TITLE
[0001] A method of manufacturing a resealable vented multilayer film for use in heat sealable tray sealing machines and a resealable vented multilayer film.
FIELD
[0002] There is described a method of manufacturing a multilayer film for heat sealable tray sealing machines, which is resealable and which has micro-perforations for modifying or controlling the flow of oxygen and carbon dioxide in and out of a fresh produce container.
BACKGROUND
[0003] United States Patent 7,083,837 (Varriano-Marston) titled "Registered micro-perforated films for modified/controlled atmosphere packaging", describes micro-perforated packaging material for use in modifying or controlling the flow of oxygen and carbon dioxide into and out of a fresh produce container.
[0004] United States Patent Publication 20110038569 (Huffer) titled "Easy-open resealable package", describes a package with a region of pressure-sensitive adhesive that enables a user to reclose the package after use by adhering an end portion of the packaging to the pressure-sensitive adhesive.
SUMMARY
According to one aspect there is provided a method of manufacturing a resealable vented multilayer film for use in heat sealable tray sealing machines. The method involves a first step of laminating a polymeric bottom layer, a pressure sensitive adhesive layer and a polymeric top layer to form a multi-layer film having a peripheral edge. The method involves a second step of perforating the multi-layer film. The method involves a third step of scoring the bottom layer to create a frangible connection. The frangible connection is spaced inwardly from a peripheral edge of the bottom layer. The top layer and the bottom layer remain adhered in a central portion of the multi-layer film, while the top layer separates from the bottom layer along the peripheral edge leaving a portion of the bottom layer as a resealing flange defined by the positioning of the frangible connection.
[0005] According to another aspect there is provided a resealable vented multilayer film, which consists of a perforated multi-layer firm comprising a polymeric bottom layer laminated by a pressure sensitive adhesive layer to a polymeric top layer. The multi-layer film has a peripheral edge. The bottom layer is scored to create a frangible connection. The frangible connection is spaced inwardly from a peripheral edge of the multi-layer film so that a portion of the bottom layer provides a resealing flange.
[0006] The film may feature an additional two layers. For example, a further adhesive layer may be used to place a printed layer onto the first layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein:
[0008] FIG. 1 is a section view of a first embodiment of resealable vented multilayer film.
[0009] FIG. 2 is a section view of a second embodiment of resealable vented multilayer film.
[0010] FIG. 3 is an end elevation view, in section, of a tray having the resealable vented multilayer film of FIG. 1.
[0011] FIG. 4 is an end elevation view, in section, of a tray having the resealable vented multilayer film of FIG. 2.
[0012] FIG. 5 is bottom plan view of the resealable vented multilayer film of FIG. 1, showing micro-perforation and scoring detail.
[0013] FIG. 6 is a side elevation view of a manufacturing process for producing the resealable vented multilayer film of FIG. 1.
DETAILED DESCRIPTION
[0014] A method of manufacturing a resealable vented multilayer film for use in heat sealable tray sealing machines, generally identified by reference numeral 10, will now be described with reference to FIG. 1 through FIG. 6.
Structure and Relationship of Parts:
[0015] The present method relates to packaging films comprising of several layers of polymeric films and pressure sensitive adhesive. Referring to FIG. 1, a polymeric bottom layer 13, is coated with a pressure sensitive adhesive layer 12, and then laminated with a polymeric top layer 11 of a heat sealable Polyester of other heat sealable polymeric substrate.
[0016] Referring to FIG. 3 and FIG. 5, film 10 is laser perforated with holes 14 of various quantity and size from 50 micron to 90 micron, to control the atmosphere in the package for fresh food products that respire at a fast or medium rate such as lettuce, leafy greens, carrots, and celery. The number of holes 14 differs with the produce being packaged.
With new products not previously packaged, different numbers of holes 14 are tested to see what works best for air flow.
[0017] Referring to FIG. 3 and FIG. 5, the bottom layer 13 of film 10 is scored to create a frangible connection in from the edges of bottom layer 13 to leave an edge flange 16. The scoring 18 can be done with either a laser or a metal rotary or flatbed die cutter. The score cut is made with various sizes in conjunction with the tray size and can be modified based on customer needs. The lidding film 10 is heat sealed to the rigid or semi rigid tray 20.
[0018] Pressure sensitive adhesive layer 12 utilizes a wet or fluid adhesive that remains "open" in that it does not cure dry, but remains "tacky" to the touch. This adhesive being fluid in nature, albeit viscous, can have a tendency to flow or move after application.
[0019] Referring to FIG. 6, there is illustrated bottom layer 13 being pulled past a cylinder 15 which applies pressure sensitive adhesive 12. Bottom layer 13 is then passed by a series of dryers 17. It is to be noted that even after "drying" pressure sensitive adhesive remains "tacky". Top layer 11 is then fed from feed roller 19 and top layer 11 is adhered to bottom layer 13 by passing through nip rollers 21, which press top layer 11 and bottom layer 13 together. As top layer 11 and bottom layer 13 exit nip rollers 21, they are secured together by pressure sensitive adhesive 12. Bottom layer 13 is then scored by passing through die cutter 23. Both top layer 11 and bottom layer 13 are then perforated by a laser 25. The film formed (consisting) of top layer 11, pressure sensitive adhesive layer 12 and bottom layer 13 is then wound onto a spool (shown as block 27) in preparation for the second process of 5 being heat sealed onto tray 20 in a conventional manner.
Operation:
[0020] Referring to FIG. 3, the consumer can pull up from the designated corner of film 10 10 to separate top layer 11 and the central portion of bottom layer 13.
Where the bottom layer has been scored 18 to create a frangible connection in from the edges of bottom layer 13, a flange 16 of bottom layer 13 is revealed which top layer 11 overlies during resealing.
The recess film flange 16 can be of various widths and is necessary to ensure the support of weight when the product is shipped and adjusted to meet access requirements of the client.
[0021] As described above, pressure sensitive adhesive layer 12 does not cure dry, but remains "tacky" to the touch. This enables the top layer 11 to be resealed to the remaining edge flange of bottom layer 13.
Variations:
[0022] Referring to FIG. 2, additional layers 22 may be secured by adhesive 24 to first layer 11. These additional layers 22 are not intended to separate and adhesive 24 used is not pressure-sensitive. For example, it may be desirable to adhere a printed layer.
[0023] Referring to FIG. 4, as previously described in relation to FIG. 3, the consumer can pull up from the designated corner of film 10 to separate top layer 11 from bottom layer 13. When this happens, a portion of bottom layer 13 forming film flange 16 is revealed which is recessed from the edge of the tray 20.
[0024] There are a number of benefits that are derived from having a hole size of 50 to 90 microns. These are smaller holes and there are more of them to provide the same air flow. The higher quantity of holes reduces the impact if one or more holes is blocked due to food product being in the way of a hole, or, if a tray or other item is placed on top of the package during shipping or storage. The smaller holes more effectively block external contaminants and foreign particles from entering packaging. There tends to be less adhesive flow into the center of hole, which avoids hole blockage by adhesive.
[0025] In this patent document, the word "comprising" is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article "a" does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements.
[0026] The scope of the claims should not be limited by the illustrated embodiments set forth as examples, but should be given the broadest interpretation consistent with a purposive construction of the claims in view of the description as a whole.