Abstract:
A non-foil mono-web liner for adhering to an inner surface of a paperboard body of a composite container, the liner comprising a polymer film web having an inner surface for facing an interior of the container and an outer surface for facing the paperboard body, a vapor-deposited coating of barrier material covering the outer surface of the polymer film web, a protective coating of polymer material covering the vapor-deposited coating of barrier material, and an inner heat seal layer covering the inner surface of the polymer film web and forming an innermost surface of the liner. The liner thus is structured and arranged so that when wrapped into a tubular shape with opposite edges of the liner overlapping each other, the edges are heat-sealable together via the inner heat seal layer.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to composite containers having impervious liners.  
         [0002]     Composite containers comprise wound paperboard container bodies lined by an impervious liner that provides a barrier against the passage of oxygen and/or moisture. In some applications, the liner must provide a high degree of barrier performance, which conventionally has been achieved by using metal foil-based liners. Typical foil-based liners are laminated structures such as {paper/foil/sealant}, or {sealant/foil/sealant}. Because it is a relatively costly component of the liner, it would be desirable to eliminate the metal foil layer, while still achieving high levels of barrier performance.  
       BRIEF SUMMARY OF THE INVENTION  
       [0003]     The present invention addresses the above needs and achieves other advantages by providing a composite container and a non-foil liner therefor, wherein the non-foil liner comprises a mono-web structure. By “mono-web” is meant that the liner includes only a single web of material that is pre-manufactured and supplied in the form of a roll of the material. This is in contrast to the prior-art liners described above, wherein, for example, a paper web and a metal foil web are both pre-manufactured and supplied in roll form, and are drawn from their respective rolls and laminated together during the liner manufacturing process. In a mono-web manufacturing process, a single web is drawn from a supply roll and the web is then processed to apply various layers to the web via processes such as vapor deposition and/or extrusion coating.  
         [0004]     In accordance with one embodiment of the invention, a non-foil mono-web liner is provided for adhering to an inner surface of a paperboard body of a composite container, the liner comprising a polymer film web having an inner surface for facing an interior of the container and an outer surface for facing the paperboard body, a vapor-deposited coating of barrier material covering the outer surface of the polymer film web, a protective coating of polymer material covering the vapor-deposited coating of barrier material, and an inner heat seal layer covering the inner surface of the polymer film web and forming an innermost surface of the liner. The liner thus is structured and arranged so that when wrapped into a tubular shape with opposite edges of the liner overlapping each other, the edges are heat-sealable together via the inner heat seal layer.  
         [0005]     In another embodiment, the liner further comprises an outer heat seal coating covering the protective coating of polymer material and forming an outermost surface of the liner, whereby the opposite edges of the liner are lap-sealable wherein the outer heat seal coating on one edge is heat-sealed to the inner heat seal layer on the other edge.  
         [0006]     Advantageously, the liner further comprises a coating of a polymer material applied to the outer surface of the polymer film web prior to application of the vapor-deposited coating of barrier material for enhancing effectiveness of the vapor-deposited coating of barrier material. The polymer material can be selected from the group consisting of acrylate, polyvinyl alcohol, and ethylene vinyl alcohol.  
         [0007]     The protective coating for the barrier material layer can be selected from the group consisting of nitrocellulose lacquer, acrylic lacquer, and vacuum acrylate.  
         [0008]     The vapor-deposited coating of barrier material can comprise a metal in substantially pure non-oxide form (e.g., aluminum), a metal oxide (e.g., aluminum oxide), or a silicon oxide.  
         [0009]     When particularly high barrier performance is required, the liner can comprise a second vapor-deposited coating of barrier material covering the protective coating, and a second protective coating of polymer material covering the second vapor-deposited coating of barrier material.  
