Naked collation packaging film

Abstract

The naked collation film comprises a core layer (C), an inner sealing layer (I) of a polyolefin material, and an outer sealing layer (O) of a polyolefin material, each sealing layer comprising at least two, preferably three, polyolefins selected from C4 and at least one of C2 and C3 polyolefins. At least one of the inner and outer layers has at least one of i. a C4 content greater than about 10 mol%, ii. a C4 / C2 molar ratio of at least about 1.2, and / or iii. a C4 / C3 molar ratio of at least about 0.15. The collation film is preferably non-blocking, has a large incompatibility window with the individually wrapped packages (P) of the naked collation package, and has strong optical performance.

Description

[Technical field]

[0001] The present invention relates to naked collation films, naked collation packages, and methods of forming naked collation packages including the naked collation films. [Background technology]

[0002] Naked collation is an effective way to reduce packaging costs and materials. When several individually packaged items, such as cigarette packs, are grouped together and packaged as a larger bundle for distribution or bulk retail, the individual packages are typically placed into a larger box or carton before being subsequently wrapped. Naked collation eliminates the need for the box or carton, thereby reducing packaging materials.

[0003] An essential feature of a naked collation film is that it must be capable of sealing to itself, rather than (under selected sealing conditions) to the films used to encase the individual packets. It is therefore clear that a naked collation film must have inner and outer surfaces which are sealable (under selected sealing conditions) to each other, and not to the individual packet films (also known as unit wrap films).

[0004] Another essential feature of a naked collation film is that it must be non-blocking, i.e., it must not tend to stick to itself, even under the rather severe conditions of temperature and pressure that may prevail, for example, in a shipping container or warehouse where multiple packages are likely to be stacked on top of each other, or in a compilation immediately after manufacture where the packs may still be somewhat warm after manufacture. "Pack-to-pack blocking" under such circumstances is highly undesirable.

[0005] WO 2009024810 discloses a naked collation package comprising an arrangement of individual packages individually packaged within a polyolefin film material packaged together within said naked collation package within a naked collation film, the naked collation film comprising a sealable polyolefin film having a polyolefin core layer C, a polyolefin inner sealing layer A and a polyolefin outer sealing layer B, the polyolefin material of the inner sealing layer A being adapted to withstand sealing incompatibility with the filmic polyolefin material of the individual packages under certain sealing conditions. and a polyolefin material of the outer sealing layer B is selected for sealing compatibility with B and sealing compatibility with A under selected sealing conditions, the individual packages are arranged in a custom configuration inside the package, and the naked collation film is wrapped around the custom configuration of the individual packages and sealed to itself with a perimeter seal (A to B) and sealed to itself with an envelope seal at each end of the packages (B to B, and optionally A to B), and there is no seal between the naked collation film and the film material of the individual packages.

[0006] WO2012164308 describes a method for forming a naked collation package, comprising: a) providing an arrangement of individually wrapped packages in a film-like material; and b) providing a naked collation film for naked wrapping the individually wrapped packages, the naked collation film comprising a polyolefin core layer C, an inner sealing layer A on an inner surface of the naked collation film, and a polyolefin outer sealing layer B on an outer surface of the naked collation film, the material of the inner sealing layer A being selected for sealing incompatibility with the film-like material of the individually wrapped packages under specified sealing conditions and heat shrink conditions, the polyolefin material of the outer sealing layer B being selected for sealing compatibility with B and sealing compatibility with A under specified sealing conditions, and layers A and B being different. a) providing a naked collation film for nakedly wrapping said individually wrapped packages, said naked collation film being formed from a material comprising: layer A comprising at least one polyolefin polymer and an antiblock component comprising at least 0.2% by weight of a layer of silicone; c) arranging the individually wrapped packages in an ordered configuration; d) arranging the naked collation film such that the naked collation film at least partially surrounds, but is not necessarily in contact with, the ordered configuration of the individually wrapped packages; and e) heat shrinking the naked collation film by subjecting the naked collation film to heat shrink conditions to shrink the naked collation film and intimately surround the arrangement of packages without sealing to the packages.

[0007] WO2018096480 describes a biaxially oriented multilayer film that is particularly suitable for use as an outer coating for individually packaged articles (naked collation packaging), which comprises at least one outer layer (A) comprising at least one ethylene polymer having a melting point below 100°C, one central layer (B) comprising at least one propylene polymer having a melting point above 140°C, and one inner layer (C) comprising at least one ethylene polymer having a melting point between 105°C and 115°C and a density between 0.910 and 0.940 g / cm3.

[0008] No. 6,358,579 discloses an individual sealable layer of a packaging film consisting of an ethylene homopolymer, a copolymer with ethylene in which propylene is the main component, preferably a copolymer with 1-butene and propylene as the main component in an amount of not more than 10% by weight (based on the copolymer), a terpolymer made of propylene, ethylene and an alpha-olefin having 4 to 10 carbon atoms, preferably in an amount of 10 to 15% by weight (based on the copolymer), preferably 93.2 to 99.0% by weight of propylene, 0.5 to 1.9% by weight of ethylene and 0.5 to 4.9% by weight of an alpha-olefin having 4 to 10 carbon atoms, or a mixture of these polymers.

