WO1998023443A2 - Emballage muni d'un opercule a plusieurs couches comprenant une pellicule impermeable aux gaz adherant de façon pelable a une pellicule permeable aux gaz - Google Patents

Emballage muni d'un opercule a plusieurs couches comprenant une pellicule impermeable aux gaz adherant de façon pelable a une pellicule permeable aux gaz Download PDF

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Publication number
WO1998023443A2
WO1998023443A2 PCT/US1997/021501 US9721501W WO9823443A2 WO 1998023443 A2 WO1998023443 A2 WO 1998023443A2 US 9721501 W US9721501 W US 9721501W WO 9823443 A2 WO9823443 A2 WO 9823443A2
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WO
WIPO (PCT)
Prior art keywords
film
films
set forth
interface
package
Prior art date
Application number
PCT/US1997/021501
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English (en)
Other versions
WO1998023443A3 (fr
Inventor
Charles R. Barmore
Narender P. Luthra
Walter B. Mueller
Joseph E. Owensby
Original Assignee
Cryovac, Inc.
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Publication date
Application filed by Cryovac, Inc. filed Critical Cryovac, Inc.
Priority to AU53616/98A priority Critical patent/AU5361698A/en
Publication of WO1998023443A2 publication Critical patent/WO1998023443A2/fr
Publication of WO1998023443A3 publication Critical patent/WO1998023443A3/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/06—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material
    • B32B27/08—Layered products comprising a layer of synthetic resin as the main or only constituent of a layer, which is next to another layer of the same or of a different material of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/302—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising aromatic vinyl (co)polymers, e.g. styrenic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/306—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising vinyl acetate or vinyl alcohol (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/30—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers
    • B32B27/308—Layered products comprising a layer of synthetic resin comprising vinyl (co)polymers; comprising acrylic (co)polymers comprising acrylic (co)polymers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/06—Interconnection of layers permitting easy separation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D77/00—Packages formed by enclosing articles or materials in preformed containers, e.g. boxes, cartons, sacks or bags
    • B65D77/10—Container closures formed after filling
    • B65D77/20—Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers
    • B65D77/2024—Container closures formed after filling by applying separate lids or covers, i.e. flexible membrane or foil-like covers the cover being welded or adhered to the container
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/30—Properties of the layers or laminate having particular thermal properties
    • B32B2307/31—Heat sealable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/514—Oriented
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/724—Permeability to gases, adsorption
    • B32B2307/7242—Non-permeable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/70—Other properties
    • B32B2307/748—Releasability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2310/00—Treatment by energy or chemical effects
    • B32B2310/14—Corona, ionisation, electrical discharge, plasma treatment
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2323/00—Polyalkenes
    • B32B2323/04—Polyethylene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2325/00—Polymers of vinyl-aromatic compounds, e.g. polystyrene
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2331/00—Polyvinylesters
    • B32B2331/04—Polymers of vinyl acetate, e.g. PVA
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2333/00—Polymers of unsaturated acids or derivatives thereof
    • B32B2333/04—Polymers of esters
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2439/00—Containers; Receptacles
    • B32B2439/70—Food packaging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2577/00—Packages formed by enclosing articles or materials in preformed containers, e.g. boxes, cartons, sacks, bags
    • B65D2577/10—Container closures formed after filling
    • B65D2577/20—Container closures formed after filling by applying separate lids or covers
    • B65D2577/2075—Lines of weakness or apertures
    • B65D2577/2091—Lines of weakness or apertures in cover

Definitions

  • the present invention relates to packaging for products, such as food products, which are enclosed under certain environmental conditions in a support member having a lid which peelably delaminates (i.e., delaminates upon peeling) to expose a gas-permeable film, thereby causing a change in the environmental conditions within the package. More specifically, the invention relates to such packaging for fresh red meat products.
  • Fresh red meat presents a particular challenge to the concept of centralized processing and packaging due to its oxygen-sensitivity.
  • oxygen-sensitivity is manifested in the shelf- life and appearance (color) of a packaged meat product.
  • color For example, while a low-oxygen packaging environment generally increases the shelf-life of a packaged meat product (relative to meat products packaged in an environment having a higher oxygen content), red meat has a tendency to assume a purple color when packaged in the absence of oxygen or in an environment having a very low oxygen concentration, i.e., below about 5% oxygen. Unfortunately, such a purple color is undesirable to most consumers, and marketing efforts to teach the consumer about the acceptability of the purple color have been largely ineffective.
  • the meat would desirably be packaged, shipped, and stored in a low- oxygen environment for extended shelf-life, and then displayed for consumer sale in a relatively high-oxygen environment such that the meat is caused to "bloom" into a red color just before being placed in a retail display case.
  • the meat product is desirably contained in a package which protects it from microbial and other contamination.
  • the package in which the meat product is displayed for consumer sale is the same package in which the meat product is initially packaged and shipped from the central processing facility.
  • centralized butchering and packaging of fresh red meat presents a number of difficult packaging challenges.
  • a variety of packages have been developed in an effort to overcome the foregoing challenges.
  • One attempted solution is to use a dual-film cover or lid over a support member, such as an oxygen-barrier tray, which contains the meat product.
  • the support member generally includes a cavity, in which the product is contained, surrounded by a peripheral flange to which the lid is secured.
  • One film of the dual-film lid is relatively oxygen-impermeable, i.e., provides a substantial barrier to the passage of oxygen therethrough, and is removably positioned above a second film that is relatively oxygen-permeable, i.e., sufficiently pe ⁇ neable to the passage of oxygen to allow the packaged meat product to bloom.
  • the package may be shipped with the upper, impermeable film intact so that a low-oxygen environment may be maintained within the package during shipping. Then the impermeable film may be removed at the supermarket just prior to placing the package in a retail display case. Since the lower film is oxygen permeable, it allows the meat product to bloom in the presence of oxygen which enters the package from the ambient atmosphere.
  • Conventional dual-film packaging arrangements can employ either separate, discrete permeable and impermeable lids which are attached separately to the support member, or a single, peelable lid which may delaminate into permeable and impermeable films.