         [0010]     The invention also provides a composite container having a non-foil mono-web liner as described above. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       [0011]     Having thus described the invention in general terms, reference will now be made to the accompanying drawings, which are not necessarily drawn to scale, and wherein:  
         [0012]      FIG. 1  is an exploded perspective view of a container in accordance with one embodiment of the invention;  
         [0013]      FIG. 2  is a cross-sectional view through the container body, along line  2 - 2  in  FIG. 1 ;  
         [0014]      FIG. 3  is a cross-sectional view, on an enlarged scale, showing a liner in accordance with one embodiment of the invention;  
         [0015]      FIG. 4  is a view similar to  FIG. 3 , showing another embodiment of the invention;  
         [0016]      FIG. 5  is a cross-sectional view of yet another embodiment of the invention; and  
         [0017]      FIG. 6  is a cross-sectional view of still another embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0018]     The present inventions now will be described more fully hereinafter with reference to the accompanying drawings, in which some but not all embodiments of the inventions are shown. Indeed, these inventions may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Like numbers refer to like elements throughout.  
         [0019]     With reference to  FIGS. 1 and 2 , there is shown a composite container  10  having a non-foil-based liner in accordance with one embodiment of the present invention. Although illustrated as having a circular cross-section, the tubular container  10  may have any cross-sectional shape that can be formed by wrapping the composite materials around an appropriately shaped mandrel. For example, the tube can be formed in a rectangular shape with rounded comers by convolutely wrapping the materials around a suitably shaped mandrel. The embodiment illustrated in  FIG. 1  is particularly advantageous for packaging potato crisps or chips and includes a flexible membrane lid  11  and a reusable plastic end cap  12  over the membrane lid. Various other end closures may be used, however, depending upon the type of product that is to be packaged. For example, where dough is to be packaged, the end caps are typically constructed of metal and are crimp-sealed onto the ends of the container.  
         [0020]     The tubular container  10  includes a wall having one or more body plies  13  ( FIG. 2 ) preferably formed of paperboard and a liner ply  14  adhered to the inner surface of the body ply or plies  13 . The upper end of the tubular container  10  is rolled over so as to form a bead  15  or flange and the membrane lid  11  is hermetically sealed to the top of the bead. The end cap  12  is then snapped over the bead  15  and may be reused after the membrane lid  11  has been removed. A metal closure (not illustrated) can be secured to the opposite end of the container  10 . Alternative closure systems can be used at the container ends. For instance, the top closure can employ a metal ring in conjunction with a membrane lid sealed to the ring.  
         [0021]     The seams where the various plies are joined together are illustrated in  FIG. 2 . In some types of containers such as self-opening containers (e.g., for refrigerated dough), a single body ply is used and the edges of the ply are first skived and then joined together during the tube-forming process with an adhesive to create a strong seam. In other types of containers, a single or multiple body plies may be used and the edges of the ply or plies are not skived and form a butt joint as shown in  FIG. 2 , or form an overlap joint. In any event, the liner ply  14  is adhered to the inner surface of the body ply or plies  13  with a wet adhesive  21  and the overlapping edges of the liner ply are sealed together to ensure that the container  10  is completely sealed. A label ply  22  is adhered to the outer surface of the body ply  13  with an adhesive  23 , and can have various graphics and/or indicia printed thereon regarding the product within the container.  
         [0022]     The liner ply  14  includes a seal formed by overlapping a first edge portion  25  of the liner with an opposite second edge portion  26  of the liner and sealing the overlapping edge portions together. Likewise, the label  22  includes a seal formed by overlapping a first edge portion  27  with an opposite second edge portion  28  of the label and sealing the edge portions together. The liner and label are both shown in  FIG. 2  with fold seals, but alternatively, the liner and/or label can be seamed with a simple lap seal if their structures permit lap seals.  
