WO1998023443A2

WO1998023443A2 - Package having a multiple-film lid comprising a gas-impermeable film peelably adhered to a gas-permeable film

Info

Publication number: WO1998023443A2
Application number: PCT/US1997/021501
Authority: WO
Inventors: Charles R. Barmore; Narender P. Luthra; Walter B. Mueller; Joseph E. Owensby
Original assignee: Cryovac, Inc.
Priority date: 1996-11-25
Filing date: 1997-11-21
Publication date: 1998-06-04
Also published as: WO1998023443A3; AU5361698A; AR014337A1

Abstract

A method and package which allows for butchering and packaging of fresh red meat at a centralized facility is provided. The package (10) includes a substantially gas-impermeable tray (12) supporting a product, a first permeable and/or perforated film (30) sealed to the tray for enclosing the product, and a second substantially gas-impermeable film (28) enclosing the first film (30), such that removal of said substantially gas-impermeable film (28) provides for the exchange of gases into and out of the package. One of either the first (30) or second (28) films has been corona treated and the two films are pressed together to form a laminate (26). The laminate (30) is sealed to the tray (12) such that the first film (30) is sealed to the tray (12) and the second film (28) is peelably sealed to the first film (30).

Description

PACKAGE HAVING A MULTIPLE-FILM LID COMPRISING A

GAS-IMPERMEABLE FILM PEELABLY ADHERED TO A

GAS-PERMEABLE FILM

BACKGROUND OF THE INVENTION

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.

Historically, large sub-primal cuts of meat have been butchered and packaged in each supermarket. This arrangement has long been recognized to be inefficient and expensive. It would instead be preferable to butcher and package the meat at a central processing facility which benefits from economies of scale, and then ship the packaged meat to individual superaiarkets or other retail outlets such as is done, for example, with many poultry products. It is believed that central processing of meat would also lead to a higher quality, more sanitary product with a longer shelf-life than meat which is butchered and packaged in individual supermarkets.

Fresh red meat presents a particular challenge to the concept of centralized processing and packaging due to its oxygen-sensitivity. Such oxygen-sensitivity is manifested in the shelf- life and appearance (color) of a packaged meat product. 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. When meat is exposed to a sufficiently high concentration of oxygen, e.g., as found in air, it assumes a bright red color which most consumers associate with freshness. After 1 to 3 days of such exposure, however, meat assumes a brown color which, like the purple color, is undesirable to most consumers (and indicates that the meat is beginning to spoil).

Thus, in order to effectively butcher and package meat products in a central facility for distribution to retail outlets, 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. While in the retail display case, the meat product is desirably contained in a package which protects it from microbial and other contamination. In order to attain the maximum economic benefit from centralized packaging, 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. As can be appreciated, 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 peπneable to the passage of oxygen to allow the packaged meat product to bloom. Thus, 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. With the separate film approach, 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. One drawback of this approach is the difficulty of sealing two separate lids to a conventional, single-flange tray in an automated fashion, i.e., continuously from separate permeable and impermeable webs of film. The permeable lid must be applied to the tray flange from a continuous web, secured (e.g., heat- welded) to an inner periphery of the flange, and then severed from the web in such a manner as to leave a sufficient area on an outer periphery of the flange to which the impermeable lid can be secured and severed from a continuous web of an impermeable film. Since this approach involves two separate lidding operations, it entails a relatively complex and expensive packaging procedure (as compared to a single-hd packaging operation) For example, it is difficult to sever the permeable hd from the web in such a manner that sufficient room is left on the outer periphery of the flange to provide a sealing surface for the impermeable lid without damaging the outer flange periphery It is also difficult to completely remove atmospheric oxygen from the space between the permeable and impermeable lids

While single, peelable lids have the advantage of providing a single web for sealing to a conventional tray flange, such films often fail during peeling, with the impermeable film either being difficult to delaminate from the peπneable film or with all or part of the permeable film remaining bonded to the impermeable film and tearing away from the rest of the package, thereby resulting in tears or holes in the package which expose the packaged meat product to dirt or contamination The bond which is formed between the films must be strong enough to prevent film separation during shipping and storage so that oxygen does not prematurely enter the package via the gas-permeable film (I e , prior to the time when the retail worker intentionally peels the impermeable film from the permeable film) At the same time, the bond between the two films must provide sufficient peelabihty that the two films can be separated without tearing or otherwise compromising the pemieable film as noted above As can be readily appreciated, these are difficult and somewhat conflicting requirements to meet

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 For example, when using 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 In addition, and as discussed more fully below, 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

Accordingly, there is a need in the art for 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.

