EP2181936A1

EP2181936A1 - A lid

Info

Publication number: EP2181936A1
Application number: EP09174950A
Authority: EP
Inventors: Richard Smith; Jeremy Woodcock
Original assignee: Paragon Labels Ltd
Current assignee: Paragon Labels Ltd
Priority date: 2008-11-03
Filing date: 2009-11-03
Publication date: 2010-05-05
Also published as: GB0820145D0; GB0901660D0

Abstract

A lid (30) for resealable adhesive attachment to trays, punnets and the like, the lid comprising an upper flexible film layer (20) dimensioned so as to substantially cover an opening in a tray or punnet, a layer of adhesive (24) covering substantially the entire lower face of the upper layer, and a lower flexible film layer (22) of generally smaller dimensions than the upper layer and attached to the upper layer by the adhesive such that a peripheral area of adhesive remains exposed for resealable adhesive securement to a lip or rim of a tray or punnet, wherein the adhesive retains its adhesive properties once the lid is lifted to permit a subsequent sealing operation to occur.

Description

The present invention relates to a lid. More particularly, the present invention relates to a lid for resealable adhesive attachment to trays, punnets and the like. The invention further relates to a web of film comprising a plurality of such lids, and a method of manufacturing a web of such lids.
Conventionally, trays or punnets of fresh produce, typically fruits such as strawberries, raspberries, peaches, etc. have semi-rigid or rigid lids that clip onto the top of the punnet using an interference type fit. Such arrangements have a number of disadvantages.
Firstly, and perhaps most importantly, the nature and shape of the material from which the punnet and lid are manufactured tends to result in a connection of the tray that is either too difficult or too easy to separate. In practical terms, this means that often purchasers will lift the tray by the lid and at some point during the lifting operation, the tray will fall away, spilling the contents thereof. Where this happens in a supermarket, a spillage on the floor of soft fruit represents a slipping hazard when such fruits are trodden on. Supermarkets in the UK are known to pay significant amounts of money each year to settle injury claims as a result of such spillages.
In addition, in those instances where the lid is difficult to separate from the tray, a user will often squash the sides of the tray to release the lid and, as a consequence, damage the contents of the tray.
Furthermore, the rigid or semi-rigid lids require a separate self-adhesive label or labels thereon in order to provide product information, use by dates, weights and special offer information. It is costly for fruit packers, who may be packing fruit for a period of a few days or weeks, when a particular fruit is ripe, to order short runs of lids with various combinations of labels applied in order to provide particular use by date or other information. Such information can quickly become out of date, (eg. use by dates) leading to a significant wastage of material if the expected number of trays are not filled with product.
The present invention seeks to overcome, or at least mitigate, one or more of the above disadvantages of the prior art.
Accordingly, one aspect of the present invention provides a lid for resealable adhesive attachment to trays, punnets and the like, the lid comprising an upper flexible film layer dimensioned so as to substantially cover an opening in a tray or punnet, a layer of adhesive covering substantially the entire lower face of the upper layer, and a lower flexible film layer of generally smaller dimensions than the upper layer and attached to the upper layer by the adhesive such that a peripheral area of adhesive remains exposed for resealable adhesive securement to a lip or rim of a tray or punnet, wherein the adhesive retains its adhesive properties once the lid is lifted to permit a subsequent sealing operation to occur.
Various materials may be used for the film layer but plastics such as polyethylene terephthalate (PET) and polypropylene (PP) are preferred. Particularly preferred is PP a upper layer and a PET lower layer as this provides a dimensionally stable and cost-effective lid. The upper layer preferably has a thickness of 25µm to 100µm, more preferably 40µm to 70µm. The lower layer has a thickness of 20µm to 100µm, preferably 25µm to 50µm.
The use of water borne adhesive and/or acrylic adhesive is preferred as such adhesives have the desired resealable properties, and direct food contact safe versions are available.
The lid may include a tab to make the peel-back operation easier for the end user and/or additional wall tabs to secure the lid to side walls of a tray or punnet.
A second aspect of the present invention provides a lid for non-resealable adhesive attachment to trays, punnets and the like, the lid comprising:

an upper flexible film layer dimensioned so as to substantially cover an opening in a tray or punnet;
a layer of adhesive covering substantially the entire lower face of the upper layer, and;
a lower flexible film layer of generally smaller dimensions than the upper layer and attached to the upper layer by the adhesive, which adhesive is preferably approved for direct food contact.

