This disclosure generally relates to a material, article, and method for closing a food container, for example, a food container containing yogurt.
Individual portioned food products are often provided with a removable lid adhered to a packaging or food container. Each lid prevents the contamination and/or spoilage of the food product by hermetically sealing the food product inside the package. Conventionally, these lids have been constructed from metal based foils. More recently, however, a demand for plastic lids has risen due to heightened cost concerns and the increased demand for metal detection in sealed food containers.
Once sealed, the individually portioned food products are often sorted by wrapping large numbers of the individually portioned food products on pallets or carts. Often the wrapping is improved by heat shrinking the wrapping to the products on the pallets or carts. Unintentionally, the heat shrinking of the wrapping causes the wrapping to bind or otherwise adhere to tab portions of the seals or lids, which can result in the disruption of the hermetic seal upon removal of the heat shrink wrapping. This loss of the hermetic seal precludes the storage and sale of the food product and therefore results in an economic loss.
In one embodiment, a plastic laminate includes a barrier substrate that has a portion of a first major surface coated with a functional layer that comprises a thermoplastic adhesive and a release agent.
In another embodiment, the plastic laminate is manufactured by binding the functional layer to the barrier substrate.
In still another embodiment, a food container lid includes the plastic laminate.
In yet another embodiment, a food container can be closed by binding the plastic laminate, e.g., the food container lid, to a rim of the food container.
In another embodiment, a sealed food container includes a food product, a food container, and a plastic laminate adhered to and closing the plastic container.
For a more complete understanding of the disclosure, reference should be made to the following detailed description and accompanying drawings wherein:
While the disclosed articles and methods are susceptible of embodiments in various forms, there are illustrated in the drawings (and will hereafter be described) specific illustrative embodiments of the invention, and these drawings are not intended to limit the invention to the specific embodiments described and illustrated herein.
Herein is provided a material and method for hermetically sealing food containers that are not disrupted by wrapping with heat shrink films (e.g., LDPE) and later removal of the heat shrink film. The material includes a plastic laminate for sealing the food container and which forms a hermetic seal between the laminate and the container.
The articles and methods described herein may be understood more readily by reference to the following detailed description and the examples provided. It is to be understood that this invention is not limited to the specific components, articles, processes and/or conditions described, as these may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.
Ranges may be expressed herein as from “about” or “approximately” one particular value and/or to “about” or “approximately” another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another embodiment.
As shown in
As shown in
In some embodiments, the release agent or layer 205 can be disposed on the tab portion 102 and on a portion of the sealing portion 101 adjacent to the tab portion 102. This arrangement of the release agent or layer 205 can result from the process by which the adhesive and/or release agents are applied to the barrier substrate 201. For example, in one embodiment, the release layer 205 can be applied to the adhesive layer 203 using a flexographic printing process that generally prints bands or stripes on a sheet of the barrier substrate 201, for example, after the adhesive layer 203 has been applied. The bands or stripes of release layer 205 can have, for example, substantially uniform widths and can be, for example, substantially linear. Bands or stripes of release layer 205 having non-uniform widths and non-linear configurations are also contemplated. For example, in various embodiments, the bands or stripes can have non-uniform widths and/or can be non-linear, for example, to substantially correspond to the shape of the tab portion 102 and reduce and/or eliminate overlapping of the release layer 205 onto the sealing portion 101.
After the release layer 205 is printed onto the adhesive layer 203, a plurality of lids 101 can then be cut, for example, die cut, out of the sheet. For example, the lids can be cut such that the tab portions 102 of the lids 100 correspond to the portions of the sheet having the bands or stripes of release layer 205 printed thereon. In embodiments where the bands or stripes have generally uniform widths, the release layer 205 typically overlaps with the sealing portion 101 of the lid 100, adjacent to the tab portion 102.
In yet another embodiment, the thermoplastic adhesive or adhesive layer 203 can be confined to only the contact portion 300 of the sealing portion 101 such as to form a ring for sealing to a container as will be described in detail below.
Additionally, as shown in
Referring to
The functional layer 202 can include individual layers—i.e., the filler layer 207, the adhesive layer 203, and the release layer 205—as shown in
In various embodiments, the functional layer 202 can include, for example, an admixture of co-extruded components of the lid 100. For example, as can be seen in
The lid 100 can include, for example, the release agent or layer 205 disposed adjacent to the adhesive agent or layer 203 and is not in direct contact with the barrier substrate 201. Alternatively, the barrier substrate 201 can be coated with a thermoplastic adhesive and a release agent such that the thermoplastic adhesive coats only the sealing portion 101 of the barrier substrate 201 and the release agent is disposed directly on the barrier substrate 201, coating only the tab portion 102. Yet further, in another alternative, the barrier substrate 201 can be coated with a thermoplastic adhesive such that the thermoplastic adhesive coats only the sealing portion 101 of the barrier substrate 201 and the barrier substrate 201 can be exposed in the tab portion 102 as the barrier substrate 201 may be incompatible with shrink wrap film.
