WO2015103176A1

WO2015103176A1 - Simplified reclosure tray lidding

Info

Publication number: WO2015103176A1
Application number: PCT/US2014/072634
Authority: WO
Inventors: Kevin O. Henderson
Original assignee: Avery Dennison Corporation
Priority date: 2013-12-30
Filing date: 2014-12-30
Publication date: 2015-07-09
Also published as: US20150183564A1

Abstract

A resealable and disposable package assembly is described. The assembly includes a tray and a multilayer lid that are bonded to one another to initially seal the contents of the package. The package can then be easily opened by at least partially separating the lid and tray. The package can be reliably and effectively sealed by recontacting the previously separated portions to one another. Neither the lid nor the tray require die cutting.

Description

SIMPLIFIED RECLOSURE TRAY LIDDING

CROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the benefit of U.S. Provisional Application No. 61/921 ,610 filed December 30, 2014, which is incorporated herein by reference in its entirety.

FIELD

[0002] The present subject matter relates to a simplified reclosure system such as for food products packaged in a plastic tray with a resealable lid.

BACKGROUND

[0003] A wide array of resealable containers are known. Typically, a container such as in the form of a flexible bag or rigid walled housing, is provided with an opening that serves to provide access to the interior of the container. A lid or cover is positioned over the opening and bonded to the container, typically by heat sealing, to enclose and seal the container interior and its contents from the external environment. For bag type containers, a portion of the flexible wall of the bag may serve as the cover and be folded or otherwise positioned over an opening in the bag. A reseal feature enables the lid or cover, or a portion thereof, to be removed or otherwise repositioned so as to allow access to the interior of the container. After accessing the interior of the container, the lid or cover can be appropriately positioned over the opening and engaged with the container to thereby reseal the container.

[0004] Numerous strategies have been devised for the lid or cover to overlay a container opening and engage the container to thereby seal the interior of the container from the outside environment. An example of a sealing strategy is the provision of corresponding, e.g. male and female, engagement structures on the respective contacting surfaces of the container and lid. Another example is the use of a layer of a pressure sensitive adhesive on the contacting surfaces of the lid or cover, and/or the corresponding region of the container extending about the periphery of the opening. This latter strategy is widely used, particularly for disposable packaging as used for storing and preserving perishable items such as food in which it is desirable to minimize exposure to air.

[0005] As packaging technology developed, a variety of materials have been used in laminates for both containers and covers. It is well known to utilize certain materials in a laminate container and cover assembly, and to thermally bond such materials together in order to initially seal the resulting package.

[0006] If however, a resealable function is desired, it is generally not possible to effectively and reliably perform the resealing using the same materials as used for the initial thermal sealing of the container. As a result, artisans devised multi-layer laminate assemblies containing both heat sealing materials and pressure sensitive adhesives. An example of such an assembly is described in U.S. Pat. No. 3,454,210. In that patent, multilayer laminates are used in both a cover and a base assembly. A heat sealable layer between the cover and base thermally bonds the components together in an initial sealing operation. Upon removal of the cover, a layer of the cover then ruptures, thereby exposing the pressure sensitive adhesive. The lid can be resealed to the container by contacting the pressure sensitive adhesive to a corresponding face on the container. A similar strategy is also described in U.S. Pat. No. 7,422,782.

[0007] Although satisfactory in many respects, previous and currently known package assemblies require forming a region of weakened material typically in the cover which facilitates initial opening of the package. Typically, forming such weakened regions is performed by die cutting along an inner face of the cover. The die cutting or "kiss cutting" operation forms cuts or other weakened regions in only a portion of the thickness of the cover. Upon an initial opening of the cover, the cuts or weakened regions result in exposing a region of pressure sensitive adhesive around the perimeter of the cover which thereby enables resealing of the cover to the container. The kiss cutting is very critical due to narrow tolerances for the die cut depth. If cutting of the cover is performed too deep, one or more barrier layers in the cover may be

compromised, and potentially the cover itself may be cut or severed. If cutting of the cover is too shallow, a consumer may not be able to open the sealed package.

[0008] Accordingly, a need exists for a new package configuration and

manufacturing method which provides a reliably sealed package which can be resealed or closed after an initial opening operation, and which does not require the previously noted sophisticated kiss cutting operation. SUMMARY

[0009] The difficulties and drawbacks associated with previously known technologies are addressed in the present tray lidding, packaging, and related methods.

[0010] In one aspect, the present subject matter provides a resealable package assembly. The package assembly includes a lid and a tray. The lid comprises a polymeric substrate defining a sealing face, a heat seal layer, a release surface disposed between the sealing face of the substrate and the heat seal layer, and an adhesive layer disposed between the sealing face of the substrate and the heat seal layer. The lid is free of structurally weakened provisions.