[0009] US Pat. No. 6,777,067 discloses polypropylene films comprising at least one heat-sealable layer, and includes an extensive list of suitable heat-sealable olefin polymers, including copolymers and terpolymers.

[0010] US Patent No. 5,900,294 discloses a polyolefin multilayer film comprising a base layer containing polypropylene and at least one outer layer. The outer layer comprises a C3 / C4-olefin resin composition having a low crystallinity and has a minimum heat sealing temperature of less than 84°C. A method for producing the multilayer film and its uses are also said to be described.

[0011] European Patent No. 0645417 discloses that the n-heptane insoluble content is <13> A biaxially oriented polypropylene film having a chain isotacticity index of at least 95% as measured by C-NMR spectroscopy is disclosed. The base layer contains 1-15 wt.% of a natural or synthetic resin having a softening point of 70-170° C. The disclosure is also said to relate to a method for producing the polypropylene film and uses thereof.

[0012] German Patent No. 3635928 discloses a multipack system comprising an arrangement of individual packages, each of which is made in a biaxially oriented polypropylene film with a modified polyolefin heat-sealing layer. The feature that characterizes the multipack system is said to be that the outer wrap film comprises a heat-sealable biaxially oriented multilayer polypropylene film produced by coextrusion with a symmetrical structure that comprises an outer layer of a low molecular weight hydrocarbon resin and is corona-treated. The multipack system according to the disclosure is said to be distinguished by the fact that the outer wrapping film is heat-sealable to itself, but does not heat-seal the biaxially oriented polypropylene film of the individual packs.

[0013] U.S. Pat. No. 5,302,427 discloses a printable biaxially oriented polyolefin multilayer packaging film, double-sided low-temperature sealed, comprising a base layer and at least one sealing layer on each side of the base layer, the base layer containing a peroxide-decomposed propylene homopolymer, each sealing layer containing an ethylene / propylene / butylene terpolymer and a propylene / butylene copolymer, one outer sealing layer containing a polydiorganosiloxane and silicon dioxide particles, not corona treated, and the polydiorganosiloxane is added in the form of a masterbatch during film manufacture.

[0014] US Patent No. 5,436,041 discloses a transparent, printable, biaxially oriented polyolefin multilayer packaging film that can be sealed on both sides, having a base layer B and different top layers A and C arranged on both sides thereof according to a build-up of layers ABC. The base layer B contains a peroxidatively decomposable polypropylene polymer with a decomposition factor ranging from about 3 to about 10. The top layer A comprises a polymer mixture of two or more of the following copolymers and / or terpolymers: copolymers of ethylene and propylene or ethylene and butylene or propylene and butylene or ethylene and another α-olefin having 5 to 10 carbon atoms, or copolymers of propylene and another α-olefin having 5 to 10 carbon atoms, or terpolymers of ethylene and propylene and butylene or ethylene and propylene and another α-olefin having 5 to 10 carbon atoms. This polymer mixture of the top layer A further contains a high viscosity polydiorganosiloxane and silicon dioxide, and optionally other added additives. The top layer C comprises a copolymer of ethylene and propylene or ethylene and butylene or propylene and butylene or ethylene and another α-olefin having 5 to 10 carbon atoms or propylene and another α-olefin having 5 to 10 carbon atoms, or a terpolymer of ethylene and propylene and butylene or ethylene and propylene and another α-olefin having 5 to 10 carbon atoms, and optionally other additives. The top layer C has a non-agglomerating coating of polydialkylsiloxane on its outer surface.

[0015] US Patent Application Publication No. 2013011669 discloses a heat-sealable oriented multilayer film comprising i) a polyolefin core layer and (ii) a blend of 10.0 wt% to 50.0 wt% of a propylene-based elastomer and 50.0 wt% to 90.0 wt% of a propylene-based polymer, the heat-sealable layer comprising less than 1.0 wt% of an ethylene homopolymer or ethylene-based copolymer, the heat-sealable layer having a haze of 5.0 or less and a seal strength of 2.00×102 g / 2.54 cm or greater at 82° C. (180° F.). In certain films, the heat-sealable layer has a haze of 5.0 or less and a seal strength of 3.00×102 g / 2.54 cm or greater at 90° C. (194° F.). Methods of making such multilayer structures and articles made therefrom are also said to be disclosed.

[0016] EP 3034300 discloses a multilayer film for naked collation of packaging products to form a pack of six or more filling pieces, comprising at least a core layer, an inner layer and an outer layer of one or more olefin (co)polymers, the outer layer (co)polymer having a melting temperature in the range of 65°C to 85°C, the inner layer (co)polymer having a melting temperature in the range of 65°C to 105°C, the core layer propylene and / or butene (co)polymer having a melting temperature above 140°C, the film enveloping the single packaging unit being formed of one or more olefin (co)polymers having a melting temperature higher than 120°C, the inner layer of the multilayer film being in contact with the film enveloping the single packaging unit (film O) forming the package, the outer layer of the multilayer film having a thickness comprised between 0.35 and less than 0.5 μm. Summary of the Invention

[0017] It is an object of the present invention to provide a naked collation film with improved performance, for example, in terms of providing a high incompatibility window, good sealing conditions at low sealing temperatures, and strong optical performance while avoiding interpack blocking problems.