         [0023]     A liner structure in accordance with a first embodiment of the invention is schematically depicted in  FIG. 3 . The liner  14  is free of any metal foil layers. The liner comprises a mono-web structure, as that term was previously defined. Thus, a single web  46  that is pre-manufactured is employed in the liner. The web  46  comprises a polymer film. The web  46  can comprise various polymers, including but not limited to polyethylene, polypropylene, polyester such as polyethylene terephthalate, nylon, and the like. To an outer surface of the web  46  is applied a layer of barrier material  48 . The layer  48  is vacuum- or vapor-deposited on the outer surface of the web  46  (i.e., the surface that faces the paperboard body plies  13  of the container, see  FIG. 2 ), which serves as the substrate for the barrier layer. In one embodiment, the layer  48  comprises a substantially pure metal in non-oxide form. Various metals can be used, but aluminum is most commonly employed. Alternatively, the layer  48  can comprise a metal oxide such as aluminum oxide, or a silicon oxide. Processes for vapor-depositing metals or oxides on polymer film are well known and are not further described herein.  
         [0024]     A coating  42  of a protective polymer material is applied to the barrier layer  48  to protect it. The polymer material can be selected from the group consisting of nitrocellulose lacquer, acrylic lacquer, and vacuum acrylate.  
         [0025]     The liner also includes a sealant layer  44  disposed on an inner surface of the web  46 . The sealant layer  44  comprises a heat seal material. Various heat seal materials may be used, including but not limited to ionomer resins (e.g., SURLYN®, an ethylene acid copolymer with acid groups partially neutralized with zinc or sodium ions), high-density polyethylene (HDPE), low-density polyethylene (LDPE), coextruded film structures (e.g., ionomer/HDPE coex, LDPE/HDPE coex, etc.). The particular sealant material is not of importance to the present invention.  
         [0026]     The liner  14  shown in  FIG. 3  has a heat seal material  44  on only one surface of the liner. Accordingly, to form a liner seal, a fold seal is necessary, as shown in  FIG. 2 . More particularly, one edge of the liner is folded over to place the sealant layer  44  on the folded edge portion in contact with the sealant layer  44  on an opposite unfolded edge of the liner, and the overlapping edges are heat-sealed together. Preferably an adhesive (not shown) is applied by a suitable applicator between the folded edge portion and the surface of the liner upon which the folded edge portion is folded, so as to ensure that the edge portion does not unfold during the spiral winding process.  
         [0027]     An alternative liner  14 ′ in accordance with the invention is shown in  FIG. 4 . The liner  14 ′ has a single polymer film web  46  and a sealant layer  44  disposed on the web&#39;s inner surface as in the previous embodiment. However, prior to vapor deposition, the outer surface of the web  46  is coated with a coating  43  of a material for enhancing the uniformity of vapor deposition of the barrier material  48 . The coating  43  can comprise a polymer selected from the group consisting of acrylate, polyvinyl alcohol, and ethylene vinyl alcohol. As an alternative to the use of the coating  43 , the outer surface of the web  46  can be treated by plasma discharge or the like, for enhancing the uniformity of vapor deposition.  
         [0028]     Yet another embodiment of the invention is shown in  FIG. 5 . The liner  14 ″ has a single polymer film web  46  and a sealant layer  44  disposed on the web&#39;s inner surface, a vapor-deposition-enhancing coating  43  on the web&#39;s outer surface, a vapor-deposited barrier layer  48  applied to the coating  43 , and a protective coating  42  applied over the vapor-deposited layer  48 , as in the liner of  FIG. 4 . In addition, a second vapor-deposited coating  51  of barrier material is applied over the protective coating  42 , and a second protective coating  52  of polymer material is applied over the second vapor-deposited coating  51  of barrier material. This liner structure is particularly useful when relatively high levels of barrier performance are needed.  
         [0029]     The above-described liner structures have a sealant layer  44  on only one surface of the liner.  FIG. 6  depicts a liner  114  generally corresponding to that of  FIG. 3 , but having a second sealant layer  54  covering the protective coating  42  and forming the outermost surface of the liner. The liner  114  is advantageous in that it can be lap-sealed as opposed to fold-sealed. The liners of  FIGS. 4 and 5  likewise can include such a second sealant layer to make them lap-sealable, if desired.  
         [0030]     Many modifications and other embodiments of the inventions set forth herein will come to mind to one skilled in the art to which these inventions pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the inventions are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.