GB2367033A

GB2367033A - Multiply film assembly

Info

Publication number: GB2367033A
Application number: GB0023324A
Authority: GB
Inventors: Luen Sing Tang
Original assignee: TECKSOM INTERNAT Ltd; Tecksom International Ltd
Current assignee: TECKSOM INTERNAT Ltd; Tecksom International Ltd
Priority date: 2000-09-22
Filing date: 2000-09-22
Publication date: 2002-03-27
Also published as: GB0023324D0

Abstract

A multiply film assembly (2) for sealing to another portion to thereby in combination define a sealed container such as a bag or a pack including a tray having a first ply (23) of a film material of a shape to define the perimeter of the assembly, at least three panels of a film material (20) arranged in an abutting configuration and each adhered to at least part of one major surface of the first ply. At least one (18) of the three panels is adhered to the major surface in a releasable manner whilst the other of the panels are adhered in a permanent manner. The reduced seal regions are able to create an opening for any gas buildup (eg as a result of cooking) to vent from the interior of the container.

Description

A MULTI PLY FILM MATERIAL

HELD OF INVENTION The present invention relates to a multi ply film material which is for example useful in the provision, or may define part of the enclosure of a pack containing food. In particular although not solely the film material is useful in packs containing food which are heated by micro wave energy and which require a small opening to be formed in order, during such heating, to avoid the expansion of the volume of the pack and thereby cause undesirable rupturing or explosion.

BACKGROUND ART Film material to define packages suitable for cooking applications are known.

Such include packages which are adapted to allow the cooking of foods contained therein, in a microwave oven.

During the cooking of certain foods in such packages, it is desirable to maintain a level of moisture in order to prevent the foods from cooking dry. The presence of

moisture within a package during the cooking of the foods will keep the food moist and more pleasant to the taste.

A common form of microwave package is made of plastic film material and can receive food through a mouth region. Water or other liquid may also be added to the contents whereafter the package is normally sealed to contain its contents and placed in the microwave. Upon the heating it will be appreciated that as a result of heating,

the pressure inside of the package will increase. The increase in pressure may be such that the package may rupture and result in the spilling of the contents. Continued cooking after the rupturing may result in the food from cooking dry.

Bags with vent holes to deal with an over pressure also exist. For example, US4874620 defines a bag of a multi ply assembly which incoiporales a venting passage which can be created between plies of the multi ply assembly of the film defining. the bag.

In US4874620 there is provided two plies of a film material wherein the innermost ply is provided with a strip which extends across the sealed mouth region of the bag, wherein along the strip the inner ply is not adhered to the multi ply assembly.

Perforations provided to the inner ply along this strip allow for pressure relief

of a gas build up within the containment region of the bag to escape along the strip, through the sealed mouth region and out from the bag. The bag is made from at least two co-extensive plies of material wherein adhesion between the plies, save for the strip region, is achieved by pattern application of an adhesive.

This requires the use of machinery which is capable of pattern applying the laminating adhesives. Because gas access to the strip region defining the vent is achieved by a perforation of the inner ply along the strip region, the machine is also

required to provide, or allow for the use of a pre manufactured film which incorporates a perforation.

One further disadvantage of the bag of US4874620 is that because of no adherence occmring at the strip region between the two plies of film material, there is provided even before gas expansion within the containment region, a fluid collection between the interior and exterior of the bag. For the purposes of containing food, it is desirable for the containment region of a bag to be fully sealed to the external environment until such time as eating is eminent Furthermore, some food products are desirably packed under at least a partial vacuum and the invention of US4874620 would not reliably allow for such a vacuum to be created.

Accordingly it is an object of the present invention to overcome the abovementioned disadvantages or to at least provide the public with a useful choice.

