Disclosed herein is a flexible package having steam vent. Film is used as a bladder that expands in response to an increase in the internal pressure while contents of the package are micro-waved. A laser-scored or similarly-produced vent(s) is provided, for example via scoring of an oriented PET or OPP layer, such that at least a region of the package exhibits differential elasticity for the surface, where the package is intact under normal (frozen or refrigerated conditions) and expansion of the package occurs due to internal pressure (e.g., steam) that builds up during heating (e.g. micro-waving) and causes some portions of the surface fail thereby creating vents. More specifically, the pressure build-up stresses the film of the package causing it to stretch to the point that only the vent point(s) fails and causes holes to appear in the sealant film, thereby allowing the pressure/steam to escape.
It is known in the packaging industry that the use of ventable packaging, particularly packaging that is microwavable, is advantageous. Several techniques have been employed to facilitate venting, including labels that expose a vent hole (e.g., APC's Estersteam® and Avery's Flexis Steam), laser scoring, Vacsys™ as well as heat seal coatings and controlled lamination failures. There are, however, various advantages and disadvantages with these known techniques. For example, several of the techniques might preclude hermetic sealing or otherwise risk an open package. With respect to packages containing foodstuffs the presence of vents is further complicated when the packages must contain sauces without the risk of leaking. And, even when vents are provided, there remains a problem of controlling the size of a vent(s) on a consistent basis so as to assure a consistent product/package experience.
Although several embodiments described herein are directed to laser-scored packaging, it will be appreciated that alternative scoring techniques may be employed to achieve the same functionality in a package. With respect to laser-scored packages, scoring film is a technology that may be employed for steam venting. The patterns that may be used for scoring vary greatly from continuous scores to perforations. Key challenges in laser-scoring include: (a) difficulty in ensuring the package is hermetic, and remains so until use; (b) achieving a consistent location for venting, so as to avoid spillage while cooking, and providing a package that can be handled once heated; (c) consistently controlling the score depth from job to job in view of potential material variations; and (d) preventing the scored areas from tear propagation due to building pressure inside the package.
In the package embodiments disclosed herein an improved packaging film and system is disclosed. The packaging system also addresses key challenges found with other technologies. In particular, various embodiments of the system do not require an added label or coating resulting in higher costs and more complex manufacturing processes; and is not subject to tear propagation at or around the steam vent area. The disclosed embodiments result in a self-regulating vent hole size (i.e., higher temperature/pressure, greater vent hole size), yet maintain a hermetic package until use. And, the disclosed vent hole system can be incorporated it into an easy open mechanism.
Disclosed in embodiments herein is a microwavable package, comprising: an enclosure having one or more film surfaces; at least one film surface of the enclosure forming a portion of the enclosure, said film surface including at least one vent section, wherein the vent section includes a pressure-responsive vent along a scored or modified portion of the film surface.
Further disclosed in embodiments herein is a multi-layer film package, comprising: an enclosure formed substantially of a multi-layer structure with differently extensible layers (e.g., an oriented film layer laminated to a sealant film) said enclosure being filled with a microwavable material (e.g., foodstuff) which is sealed therein; and at least a portion of one film surface including a scored region across the oriented layer surface, said scored region having a surface deformation of variable depth, wherein the depth periodically extends through at least the oriented layer(s) of the film such that heating of the package contents causes expansion of the package and stretching of the film surface and thereby the creation of vent points at least where the scoring penetrated at least the oriented layer(s).
Also disclosed herein is a method of manufacturing a flexible film for use on a steam venting package, comprising: providing a flexible film; and scoring a layer of the flexible film to produce a layer of the film exhibiting a reduced extensibility relative to at least an adjacent layer of the flexible film, and thereby producing a pressure-responsive region of the film.
The various embodiments described herein are not intended to limit the disclosure to those embodiments described. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the various embodiments and equivalents set forth. For a general understanding, reference is made to the drawings. In the drawings, like references have been used throughout to designate identical or similar elements. It is also noted that the drawings may not have been drawn to scale and that certain regions may have been purposely drawn disproportionately so that the features and aspects could be properly depicted.
Although described relative to a packaging film surface in several of the following embodiments, it will be appreciated that the disclosed venting system may be incorporated into any package that employs or can be modified to include at least one film surface into which the venting system may be incorporated. Moreover, the term package is intended to include any of a number of configurations, shapes and sizes that may be used for the heating or preparation of foodstuffs as well as other materials, including bags (e.g., flat-bottomed and side-gusseted) and lidding materials. Furthermore, the various differently extensible substrates may include paper and cellophane (cellulose-based films) as well as various combinations of the materials disclosed herein.