[0018] Surprisingly, it has been found that the sealing properties of the sealing layer of a naked collation film can be improved by increasing the C4 polyolefin content therein.

[0019] Thus, in one aspect, the present invention provides a naked collation film comprising a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposite surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, both the inner and outer sealing layers comprising a C4 polyolefin and at least one of a C2 and a C3 polyolefin, preferably comprising C2, C3 and C4 polyolefins, and at least one of the sealing layers having a C4 polyolefin content greater than 10 mol%, preferably greater than 10.5 mol%, more preferably greater than 11.0 mol%, even more preferably greater than 11.5 mol%, and most preferably greater than 12.0 mol% based on the total polyolefin content of that sealing layer.

[0020] In a related aspect, the invention provides a naked collation film comprising a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposing surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, both the inner and outer sealing layers comprising C2 and C4 polyolefins, and optionally also C3 polyolefins, preferably comprising C2, C3 and C4 polyolefins, and at least one of the sealing layers having a C4:C2 molar ratio of at least 1.2, preferably at least 1.5, more preferably at least 1.6, and most preferably at least 1.7.

[0021] In a related aspect, the invention provides a naked collation film comprising a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposing surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, both the inner and outer sealing layers comprising C3 and C4 polyolefins, and optionally also C2 polyolefins, preferably C2, C3 and C4 polyolefins, and at least one of the sealing layers having a C4:C3 molar ratio of at least 0.15, preferably at least 0.16, more preferably at least 0.17, and most preferably at least 0.20.

[0022] The naked collation films of the above embodiments are non-blocking. By "non-blocking" we mean that the film passes the inter-pack blocking test detailed herein.

[0023] The present invention also provides a naked collation package comprising a plurality of individually wrapped packages packaged within a sealed naked collation film as defined above.

[0024] Preferably, each individually wrapped package includes a separate polyolefin film in contact with the inner sealing layer.

[0025] The further polyolefin film may or may not include C4, typically including at least two of C2, C3 and C4, or at least one of C2, C3 and C4 in combination with other polymers or copolymers or blends thereof, such as copolymers including C6 and / or C8. The further polyolefin film may be a multi-layer film, in which case the outer layer (which in the present use generally contacts the inner sealing layer of the naked collation film) may or may not include C4, typically including at least two of C2, C3 and C4.

[0026] The terms "inside", "inner", "outer" and "outside" should be construed to mean the inner or outer surface of a naked collation film, naked collation film, unit wrap film and / or film in use. The use of such terms to designate the surfaces of layers should not be construed as limiting, and it will be understood by those of skill in the art that "inside" and "inner" or "outer" and "outer" are interchangeable. For example, those of skill in the art will understand that "inside / inner" is construed the same as "inside / inner".

[0027] The present invention also provides a method for forming a naked collation package, comprising the steps of: a) providing an arrangement of individually wrapped packages; b) providing a naked collation film as defined above; c) arranging the individually wrapped packages into the ordered configuration; d) positioning the naked collation film such that the naked collation film at least partially surrounds, but does not necessarily contact, the ordered configuration of the individually wrapped packages; e) sealing the naked collation film by exposing the naked collation film to sealing conditions, causing the naked collation film to seal to itself and intimately surround the packaging arrangement without being sealed to the packaging.

[0028] In some cases, there may be additional steps including heat shrinking the naked collation film by exposing the naked collation film to heat shrink conditions, causing the naked collation film to shrink and closely surround the packaging arrangement without sealing to the packaging.

[0029] The above method preferably further comprises one or more of the following steps, which may be carried out before or after any of steps a) to d), where appropriate: a-1) forming a film tube having overlapping edges; a-2) forming a perimeter seal by sealing together the overlapping edges of the film tube; a-3) forming an envelope seal at each end of the package by folding within the film tube and sealing the folded ends.

[0030] Further details of such a method, depending on the different naked collation films, are disclosed in WO 2012 / 164308 in the name of the Applicant.

[0031] Further preferred features are defined in the dependent claims.

[0032] The present inventors have surprisingly found that naked collation films having the monomer ratio content provided herein are advantageous for a number of reasons. For example, the naked collation film wrap according to the present invention exhibits an increased performance incompatibility window (i.e., an increased range of sealing temperatures for the naked collation film below the temperature at which (undesirable) sealing occurs between the naked collation film and the film of the individually wrapped package within the naked collation film). The naked collation film of the present invention advantageously exhibits low seal initiation temperatures and strong optical properties.

[0033] It is possible to produce a film that has a relatively large incompatibility window, but is still unsuitable for use in naked collation packaging due to its tendency to block. For example, a film produced containing a single low melting C3 / C4 copolymer in its sealing layer (Comparative Example C1 described below) appears completely unsuitable for its intended use due to its tendency to block.

[0034] To avoid blocking and thus make the film "non-blocking", it is preferred that at least the outer sealing layer of the naked collation film comprises at least one copolymer or terpolymer having a melting point above 75°C, preferably above 80°C.

[0035] The term "multilayer film" should be interpreted according to the normal usage of the term to refer to a film that includes at least two layers. A multilayer film may, for example, include at least two layers, at least three layers, at least four layers, or more.