  • the permeable and impermeable lids are typically sealed to separate locations on the support member flange, with the pemieable lid being sealed to an inner periphery of the flange and the impermeable lid being sealed to an outer periphery of the flange, i.e., outboard of the flange area at which the permeable lid is sealed.
  • the primary difficulty m achieving consistent and reliable peelabihty in a single, peelable lid lies in the manner m which the pemieable and impermeable films are adhered to one another
  • Conventional mechanisms for bonding two films together generally include the use of heat and pressure (thermal lamination) and/or adhesives (adhesive lamination) to bond the two films While such mechanisms work well m producing non-peelable laminates (l e , laminates which are not intended to be subsequently delamrnated), they are not readily adaptable for producing peelable laminates
  • thermal and/or adhesive lamination techniques it is difficult to regulate the resultant bond-strength between the laminated films in such a manner that the films will peelably delaminate when subjected to a desired peel force
  • thermal and adhesive lamination is disadvantageous when the gas-permeable film is perforated because the heat from themial lamination can weld closed the perforations while adhesive can occlude the perforations
  • a dual-film package which combines the manufacturing simplicity of a package having a single, peelable lid with the consistent peelabihty of a package having separate permeable and impermeable lids SUMMARY OF THE INVENTION That need is met by the present invention which is directed to a package, comprising: a product support member having a cavity formed therein, a product being disposed with the cavity; a laminate heat-sealed to the support member and enclosing the product therein, the laminate comprising a first film in contact with the suppport member and a second film, at least one of the first and second films comprising a reactively-modified surface such that the laminate peelably delaminates at a peel force ranging from 0.001 pounds per inch to 2.5 pounds per inch.
  • the present invention is also directed to providing a method for making a package for a product comprising: providing a product support member containing a product therein; providing a first film; providing a second film; reactively modifying the surface of at least one of the first and second films to form a corona treated surface and pressing the first and second films togetlier. tliereby forming a laminate which is delaminatable at a peel force ranging from 0.001 pounds per inch to 2.5 pounds per inch; extending the laminate over the support member containing the product such that the first film is adjacent to the support member; and sealing the laminate to the support member.
  • the first film is preferably gas-permeable and, more preferably, perforated to provide for rapid penetration of atmospheric oxygen therethrough.
  • the first and/or second film surface is preferably reactively modified via corona treatment.
  • the present invention provides a reliable peel mechanism for a package having a dual-film lid which combines the manufacturing simplicity of a package having a single, peelable lid with the consistent peelabihty of a package having separate permeable and impermeable lids. Furthermore, the disadvantages of thermal and adhesive lamination are avoided. This is particularly important when the gas-permeable first film is perforated.
  • Fig. 1 is a perspective view of a package, according to the invention
  • Fig. 2 is a partial cross-sectional view of the package of Figure 1
  • Fig. 3 is a diagrammatic illustration of the process for making a laminate in accordance with the present invention.
  • film refers to a the ⁇ noplastic material, generally in sheet or web fo ⁇ n, having one or more layers of polymeric or other materials which may be bonded together by any suitable means well known in the art, e.g., coextrasion, lamination, etc.
  • a film can be a monolayer film (having only one layer), or a multilayer film (having two or more layers).
  • the te ⁇ n "laminate” refers to a composite structure of two or more films which are bonded together.
  • the component films of a laminate may be bonded togetlier by any suitable means such as, e.g., adhesive bonding, corona treatment, heat treatment, pressure treatment, etc., including combinations thereof.
  • Laminates in accordance with the present invention are formed by pressing together two or more films of which at least one has been corona treated.
  • the surface (or surfaces) of each of the films at which bonding occurs is refe ⁇ ed to herein as the “bonding surface.”
  • the plane or contour at which two films intersect is refe ⁇ ed to herein as an "interface.”
  • the te ⁇ n "layer” refers to a discrete film component which is coextensive with the film and has a substantially uniform composition. In a monolayer film, the "film” and “layer” would be one and the same.
  • reactive surface modification refers to chemically altering the surface of a film in order to incorporate reactive species onto such film surface, e.g., to provide the film surface with auto-adhesion functionality (i.e., rendering the surface capable of adhering to another surface without the need for an adhesive).
  • reactive surface modification include corona treatment, plasma (ionized gas) treatment, and flame treatment, with corona treatment being preferred.
  • the surface of a film which has been subjected to reactive surface modification is refe ⁇ ed to as a "modified surface” or, in the case of corona treatment, a "corona treated surface.”
  • gas-permeable refers to a film or film portion which admits at least about 1,000 cc of gas. such as oxygen, per square meter of film per 24 hour period at 1 atmosphere and at a temperature of 73 °F (at 0% relative humidity). More preferably, a gas- permeable film or film portion admits at least 5,000, even more preferably at least 10,000, such as at least 15,000, 20,000, 25,000, 30,000, 35,000, 40,000, and 50,000, and most preferably at least 100,000 cc of oxygen per square meter per 24 hour period at 1 atmosphere and at a temperature of 73 °F (at 0% relative humidity).
  • Typical gas transmission rates for gas-permeable film and film portions in accordance with the present invention range from 1,000 to 100,000, preferably 5,000 to 95,000, such as 10,000 to 90,000, 15,000 to 85,000, 20,000 to 80,000, 25.000 to 75,000, 30,000 to 70,000, and 40,000 to 60,000 cc of oxygen per square meter per 24 hour period at 1 atmosphere and at a temperature of 73 °F (at 0% relative humidity).
  • a gas-permeable film or film portion can itself have the aforedescribed levels of gas permeability or, alternatively, can be a film or film portion which does not inherently possess the aforedescribed levels of gas permeability but which is altered, e.g., perforated or peelably delaminated, to render the film gas- permeable as defined above.
  • substantially gas-impermeable refers to a film or film portion which admits less than 1000 cc of gas, such as oxygen, per square meter of film per 24 hour period at 1 atmosphere and at a temperature of 73 °F (at 0% relative humidity). More preferably, a substantially gas-impermeable film admits less than about 500, such as less than 300, and less than 100 cc of gas. More preferably still less than about 50 cc. and most preferably less than 25 cc, such as less than 20, less than 15, less than 10, less than 5, and less than 1 cc of gas per square meter per 24 hour period at 1 atmosphere and at a temperature of 73°F (at 0% relative humidity).