BRIEF DESCRIPTION OF HvENTtON Accordingly in a first aspect the present invention consists in a bag which provides a containment region for food, said bag fanned of film material to define a front and back wall of said bag and to define sealed side edges, a mouth end and a bottom end wherein the -ont and back walls at said bottom end are substantially heat sealed to each other

to define a sealed bottom of said bag (preferably substantially laterally to the longitudinal mouth to bottom direction of said bag), wherein at least one of said front or back walls is a multiply plastic film which includes an exterior most ply and an inner most ply, said inner most ply comprising of at least 3 juxtaposed panels having their adjacent edges abutting each other, and adhered (whether directly or not) to said exterior ply, wherein abutting edges of said panels extend at least across said bottom seal and at least in part into the containment region, and wherein at least one of said panels is separably adhered to said exterior most ply to allow separation dmfrom across said sealed bottom and at least in part in said containment region side of said wall, to thereby create a vent passage between said at least one panel and the exterior most ply of said multiply assembly, to allow the escape of some fluid from the containment region of said bag during conditions of pressurisation of said containment region (e. g. during heating of said food).

Preferably said at least one panel which is separably adhered to said exterior most ply is a panel of said at least three juxtaposed panels, which is an intermediate of the at least three juxtaposed panels.

Preferably said exterior most ply is adhered to said inner most ply and wherein said at least one panel of said inner most ply also includes a release agent provided at least across said sealed bottom and intermediate of said at least one panel and said exterior most ply.

Preferably said at least one panel is a strip which is co-extensive (mouth to bottom) of exterior ply.

In a second aspect the present invention consist in a pack which includes a tray of a kind which defines a receptacle defined by a bottom and side walls extending upwardly from said bottom, wherein the side walls are terminated by a Bared or flanged

rim at a mouth opening to said receptacle, wherein sealed to the rim to cover the mouth of said receptacle is a multiply film material which comprises ; au exterior ply of a sheet film material, an inward most ply, inward of said exterior ply and sealed to said rim of said receptacle, said inward most ply comprising of at least three juxtaposed panels of film

material wherein abutting edges of said panels extend at least across the region of sealing of said multi ply assembly with said rim of said container, and wherein all panels of said inward most ply are adhered to said exterior ply, and wherein at least one panel of said inward most ply, is adhered (directly or indirectly) to the exterior ply in a releasable manner, wherein when an over pressure (relative to atmospheric conditions) results from heating the contents of said pack occurs, the adhesion between said at least one panel and said exterior ply, will results in pealing of said at least one panel from the exterior ply whist the other panels will remain adhered.

Preferably said at least one panel is a single ply film material.

Preferably said at least one panel has intermediate with its adhesion with said exterior ply, a release agent provided.

Preferably wherein said at least one panel is a multi ply film material wherein the ply thereof adjacent to said exterior ply is provided with a release agent on the surface thereof to mate with said exterior ply.

Alternatively said exterior ply includes an additional ply which is co-extensive with said at least one panel of the inward ply and is adhered therewith in a releasable manner.

Preferably said at least one panel is a panel flanked by one or more of the other panels of said inward most ply.

Preferably said at least one panel is sealed to said exterior ply by an adhesive, but where said adhesive strength is reduced by the provision of a release agent on the mating surface of said at least one panel.

In a further aspect the present invention consists in a method of making a multi ply film material comprising providing a first ply of film material (hereinafter exterior ply) adhering at least three juxtaposed and abutting panels to a first major surface of said exterior ply, wherein at least one of said panels includes a release agent applied to a major surface to be intermediate of said at least one panel and said exterior ply, and

wherein the panels immediately adjacent to said at least one panel are fully adhered to said exterior panel.

Preferably said release agent is applied to a surface of said at least one panel before being adhered to said exterior panel In still a further aspect the present invention consists in a multiply film assembly for seating thereof to another portion to thereby in combination define a sealed container said assembly comprising : a first ply of a film material of a shape to define the perimeter of said assembly, at least three panels of a film material arranged in an abutting configuration relative to each other and each adhered to at least part of one major surface of said first ply, wherein at least one of said three panels adhered to said major surface in a releasable manner whilst the other of said panels are adhered in a permanent manner wherein edges of said at least one panel abutting with the adjacent edges of said other panels, extend across a region where said multiply assembly is to be sealed to the other portion of the said container.

Preferably said at least one panel is directly adhered in a releasable manner to said first ply.

Preferably said at least one panel is adhered in a releasable manner to said fast ply indirectly by being adhered to an intermediate ply which is coextensive with said at least one ply.

Preferably said adhesion in a releasable manner is provided by a release agent between said intermediate ply and said first ply.

Preferably said adhesion in the releasable manner is provided by a release agent between said intermediate ply and said at least one panel.