[0011] In another aspect, the present subject matter provides a method for opening and resealing a previously heat sealed package. The package includes a lid and a tray. The lid has a polymeric substrate defining a sealing face, a heat seal layer, a release surface disposed between the sealing face of the substrate and the heat seal layer, and an adhesive layer disposed between the sealing face of the substrate and the heat seal layer. The lid is free of structurally weakened provisions. The lid and the tray are heat sealed to one another. The method comprises separating at least a portion of the lid from the tray within a heat seal region by separating the adhesive layer from the release surface in the heat seal region to thereby open the package. The method also comprises matingly contacting the adhesive layer with the release surface within the heat seal region to thereby reseal the package.

[0012] As will be realized, the subject matter described herein is capable of other and different embodiments and its several details are capable of modifications in various respects, all without departing from the claimed subject matter. Accordingly, the drawings and description are to be regarded as illustrative and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a perspective schematic view of an embodiment of a resealable package assembly in accordance with the present subject matter.

[0014] Figure 2 is a schematic partial cross sectional view of an exemplary first embodiment of the package assembly taken across line 2-2 in Figure 1 .

[0015] Figure 3 is a schematic partial cross sectional view of the first embodiment package assembly after an initial opening in accordance with the present subject matter.

[0016] Figure 4 is a schematic partial cross sectional view of an exemplary second embodiment of the package assembly taken across line 2-2 in Figure 1 .

[0017] Figure 5 is a schematic partial cross sectional view of the second

embodiment of the package assembly after an initial opening in accordance with the present subject matter.

[0018] Figure 6 is a schematic partial cross sectional view of an exemplary third embodiment of the package assembly taken across line 2-2 in Figure 1 .

[0019] Figure 7 is a schematic partial cross sectional view of the third embodiment of the package assembly after an initial opening in accordance with the present subject matter.

[0020] Figure 8 is a schematic partial cross sectional view of an exemplary fourth embodiment of the package assembly taken across line 2-2 in Figure 1 . [0021] Figure 9 is a schematic partial cross sectional view of the fourth embodiment of the package assembly after an initial opening in accordance with the present subject matter.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The present subject matter provides a simplified reclosure system, such as for food products packaged in a plastic tray with a resealable lid. The subject matter provides a unique laminate assembly for the lid which enables the lid to be used in resealable applications. The lid laminate includes (from bottom or underside, to the top or outer face) (i) a layer of a heat sealable coating, (ii) a layer of a pressure sensitive adhesive, (iii) a release surface, e.g. a release layer, and (iv) one or more plastic or polymeric substrates and/or barrier layers. Specifically, the lid is sealed to a

conventional tray (typically formed from nearly any conventional tray material) using heat sealing. The heat sealable coating, i.e., layer (i), forms a seal with the tray material. The lid thus maintains a seal for the package contents. After an initial opening of the lid such as by a consumer, the lid may be resealed or "closed" against the tray and retained closed by the layer of pressure sensitive adhesive, i.e., layer (ii), initially incorporated in the lid laminate. A significant advantage of the present subject matter is that the lid does not have to be die cut, kiss cut, or otherwise processed to include one or more weakened regions in the lid.

[0023] Additional details of each of the various aspects, components and materials are as follows. Heat Seal Layer

[0024] The heat seal (or sealable) layer or coating used in the present subject matter can be water-based or solvent-based. In certain embodiments and particularly for applications in which a lid is to be heat sealed to a tray or other component that is formed from amorphous polyethylene terephthalate (APET), the heat seal layer exhibits characteristics enabling formation of a heat seal to APET at 130° C at 40 psig/1 .5 seconds. In certain embodiments, the heat seal layer or coating is optionally clear or substantially so. In other embodiments, the heat seal layer has sufficient clarity that it is "see through." It will be appreciated, however, that the present subject matter includes heat seal coatings which are opaque or translucent. The heat seal coating if not clear or transparent can be colored and may exhibit a white, off-white, or nearly any other color.

[0025] In certain embodiments, a heat seal coating available from Jamestown Coating Technologies of Jamestown, Pennsylvania, under the designation 93783A has been found useful. Table 1 set forth below lists various physical characteristics and performance properties of the coating.

Table 1 - Jamestown 93783A Heat Seal Coating

[0026] The heat seal coating in Table 1 is noted by its supplier Jamestown Coating

Technologies as a water-based FDA 175.300 compliant heat seal coating that can be used on substrates such as aluminum and cellulosic substrates. The coating creates a bond at low sealing conditions.

[0027] The present subject matter includes the use of other heat seal materials. Such other heat seal materials may be used in combination with the noted Jamestown 93783A heat seal coating. And in other embodiments, the other heat seal materials can be used instead of the noted Jamestown 93783A heat seal coating.

[0028] The present subject matter also includes the use of heat seal coatings or layers which are in the form of thin, frangible polymeric films. Such films could be transferred via release liner to a desired surface or substrate region. An example of such a polymeric film is a heat activated thermoplastic dry film. A nonlimiting example of such a film is a dry film adhesive available from Lenderink Technologies of Belmont Ml under the designation LENDERICK DRY FILM ADHESIVE 200. It will be understood that the present subject matter is not limited to this, and includes a wide array of other heat seal materials.

