WO2011124926A2 - Naked collation package - Google Patents

Abstract

The invention is concerned with a naked collation package comprising an arrangement of individual packages, individually packaged in a polyolefinic filmic material, that are packed together in said naked collation package in a naked collation film, wherein the naked collation film comprises a sealable polyolefin film having a polyolefinic core layer C, an optional polyolefinic inner sealing layer B and a polyester outer sealing layer A, the polyolefinic material of the inner sealing layer B being selected for sealing incompatibility with the filmic polyolefinic material of the individual packages under a specified sealing condition, and the polyester material of the outer sealing layer A being selected for sealing compatibility with A and for sealing compatibility with B under the selected sealing condition, the individual packages being arranged in an ordered configuration inside the package and with the naked collation film wrapped around the ordered configuration of individual packages.

Description

NAKED COLLATION PACKAGE

The present invention relates to a naked collation package and to a method for its manufacture.

Naked collation is an effective way to reduce packaging costs and materials. When a number of individually packaged articles (cigarette packs, for example) are to be grouped together and packaged as a larger bundle for distribution or for bulk retail, it is usual for the individual packages to be placed in a larger box or carton, before then being wrapped. Naked collation eliminates the need for the box or carton. However, one of the problems of naked collation in film wrapping is that in generating the collated package it is necessary to seal the film package. This raises the prospect of the collated package film sealing not only to itself but also to the film used to wrap each individual packet. In the cigarette industry, wherein the individual packs tend to be wrapped in polypropylene film, this is a particular problem. The manufacturer may wish to use polypropylene film for its collated bundle, taking advantage of the favourable optical and mechanical properties of such films, but in that case risks sealing the collation film also to the film of the individual packs. Such problems have in the past been addressed by providing the polypropylenic overwrap film for naked collation with an acrylic coating, which seals well to itself but not to the polypropylene wrapping of the individual packs. However, acrylic coatings add cost to the film manufacturing process, both in terms of the material used to provide the coating and, perhaps more importantly, in necessitating a coating operation following extrusion of the film.

WO-A-03/089336 discloses a method of packing packets of cigarettes wherein an ordered group of individual packets is packed solely in a sheet of transparent heat-seal plastic packing material, which is folded about the ordered group to form a tubular wrapping. A girth seal is then provided to seal the tube, and envelope seals at each end of the package. Shrink naked collation refers in the art to this type of package wherein the film is shrinkable to wrap more tightly the collated packets once sealed.

US Patent No. 6358579 discloses another naked collation type packaging wherein the packaging film is a polyester film. The sealable outer layers comprise copolyester and the combined film is said to seal to itself, but not to the biaxially oriented polypropylene films of the individual packages. However, it has been found that the use of polyester layers in such arrangements is problematic as it is difficult to control the degree of shrinkage of those layers. Further, depending on the nature of the products which are packaged, the water vapour transition rate through polyester layers may be unacceptably high.

A multipack system in which individual packaging takes place in a biaxially stretch-oriented polypropylene film having modified polyolefinic heat-sealing layers is disclosed in DE3635928. EP1431028 discloses a polypropylene film or laminate, in which if the film/laminate is heat-sealable the inside of the film is coated locally with heat- resistant varnish over areas affected by sealing, whereas if the film/laminate is not heat-sealable a heat-sealable varnish is applied to the sealing points.

EP1840029 discloses a multilayer polyolefinic collation film in which the melting point of the outer layer on one side of the film is higher than the melting point of the outer layer on the other side of the film.

It is an object of the present invention to provide an improved naked collation film in polyolefin packaging, in particular one which avoids the need for an acrylic coating. It is also an object of the present invention to provide a naked collation film having a low water vapour transition rate and a controllable degree of shrinkage.

According to the present invention there is provided a method for forming a naked collation package comprising:

providing an arrangement of packages individually wrapped in a filmic polyolefinic material;

providing a naked collation film for nakedly wrapping said individually wrapped packages, the naked collation film comprising a polyolefinic core layer C, a polyester outer sealing layer A on the outer surface of the naked collation film, and an inner sealing layer A' on the inner surface of the naked collation film, the polyester material of the outer sealing layer A being selected for sealing compatibility with A and A' and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the material of the inner sealing layer being selected for sealing compatibility with A' and A and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition;

arranging the individually wrapped packages in an ordered configuration in contact with the naked collation film;

wrapping the naked collation film around the ordered configuration of individually wrapped packages; and

sealing the naked collation film.