By laminating the permeable and impermeable films via corona treatment or other reactive surface modification technique, 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.

BRIEF DESCRIPTION OF THE DRAWINGS

A detailed description of prefeπed embodiments of the invention follows, with reference to the accompanying drawings, wherein:

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; and Fig. 3 is a diagrammatic illustration of the process for making a laminate in accordance with the present invention.

DEFINITIONS As used herein, the term "film" refers to a theπnoplastic material, generally in sheet or web foπn, 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).

As used herein, the teπn "laminate" refers to a composite structure of two or more films which are bonded together. Generally, 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 refeπed to herein as the "bonding surface." The plane or contour at which two films intersect is refeπed to herein as an "interface."

As used herein, the teπn "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.

As used herein, the phrases "reactive surface modification," "reactively modifying the surface of," "reactively-modified surface" and the like refer 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). Specific examples of 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 refeπed to as a "modified surface" or, in the case of corona treatment, a "corona treated surface."

As used herein, the phrase "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). In accordance with the present invention, 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.

As used herein, the phrase "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).

As used herein, the phrase "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 thermofoπned 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.

As used herein, the term "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.

As used herein, the terms "peel," "peeling," and the like refer 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. As used herein, the term "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.

As used herein, the term "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.

As used herein, the phrase "sealant film" refers to a film which is confoπnably bonded to at least one of the exterior surfaces of a product support member. Preferably, 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.

As used herein, the phrase "ethylene/alpha-olefin copolymer" generally designates copolymers of ethylene with one or more comonomers selected from C3 to C₂o 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). 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. Sometimes linear polyethylene in the density range from about 0.926 to about 0.94 is referred to as linear medium density polyethylene (LMDPE). Lower density ethylene/alpha-olefin copolymers may be referred to as very low density polyethylene (VLDPE, typically used to refer to the ethylene/ butene copolymers available from Union Carbide with a density ranging from about 0.88 to about 0.91 g/cc ) and ultra-low density polyethylene (ULDPE. typically used to refer to the ethylene/octene copolymers supplied by Dow).

The phrase "ethylene/alpha-olefin copolymer" also includes homogeneous polymers such as metallocene-catalyzed EXACT™ linear homogeneous ethylene/alpha-olefin copolymer resins obtainable from the Exxon Chemical Company, of Baytown, Texas; TAFMER™ 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 AFFINITY™ resins. The phrase "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. Furthermore, 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.

As used herein, the term "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.

As used herein, the term "olefin" generally refers to any one of a class of monounsaturated, aliphatic hydrocarbons of the general formula C_nH_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. As used herein, the term "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. Included in the terni polyolefin are 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. It could also be obtained by incoφorating into the olefin homopolymer or copolymer, 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.

As used herein, a "styrene butadiene copolymer" (SBC) refers to a thermoplastic copolymer, generally a block copolymer. containing styrene comonomer and butadiene comonomer.

As used herein, the term "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 peφendicular to one another, such as the longitudinal direction and the transverse direction.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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. Thus, removal of the substantially gas-impermeable film allows for a release of the low oxygen atmosphere and for introduction of oxygen to the packaged meat product.

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.

Although 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 prefeπed that the first film is perforated. Most prefeπed 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. At retail, 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.

Looking to Figure 1, 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.

Figure 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 prefeπed 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 However, 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 foπned 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 shaφ 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, thereby perforating the film

It is prefeπed that laminate 26 is foπned 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 prefeπed 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 puφoses 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 peel force of no more than about 2 5 lb/inch is required to delaminate the two films In fact, a weak bond, such as one representing a peel force as low as about 0 001 lb/inch, is sufficient to keep the films together dunng the manufacture of the package That is, generally ,the present inventive package is made by providuig a tray containing a product, providing films 30 and 28, corona treating at least one of the two films, pressing them together to form laminate 26, extending laminate 26 over the tray such that film 30 is directly adjacent to the tray, and sealing the laminate to the tray A bond strength falling within these ranges provides a balance between sufficient adhesion to prevent premature separation of film 28 from film 30, e g during manufacture, shipping and storage, and sufficient peelabihty so that the film 28 can be separated from film 30 without tearing or otherwise compromising film 30 A bond strength of more than 2 5 lb/inch results in a lid that is more difficult to peel, or can result in unintentional separation of the entire laminate from the tray On the other hand, a bond strength of less than about 0 001 lb/inch creates a greater likelihood of premature separation of film 28 from film 30