[0029] Alternative and/or additional materials for the heat seal layer may in certain embodiments include, but are not limited to, the following film-forming materials used alone or in combination such as polyethyelene, metallocene catalyzed polyolefins, syndiotactic polystyrene, syndiotactic polypropylene, cyclic polyolefins, polyethylene methyl acrylic acid, polyethylene ethyl acrylate, polyethylene methyl acrylate, acrylonitrile butadiene styrene polymer, polyethylene vinyl alcohol, polyethylene vinyl acetate (also known as ethylene vinyl acetate (EVA)), polybutylene, polystyrene, polyurethane, polysulfone, polyvinylidene chloride, polypropylene, polymethyl pentene, styrene maleic anhydride polymer, styrene acrylonitrile polymer, ionomers based on sodium or zinc salts of ethylene/methacrylic acid, polymethyl methacrylates, cellulosics, polyacrylonitriles, and thermoplastic polyesters. In certain embodiments, polyethylene (PE) is used in the heat seal layer, and particularly, a blend of PE and EVA, such as for example, a blend of PE and EVA with special antiblock and antistatic additives. Another particular material for use in the heat sealing layer is glycol-modified polyethylene terephthalate (PETG). In certain versions of the present subject matter, a particular material for the heat sealing layer is linear low density polyethylene (LLDPE).

[0030] The thickness of the heat seal layer may vary according to requirements of the packaging assembly. Typically, the heat seal coating is applied at a coating weight less than 10 gsm and in certain embodiments, about 5 gsm. Typically, the thickness of the heat seal layer is from about 15 to about 90 microns and in certain embodiments from about 30 to about 60 microns. However, it will be appreciated that the present subject matter includes the use of heat seal layers having thicknesses less than or greater than these thicknesses.

[0031] The heat seal layer is designed to be activated at temperatures known to those skilled in the art. While the heat seal layer may activate at temperatures below those specified for activation, the heat seal layer is designed to activate at certain temperatures based on the substrate material. In certain embodiments, the heat seal coating activates at temperatures between about 60° C and 164° C. In particular embodiments, the heat seal coating activates at a temperature within a range of from 120° C to 140° C, and in certain embodiments at a temperature of 130° C. The bonding temperature of the heat seal material should not be such that the release layer or release material (described in greater detail herein) bonds to the adhesive. In many embodiments, pressure is also applied to the respective surfaces during heat sealing.

[0032] In certain embodiments, the heat seal material changes state upon heating and becomes a pressure sensitive adhesive or exhibits properties comparable to the pressure sensitive adhesives described herein. This type of heat seal material will bond to the tray but will release from the release surface.

Pressure Sensitive Adhesive

[0033] The lid includes an adhesive layer. In many embodiments, the adhesive layer is a pressure sensitive adhesive layer and the adhesive provides a tacky surface allowing a bond to another contacting surface. Particularly, the properties of the adhesive are such that the bond also provides a seal to prevent or at least significantly prevent the flow of air or other agents across the region of the adhesive. The adhesive layer may be a single adhesive layer or may be a multilayer adhesive.

[0034] A wide range of adhesives can be used in this layer so long as their properties and characteristics are consistent with the packaging requirements of the resulting assembly. The adhesive could be a hot melt pressure sensitive adhesive, such as for example a rubber-based or acrylic-based pressure sensitive adhesive. The adhesive could be a UV cured hot melt. The adhesive could be based on a rubber- based hot melt composition, a solvent rubber adhesive, a solvent acrylic adhesive, or a solvent polyurethane adhesive. The adhesive could be emulsion-based such as an emulsion acrylic adhesive. The adhesive could be a high solids type adhesive as known in the art. As noted, a wide array of adhesives could be used. Each of the aforementioned adhesives are preferably in the form of PSA's. An extensive selection of various pressure sensitive adhesives are disclosed in U.S. Pat. Nos. 5,623,01 1 ;

5,830,571 ; and 6,147,165; owned by the assignee of the present application, and incorporated herein by reference.

[0035] A particular pressure sensitive adhesive for use in the pressure sensitive adhesive layer is commercially available under the designation Fasson® S692N. The S692N adhesive is an acrylic emulsion based adhesive. Generally, this adhesive is a polymeric blend of butyl acrylate and 2-ethyl-hexyl acrylate monomers with various tackifiers and processing acids. Other pressure sensitive adhesives include, but are not limited to, emulsion acrylic adhesives and rubber-based hot melt adhesives. [0036] In still another embodiment, the adhesive composition for use in conjunction with the present subject matter is an acrylic emulsion polymer comprising at least one acrylate ester of an alcohol containing at least four carbon atoms, at least one partially water soluble comonomer and at least one polar comonomer. The polymers are formed in the presence of a mixture of nonionic and anionic surfactants and have a mean particle size of less than about 0.200 microns and a particle size range of about 0.15 microns to about 0.25 microns. Suitable alkyl acrylates includes, but are not limited to, butyl acrylate, 2-EHA and mixtures thereof. Suitable partially water soluble

comonomers include, but are not limited to, methyl acrylate, methyl methacrylate, and mixtures thereof. In one instance, acrylic acid is the polar comonomer and is utilized with another carboxylic acid such as methacrylic acid.