[0036] Thus, in some embodiments, the film may include an inner layer, an outer layer, and at least one core layer.

[0037] For the avoidance of doubt, any properties etc. described according to the "multilayer film" of the present invention may be construed to refer to properties of the multilayer film itself (i.e., including all layers present in the multilayer film) and / or to refer to one or more individual layers of that multilayer film, such disclosure would be clear to one of ordinary skill in the art.

[0038] Unless the context dictates otherwise, a monomer ratio of a polymer film, e.g., a C4 / C3 monomer ratio, should be interpreted as the average monomer molar ratio of the polymers in the particular layer of the multilayer film to which the context refers. Thus, monomer content is typically referred to in relation to the monomer ratio of one or more of the individual layers of the multilayer film.

[0039] The multilayer polymer film may optionally comprise a blend of polyolefin copolymers. Each polyolefin copolymer may optionally comprise at least one copolymer of propylene with ethylene or butylene. The polyolefin copolymer may optionally comprise at least one terpolymer, which may optionally be of ethylene, propylene and butene.

[0040] "Copolymer" in this sense means any number of constituent polymer moieties, such as ethylene, propylene, butene, or any olefin having up to 10 carbon atoms. Bipolymers, terpolymers and copolymers of four or more constituent polymer moieties, for example, are classified under the term "copolymer." Furthermore, both random and block copolymers are included in this definition, and the multilayer polymer film and / or individual layers of the film may additionally or alternatively comprise blends of one or more homopolymers, copolymers or mixtures thereof. The inner and / or outer layers of a multilayer film may be the same or different.

[0041] When the multilayer polymer film comprises at least one terpolymer of ethylene, propylene and butene, propylene is preferably present as the major component.

[0042] The composition of the inner and outer sealing layers of the naked collation film may be the same or different.

[0043] The inner layer and / or the outer sealing layer of the film may optionally comprise a C2 olefin polymer in an amount of from about 0 to about 20 mol %, such as from about 1 to about 15 mol %, or from about 2 to about 12 mol %.

[0044] The inner layer and / or the outer sealing layer of the film may optionally comprise a C3 olefin polymer in an amount of about 55 mol% to about 95 mol%, about 60 mol% to about 90 mol%, about 65 mol% to about 85 mol%, or about 70 mol% to about 85 mol%.

[0045] The inner sealing layer and / or the outer sealing layer of the film may comprise a C4 olefin polymer in an amount of about 10 mol% to about 40 mol%, such as about 10 mol% to about 35 mol%, for example about 10 mol% to about 30 mol%, for example about 10 mol% to about 25 mol%, for example about 10 mol% to about 20 mol%.

[0046] One or both of the inner and outer sealing layers may comprise C2, C3 and C4 polyolefins.

[0047] One or both of the inner and outer sealing layers may comprise at least two copolymers and / or one terpolymer.

[0048] The inner layer and / or the outer layer of the multilayer polymer film should be interpreted as a sealing layer. A naked collation multilayer film, for example, can have a sealing compatibility with itself (A and B, A and A and / or B and B) under sealing conditions, but has a sealing incompatibility (under sealing conditions) with the film-like polyolefin material of the individually wrapped package. One way that such sealing incompatibility can be provided is to provide the film described herein.

[0049] The term "sealing compatibility" or "compatibility" should be interpreted to mean that the seal strength under the sealing condition is at least 200g / 25mm. Thus, sealing compatibility refers to a substantial functional seal under the selected sealing condition between each sealing layer (whether inner or outer) of the multilayer polymer film.

[0050] The term "sealing incompatibility" or "incompatibility" should be interpreted to mean that the seal strength under the sealing condition is less than 50g / 25mm. Thus, sealing incompatibility refers to the substantial absence of sealing under the selected sealing condition between the inner sealing layer and the outer exterior surface of the film-like polyolefin material of the individually wrapped package.

[0051] The naked collation film may be construed as exhibiting adhesion between the inner layer of the naked collation film and the outer layer of the naked collation film and / or unit wrap when the film is heated to a temperature above the sealing initiation temperature. The term "adhesion" should be construed to mean a seal strength at sealing conditions greater than 50g / 25mm, but substantially less than 200g / 25mm, which is undesirable.

[0052] The films used in the methods of the present invention are preferably non-blocking and therefore exhibit good (ie, low) thermal blocking properties.

[0053] Without wishing to be bound by theory, the inventors of the present invention have advantageously found that a sealing layer comprising C4 and at least one of C2 and C3 achieves good heat blocking properties in a film according to the present invention.

[0054] It will be understood that naked collation films according to the present invention may optionally include additional layers, as well as the inner and outer layers previously identified. Such additional layers may include, for example, laminations, printable layers, UV barrier layers, oxygen permeable or barrier layers, water vapor permeable or barrier layers, etc. If present, such additional layers may be provided, for example, by coextrusion, post-coextrusion coating, coextrusion coating, or a combination of two or more thereof.

[0055] The polymeric film may be made by any process in the art including, but not limited to, cast sheet, cast film, or blown film.

[0056] The naked collation films of the present invention can be of various thicknesses depending on the requirements of the application. For example, they can be about 10 to about 240 μm thick, preferably about 12 to 50 μm thick, and most preferably about 15 to about 30 μm thick.

