Patent Publication Number: US-2010111453-A1

Title: Two Side Cut Reseal With Pressure Sensitive Adhesive and the Method for Making Same

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a flexible bag formed on a vertical form fill, and seal machine having a resealable opening near the top, and the method for making same. The invention allows for use of existing packaging technology to produce a flexible package with adhesive capable of resealing an opening in the bag without disturbing food products at a low cost. 
     2. Description of Related Art 
     Snack foods and other items are often packaged in bags formed from thin, flexible packaging films. These thin films are formed primarily of plastics, such as polypropylene and polyethylene, but can also contain metalized films, foil, paper, or oriented films. These packaging films can have numerous layers directed to achieving specific needs, but are generally formed at least in part by extrusion of a plastic layer, co-extrusion of multiple layers simultaneously, extrusion coating of another material (such as paper), and the lamination of two layers together via either extrusion lamination or adhesive lamination. The packaging film used in such process is typically a composite polymer material produced by a film converter. 
     A typical film  100  ideally suited for use on vertical form and fill machines for the packaging of food products is seen in  FIG. 1 . The outer layer  102  is typically an OPP layer, short for oriented polypropylene, while the inner layer  106  is usually a metalized OPP. The use of a thermoplastic polymer such as OPP or Polyethylene terephthalate (PET) for the outer layer  102  and the inside layer  106  further makes it possible to heat seal any surface of the film to any other surface in forming either the transverse seals or back seal of a package. Sandwiched between the outer layers  102  and inner layer  106  is a middle layer  104 , which is typically either an adhesive or polyethylene. The inner, metallic layer  106  can itself be a layered laminate and contains a sealant layer  108  on what will be the inside, or product side, of the package. This sealant layer  108  is typically formed of a ter-polymer, composed of ethylene, propylene, and butylenes. Printing for the package is done on the inside of the outer layer and becomes sandwiched between the middle layer  104  and outer layer  102 . 
     Although  FIG. 1  depicts the inner layer  102  and outer layer  106  as only two layers, these layers  102 ,  106  can each include one or more layers. A metallic layer, such as aluminum, between the OPP layer  106  and the adhesive or polyethylene layer  104  can provide a barrier to retain taste and freshness of the product contained therein. Other materials used in these layers are polyester, paper, polyolefin extrusions, adhesive laminates, polyethylene and other such materials, or a layered combination of the above. The package seen in  FIG. 1  is referred to in the art as a “flexible bag” or “pillow pouch,” and is commonly used for packaging snack foods such as potato chips, tortilla chips, and other various sheeted and extruded products. 
     Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products.  FIG. 2  shows an exemplary vertical form, fill, and seal machine that can be used to package snack foods, such as chips. This drawing is simplified, and does not show the cabinet and support structures that typically surround such a machine, but it depicts the workings of the machine well. A continuous web of film  210  is pre-printed with desired graphics such as the product label and nutritional information and includes reference marks known as eye marks. The eye marks are generally a plurality of rectangular ink spots or marks spaced apart and formed along the edge of the film web. The pre-printed packaging film  210  is taken from a roll of film web on the supply spool (also known as the unwind)  212  and passed through tensioners  214  that keep it taut. The film then passes over a former  216 , which directs the film as it forms a vertical tube around a product delivery cylinder  218 . This product delivery cylinder  218  normally has either a round or a somewhat oval cross-section. A registration mark sensor is used to detect the eye marks and generate a signal, which triggers the cutting process. In other words, the sensor detects the marks and notifies the bag cutting and sealing machine where to cut and seal the bag so the print is aligned properly on the bag. As the tube of packaging material is pulled downward by drive belts  220 , the edges of the film are sealed along its length by a vertical sealer  222 , forming a back seal  224 . The machine then applies a pair of heat-sealing jaws  226  against the tube to form a transverse seal  228 . This transverse seal  228  acts as the top seal on the bag  230  below the sealing jaws  226  and the bottom seal on the bag  232  being filled and formed above the jaws  226 . After the transverse seal  228  has been formed, a cut is made across the sealed area to separate the finished bag  230  below the seal  228  from the partially completed bag  232  above the seal. The film tube is then pushed downward to draw out another package length. Before the sealing jaws form each transverse seal, the product to be packaged is dropped through the product delivery cylinder  218  and is held within the tube above the transverse seal  228 . 