[0037] When utilizing a pressure sensitive adhesive, the adhesive is typically applied at a coat weight of about 18 gsm. Typically, for most adhesives, coat weights of from about 4 gsm to about 32 gsm could be used. The thickness of the pressure sensitive adhesive layer typically ranges from about 3 to about 40 microns and particularly from about 12 to about 20 microns. It will be understood, however, that the present subject matter includes lids or cover laminates using thicknesses greater than or lesser than these thicknesses for the pressure sensitive adhesive layer.

Release Layer

[0038] In certain embodiments of the present subject matter, the release surface (i.e. layer (iii)) may be a release layer. A wide variety of release materials such as those typically used for pressure sensitive tapes and labels can be used in accordance with the present subject matter, including silicones, alkyds, stearyl derivatives of vinyl polymers (such as polyvinyl stearyl carbamate), stearate chromic chloride, stearamides and the like. Fluorocarbon polymer coated release liners are also known but are relatively expensive. For most pressure sensitive adhesive applications, silicones are by far the most frequently used materials. Silicone release coatings have easy release at both high and low peel rates, making them suitable for a variety of production methods and applications.

[0039] Known silicone release coating systems consist of a reactive silicone polymer, e.g., an organopolysiloxane (often referred to as a "polysiloxane," or simply, "siloxane"); a crosslinker; and a catalyst. After being applied to the adjacent layer or other substrate, the coating generally must be cured to crosslink the silicone polymer chains, either thermally or radiatively (by, e.g., ultraviolet or electron beam irradiation).

[0040] Based on the manner in which they are applied, three basic types of silicone release coatings used in the pressure sensitive adhesive industry are known:

solventborne, waterborne emulsions, and solvent free coatings. Each type has advantages and disadvantages. Solventborne silicone release coatings have been used extensively but, because they employ a hydrocarbon solvent, their use in recent years has tapered off due to increasingly strict air pollution regulations, high energy

requirements, and high cost. Indeed, the energy requirements of solvent recovery or incineration generally exceed that of the coating operation itself.

[0041] Waterborne silicone emulsion release systems are as well known as solvent systems, and have been used on a variety of pressure sensitive products, including tapes, floor tiles, and vinyl wall coverings. Their use has been limited, however, by problems associated with applying them to paper substrates. Water swells paper fibers, destroying the dimensional stability of the release liner backing and causing sheet curling and subsequent processing difficulties.

[0042] Solventless silicone release coatings have grown in recent years and now represent a major segment of the silicone release coating market. Like other silicone coatings, they must be cured after being applied to the flexible liner substrate. Curing produces a crosslinked film that resists penetration by the pressure sensitive adhesive.

[0043] Informative descriptions of various release materials, their characteristics, and incorporation in laminate assemblies are provided in U.S. Pat. Nos. 5,728,469;

6,486,267; and US Published Patent Application 2005/0074549, owned by the assignee of the present application. It is also contemplated that various waxes known in the art could be used for the release material or utilized in the release layer.

[0044] The particular lid or lidding laminates of the present subject matter utilize release layers that are relatively thin. For example, a typical release layer thickness is from about 1 to about 4 microns. In certain embodiments, the thickness of the release layer is from about 1 to about 2 microns. However, it will be understood that the present subject matter includes the use of release layers having thicknesses greater or lesser than these thicknesses.

[0045] A particular release composition has been identified for use in the present subject matter. That release composition is SILPHAN S 50 M 10R13035 clear, available from Siliconature S.P.A. of Italy. Table 2 set forth below lists various properties of this release composition. Table 2 - Properties of SILPHAN S 50 M 10R13035

[0046] In other embodiments, the release material may include a low surface energy polymer such as TPX® FILM OPULENT™ commercially available from Mitsui

Chemicals America, Inc. The TPX® OPULENT film includes polymethylpentene. The present subject matter includes the use of other release materials.

[0047] In embodiments wherein the release surface is a release layer, the function between the release layer and the adhesive layer, e.g., layers (iii) and (ii) respectively, can be based upon poor adhesive bonding to a non-polar release surface. That is, an adhesive strength between the release surface (e.g. a release layer) and the adhesive layer is unequal to an adhesive strength between the adhesive layer and the heat seal layer. An example of this strategy is bonding between an emulsion acrylic adhesive on untreated biaxially oriented polypropylene (BOPP).

