Patent Publication Number: US-2010129008-A1

Title: Laminate for a bag for flowable material having an oriented polypropylene, and a bag made therefrom

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation of PCT/US2009/004103 filed Jul. 15, 2009, having the same title, which claims priority from U.S. Provisional Patent Application Ser. No. 61/134,933 filed Jul. 15, 2008, having the same title, the entire disclosure of each of which is hereby incorporated by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     1. Field of the Disclosure 
     The disclosure relates in general to bags, and more particularly, to a laminate for a bag for flowable material having an oriented polypropylene. 
     2. Background Art 
     The use of bags for flowable material, such as liquids and syrups (among others), is known in the art. For example, wines are packaged in such bags which are then inserted into boxes (commonly termed bag-in-box wine packaging). A constant struggle with such packaging is to limit bag cracking that typically occurs during shipping and transport. Additionally, with certain products, it is necessary to limit the quantity of oxygen that is transmitted through the bag (typically quite significant for wine products). 
     One structure that is utilized comprises a three layer laminate comprising an EVOH cap layer, a BON core layer and a PE sealant layer. While this structure has been utilized, there is a need to provide a structure that has a material which has less susceptibility to flex cracking and which has a lower oxygen transmission rate. 
     It is an object of the present invention to improve the performance of bag laminate constructions. 
     It is another object of the present invention to improve resistance to flex cracking in laminate constructions for bags. 
     It is another object of the invention to reduce the oxygen transmission rate in laminate constructions for bags. 
     These objects as well as other objects of the present invention will become apparent in light of the present specification, claims, and drawings. 
     SUMMARY OF THE DISCLOSURE 
     The disclosure is directed to a bag for a flowable material comprising a plurality of walls coupled together by way of a plurality of seals to define a substantially fluid tight cavity. The plurality of walls each comprising a laminate structure comprising a sealant layer comprising a polyethylene material; a core layer comprising an oriented polypropylene material; and a cap layer comprising an EVOH material. 
     In a preferred embodiment, at least one of the layers further includes a metallized vapor deposited layer thereon. 
     In another preferred embodiment, the metallized vapor deposited layer is deposited on a side of the core layer. 
     In yet another preferred embodiment, the metallized vapor deposited layer comprises aluminum. 
     In another preferred embodiment, the metallized vapor deposited layer comprises one of the group consisting of: metals, PVDC, aluminum oxide and silicon oxide. 
     Preferably, the sealant layer further comprises: 1.8 mil thick 0.920 g/cc octene LLDPE (1.0 g/10 min MI). 
     In another embodiment, the core layer further comprises 0.70 mil thick oriented polypropylene material. 
     In yet another preferred embodiment, the core layer further includes a treatment applied thereto, wherein the treatment is selected from the group consisting of: plain, corona, plasma and chemical. 
     Advantageously, the cap layer may comprise a multi-sub-layer EVOH based layer. 
     In another preferred embodiment, the base of the EVOH layer comprises a propylene sub-layer. 
     In one such preferred embodiment, the EVOH layer includes a plurality of polyethylene sub-layers sandwiched around an EVOH sub-layer. 
     In another such embodiment, the EVOH layer comprises a plurality of sub-layers including, at least one vinyl acetate sub-layer, a plurality of polyethylene sub-layers and an EVOH sub-layer surrounded by the plurality of polyethylene sub-layers. 
     In one such embodiment, the EVOH layer comprises five sub-layers, including, in order, a first linear low density polyethylene sub-layer, a second linear low density polyethylene sub-layer, a third linear low density polyethylene sub-layer, an EVOH sub-layer, and a forth linear low density polyethylene sub-layer. 
     Preferably, the first linear low density sub-layer comprises a 0.55 mil 50% 12% VA (0.40 g/10 min MI)/50% 0.920 g/cc octene LLDPE (1.0 g/10 min MI) with anti-block, anti-oxidant, and slip additives. 
     Preferably, the second linear low density sub-layers comprise a 0.20 mil 100% 0.924 g/cc anhydride modified LLDPE (2.2 g/10 min MI). 
     Preferably, the third linear low density sub-layer comprises a 0.30 mil 29 mol % ethylene EVOH (3.8 g/10 Min MI). 
     Preferably, the EVOH sub-layer comprises a 0.20 mil 100% 0.924 g/cc anhydride modified LLDPE (2.2 g/10 min MI). 
     Preferably, the fourth linear low density sub-layer comprises a 0.55 mil 100% 0.920 g/cc octane LLDPE (1.0 g/10 min MI) with anti-block, anti-oxidant, and slip additives. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will now be described with reference to the drawings wherein: 
         FIG. 1  of the drawings is a top plan view of a bag having the laminate construction of the present invention; and 
         FIG. 2  of the drawings is a cross-sectional view of the laminate construction of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and described herein in detail a specific embodiment with the understanding that the present disclosure is to be considered as an exemplification and is not intended to be limited to the embodiment illustrated. 