     There are a number of desirable features that manufacturers have long strived to include in packages made on a vertical form, fill, and seal machine. One exemplary feature is the ability to re-close a package of a snack food that is only partially eaten, so that the flavor and texture of the product are preserved as long as possible. Ordinarily, not all of a package of snack foods is consumed at one time and thus there is a desire to reseal the package and prevent moisture from causing premature staling and spoilage of the contents. Many of the reclosable packages disclosed in the prior art utilize a mechanical reclosure means such as interlocking mechanical profiles or an adhesive reclosure means whereby at least a portion of the adhesive is adhered to the outside of the package to close the package mouth. Use of interlocking strips, however, such as zippers or sliders is costly, and complicates the manufacture of packaging. It would be desirable to have a low-cost alternative. 
     Referring to  FIGS. 3   a  and  3   b , therein is depicted a prior art packaging product having a recloseable seal feature, wherein the film comprises score lines  30 , which pass through all the layers of the film. An upper peelable seal  32  comprising an adhesive layer is then affixed over the scored section of the film. As seen in  FIG. 3   a , the upper peelable seal  32  has an area larger than that of the scored section and comprises a tear tab  34 , which is free from adhesive so that a consumer can grip the tear tab  34  with ease. Thus, as the consumer grips the tear tab  34  and pulls it back in the direction of the scored section, the film tears along the path of least resistance in the direction provided by the perforated lines  30 , creating a large flap on the top side of the package. An opening  38  is created in the bag and the adhesive layer  36  is exposed as depicted in  FIG. 3   b . A consumer can then consume a portion of the contents within the bag through the opening  38  and reseal the opening by sticking the adhesive layer  36  back onto the outer film layer of the package. 
     U.S. Patent Application 2005/0276525 to Hebert et al. discloses a recloseable package that is depicted in  FIGS. 4   a  and  4   b . However, rather than scoring once through the entire film, Hebert et al. performs two scoring operations: 1) through an inner portion of the film with score lines  40  and 2) through an outer portion of the film with score lines  42 . This pressure scoring is possible using laser or mechanical scoring or cutting. Laser scoring is a process that utilizes a laser beam to provide a focused spot of energy, which is able to remove material to a specified depth. The technology is well suited to fabricating high accuracy parts at high speeds, especially flexible packaging products. As seen in  FIG. 4   a , the outer perforation line  42  surrounds the inner perforation line  40 . When a consumer grabs the tear tab  44 , he can peel back the outer (ie, top) portion of the film away from the inner portion, exposing the adhesive layer  46  found between the two layers and separating the outer portion from the inner portion of the film. Products from within the bag are then fully exposed and can then be consumed from the opening  48 . When the consumer is ready to store any remaining products within the bag, he can reseal the package by pressing down around the top side of the package to reduce product exposure to the surrounding environment. 
     The prior art described above form packages with relatively large openings, allowing a consumer to readily consume food products from within the package with relative ease. In fact, the consumer need not grip the package with both hands to successfully retrieve the product within the bag. However, the prior art top flaps, such as those depicted in  FIGS. 3 and 4 , have a number of significant drawbacks. For example, the flap is scored along a substantial portion of the top side of the bag to form a U-shape, exposing a significant amount of the food products within the bag to its surroundings and making the products more susceptible to damaging conditions. Further, when attempting to reseal the packages, a consumer must push down along all three edges of the adhesive to adequately seal the bag. This places pressure on a significant portion of the products behind the seal of the bag. Placing pressure along the bag could cause the consumer to crush the contents remaining in the bag when it is resealed, resulting in a large amount of unwanted broken pieces or crumbs. In addition, frequent opening of the package causes frequent exposure of the adhesive to the products behind the top seal. Over time, this exposure causes the items such as unwanted crumbs to stick to the adhesive, diminishing its adhesive properties and rendering the seal inoperable. Finally, the horizontal packaging, while easy to pull open by means of the top flap, is made on a horizontal form, fill and seal machine, which are not typically use for loose fill products such as potato chips. 