The films employed in the present invention exhibit low water vapour transition rates, enabling them to be used to package moisture sensitive products such as cigarettes. By providing collation films which are good moisture barriers, the burden of moisture resistance on the polyolefinic filmic material used to wrap the individual products is reduced meaning that the polyolefinic filmic material can be made thinner, reducing the cost of packaging and also the burden on the environment. For the avoidance of doubt, where reference is made to a 'polyester outer sealing layer', this means that the principal constituent of the layer in question is polyester.

Any sealing arrangement of the naked collation film around the individually wrapped packages may be employed. In a preferred arrangement, the naked collation film is wrapped around the ordered configuration of individually wrapped packages to form a film tube with overlapping edges. A girth seal may then be formed by sealing together the overlapping edges of the film tube, without sealing the naked collation film to the filmic polymeric material of the individually wrapped packages. Envelope seals can then be formed at each end of the package by folding in the film tube and sealing the folded ends, without sealing the naked collation film to the filmic polymeric material of the individually wrapped packages.

The girth seal is preferably formed A' to A. The envelope seals may be formed A' to A' and/or A to A' and/or A to A, and combinations of two or more thereof.

It is preferred that the outer sealing layer comprises at least 50% polyester. In more preferred embodiments of the present invention, the outer sealing layer comprises at least 80% or more preferably 95% polyester. The inner sealing layer A', may be formed of any material which exhibits sealing compatibility with the outer sealing layer A and sealing incompatibility with the filmic polyolefinic material of the individually wrapped packages.

In a preferred embodiment, the inner sealing layer A' comprises a polyester component. Preferably, the inner sealing layer comprises polyester in an amount of at least 50 percent, by weight of that layer. In preferred embodiments, the inner sealing layer comprises polyester in an amount of at least 80 percent or at least 95 percent, by weight of that layer.

In especially preferred arrangements, the material from which inner sealing layer A' is formed is the same as or is substantially the same as the material from which outer sealing layer A is formed.

The inner sealing layer A' may additionally or alternatively comprise a polyolefinic component. The polyolefinic component may comprise homopolymers or copolymers.

In such arrangements, the external surface of the filmic polyolefinic material of the individually wrapped packages preferably comprises at least one polyolefinic component derived from a monomeric olefin having a carbon chain length x, and the inner sealing layer A' comprises at least one polyolefinic component derived from a monomeric olefin having a carbon chain length y, y being different from x. 11 050700

Thus, in the case where the surface polyolefinic material of the individually wrapped packages comprises a polyethylenic component, the polyolefinic material of the inner sealing layer A' preferably comprises a polypropylenic component and/or a polybutylenic component. In the case where the surface polyolefinic material of the individually wrapped packages comprises a polypropylenic component, the inner sealing layer A' preferably comprises a polyethylenic component and/or a polybutylenic component. In the case where the surface polyolefinic material of the individually wrapped packages comprises a polybutylenic component, the inner sealing layer A' preferably comprises a polyethylenic component and/or a polypropylenic component.

For the avoidance of doubt, it is mentioned that, in arrangements where inner sealing layer A' comprises a polyolefinic component, when the external surface of the filmic polyolefinic material of the individually wrapped packages comprises at least one polyolefinic component derived from a monomeric olefin having a carbon chain length x, and the inner sealing layer A' comprises at least one polyolefinic component derived from a monomeric olefin having a carbon chain length y, y being different from x. The inner sealing layer A' may additionally comprise at least one polyolefinic component derived from a monomeric olefin having a carbon chain length x. In this case, inner sealing layer A' comprises at least two polyolefinic components, one being derived from a monomeric olefin having a carbon chain length y and the other being derived from a monomeric olefin having a carbon chain length x. The polyester material of the outer sealing layer A may also additionally comprise at least one polyolefinic component derived from a monomeric olefin having a carbon chain length x.

It is also contemplated within the scope of the invention to provide an inner sealing layer and/or a filmic polyolefinic material having a polymeric component derived from plural monomeric sources (for example a polypropylene/polyethylene random or block copolymer, and/or a blend of polypropylene and polyethylene), in which case provided that the sealing layer is derived from at least one monomeric component which has a different chain length from at least one monomeric originating component of the filmic polyolefinic material, then sealing incompatibility is realised. It will be appreciated that in this case the filmic polyolefinic material and the material of the inner sealing layer may consist of or comprise the same polyolefinic material, for example a block or random copolymer or blend derived from plural monomeric sources wherein at least one monomeric source (for example ethylene) is of different chain length from at least one other monomeric source (for example propylene).

Preferably both x and y are from 2 to 4, although x and y must be different in this embodiment of the invention.

Accordingly, the invention provides a means for forming a naked collation package in which the naked collation film is rendered incompatible (for sealing purposes at the sealing condition) with the polyolefinic (especially polypropylenic) material wrapping the individual packets. The naked collation film has sealing compatibility with itself (A to A, A to A' and/or A' to A') at the sealing condition but is sealingly incompatible (at the sealing condition) with the filmic polyolefinic material of the individually wrapped packages. One way in which such sealing incompatibility can be provided is by providing an inner sealing layer comprising a polyester component and / or at least one polyolefinic material derived from a monomer of different chain length from a monomer from which at least one polyolefinic material in the filmic material of the wrapped individual packages is derived.

The invention provides a method as hereinbefore described for forming a naked collation package in which the inner sealing layer and/or the outer sealing layer comprises at (east one component having a low heat seal threshold.

By "low heat seal threshold" is preferably meant that the sealing layer comprising the material having the low heat seal threshold wi!! seal to itself and/or to the other sealing layer of the naked collation film at a temperature of less than 135°C, preferably less than 130°C, more preferably less than 125°C, still more preferably less than 120°C, even more preferably less than 115°C and most preferably less than 110°C when subjected to a sealing condition of for example 5psi at a 0.2s dwell time. The sealing condition in forming the naked collation package of the invention may be selected to correspond the said sealing temperature, or to be greater than it, provided that the sealing condition is not selected to be so great that sealing between the inner sealing layer of the naked collation film and the polyolefinic filmic material of the wrapped individual packages will begin to occur. The heat seal strength of the outer sealing layer to itself and/or to the inner sealing layer at the selected sealing condition is preferably above 100g/25mm, more preferably above 200g/25mm, still more preferably above 300g/25mm and most preferably above 400g/25mm.

The heat seal threshold of the or each sealing layer of the naked collation film to itself and/or to the other sealing layer of the naked collation film should in any event be lower than the heat seal threshold of the said sealing layer to the polyolefinic filmic material of the unit wraps, preferably substantially lower, for example at least about 5°C lower, preferably at least about 10°C lower, more preferably at least 15°C lower. At the selected sealing condition the seal strength of the or each sealing layer of the naked collation film to itself and/or to the other sealing layer should be higher than the seal strength of the said sealing layer to the polyolefinic filmic material of the unit wraps, preferably substantially higher, for example at least about 50g/25mm higher, preferably at least about 100g/25mm higher, more preferably at least about 150g/25mm higher.

By "sealing incompatibility" or "sealingly incompatible" is preferably meant that the seal strength at the sealing condition is less than 100g/25mm, preferably less than 80g/25mm, more preferably less than 60g/25mm, still more preferably less than 40g/25mm, yet more preferably 30g/25mm, even more preferably iess than 20g/25mm and most preferably less than 10g/25mm, or even less than 5g/25mm, or close to 0g/25mm or zero.

The sealing layers of the film may optionally be corona discharge treated, or treated in some other way further to enhance the sealing incompatibility between the sealing layers and the filmic polyolefinic material.

The filmic polyolefinic material may be of any known construction, including monolayer and multilayer, but in order to ensure sealing incompatibility with the naked collation film, it is generally only necessary, or primarily necessary, to consider only the external outer layer of that material as polyolefinic. In this sense "sealing incompatibility" refers to a substantial absence of sealing at the selected sealing condition between the naked collation film and the external outer surface of the filmic polyolefinic material of the individually wrapped packages.

The invention aiso provides a naked collation package comprising an arrangement of individual packages, individually packaged in a polyolefinic filmic material, that are packed together in said naked collation package in a naked collation film, wherein the naked collation film comprises a sealable polyolefin film having a polyolefinic core layer C, a polyester outer sealing layer A, and an inner sealing layer A', the polyester material of the outer sealing layer A being selected for sealing compatibility with A and A' and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the material of the inner sealing layer A' being selected for sealing compatibility with A' and A and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the individual packages being arranged in an ordered configuration inside the package and with the naked collation film wrapped around the ordered configuration of individual packages.

The inner sealing layer is selected for sealing incompatibility with the filmic polyolefinic material of the individually wrapped packages under a specific sealing condition. Inner sealing layer A' also has sealing compatibility with outer sealing layer A under the selected sealing condition.

The collation film is preferably sealed to itself at a girth seal, and sealed to itself (A to A, A to A' and/or A' to A') at envelope seals at each end of the package, there being no seal between the naked collation film and the filmic material of the individual packages.

The sealing condition may be selected by the assembler of the naked collation package and will generally comprise conditions of elevated temperature and/or pressure and a dwell time for the sealing operation. Typically the sealing temperature will be above 80°C, for example above 85°C, or even above 90°C. Sometimes seal temperatures in excess of 95°C or even 100°C may be used. Typically it is desirable for the sealing temperature to be below a certain level also. An excessive sealing temperature may cause sealing of the naked collation film to the individual packages. Generally the sealing temperature will be below 200°C, more often lower, such as below 175°C, below 150°C or below 140°C. Usually it is preferable for the sealing temperature not to exceed 130°C. The sealing pressure will typically be above 2psi, often between about 5psi and 25psi for example. Dwell times may be selected in accordance with well known principles and will generally be from at least about 0.05s to about 2s, for example from 0.075s to about 1s, preferably from about 0.1s to about 0.5s.

The sealing layers are preferably formed as coat layers, or coatings, on opposite surfaces of the core layer C. These layers may be formed by coextrusion with the core layer, by the subsequent application of one of more coats onto the surface of the already formed core layer, by extrusion coating, or by a combination thereof. Generally it is preferred that the sealing layers be coextruded together with the core layer in manufacture of the naked collation film.

To increase the degree of adherence between the core layer and the inner or outer sealing layers, the naked collation film may comprise at least one tie constituent having compatibility with the polymeric material of the core layer and with the sealing layers, the said compatibility of the tie constituent deterring delamination of the sealing layers from the core layer. By "compatibility" is preferably meant that the tie constituent has an affinity, for example a chemical affinity, both for material of the sealing layer/s and for material of the core layer.

The tie constituent, when present, may be provided in a tie layer B of the film between the core layer and the inner and/or outer sealing layers. In arrangements where a single tie layer B is present, the collation film may have the structure A/B/C/A' or A/C/B/A'. In alternative arrangements, where two tie layers are present, the collation film may have the structure A/B/C/B/A. The requirement for one or more tie layers will depend, for example, on the materials from which the sealing layers and the core layer are formed.

Alternatively or additionally, the tie constituent may be provided in any of the core layer, the inner sealing layer and / or the outer sealing layers. Thus, in arrangements where the collation film structure is presented in the absence of tie layer B, e.g. A/C/A', a tie constituent may nevertheless be present, in the core layer or in the sealing layers. Further, in arrangements where the collation film structure is presented as including a tie layer B, this does not exclude the presence of tie constituents in the sealing, core, or other layers. For example, if the collation film structure is presented as A/B/C/A', the film clearly includes a tie layer between the outer sealing layer and the core layer. However, one or more of the outer sealing layer, the inner sealing layer and the core layer may also include a tie constituent. The tie constituent preferably comprises a modified polyolefin, for example, a copolymer of ethylene with an ester such as an ethylene/vinyl acetate copolymer, or an ethylene/methyl acrylate copolymer, an ethylene/n-butyl acrylate copolymer, or an ethylene/ethyl acrylate copolymer, for example, lonomers (partially hydrolyzed ester derivatives) are also suitable comonomers. Alternatively, the tie constituent may be a copolymer of ethylene and a carboxylic acid or carboxylic acid anhydride, or a terpolymer of ethylene, an ester, and a carboxylic acid or carboxylic acid or anhydride. Suitable carboxylic acids and carboxylic acid anhydrides include, but are not limited to acrylic acid, methacrylic acid, and maleic acid or maleic anhydride. Preferred modified polyolefins include ethylene/methyl methacrylate or ethylene/methacrylate/maleic acid anhydride copolymers. Such polymers are available under the trade names Admer, Bynel and Lotader.

The inner sealing layer A' may comprise one or more polyolefinic homopolymers, one or more polyolefinic copolymers, or mixtures of two or more thereof. By "copolymers" in this sense is meant any number of constituent polymer parts - so that bipolymers, terpolymers and copolymers of four or more constituent polymer parts are all included, for example. Both random and block copolymers are included in this definition, and the sealing layers may additionally or alternatively comprise blends of one or more homopolymers, copolymers or mixtures thereof. The polyester comprised in the outer sealing layer, and optionally in the inner sealing layer, of the films of the present invention is preferably a copolyester. Examples of copolyesters which may be employed in the films of the present invention are reaction products of terephthalic acid, isophthalic acid or adipic acid with ethylene glycol, butanediol or hexanediol.

The polyester materials which may be employed in the sealing layer/s of the present invention preferably have a low degree of crystallinity. In preferred arrangements, the polyester is amorphous.

In a preferred embodiment, the polyester is the copolyester PETG. An example of such a copolyester is Eastar 6763, available from Eastman Chemicals.

The core layer is polyolefinic and may also comprise one or more homopolymers, one or more copolymers, or mixtures of two or more thereof. Preferably however, the core layer comprises a homopolymer, more preferably polypropylene, most preferably biaxially oriented polypropylene. The material of the core layer may however be blended with one or more further materials to select if desired additional or alternative functionality or aesthetics.

It will be understood that the naked collation film may comprise additional layers as well as the hitherto identified core and sealing layers C, A and A'. Such additional layers may for example include lamination layers, printable layers, UV barrier layers, oxygen permeability or barrier layers, water vapour permeability or barrier layers and the like. Such additional layers may be provided also by coextrusion, by post-coextrusion coating, by coextrusion coating or by combinations of two or more thereof.

The naked collation film may comprise, in its core layer and/or in one or more of its sealing layers and/or in any additional layer(s) functional materials for other purposes in relation to the functional or aesthetic characteristics of the film. Suitable functional materials may be selected from one or more of the following, mixtures thereof and/or combinations thereof: UV absorbers, dyes; pigments, colorants, metallised and/or pseudo-metallised coatings; lubricants, anti-static agents (cationic, anionic and/or non-ionic, e.g. poly-(oxyethylene) sorbitan monooleate), anti-oxidants (e.g. phosphorous acid, tris (2,4-di-tert-butyl phenyl) ester), surface-active agents, stiffening aids, slip aids (for example hot slips aids or cold slip aids which improve the ability of a film to slide satisfactorily across surfaces at about room temperature, e.g. micro-crystalline wax; gloss improvers, prodegradants, barrier coatings to alter the gas and/or moisture permeability properties of the film (such as polyvinylidene halides, e.g. PVdC); anti-blocking aids (for example microcrystalline wax, e.g. with an average particle size from about 0.1 to about 0.6 μητι); tack reducing additives (e.g. fumed silica, silica, silicone gum); particulate materials (e.g. talc); additives to increase COF (e.g. silicon carbide); additives to improve ink adhesion and/or printability, additives to increase stiffness (e.g. hydrocarbon resin); additives to increase shrinkage (e.g. hard resin).

Some or all of the additives listed above may be added together as a composition to coat the films of the present invention and/or form a new layer which may itself be coated and/or may form the outer or surface layer of the sheet. Alternatively, some or all of the preceding additives may be added separately and/or incorporated directly into the bulk of the core layer optionally during film formation (e.g. as part of the original polymer composition), and thus they may or may not form layers or coatings as such.

Films of the invention can also be made by the laminating of two co-extruded films. Application of the outer layers onto the core layer is conveniently effected by any of the laminating or coating techniques conventionally employed in the production of composite multi-layer films. For the avoidance of doubt, where reference is made in this context to Outer' layers, those layers include not only the outer sealing layer A, but also the inner sealing layer A' as well as any additional layers besides the core layer C.

Preferably, one or more outer layers are applied to the substrate by a co- extrusion technique in which the polymeric components of the core and outer layers are co-extruded into intimate contact while each is still molten. Preferably the co-extrusion is effected from a multi channel annular die so designed that the molten polymeric components constituting individual layers of the composite film merge at their boundaries within the die to form a single composite structure which is then extruded from a common die orifice in the form of a tubular extrudate. It will be appreciated that any other shape of suitable die could also be used such as flat die.

The polymeric film can be made by any process known in the art, including, but not limited to, cast sheet, cast film, or blown film. This invention may be particularly applicable to films comprising cavitated or non-cavitated polypropylene films, with a block copolymer polypropylene/polyethylene core and skin layers with a thickness substantially below that of the core layer and formed for example from random co-polymers of ethylene and propylene or random terpolymers of propylene, ethylene and butylene. The film may comprise a biaxially orientated polypropylene (BOPP) film, which may be prepared as balanced films using substantially equal machine direction and transverse direction stretch ratios, or can be unbalanced, where the film is significantly more orientated in one direction (MD or TD). Sequential stretching can be used, in which heated rollers effect stretching of the film in the machine direction and a stenter oven is thereafter used to effect stretching in the transverse direction. Alternatively, simultaneous stretching, for example, using the so-called bubble process, or simultaneous draw stenter stretching may be used. In certain arrangements of the present invention, the naked collation film employed may have a degree of shrinkability. Preferably, the degree of shrinkability is relatively low, less than 20% in the machine and/or transverse directions at 135°C. In preferred arrangements, the degree of shrinkage is less than 10% in the machine and/or transverse directions at 135°C. Regardless of the degree of shrinkability of the film, an advantage of the films employed in the present invention is that the degree of shrinkability is controllable, i.e. it is consistent and predictable.

The films used in accordance with 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 240pm thick, preferably from about 12 to 50pm thick, and most preferably from about 15 to about 30pm thick.

In a multi-layer film in accordance with the invention having a core layer, an outer sealing layer and an inner sealing layer, each sealing layer may independently have a thickness of from about 0.05pm to about 2pm, preferably from about 0.075pm to about 1.5pm, more preferably from about 0.1 pm to about 1.0pm, most preferably from about 0.15pm to about 0.5pm.

It has surprisingly been found that films having sealing layers of such low thickness perform effectively; as will be demonstrated below, good sealing properties are exhibited by films of the present invention. The outer and/or inner sealing layers may be ink printable, either inherently or with the aid of a suitable treatment, corona discharge treatment for example.

Tie layer/s B, if present, may independently have a thickness of from about 0.05pm to about 2pm, preferably from about 0.075pm to about 1.5pm, more preferably from about 0.1 m to about 1.0pm, most preferably from about 0.3pm to about 0.5pm. Despite the low thickness of the tie layers B employed in the films of the present invention, they were unexpectedly found to provide good resistance to delamination of those films. By reducing the thickness of the tie layers B, the amount of tie constituent used to produce those layers is reduced. This in turn reduces the cost of production on the film and also reduces the burden on the environment.

The invention is further illustrated by reference to the following examples, which are by way of illustration only, and are not limiting to the scope of the invention described herein.

EXAMPLE 1

Preparation of Film Twelve samples having the following structures were prepared using coextrusion techniques. Samples 1 to 3 are provided for illustrative purposes and do not fall within the scope of the present invention.

Optical Properties. Gloss and wide angle haze (WAH) values of the samples were recorded using the ASTM D2457 and D1003 test methods, respectively. Gloss was measured using a Rhopoint glossmeter, using an angle of 45°. WAH was measured using an E.E.L. Spherical Haze Meter. The results are provided below:

As can be seen, the optical properties of the samples (Samples 1 to 3) which do not include the outer sealing layer are poor. The provision of a copolyester sealing layer and tie coat provides a vast improvement in optical properties (Samples 4 to 6). An increase in the weight of the external sealing layer improves optical properties further (Samples 7 to 9). Excellent optical properties are also provided by films which do not include a separate tie layer (Samples 10 to 12).

Surface Energy. The surface energy of the nine inventive samples has been measured by wiping a swab, saturated with a Sherman ink of known surface tension, across the surface of the films and observing whether the liquid wets the surface or retracts into droplets. The surface energy of the ink with the highest surface tension that wets the film surface is taken as the surface energy of the film.

The surface energy of each of those samples falls within the range of 42 to 44 Dynes/cm. Surface energies of this order of magnitude are advantageous as they increase the incompatibility of the copolyester sealing layer with the polyolefinic filmic material in which the individual items are wrapped. A high surface energy also improves printability of the films. Printability. Ink adhesion has been recorded at room temperature using a range of ink types. The tests were performed by taking samples of the films, applying ink, and drying in an oven at 60° for 2 minutes. A strip of tape is then rolled over the printed surface with a rubber roller to ensure even contact with the printed surface. The tape is then removed and the percentage of ink that is removed with the tape is recorded.

Results indicate that the non-inventive samples (Samples 1 to 3) were not printable. Samples 4 to 9, however, all showed 100% adhesion with solvent based inks at room temperature, indicating that these samples are inherently printable with solvent based inks.

Heat Sealing Strength. The heat sealing strength of Samples 4 to 12 was investigated. Samples of the inventive films were taken in pairs and the PETG outer sealing layers of those pairs were sealed to each other at a pressure 5psi and at temperatures of from 115°C to 150°C for 0.5 second dwell time, i.e. an A to A seal (or an A to A' seal, if the inner and outer sealing layers are formed of the same material) was made. The seal strength was then measured. Sample 115°C 120°C 125°C 130°C 135°C 140°C 150°C

4. 0 27 40 100 127 117 105

5. 0 30 73 180 205 209 207

6. 0 25 155 224 285 264 224

7. 0 16 42 172 194 215 242

8. 0 32 63 266 325 329 300

9. 0 36 201 331 387 388 362

10. 0 0 95 234 315 289 265

11. 0 62 95 137 100 138 102

12. 0 52 67 72 65 102 67

From these results, it can be seen that all inventive samples exhibited good seal strengths, confirming that the films of the present invention are compatible with themselves. It can also be seen that an increase in the weight of the tie layer leads to improved heat seal strength of the co-polyester across the temperature range. Increasing the coat weight of co-polyester, where used in conjunction with a tie layer, leads to a further improvement in heat seal strength, of the co- polyester across the temperature range. Increasing co-polyester coat weight in the absence of a tie layer also results in improved seal strength.

Incompatibility. To investigate the degree of incompatibility between the samples of the present invention and the tobacco unit wraps, heat seal tests between the two materials were carried out. The same technique as outlined above in the Heat Sealing Strength tests was adopted, except that instead of sealing the PETG outer sealing layers of two samples together, the outer sealing layer of a sample was heat sealed to a sample of conventionally used filmic polyolefinic wraps and the resulting seal strengths measured.

10 GLT (EOD) 6.1 5.6 13.1 14 10.6 21.1 39.5

GLT (SPX) 10.3 9.8 18.6 15 9.4 57.5 0

GLT (Hyosung) 10.3 2.4 23.5 17.4 22.4 27.2 79.3

GLS (Stamylx) 14.4 8.5 12.1 20.5 17.1 0 0

30 135 140 145 150 160 170

11 GLT (EOD) 17.4 8.1 6.4 8.9 13.8 39.2 85.2

GLT (SPX) 6.7 7.4 3.8 17.3 25.1 24 0

GLT (Hyosung) 6.2 4.8 8 16.1 29.5 31.3 32.6

GLS (Stamylx) 10 12.9 19.5 16.7 0 0 0

130 135 140 145 150 160 170

12 GLT (EOD) 6.7 7.4 19 15.9 20.7 19.5 28.7

GLT (SPX) 6.6 10.4 5.7 11.1 12.1 25.2 26.9

GLT (Hyosung) 4.6 7.4 12.7 11.8 15.4 30.2 28.7

GLS (Stamylx) 8.6 18 10.7 14.3 26.4 0 0

As can be seen, the seals formed between comparative Samples 1 to 3 were high, meaning that those films were compatible with the polyolefinic filmic wraps. However, the seal strength between the films of Samples 4 to 12 was far lower, across a wide temperature range, confirming their incompatibility with polyolefinic filmic wraps.

Claims

1. A method for forming a naked collation package comprising:

a) providing an arrangement of packages individually wrapped in a filmic polyolefinic material;

b) providing a naked collation film for nakedly wrapping said individually wrapped packages, the naked collation film comprising a polyolefinic core layer C, a polyester outer sealing layer A on the outer surface of the naked collation film, and an inner sealing surface layer A' on the inner surface of the naked collation film, the polyester material of the outer sealing layer A being selected for sealing compatibility with A and A' and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the material of the inner sealing layer being selected for sealing compatibility with A' and A and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition; c) arranging the individually wrapped packages in an ordered configuration in contact with the naked collation film;

d) wrapping the naked collation film around the ordered configuration of individually wrapped packages; and

e) sealing the naked collation film.

2. The method of Claim 1 , wherein the naked collation film, in step d), is wrapped around the ordered configuration of individuaiiy wrapped packages to form a film tube with overlapping edges, and, in step e), a girth seal is formed by sealing together the overlapping edges of the film tube, without sealing the naked collation film to the filmic polymeric material of the individually wrapped packages and envelope seals are formed at each end of the package by folding in the film tube and sealing the folded ends, without sealing the naked collation film to the filmic polymeric material of the individually wrapped packages.

3. The method of Claim 2, wherein the girth seal is formed A to A'

4. The method of Claim 2 or 3, wherein the envelope seals are formed A to A, A to A' and/or A' to A'.

5. The method of any one of Claims 2 to 4, wherein the inner sealing layer comprises a polyester component.

6. The method of any one of Claims 2 to 5, wherein the outer sealing layer and inner sealing layers are formed of substantially the same material.

7. The method of any one of Claims 2 to 6, wherein the inner sealing layer comprises at least one polyolefinic component having a low heat seal threshold.

8. The method of any one of Claims 1 to 7, wherein the outer sealing layer comprises at least 50% by weight of the layer copolyester.

9. The method of Claim 8, wherein the copolyester is amorphous.

10. The method of Claim 8 or 9, wherein the copolyester is PETG.

11. The method of any one of Claims 1 to 10, wherein the naked collation film comprises a tie constituent.

12. The method of Claim 1 , wherein the tie constituent is located in the outer sealing layer, the inner sealing layer, the polyolefinic core, or in at least one tie layer located therebetween.

13. The method of Claim 11 or 12 wherein the tie constituent is a modified polyolefin.

14. The method of Claim 13, wherein the modified polyolefin is ethylene modified with acrylate or anhydride groups.

15. The method of any one of Claims 12 to 14, wherein the at least one tie layer has a thickness of from about 0.05pm to about 2pm.

16. The method of any one of Claims 12 to 15, wherein the at least one tie layer has a thickness of from about 0.1 pm to about 1.0μιη,

17. The method of any one of Claims 12 to 16, wherein the at least one tie layer has a thickness of from about 0.3μιη to about 0.5pm.

18. The method of any one of Claims 1 to 17, wherein the inner and / or outer sealing layers have a thickness of from about 0.05μιη to about 2μηΊ.

19. The method of any one of Claims 1 to 18, wherein the inner and / or outer sealing layers have a thickness of from about 0.1 μπι to about 1.Opm.

20. The method of any one of Claims 1 to 19, wherein the inner and / or outer sealing layers have a thickness of from about 0.15pm to about 0.5pm.

21. The method of any one of Claims 1 to 20, wherein the sealing condition comprises conditions of elevated temperature and/or pressure and a dwell time for the sealing operation.

22. The method of Claim 21 , wherein the sealing temperature is above 80°C.

23. The method of Claim 21 or 22 wherein the sealing temperature is below 200°C.

24. The method of any one of Claims 21 to 23, wherein the dwell time is from 0.05s to 2s.

25. A naked collation package manufactured by a method according to any one of Claims 1 to 24.

26. A naked collation package comprising an arrangement of individual packages, individually packaged in a polyolefinic filmic material, that are packed together in said naked collation package in a naked collation film, wherein the naked collation film comprises a sealable polyolefin film having a polyolefinic core layer C, a polyester outer sealing layer A, and an inner sealing layer A', the polyester material of the outer sealing layer A being selected for sealing compatibility with A and A' and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the material of the inner sealing layer A' being selected for sealing compatibility with A' and A and sealing incompatibility with the filmic polyolefinic material under the selected sealing condition, the individual packages being arranged in an ordered configuration inside the package and with the naked collation film wrapped around the ordered configuration of individual packages.