[0048] In certain embodiments, the release material exhibits barrier properties or barrier characteristics to prevent oxygen or odor transmission through that layer, or at least substantially hinder passage through that layer. Lid Material

[0049] The lid or lidding can be formed from a wide array of materials such as polyethylene terephthalate film, polyolefin film materials or paper, cardboard, or other paper-based materials. Representative materials for the lid include, but are not limited to, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), both oriented and nonoriented, and copolymers thereof. Another example of a potentially suitable film for the lid is a layer of polyvinyl chloride (PVC) and copolymers thereof. Additional materials include, but are not limited to, polyvinyl chloride (PVC), and ortho- phthalaldehyde (OPA). For many applications, PET is preferred.

[0050] The lid can be utilized at various thicknesses. The lid substrate can have a typical thickness of from about 12 to about 125 microns, and a particular thickness of from about 50 to about 100 microns. In certain applications, a thickness of about 75 microns is suitable. However, it will be appreciated that the present subject matter includes the use of other thicknesses.

[0051] Since the outer face of the lid will likely constitute the outermost surface, it is desirable that the material selected for the outer substrate, at least along this outwardly directed face, exhibit attractive printability characteristics.

[0052] Printability is typically defined by the sharpness and brightness of the image and by ink anchorage. The sharpness is closely related to the surface tension of the print surface. The ink anchorage is often tested by a tape test (Finat test: FTM21 ). In general, PVC is printable with a variety of inks intended to be used with PVC. In most occasions the inks are water-based (especially in the US) or designed for UV drying (especially in Europe). In general, all polyolefin films can be printed with UV inks after on-press corona treatment, PE being better than PP mainly on ink adhesion. For waterbased inks an additional primer or topcoat is preferred to achieve good ink anchorage. In many applications, it may be desired to provide decorative patterns on the tray and/or lidding.

[0053] The lid may include an optional printing layer disposed on an outer face of the lid or on an inner surface of the lid. The lid may include an optional printing layer disposed below the outer face on an inner surface of the lid. When providing print and/or decoration on a package or container, one may print the lidding or "trap" the printing with an over-laminate. In certain embodiments it may be useful to trap the printing or decoration in order to preserve or maintain desired aesthetics of the artwork, i.e., brightness and/or color tone. A typical practice is to reverse print the relatively thin over-laminate prior to joining the over-laminate to the heavier base lidding.

Additional Layers in the Lid

[0054] According to certain embodiments, the lid may include a barrier material layer to promote the sealing characteristics of the lid and resulting sealed lid and tray assembly. Typically, it is desirable for the barrier material to exhibit resistance to oxygen transport or diffusion through the material. This is particularly desirable for sealing applications involving certain foods. A wide range of barrier materials can be used for the barrier material layer. The selection of the barrier material(s) is largely dictated by the degree of sealing required and hence, by the contents for which the sealing assembly is to house. Representative materials for use in the barrier material layer include, but are not limited to, polyvinyl alcohol (PVOH) and ethylene vinyl alcohol (EVOH) polymers. A well known and preferred barrier material is polyvinylidene chloride (PVDC). It is also contemplated that nylon and various nylon-based polymers known in the art could be used. It is further contemplated that combinations of these materials could be used, and in particular, multiple films of these materials could be utilized. An excellent discussion of barrier materials and their characteristics is provided in US Patent Application Publication 2004/0033379, owned by the assignee of the present application. In certain embodiments, particular materials for the barrier material include PVDC, PVOH, EVOH, and combinations thereof. Additional nonlimiting examples of suitable barrier materials may include AIO_x, SiO_x, and G-Polymer available from Nippon Goshei (also known as Nippon Synthetic Chemical Industry Co., Ltd.) of Osaka, Japan. Another potentially suitable barrier material is BAREX® (acrylonitrile based copolymers) available from Velox GmbH of Hamburg, Germany.

[0055] The barrier material is typically utilized at relatively small thicknesses in various embodiments of the lid laminate. For example, the barrier material layer thickness is from about 1 to about 5 microns, and particularly from about 1 to about 3 microns in thickness. Again, it will be understood that the present subject matter includes the use of other thicknesses for the barrier material layer.

[0056] As noted, in certain embodiments the barrier material exhibits relatively low oxygen permeability. Particular maximum oxygen permeability is approximately 50 cc/m 24 hours. Most particularly, the oxygen permeability is 0.5 to 7 cc/m 24 hours. [0057] For certain applications, it is contemplated that the lid laminate of the present subject matter can be free of a barrier layer. However, many embodiments include a barrier layer.

[0058] As previously noted, an optional printing layer may be disposed on the previously described lid outer substrate. The printing layer serves to receive and retain one or more inks deposited on the printing layer. The ink(s) constitute indicia or other markings for the lid laminate and package assembly. The printing layer can be formed from a wide range of materials typically known to those skilled in the art. For example, a variety of polyvinyl alcohol (PVA) and cellulose-based materials can be used for the printing layer.

[0059] The printing layer typically ranges from about 3 to about 20 microns in thickness and particularly, from about 3 to about 8 microns in thickness.