Various materials may be used for the film layer but plastics such as polyethylene terephthalate (PET) and polypropylene (PP) are preferred. Particularly preferred is PP a upper layer and a PET lower layer as this provides a dimensionally stable and cost-effective lid. The upper layer preferably has a thickness of 25µm to 100µm, more preferably 40µm to 70µm. The lower layer has a thickness of 20µm to 100µm, preferably 25µm to 50µm.
The use of water borne adhesive and/or acrylic adhesive is preferred as such adhesives have the desired adhesive properties, and direct food contact safe versions are available.
The lid may include a tab to make the peel-back operation easier for the end user and/or additional wall tabs to secure the lid to side walls of a tray or punnet.
A third aspect of the present invention provides a film laminate web comprising a plurality of lids according of the first or second aspects of the invention
A fourth aspect of the present invention provides a method of manufacturing a web of lids for non-resealable adhesive attachment to trays, punnets and the like, the method comprising the steps of providing a feed of flexible film laminate comprising an upper flexible film layer, a lower flexible film layer and an adhesive having properties such that it may not be re-adhered to a surface once lifted therefrom covering substantially all of the internal faces of the upper and lower films, cutting an outline cut of a lid in the upper film layer, cutting an inner cut in the lower layer generally substantially concentrically within the outline cut of the upper layer.
A fifth aspect of the present invention provides a method of manufacturing a web of lids for resealable adhesive attachment to trays, punnets and the like, the method comprising the steps of providing a feed of flexible film laminate comprising an upper flexible film layer, a lower flexible film layer and an adhesive having properties such that it may be re-adhered to a surface once lifted therefrom covering substantially all of the internal faces of the upper and lower films, cutting an outline cut of a lid in the upper film layer, cutting an inner cut in the lower layer generally substantially concentrically within the outline cut of the upper layer.
Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIGURE 1 is a schematic side view of a press for manufacturing lids according to an embodiment of the present invention;
FIGURE 2 is a plan view of a portion of a web of film laminate incorporating a plurality of lids according to an embodiment of the present invention;
FIGURES 3 and 4 are cross-sectional views through portions of the web of Figure 2 along the planes 3-3 and 4-4 respectively in which the thicknesses of the layers are not to scale;
FIGURE 5 is a perspective view of a lid being applied to a tray;
FIGURE 6 is a plan view of a web of film laminate incorporating lids according to another embodiment of the present invention; and
FIGURE 7 is a cross-sectional view through a portion of the film of Figure 6 along the plane 7-7 in which the thicknesses of the layers are not to scale.