     Consequently, because of the speed and productivity achieved on a vertical form, fill, and seal machine, a need exists for a flexible bag with a recloseable seal created using such technology and a single sheet of packaging film. Further, a need exists for a low cost reseal that offers minimum surface area from which products are exposed to its surroundings and allows a consumer to reseal packages without the need to score an entire side of a resulting package and without causing loss of seal adhesion. Finally, a need exists for a resealable package more akin to the high quality zipper seals often desired without the fear of damaging the products behind the seal and without the high costs associated with zipper seals. 
     SUMMARY OF THE INVENTION 
     The proposed invention involves producing a vertical flexible bag constructed of a single sheet of multi-layered material using a vertical form, fill, and seal machine and having a reclose seal along the top. The flexible bag formed on such a machine comprises an outer film layer, an inner film layer, and an adhesive between the outer and inner film layer. In a preferred embodiment, the outer film layer is scored at a position parallel to and less than two inches from the bottom of the top seal of the bag and to the adhesive middle layer, forming a first horizontal score line. More preferably, the first horizontal score line is less than or equal to approximately 1 inch from the bottom of the top seal, and most preferably equal to approximately 0.25 inches. The inner film layer is scored at a position below and parallel to the first horizontal line to the adhesive middle layer, forming a second horizontal score line that is below the first horizontal line. In one embodiment, the second horizontal score line is positioned from approximately 0.5 to one inch below the first horizontal score line. The area between the first and-second horizontal score lines define a single straight resealable opening. In an alternate embodiment, only one horizontal line is scored deep enough to entirely perforate through all the layers of the film. An upper adhesive seal comprising two different bond strengths is then placed over the horizontal score line, covering at least a half inch around the horizontal score line in all directions. Optionally, both embodiments comprise a tamper evident tab that lacks adhesive such that a consumer can pull on the tab to open the package. 
     The resulting flexible package may be opened, a part of the contents removed and the package closed (ie, resealed) to prevent premature deterioration of the quality of the contents because of exposure to moisture in the air. The reseal also prevents damage to the contents within the bag because of any pressure necessarily applied when attempting to reseal the bag. The bag formed as a consequence is a substantial improvement over prior art resealable bags. 
     The above as well as additional features and advantages of the present invention will become apparent in the following written detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  depicts a cross-section of a typical packaging film known in the prior art. 
         FIG. 2  depicts a vertical form, fill, and seal machine that is known in the prior art. 
         FIG. 3   a  depicts a prior art package incorporating a resealable label. 
         FIG. 3   b  depicts the prior art package seen in  FIG. 3   a  after it has been opened by a consumer. 
         FIG. 4   a  depicts a perspective view of another prior art package incorporating a resealable feature. 
         FIG. 4   b  depicts a perspective view of the prior art package of  FIG. 4   a  after it has been opened by a consumer. 
         FIG. 5   a  depicts a perspective view of one embodiment of-a flexible, resealable package of the instant invention. 
         FIG. 5   b  depicts the embodiment of  FIG. 5   a  after a consumer has peeled open the resealable opening. 
         FIG. 6   a  depicts a perspective view of a second embodiment of a flexible, resealable package of the instant invention. 
         FIG. 6   b  depicts the embodiment of  FIG. 6   a  after a consumer has opened the flexible, resealable package of the present invention. 
     
    
    
     Where used in the various figures of the drawing, the same numerals designate the same or similar parts. All figures are drawn for ease of explanation of the basic teachings of the present invention only; the extensions of the figures with respect to number, position, relationship, and dimensions of the parts to form the preferred embodiment will be explained or will be within the skill of the art after the following teachings of the present invention have been read and understood. Further, the exact dimensions and dimensional proportions- to conform to specific force, weight, strength, and similar requirements will likewise be within the skill of the art after the following teachings of the present invention have been read and understood. 