  • product support member refers to a component of a package on or in which a product is disposed.
  • Meat products are typically disposed in a tray-like package component comprising, e.g., expanded polystyrene sheet material which has been thermofo ⁇ ned into a desired shape, for supporting the meat product.
  • a product support member preferably includes a cavity into which the product is disposed and a peripheral flange which provides a sealing surface for attachment of a lid to the support member to thereby enclose the product within the cavity.
  • bond-strength refers generally to the adhesive force with which two adjacent films, or two adjacent film layers, are connected, and is measured by the force required to separate two films or film layers in accordance with ASTM F88-94.
  • peel refers to the act of removing one or more films from a multiple-film laminate by manually grasping and pulling back the film(s) along a plane or interface between two films in the laminate.
  • peel-force refers to the amount of force required to separate two films of a multiple-film laminate, and is measured in accordance with ASTM F904-91.
  • heat-seal refers to the union of two films by bringing the films into contact, or at least close proximity, with one another and then applying sufficient heat and pressure to a predetermined area (or areas) of the films to cause the contacting surfaces of the films in the predetermined area to become molten and intemiix with one another, thereby forming an essentially inseparable bond between the two films in the predetermined area when the heat and pressure are removed therefrom and the area is allowed to cool.
  • the phrase "sealant film” refers to a film which is confo ⁇ nably bonded to at least one of the exterior surfaces of a product support member.
  • the sealant film is bonded to the upper, as opposed to the lower, exterior surface of the support member and is a substantially gas-impermeable film.
  • ethylene/alpha-olefin copolymer generally designates copolymers of ethylene with one or more comonomers selected from C3 to C 2 o alpha-olefins, such as 1-butene, 1-pentene, 1-hexene, 1-octene, methyl pentene and the like, in which the polymer molecules comprise long chains with relatively few side chain branches. These polymers are obtained by low pressure polymerization processes and the side branching which is present will be short compared to non-linear polyethylenes (e.g., LDPE, a low density polyethylene homopolymer).
  • LDPE low density polyethylene homopolymer
  • Ethylene/alpha-olefin copolymers generally have a density in the range of from about 0.86 g/cc to about 0.94 g/cc.
  • the term linear low density polyethylene (LLDPE) is generally understood to include that group of ethylene/alpha-olefin copolymers which fall into the density range of about 0.915 to about 0.94 g/cc.
  • LLDPE linear low density polyethylene
  • LLDPE linear medium density polyethylene
  • VLDPE very low density polyethylene
  • ULDPE ultra-low density polyethylene
  • ethylene/alpha-olefin copolymer also includes homogeneous polymers such as metallocene-catalyzed EXACTTM linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from the Exxon Chemical Company, of Baytown, Texas; TAFMERTM linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from the Mitsui Petrochemical Corporation; and long-chain branched, metallocene-catalyzed homogeneous ethylene/alpha-olefin copolymers available from The Dow Chemical Company, known as AFFINITYTM resins.
  • EXACTTM linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from the Exxon Chemical Company, of Baytown, Texas
  • TAFMERTM linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from the Mitsui Petrochemical Corporation
  • homogeneous polymer refers to polymerization reaction products of relatively narrow molecular weight distribution and relatively narrow composition distribution.
  • Homogeneous polymers are structurally different from heterogeneous polymers (e.g., ULDPE, VLDPE, LLDPE, and LMDPE) in that homogeneous polymers exhibit a relatively even sequencing of comonomers within a chain, a mirroring of sequence distribution in all chains, and a similarity of length of all chains, i.e., a narrower molecular weight distribution.
  • homogeneous polymers are typically prepared using metallocene, or other single-site type catalysts, rather than using Ziegler-Natta catalysts. Such single-site catalysts typically have only one type of catalytic site, which is believed to be the basis for the homgeniety of the polymers resulting from the polymerization.
  • ethylene vinyl acetate copolymer or "EVA” is used to refer to a copolymer formed from ethylene and vinyl acetate monomers wherein the ethylene derived units in the copolymers are present in major amounts, preferably between about 60% and 98% by weight and the vinyl acetate derived units in the copolymer are present in minor amounts, preferably between about 2% and 40% by weight.
  • olefin generally refers to any one of a class of monounsaturated, aliphatic hydrocarbons of the general formula C n H 2n , such as ethylene, propylenc, and butene.
  • the term may also include aliphatics containing more than one double bond in the molecule such as a diolefin or diene, e.g., butadiene.
  • polyolefin refers to olefin polymers and copolymers, especially ethylene and propylene polymers and copolymers, and to polymeric materials having at least one olefinic comonomer, such as ethylene vinyl acetate copolymer and ionomer.
  • Polyolefins can be linear, branched, cyclic, aliphatic, aromatic, substituted, or unsubstituted.
  • terni polyolefin include homopolymers of olefin, copolymers of olefin, copolymers of an olefin and a non-olefinic comonomer copolymerizable with the olefin, such as vinyl monomers, modified polymers of the foregoing, and the like.
  • Modified polyolefins include modified polymers prepared by copolymerizing the homopolymer of the olefin or copolymer thereof with an unsaturated carboxylic acid, e.g., maleic acid, fumaric acid or the like, or a derivative thereof such as the anhydride, ester metal salt or the like.
  • an unsaturated carboxylic acid e.g., maleic acid, fumaric acid or the like, or a derivative thereof such as the anhydride, ester metal salt or the like.
  • styrene butadiene copolymer refers to a thermoplastic copolymer, generally a block copolymer. containing styrene comonomer and butadiene comonomer.
  • oriented or “stretch-oriented” refers to a polymer-containing material which has been stretched at an elevated temperature (the orientation temperature), followed by being “set” in the stretched configuration by cooling the material while substantially retaining the stretched dimensions.
  • a material can be stretched in one direction (uniaxial orientation), two directions (biaxial orientation), or multiple directions.
  • Biaxial orientation typically occurs in two directions which are pe ⁇ endicular to one another, such as the longitudinal direction and the transverse direction.