FIGURE 8 is a plan view of a portion of a web of film laminate incorporating a plurality of lids according to another embodiment of the present invention.
With reference to Figure 1, a press 10 is shown schematically converting an infeed roll 12 of film laminate material into a rewind roll 14 of laminate that has been printed and die-cut to form a web 15 of lids according to an embodiment of the present invention.
The press is typically a UV flexo press such as a press of the type manufactured by MPS Systems BV of Didam, Netherlands. In this embodiment the press 10 comprises ten print stations indicated generally at 16 that may be used to apply inks of differing colours, varnishes, lacquers and other coatings such as anti-mist coatings, for example. The press 10 further comprises a die-cutting station 18 downstream of the print stations 16 as described in more detail below. The press 10 additionally comprises a drive mechanism and control system (not shown), as is well known in the art.
In this embodiment, the infeed roll 12 comprises a laminate web 15 of transparent flexible plastics sheet material comprising an upper layer of polypropylene (PP) having a thickness of 50µm and a lower liner layer of polyethylene terephthalate (PET) having a thickness of 30µm. In other embodiments, the materials and thicknesses may be altered as required.
The upper and lower layers 20, 22 are releasably secured together by an adhesive layer 24 covering the entire areas of the upper and lower layers facing each other. In this embodiment, the adhesive is an acrylic water borne adhesive that is ISEGA approved for direct contact with food, including dry and moist foods and fatty foods with a fat reduction factor of at least 3 (in accordance with EC directive 85/572/EEC). One example of such an adhesive is provided by UPM Raflatac of Scarborough, United Kingdom under the designation RP74. In other embodiments, other suitable adhesives may be used, but it is important for food packaging, in particular the packaging of moist, fresh or fatty foods such as fruit, vegetables and bakery items that the adhesive is approved for direct contact, since it cannot be guaranteed that during the course of opening the tray and removing food items from the tray, that the food items will not come in contact with the adhesive layer.
The RP74 adhesive is typically used for adhering clear labels to a packaging of toiletries such as shampoo bottles and the like, where it is not anticipated that the label will be peeled back and resealed. However, the applicant has recognised that at typical chiller cabinet/refrigerator temperatures (0°-10°C) in which fresh produce is transported and stored before opening, this adhesive exhibits properties that are particularly desirable for enabling resealing to occur. In particular, when peeled back, the adhesive that is exposed remains tacky in order that when again placed in contact with the lip it will re-adhere. At temperatures above this level re-adhesion may be achieved, but the adhesive 24 is more liable to "creep" if weight is placed on top of the lid. Furthermore, the adhesive 24 is able to retain a significant level of adhesion even if the interface between the adhesive and lip of the tray has been contaminated by a certain amount of moisture.
In operation, manufacturing of the lids 30 occurs on the press 10 as a continuous process at speeds of up to 100 metres per minute, but typically in the range of 60 to 80 metres per minute. Each print station 16 is used to apply a different colour ink. Typically, the first print station is used to apply text that would be visible from the underside of the lid through the film (i.e. it is printed in reverse), the next print station prints a base colour (usually white) and then the subsequent print stations print further colours on top of this. Consequently, the product information and promotional information 25 that would previously have been present on a separately applied label or labels on a semi-rigid punnet lid is printed directly on the lid itself.
The inks used in the printing process are typically UV cured and have low odour and low migration properties to prevent the contents of the trays to which they are to be applied being tainted by the ink.
In addition, in other embodiments, turn bars may be incorporated into the press in order that coatings such as anti-mist coatings may be printed on the underside of the lids 30 at print stations 16.
In this embodiment, once the printing of the ink is complete, die-cutting takes place. With reference to Figures 2, 3 and 4, at the die-cutting station 18 an outline cut 32 of the lid is made through the upper layer 20 only, except where a tab 34 is provided. In this location, the outline cut 32 is interrupted, but a further cut 35 to define the tab extends beyond the tray opening. The outline cut 32 substantially corresponds to the dimensions of a lip 60 of a tray 52 to which the label is to be applied (see Figure 5).
The web 15 is then cut from the reverse or underside through just the lower layer 22 to form a continuous inner cut 36 that is concentrically arranged within the lid outline cut 32. An area of overlap 38 extending around the periphery of the lid is provided laterally between the two cuts 32 and 36. This maintains an adhesive connection of the lid 30 to the remaining portion of the web 15. The width of this overlap portion 38 is typically selected so that the lower layer 22 covers substantially all of the portion of the lid 30 that extends over the opening of the tray. This prevents the contents of the tray from adhering to the adhesive once the lid is applied.