Figure 3 diagrammatically illustrates the process for forming laminate 26 in accordance with die present invention For the embodiment illustrated, film 30 is passed through electrostatic microperforation device 50 such as discussed above Film 28 is passed through corona treatment unit 52 It should be noted that 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

Within unit 52, the bonding surface of film 28 and/or 30 is sub|ected to corona discharge 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 . from about 10 to about 2000 feet/minute Corona treatment units are commercially available, e g , from Enercon Industnes Coφoration of Menomonee Falls, WI By one theory, a high voltage passed through an electrode adjacent to the film surface ionizes the air, causing oxidation of the corona-treated film surface Altliougli a vaπety of theoπes have been suggested to explain corona lamination bonding of polyolefins, it is widely recognized that corona treatment of polymenc matenals can improve adherence characteπstics under certain circumstances Preferably, films 28 and 30 are then immediately pressed together at rolls 54 and taken up as laminate 26 Although not shown in Figure 3, it should be noted from the Examples below that 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 prefeπed that film 30 include an anti-fog additive therein Suitable anti-fog additives include, e g , polyethoxvlated cetyl alcohol, glycerol monostearate, polyoxyethylene (4) nonylphenol, glycerol monooleate, polyoxy ethylene (4) lauryl alcohol, polyoxy ethylene (26) glycerol ether, and polyoxy ethylene (20) sorbitol ether The inclusion of anti-fog additives in a film, however, has been found to result in weak corona bond between the anti-fog-containing film and another film Although it may be possible to compensate for the weakness of the bond by increasing the amount of exposure to the corona discharge (by increasing the amount of corona discharge and/or slowing the speed at which the film passes by the corona electrode), such measures may often be too costly and time-consuming for commercial production.

The inventors have discovered 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 foπned 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"). If 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. In this regard, 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 inventors have deteimined, however, that a good corona bond can still be obtained if 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. acrylic acid-modified EVA or EMA, anhydride-modified EVA or EMA, and syndiotactic polymethyl pentene. If one of the films is stretch-oriented and the other is not, 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.

Accordingly, the strength of the corona bond between the two films is improved despite the presence of anti-fog additive in one of the films. Thus, when an anti-fog additive is included in film 30, it is prefeπed that 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 symmetπcal laminate structure which precludes curling, such as is set forth below in Example 5

For any three-film laminates, 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

Referring again to FIG 3. rolls 54 are preferably heated in order to improve bonding between tlie two films By such process, laminate 26 is foπned by a combination of corona lamination and thermal lamination However, for the examples given below it should be noted that at least one of the films employed in forming the final laminate is a stretch-onented, heat shπnkable film Thus, for such embodiments care should be taken to insure that the temperature of the nip rolls is sufficiently lower than the onentation temperature of the heat shπnkable film m order to preclude shrinkage of that film during manufacture of tlie laminate

Also optionally, 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 Also, 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 mateπal Typical polymeπc matenals for the gas-permeable film may include any mateπal 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. etliylene/acryhc acid copolymers including metal neutralized salts thereof, and ethylene/alpha-olefin copolymers such as, e g , linear low density polyethylene (LLDPE) A prefeπed gas-permeable film for use in accordance with the present invention is a symmetncal, five layer oπented film having the structure

EVA / LLDPE / EVA / LLDPE / EVA, although a wide vaπety of gas-permeable films may be employed 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 prefeπed for use as tlie substantially gas-impermeable lidding of tlie present inventive packages. A prefeπed 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.) Also prefeπed is 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-impeπneable web of the present invention.

Generally, 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. For example, 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 nonfoπning 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.

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 prefeπed 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"). If both the 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. instead, a hot blown film, for example), it is prefeπed that 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. If one of the films is stretch-oriented and the other is not, the oriented film may include any polyolefin as tlie compatible interface material. If both films are not stretch- oriented, the interface materials for both films arc preferably selected from the above list in order to form a good corona bond.

In another prefeπed embodiment of the invention, 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). As described in Examples 10, 11, and 12, the SBC-containing layers tiius form the peelable interface between the two films.

Preferably, 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. For example, if the support member is constructed of a material which is not sufficiently gas-impermeable for the intended package application, 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. Similarly, 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 incoφorated 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

MECHANISM and filed October 18. 1996, tlie disclosure of which is hereby incoφorated herein by reference.

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. When such oxygen-sensitive products are to be packaged, 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. Alternatively, 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 incoφorated 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. For each of the multilayer film and laminate structures shown in the Examples, single slashes (/) indicate an intrafilm layer/layer interface; double slashes (If) indicate an interfilm, i.e., film film, corona lamination interface; and 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.;

lonomer: Surlyn 1650 (TM), a zinc salt of an ethylene methacrylic acid copolymer, supplied by duPont;

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

3.2 MI, supplied by Quantum;

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: an antiblock, anhydrous sodium silicate;

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; and

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 Coφoration 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:

PET/ SiOx II EVA1 / LLDPE1 / EVA1 / LLDPE1 / EVA1.

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 .

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/

EVAl//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 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/Adlι-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. The 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:

Adlι-2 / 70.5% LLDPEl + 23.5% LMDPE + 4% Glyc. + 2% AB and was biaxially-oriented. 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:

PET/ SiOx //EVAl/LLDPEl/EVAl/LLDPEl/EVAl//Adlι-2/70.5% LLDPEl + 23.5% LMDPE +

4% Glyc. + 2% AB. The laminate was heat-sealed to the flange of a BT979 barrier foam tray (with the "70.5% LLDPEl + 23.5% LMDPE + 4% Glyc. + 2% AB" layer in contact with the tray) and delaminated at the // interface.

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:

LLDPE + Anti-Fog//LLDPE//SiOx/PET LDPE + Anti-Fog//LDPE//PVDC/PET LLDPE + Anti-Fog//LLDPE//PVDC/PET

LDPE + Anti-Fog//LDPE//SiOx/PET

Example 10

A multilayer film with the following construction was hot blown:

96% SBC + 4% AB-MB/EVA4/Adh-3/EVOH/Adlι-3/EVA5

This film was corona laminated to a sheet of oriented polypropylene (440 CGW from Noφrop) 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.

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

Noφrop) 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:

SBC/ULDPE/EVA4/ULDPE/LLDPE4 This film was corona-laminated to the films of Examples 10 and 11 to produce peelable laminates of the following constructions ("ULDPE" is XU 61521 ultra low density polyethylene from Dow): LLDPE4/ULDPE/EVA4/ULDPE/SBC//96% SBC+4%AB-MB/EVA4/

Adh-3/EVOH Adh-3/EVA5//Oπented PP LLDPE4/ULDPE/EVA4/ULDPE/SBC//96% SBC+4% AFOG/EVA4+4% AFOG/Adh-

3/EVOH/Adh-3/EVA5//Oriented PP The foregoing laminates were heat-sealed to the flange of a BT979 barrier foam tray (with tiie "LLDPE4 layer in contact with the tray) and delaminated at the IJ_ interface, i.e., the lidstock separated at the junction of the two SBC materials.

The foregoing description of prefeπed embodiments of the invention has been presented for puφoses of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embcπiiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. It is intended that tiie scope of tiie invention be defined by the claims appended hereto, and their equivalents.

Claims

WHAT IS CLAIMED IS:

1. A package, comprising: a product support member having a cavity formed therein, a product being disposed with said cavity; a laminate heat-sealed to the support member and enclosing tiie product therein, said laminate comprising a first film in contact with said suppport member and a second film, at least one of said first and second films comprising a reactively-modified surface such that said laminate peelably delaminates at a peel force ranging from 0.001 pounds per inch to 2.5 pounds per inch.

2. The package set forth in claim 1 wherein the first film is gas-permeable.

3. The package set forth in claim 2 wherein said gas-permeable film is perforated.

4. The package set forth in claim 1 wherein said first film is rendered gas-permeable by perforating said film.

5. The package set forth in claim 1 wherein said first and second films are in direct contact with one another and define an interface therebetween, said at least one corona-treated surface being located at said interface.

6. The package set forth in claim 5 wherein said first and second films are stretch-oriented films, each of said films comprising a polyolefin at said interface.

7. The package set forth in claim 5 wherein at least one of said first and second films are not stretch-oriented and comprise at least one material selected from the group consisting of ethylene/vinyl acetate copolymer (EVA), ethylene/metiiacrylate copolymer (EMA), acrylic acid copolymers, methyl acrylic acid copolymers, acrylic acid-modified EVA or EMA. anhydride-modified EVA or EMA. and syndic-tactic polymethyl pentene at said interface.

8. The package set forth in claim 5 wherein said first and second films each comprise styrene/butadiene copolymer at said interface.