This invention may also be said broadly to consist in the parts, elements and features referred to or indicated in the specification of the application, individually or collectively, and any or all combinations of any two or more of said parts, elements or features, and where specific integers are mentioned herein which have known

equivalents in the art to which this invention relates, such known equivalents are deemed to be incorporated herein as if individually set forth.

The invention consists in the foregoing and also envisages constructions of which the following gives examples.

One preferred form of the present invention will now be described with reference to the accompanying drawings in which ; BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded sectional view through a portion of a package at the region where a venting passage is to be finned, wherein a front wall 2 and a rear wall 3 are provided to there between define a containment region X, Figure 2 is an alternative configuration to that shown in Figure 1, Figure 3 is an alternative configuration to that shown in Figure 1, Figure 4 is an alternative configuration to that shown in Figure 1, Figure 5 is an alternative configuration to that as shown in Figure 1, Figure 6 is a perspective view of a sheet of film material which can be utilised to define the front and back panels to form a package of the present invention, Figure 7 illustrates a perspective view of one preferred form of the present invention in a completely assembled condition and that being formed from a sheet of film material as for example shown in Figure 6, Figure 8 is a perspective view of an end region of a package of the present invention illustrating an alternative configuration by which the vent passage may be provided, Figure 9 illustrates an alternative configuration to that shown in Figure 1, Figure 9a illustrates the transition of the vent passage to a condition where a vent passage is formed, Figure 10 is a plan view of the package of the present invention wherein the mouth edge is still unsealed and ready for receiving food to be contained within the containment region defined by the front and rear panels, Figure 11 is a view through section C-C of Figure 10,

Figure 12 is a view through section A-A of Figure 10, Figure 13 is a view through section D-D, Figure 14 is a view enough section B-B, Figure 15 is a perspective view of an end region of the bag of the present invention wherein a vent passage has been fanned between the plies of the multiply assembly of at least one of the front or rear panels of the package of the present invention, Figure 16 is an illustration of a pack which incorporates as part of the enclosure, the film material of the present invention, and Figure 17 is a perspective illustrating in simplified terms, how the multi ply film of the present invention may be assembled.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT In the preferred form the present invention consists in multi ply film material 2 for a bag or package 1 or 30 for or which contains a food contents within the containment region of the bag. In one preferred use with reference to Figure 7, the bag is preferably of a rectangular shape and has side edges 12, a bottom edge 11 and a mouth edge 10. The containment region is defined between these edges and between a front and rear walls of a sheet material. In the preferred form where the bag is formed from a tube of material which may for example have been formed from a sheet of film material wherein the longitudinal edges have been brought together to define the tube, the mouth and bottOm edges extend preferably laterally to The general direction of the longitudinal edges.

The front wall 2 and back wall 3 may alternatively have their side edges 12 sealed together however in the most preferred form the front and rear walls are defined by the folding of a single sheet of film material into a tube and forming a longitudinal seal 13, as for example shown in Figure 6. This sealing may be achieved by adhesive, RF sealing or heat sealing techniques.

The containment region X defined between the front and rear walls 2, 3 is a region where contents such as food can be placed and can be sealed within the package.

Such contents is for example a food contents which may be subjected to heating.

With reference to Figures 1-5, it can be seen that at least one of the front or rear walls is a multiply assembly. The multiply assembly is of a configuration which allows for a vent passage to be formed through at least one and preferably both of the end seals provided to define the bottom and mouth edges 10, 11. This vent passage 14 is to be formed when a pressure increase occurs within the containment region to an extent at which such pressure needs to be released to avoid ruptureing of the bag. The vent passage is of a nature to allow for some of the fluid to escape from the containment region across the end seal of the package and away from the package. Therefore as the food contents of the package is heated, the forming of the vent package will prevent the package from exploding or rupturing undesirably.

The multi ply assembly 2 film material which provides the region which allows the formation of the vent passage consists of an outer ply 23 and at least one ply inwardly thereof which preferably consists of panels 20, 21 and 18. The panel 18 is preferably at least provided to be positioned across the end seal region of the bottom and/or mouth edges 10, 11. Figure 8 shows only a partial panel 18. In the preferred form, as the multi ply film material is manufactured from continuous roll feed, this panel 18 is substantially co-extensive with the panels 20, 21.