[0057] Each sealing layer may, for example, independently have a thickness of about 0.05 μm to about 2 μm, preferably about 0.075 μm to about 1.5 μm, more preferably about 0.1 μm to about 1.0 μm, and most preferably about 0.15 μm to about 0.5 μm.

[0058] The naked collation film may optionally include functional materials, for example in at least one layer, for other purposes related, for example, to the functional or aesthetic properties of the film.

[0059] Suitable functional materials may be selected from, but are not limited to, one or more of the following mixtures: UV absorbers, dyes, and / or combinations thereof; pigments, colorants, metallized and / or pseudo-metallized coatings; lubricants, antistatic agents (cationic, anionic and / or nonionic, e.g., poly-(oxyethylene)sorbitan monooleate), antioxidants (e.g., phosphoric acid, tris(2,4-di-tert-butylphenyl) esters), surfactants, curing aids, slip aids (e.g., hot or cold slip aids that improve the ability of the film to slide well across a surface at about room temperature, e.g., microcrystalline waxes); gloss enhancers, degradation promoters, barrier coatings (e.g., polyvinylidene, ethylenediaminetetraacetate ... halides, e.g., PVdC); anti-blocking aids (e.g., microcrystalline waxes having an average particle size of, e.g., about 0.1 to about 0.6 μm); tack reducing additives (e.g., fumed silica, silica, silicone gums); 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 and / or increase shrinkage (e.g., hydrocarbon resins and / or hydrogenated hydrocarbon resins). As specific and non-limiting examples, hydrocarbon resins and / or hydrogenated hydrocarbon resins that may be used to increase stiffness and / or increase shrinkage may include one or more C5 resins and / or C9 resins. For example, suitable C5 resins and / or C9 resins may include Constab™ MA 00956 PP, Oppera™ PR 120, Regalite™ R 1125, Arkon™ P-125, and / or mixtures of two or more thereof.

[0060] The naked collation film according to the present invention may be used as an overpacking or wrap around an article that is individually wrapped with a film-like material, such as a cigarette packet configuration. The film-like material may be, for example, a polyolefin material.

[0061] In this context, the film-like material may be construed as a "unit wrap."

[0062] A unit wrap can include, for example, at least one layer, at least two layers, or at least three layers. Thus, a unit wrap can have at least an inner surface and an outer surface.

[0063] The outer surface of the film-like material of the unit wrap preferably comprises at least one polyolefin component. Typically, these may comprise one or more of C2, C3 and / or C4, and sometimes C8 olefinic polymers. In a preferred embodiment, C3 olefinic polymer is the predominant material.

[0064] The present inventors have surprisingly found that such an arrangement provides the large incompatibility window described herein.

[0065] The C4 mol % content of the naked collation film is preferably higher than that of the film-like material of the unit wrap.

[0066] The C4 mol % content of the inner layer of the naked collation film is preferably higher than that of the outer layer of the film material of the unit wrap.

[0067] The film material encasing the individual packets, for example a polyolefin material, suitably comprises a polypropylene-based (C3) olefin polymer and may further comprise a C2 and / or C4 olefin polymer.

[0068] For the avoidance of doubt, all features relating to naked collation films also relate to uses of naked collation films and methods for forming naked collation packages, where appropriate, and vice versa.

[0069] Preferred embodiments of the present invention will now be described, by way of example only, with reference to Figures 1 to 4 of the accompanying drawings. [Brief description of the drawings]

[0070] [Figure 1] FIG. 1 is a schematic cross-sectional view of a naked collation film according to the present invention in contact with a package to form a naked collation package. [Diagram 2] FIG. 2 is a plot of the incompatibility window of C4 mol % content for example naked collation films of the present invention. [Diagram 3] FIG. 3 is a plot of incompatibility window: C4:C3 molar ratio for an example naked collation film of the present invention. [Figure 4] FIG. 4 is a plot of incompatibility window: C4:C2 molar ratio for an example naked collation film of the present invention.

[0071] example Preparation of films Thirteen random copolymers were prepared and named with polymer references A to M. These copolymers may be obtained by polymerizing the monomers by known polymerization methods such as gas phase, bulk and slurry processes in the presence of catalysts such as Ziegler-Natta and metallocene catalysts. Further details of such processes can be found in EP 0483675, US 2017037161 and WO 18211107.

[0072] Sixteen samples of biaxially oriented film were prepared using a standard bubble process in which polymer layers are extruded from a core extruder and a sealing layer extruder to create a three-layer polymer tube. The polymer tube passes through a cooling system, is subsequently reheated, and bubbles are formed by flowing air inside the polymer tube. The bubbles are then cooled before being collapsed by converging rollers, slit to form two polymer film sheets, processed on rollers, and surface-treated by corona treatment before being collected in a roll. Further details of the bubble process are described, for example, in EP 0410792 and GB 2000175.6 and Biaxial Stretching of Film, Principles and Applications, 2011, Ed. Mark T. DeMeuse, ISBN 978-1-84569-675-7.