9. The package set forth in claim 1, further mcluding an intermediate film positioned between said first and second films, said first and intennediate films being in direct contact with one another and defining an interface therebetween, at least one of said first and intemiediate films having a corona-treated surface located at said interface.

10. The package set forth in claim 9 wherein said first film contains therein an anti-fog additive and said intennediate film contains substantially no anti-fog additive.

11. The package set forth in claim 9 wherein said first and intermediate films are stretch- oriented films, each of said films comprising a polyolefin at said interface.

12. The package set forth in claim 9 wherein at least one of said first and intermediate films are not stretch-oriented and comprise at least one material selected from the group consisting of ethylene/vinyl acetate copolymer (EVA), etiiylene/methacrylate copolymer (EMA), acrylic acid copolymers, methyl acrylic acid copolymers, acrylic acid-modified EVA or EMA, anhydride-modified EVA or EMA, and syndic-tactic polymethyl pentene at said interface.

13. The package set forth in claim 9 wherein said first and intermediate films each comprise styrene/butadiene copolymer at said interface.

14. The package set forth in claim 1 wherein said second film is substantially gas- impermeable.

15. The package set forth in claim 14 wherein said substantially gas-impermeable film comprises at least one material selected from the group consisting of ethylene/vinyl alcohol copolymers, polyamides, vinylidene chloride copolymers, biaxially oriented nylon, biaxially oriented polyester, polyethylene terephthalate, and silicon oxide.

16. The package set forth in claim 1 wherein said reactively-modified surface is a corona- treated surface.

17. 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 modifiying the surface of at least one of said first and second films to form a reactively-modified surface and pressing the first and second films together, tliereby forming a laminate which is delaminatable at a peel force ranging from 0.001 pounds per mch to 2.5 pounds per inch; extending the laminate over tiie support member containing tiie product such that the first film is adjacent to tiie support member; and sealing the laminate to tiie support member.

18. A method as set forth in claim 17 further including the step of perforating the first film prior to pressing the first and second films together.

19. A method as set forth in claim 17 wherein said first film is a gas-permeable film.

20. A method as set forth in claim 17 wherein said step of sealing the laminate to the support member seals the first film portion thereof to the support member and peelably seals tiie second film portion to the first film portion.

21. A method as set forth in claim 17 further including the step of heating the first and second films substantially simultaneously with the step of pressing the first and second films together.

22. A method as set forth in claim 18 wherein the step of perforating the first film comprises electrostatically microperforating tiie first film.

23. The method set forth in claim 17 wherein said first and second films are in direct contact with one another and define an interface therebetween, said at least one corona-treated surface being located at said interface.

24. The method set forth in claim 23 wherein said first and second films are stretch-oriented films, each of said films comprising a polyolefin at said interface.

25. The method set forth in claim 23 wherein at least one of said first and second films are not stretch-oriented and comprise at least one material selected from the group consisting of ethylene/vinyl acetate copolymer (EVA), ethylene/methacrylate copolymer (EMA), acrylic acid copolymers, metiiyl acrylic acid copolymers. acrylic acid-modified EVA or EMA, anliydride-modified EVA or EMA. and syndiotactic polymethyl pentene at said interface.

26. The method set forth in claim 23 wherein said first and second films each comprise styrene/butadiene copolymer at said interface.

27. The method set forth in claim 17, further including an intennediate film positioned between said first and second fihns, said first and intermediate films being in direct contact with one another and defining an interface therebetween, at least one of said first and intennediate films having a corona-treated surface located at said interface.

28. The method set forth in claim 27 wherein said first film contains therein and anti-fog additive and said intennediate film contains substantially no anti-fog additive.

29. The method set forth in claim 27 wherein said first and intermediate films are stretch- oriented films, each of said fihns comprising a polyolefin at said interface.

30. The method set forth in claim 27 wherein at least one of said first and intermediate films are not stretch-oriented and comprise 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 at said interface.

31. Tlie method set forth in claim 27 wherein said first and intermediate films each comprise styrene/butadiene copolymer at said interface.

32. The method set forth in claim 16 wherein said second film is substantially gas- impermeable.

33. The method set forth in claim 32 wherein said substantially gas-impermeable film comprises at least one material selected from the group consisting of etiiylene/vinyl alcohol copolymers. polyamides, vinylidene chloride copolymers, biaxially oriented nylon, biaxially oriented polyester, polyethylene terephthalate, and sihcon oxide.

iUBSΪSTUIE SHEET (RULE 261

34. Tl e metiiod set forth in claim 17 wherein said reactively-modified surface is a corona- treated surface.