[0060] As described herein, the lids or lidding of the present subject matter are free of any structurally weakened provisions such as die cuts, kiss cuts, scores, or other perforations that extend through only a portion of the thickness of the lid. As will be appreciated, such structurally weakened provisions are typically formed or provided in many previously known resealable packages and are often located within or proximate heat sealing (or heat sealed) regions of the package.

Tray

[0061] The term "tray" as used herein refers to an enclosure, container, housing, or package that provides an interior hollow region within which, food or other items can be stored. The interior of the tray can be accessible through one or more apertures or openings defined in the tray, such as in a wall of the tray. Alternately, the tray can be formed, particularly from a relatively rigid shape-retaining material such that the tray defines a recessed open interior region that is accessible through an opening or other access means formed in the tray. Particular forms of the tray in accordance with the present subject matter exhibit one or more relatively rigid walls formed and/or arranged about an opening that provides unobstructed access to the interior of the tray.

[0062] In many embodiments, extending about the periphery of the tray opening, is a lip or other structural member that defines a region for contacting and sealing with the previously described lid. Particularly, a layer of a heat seal material is disposed along a face or at least a region of the face of the lip for subsequent contact with the heat seal layer of the lid laminate during thermal bonding between the lid and tray. The heat seal material on the tray or lip thereof, may be the same or different than the heat seal material of the lid laminate.

[0063] Although a particular form of the tray is a rigid wall receptacle having the previously described lip, the present subject matter includes the use of flexible wall enclosures such as a bag, pouch, or packet.

[0064] The tray can be formed from nearly any suitable material that is used in heat sealed packaging. Nonlimiting examples of the tray material include polystyrene, amorphous polyethylene terephthalate, crystalline polyethylene terephthalate, polypropylene, polyethylene, and combinations thereof. Methods

[0065] Generally, the heat seal material used in the lid laminate is applied onto a layer of the pressure sensitive adhesive. The present subject matter provides several techniques for obtaining such a layered array. In one embodiment, the adhesive is applied as a cast coating and then dried. After sufficient drying, the heat seal material is applied to the adhesive layer such as by casting.

[0066] In another embodiment, the adhesive and the heat seal material are applied simultaneously through a multi-manifold coating die head. Some degree of interfacial mixing may occur. A strategy to control such mixing is to adjust the viscosity of the coatings and/or impart incompatibility between the adhesive and the heat seal material. An example of imparting incompatibility is by using a solvent-based adhesive and a water-based heat seal material.

[0067] In yet another embodiment, the heat seal material could be applied to a low surface energy carrier web and subsequently transferred to the adhesive layer via lamination. The carrier web would then be removed in another step or operation.

[0068] Figure 1 is a schematic view of an embodiment of a resealable package assembly 10 in accordance with the present subject matter. The package 10 comprises a multilayer lid 20 and a tray 100. The lid 20 encloses an interior 130 of the tray 100. As schematically shown in Figure 2 which illustrates an exemplary first embodiment of the package assembly, the lid 20 comprises a polymeric substrate 50 defining a sealing face 52, a release layer 60 disposed on the sealing face 52, an adhesive layer 70 disposed on the release layer 60, and a heat seal layer 80 disposed on the adhesive layer 70. The lid 20 is free of structurally weakened provisions such as scores, cuts, perforations, or the like that extend through a portion of the thickness of the lid 20. The lid 20 may optionally comprise one or more barrier layers 40, typically along a face of the substrate 50 opposite the sealing face 52. And, the lid 20 may also include one or more additional layers 30 such as a topcoat or over-laminate layer.

[0069] Referring further to Figure 2, a portion of the heat seal layer 80 is thermally adhered such as by heat sealing to an adjacent portion of the tray 100, such as for example, an upwardly directed surface of a tray lip or rim 1 10. The region of heat sealing between the lid 20 and the tray 100 is shown as a heat seal region 120.

[0070] Referring to Figure 1 , the package assembly 10 is shown during an opening operation. During opening, i.e., either an initial opening after heat sealing between the lid 20 and the tray 100, or a subsequent opening occurring after the initial opening, the lid 20 or a portion thereof is typically separated from the tray 100 by pulling the lid therefrom as depicted in Figure 1 by arrow A. During an initial opening of the package 10, the release layer 60 separates from the adhesive layer 70 in the heat seal region 120. Thus, the portion of the lid 20 separated from the tray 100 exhibits a peripheral region, i.e., the heat seal region on the lid 125, at which is exposed a portion of the release layer 60. The interior region along the underside of the lid 20 is the heat seal material 80. After separation of the lid 20 from the tray, a peripheral region of the heat seal layer 80 and the adhesive layer 70 remains with the tray 100 within the heat seal region 120.