The die-cutting station 18 carries out a further tab cut 40 in the lower layer 22 that follows the path of the corresponding cut 35 in the upper layer 20 in order to form a two layer tab 34. The die-cutting station also cuts an inner tab cut 41 that follows the outline of the tray lip, such that this two layer tab terminates at the area where adhesive 24 is required to be revealed.
It will be noted that the cuts 35 and 40 to form the tab terminate in ends 42 that curve away from the tray outline cut so that when the lid 30 is separated from the remainder of the web 15 the lower layer of the tab 34 remains in place.
The die-cutting unit 18 may, in other embodiments, also be positioned in other locations further upstream on the press, multiple stations provided, or located in a separate location from the press.
In other embodiments, the die-cutting station may be used to cut one or more holes in the lid, depending upon the product to be packed in order to provide for an appropriate modified atmosphere within the tray 52. In such embodiments, a shock air unit may then be used to separate the material that is to be removed to form the hole from the lid 30.
For certain fresh produce, the hole size required to provide a suitable modified atmosphere may be so small it is not be feasible using die-cutting apparatus. In such instances, the holes may be cut using laser cutting or other suitable means.
Once the die-cutting operations are complete, the web 15 is wound onto rewind roll 14. Thereafter it may be supplied directly to a packer or subject to further operations such as longitudinal slitting if the web has multiple lids cut in a side by side arrangement and the packer only has a single row lidding machine.
Referring now to Figure 5, a portion of a lidding machine 50 for applying the lids 30 to trays 52 is illustrated. The lidding machine is based upon a modified standard label applicator of the type supplied by Herma UK of Haverhill, Suffolk, United Kingdom. The lidding machine 50 comprises a tray drive conveyor 54, guides 56 either side of the tray (only one visible in Figure 5) and a lid applicator beak 58 that sharply diverts the web 15 through an angle of over 90° such that the lids 30 peel off from the web and are placed on the trays 52 with the peripheral area of adhesive 24 that is revealed overlying a lip 60 of the tray. This peripheral area has a typical width of 5mm - 10mm, and is dictated by the width of the lip 60 and the tolerance in placement of the lid 30.
A pressure roller 62 is provided to ensure a good adhesion of the adhesive 24 to the lip 60. The remaining web 15 is wound onto a waste roll (not visible) for recycling or disposal.
The lidding machine 50 further comprises a suitable control mechanism (not shown) that is able to detect the position of trays 52 and lids 30 and control the drive of the web 15 and the conveyor 54 to ensure an accurate placement of the lids 30 on the lip 60 (typically to within plus or minus 0.5mm).
The lidding machine 50 may further be provided with an in-line print station (not shown) to print variable information on the lids 30. This may be "use-by" information, in which case it need only vary once per day, batch information or grower information, in which case it is only a limited variability, or weight information in the case that the contents of the tray are being sold on a catchweight basis. In this latter case, the print station has a data link to a weighing station (not shown) and the controller of the lidding machine 50 such that a particular tray 52 of product is weighed, the data is transmitted to the print station and appropriate information printed on a lid 30 that is ultimately to be placed on that tray. Subsequently the controller ensures the correct lid is applied to that tray 52.
Turning to Figures 6 and 7, a second embodiment of a lid according to the present invention is shown. In this embodiment, like parts are illustrated by similar reference numerals but with the addition of prefix "1". The lid 130 of this embodiment is generally formed from the same materials and in the same manner as the lids 30 of the first embodiment. The only significant difference is in the tab arrangement.
In this embodiment, rather than providing a tab that extends beyond the lip 60 of the corresponding tray 52, a corner of the lid is omitted by cutting through the entire depth of the lid so that when the lid 130 is placed on the tray, a user can insert a finger between the lip 60 and an edge 144 that defines the cut away portion and thus engage the lid 130 and peel it back.
Clearly, the use of such an arrangement is only desirable in circumstances where the contents of the tray are larger than the hole formed in the lid and so cannot fall out, and in circumstances where the hole would not compromise the shelf life of the products being packaged within the tray.
The lid may be applied to a tray using the same method and apparatus as outlined above.