Referring to FIGS. 1 and 2A-2C, depicted therein are top and cross-sectional views of the multi-layer film having one or more sealant layers plus at least an outer or top layer of an oriented material such as oriented polyester (PET), oriented polypropylene (OPP), or biaxially oriented Nylon (BON). Such films are produced and sold by a variety of companies, including Polyplex TFC, DuPont Mylar, SKC SP-65, and Flex F-PAP. The films may include separate oriented layers that are adhesive or extrusion laminated to an inner film or layer to provide a package structure with oriented PET or OPP, for example, laminated to a coextruded sealant film. In general, a sealant film is produced from a resin such as polyethylene and/or polypropylene that may be responsive to heating in order to bond or adhere to other layers. Further contemplated are combinations of sealant materials in the form of blends or layers of such materials. As will be described relative to alternative materials below, it is possible to employ a single material yet cause a top layer of the material to have a differential or reduced extensibility, and there by achieve the equivalent of a layered film having oriented materials.
In one embodiment, the film provides a differential score capability. Depicted along the surface of film 110 of
As illustrated in
Referring also to
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And, referring also to
Also contemplated as alternatives are the location of the vent scoring, such that the film wants to stretch. Typically this would be at the center of the bag or package, but other locations could be used. Moreover, the shape of the bag or packaging plays a roll, and the scoring is believed to be most advantageous be across a short package dimension. Typically the package wants to become a ball, so the short bag width is what wants to stretch more—i.e., a score perpendicular to short bag width. It is also contemplated that the thickness of the sealant film could be adjusted or variable so as to vary the time or strain necessary to cause stretching or opening of the vents.
As an illustration of alternative vent scoring or positions, reference is made to
A similar embodiment is illustrated in
In summary, disclosed in the figures is a an enclosure formed substantially of a multi-layer, oriented film structure 110, where the enclosure may be filled with a microwavable material (e.g., foodstuff) which is sealed therein. At least a portion of one film surface includes a laser-scored line across the PET coated surface, where the laser-scored line has a variable depth and/or width/size. In one embodiment described above, the depth of the laser scoring periodically extends through the oriented PET coating and into a lower layer(s) of the film such that heating of the package contents causes stretching of the film surface and the creation of vent points at least where the laser-scoring penetrated the PET coating.
Also contemplated is a method of manufacturing a steam venting package in accordance with the features described above. As illustrated in
As will be appreciated, various methods of manufacturing the flexible film, packages and, in turn packaging products, may be employed, be they formed entirely from flexible films or of combinations of rigid materials and flexible films, and the use or selection of a particular package or materials may be dependent upon the item to be packaged and the intended manner of use. Such a method would include providing a package enclosure with at least one surface formed of a multi-layer film, where at least one layer of the film includes a scored or worked region that has a reduced extensibility. The surface could be laser-scored over at least a portion of the surface to produce a differentially-scored line across the surface, where at least some of the laser-scored line penetrates into but not entirely through the underlying layer(s), thereby providing a weakened vent point where, upon expansion of the surface due to heating the vent point will fail prior to the surrounding material causing a vent to open in the surface.
Benefits of the disclosed vent design and easy opening package are that, after cooking, the package allows the consumer to tear down the length of the bag at the score line. It is also believed that the design will result in reduced sauce spillage due to the use of small vent points and the ability to position the vent points in the middle of the bag. Lastly, the disclosed package is believed to improve safety as the vents will not reseal causing implosion as the package cools, and the position of vent points can be controlled and located away from the ends where users grab the package.
It should be understood that various changes and modifications to the embodiments described herein will be apparent to those skilled in the art. Such changes and modifications can be made without departing from the spirit and scope of the present disclosure and without diminishing its intended advantages. It is therefore anticipated that all such changes and modifications be covered by the instant application.
This application claims priority under 35 U.S.C. §119 from the following U.S. Provisional Patent Applications, U.S. Ser. No. 61/493,682 for MICROWAVABLE FILM PACKAGE HAVING STEAM VENTING FEATURE, filed Jun. 6, 2011 by S. Holmen, and U.S. Ser. No. 61/499,119 for MICROWAVABLE FILM PACKAGE HAVING STEAM VENTING FEATURE, filed Jun. 20, 2011 by S. Holmen, both of which are hereby incorporated by reference in their entirety.
Number | Date | Country | |
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61493682 | Jun 2011 | US | |
61499119 | Jun 2011 | US |