[0071] Figure 3 schematically illustrates a cross-sectional view of the first embodiment of the resealable package assembly 210 after heat sealing and an initial opening. The package 210 comprises a lid 220 and a tray 300. The lid 220 comprises one or more outer layers 230, one or more barrier layers 240, one or more polymeric films or substrates 250, a release layer 260, an adhesive layer 270, and a heat seal layer 280. The lid 220 and the tray 300 were previously heat sealed to one another within the heat seal regions 320. After an initial opening of the package 210, for example to access an interior 330 of the tray 300, portions of the adhesive layer 270 and the heat seal layer 280 remain associated with, i.e., bonded with, the tray 100 within the heat seal region(s) 320.

[0072] Figures 4 and 5 schematically illustrate cross-sectional views of a second embodiment of the resealable package assembly 1 0721 0'. The difference between the first embodiment and this second embodiment of the resealable package assembly is that layers 60 and 70 are swapped in position such that after an initial opening of the package 21 0', for example to access an interior 330 of the tray 300, portions of the release layer 260 and the heat seal layer 280 remain associated with, i.e., bonded with, the tray 100 within the heat seal region(s) 320.

[0073] Figures 6 and 7 schematically illustrate cross-sectional views of a third embodiment of the resealable package assembly 1 0721 0". In this third embodiment, an applied release layer 60/260 is optional and the adhesive layer 70/270 is more preferentially adhered to the heat seal layer 80/280 than to the sealing face 52 of the substrate 50/250. Thus in the absence of a release layer 60/270, the sealing face 52 of the substrate 50/250 serves as the release surface and because the adhesive layer 70/270 is more preferentially adhered to the heat seal layer 80/280 than to the sealing face 52 of the substrate 50/250, after an initial opening of the package 21 0", for example to access an interior 330 of the tray 300, portions of the adhesive layer 270 and the heat seal layer 280 remain associated with, i.e., bonded with, the tray 100 within the heat seal region(s) 320.

[0074] Figures 8 and 9 schematically illustrate cross-sectional views of a fourth embodiment of the resealable package assembly 1 0"721 0"'. Like the third

embodiment, in this fourth embodiment, an applied release layer 60/260 is optional and in the absence of a release layer 60/270, the heat seal layer 280 serves as the release surface. However, unlike the third embodiment, the adhesive layer 70/270 is more preferentially adhered to the sealing face 52 of the substrate 50/250 than to the heat seal layer 80/280. Therefore, after an initial opening of the package 21 0"', for example to access an interior 330 of the tray 300, only the heat seal layer 280 remains associated with, i.e., bonded with, the tray 100 within the heat seal region(s) 320.

[0075] It will be appreciated that the present subject matter can be utilized with a wide array of container shapes, configurations, and arrangements and in no way is limited to the particular forms depicted in the referenced figures.

[0076] The various lids and/or lidding can be heat sealed to a tray or other container by techniques as known in the art. After sealing, the sealed assembly can be opened by at least partially separating the lid from the tray. Typically, such separating requires an opening force of less than 15 N/inch, particularly from about 0.1 N/inch to about 15 N/inch, and more particularly from about 2 N/inch to about 10 N/inch.

[0077] The present subject matter provides various laminate assemblies, trays, lids, packaging, adhesives and coatings, and related methods which when implemented in reclosable tray lidding configurations, do not require die cuts and the relative complexity associated with forming such die cuts. [0078] Many other benefits will no doubt become apparent from future application and development of this technology.

[0079] All patents, published applications, and articles noted herein are hereby incorporated by reference in their entirety.

[0080] As described hereinabove, the present subject matter solves many problems associated with previous strategies, systems and/or devices. However, it will be appreciated that various changes in the details, materials and arrangements of components, which have been herein described and illustrated in order to explain the nature of the present subject matter, may be made by those skilled in the art without departing from the principle and scope of the claimed subject matter, as expressed in the appended claims.

Claims

WHAT IS CLAIMED IS:

1 . A resealable package assembly, the package assembly including a lid and a tray, the lid comprising:

a polymeric substrate defining a sealing face;

a heat seal layer;

a release surface disposed between the sealing face of the substrate and the heat seal layer; and

an adhesive layer disposed between the sealing face of the substrate and the heat seal layer;

wherein the lid is free of structurally weakened provisions.

2. The resealable package assembly of claim 1 wherein the adhesive layer includes a pressure sensitive adhesive.

3. The resealable package assembly of any one of claims 1 -2 wherein an adhesive strength between the release surface and the adhesive layer is unequal to an adhesive strength between the adhesive layer and the heat seal layer.

4. The resealable package assembly of any one of claims 1 -3 wherein the release surface is a release layer.

5. The package assembly of claim 4 wherein the release layer includes silicone.

6. The resealable package assembly of any one of claims 1 -5 wherein the lid further comprises:

at least one barrier layer.

7. The resealable package assembly of claim 6 wherein the barrier layer exhibits an oxygen permeability of less than 50 cc/m²/24 hours.

8. The resealable package assembly of any one of claims 1 -7 wherein the heat seal layer activates at a temperature within a range of from 60° C to 164° C.