With reference to Figure 8, an alternative embodiment of the invention is illustrated. Like parts are again illustrated by similar reference numerals but with the prefix "2" rather than "1". In this embodiment, two adhesive wall tabs 233 are cut from the upper layer 220 on the lid 230 such that when the lid is peeled off the web, adhesive is revealed to secure the lid firmly to the side walls of the tray when 'ploughed' down by an applicator. This allows trays to be stacked more rapidly after lidding without fear of the lids collapsing. The wall tabs 233 may vary in length but will typically be 16-21mm in length (dependent upon the "overhang" of the lip, and desired strength of the connection).
The lid 230 is provided with two lines of weakness in the form of perforations 237 cut through the upper layer 220, allowing a portion of it to be partially torn away in order to allow access to the contents. In this embodiment, the perforations 237 comprise a series of 2mm cuts with 0.3mm ties, but in other embodiments may be a variety of other lengths. Each line of perforations 237 commences at its intersection with the edge of the lid 230 with a curved cut 245 that promotes tearing of the perforations in preference to other peeling/failure modes.
In other embodiments, the lines of weakness may take some other form, for example a scored line in a material such as paper.
In this embodiment, the perforations 237 are dimensioned to run down the centre of the lip of the tray 52 so that the torn back portion can be resealed to the exposed half of the lip 60 whilst the non-removed portion of the lid 230 remains attached to the other half of the lip. The wall tabs 233 ensure that the non-removed portion of the lid 230 remains in place. Alternatively, the perforations 237 may be dimensioned to run inside the lip 60 of the tray or outside the lip along the wall tabs 233.
In variants, the perforations may run the full length of the lid 230 or wall tab 233 so that the torn away portion of the lid can easily be fully detached. The number and/or position of the wall tabs 233 may be altered - for example, two tabs may be provided on each side.
A peel tab 234 is provided so that the lid 230 can easily be grasped and torn along the perforated lines 237. The peel tab 234 has a curved intersection with the main part of the lid to minimise the risk of tearing occurring at the point of attachment.
This lid arrangement allows resealing of the tray whilst giving higher protection against undetected tampering, since it is apparent from the state of the perforations 237 if the lid 230 has previously been opened. Prior art punnet lids of the type described above provide no evidence of tampering.
Air holes may be cut into the lid using the same die(s) used to cut the outline of the lid to optimise the atmosphere in the tray to maximise to shelf life of the product contained within. Waste material may be removed using shock air technology.
In a further embodiment (not shown), a single use lid, of either this or a previously described shape, with a more permanent adhesive securing the lid to the tray. Such an adhesive is applicable as a replacement for heat-sealed lids for use with, for example, trays containing frozen ready meals or pre-prepared or dried foods. Product information being printed directly on the label dispenses with the need for a separate paperboard sleeve or other covering such as is currently used for such products, thereby saving cost and raw materials. A base colour may be printed over the whole of the lid, thus rendering it opaque if required. Alternatively, an opaque material such as a suitable polyethylene terephthalate (PET) or polypropylene (PP) film could be used.
A suitable adhesive for this purpose may be a permanent acrylic water based adhesive that has approval for direct food contact. An example of such an adhesive is that produced by UPM Raflatac of Scarborough, United Kingdom under the designation RP77. This adhesive is primarily intended for labelling high density polyethylene drums and other rough substrates, but has been found to be useful in the present application.
It should be understood that numerous changes may be made within the scope of the present invention. For example, different materials may be used for the upper and lower film layers such as amorphous polyethylene terephthalate (APET) or recycled polyethylene terephthalate (RPET) or biodegradable/recyclable material such as plant based materials including polylactic acid (PLA), cellulose products such as Natureflex^RTM, or paper products. The same material may be used for both layers. The thickness of the layers may be varied. The lids may be used in conjunction with other food products to be packaged instead of fruit and vegetables, such as snack products, cooked meats, pastries, bread products and the like. The lid may be used in non-food applications, in which case use of food contact safe adhesive would not be necessary. The laminate may be formed from more than two film layers. The laminate may be formed in-line on the press. The tab or cut-away portion may be provided at other locations in the lid. Further suitable adhesives that have been identified include UV cured hot melt adhesives, such as AP1000 from Ritrama of Eccles, Manchester, UK or XO76 from UPM Raflatac, or an acrylic solvent adhesive, such as S517N from Fasson of Raunds, Northhamptonshire, UK, all in conjunction with a PP top layer and a PET lower layer. The AP1000 ahesive has been found to be less permanent (more resealable) than either XO76 or S517N.