     DETAILED DESCRIPTION 
       FIGS. 5 and 6  depict two embodiments of the package of the present invention, which may be closed after being opened (ie, resealed) to preserve moisture sensitive food products, including but not limited to snack chips. The packages are made using a vertical form, fill, and seal machine and a flexible packaging film having at least three layers. In a preferred embodiment, an adhesive layer is pattern applied in between outer and inner film layers, preferably a pressure sensitive adhesive is placed in between an outer and inner score line and forms a bond in between the outer and inner film layers when pressure is applied across the top portion of the resulting package. As described above, and as seen in  FIG. 2 , in a vertical form, fill, and seal machine, a length of plastic film is formed into a vertical tube around a product delivery cylinder. The vertical tube is vertically sealed along its length to form a back seal and is transversely sealed to form top and bottom seals delineating individual packages, which are then cut from the vertical tube. 
     As used herein, the term “score lines” encompasses lines, notches or incisions that have been cut into the material or a portion of the material, perforating the film to enable it to be separated easily from adjoining portions of the adjacent material or sections. As used herein, “reclose strip” is synonymous with reseal. Applicants use the terms “peelable” and “releasable” interchangeably to refer to the side of the adhesive comprising a lower bond strength as compared to its opposing side. This provides for release of the peelable side of the adhesive from a first adjacent surface of a layer, while allowing for a more permanent bonding to a second adjacent surface of another layer when the layers surrounding either side of the adhesive are pulled apart by a consumer. 
       FIGS. 5   a  and  5   b  depict a perspective view of a first embodiment of the flexible, resealable package of the instant invention. As seen in  FIG. 5   a , the flexible film of the package has been scored along a horizontal line  50 . The flexible film is cut all the way through the film (ie, perforated through each of its layers) at line  50  substantially parallel to the top seal  52  of the package. Preferably, the score line  50  should be as close as possible to the bottom of the top seal, as illustrated in  FIG. 5   a  by the distance X. In one embodiment, the score line  50  is less than about 2 inches from the bottom of the top seal and more preferably about one inch from the bottom of the top seal. The score line  50  can be performed by any means known-in the art including without limitation die cutting or laser scoring. The ends of the score line  50  contain a slight deviation or curve from the line  50 , in either an up or down direction, to provide for a tear stop for decreased propagation, which prevents the package from tearing beyond- the length of the score line  50  and from forming inconsistent tear lines beyond the scope of the score line  50 . 
     Affixed over the score line  50  is a strip or label  54 , which is centered over the score line  50  to cover a length of about half an inch in each direction surrounding the score line  50 . The label  54 , contains a pattern-applied adhesive with at least two different bond strengths. On its inner side facing the outer side of the film of the bag and below the score line  50  (referred to as the lower portion), the affixed label  54  comprises an adhesive with a bond strength higher than that of the portion above the score line  50  (referred to as the upper portion), causing the lower portion to remain affixed to the outer film layer below the score line  50  when the label is pulled outward from the bag by a consumer. The upper portion of the affixed label  54  contains a pressure-sensitive adhesive  56  with a lower bond strength (typically from about 20 to 1,600 grams per inch width) than the adhesive of the lower portion of the label  54  (typically from about 100 to 4,000 grams per inch width, depending on the strength of the upper portion). Consequently, the upper portion of the label  54  comprises a peelable inner side that releases from the film of the package while the lower portion remains more permanently bonded to the film, forcing the film to tear along the scored line  50  when the label  54  is pulled away-from the film by a consumer. 
     After the film is scored and the label  54  affixed, the film is then run through a vertical form, fill and seal machine, as previously discussed in relation to  FIG. 2 , to form the bag seen in  FIGS. 5   a  and  5   b . The graphics on the packaging film can-be oriented in either the direction of film travel or perpendicular to the direction of the film travel.  FIG. 5   b  demonstrates the bag after it has been opened by a consumer. As seen in  FIG. 5   b , the opening  58  of the resulting flexible bag exposes the pressure-sensitive adhesive  56  to the inner side of the bag. The adhesive will then be able to reseal with the portion of the package above the score line  50  when pressure is placed along the seal by a consumer. 