9. The resealable package assembly of any one of claims 1 -8 wherein the heat seal layer forms a heat seal to the tray at 130° C at 40 psig/1 .5 seconds.

10. The resealable package assembly of any one of claims 1 -9 wherein the structurally weakened provisions include a cut extending partially through a thickness of the lid.

1 1 . The resealable package assembly of any one of claims 1 -10 wherein after heat sealing of the lid to the tray, the package can be opened by separating at least a portion of the lid from the tray, the separating requiring an opening force of less than 15 N/inch.

12. The resealable package assembly of any one of claims 1 -1 1 wherein the lid is sealingly engaged to the tray.

13. The resealable package assembly of claim 12 wherein the lid is heat sealed to the tray.

14. The resealable package assembly of any one of claims 1 -1 1 wherein at least a portion of the lid is separated from the tray by separating the adhesive layer of the lid from the release layer of the lid.

15. The resealable package assembly of any one of claims 1 -14 wherein the release layer is disposed on the sealing face of the substrate adjacent to and in contact with the adhesive layer.

16. The resealable package assembly of claim 15 wherein the heat seal layer is adjacent to and in contact with the adhesive layer.

17. The resealable package assembly of any one of claims 1 -14 wherein the adhesive layer is disposed on the sealing face of the substrate adjacent to and in contact with the release layer.

18. The resealable package assembly of claim 17 wherein the heat seal layer is adjacent to and in contact with the release layer.

19. A method for opening and resealing a previously heat sealed package, the package including a lid and a tray, the lid having a polymeric substrate defining a sealing face, a heat seal layer, a release surface disposed between the sealing face of the substrate and the heat seal layer, and an adhesive layer disposed between the sealing face of the substrate and the heat seal layer, the lid being free of structurally weakened provisions, the lid and the tray being heat sealed to one another, the method comprising:

separating at least a portion of the lid from the tray within a heat seal region by separating the adhesive layer from the release surface in the heat seal region to thereby open the package; and

matingly contacting the adhesive layer with the release surface within the heat seal region to thereby reseal the package.

20. The method of claim 19 wherein the adhesive is a pressure sensitive adhesive.

21 . The method of any one of claims 19-20 wherein the lid and the tray are heat sealed to one another by:

contacting the heat seal layer of the lid with the tray in the heat seal region; and heating at least one of the lid and the tray within the heat seal region to a temperature of from about 60° C to 164° C.

22. The method of claim 21 wherein heating is performed at a temperature of 130° C.

23. The method of any one of claims 21 -22 wherein the lid and the tray are heat sealed to one another by also:

applying pressure to the lid and the tray during the heating.

24. The method of claim 23 wherein the lid and the tray are heat sealed to one another by heating to 130° C and applying 40 psig pressure.

25. The method of any one of claims 19-24 wherein separating requires an opening force of less than 15 N/inch.

26. The resealable package assembly of any one of claims 1 -3 wherein the release surface is the sealing face of the substrate.

27. The resealable package assembly of any one of claims 26-27 wherein the lid further comprises:

at least one barrier layer.

28. The resealable package assembly of claim 27 wherein the barrier layer exhibits an oxygen permeability of less than 50 cc/m²/24 hours.

29. The resealable package assembly of any one of claims 26-28 wherein the heat seal layer activates at a temperature within a range of from 60° C to 164° C.

30. The resealable package assembly of any one of claims 26-29 wherein the heat seal layer forms a heat seal to the tray at 130° C at 40 psig/1 .5 seconds.

31 . The resealable package assembly of any one of claims 26-30 wherein the structurally weakened provisions include a cut extending partially through a thickness of the lid.

32. The resealable package assembly of claim 26-31 wherein the adhesive layer is disposed on the sealing face of the substrate adjacent to and in contact with the heat seal layer.

33. The resealable package assembly of any one of claims 26-32 wherein after heat sealing of the lid to the tray, the package can be opened by separating at least a portion of the lid from the tray, the separating requiring an opening force of less than 15 N/inch.

34. The resealable package assembly of any one of claims 26-33 wherein the lid is sealingly engaged to the tray.

35. The resealable package assembly of claim 34 wherein the lid is heat sealed to the tray.

36. The resealable package assembly of any one of claims 26-33 wherein the adhesive strength between the sealing face of the substrate and the adhesive layer is less than the adhesive strength between the adhesive layer and the heat seal layer.

37. The resealable package assembly of claim 36 wherein at least a portion of the lid is separated from the tray by separating the adhesive layer of the lid from the sealing face of the substrate.

38. The resealable package assembly of any one of claims 26-33 wherein the adhesive strength between the sealing face of the substrate and the adhesive layer is greater than the adhesive strength between the adhesive layer and the heat seal layer.

39. The resealable package assembly of claim 38 wherein at least a portion of the lid is separated from the tray by separating the adhesive layer of the lid from the heat seal layer.