Claims

A lid for resealable adhesive attachment to trays, punnets and the like, the lid comprising:
an upper flexible film layer dimensioned so as to substantially cover an opening in a tray or punnet;

a layer of adhesive covering substantially the entire lower face of the upper layer, and;

a lower flexible film layer of generally smaller dimensions than the upper layer and attached to the upper layer by the adhesive such that a peripheral area of adhesive remains exposed for resealable adhesive securement to a lip or rim of a tray or punnet, wherein the adhesive retains its adhesive properties once the lid is lifted to permit a subsequent sealing operation to occur.
A lid according to claim 1 wherein the upper layer is formed from a plastics material, preferably polyethylene terephthalate (PET) or polypropylene (PP), and preferably or alternatively wherein the lower layer is formed from a plastics material, preferably polyethylene terephthalate (PET) or polypropylene (PP).
A lid according to any preceding claim wherein the adhesive is a water borne adhesive and preferably or alternatively wherein the adhesive is an acrylic adhesive.
A lid according to any preceding claim wherein the adhesive is approved for direct food contact and preferably or alternatively wherein the adhesive has a fat reduction factor of at least three according to EC directive 85/572/EEC.
A lid according to any preceding claim wherein the upper layer has a thickness in the range of 25µm to 100µm, preferably 40µm to 75 µm and preferably or alternatively wherein the lower layer has a thickness in the range of 20µm to 100µm, preferably 25µm to 50µm.
A lid according to any preceding claim further comprising indicia printed directly on to the upper layer, preferably wherein the indicia comprise one or more layers of low odour and/or low migration ink.
A lid according to any preceding claim further comprising a tab dimensioned to project beyond a lip of a tray or punnet to which the lid is to be attached to facilitate the peeling open of the lid, preferably wherein the tab comprises the upper and lower film layers.
A lid according to any preceding claim wherein the lid comprises an edge dimensioned to be set back from a lip of the punnet or tray to be covered so as to facilitate the peeling open of the lid.
A lid according to any preceding claim further comprising a wall tab dimensioned to project beyond a lip of a punnet or tray to which the lid is to be attached to allow the lid to be attached to a side wall of said punnet or tray, preferably wherein the lid further comprises a line of weakness positioned in order to allow a portion of the lid to be wholly or partially separated from the wall tab, even more preferably wherein the line of weakness runs substantially parallel to a side of the punnet or tray.
A lid according to claim 9 comprising a wall tab on two opposing sides of the lid, each with a corresponding line of weakness.
A lid according to any of claims 9 or 10 wherein the line of weakness comprises a series of perforations.
A tray with a lid according to any of claims 9 to 11 wherein the line or lines of weakness is/are configured to be positioned in the centre of a lip of the tray.
A lid for non-resealable adhesive attachment to trays, punnets and the like, the lid comprising:
an upper flexible film layer dimensioned so as to substantially cover an opening in a tray or punnet;

a layer of adhesive covering substantially the entire lower face of the upper layer, and;

a lower flexible film layer of generally smaller dimensions than the upper layer and attached to the upper layer by the adhesive, wherein the adhesive is approved for direct food contact.
A film laminate web comprising a plurality of lids according to any preceding claim, preferably wherein the lids are adhesively secured to the web by the peripheral area of adhesive to be subsequently secured to a lip of a tray or punnet.
A method of manufacturing a web of lids for resealable adhesive attachment to trays, punnets and the like, the method comprising the steps of:
a) providing a feed of flexible film laminate comprising an upper flexible film layer, a lower flexible film layer and an adhesive having properties such that it may be re-adhered to a surface once lifted therefrom covering substantially all of the internal faces of the upper and lower films;

b) cutting an outline cut of a lid in the upper film layer;

c) cutting an inner cut in the lower layer generally substantially concentrically within the outline of the upper layer, preferably wherein in step b) one or more wall tabs dimensioned to project beyond a lip of a punnet or tray to which the lid is to be attached are cut, more preferably wherein in step b) one or more lines of weakness are made.
A method according to any one of claims 15 further comprising a step after step a) of printing the film with one or more layers of ink and preferably or alternatively wherein in steps b) and/or c) a tab dimensioned to project beyond a lip of a tray to which the lid is to be attached is cut and further preferably or alternatively wherein the steps are continuous.