nylon 6,6/610/MXD-6.
  • 3. The film of claim 1 wherein the semicrystalline polyamide is selected from the group consisting of nylon 6, nylon 9, nylon 11, nylon 12, nylon 66, nylon 69, nylon 610, nylon 612, nylon 6/12, nylon 6/69, nylon 66/610, nylon 6/66, nylon 66/6, nylon 12T, nylon 6T, and nylon 666.
  • 4. The film of claim 1 wherein the intermediate layers each comprise a blend of a semicrystalline polyamide and an amorphous polyamide.
  • 5. The film of claim 1 wherein the polymeric adhesive layers each comprise a polymeric adhesive selected from the group consisting of anhydride grafted ethylene/1-butene copolymer, anhydride grafted ethylene/1-hexene copolymer, and anhydride grafted ethylene/1-octene copolymer.
  • 6. The film of claim 1 wherein the first outer layer comprises an ethylene/alpha-olefin copolymer having a density of between 0.916 and 0.945 grams per cubic centimeter.
  • 7. The film of claim 1 wherein the first outer layer comprises a propylene/ethylene copolymer.
  • 8. The film of claim 1 wherein the first outer layer comprises a single site-catalyzed ethylene/alpha-olefin copolymer.
  • 9. The film of claim 1 wherein the film is not oriented.
  • 10. A method of packaging a food product comprising:a) providing a rollstock film, the film comprising i) a core layer consisting essentially of an amorphous polyamide; ii) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; iii) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and iv) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer, wherein the film has a total thickness of between 0.5 and 10 mils; and wherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180° F.; b) forming the film into a tube in a vertical/form/fill/seal process; c) filling the tube with a food product; and d) closing the tube to form a sealed pouch containing the food product.
  • 11. A package comprises:a) a flowable food product; and b) a pouch containing the food product, the pouch made from a film comprising i) a core layer consisting essentially of an amorphous polyamide; ii) two intermediate layers, disposed on opposite surfaces of the core layer, comprising a semicrystalline polyamide; iii) two adhesive layers, each disposed on a surface of the respective intermediate layer, comprising a polymeric adhesive; and iv) two outer layers, each disposed on a surface of a respective adhesive layer, comprising a material selected from the group consisting of amorphous polyamide, semicrystalline polyamide, ethylene/alpha olefin copolymer, propylene homopolymer, and propylene/alpha olefin copolymer, wherein the film has a total thickness of between 0.5 and 10 mils; and wherein the film exhibits a free shrink of less than 5% in the longitudinal direction, and less than 5% in the transverse direction, at 180° F.
US Referenced Citations (78)
Number Name Date Kind
2252555 Carothers Aug 1941 A
2733230 Ufer Jan 1956 A
2893980 Ham et al. Jul 1959 A
3150117 Gabler Sep 1964 A
3240732 Ham et al. Mar 1966 A
3347828 Stephens et al. Oct 1967 A
3376270 Ridgway Apr 1968 A
3386964 Twilley Jun 1968 A
3489724 Iwakura et al. Jan 1970 A
3573260 Morello Mar 1971 A
3592952 Fang Jul 1971 A
3597400 Kashiro et al. Aug 1971 A
3642941 Schneider et al. Feb 1972 A
3646156 Schneider et al. Feb 1972 A
3650999 Martins et al. Mar 1972 A
3661832 Stephens May 1972 A
3673277 Schmitt et al. Jun 1972 A
3794625 Anderson et al. Feb 1974 A
3875129 Herwig et al. Apr 1975 A
3922468 Burke, Jr. et al. Nov 1975 A
3962524 Miyamoto et al. Jun 1976 A
3968071 Miyamoto et al. Jul 1976 A
3974234 Brinkmann et al. Aug 1976 A
3979540 Moffett Sep 1976 A
4016140 Morello Apr 1977 A
4018746 Brinkmann et al. Apr 1977 A
4053682 Donermeyer Oct 1977 A
4098860 Etou et al. Jul 1978 A
4100223 Meyer et al. Jul 1978 A
4133802 Hachiboshi et al. Jan 1979 A
4167505 Dunkelberger Sep 1979 A
4173290 Kobayashi et al. Nov 1979 A
4224214 Chen Sep 1980 A
4232145 Schmid et al. Nov 1980 A
4254169 Schroeder Mar 1981 A
