Abstract:
A high-clarity, cast polypropylene produce pouch with first and second sidewalls and a bottom panel joined to form a pouch wherein the first and second sidewalls and the bottom panel are formed from cast polypropylene. The bottom panel can be a bottom gusset panel. The first and second sidewalls and the bottom gusset panel can have edges joined by side welding or heat sealing. Zipper or slide closures can close the first and second sidewalls. A method for forming a high-clarity, cast polypropylene produce pouch comprises creating a polypropylene (PP) resin, passing the polypropylene (PP) resin through a cast extruding machine and extruding molten polypropylene (PP) to produced extruded polypropylene (PP), rolling the extruded polypropylene (PP) in a cooling roller, and applying a surface-modifying corona treatment to the extruded polypropylene (PP).

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to flexible containers. More particularly, disclosed herein is a flexible, self-standing produce pouch of high-clarity, cast polypropylene film for containing loose produce, particularly fruits and vegetables. 
       BACKGROUND OF THE INVENTION 
       [0002]    Prior art bags or pouches for fruits, vegetables, and other produce are often crafted from an extruded tube of thermoplastic film. The thermoplastic film is assembled by heat sealing and processed to yield a finished pouch. Processing steps commonly include hole punching, perforating, and potentially further manufacturing steps designed to produce a specified pouch. Pouches are commonly crafted with rectangular or tapered shapes. Some pouches have zipper or slide closures with engaging male and female strips that can be selectively engaged to seal the mouth of the pouch. Other pouches are designed for being tied or fastened in a closed configuration. Pouches can incorporate handles and can be vented to help preserve freshness and to permit rinsing. 
         [0003]    Produce pouches are commonly formed from coextruded and blown high and low density polyethylene, polyester, or polypropylene film, which may be laminated. The manufacturing process typically includes the step of sealing a bag by applying enough heat to the surface of the bag to melt the material and cause it to adhere to itself. 
         [0004]    To heat seal bags manufactured from coextruded polyethylene, the packaging industry developed a heat sealing mechanism under which a filament generates sufficient heat to reach the melting point of the material. The inside layer of material must melt while the outer layers must be cooled so that they do not melt and cause the bag to lose its shape. Cooling can be achieved by, for example, blasts of cold air following the application of heat. 
         [0005]    To avoid the manufacturing problems associated with heat sealing coextruded polyethylene, the packaging industry has used laminated film. Laminated film consists of layers of different material that are brought together. The layers may consist of such materials as polyethylene, polyester, paper, foil and polypropylene. The outside layer of laminated film can be a heat resistant material, such as polyester, or can be coated for heat resistance. The use of laminated film and high temperature jaws for heat sealing streamlines the manufacturing process. However, the laminated film is approximately three times the cost of coextruded polyethylene. 
         [0006]    The prior art has also recognized that it is desirable to have produce bags or pouches that are capable of standing up when filled. Self-standing bags are desirable for a number of reasons. For example, a principal display panel can then be caused to face consumers. Further, arranging the bags in a standing position takes less space, can prevent damage and loss to the contained goods, and can be more attractive to consumers. 
         [0007]    It is further known that retail produce merchandisers now seek high-clarity packaging for many commodities, including grapes, cherries, and other loose fruit and vegetable products. High-clarity pouches give a consumer a greater ability to view the contained goods and can increase the perceived cleanliness and quality of the fruit, vegetable, or other produce contained by the pouch. However, although desirable, high-clarity packaging can entail increased production costs. Of course, produce growers and shippers desire cost-effective packaging. Moreover, existing high-clarity constructions often do not tolerate changes in temperature well and suffer losses in clarity, strength, and durability, all quite undesirable to produce growers, shippers, sellers, and consumers. 
         [0008]    Accordingly, it will be recognized that a high-clarity packaging solution that is innovative in construction while remaining efficient in cost and demonstrating an ability to tolerate temperature variations with limited or no loss in performance would represent a useful advance in the art of produce packaging. 
       SUMMARY OF THE INVENTION 
       [0009]    With a knowledge of the present state of the art, the present inventors set forth with the basic object of providing a pouch for produce and other goods that provides a high-clarity packaging solution. 
         [0010]    A further object of embodiments of the invention is to provide a produce pouch with high-clarity characteristics that better tolerates temperature variations. 
         [0011]    An additional object of the invention is to provide a produce pouch that can be manufactured and sold with cost efficiency. 
         [0012]    Still another object of embodiments of the invention is to provide a high-clarity produce pouch that is capable of being self-standing when retaining goods. 
         [0013]    These and further objects and advantages of the present invention will become obvious not only to one who reviews the present specification and drawings but also to those who have an opportunity to experience an embodiment of the high-clarity, cast produce pouch disclosed herein in operation. However, it will be appreciated that, although the accomplishment of each of the foregoing objects in a single embodiment of the invention may be possible and indeed preferred, not all embodiments will seek or need to accomplish each and every potential advantage and function. Nonetheless, all such embodiments should be considered within the scope of the present invention. 
         [0014]    One will appreciate that the foregoing discussion broadly outlines the more important goals and features of the invention to enable a better understanding of the detailed description that follows and to instill a better appreciation of the inventors&#39; contribution to the art. Before any particular embodiment or aspect thereof is explained in detail, it must be made clear that the following details of construction and illustrations of inventive concepts are mere examples of the many possible manifestations of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]    In the accompanying drawing figures: 
           [0016]      FIG. 1  is a perspective view of a high-clarity, cast produce pouch pursuant to the present invention in a standing configuration; 
           [0017]      FIG. 2  is a view in front elevation of the high-clarity, cast produce pouch of  FIG. 1  in a collapsed configuration; 
           [0018]      FIG. 3  is a view in front elevation of a plurality of high-clarity, cast produce pouches as disclosed herein joined together by fasteners passed through their retaining strips; 
           [0019]      FIG. 4  is a view in left side elevation of the high-clarity, cast produce pouch of  FIG. 1  with the bottom gusset expanded and the pouch in a standing disposition; 
           [0020]      FIG. 5  is a top plan view of the high-clarity, cast produce pouch of  FIG. 1  in an open configuration; 
           [0021]      FIG. 6  is a bottom plan view of the high-clarity, cast produce pouch of  FIG. 1  in an open configuration; 
           [0022]      FIG. 7  is a top plan view of the high-clarity, cast produce pouch of  FIG. 7  in an open configuration during production; 
           [0023]      FIG. 8  is a perspective view of an alternative high-clarity, cast produce pouch pursuant to the present invention in a standing configuration; 
           [0024]      FIG. 9  is a perspective view of a further alternative embodiment of the high-clarity, cast produce pouch in a standing configuration; 
           [0025]      FIG. 10  is a view in front elevation of the high-clarity, cast produce pouch of  FIG. 9  in a collapsed configuration; 
           [0026]      FIG. 11  is a view in front elevation of a plurality of high-clarity, cast produce pouches as disclosed herein joined together by fasteners passed through their retaining strips; 
           [0027]      FIG. 12  is a view left side elevation of the high-clarity, cast produce pouch of  FIG. 1  with the bottom gusset expanded and the pouch in a standing disposition; 
           [0028]      FIG. 13  is a top plan view of the high-clarity, cast produce pouch of  FIG. 1  in an open configuration; 
           [0029]      FIG. 14  is a bottom plan view of the high-clarity, cast produce pouch of  FIG. 1  in an open configuration; 
           [0030]      FIG. 15  is a top plan view of the high-clarity, cast produce pouch of  FIG. 7  in an open configuration during production; 
           [0031]      FIG. 16  is a perspective view of another embodiment of the high-clarity, cast produce pouch in a standing configuration; 
           [0032]      FIG. 17  is a top plan view of an embodiment of the high-clarity, cast produce pouch with side welds in an open configuration during production; 
           [0033]      FIG. 18  is a top plan view of a further embodiment of the high-clarity, cast produce pouch with side welds in an open configuration during production; 
           [0034]      FIG. 19  is a top plan view of another embodiment of the high-clarity, cast produce pouch in an open configuration during production wherein a handle is disposed below the closure mechanism; 
           [0035]      FIG. 20  is a top plan view of still another embodiment of the high-clarity, cast produce pouch in an open configuration during production wherein a handle is disposed above the closure mechanism; and 
           [0036]      FIG. 21  is a flow chart of a production process for produce pouches according to the invention disclosed herein. 
       
    
    
       [0037]    The various notes, dimensions, and details on the drawings are incorporated herein by reference but should not be interpreted as limiting the invention in any manner. 
       DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0038]    The produce pouch disclosed herein is subject to a wide variety of embodiments. However, to ensure that one skilled in the art will be able to understand and, in appropriate cases, practice the present invention, certain preferred embodiments of the broader invention revealed herein are described below and shown in the accompanying drawing figures. 
         [0039]    Turning more particularly to the drawings, a produce pouch according to the present invention is indicated generally at  10  in  FIGS. 1 through 7 . There, the produce pouch  10  has a first sidewall  12 , a second sidewall  14  joined along its outboard, lateral edges to the first sidewall  12  to form side seams  20 , and a bottom gusset panel  16  joined at its ends by bottom seams  22  and at its longitudinal edges to the first and second sidewalls  12  and  14 . 
         [0040]    As best seen perhaps in  FIG. 7  where the pouch  10  is depicted in an open configuration prior to formation of the seams  20  and  22 , the first and second sidewalls  12  and  14  and the bottom gusset panel  16  can be integrally formed with the first sidewall  12 , the bottom gusset panel  16 , and the second sidewall  14  disposed in series. The first and second sidewalls  12  and  14  have body portions that are generally mirror images, each with a rectangular upper section and a tapered lower section. The bottom gusset panel  16  has a rectangular main section and pointed ends that taper at angles corresponding to the tapering of the lower sections of the first and second sidewalls  12  and  14 . The sidewalls  12  and  14  and the bottom gusset panel  16  can be joined to form the overall pouch  10  by, for example, heat sealing to create the side and bottom seams  20  and  22 . 
         [0041]    When the produce pouch  10  is in an open configuration as depicted in  FIGS. 1 and 4  through  6 , the bottom gusset panel  16  achieves a somewhat flattened configuration such that the panel  16  acts as a foot for enabling the produce pouch  10  to be disposed in a free-standing position. Prior to being filled with produce, the pouch  10  can be disposed in a flat configuration with the bottom gusset panel  16  folded longitudinally into a facing relationship. 
         [0042]    The produce pouch  10  has a mouth defined by the upper edges of the first and second sidewalls  12  and  14 . The mouth can be selectively closed by use of a zipper closure  18 . As seen, for example, in  FIG. 7 , the zipper closure  18  is formed by strips  18 A and  18 B that traverse substantially the entire length of the respective sidewall  12  and  14 . The strips  18 A and  18 B have mating, self-retaining profiles. The male and female profiles of the strips  18 A and  18 B can be connected to close the pouch  10  by pinching and sliding across the strips  18 A and  18 B along the length of the top edges of the first and second sidewalk  12  and  14 , and the strips  18 A and  18 B can be separated to open the mouth of the pouch  10  as is necessary to insert or remove produce. 
         [0043]    To permit air and liquid flow within and through the open inner volume defined by the first and second sidewalls  12  and  14  and the bottom gusset panel  16 , a plurality of vents  30  can be spaced over the sidewalk  12  and  14  and the bottom gusset panel  16 . In this example, the vents  30  comprise round through-holes, but it will be recognized that other shapes would be readily possible. In the depicted embodiment, however, vents  30  are not disposed over predetermined portions of the first and second sidewalk  12  and  14  such as upper and central segments thereof, to permit the application and display of display material  32 . 
         [0044]    Of course, the locations and content of the display material  32  can vary irnfinitely and can include, for instance, branding, product information, and pricing codes. Display material  32  can be centrally disposed on one or both sidewalk  12  and  14 , on the bottom gusset panel  16 , and potentially above the closure mechanism. 
         [0045]    Still further, a handle  24  can be cut through each of the first and second sidewalk  12  and  14  in aligned locations, such as adjacent to the upper edges thereof In this example, the handle  24  is disposed below the zipper closure  18 , but it could be disposed above the zipper closure  18  as shown and described hereinbelow. As seen in  FIG. 7 , a handle  24 A can be formed in the first sidewall  12 , and a handle  24 B can be formed in the second sidewall  14 . 
         [0046]    With further reference to  FIG. 3 , produce pouches  10  as taught herein can be initially provided with a retaining strip  26  that has a plurality of retaining apertures  28  longitudinally spaced therealong. A fastener  36 , such as a simple twist tie, can be passed through each of the aligned apertures  28  in a plurality of produce pouches  10  to retain the pouches  10  prior to separation and filling. The retaining strip  26  can be removable thereby to permit a separation of the retaining strip  26  from the remainder of a given pouch  10  and a separation of that pouch  10  from the remaining pouches  10 . In this example, as best seen in  FIG. 3 , the retaining strip  26  is detachably connected to the upper edge of the first panel  12  by a line of perforations  34 . With that, the retaining strip  26  can be selectively torn away. 
