WO2010038080A1

WO2010038080A1 - Overwrap film

Info

Publication number: WO2010038080A1
Application number: PCT/GB2009/051298
Authority: WO
Inventors: Barry Frizell; Wolfgang Zimmerer; John Fell
Original assignee: Innovia Films Limited
Priority date: 2008-10-03
Filing date: 2009-10-02
Publication date: 2010-04-08
Also published as: GB0818122D0

Abstract

The present invention provides a polymeric film (12) or packaging sheet, characterised in that the film or sheet has a tear line (28) formed therein, said tear line arranged as a propagation region for a tear in said film or sheet, wherein said tear propagates upon application of oppositely directed forces in a plane of said film or sheet to corresponding opposite sides of said tear line. The invention also provides a method and apparatus of producing a polymeric film or packaging sheet.

Description

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The present invention relates to an overwrap film and particularly to a polymeπc film for overwrap packaging applications

The invention also concerns packaging sheets generally

The packaging industry requires large quantities of film which protect a packaged product from the atmosphere dirt, grease, etc and provide a degree of protection to the packaged product against impacts Polyolefins are in demand as film-forming materials by virtue of their strength and clarity However, many other substrate films are useful in this connection For convenience this specification will describe mostiy poiyolefinic films, but other substrate films are within the scope of the invention as will be made clear herein

In the field of packaging rigid articles and/or articles which are not susceptible to flexing, for example, CD cases DVD cases, and the like, the use of poiyolefin films is advantageous because they offer excellent shπnk tightening properties

However, it is because of the very same excellent shrink tightening properties that users often experience difficulties in removing the packaging from the article

The film is so tightly wrapped around the article that the user is unable to gain any substantial purchase on the fiim in orαer to tear the film and thereby remove the film from the aricfc The user may resort to using a sharp implement to assist with the opening process but this may then cause damage to the article and negate trie purpose of the film

Similar difficulties may present themselves in connection with other types of packaging sneet paper for example The present invention relates to a film, a method of producing a film, and a device for producing a film, which overcomes or substantially eliminates the aforementioned problem. The invention also concerns packaging sheets which can be easily opened.

According to an aspect of the present invention, there is provided a packaging sheet, characterised in that the sheet has a tear line formed therein, said tear line arranged as a propagation region for a tear in said sheet, wherein said tear propagates upon the application of a force applied to the sheet in the plane of the sheet and in a direction away from the tear line or from a portion thereof wherein the tear line is an oscillating tear line comprising a series of repeat patterns, each of which has a first directional component which is parallel to a straight longitudinal axis running along the length of the tear line and through the centre thereof, and a second directional component which is perpendicular to the said longitudinal axis, and wherein the tear line has a pattern which osculates above and below the longitudina! axis.

Preferably the packaging sheet is a polymeric film. Thus according to a preferred aspect of the present invention, there is provided a polymeric film, characterised in that the film has a tear line formed therein, said tear line arranged as a propagation region for a tear in said film, wherein said tear propagates upon the application of a force applied to the film in the plane of the film and in a direction away from the tear line or from a portion thereof, wherein the tear line is an oscillating tear line comprising a series of repeat patterns, each of which has a first directional component which is parallel to a straight longitudinal axis running along the length of the tear line and through the centre thereof, and a second directional component: which is perpendicular to the said longitudinal axis, and wherein the tear line has a pattern which oscillates above and below the longitudina! axis.

However, the packaging sheet may be of any suitable material, for example paper. Consequently, according to another aspect of the present invention. there is provided a paper packaging sheet characterised in that the sheet has a tear line formed therein said tear line arranged as a propagation region for a tear in said sheet wherein said tear propagates upon the application of a force applied to the sheet in the plane of the sheet and in a direction away from the tear line or from a portion thereof wherein the tear line is an oscillating tear line comprising a series of repeat patterns each of which has a first directional component which is parallel to a straight longitudinal axis running along the length of the tear line and through the centre thereof and a second directional component which is perpendicular to the said longitudinal axis and wherein the tear line has a pattern which oscillates above and below the longitudinal axis

In the description which follows emphasis will be placed on polymeric films as packaging sheets in accordance with the invention However *t will be understood from the foregoing that other types of packaging substrate notably paper are specifically contemplated herein

Preferably the force is a mechanical force more preferably a translational force and most preferably a pulling and/or pushing force

In order to propagate ihe tear the force will generally be applied at a location proximate the tear line and preferably substantially transversely with respect thereto or with respect to a portion thereof

St is envisaged that generally the tear will be caused to propagate by the application of substantially oppositely directed forces Such oppositely directed forces will generally be applied at opposite proximal locations on the film or sheei on esiner siαe oτ tne tear line ana directed in eacn case away from tne tear line or from a portion thereof

Preferably the %ar propagates substantially along the tear l,ηe upcp application of the force(s) Thus it is envisaged that a film in accordance with the invention when placed on a substantially flat surface can be made to tear along the tear line by for example a manual operation in which the thumbs, for example, are placed either side of the tear line and with the application of reasonable pressure sn a direction through the plane of the film or sheet (to maintain grip on the film or sheet) and transversely away from the tear line so that the film or sheet splits in two and so that each spirt portion is effectively pulled apart from the other as the tear propagates along the tear line In final use of the film it is envisaged that the film will be shrink-wrapped around a useful article and that the useful article can be unwrapped sn the manner above described, or indeed by any other suitable application of force effective to cause a tear in the wrapping film to propagate along the tear line In the case of a paper- wrapped article, it is envisaged that the same mechanism of tearing will render the paper-wrapped article easy to open

The invention therefore provides a method for unwrapping a package comprising an article wrapped with tne film of the invention wherein the method comprises the use of manual force to urge apart two sections of the film either side of the tear line

The invention also provides a method for unwrapping a package comprising an article wrapped with the packaging sheet of the invention, wherein the method comprises the use of manual force to urge apart two sections of the sheet either side of the tear line

Preferably the manual urging force comprises bearing down on the film- or sheet-wrapped article (to maintain grip; whilst simultaneously pusntng or pulhng the film or sneet away from the tear line in a direction suostantially transverse with respect to the tear line

The tear line may be continuous or may have a discrete pattern In the event that the tear line is continuous it is preferred in that case that the tear hne be formed as an incomplete perforation snosion trough or .ndentation on the film or sheet - in other words that the film or sheet is not cut right through along a continuous line. In the event that the tear line is discontinuous - ie comprising an intermittent series of perforations, incisions, troughs or indentations separated by regions of substantially uncut film or sheet - it is acceptable (although not always necessary) for the film or sheet to be completely perforated in the cut regions. It will be understood from hereon in that "perforation" need not necessarily mean a perforation right through the film or sheet but also includes perforations which pass into - but not right through - the film or sheet,

Whether the tear line is continuous or discontinuous, it does in any event comprise a series of repeat patterns, each of which has a first directional component which is parallel to a straight longitudinal axis running along the length of the tear line and through the centre thereof, and a second directional component which is perpendicular to the said longitudinal axis The tear line has a pattern which oscillates above and below the said longitudinal axis. Preferably, the tear line is a wavy or zigzag line made up from a series of repeat patterns; waves or wave portions, zigzags or zigzag portions as the case may be. One preferred pattern is a sinusoidal wave.

The tear line is an oscillating tear line. Preferably the tear line is an osciiiating tear line with a repeat unit which itself is oscillating.

By oscillating is preferably meant that the tear line propagates sequentially above and below a longitudinal axis running along the length of the tear line through the centre thereof.

The amount of film or sheet materia! removed (ie cut away) along the length of the tear line can be an important characteristic in controlling the ease with which the film or sheet can be separated along the tear line. Preferably at least about 10%. more preferably at least about 20%, even more preferably at least about 30%, yet more preferably at least about 40% and most preferably at least about 50% - even as high as 60%, 70% or 80% - of the film or sheet may be removed in along the tear line. Clearly there are other factors, such as the nature of the film or sheet material itself and the thickness of the fiim or sheet itself which come into play as well or instead in this connection

The force required to propagate a tear from said tear line is dependent upon not only the configuration of the tear line but also the depth of the tear iine in the case where the tear line is formed from a series of discrete perforations, the force is also dependent upon the space between adjacent perforations and the length of the perforations themselves Thus by altering the above parameters, the force required to open the packaging material to unwrap an article can be altered

According to another aspect of the present invention, there is provided a method of producing a polymeric film in accordance with the above, characterised in that the film has a tear line formed therein said tear line arranged as a propagation region for a tear in said film said method comprising passing said film between a firsi roller and a second roller, urging said second roller against said first roller and forming said tear line in said film by way of cutting elements located about a periphery of said second roller removing material from said film

According to yet another aspect of the present invention, there is provided a method of producing a packaging sheet in accordance with the above, characterised in that the sheet has a tear line formed therein said tear line arranged as a propagation region for a tear in said sheet sasd method comprising passing said sheet between a first roller ana a second roller urging said second roller against said first roller and forming said tear line in said sheet by way of cutting elements located about a penpnery of said second roϋer remov.ng material from said sneet

According to a further aspect of the present indention there is provided an apparatus for producing a polymeric film or packaging sheet in accordance with trie aoove cnaracteriseσ m mat ine film or sheet has a tear line foimed therein, said tear line arranged as a propagation region for a tear in said film or sheet, said apparatus comprising a first roller a second roller including cutting elements located about a surface thereon means for urging said second roller against first roller, wherein said film or sheet is arranged to pass between said first and second rollers and wherein said second roller is arranged to form said tear line in said film or sheet by way of said cutting elements removing material from said film or sheet

The present invention still further provides a package comprising an article, such as a carton, box, tin, CD or DVD case, wrapped in a film or sheet as hereinbefore described

The invention also provides a package of stacked articles wrapped in the film or sheet of the invention For example, Post-It^TIV1 notes or stacks of paper may be wrapped in the film or sheet of the invention in an easy-to-open manner Thus in one embodiment the invention provides a ream wrap package comprising a stack of paper wrapped in the film or sheet of the invention

A tear line is formed in said film or sheet by passing the film or sheet between two rollers One of the rollers is a cutting roller and is provided with cutting teeth for removing material from the film or sheet to form the tear line

In the apparatus of the present invention for forming a tear hne in a film or sheet, the cutting roller is urged into engagement with the other roller by a biasing means and the film or sheet passes between the two As will be appreciated the depth of cut made by tne cutting teeth of the cutting rolϊer in forming said perforations will depend upon the force with which the biasing means urges the cutting roller into engagement with the other roiier

Preferably the force exerted by the biasing means may oe altered by an operator in order to alter the depth of cut made by the cutting roller and thereby altering the depth of trie fear line A cut-depth adjustment τieans which is linked to the biasing means may be provided to allow the operator to adjust the force applied by the biasing means

In a preferable arrangement, the biasing means may comprise a pneumatic/hydraulic arrangement whereby the depth of cut is dependent upon air/fluid pressure applied to the cutting roller by the biasing means

The films or sheets used in accordance wth the present invention can be of a variety of thicknesses according to the application requirements For example they can be from about 10 to about 240μm thick and preferably from about 50 to about 90μm thick The tear line in the film is preferably of a narrower gauge than the rest of the film - for example 1 %, 2%, 5%, 10%, 20% or 50% narrower than the bulk of the film, or the tear line may extend all or substantially all the way through the film When paper sheets are used these may be considerably thicker

The films used in the present invention, prior to deposition of any coating and/or skin or lamination layer may comprise any suitable polymeric filmic substrate such as films made from biopolymers such as any of those described herein [preferably polylactic, polygalactic and/or cellulosic films (e g microbial and/or regenerated cellulose film)] , thermoplastic films, polymeric films (for example films comprising polyolefins [e g polypropylene and/or polyethylene] polyurethanes polyvinylhalides [e g PVC] polyesters [e g polyethylene terephthalate-PET], polyamides [e g nylons] and/or non- hydrocarbon polymers) , and/or multilayer and/or composite sheets %rmed by any suitable combinations and/or mixtures of thereof Suitable filmic substrates therefore include poϊyolefirsic films but also polyester films polyurethane films cellulosic and PLA films

The films of the present invention may consist of only one ϊayer or may comprise a plurality of layers Layers when oresent can be combined by lamination and/or co-extrusion and/or coating and/or melt coat extrusion Films may be otherwise treated (for example by corona discharge treatment; to improve certain characteristics of trie film pπntabiiity or coating aαnesion for example The films may also be laminated to oiher materials - paper for example to form packaging sheets in accordance with the invention

The films of the invention may comprise one or more additive materials such as dyes pigments colorants metallised and/or pseudo metallised coatings (e g aluminium), lubricants, antioxidants surface-active agents, stiffening aids, gloss-improvers prodegradants UV attenuating materials (e g UV light stabilisers), sealability additives tackifiers anti-blocking agents, additives to improve ink adhesion and/or portability cross-linking agents, anti-slip and/or anti-block additives and the like

The present invention is described further hereinafter by way of example only, with reference to the accompanying drawings in which

Fig 1 illustrates a side elevation of a portion of a biaxially oriented propylene polymer film substrate 1

Fig 2 illustrates a side elevation of a similar film portion having on a surface 2 of substrate 1 a heat-sealable layer 3 formed from an etrtySβne-butene-1 random copolymer

Fig 3 illustrates a side elevation of a similar film portion having on a second surface 4 of substrate 1 a heat-sealable layer 5 formed from an ethylene- butene-1 random copolymer

Fig 4 illustrates a schematic side elevation of an apparatus for forming a tear line in the film of any of Figs 1 to 3

Fig 5 illustrates a schematic perpendicular view of said lines of weakness formed in a fnm ana

Fig 6 illustrates a schematic perpendicular view of an article wrapped with a film accordirg to the present invention Figs 1 to 3 are self-explanatory and no further description is reαuired

Fig 4 illustrates a cutting apparatus 10 for forming a tear line in a film 12 Note that the film may be any of the films as illustrated in Figs 1 to 3 or any other suitable film, or indeed sheet such as paoer

The cutting apparatus 10 comprises a first roller 14 and a second roller 16 arranged to rotate in opposite directions and between which the film is arranged to pass The second roller 16 is mounted upon a support member 18 which extends from a region of a housing 20 of said cutting apparatus 10

There is further provided a biasing means 22 which is arranged to urge the second roller 16 against the first roller 14 Thus when the first and second rollers 14, 16 rotate in directions indicated by arrows A and B respectively the film is arranged to travel in a direction illustrated by arrow C

The second roller 16 comprises cutting teeth 24 in a peripheral surface and these teeth are arranged to remove material from the film passing between the first and second rollers 14, 16 thereby forming a tear line

Advantageously such a tear line is formed by a discontinuous series of perforations

It will be appreciated that the force exerted by the biasing means 22 upon the second roiler 16 will influence the depth of material relieved frorτ> the ^film 12 by the cutting teeth 24 of the second roller 16

Preferably the force exeried oy tne biasing means 22 is adjustable so that the depth of material removed from the film can be altered A cut-depth adjustment means 26 is provided to aliov/ tne force exerted by the biasing means 22 to be adjusted

In a preferred embodiment the biasing means 22 comprises a pneumatic arrangement whereby the depth of cut is dependent upon air pressure appiieα to said second roller 16 by said biasing means By adjusting the cut-depth adjustment means 26 a user can adjust the air pressure applied by the biasing means 22

As will be appreciated, the force required to propagate a tear from the tear line formed in the film will depend, on the one hand, upon the depth of cut in the tear line and on the other hand upon the length of each cut and the space between adjacent cuts, i e the perforation period

As noted above the cut depth is controlled by the force exerted upon the second roller 16 by the biasing means The perforation period, however, depends upon the configuration of the cutting teeth 24 of the second roller 16 Therefore, to form different cut length/space length ratios, different configurations of cutting teeth 24 will be required

Fig 5 illustrates a film 12 formed with a tear line 28 As can be seen in the illustration, the tear line 28 is formed from a plurality of discrete perforations 30 and has a substantially sinusoidal waveform configuration in a plane of the film 12 The configuration need not, however, be sinusoidal and any suitable configuration may be adopted

The arrows X X ₁ Y and Y in Fig 5 illustrate the two possible directions of application of forces by a user to cause propagation of a tear from the tear line In the first case, a user may apply a first force in the plane of the film 12 and on one side of the tear line 28 in a direction X and a second force in the plane of the film 12 and on the other side of the tear line in an opposite direction X In the second case a user may apply a first force in the plane of the film ana on one side of the teai line 28 in a direction Y (perpendicular to direction X) and a second force in the plane of the film 12 and on the other side of the tear line "ti an opposite direction ^v (perpendcular to director X j

Fig 6 illustrates a film 12 having a tea^r line 28 formed therein used as shrink- wrap packaging for an article 32 which comprises a CD case

Claims

CLAMS

1 A packaging sheet characterised in that the sheet has a tear line formed therein said tear line arranged as a propagation region for a tear in said sheet wherein said tear propagates upon the application of a force applied to the sheet in the plane of the sheet and in a direction away from the tear line or from a portion thereof wherein the tear line is an oscillating tear line comprising a series of repeat patterns each of which has a first directional component which is parallel to a straight longitudinal axis running along the length of the tear line and through the centre thereof and a second directional component which is perpendicular to the said longitudinal axis and wherein the tear line has a pattern which oscillates above and below the longitudinal axis

2 A packaging sheet according to claim 1 wherein the sheet comprises a polymeric film

3 A packaging sheet according to claim 1 or claim 2 wherein the sheet comprises paper

4 A packaging sheet according to any one of claims 1 to 3 wherein the force is a mechanical force

5 A packagsrg sieet according to any one of claims 1 to 4 whe^reιn in order to propagate the tear the force is applied at a location proximate the tear line

6 A packaging sheet according to any one of claims 1 to 5 wherein in order to propagate tne tear the force .s applied substantially transversely with respect to the tear line or with respect to a portion thereof

7. A packaging sheet according to any one of claims 1 to 8 wherein the tear line comprises a repeat unit which itself is oscillating.

8. A packaging sheet according to any one of claims 1 to 7 wherein the tear line is a wavy or zigzag line

9. A packaging sheet according to any one of claims 1 to 8 wherein the tear line propagates sequentially above and below the longitudinal axis.

10. A package comprising an article wrapped in a packaging sheet according to any one of claims 1 to 9.

1 1. A package according to claim 10 wherein the article is selected from a box, tin, carton, CD or DVD case, or from a plurality of stacked articles.

12. A ream wrap package according to claim 1 1 .

13. A method for unwrapping the package of any one of claims 10 to 12 comprising manuaS urging of the sheet away from the tear line,

14, A method according to claim 13 wherein the manual urging force comprises bearing down on the sheet-wrapped article (to maintain grip) whilst simultaneously pushing or pulling the sheet away from the tear line in a direction substantially transverse with respect to the tear line