With reference to Figure 17 the multi ply film material of the present invention is made up by providing at least the outer ply 23 and an inner ply consisting of panels 20, 21 and 18. The inner ply has the three panels (and there could be further panels) dispensed from rolls of stock material and manoeuvred to be in an abutting or perhaps partially overlapping relationship. The outer ply 23 is adhered to the panels 20 and 21 of the inner ply.

The achievement of reduced strength adherence between the exterior panel and the intermediate panel 18 is preferably achieved by the use of a release agent which is for example pro-applied to me feed stock material, or during the process as for example

shown in Figure 17, can be applied at least sometime prior to the point where the exterior ply is brought into contact with the intermediate panel 18.

In this manner, adhesive can then be applied entirely to the abutting surface of the outer ply.

The release agent 19, is in this process conveniently positioned to be only provided intermediate of the panel 18 and the external ply 23.

With reference to Figure 13, the containment region XI before an over pressure is formed within the containment region, is substantially sealed. The reduced but still effective sealing of the panel 18 with the external ply 23 is such that during normal conditions of for example transportation and atmospheric conditions, no opening is created across the end seal at the bottom edge 11. Indeed the sealing is preferably such that a partial vacuum can be created if desired within the containment region.

Once an over pressure is created within the containment region X, such as for example when the containment region and its contents is heated, the expansion of the interior gases is desirably controlled. The vent passage 14 is at this point formed to allow for the expanded gases within the containment region to escape from within the pack. With reference to Figure IS and 11, a separation between the exterior ply and the intermediate panel occurs at least at and across the end seal of for example the bottom and/or mouth edges 10, 11. As the intermediate panel 18 is fully or more significantly adhered to the other wall 3 or for example the tray 31 of the pack, a vent passage (which is shown in an exaggerated form) can be formed as shown in Figure 12.

The end seals of the bottom and mouth edges 10, 11 are preferably provided by heat sealing. Accordingly me material selected for the rear waU 3 and the interior most plies of me front wall 2. are such as to allow for full heat sealing to occur there between across the bottom and mouth edges. Figures 2-3 illustrate alternative arrangements but such arrangements consistently have the feature that the inner most plies of the front and rear walls are fully heat salable to each other, With reference to Figure 1, ply 20 and 21 are preferably of a material such as PET (polyethylene tercphmahte) the panel 18 is preferably of PET, the exterior ply 23 of the front wall is preferably of a material such as OPP (oriented polypropylene). The

interior most ply of the back wall 3, is preferably also of a like material to the panels defining the inner most ply of the front wall. Hence this material is preferably also PET.

As an altemative fonn, the interior most plies of the front and back walls may be of PET. Alternatively a combination of these materials may be used in the make up of me intenorply ofthe & ontwall such that for example CPP is used for me panels 20, 21 and PET is used for the panel 18 wherein the interior most ply of the back wall is CPP, and wherein appropriate temperatures and perhaps a heat scalable glue needs to be utilised. The release agent is preferably of a material such as a flexographic ink which is of a kind which will prevent complete lamination and provides only partial or reduced strength lamination. In the preferred form this ink is first applied to the side of panel 18 to be facing the exterior ply 23. It is then allowed to dry.

Before each of the plies are brought together, a laminating adhesive such as a polyursthane adhesive, is applied to the surfaces of panels 21, 18 and 20 and the outer ply 23 before me panels 21, 18 and 20 are adhered to me outer ply 23.

With reference to Figures 4 and 5, the strip assembly of panels 18 and 33, are first produced by laminating these together. In Figure 5, as well as laminating, the application of their release agent is also provided before the assembly of the strip defined by panels 18 and 23 is brought in conjunction with the panels 21 and 20 to be laminated to the exterior ply 23.

Once the multi ply assembly as for example formed according to the steps shown in Figure 17, me Sim matenal can be manipulated as for example shown in Figure 6 to define a bag made from the multi ply film assembly. Heat sealing across a longitudinal seal formed where parallel edges of the sheet material are joined, is preferably provided by heat or adhesive sealing or the like.