       FIGS. 6   a  and  6   b  depict a second and preferred embodiment of the present invention, wherein offsetting cuts are made on the inside and outside layers (ie, sides) of the flexible film. As used herein, “offset” is used to mean non-overlapping such that the cuts made on the two sides of the flexible film form parallel score lines, but do not overlap or meet and do not completely perforate or cut the package completely through each layer along parallel planes of the film layers. By creating offsetting cuts on the two sides of the flexible film layer, two lines of weakness are formed which define a straight opening in the front side of the bag, as depicted in  FIG. 6   b , when the front and back sides are grabbed by the index finger and thumb and pulled away from one another. Thus, the film layers will comprise offsetting cuts at specific sides of the film and define a straight releasable opening along one side of the bag. 
     As described above in relation to  FIG. 1 , the film created for packaging products typically comprises an outer film layer  102  and an inner film layer  106  (which can each include one or more layers of materials) as well as a layer  104  sandwiched in between, which is comprised of either an adhesive or polyethylene. Consequently, as used herein, the terms “outer film layer” and “inner film layer” are meant to include one or more layers of materials on opposite sides of a film. In one embodiment, the sandwiched layer  104  can comprise both an adhesive layer and a polyethylene, which will make the bag stiffer, thicker, and more puncture resistant. 
       FIG. 6   a  demonstrates the second and preferred embodiment of the package in its sealed condition. A plurality of lines have been scored through the outer film layer of the flexible film package to the adhesive layer along a score line  60  in a line substantially parallel to, and at a distance X from, the bottom of the top seal  70  and perpendicular to the side edges of the web. The scoring forms an outer score line  60  through the outer film layer  102 , which as described above can comprise one or more layers of materials. As depicted in  FIG. 6   a , the optional tear tab forms a curve or semicircle towards the top seal in the center of the score line  60 . The tear tab does not comprise any adhesive in between the outer and inner sides of the film in order to provide a consumer with easy grip and access to opening the package. The cut is made by any means known in the art including without limitation laser or mechanical cutting. Preferably, the outer score line  60  is no more than two inches from the bottom of-the top seal  70 . Thus, the distance X, as seen in  FIGS. 6   a  and  6   b , should be less than two inches, more preferably less than or equal to about one inch and most preferably equal to about 0.25 inches. A plurality of lines is also scored through the innermost layer  106  to the adhesive layer, forming a second and parallel score line  62  on the inner (opposite) film layer. The score line  62  is a distance Y below the score line  60 , where Y ranges from about 0.5 to 1 inch (not including the optional tab in its center). The scoring of the second parallel score line  62  can be performed simultaneously or separately from the scoring of the first horizontal line. Together with score line  60 , score line  62  defines a resealable opening. Further, one skilled in the art, armed with this disclosure, will recognize that the score lines  60 ,  62  can be placed on the packaging film either during or after film formation before it is rolled into the supply spool  212 . In one embodiment, the outer and inner score lines both comprise a tear stop at each of its ends for decreased propagation. 