  • the present invention is directed to a tray-type package suitable for the central processing of fresh red meat which includes a substantially gas-impermeable support member or tray, a first film sealed to the tray which is gas-pcmieable or which includes a means defined therein for providing for an exchange of gases into and out of the package, and a substantially gas-impermeable film which encloses the first film.
  • the package most preferably contains a low oxygen gaseous atmosphere such as, for example, a nitrogen carbon dioxide mix.
  • a low oxygen gaseous atmosphere such as, for example, a nitrogen carbon dioxide mix.
  • the means for exchanging gases defined witliin the first film are preferably perforations defined within the first film which are exposed upon removal of the substantially gas-impermeable film.
  • films which are highly gas-permeable as a result of the specific component resins are within the scope of the first film of the present invention, it is prefe ⁇ ed that the first film is perforated. Most prefe ⁇ ed are gas-permeable films which are also perforated for improved permeability.
  • Figures 1 and 2 illustrate a package having a multiple-film lid which may be delaminated into a substantially gas-impermeable upper film and a perforated lower film.
  • Such multiple-film lids allow for a simplified packaging operation employing conventional single flange trays, a vacuum or, preferably, a vacuum and gas flush with a low oxygen atmosphere, and sealing of a single web to the tray flange in a single sealing step.
  • the upper film of the lid is peeled away revealing a perforated lower film which preferably has a gas transmission rate of at least about 50,000 cc/m2/24 hrs./atm. at 73°F, allowing for a rapid release of the low oxygen atmosphere and introduction of oxygen for immediate blooming of the packaged meat product.
  • a package 10 in accordance with the present invention includes a support member or tray 12 having side walls 14 and a base 16 defining an inner cavity 18 for receiving product 20.
  • a peripheral flange 22 is defined about the upper portions of side walls 14.
  • Multiple-film (laminate) lid 26 is sealed to the tray at the flange 22.
  • FIG 2 is a partial cross-section of the package 10 of Figure 1.
  • Lid 26 is a laminate of a nonperforated substantially gas-impermeable film 28 and a film 30 which includes perforations 32 defined therein. It is prefe ⁇ ed that film 30 is a gas-permeable film because, although the perforations defined therethrough greatly increase the gas transmission rate of the film, such inherent permeability aids in gas exchange and blooming will be hindered in areas of intimate film to meat contact
  • a nonpenneable film which is perforated to render it pemieable is also within the scope of the present invention As is shown in Figure 2.
  • nonperforated film 28 is peeled away to reveal perforated film 30 for a rapid exchange of gases and blooming of the packaged meat at retail Perforations 32 preferably range from about 5 to about 250 microns m diameter, more preferably 25 to 125 microns, and most preferably 75 to 100 microns in diameter Ideally, the perforations are large enough to permit the passage of atmospheric gas therethrough (oxygen, nitrogen, carbon dioxide), but small enough to prevent the passage of liquids or dirt
  • the perforations may be fo ⁇ ned by any suitable means, including the use of mechanical, chemical, or electrical devices
  • Non-hmitmg examples of such devices include those which perforate with laser energy, electrostatic discharge, ultrasonic waves, flame discharge, needles or other sha ⁇ objects, or combinations thereof
  • Preferred devices are those which produce laser energy or electrostatic discharge
  • An electrostatic discharge device operates by passing a film between a pair of electrodes and transmitting electricity to one of the electrodes in sufficient voltage that the electrode discharges through the film and to the other electrode,
  • laminate 26 is fo ⁇ ned by reactive surface modification of films 28 and/or 30 More preferably, laminate 26 is formed by corona lamination Specifically, when first film 30 includes perforations 32, corona lamination (or other fomi of reactive surface modification) is prefe ⁇ ed to either adhesive lamination, wherein the adhesive may occlude the perforations, or lamination under heat and pressure, wherein heat sufficient to weld the two films may partially or completely close the perforations by melt deformation Corona lamination may be employed to form a laminate which is delaminatable at any desired peel force, depending on the component resins of the adjacent bonding layers of the films being laminated and the degree of corona discharge exposure (which is, in turn, determined by the amount of power supplied to the corona unit and the speed at which the film being treated passes through the corona unit) For pu ⁇ oses of the present invention, in order to ensure that film 28 may be peelably removed from film 30, the bond strength between the two films should be such that a
  • Figure 3 diagrammatically illustrates the process for forming laminate 26 in accordance with die present invention
  • film 30 is passed through electrostatic microperforation device 50 such as discussed above
  • Film 28 is passed through corona treatment unit 52
  • film 30 may be corona treated instead of film 28 or, most preferably, the bonding surfaces of both films 28 and 30 are subjected to corona treatment
  • the bonding surface of film 28 and/or 30 is sub
  • the amount of corona discharge to winch the films are exposed is directly proportional to the amount of power supplied to the corona unit and also the speed at which the films are passed through the unit
  • Any desired combination of power input to the corona unit and film speed may be employed to achieve a desired bond-strength between the films
  • the amount of power to supplied to the corona umt may range, c g . from about 0 02 to about 0 5 kilowatts (kw) per mch of film width and the film speed through the corona unit may range, e g .
  • films 28 and 30 are then immediately pressed together at rolls 54 and taken up as laminate 26
  • the laminate of the present invention may include three or more component films Such may be desirable, for example, when film 30 includes therein an anti-fog additive That is, in order to prevent the accumulation of condensation on the inside surface of film 30 from the packaged food product, it is prefe ⁇ ed that
  • tlie detrimental effects of an anti-fog additive on corona bond-strength can be substantially reduced by the inclusion of an intermediate film between tlie two films which are desired to be bonded, wherein the intermediate fihn contains no anti-fog additive and wherein both the intermediate film and tlie anti-fog-containing film are fo ⁇ ned from, or include exterior layers at tlie interface of tlie two films which are formed from, materials which have a high affinity for one another when subjected to corona treatment ("interface materials").
  • both the intermediate film and the anti-fog-containing film are stretch-oriented films
  • almost any polyolefin or blend of polyolefins may be employed at the interface of the two films as the interface materials.
  • the polyolefin may be the same or different in each of the films. If one or both of the films is not stretch-oriented (but is, instead, a hot blown film, for example), it becomes more difficult to obtain a good corona bond between such films.