         [0047]    The first and second sidewalk  12  and  14  and the bottom gusset panel  16  are preferably formed as cast polypropylene (PP), which has been found by the present inventors toy provide a plurality of improved performance characteristics carrying forth the goals of the invention. By way of example and not limitation, cast polypropylene permits the sidewalk  12  and  14 , the bottom gusset panel  16 , and the produce pouch  10  in general to exhibit high clarity, good durability, and desired improvements in performance despite fluctuations in temperature. Moreover, the cast polypropylene sidewalls  12  and  14  and bottom gusset panel  16  exhibit high resistance to chemical caustics and solutes and are reusable as necessary. 
         [0048]    An alternative produce pouch  10  pursuant to the invention disclosed herein is depicted in  FIGS. 8 through 15 . The produce pouch  10  again has a first sidewall  12 , a second sidewall  14  joined along its outboard, lateral edges to the first sidewall  12  to form side seams  20 , and a bottom gusset panel  16  joined at its ends by bottom seams  22  and at its longitudinal edges to the first and second sidewalls  12  and  14 . The first and second sidewalk  12  and  14  and the bottom gusset panel  16  are again preferably formed as cast polypropylene (PP) due to its improved performance characteristics as discussed previously. 
         [0049]    As shown in  FIG. 15  where the pouch  10  is depicted in an open configuration prior to formation of the seams  20  and  22 , the first and second sidewalls  12  and  14  and the bottom gusset panel  16  can again be integrally formed with the first sidewall  12 , the bottom gusset panel  16 , and the second sidewall  14  disposed in series. As before, the first and second sidewalls  12  and  14  have body portions that are generally mirror images, each with a rectangular upper section and a tapered lower section. The bottom gusset panel  16  has a rectangular main section and pointed ends that taper at angles corresponding to the tapering of the lower sections of the first and second sidewalls  12  and  14 . The sidewalls  12  and  14  and the bottom gusset panel  16  can be joined to form the overall pouch  10  by, for example, heat sealing to create the side and bottom seams  20  and  22 . 
         [0050]    When the produce pouch  10  is in an open configuration as depicted in  FIGS. 9 ,  12 , and  13 , the bottom gusset panel  16  achieves a somewhat flattened configuration such that the panel  16  acts as a foot for enabling the produce pouch  10  to be disposed in a free-standing position. Prior to being filled with produce, the pouch  10  can be disposed in a flat configuration with the bottom gusset panel  16  folded longitudinally into a facing relationship. 
         [0051]    As in the embodiment of  FIGS. 1 through 7 , the produce pouch  10  has a mouth defined by the upper edges of the first and second sidewalls  12  and  14 . The mouth can be selectively closed by use of a slide closure  38 . As seen, for example, in  FIG. 15 , the slide closure  38  is formed by strips  38 A and  38 B that traverse substantially the entire length of the respective sidewall  12  and  14 . The strips  38 A and  38 B have mating, self-retaining profiles. The male and female profiles of the strips  38 A and  38 B can be connected to dose the pouch  10  by sliding a slider member  40  along the strips  38 A and  38 B, and the pouch  10  can be opened by sliding the slider member  40  in an opposite direction. 
         [0052]    A plurality of vents  30  are again spaced over the sidewalls  12  and  14  and, the bottom gusset panel  16  to permit air and liquid flow within and through the open inner volume defined by the first and second sidewalls  12  and  14  and the bottom gusset panel  16 . As before, the vents  30  comprise round through-holes. Vents  30  are not disposed over predetermined portions of the first and second sidewalls  12  and  14 , such as upper and central segments thereof, to permit the application and display of display material  32 . 
         [0053]    Again looking to  FIG. 11 , produce pouches  10  as taught herein can be initially provided with a retaining strip  26  that has a plurality of retaining apertures  28  longitudinally spaced therealong. A fastener  36  can be passed through each of the aligned apertures  28  in a plurality of produce pouches  10  to retain the pouches  10  prior to filling. The retaining strip  26  can be removable thereby to permit a separation of the retaining strip  26  from the remainder of a given pouch  10  and a separation of that pouch  10  from the remaining pouches  10 . Here, the retaining strip  26  is again detachably connected to the upper edge of the first panel  12  by a line of perforations  34  so that the retaining strip  26  can be selectively torn away. 
         [0054]    While the produce pouch illustrated in  FIGS. 8 through 15  is depicted without a handle  24 , it will be appreciated that a handle  24  could readily be incorporated. Indeed, a handle  24  could readily be disposed above or below the closure mechanism whether the closure mechanism comprises a slide closure  38  with a slider member  40  as illustrated in the current embodiment, a zipper closure  18  as in the embodiment of  FIGS. 1 through 7 , or any other closure mechanism. In theory, a handle  24  could be disposed above the closure mechanism, and a handle  24  could be disposed below the closure mechanism. For instance, in the embodiments of the produce pouch  10  illustrated in  FIGS. 16 and 19 , a handle  24 , which is formed by handle portions  24 A and  24 B, is disposed below the closure mechanism, formed in this case by a slider member  40  in combination with a slide closure  38  formed by the strips  38 A and  38 B. In the embodiment of  FIG. 20  where the produce pouch  10  is depicted in a pre-assembly open configuration, handle portions  24 A and  24 B are disposed distal to the closure mechanism formed by the slide closure  38  and the slider member  40  such that the handle  24  so formed is above the closure mechanism in the completed pouch  10 . 
         [0055]    Further embodiments of the produce pouch  10  are contemplated as in  FIG. 17  and  FIG. 18 , which depicts just one-half of a produce pouch  10 , where the pouch  10  again has a first sidewall  12 , a second sidewall  14  for being joined along its outboard, lateral edges to the first sidewall  12  to form side seams, and a bottom gusset panel  16  joined at its ends to form bottom seams and at its longitudinal edges to the first and second sidewalls  12  and  14 . Here, however, the side and bottom seams are formed by side welds  42  for joining the sidewalls  12  and  14  and the bottom gusset panel  16  to form the completed produce pouch  10 . The illustrated side weld construction for the produce pouch  10  thus forms a bag with welded side seals and a folded and welded bottom. As the die-cutting forms of  FIGS. 17 and 18  illustrate, the width of the side welds  42  can vary within the scope of the invention. For instance, as shown in  FIG. 17 , the side welds  42  could be 10 mm (approx. 0.4 inches) wide. As shown in  FIG. 18 , the side welds  42  could be narrower, such as 6 mm (approx. 0.24 inches) wide. The connections between the bottom gusset panel  16  and the first and second sidewalls  12  and  14  can be formed integrally as during the initial extrusion or other formation of the sidewalls  12  and  14  and the bottom gusset panel  16 . 
         [0056]    As noted previously, the first and second sidewalls  12  and  14  and the bottom gusset panel  16  are preferably formed as cast polypropylene (PP). As contemplated hereunder, the production process can proceed as shown schematically in  FIG. 21 . First, a resin blend can be created. The resin blend can be processed at an elevated temperature, such as 225-235° C. (or 437-455 ° F.). The preferred resin used hereunder can have additives and agents added, including one or more of an anti-blocking agent, a slipping agent, an antistatic agent, a nucleating agent, and a propylene carrier elastomer. This presently preferred resin formula seeks to achieve, among other things, longer shelf life of the polypropylene (PP) film, including during prolonged low-temperature storage of produce. 
         [0057]    The resin blend so formed can be passed through a cast extruding machine prior to undergoing molten plastic extrusion in an extruding step in the cast extruding machine and/or in a secondary extruding machine. The resulting product can then pass through a primary cooling roller, potentially followed by a secondary cooling roller. Gauge control can be undertaken to measure and confirm thickness and other parameters of the cooled and rolled product. A surface-modifying corona treatment can then be applied to the material, such as by use of a low temperature corona discharge plasma, to achieve desired surface energy characteristics of the polypropylene (PP) material. The resulting product can then be trimmed, wound, slit, and packed with the for sidewalls  12  and  14  and the bottom gusset panel  16  joined, such as by heat sealing, side welding, or any other effective practice. A 72-hour curing time can be provided prior to slitting. Printing can be applied as appropriate and may be done with high temperature ink where necessary. It will be understood that the processing time for the material will depend on, among other things, machine capacity. In one practice of the invention, for example, the full processing capacity is 22,000 pounds per 24 hour period. 
         [0058]    With certain details and embodiments of the present invention for high-clarity, cast produce pouch  10  disclosed, it will be appreciated by one skilled in the art that numerous changes and additions could be made thereto without deviating from the spirit or scope of the invention. This is particularly true when one bears in mind that the presently preferred embodiments merely exemplify the broader invention revealed herein. Accordingly, it will be clear that those with certain major features of the invention in mind could craft embodiments that incorporate those major features while not incorporating all of the features included in the preferred embodiments. 
         [0059]    Therefore, the following claims are intended to define the scope of protection to be afforded to the inventor. Those claims shall be deemed to include equivalent constructions insofar as they do not depart from the spirit and scope of the invention. It must be further noted that a plurality of the following claims may express certain elements as means for performing a specific function, at times without the recital of structure or material. As the law demands, these claims shall be construed to cover not only the corresponding structure and material expressly described in this specification but also all equivalents thereof that might be now known or hereafter discovered.