     Adhesive layers of different bond strengths are applied throughout the film layers of the bag and in between the outer layer and the inner layer of the film web during film formation. In one embodiment, the adhesive layer comprises at least two different bond strengths. A pressure sensitive adhesive  66  is pattern applied in between the outer score line  60  and the inner score line  62 , defined as Y in  FIG. 6   a , within the film that makes up the front side of the bag. This pressure sensitive adhesive  66  comprises a peelable side, which has a lower bond strength than that of the adhesive layer applied throughout the rest of the film in between the outer and inner layers. In other words, the bond strength of at least one side of the pressure sensitive adhesive applied in between the first horizontal (outer) score line  60  and the second horizontal (inner) score line  62  is less than that of any adhesive between the outer and inner layers throughout the film of the flexible bag. This allows for one side of the adhesive to be releasable from a first adjacent side in between the inner layer and outer layer of the bag. Generally, the bond strength of a releasing pressure-sensitive adhesive is between about 25 to about 1,600 grams per inch width, while the bond strength of the opposing side of the adhesive ranges from between about 100 to 4,000 grams per inch width or higher, so long as the latter bond strength is higher than that of the former to create a more permanent bond which has a more aggressive adhesive. Thus, a first side of the adhesive is peelable from to a first adjacent surface, while the second side of the adhesive is more strongly adhesive to a second adjacent surface. Any adhesive in between the outer and inner layers throughout the rest of the package away from the outer and inner score lines will also comprise a higher bond strength than the peelable side. In one embodiment, the peelable side of the pressure-sensitive adhesive  66  has a bond strength ranging from approximately 25 to 1,600 grams per inch width and is adjacent to an inner film layer, while the opposite side has a stronger adhesive bond strength ranging from 100 to 4,000 grams per inch width and is adjacent to an outer film layer, such that upon separation by a consumer, the peelable adhesive will release from the inner film layer. In another embodiment, the peelablc adhesive has a bond strength ranging from approximately 200-800 grams per inch width, while the opposite (more permanently-bonded) side has a bond strength ranging from approximately 800-4000 grams per inch width. Thus, a straight resealable opening  64 , seen in  FIG. 6   b , is formed at the top of the bag between the first outer score line and second inner score line when the front and back sides of the bag are pulled apart or separated by a consumer. The pattern applied pressure-sensitive adhesive  66  remains bonded to the surface with which it more permanently bonded and is exposed on the inner side of the outer film layer. The adhesive  66  can then engage the exposed area  68  of the inner layer to form the reseal under pressure imposed by a user such as pressing along section Y on the outside of the bag towards the exposed area  68 . Alternatively, one skilled in the art, armed with this disclosure, will also recognize that the bond strength of the pattern-applied adhesive can also be adjusted such that the adhesive  66  remains on the exposed area  68 . Thus, the adhesive layer  66  within the front side of the package wall releasably adheres the inner and outer layers of the film back together once separated by a consumer. 
     To form the package shown in  FIGS. 6   a  and  6   b , after formation and scoring of the film, it is then placed on the supply spool  212  of a vertical form, fill and seal machine, as discussed in relation to  FIG. 2  in the prior art. As discussed previously, a registration mark sensor will detect the eye marks pre-printed on the scored film to align the film properly such that the reseal is at the top of the bag and ensure that the package is sealed and cut at the proper locations. The vertical form and fill machine thus operates as previously described in the prior art, with the vertical seal along its length to form a back seal and a transverse seal along its bottom to form a bottom seal. Product is then introduced through the forming tube  218  into the sealed tube of packaging film, and the upper transverse seal being formed within 2 inches of the reseal, thereby forming a top seal  70  and completing the package. As used herein the top and bottom seals are used to encompass seals made between two adjacent film layers by applying heat and/or pressure (ie, between sealing jaws) for a given dwell time. 
     As shown in  FIG. 6   a , the flexible package formed comprises a width W and a length L. A plurality of score lines formed along the outer film portion  102  and the plurality of score lines formed along inner film portion  106  define an opening  64  having a length L 1 . The length L 1  is approximately 83% to 99% of the width W of the bag, and more preferably, about 91% to about 98% of the width W of the bag. In other words, the ratio of the length of the opening L 1  to the width W ranges from approximately 9:10 to approximately 49:50. In another embodiment, the length L 1  of the opening ranges from approximately 25% to approximately 68% versus the length L of the bag, resulting in a ratio for the opening to length.of.the bag ranging from between approximately 1:4 to approximately 34:50. 
     After opening, the packages of the two embodiments described above can then be reclosed by applying pressure across the top of the package. The package can then be re-opened and re-closed as desired by the consumer. Referring to  FIGS. 5   a ,  5   b ,  6   a  and  6   b , while the reseal  50 ,  60  is functional anyplace on the package, it is desirable that the strip be applied on the upper half of the resulting package and as close as possible to the bottom of the top seal, preferably less than 2 inches from the bottom of the top seal  52 ,  70  of the resulting package. Placing the reseal  50 ,  60  on the lower half of the bag could cause the user to crush the contents remaining in the bag when it is resealed. 
     The present invention offers an economic method of producing an incorporated reseal function without modification of the vertical form, fill and seal machines used to continuously and effectively produce snack food packages. The invention is further an improvement over methods for including reseal functions on snack food packages. While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention.