Patent Publication Number: US-2010129503-A1

Title: Packages for steam venting, and methods

Description:
This application is being filed on 15 Apr. 2008 as a PCT International Patent application in the name of Kapak Corporation, a U.S. national corporation, applicant for the designation of all countries except the US, and Robert Chadwick Flaherty, a citizen of the U.S., applicant for the designation of the US only, and claims priority to U.S. Provisional Patent Application No. 60/912,546, filed Apr. 18, 2007. 
    
    
     TECHNICAL FIELD 
     This disclosure generally relates to flexible polymeric packages having a venting arrangement to allow the release of pressure, such as upon heating. 
     BACKGROUND 
     A variety of items are marketed and enclosed within flexible bags, pouches, or package constructions. Examples include non-edible items, as well as edible items such as pet food, coffee, cookies, rice, salt, candies, etc. Many of these packages can be stored at room temperature. However, some items, such as vegetables, are best when stored chilled, e.g., frozen. 
     With today&#39;s fast-paced society, many end-users prefer items (e.g., foods,) that are quick and convenient to prepare. The microwave is now a mainstay in the American household for food preparation. The consumer desires food packaging that can be taken from the chilled environment, e.g., freezer, and that can be readily heated, e.g., microwave heated. 
     What is desired is a package that can be taken from a first temperature, such as a freezer, and then exposed to an elevated temperature, such as such resulting from heating in a microwave. Various constructions have been known for this application. Often, these packages include user interaction to provide a vent in the package to provide an escape for the increasing pressure. There is always room for improvements specifically eliminating the need for the end-user to interact with the package. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure is directed to generally flexible, polymeric packages that have a body and at least one venting arrangement present in a seal. The venting arrangement includes a water compatible coating that provides a vent from the interior of the package to the exterior, upon exposure of the coating to a fluid water source. The fluid water source (e.g., liquid water or vapor) solubilizes, dissolves or otherwise renders ineffective the coating, forming a fluid path from the interior of the package to the exterior of the package, thus allowing the escape of pressure from the package. The present disclosure is also directed to the roll stock used to make such packages. 
     In one particular aspect, this disclosure is directed to a flexible package having a flexible body having at least one seal and a venting arrangement extending through the at least one seal from the package interior, the venting arrangement comprising a water compatible coating. The at least one seal may be formed between a first portion of the body and a second portion of the body, so that the venting arrangement extends therebetween, or the at least one seal may be formed between a first panel and a second panel, so that the venting arrangement extends between those panels. 
     The body or panels of the package may be, for example, polyester, polyamide (nylon), polyethylene, polypropylene, copolymer or polymer blend, i.e., ethylene vinyl acetate (EVA), ethylene acrylic acid (EAA), or ethylene normal butyl acetate (EnBA). The material that forms the body or panels may include a coating or treatment to facilitate the formation of the resulting package. 
     The coating may include a starch, gum, sugars, or water soluble proteins, or other food grade coating, and may be present only in the seal area or may be present on the entire package interior, or portions thereof. 
     In another particular aspect, this disclosure is directed to a self-venting flexible package that has a first polymeric panel and a second polymeric panel, the first and second panels being sealed together to form an interior with an item therein. A venting arrangement comprising a water compatible coating extends from the interior between the first panel and the second panel, wherein the venting arrangement breaks when exposed to liquid or vapor water to release pressure from the interior of the package. The venting arrangement may break to release pressure, e.g., steam pressure. 
     The packages of this disclosure are particularly suited for storing and heating of food items therein, without the need for end-user intervention. 
     This disclosure is also directed to methods of using the packages, such as to heat items (e.g., food items). One particular method includes providing a self-venting package comprising a flexible body having at least one seal, the body defining a package interior with a food item therein, and a venting arrangement extending through the at least one seal from the interior, the venting arrangement comprising water compatible coating, heating the package to raise the temperature of the food item, such as creating steam under pressure on the interior of the package; and breaking the venting arrangement to release the pressure. The package is particularly adapted for heating in a microwave oven. 
     The package may be referred to as a “freezer to microwave” oven package. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  a schematic perspective view of a package according to this disclosure; 
         FIG. 1A  is a cross-sectional view of the package of  FIG. 1  taken along line A-A; 
         FIG. 2  is a schematic plan view of film stock used for making the package of  FIG. 1 ; 
         FIG. 3  is a schematic plan view of the film stock of  FIG. 2 , prior to incorporation into the package of  FIG. 1 ; 
         FIG. 4  is a schematic plan view of the package of  FIG. 1  venting pressure from its interior; and 
         FIG. 5  is schematic perspective view of a second embodiment of a package according to this disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The packages of this disclosure include a venting arrangement in a seal area where two polymeric film portions join. The venting arrangement includes a water compatible coating, which can be an adhesive coating, that provides a vent from the interior of the package to the exterior, upon exposure of the coating to a fluid water source. 
     Referring to the figures, a flexible package is illustrated in  FIGS. 1 and 1A . Package  10  includes a body  11  defined by a first panel  12  and an opposite second panel  14  that are connected by side edges  16 ,  17 ,  18 ,  19 . For clarity herein, in this orientation of package  10 , side edge  17  can be referred to as a bottom edge  17  and side edge  19  can be referred to as a top edge  19 . 
     Side panels  12 ,  14  and side edges  16 ,  17 ,  18 ,  19  define body  11  with a storage interior  15  therebetween. Various other configurations of body  11  are known and are suitable for packages in accordance with the principles of this disclosure. Storage interior  15  is configured for receiving an item, such as a foodstuff item or other item(s), for storage within package  10 . 
     In this embodiment, package  10  is a rectangular package, having four side edges. It is understood that other shaped packages are within the scope of this disclosure, e.g., triangular packages with three side edges, circular packages with one edge or tube-shaped packages with either a fin or lap seal as would be produced on a vertical or horizontal form fill and seal machine. 
     Side panels  12 ,  14  are flexible sheets, typically polymeric film. Examples of suitable films for use as panels  12 ,  14  are well known, and include polyester, polyamide (nylon), polyethylene (e.g., LDPE, HDPE), polypropylene, copolymer or polymer blends (e.g., ethylene vinyl acetate (EVA), ethylene acrylic acid (EAA), or ethylene normal butyl acetate (EnBA)) and the like. Multi-layered, e.g. co-extruded film or laminated materials may also be used. A laminated material can be any two or more dissimilar materials joined with an adhesive or extrusion laminated (e.g., biaxially oriented polyester or biaxially oriented polyamide joined to a polyethylene or polypropylene). 
     As provided above, side panels  12 ,  14  meet at bottom edge  17 , side edges  16 ,  18  and at top edge  19 . Any or all of edges  16 ,  17 ,  18 ,  19  may be seals or may be folds. In package  10  of  FIGS. 1 and 1A , each of edges  16 ,  17 ,  18  and  19  is a seal. In alternate embodiments, for example, one of side edges  16 ,  18  could be a fold and the other of side edges  16 ,  18  could be a seal. For example, one piece of film material could be folded to form panels  12 ,  14 , thus forming one folded side edge (e.g., side edge  16 ) and one sealed side edge (e.g., side edge  18 ). Top and bottom edges  17 ,  19  would also be seals. In an alternate configuration, a tube of material can be used, thus forming two folded side edges (side edges  16 ,  18 ). These various edge configurations are known in the art and any of these are suitable for package  10 . 
     Seals at edges  16 ,  17 ,  18 ,  19  may be adhesive seals or may be heat-welded seals, formed by the melting of panels  12 ,  14  together. 
     In accordance with this disclosure, at least one of side edges  16 ,  17 ,  18  and  19  includes a venting arrangement (not visible in this figure), which, upon activation, provides fluid communication from interior  15  of package  10  to the exterior of package  10 . 
     Referring to  FIG. 2 , a polymeric sheet suitable for body  11 , specifically suitable for either or both side panels  12 ,  14 , is illustrated. Sheet  20  includes edges  22 ,  23 ,  24 ,  25 , which define the shape and size of sheet  20 . Sheet  20  includes a base sheet  26 , and a coating  28  covering a portion of base sheet  26 . By the term “coating,” it is meant a material or layer that partially or fully covers, or coats, a surface, and in some situations also acts as an adhesive to provide or promote adhesion. 