The heat sealing of the film material to provide the end seals, can be performed at temperatures that are suitable for the joining materials to be sealed together. The temperature for sealing CPP films together can for example be between 1300 and 150 C. A higher sealing temperature has to be applied when sealing the PET films together. Normally when a heat salable glue is applied between the PET films to be

seals, the scaling temperature can for example be between 130"and 200"C. However it has to be kept in mind that PET can not be heat sealed with either OPP or CPP. In the preferred embodiment of the plies of Figure 1, where the panels 20,21 and 18, and the back wall 3 are made from PET, the PET films are sealed under appropriate temperatures (for example between 130 and 200aC with the application of a heat sealably glue).

In the case shown in Figures 4 and 5 a possible combination of materials is from

top to bottom, OPP, PET for me intennediate panel (within the multi ply 2) CPP for the icdtshor most ply of the multi ply 2 and CPP for thetenor most ply of the back wall. Due to the structural differences between PET and OPP, CPP, there is no risk of the PET panel being sealed to the CPP or (NT.

In a general sense, the materials and configurations of the plies and panels chosen is such that the panel 18 has substantially no possibility of being fully bonded on both sides (by heat or lamination sealing) so as to ensure a vent passage can be formed.

With reference to Figure S. there is shown a version of the multi ply assembly of the present invention wherein a panel co-extensive with the intermediate panel 18 is provided. Between this panel 33 and panel 18 there is provided the release agent to allow a vent opening to be created there between.

The advantage of the arrangement as shown in Figure 5, is that, in for example the package of Figure 16, a tearable opening can be provided by uplifting both panel 18 and 33 whereby these shear through the exterior panel 23. Alternatively, it may only be the ply 33 which is uplifted to thereby shear through the exterior ply 23.

The multi ply assembly of Figure S. In this case, the interior most ply of the multi ply assembly 2 is made up of CPP or PET for bonding to the rim of the tray. At least the rim of the tray is made up of polypropylene or polyethylene. Once sealed,

because of the strong bonding, panel 18 can not be hand lifted. The structure of the present invention (with the addition of the release agent between panel 33 and 18) enables easy opening of the container as shown in Figure 16 by allowing the panel 33 to be uplifted to thereby shear through the exterior ply 23. So as well as providing a

suitable means to open the container, the multi ply assembly of the present invention provides the formation of the venting passage when an overpressure occurs inside of the container. The advantage is that the panel 18 does not need to be a material different to the panels 20 and 21 such as for example a more expensive material as EVA (ethylene vinyl acetate) in order to avoid this panel from being sealed to the rim of the container to therebetween provide the vent passage or to enable uplifting of the panel. In the configuration of the multi ply assembly of Figure 5, the panel 18 does become fully sealed to the rim of the container and the vent passages form between the panel 18 and intermediate panel 33. The benefit of hygiene is also immediately apparent.

The multi ply film assembly of the present invention and its use with the container as for example shown in Figure 16, are also suitable for oven cooking. A suitable selection of materials must be made in order to ensure that because of prolonged heating, the integrity of the pack is not compromised. The use of, for example CPP or OPP will not be possible because they are likely to melt in the oven. In this case it will be best to use PET for all layers of the multi ply assembly.

The most preferred form of the release agent is a solvent-based flexographic ink composed of synthetic resins and organic pigment dissolved in an organic solvent. The organic solvent can for example be alcohol or alcohol with small amounts of esters or ketones.

Claims

CLAIMS : 1. A bag which provides a containment region for food, said bag formed of film material to define a front and back wall of said bag and to define sealed side edges, a mouth end and a bottom end wherein the front and back walls at said bottom end are substantially heat sealed to each other to define a sealed bottom of said bag (preferably substantially laterally to the longitudinal mouth to bottom direction of said bag), wherein at least one of said front or back walls is multiply plastic film which includes an exterior most ply and an inner most ply, said inner most ply comprising of at least 3 juxtaposed panels having their adjacent edges abutting each other, and adhered (whether directly or not) to said exterior ply, wherein abutting edges of said panels extend at least across said bottom seal and at least in part into the containment region, and wherein at least one of said panels is separably adhered to said exterior most ply to allow separation therefrom across said sealed bottom and at least in part in said containment region side of said wall, to thereby create a vent passage between said at least one panel and the exterior most ply of said multiply assembly, to allow the escape of some fluid from the containment nlgion of said bag during conditions of pressurisation of said containment region (e. g. during heating of said food).
2. A bag as claimed in claim 1 wherein said at least one panel which is separably adhered to said exterior most ply is a panel of said at least three juxtaposed panels, which is an intermediate of the at least three juxtaposed panels.
3. A bag as claimed in claims 1 or 2 wherein said exterior most ply is adhered to said inner most ply and wherein said at least one panel of said inner most ply also includes a release agent provided at least across said sealed bottom and intermediate of said at least one panel and said exterior most ply.
4. A bag as claimed in any one of claims 1 to 3 wherein said at least one panel is a strip which is co-extensive (mouth to bottom) of exterior ply.
5. A pack which includes a tray of a kind which defines a receptacle defined by a bottom and side walls extending upwardly from said bottom, wherein the side walls are terminated by a flared or flanged rim at a mouth opening to said receptacle, wherein sealed to the rim to cover the mouth of said receptacle is a multiply film material which comprises ;