In addition to the materials described above, the plastic laminate 200 of the present disclosure can further include any one or more materials safe for contact with food products, for example, materials permissible for use by the U.S. Food and Drug Administration (FDA) under 21 C.F.R. §175(C) “Substances for use and components of coatings”; 21 C.F.R. §177(B) “Substances for use and basic components of single and repeated use food contact surfaces”; 21 C.F.R. §177(C) “Substances for use only as components of articles intended for repeated use” the contents of which are incorporated herein by reference to those materials.
The barrier substrate 201 can have a thickness in a range of about 0.0025 mm to about 0.125 mm, about 0.005 mm to about 0.1 mm, about 0.01 mm to about 0.09 mm, about 0.02 mm to about 0.08 mm, and/or about 0.03 mm to about 0.07 mm. For example, the barrier substrate 201 can have a thickness in a range of about 0.0127 mm to about 0.076 mm (e.g., a range of about 0.5 mils to about 3 mils). Other suitable thicknesses include, but are not limited to, about 0.0025 mm, 0.005 mm, 0.0075 mm, 0.01 mm, 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, 0.06 mm, 0.7 mm, 0.08 mm, 0.09 mm, 0.1 mm, and 0.125 mm.
The barrier substrate 201 can include a polymer, for example, selected from polyethylene terephthalate, polypropylene, polystyrene, polyester, foil, and a mixture thereof. In one embodiment, the barrier substrate 201 includes polyethylene terephthalate. In another embodiment the barrier substrate 201 consists essentially of polyethylene terephthalate. Herein, a barrier substrate 201 that consists essentially of polyethylene terephthalate means the barrier substrate 201 may include other materials that do not materially and adversely affect the characteristics of the polyethylene terephthalate as a barrier substrate 201. These other materials can include, for examples, primers, dyes, release agents, inks, coatings, pigments, inorganic lubricants, waxes and/or antiblocking agents.
The thermoplastic adhesive of the functional layer 202 can be, for example, a material selected from polyvinyl acetate (PVA), polyvinyl alcohol (PVA), polyacrylate (e.g., Poly(methyl methacrylate) (PMMA)), polyester acrylic resin, silicone resin, polyamine, and a mixture thereof. In one embodiment, the thermoplastic adhesive includes a polyethylmethacrylate and a high density polyethylene (HDPE). For example, the thermoplastic adhesive can be formed of distinct layers of the polyethylmethacrylate and HDPE or can be a coextrusion of the polyethylmethacrylate and HDPE. The thermoplastic adhesive can include the materials permissible for use by the FDA under 21 C.F.R. §175(B) “Substances for use only as components of adhesives”; 21 C.F.R. §175.300 “Indirect Food Additives: Adhesives and Components of Food”; and/or 21 C.F.R. §177.1520 “Indirect Food Additives: Olefin Polymers” the contents of which are incorporated herein by reference to those materials.
The thermoplastic adhesive is capable of sealing the plastic container 104 without significantly damaging the container 104 or the barrier substrate 201. Thermoplastic adhesives often require heating to a temperature above which the thermoplastic adhesive softens, e.g., the glass-transition temperature and/or the Vicat softening point (ASTM D1525) for the thermoplastic. Suitable thermoplastic adhesives for use in the present disclosure include those thermoplastic having a glass-transition temperature less than about 200° C., less than about 190° C., less than about 175° C., less than about 150° C., less than about 125° C., less than about 100° C., less than about 75° C., less than about 50° C., less than about 25° C., and less than about 0° C. may be suitable For example, LDPE can be used as the thermoplastic adhesive and has a glass transition temperature of approximately −78° C. or lower. Suitable thermoplastic adhesives for use in the present disclosure can also or alternatively having a Vicat softening point of less than about 200° C., less than about 175° C., less than about 150° C., less than about 125° C., or less than about 100° C. In other embodiments, thermoplastic adhesives having different glass-transition temperatures may be suitable.
The release agent can include, for example, a high temperature wax, including a wax having a melting point above about 150° C., above about 200° C., above about 250° C., or above about 300° C., The release agent can include, for example, a silicone, an organopolysiloxane, a silicone and siloxane copolymer, and a silicone and siloxane blend. Examples of silicone and siloxane copolymers and blends include, for example, mixtures of an organosiloxane and vinyl methyl ether-maleic anhydride copolymer, epoxypolysiloxane, polysiloxane titanate, and a polyurethane organosilicone blend. The release agent can include, for example, long chain branched polymers, including, for example, alkyacrylate-acrylic acid copolymer, stearyl methylacrylate-acrylonitrile copolymer, polypropylene copolymer, polystyrene copolymer, and strearic acid polyester-fomaldehyde resin. The release agent can include, for example, fluorocarbon polymers, such as perfluoronated polyesters, and perfluoroalkylacryaltes. The release agent can include any combination of the above-mentioned materials and can further include other components which meet the requirements of being incompatible with the shrink film, compatible with the adhesive, and, importantly, meet food regulatory requirements. One example of a material that can be used as the release agent is commercially available as MGS955 (Midwest Graphic Sales, Inc., IL).
As mentioned, the plastic laminate 200 can be for closing a food container 104 as shown in
Methods of applying the functional layer to the barrier substrate 201 include, for example, thermal lamination, adhesive lamination, solvent welding, extrusion coating, extrusion laminating, heat seal coating, roller coating, painting, spraying, and other known methods of forming, coating, and/or laminating films or sheets. The functional layer can be applied to the barrier substrate 201 uniformly. A method for forming uniform layers can include impregnation units, knife coating units, wire wound coating bars, roll coaters, spray coaters, size presses, nip presses, and the like. For example, the functional layer can be applied to the barrier substrate, for example, a corona treated barrier substrate, as an emulsion or solution at a coat weight of about 1 to about 1.5 lbs/ream (wherein a ream includes approximately 432,000 in2) and/or about 1.5 to about 4.0 grams per square meter. The coated barrier substrate can then be dried using standard IR and/or hot air driers.
As discussed above, the food container lid 100 of the disclosure, for example, can be cut from a larger sheet of the plastic laminate, and can have a symmetrically shaped body portion 101 and a tab portion 102 extending outwardly from a perimeter edge 101a of the body portion 101. The tab portion 102 is for grasping by a user for removal of the lid, as seen in
The food container 104 shown in
As discussed above, sealed food containers are often aggregated and secured by wrapping large numbers (e.g., equal to or greater than 6, 12, 24, 48, 96, or 192; typically 6 or 12) of the sealed food containers with a heat shrinkable wrapping and once secured, a high temperature is applied to the wrapping which shrinks and binds the sealed food containers to form a bundle of sealed food containers. For example, a pallet including the secured, sealed food containers can be passed through a processing oven so the wrapping is exposed to a temperature greater than, for example, 300° F., 350° F., 375° F., and/or 400° F., for a time less than about 30 sec, about 15 sec, about 7 sec, and/or about 6 sec. With conventional food container lids, the heat shrinking can activate or soften the thermoplastic adhesive disposed on the tab portion 102 of the lids 100, thereby causing the shrink wrapping to adhere to the food container lid. In circumstances where the wrapping adheres to the food container lid, the removal of the wrapping, for example for display or sale, can result in at least partial removal of the lid from the container and disruption in the hermetic seal between the lid and the food container. Such a disruption can preclude the sale of the food product, thereby resulting in lost profits. To overcome this problem with conventional lids, the present disclosure advantageously includes the presence of the release agent, which reduces or retards the adhesion of the shrink wrapping to the adhesive disposed on the food container lid. Specifically, the release agent effectively makes the functional layer 202 carried by the tab portion 202 of the lid 100 incompatible with the shrink wrapping, thereby reducing and/or eliminating the occurrence of 11d disruption and lost product associated with conventional lids.
While the disclosure has thus far described the lid 100 as being constructed primarily of a polymer, in alternative embodiments, the lid may be formed from a different material that may be a biodegradable material, such as molded fiber or pulp or paper. For example, the lids may be 100% post consumer fiber or pulp feedstock. In another example, the lids may be 100% recycled corrugated fiberboard and newspaper. The materials described herein can include, for example, virgin pulp fiber and can include type-2 molded fiber, type-2A thermoformed fiber, type-3 thermoformed fiber, type-4 thermoformed fiber, molded fiber, X-RAY formed fiber, infrared formed fiber, microwave formed fiber, vacuum formed fiber, structural fiber, sheet stock, recycled plastic or any other structural material (e.g., foil). Any of the materials that may be used to form the lid 100 may be used in any of the embodiments described herein.
Additionally, in some embodiments, the lids 100 may include an accelerator that helps promote degradation after use. Alternatively or additionally, additives can be included which help breakdown the intended content of the lids. For example, where the container is to carry oil, an additive can be included in the lid which helps breakdown oil over time, increasing the recyclable properties of the container. In some embodiments, the lid is made from materials that can be recycled, either completely or in part.
The foregoing description is given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as modifications within the scope of the invention may be apparent to those having ordinary skill in the art.
The benefit of priority of U.S. Provisional Application No. 61/387,559, filed Sep. 29, 2010, is hereby claimed and the entire contents thereof are incorporated herein by reference.
Number | Date | Country | |
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61387559 | Sep 2010 | US |