     It will be understood that like or analogous elements and/or components, referred to herein, may be identified throughout the drawings by like reference characters. In addition, it will be understood that the drawings are merely schematic representations of the invention, and some of the components may have been distorted from actual scale for purposes of pictorial clarity. 
     Referring now to the drawings and in particular to  FIG. 1 , a bag  12  having a laminate structure  10  is shown. The bag comprises a conventional bag for flowable material (such as syrup, wine, fine powders, and the like). In the embodiment shown, a pillow type bag is shown which includes a plurality of walls  20 ,  22  and a plurality of seals, such as seal  24  which joins the walls to each other to define cavity  25 . In certain embodiments, a spout, such as spout  26  is disposed on one of the walls to provide fluid communication to the cavity. Typical sizes for such pillow type containers often range between 1 liter and 20 liters. Of course, this is not deemed as limiting the bag to a particular size, but, rather, is provided as exemplary of conventional sizes of such containers. 
     Of course, in other embodiments, a alternate bag construction can be utilized. For example, the laminate structure  10  can be used in association with other bag constructions, such as gusseted bags or bags that are formed from a number of different constructions with a number of different seals formed in any one of a number of different formats. In other words, the laminate is shown in an exemplary embodiment with the understanding that there is no limitation as to the configuration and structure of the bag with which the laminate is utilized. 
     With specific reference to the laminate structure, and as is shown in  FIG. 2 , the laminate structure comprises a sealant layer  30 , a core layer  32  and a cap layer  34 . The three layers are laminated together. In one embodiment, it is contemplated that the three layers are adhered to each other. For example, a two component solventless polyurethane adhesive system  41 ,  43  can be utilized between the layers. In other embodiments, the three layers may be thermally bonded together. Indeed, the particular manner in which the three layers are coupled together to form a laminate can be another mechanism altogether without departing from the scope of the invention. 
     In a preferred embodiment, the sealant layer (which comprises the product contact layer) comprises a polyethylene material. For example, in one specific embodiment, the material comprises a 1.8 mil thick 0.920 g/cc octene LLDPE (1.0 g/10 min MI) with anti-block, anti-oxidant and slip additives. Of course other polyethylene materials are contemplated for use as well. For example, a propylene based sealant layer can be utilized (homopolymer, impact copolymer, random copolymer or elastomer/plastomer). In certain embodiments, such a propylene based sealant layer can aid adhesion during thermal lamination processes. 
     The core layer  32  comprises an oriented polypropylene film (OPP). In one embodiment, 0.70 mil thick corona treatment/oriented polypropylene/heat sealable layer material is contemplated. In another embodiment, this layer may be metalized such that the structure may include a 2.1 minimum optical density aluminum layer. One manner of applying such a metallized layer comprises the use of metal vapor deposition on the film. Of course, other configurations of oriented polypropylene films are likewise contemplated for use. 
     It is contemplated that a number of different thicknesses can be utilized. Additionally, a number of treatments may be applied (plain, corona, plasma and chemical). Further, heat sealable layers can be added on either side of the OPP, or on both sides. Finally, other coatings can be added, in addition to aluminum, such as other metals, PVDC, aluminum oxide and silicon oxide. Additionally, the optical density can be varied as desired. 
     With continued reference to  FIG. 2 , the cap layer  34  comprises a EVOH material. In the embodiment shown, a five sub-layer co-extruded EVOH based layer is contemplated. The five sub-layers  51 - 55  comprise: (1) 0.55 mil 50% 12% VA (0.40 g/10 min MI)/50% 0.920 g/cc octene LLDPE (1.0 g/10 min MI) with anti-block, anti-oxidant, and slip additives; (2) 0.20 mil 100% 0.924 g/cc anhydride modified LLDPE (2.2 g/10 min MI); (3) 0.30 mil 29 mol % ethylene EVOH (3.8 g/10 Min MI); (4) 0.20 mil 100% 0.924 g/cc anhydride modified LLDPE (2.2 g/10 min MI); and (5) 0.55 mil 100% 0.920 g/cc octane LLDPE (1.0 g/10 min MI) with anti-block, anti-oxidant, and slip additives. Of course, other polyethylene layers are likewise contemplated for use. A propylene based cap layer can be utilized (homopolymer, impact copolymer, random copolymer or elastomer/plastomer). In certain embodiments, such a propylene based cap layer can aid adhesion during thermal lamination. More specifically, this would be applicable to just OPP (not MOPP) and the propylene based material would be added to layer  55  ( FIG. 2 ). 
     Advantageously, over the prior art EVOH/BON/PE material, the present disclosed embodiment has over a three-fold increase in flex crack resistance and over a two-fold improvement in oxygen transmission rate. As the OPP material has a lower modulus than the prior used BON, the thickness of this layer can be increased without affecting the bag modulus. 
     The foregoing description merely explains and illustrates the invention and the invention is not limited thereto except insofar as the appended claims are so limited, as those skilled in the art who have the disclosure before them will be able to make modifications without departing from the scope of the invention.