4309528 Keske et al. Jan 1982 A
4313868 Hanson Feb 1982 A
4340697 Aya et al. Jul 1982 A
4357376 Nattinger et al. Nov 1982 A
4369305 Pagilagan Jan 1983 A
4381371 Nielinger et al. Apr 1983 A
4398642 Okudaira et al. Aug 1983 A
4404317 Epstein et al. Sep 1983 A
4410661 Epstein et al. Oct 1983 A
4442254 Aratani Apr 1984 A
4455417 Vanderkooi, Jr. et al. Jun 1984 A
4457960 Newsome Jul 1984 A
4461808 Mollison Jul 1984 A
4467084 Kitagawa et al. Aug 1984 A
4482695 Barbee et al. Nov 1984 A
4486507 Schumacher Dec 1984 A
4500668 Shimizu et al. Feb 1985 A
4501879 Barbee et al. Feb 1985 A
4508769 Vanderbooi, Jr. et al. Apr 1985 A
4515924 Brooks et al. May 1985 A
4542047 Donermeyer et al. Sep 1985 A
4640852 Ossian Feb 1987 A
4695491 Kondo et al. Sep 1987 A
H469 Deak May 1988 H
4746562 Fant May 1988 A
4767651 Starczewski et al. Aug 1988 A
4788249 Maresca et al. Nov 1988 A
4800129 Deak Jan 1989 A
4818592 Ossian Apr 1989 A
4826955 Akkapeddi et al. May 1989 A
4911963 Lustig et al. Mar 1990 A
5006384 Genske Apr 1991 A
5039565 Deyrup Aug 1991 A
5053259 Vicik Oct 1991 A
5110855 Blatz May 1992 A
5139805 Tada et al. Aug 1992 A
5208082 Chou May 1993 A
5482771 Shah Jan 1996 A
5491009 Bekele Feb 1996 A
5707750 Degrassi et al. Jan 1998 A
5750262 Gasse et al. May 1998 A
6068933 Shepard et al. May 2000 A
6149993 Parks et al. Nov 2000 A
Foreign Referenced Citations (14)
Number Date Country
B-2168595 Sep 1997 AU
2172019 Sep 1996 CA
2172019 Sep 1996 CA
0 227 053 Dec 1986 EP
287839 Oct 1988 EP
465681 Jan 1992 EP
0465681 Jan 1992 EP
465931 Jan 1992 EP
0465931 Jan 1992 EP
2 471 399 Jun 1981 FR
1049987 Nov 1965 GB
1250877 Oct 1971 GB
22263 Nov 1987 NZ
WO 9828132 Jul 1998 WO
Non-Patent Literature Citations (19)
Entry
English-language abstract of 2,471,399 (France); Derwent 003187586.
Polymer Modification; Modified Nylons, DuPont Aust., Melb 61 35212676, Jul. 12, 1990; pp. 418-421.
Property And Extrusion Guide, SELAR PA 3426, SELAR PA—Nylon 6 Blends, Amorphous Nylon Resin; pp. 1-5.
Schotland Business Research, Inc., Proceedings of the Fifth Annual International Coextrusion Conference and Exhibition COEX'85,Oct. 9, 1985; Princeton, NJ, USA, p. 171-187.
Trigon Packaging Systems (NZ) Ltd., New Film Co-extrusion Developments in New Zealand and Australia; R.A. Cassey; p. 111-128.
EMS-Chemie AG, Zurich, Switzerland; Emser Industries; Engineering Resins; Grivory G21; 11 pages.
Mitsubishi Kasei Corporation; Novamid X21; 8 pages.
World Link, Partnering for your Global Packaging Solutions; DuPont Packaging; vol. 1, Spring 1998.
English language abstract, AU 9539110-A; “Multilayer film for use in packaging . . . ”; Jun. 20, 1996; W. R. Grace & Co.-Conn.
English language abstract, AU 9662133-A; “Multilayer film used as packaging film, . . . ”; Jun. 5, 1997; W. R. Grace & Co.-Conn.
English language abstract, EP-685510-A; “Biaxially oriented amide film for easily un-s . . . ”; Dec. 6, 1995; Unitika.
English language abstract, EP-755777-A; “Composite films with good deep draw and low . . . ”, Jan. 29, 1997; Wolff Walsrode AG.
English language abstract, EP-755778-A; “Barrier films of amide and olefin(s) that do . . . ”; Jan. 29, 1997; Wolff Walsrode AG.
English language abstract, DE 19504058-A; “Heat, oil and solvent resistant thermoplastic . . . ”; Aug. 14, 1996; BASF AG.
English language abstract, DE 19530952-A; “Sterilisation resistant, deep drawable, heat . . . ”; Feb. 27, 1997; Wolff Walsrode AG.
English language abstract, JP 08300583-A; “Multilayer film useful esp. for packing food . . . ”; Nov. 19, 1996; Sumitomo Bakelite Co.Ltd.
English language abstract, JP 08332703-A; “Multilayer film used for food packaging-com . . . ”; Dec. 17, 1996; Sumitomo Bakelite Co Ltd.
English language abstract, JP 9155997-A; “Laminated tube container for cosmetic, foods . . . ”; Jun. 17, 1997; Dainippon Printing Co Ltd.
English language abstract, WO 9612616-A; “Retortable, high oxygen barrier polymeric film . . . ”; May 2, 1996; Allied-Signal Inc.