an exterior ply of a sheet film material, an inward most ply, inward of said exterior ply and sealed to said rim of said receptacle, said inward most ply comprising of at least three juxtaposed panels of film material wherein abutting edges of said panels extend at least across the region of sealing of said multi ply assembly with said rim of said container, and wherein all panels of said inward most ply are adhered to said exterior ply, and wherein at least one panel of said inward most ply, is adhered (directly or indirectly) to the exterior ply in a releasable manner.
6. A pack as claimed in claim 5 wherein when an over pressure (relative to atmospheric conditions) results from heating the contents of said pack occurs, the adhesion between said at least one panel and said exterior ply, will result in pealing of said at least one panel from the exterior ply whilst the other panels will remain adhered.
7. A pack as claimed in claims 5 or 6 wherein said at least one panel is a single ply film material.
8. A pack as claimed in any one of claims 5 to 7 wherein said at least one panel has intermediate with its adhesion with said exterior ply, a release agent provided.
9. A pack as claimed in any one of claims 5 to 8 wherein said at least one panel is a multi ply film material wherein the ply thereof adjacent to said exterior ply is provided with a release agent on the surface thereof to mate with said exterior ply.
10. A pack as claimed in claims 5 or 6 wherein said exterior ply includes an additional ply which is co-extensive with said at least one panel of the inward ply and is adhered therewith in a releasable manner.
11. A pack as claimed in any one of claims 5 to 10 wherein said at least one panel is a panel flanked by one or more of the other panels of said inward most ply.
12. A pack as claimed in any one of claims 5 to 11 wherein said at least one panel is sealed to said exterior ply by an adhesive, but where said adhesive strength is reduced by the provision of a release agent on the mating surface of said at least one panel.
13. A method of making a multi ply film maternal comprising providing a first ply of film material (hereinafter exterior ply) adhering at least three juxtaposed and abutting panels to a first major surface of

said exterior ply, wherein at least one of said panels includes a release agent applied to a major surface to be intermediate of said at least panel and said exterior ply, and wherein the panels immediately adjacent to said at least one panel are fully adhered to said exterior panel.
14. A method as claimed in claim 13 wherein said release agent is applied to a surface of said at least one panel before being adhered to said exterior panel.
15. A multiply film assembly for sealing thereof to another portion to thereby in combination define a sealed container said assembly comprising : a first ply of a film material of a shape to define the perimeter of said assembly, at least three panels of a film material arranged in an abutting configuration relative to each other and each adhered to at least part of one major surface of said first ply, wherein at least one of said three panels adhered to said major surface in a releasable manner whilst the other of said panels are adhered in a permanent manner wherein edges of said at least one panel abutting with the adjacent edges of said other panels, extend across a region where said multiply assembly is to be sealed to the other portion of the said container.
16. A multiply film assembly as claimed in claim 15 wherein said at least one panel is directly adhered in a releasable manner to said first ply.
17. A multiply film assembly as claimed in claim 15 wherein said at least one panel is adhered in a releasable manner to said first ply indirectly by being adhered to an intermediate ply which is coextensive with said at least one ply.
18. A multiply film assembly as claimed in claim 17 wherein said adhesion in a releasable manner is provided by a release agent between said intermediate ply and said first ply.
19. A multiply film assembly as claimed in any one of claims 15 to 18 wherein said adhesion in the releasable manner is provided by a release agent between said intermediate ply and said at least one panel.