[0073] Prior to extrusion, a standard antiblock / slip wrapper was added to the polymer mixture of the sealing layer(s) to aid in downstream processing. The antiblock / slip wrapper added to the outer layer contained 1.2% PDMS (silicone gum) and 0.1% Silica AB. The antiblock / slip wrapper added to the inner layer contained 0.5% PDMS (silica gum) and 0.1% Silica AB.

[0074] All of the film samples according to the invention tested below contained the same antiblock / slip packaging as described above.

[0075] In all cases the core layer of the film was composed of polypropylene homopolymer.

[0076] Details of the 16 film samples and their sealing layer polymer content (inside and outside ("inside" refers to the side of the film that forms the inside surface of the naked collation film within the naked collation package when in use, and "outside" refers to the outside surface of the film when in use) are shown in Tables 1 and 2 below.

[0077] Sample 3 has a maximum of 8.4 mol % C4 in its sealing layer, a maximum C4 / C2 molar ratio of 0.84, and a maximum C4 / C3 molar ratio of 0.1, and is therefore a comparative example.

[0078] Melting temperature (T m / ℃) In the following examples of polymers, the melting points (T m The method used to determine the T of the polymers in Table 1 is similar to that used according to ASTM D3418. m Because the method used to determine this uses a faster heating rate than ASTM D3418, the observed melting points are approximately 2% higher than would be found if measured by ASTM D3418.

[0079] The melting temperatures of the polymer samples were determined by the following method: A differential scanning calorimeter (Perkin Elmer Diamond™ DSC) capable of heating or cooling at rates greater than 20° C. / min was used.

[0080] First, the DSC was calibrated at the same heating rate (20°C / min) as that used for the samples. A known weight of indium (approximately 10 mg) was pressed into an aluminum pan and heated at 20°C / min from 0°C to 170°C using an uncalibrated temperature scale. The temperature scale of the instrument was verified against the observed melting points of standards. The melting points observed for these materials should be considered the onset of melting.

[0081] The polymer granules were cut to obtain a mass of approximately 8.5 mg, a size that would fit appropriately into an aluminum sample pan. The side of the sample facing the base of the pan should be flat and smooth.

[0082] The film is die cut to a size approximately equal to the dimensions of the sample pan, for example, a paper hole punch may be used to create the required size, and may be firmly crimped to ensure good contact with the base of the sample pan, which should not be damaged or deformed to ensure good contact with the heat source.

[0083] Approximately 8.5 mg of sample was weighed to an accuracy of 0.01 mg and tightly crimped into an aluminum sample pan. If it was thought that the sample might release decomposition gases resulting in a pressure increase, the pan was punctured in the center of the lid.

[0084] The sample was placed in the center of the cell and a nitrogen purge was maintained at 30 ml / min throughout the test to provide an inert atmosphere.

[0085] An initial heating step was performed from 0° C. to 210° C. at 20° C. / min. The sample was held at 210° C. for 3 minutes to ensure complete melting and eliminate thermal history. The sample was then cooled to 0° C. at 20° C. / min and the resulting cooling curve was recorded. This curve can be used to determine any crystallization transitions.

[0086] The sample was immediately reheated to 210°C at 20°C / min and the resulting heating curve was recorded. This curve was used to determine any melting transitions. The observed melting point was taken as the onset of melting.

[0087] Weight average molecular weight (M w / g / mol), number average molecular weight (M n / g / mol), intrinsic viscosity (IV / dL / g), radius of hydration (Rh / nm), and radius of gyration (Rg / nm) Thirteen samples of the polymer pellets were analyzed by high temperature gel permeation chromatography (HT-GPC) to determine the weight average molecular weight (M w ) and number average molecular weight (M n ) was determined. Intrinsic viscosity, hydration radius and radius of gyration data were also obtained for each polymer.

[0088] Samples were dissolved in 1,2,4-trichlorobenzene at 160°C and stirred for 55 minutes, then transferred to 115°C and further stirred until the samples were analyzed. An aliquot was injected into a gel permeation chromatograph operated at 160°C. Triple detection by refractive index, viscosity, and light scattering was used for molecular characterization. Duplicate aliquots were analyzed and average results reported. [Table 1] [Table 2]

[0089] 1, each sample comprises a core layer C of homopolymer (polypropylene) and two coextruded sealing layers on each surface of the core layer, one outer layer O (called "outside") and one inner layer I (called "inside"), of ethylene-propylene or propylene-butylene copolymer or ethylene-propylene-butylene terpolymer with the loadings shown in Table 2. Each sample comprises in its sealing layers a blend of polymeric materials as detailed below.

[0090] The "Content" column, including subheadings "C2," "C3," and "C4," gives the mole percentage of each polymer in the copolymer and / or terpolymer blend in a given sample, and the following two columns, including the heading "Sample" and the subheadings "Inner" and "Outer," give the mole percentage of each polymer in the copolymers and / or terpolymers that make up the inner and outer layers, respectively.

[0091] So, for example, sample 1 has three different components in its sealing layer: Polymer A, Polymer B, Polymer C, The inner sealing layer therein comprises 50 mol% polymer B and 50 mol% polymer C, and the outer sealing layer comprises 30 mol% polymer A and 70 mol% polymer C. Thus, the C2 content of the inner sealing layer is 4 mol% since polymer C has a C2 content of 8 mol% and polymer B has a C2 content of 0 mol%, and the C2 content of the outer sealing layer of Sample 1 is 5.6 mol% since polymer C has a C2 content of 8 mol% and polymer A has a C2 content of 0 mol%, but the polymer C copolymer contributes to the total of 70% of the outer sealing layer.