  • the interface material of die non-oriented film(s) includes at least one material selected from the group consisting of ethylene/vinyl acetate copolymer (EVA), ethylene/methacrylate copolymer (EMA), acrylic acid copolymers, methyl acrylic acid copolymers.
  • EVA ethylene/vinyl acetate copolymer
  • EMA ethylene/methacrylate copolymer
  • acrylic acid-modified EVA or EMA acrylic acid-modified EVA or EMA, anhydride-modified EVA or EMA, and syndiotactic polymethyl pentene.
  • the oriented film may include any polyolefin as tl e interface material. If both films are not stretch-oriented, the interface materials for both films are preferably selected from the above list in order to form a good corona bond.
  • the strength of the corona bond between the two films is improved despite the presence of anti-fog additive in one of the films.
  • a third, intermediate film be included between films 28 and 30.
  • the intermediate film may, if desired, have the same composition as film 30 except that the intermediate film would not contain anti-fog additive. This approach is demonstrated in Examples 6 and 8 below. Since the intermediate film contains no anti-fog additive, it forms a strong corona bond with the film 28 which also contains no anti-fog additive. In general, the bond between the intermediate film and film 28 will be stronger than tlie bond between the intermediate film and film 30 when film 30 contains an anti-fog additive. Thus, when laminate 26 is caused to be peelably delaminated, both film 28 and the intermediate film will be removed from package 10. leaving behind only film 30.
  • the intermediate film may have any desired film thickness, e.g., ranging from about 0.3 mil to about 5 mils and, more preferably, from about 0.5 mil to about 1 mil. Another reason to include an intermediate film in laminate 26 is to provide a relatively symmet ⁇ cal laminate structure which precludes curling, such as is set forth below in Example 5
  • all four bonding surfaces are preferably simultaneously corona treated and all three films are then immediately and simultaneously pressed together, although, less preferably, a first corona laminate may be fomied and then it's bonding surface may be simultaneously corona treated with the bonding surface of a third film and the laminate and film pressed together
  • rolls 54 are preferably heated in order to improve bonding between tlie two films
  • laminate 26 is fo ⁇ ned by a combination of corona lamination and thermal lamination
  • at least one of the films employed in forming the final laminate is a stretch-onented, heat sh ⁇ nkable film
  • a thin layer of an adhesive may be applied to tlie bonding surface of one of the films of tlie laminate such that laminate 26 would be formed by a combination of corona lamination and adhesive lamination
  • a combination of corona, adhesive, and thermal lamination may be employed if desired
  • the gas-permeable film or web of the present invention is an oxygen pemieable film which may be a formable or stretchable mate ⁇ al
  • Typical polyme ⁇ c matenals for the gas-permeable film may include any mate ⁇ al which can be securely sealed and bonded to the support member, such as polyethylene or any of a vanety of ethylene copolymers including, for example, ethylene vinyl acetate (EVA), ethylene/acrylate copolymers.
  • a prefe ⁇ ed gas-permeable film for use in accordance with the present invention is a symmetncal, five layer o ⁇ ented film having the structure
  • the gas-permeable film may have any desired thickness ranging, e g , from about 0 3 mil to about 5 mils and, more preferably, from about 0 5 mil to about 1 mil
  • Tl e substantially gas-impermeable film or web of the present invention may be any suitable banner layer, film or laminate which is substantially impermeable to gas such as oxygen so that a fresh meat product contained in a vacuum or other low oxygen atmosphere possesses an enhanced shelf life over a package without the bamer layer
  • Suitable polymenc matenals having gas bamer properties for use in the present invention include ethylene/vinyl alcohol copolymers, polyamides, vinylidene chloride copolymers (PVDC) such as vinylidene chloride/vinyl chloride copolymer or vinylidene chloride/methyl acrylate copolymer.
  • Laminates of a scalable film and a barrier structure which includes a barrier layer and a tough, non-fomiing material such as a biaxially oriented nylon or biaxially oriented polyester are especially prefe ⁇ ed for use as tlie substantially gas-impermeable lidding of tlie present inventive packages.
  • a prefe ⁇ ed substantially gas-impermeable web is SiOx- coated PET such as that sold under the tradename Simplicity (TM) by PC Materials of Mount Bethel, Pa. (“SiOx” is a silicon oxide where "x" typically ranges from 0.5 to 4.
  • the SiOx coating on the PET or other substrate generally has a thickness ranging from about 50 to about 2000 angstroms.
  • PVDC-coated PET wherein the PVDC coating typically ranges in thickness from about 1 to about 10 microns.
  • a variety of other laminates and multilayer films may also be employed as die substantially gas-impe ⁇ neable web of the present invention.
  • tlie films or webs which may be employed in accordance with the present invention may be monolayer or multilayer.
  • Multilayer films may be employed when all of the properties required of the film cannot be achieved by a single polymeric component or a blend of polymers in a single layer.
  • a substantially gas-impermeable film to be sealed to a tray in all likelihood will comprise a multilayer film because several properties are needed including peelable sealability, as well as oxygen barrier, impact, and outer abuse properties.
  • Laminates of sealable films and nonfo ⁇ ning materials such as biaxially oriented polyester or biaxially oriented nylon are also within die scope of the present invention and are widely recognized as superior lidstocks for tray-type packages.
  • tl e gas-penneable and gas-impermeable films In order for tl e gas-penneable and gas-impermeable films to be corona bonded with a desired bond-strength as discussed above (i.e., such that the films may be peelably delaminated a peel force ranging from about 0.001 to about 2.5 lb/inch), it is prefe ⁇ ed that the materials from wliich the films arc formed, or their exterior layers located at the interface of the two films, are materials wliich have a high affinity for one another when subjected to corona treatment ("interface materials").
  • gas-permeable and gas-impermeable films are stretch-oriented films
  • almost any polyolefin or blend of polyolefins may be employed at the interface of the two films as interface materials.
  • the polyolefin may be the same or different in each of the films. If one or both of the films is not stretch-oriented (but is.
  • the interface material of tl e non-oriented film(s) includes at least one material selected from the group consisting of ethylene/vinyl acetate copolymer (EVA), ethylene/methacrylate copolymer (EMA), acrylic acid copolymers, methyl acrylic acid copolymers, acrylic acid-modified EVA or EMA, anhydride-modified EVA or EMA, and syndiotactic polymethyl pentene.
  • EVA ethylene/vinyl acetate copolymer
  • EMA ethylene/methacrylate copolymer
  • acrylic acid copolymers methyl acrylic acid copolymers
  • acrylic acid-modified EVA or EMA acrylic acid-modified EVA or EMA
  • anhydride-modified EVA or EMA anhydride-modified EVA or EMA
  • syndiotactic polymethyl pentene syndiotactic polymethyl pentene.
  • the oriented film may include any polyolefin as tlie compatible interface material
  • both the gas-penneable and gas- impermeable films contain exterior layers wliich are in contact with another at the interface between tlie two films and which comprise a styrene/butadiene copolymer (SBC).
  • SBC styrene/butadiene copolymer
  • a sealant film is included as a liner for at least the upper surface of support member 12 as a means to improve the functional characteristics of the support member when such improvement is deemed necessary or desirable.
  • a sealant film which provides the required degree of gas-impermeability may be employed.
  • a sealant film may also be used to improve the bond-strength between the gas- penneable film and support member when the film and support member are constructed of materials which are not readily capable of forming a sufficiently strong heat-seal. In that case, a sealant film may be used which both bonds well to the upper surface of the support member and also forms a strong heat-seal with the gas-permeable film.
  • Support member 12 can have any desired configuration or shape, e.g., rectangular, round, oval, etc.
  • flange 22 may have any desired shape or design, including a simple, substantially flat design which presents a single sealing surface as shown, or a more elaborate design which presents two or more sealing surfaces, such as the flange configurations disclosed in U.S. Patent Nos. 5,348,752 and 5,439,132, the disclosures of which are hereby inco ⁇ orated herein by reference.
  • the flange may also include a peripheral lip positioned adjacent and exterior to the heat-sealing surface to facilitate the peelable delamination of lid 26, such as disclosed in U.S. Serial No. 08/733,843, entitled PACKAGE HAVING PEEL INITIATION
  • Suitable materials from which support member 12 can be fonned include, without limitation, polyvinyl chloride, polyethylene terephthalate, polystyrene, polyolefins such as high density polyethylene or polypropylene, paper pulp, nylon, polyurethane, etc.
  • the support member may be foamed or non-foamed as desired, and preferably provides a barrier to the passage of oxygen therethrough, particularly when the packaged food product is oxygen- sensitive (i.e., perishable, degradable, or otherwise changeable in the presence of oxygen), such as fresh red meat products (e.g., beef, veal, lamb, pork, etc.), poultry, fish, cheese, fruits, or vegetables.
  • support member 12 preferably allows less than or equal to about 500 cc of oxygen to pass, more preferably less than about 100 cc of oxygen, more preferably still less than about 50 cc, and most preferably less than about 25 cc of oxygen to pass per square meter of material per 24 hour period at 1 atmosphere and at a temperature of 73°F (at 0% relative humidity).
  • Support member 12 may be formed from a material which itself provides a barrier to the passage of oxygen, e.g., vinylidene chloride copolymer, nylon, polyethylene terephthalate, ethylene/vinyl alcohol copolymer, etc.
  • support member 12 may have a substantially gas-impermeable sealant film laminated or otherwise bonded to the inner or outer surface thereof as described above, and as also disclosed in U.S. Patent Nos. 4,847,148 and 4,935,089, and in U.S. Serial No. 08/326,176, filed October 19, 1994 and entitled "Film Substrate Composite Material” (published as EP 0 707 955 Al on April 24, 1996), the disclosures of which are hereby inco ⁇ orated herein by reference.
  • Any such sealant film preferably includes an oxygen-barrier material such as e.g., vinylidene chloride copolymer (saran), nylon, polyethylene terephthalate, ethylene/vinyl alcohol copolymer, etc.
  • Laminates produced in accordance with the present invention are set forth in the Examples below.
  • single slashes (/) indicate an intrafilm layer/layer interface
  • double slashes (If) indicate an interfilm, i.e., film film, corona lamination interface
  • underlined double slashes (//) indicate a peelable interface.
  • the following resins were employed:
  • EVA1 Rexene PE 1335, an ethylene vinyl acetate copolymer having 3.3 percent by weight of vinyl acetate, a density of 0.924 g/cc and a 2.0 MI, supplied by Rexene;
  • EVA2 98.5% by weight of LD 362, an ethylene vinyl acetate copolymer having in the range of 3.5% to 4.5%) by weight of vinyl acetate, a density of 0.925 g/cc and a 2.0 MI (supplied by Exxon), also including 1% by weight of polyethoxylated cetyl alcohol and 0.5% by weight of glycerol monostearate anti-fog additives;
  • EVA3 96.5% of Rexene PE 1335, described above, and 3.5% by weight of polyoxyethylene (4) nonylphenol anti-fog additive;
  • EVA4 Elvax (TM) 3165 ; an ethylene vinyl acetate copolymer having 18 percent by weight of vinyl acetate, a density of 0.94 g/cc and a 0.7 MI, supplied by DuPont;
  • EVA5 Exxon 32.89; an ethylene vinyl acetate copolymer having 4% by weight vinyl acetate, supplied by Exxon;
  • LLDPE 1 Dowlex 2045.04 (TM), a heterogeneous ethylene octene copolymer having a density of 0.920 g/cc and a 1.0 MI, supplied by tlie Dow Chemical Co.;
  • LLDPE2 98.5% by weiglit of Dowlex 2045.04 (TM), described above, further including 1% by weight of polyetiioxylated cetyl alcohol and 0.5% by weiglit of glycerol monostearate anti-fog additives;
  • LLDPE3 96.5% by weight of Dowlex 2045.04 CTM), described above, and 3.5% by weight of polyoxyethylene (4) nonylphenol anti-fog additive;
  • LLDPE4 Dowlex 2244A (TM); a heterogeneous ethylene/octene copolymer having a density of 0.916 g/cc and a 3.3 MI, supplied by the Dow Chemical Co.;
  • LMDPE Dowlex 2037 (TM), a heterogeneous ethylene/octene copolymer having a density of 0.935 g/cc and a 2.5 MI, supplied by the Dow Chemical Co.;
  • LDPE NA 345-013, a low density polyethylene having a 1.8 MI, supplied by Quantum;
  • Adh-1 Plexar 107 (TM), an anhydride modified ethylene vinyl acetate copolymer having a
  • Adh-2 Bynel CXA-4104 (TM), an anhydride modified linear low density polyethylene having a density of 0.920 g/cc and a 1.0 MI, supplied by duPont;
  • Adh-3 Tymor 1203 (TM), an anl ydride-modified linear low density polyethylene; supplied by duPont;
  • EVOH Soarnol ET (TM), an ethylene vinyl alcohol copolymer having 38% by mole ethylene and a 3.2 MI, supplied by Nippon Gohsei;
  • Glyc a blend of 88% by weight of mono & diglycerides and 12% by weight of propylene glycol;
  • AB-MB an antiblock masterbatch, Ampacet 10853, a linear low density polyethylene containing 20% by weight diatomaceous silica having a 1.5 MI;
  • EMA EMA 2207, an ethylene methyl acrylate copolymer having 24% by weight of methyl acrylate and a 6.0 MI, supplied by Chevron;
  • SBC KK36 (TM) styrene/butadiene copolymer having 75 percent by weight of styrene, a melt index of 8.0 (Condition G of ASTM D-1238) and a density of 1.01 g/cc, obtained from Phillips 66, of Pasadena, Texas.
  • Example 1 A five layer film having the structure: EVA1 / LLDPE1 / EVA1 / LLDPE1 / EVA1 was coextruded, biaxially oriented, and had a thickness of about 0.6 mil. The final film was subsequently corona treated with an SSI 55 corona treatment unit from Enercon Industries Co ⁇ oration at 0.11 kw/in. at 50 ft/min. A sheet of SiOx coated PET (0.48 mil) was corona treated with the same treatment unit at 0.11 kw/in. at 50 ft/min at the surface containing the SiOx coating. The corona treated surfaces of the two films were pressed together by a pair of nip rollers to form a laminate having the structure:
  • the laminate was heat-sealed to the flange of a BT979 barrier foam tray (a polystyrene foam tray having an oxygen-barrier sealant film bonded to the upper surface thereof) and then the SiOx coated PET film was peelably delaminated from the five layer film which remained sealed to tlie tray .
  • a BT979 barrier foam tray a polystyrene foam tray having an oxygen-barrier sealant film bonded to the upper surface thereof
  • Example 2 A laminate and package was formed substantially as set forth in Example 1. However, prior to corona treatment, the five layer film was perforated by electrostatic discharge.
  • Example 3 A laminate was fomied substantially as set forth in Example 1. However, the five layer, oriented film employed had tlie following 0.6 mil structure:
  • EVA2 / LLDPE2 / EVA2 / LLDPE2 / EVA2 such that the final laminate had tlie structure: PET/ SiOx 11 EVA2 / LLDPE2 / EVA2 / LLDPE2 / EVA2.
  • the laminate was heat-sealed to the flange of a BT979 barrier foam tray and then the SiOx coated PET film was peelably delaminated from the five layer film wliich remained sealed to the tray.
  • Example 4 A laminate and package was formed substantially as set forth in Example 3. However, prior to corona treatment, the five layer film was perforated by electrostatic discharge.
  • Example 5 A five layer, oriented film as set forth in Example 1 was produced and corona treated at 0.11 kw/in at 50 ft/min on one surface thereof. A five layer, oriented film as set forth in Example 3 was produced, perforated by electrostatic discharge and corona treated at 0.11 kw/in at 50 fVmin on one surface thereof. A sheet of SiOx-coated PET was corona treated on both surfaces thereof with a SS2544 corona treatment unit from Enercon Industries at 0.13 kw/in at 50 ft/min.
  • the three films were simultaneously pressed togetlier by a pair of nip rollers to fomi a laminate having the structure: EVAl/LLDPEl/EVAl/LLDPEl/EVAl//SiOx-coated PET//perforated(EVA2/LLDPE2/EVA2 LLDPE2/EVA2).
  • the laminate was heat-sealed to the flange of a BT979 barrier foam tray and then the SiOx coated PET film and non-perforated film was peelably delaminated (as a two-film laminate) from the perforated five layer film which remained sealed to the tray.
  • Example 6 A five layer, oriented film as set forth in Example 1 was produced and corona treated at 0.13 kw/in at 50 ft/min on both surfaces thereof. A five layer, oriented film as set forth in Example 3 was produced, perforated by electrostatic discharge and corona treated at 0.11 kw/in at 50 ft/min on one surface thereof. A sheet of SiOx-coated PET was corona treated on the SiOx-coated surface thereof at 0.11 kw/in at 50 fl/min. The three films were pressed together by a pair of nip rollers to form a laminate having the structure: PET/ SiOx //EVA1/LLDPE1/EVA1/LLDPE1/
  • the laminate was heat-sealed to the flange of a BT979 barrier foam tray and then the SiOx coated PET film and non-perforated film was peelably delaminated (as a two-film laminate) from the perforated five layer film which remained sealed to the tray.
  • Example 7 A seven layer film was coextruded and hot blown having tlie 2.0 mil structure: 98% lonomer + 2% AB-MB/LDPE/Adh-l/EVOH/Adl ⁇ -l/LDPE/97% EMA + 3% AB-MB.
  • a five layer film (0.6 mil) was coextruded having the structure: EVA3 / LLDPE3 / EVA3 / LLDPE3 / EVA3 and was biaxially-oriented.
  • the seven layer hot blown film was corona treated on one surface thereof at 0.11 kw/in at 100 ft/min.
  • the five layer oriented film was corona treated on one surface thereof at 0.11 kw/in at 100 ft/min.
  • corona treated surfaces of the two films were pressed together by a pair of nip rollers to form a laminate having tlie structure: 98% lonomer + 2% AB-MB LDPE/Adli-l EVOH/Adli-l/LDPE/97% EMA + 3% AB- MB/ EVA3/LLDPE3/EVA3/LLDPE3/EVA3
  • the laminate was heat-sealed to the flange of a BT979 barrier foam tray (with EVA3 in contact with tlie tray) and delaminated at the J I_ interface.
  • Example 8 A two layer film (0.5 mil) was coextruded having the structure:
  • the two layer film was corona treated on the adhesive surface thereof at 0.11 kw/in at 150 ft/min.
  • a sheet of SiOx-coated PET was corona treated on the SiOx-coated surface thereof at 0.11 kw/in at 150 ft/min.
  • a five layer oriented film as set forth in Example 1 was corona treated at 0.13 kw/in at 150 ft/min on both surfaces thereof. The three fihns were pressed together by a pair of nip rollers to form a laminate having the structure:
  • Example 9 A LLDPE or LDPE biaxially oriented, monolayer intermediate film without anti-fog additive is corona treated on both surfaces thereof and bonded on one surface to a perforated LLDPE or LDPE biaxially oriented, monolayer film containing therein an anti-fog additive (tlie bonding surface of which is also corona treated), and bonded on the other surface to a sheet of SiOx-coated PET (or PVDC- coated PET), the bonding surface of which is also corona treated, to form the following laminates:
  • a multilayer film with the following construction was hot blown:
  • This film was corona laminated to a sheet of oriented polypropylene (440 CGW from No ⁇ rop) to fomi a lidstock with the SBC on the side to be in contact with the permeable film (Example 12), while having a high- temperature-resistant material (oriented PP) on the side contacting the heat-seal bar.
  • oriented polypropylene 440 CGW from No ⁇ rop
  • oriented PP high- temperature-resistant material
  • Example 11 A multilayer film with the following construction was hot blown: 96% SBC+4% AFOG/96% EVA4/Adh-3/EVOH/Adh-3/EVA5+4% AFOG This film was corona laminated to a sheet of oriented polypropylene (440 CGW from
  • No ⁇ rop to form a lidstock with the SBC on the side to be in contact with the permeable film (Example 12), while having a high- temperature-resistant material (oriented PP) on the side contacting the heat-seal bar ("AFOG” is polyoxyethylene (4) nonylphenol anti-fog additive).
  • Example 12 A coextruded, biaxially oriented multilayer film had the following construction:
  • Adh-3/EVOH Adh-3/EVA5//O ⁇ ented PP LLDPE4/ULDPE/EVA4/ULDPE/SBC//96% SBC+4% AFOG/EVA4+4% AFOG/Adh-

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
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Abstract

La présente invention concerne un procédé et un emballage permettant la coupe et l'emballage de la viande rouge dans une installation centralisée. Ledit emballage comprend une barquette sensiblement imperméable aux gaz contenant un produit, une première pellicule perméable et/ou perforée scellée à la barquette de manière à enfermer le produit, et une deuxième pellicule sensiblement imperméable aux gaz recouvrant la première pellicule, de manière qu'en retirant la pellicule sensiblement imperméable aux gaz, on permet aux gaz de pénétrer dans l'emballage et d'en sortir. L'une des deux pellicules est traitée par décharge corona, et les deux pellicules sont pressées l'une contre l'autre afin de former un stratifié. Le stratifié est scellé à la barquette de manière que la première pellicule est scellée à la barquette et que la deuxième pellicule est scellée de façon pelable à la première pellicule.
PCT/US1997/021501 1996-11-25 1997-11-21 Emballage muni d'un opercule a plusieurs couches comprenant une pellicule impermeable aux gaz adherant de façon pelable a une pellicule permeable aux gaz WO1998023443A2 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU53616/98A AU5361698A (en) 1996-11-25 1997-11-21 Package having a multiple-film lid comprising a gas-impermeable film peelably adhered to a gas-permeable film

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US75599196A 1996-11-25 1996-11-25
US08/755,991 1996-11-25

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WO1998023443A2 true WO1998023443A2 (fr) 1998-06-04
WO1998023443A3 WO1998023443A3 (fr) 1998-09-03

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999028123A1 (fr) * 1997-12-02 1999-06-10 Cryovac, Inc. Stratifie, emballage fabrique a partir de ce stratifie et procede d'emballage
WO2001012523A1 (fr) * 1999-06-16 2001-02-22 Bongers Cornelis Margaretha Th Procede d'emballage separe de differents types d'aliments et emballage correspondant
US6627273B2 (en) 2001-03-13 2003-09-30 Cryovac, Inc. Lidstock laminate
US6769227B2 (en) 2002-07-23 2004-08-03 Cryovac, Inc. Package including a lidstock laminate
FR2873992A1 (fr) * 2004-08-05 2006-02-10 Perle Du Sud Procede et dispositif d'emballage de produits vegetaux frais
US11806981B2 (en) 2017-10-09 2023-11-07 Cryovac, Llc Use of high barrier and peelable polyester film for tray lidding, dual ovenable packaging applications and tray lidding dual ovenable packages obtained therefrom

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WO1999028123A1 (fr) * 1997-12-02 1999-06-10 Cryovac, Inc. Stratifie, emballage fabrique a partir de ce stratifie et procede d'emballage
US6670023B2 (en) 1997-12-02 2003-12-30 Cryovac, Inc. Laminate for case-ready packaging including a gas-impermeable film capable of delaminating into a gas-permeable portion and a gas-impermeable portion, and a gas-permeable film bonded thereto
WO2001012523A1 (fr) * 1999-06-16 2001-02-22 Bongers Cornelis Margaretha Th Procede d'emballage separe de differents types d'aliments et emballage correspondant
US6627273B2 (en) 2001-03-13 2003-09-30 Cryovac, Inc. Lidstock laminate
US6769227B2 (en) 2002-07-23 2004-08-03 Cryovac, Inc. Package including a lidstock laminate
FR2873992A1 (fr) * 2004-08-05 2006-02-10 Perle Du Sud Procede et dispositif d'emballage de produits vegetaux frais
EP1647489A3 (fr) * 2004-08-05 2006-05-24 Perle Du Sud Procédé et dispositif d'emballage de produits végétaux frais
US11806981B2 (en) 2017-10-09 2023-11-07 Cryovac, Llc Use of high barrier and peelable polyester film for tray lidding, dual ovenable packaging applications and tray lidding dual ovenable packages obtained therefrom

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AR014337A1 (es) 2001-02-28
AU5361698A (en) 1998-06-22

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