     Coating  28  includes at least one coating that is compatible with water. By the term “compatible with water” or variations thereof, it is meant that the coating may be soluble in water, may be miscible with water, or that water hydrates the coating. The coating is non-toxic, and in preferred embodiments, the coating is edible or food-grade. Preferably, coating  28  is non-toxic, and in preferred embodiments, is edible or food-grade. 
     A variety of food-grade coatings or tacking agents may be present in coating  28 . Food grade starches are suitable for coating  28 . Starches, in a pregelatinized or non-pregelatinized form, hydrate in water and have good film-forming properties. Examples of suitable starches include tapioca dextrin K4484 and corn syrup solids (“N-Tack”) from National Starch &amp; Chemical Co. and instant starch B792, cooked starch B790, and maltodextrin M180, all from Grain Processing Corp. of Muscatine, Iowa. Other suitable materials include polysaccharide gums such as gellan gum, xanthan gum, gum arabic, and cellulose gum or mixtures thereof. An example of a cellulose gum is sodium carboxymethyl cellulose. Others include sugars and water soluble proteins. 
     Coating  28  may consist of the water compatible coating, or may include a binder or additive(s). That is, the “water compatible” coating may be present as 100% of coating  28 , or may be only a portion of the material used for coating  28 . For example, a material generally not known as a coating may be combined with the water compatible coating to provide coating  28 . Any binder or additive(s) may help to help plasticize or modify the surface tension of adhesive coating  28 . For example, ethylene acrylic acid (e.g., “MP4983” or “MP4990” ethylene acrylic acid from Michelman) may be combined with a water compatible coating (e.g., starch) to provide a suitable coating  28 . Polysorbate and propylene glycol are other examples of suitable additives. The amount of water compatible coating and any binder or additive(s) will depend on the specific coating and binders or additive(s) used. 
     Sheet  20  may include a coating (e.g., primer) or treatment thereon to facilitate forming of the desired package. For example, the surface energy of sheet  20  may be modified (e.g., by corona treating) to facilitate wetting of coating  28 . 
     Returning to  FIG. 2 , coating  28  is not continuous, but configured so that portions of base sheet  26  remain exposed. In many embodiments, at least  25 % of base sheet  26  remains exposed in the coated portion; that is, coating  28  occupies no more than 75% of base sheet  26  in the coated portion. In other embodiments, at least 75% of base sheet  26  in the coating portion remains exposed, so that coating  28  occupies no more than 25%. Other amounts of coverage, either in between, more coverage or less coverage, are acceptable in other embodiments. 
     In this illustrated embodiment, coating  28  is a series of parallel, discontinuous lines over the expanse of base sheet  26 . Other patterns for coating  28  may be used, such as patterns of lines (including continuous lines, wavy lines, intersecting lines), patterns of shapes (including polymeric shapes with filled centers or not, and random shapes), and combinations and variations thereof. Coating  28  is configured so that upon incorporation into package  10 , coating  28  extends through a side seal area, as described below. 
     Coating  28  is present in at least one of the areas that forms sealed side edge  16 ,  17 ,  18 ,  19  of package  10 . In  FIG. 2 , coating  28  is present in all of the areas that form side edges  16 ,  17 ,  18 ,  19  and, in addition, present in areas of base sheet  26  that form panels  12 ,  14 ; in this embodiment, the entire surface of sheet  20  has coating thereon. In another embodiment, coating  28  may be present in only select areas of base sheet  26 , e.g., those that form one or more of side edges  16 ,  17 ,  18 ,  19 . In these embodiments, coating  28  will be in register with the eventual size and shape of package  10 . In these areas where coating  28  is present, it may occupy no more than 75% of these areas. 
       FIG. 3  illustrates two sheets  20 , sheets  20 A,  20 B, each similar to sheet  20  of  FIG. 2 , positioned in preparation to form package  10 . Side edges  22 A,  23 A,  24 A,  25 A align with and overlap side edges  22 B,  23 B,  24 B,  25 B, respectively. In this resulting package, i.e., package  10  of  FIG. 1 , each of side edges  16 ,  17 ,  18 ,  19  will include seals made at side edges  22 A/B,  23 A/B,  24 A/B,  25 A/B. Coating  28  is of sufficient shape and size so that coating  28  extends through the seal at least one of side edges  16 ,  17 ,  18 ,  19 . Although not necessary, coating  28  of sheet  20 A intersects with coating  28  of sheet  20 B where sealed. In some embodiments, a non-water compatible adhesive may be used to facilitate sealing of side edges  22 A/B,  23 A/B,  24 A/B,  25 A/B. 
     Upon forming of seals between sheets  20 A,  20 B to form side edges  16 ,  17 ,  18 ,  19  of packages  10 , interior  15  is defined therebetween, where sheet  20 A is not sealed to sheet  20 B. Coating  28 , on either or both of sheets  20 A,  20 B, forms a path between interior  15  and the exterior of package  10 . 
     Package  10  is particularly suited for storing of items, such as frozen food items including vegetables, fruit, French fries, and the like, which are typically heated, e.g., in a microwave oven. Package  10  is configured to be “freezer to microwave”, in that package  10 , with frozen items within interior  15 , can be placed into a microwave oven and the items therein heated. Package  10  includes a venting arrangement that provides fluid communication from interior  15  to the exterior of package  10 . 
     In many embodiments, package  10  will be filled with items at a packaging plant, when the package is made. In some embodiments, package  10  may be filled after the package is made. Generally however, package  10  will be obtained by the consumer already filled with the items. 
       FIG. 4  illustrates package  10  venting from interior  15  to the exterior of package  10  via a venting arrangement present in side edges  16 ,  18 . Venting arrangement includes vents  30 , formed by coating  28 . In fact, vents  30  are caused by the lack of coating  28 . Vents  30  may be present where coating  28  on panel  12  contacts coating  28  on panel  14 , where coating  28  on panel  12  contacts panel  14 , or where panel  12  contacts coating  28  on panel  14 . Vents  30  are present between panel  12  and panel  14 ; vents  30  do not form within the interior of either panel  12 ,  14  (e.g., a laminated panel does not delaminate). 
     In use, when package  10  is filled with frozen items (e.g., vegetables) interior  15  includes cold air and crystals of ice (frozen water). As the temperature within interior  15  increases, the cold air warms and the ice eventually melts, possibly forming liquid water. Eventually, the temperature of the water within interior,  15  increases sufficiently, forming steam (vaporized water) within interior  15 . 
     As described above, coating  28 , a water compatible coating, forms a path between interior  15  and the exterior of package  10 . As a coating  28  comes into contact with fluid water (e.g., liquid or vapor water), coating solubilizes, dissolves rendered ineffective as an adhesive by the fluid water, the path from interior  15  to the exterior of package  10  is unhindered, thus forming vents  30 . Increased pressure within interior  15 , caused by the expanding air and steam, escapes from interior  15  via vents  30 . 
       FIG. 5  illustrates an alternate embodiment of a ventable package according to this disclosure. Package  10 ′ of  FIG. 5  is similar to package  10  of  FIGS. 1 and 1A  in having a body  11 ′ defined by a first panel and an opposite second panel that are connected by side edges  16 ′,  17 ′,  18 ′,  19 ′. In package  10 ′, side edges  16 ′,  18 ′ are folds and side edges  17 ′,  19 ′ are seals. Package  10 ′ includes a central seal  13 , which, in this embodiment, includes a venting arrangement. 
     Package  10 ′ is made, for example, by folding sheet  20  of  FIG. 2  to join edge  22  with edge  24 , and sealing together to form central seal  13 . Folded edges  23 ,  25  are sealed to themselves to form edges  17 ′,  19 ′, respectively. Coating  28  is of sufficient shape and size so that coating  28  extends through the seal at central seal  13  and optionally at edges  17 ′,  19 ′. Coating  28  forms a path between the interior and the exterior of package  10 ′ through central seal  13 . Package  10 ′, upon presence of fluid water and increased pressure therein, vents in the same manner as package  10 . 
     The above description and the attached drawings provide a description of various embodiments of a ventable, flexible package. It is understood that the various elements and details of the venting arrangement illustrated in the figures and/or discussed above are interchangeable among various package designs, and that variations of the various elements and details are within the scope of this disclosure. Additionally, the various elements and details of the venting arrangement can be used with generally any package having generally any sealing arrangement and/or sealing region configuration. Since many embodiments of the disclosure can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.