[0092] The seal initiation temperature required to seal the inner and outer sealing layers of each of the samples was determined by the following method.

[0093] The seal initiation temperature (SIT) is considered to be the lowest temperature at which a seal is formed between two surfaces of a film at a set pressure and dwell time, the strength of which is at least 200g / 25mm. In the following examples, the seal initiation temperature of the inside / outside seal of the naked collation film was taken as the lowest temperature at which a seal strength of at least 200g / 25mm was achieved.

[0094] The seals in these examples were prepared using an RDM heat sealer with the pressure set at 5 psi and dwell time set at 0.5 seconds according to ASTM F2029. The seal strength was determined using an RDM seal puller after cooling according to ASTM F88. The seal strength was measured using an RDM puller with a pull speed (or jaw separation speed) of 300 mm / min. The peak strength was recorded as the seal strength.

[0095] The RDM heat sealer jaw configuration was metal to rubber. The upper jaw was made of metal with a Teflon coating on the surface to prevent the film from sticking to the jaws. The lower jaw was made of a metal base with a rubber top. During testing, the upper jaw was heated and the lower jaw was maintained at ambient temperature (atmospheric pressure (101.325 kPa) and a temperature of 25° C.). This resulted in only the upper jaw being heated.

[0096] The samples were cut lengthwise into 25mm wide strips. To determine the SIT of the samples, the upper jaw temperature was started at a low temperature, e.g. 65°C (the starting temperature depends on the film surface configuration, e.g. inside / inside, outside / outside, inside / outside). For each different temperature setting, three seals (lengthwise cut films) were made and the average seal strength was calculated. After recording the average seal strength, the sealing temperature was increased by 2°C and the procedure was repeated until the seal strength reached at least 200g / 25mm. In these examples, the lowest temperature resulting in a seal strength reaching at least 200g / 25mm is referred to as the seal initiation temperature.

[0097] The tack initiation temperature required to adhere the inner sealing layer to a unit wrap packaging film that is commonly used to package individual items (shown as package P in FIG. 1) in a naked collation package was also determined for three 20 μm thick commercially available unit wrap films, designated GLT, GLS and ZXA. GLT and GLS are commercially available from Innovia Films Limited (Lowther R&D Centre, West Road, Wigton, Cumbria, CA7 9XX, UK) and ZXA is commercially available from Innovia Films Mexico SA de CV (AV. Colorines 255, Corcentro, Sacapu, Michoacán, Mexico, CP58600). For the purposes of these examples, a 20 μm thick unit wrap film was selected, so that the GLT, GLS and ZXA films are referred to herein as GLT20, GLS20 and ZXA20, respectively. Each unit wrap packaging film has a three-layer structure including a homopolymeric polypropylene core layer, and inner and outer copolymeric skin layers. The outer skin layer, which is the layer adjacent to the naked collation film in the present use, comprises a terpolymer of polyethylene, polypropylene and polybutylene with a C4 content of 15.3 mol% for GLT, a blend of a copolymer of polyethylene and polyhexylene and a copolymer of polyethylene and polyoctylene with a C4 content of 0 mol% for GLS, and a copolymer of polyethylene and polypropylene with a C4 content of 0 mol% for ZXA. GLS and GLT films were produced by the bubble process and ZXA film by the tenter process.

[0098] The minimum temperature at which adhesion (at least 50g / 25mm seal strength) between the inner layer of the naked collation film and the outer layer of the unit wrap packaging film was achieved was measured and compared to the minimum temperature at which a seal strength of at least 200g / 25mm seal strength (SIT) was achieved for the naked collation film sample to itself (inside / outside), the difference being designated as the "incompatibility window." A positive incompatibility window is necessary for effectiveness, and generally the larger the incompatibility window, the better.

[0099] The incompatibility window, i.e., the tack initiation temperature required to cause the inner layer of the naked collation film to adhere to the outer layer of the unit wrap packaging film minus the sealing temperature required to seal the naked collation film sample to itself (inside / outside), was determined using the 3-layer hybrid test described below.

[0100] The incompatibility window was determined using the temperature range between the seal initiation temperature (SIT) of the inner / outer seal of the naked collation film, the method of which is described above (at least 200 g / 25 mm), and the temperature at which sticking occurs between the inner layer of the naked collation film and the outer layer of the unit wrap film (>50 g / 25 mm).

[0101] The incompatibility window was determined using a laboratory heat sealer per ASTM F2029 and a seal strength tester (after cooling per ASTM F88).

[0102] Three 25 mm wide strips of naked collation film and unit wrap cut in the machine direction were tested using a Laboratory Heat Sealer (RDM) with the pressure set at 5 psi and a dwell time of 0.5 seconds. The seal strength was measured using the RDM seal puller with the pulling speed (or jaw separation speed) set at 300 mm / min.

[0103] The RDM heat sealer jaw configuration used in this test was metal to rubber. The upper jaw was made of metal with a Teflon coating on the surface to prevent the film from sticking to the jaws. The lower jaw was made of a metal base with a rubber top. During the test, the upper jaw was heated and the lower jaw was maintained at ambient temperature (atmospheric pressure (101.325 kPa) and a temperature of 25° C.). To determine the SIT of the samples, the upper jaw temperature started at a lower temperature, e.g., 65° C.

[0104] The filmstrips were arranged in the following configuration: naked collation (top) / naked collation / unit wrap (bottom). The inner surface of each strip was facing down.

[0105] The first part of the test determines the Seal Initiation Temperature (SIT) for the naked collation inside / outside configuration. The temperature of the upper jaw was increased by 2°C until the seal strength reached at least 200g / 25mm. In the following examples, this temperature will be referred to as the SIT. When this point is reached, the bottom strip of unit wrap peels away from the top naked collation / naked collation seal.

[0106] The test is continued until a temperature occurs at which "tack" between the inner layer of the naked collation film and the outer layer of the unit wrap film occurs. In the examples below, "tack" is said to occur when the seal strength is at least 50g / 25mm.

[0107] The results, along with the mole percentage of C4 content of the inner and outer sealing layers for Samples 1-16, are shown in Table 3 below. [Table 3]

[0108] From Table 3, it can be seen that each sample produced a data set that included a range of three sealing incompatibility window values, as well as lower and higher C4 mol% values. Each of these data sets can be summarized graphically as a rectangle in mol%-temperature space defined by the highest and lowest sealing incompatibility window values ​​(°C) and the upper and lower mol% values. These rectangles are plotted in Figure 2. For example, sample 1, shown as rectangle S1 in Figure 2, is characterized by mol% values ​​of 16% and 17.6% and an upper incompatibility value of 12°C and a lower incompatibility value of 8°C. Sample 17 (S17) is an exception, as its three sealing incompatibility temperature values ​​are identical, i.e., 2°C, and therefore appear as a horizontal line. Samples S2 and S13 overlap almost completely.

[0109] Generally, there is a positive correlation between C4 content and positive sealing incompatibility values, which is shown by the dashed line L1. Usually, a value of at least +2°C is desirable to minimize the risk of undesired sealing of the naked collation film to the packaging film. It will be seen that this can typically be achieved by ensuring a C4 content of 10 mol% or more. The most preferred film samples according to the present invention have an average C4 polyolefin content in the inner and outer sealing layers of more than 10 mol% relative to the total polyolefin content of these sealing layers.

[0110] It will be apparent that the size of the incompatibilty window will be determined to some extent by the properties of the unit wrap selected. Thus, samples that only slightly miss delivering a good incompatibilty window in relation to the exemplified unit wrap materials cannot necessarily be dismissed as inappropriate for all unit wraps, as is indeed evident in relation to certain samples that show positive incompatibilty windows for some, but not all, samples. Nevertheless, these studies clearly demonstrate the general trends of the compositional requirements of suitable naked collation films, as detailed in the claims herein.

[0111] The molar ratios of the 16 samples are shown in Table 4 below. [Table 4]

[0112] The ceiling incompatibility window data set is plotted versus C4 / C2 molar ratio in Figure 3 in a manner similar to that plotted in Figure 2. A strong positive correlation between ceiling incompatibility window values ​​and C4 / C2 molar ratio is shown by line L2. Typically, a (desirable) positive ceiling incompatibility is obtained for a C4 / C2 molar ratio of at least 1.2, as shown by the intercept of C2 with the x-axis.

[0113] The ceiling incompatibility window data set is plotted versus C4 / C3 molar ratio in Figure 4 in a manner similar to that plotted in Figure 2. A strong positive correlation between ceiling incompatibility window values ​​and C4 / C3 molar ratio is shown by line L3. Typically, a (desirable) positive ceiling incompatibility is obtained for C4 / C3 molar ratios of at least 0.15, as shown by the intercept of C3 with the x-axis.

[0114] Seal Initiation Temperature (SIT) Samples were subjected to testing to determine the seal strength obtained when two strips were heat sealed inside to inside, outside to outside, and inside to outside at 5 psi with a 0.5 second dwell time. The average seal strengths observed are shown below in Table 5. [Table 5]

[0115] These data confirm that the film samples exhibit acceptably low seal initiation temperatures.

[0116] As can be seen from the results, in combination with the results disclosed in Table 7, the lower the SIT of the sample film, the larger the incompatibility window.

[0117] Friction coefficient The samples were tested in a Messmer Slip and Friction Tester apparatus in accordance with ASTM D1894, and the average coefficients of friction recorded, both static and dynamic, are shown in Table 6. [Table 6]

[0118] The coefficient of friction is known to be highly dependent on the surface properties of the film as well as the sealing properties of the polymer.

[0119] As will be appreciated by those skilled in the art, the coefficient of friction remains relatively low and therefore the film according to the present invention exhibits good hot slip properties.

[0120] Incompatibilities To investigate the degree of incompatibility between the naked collation film wrap samples and the films used on the unit wraps, heat seal threshold tests were performed using the 3-ply hybrid test (outlined above).

[0121] The inside seal of the naked collation film sample is tested against the outside of the unit wrap with the bottom jaw removed. The unit wrap films selected for this test were GLS20, GLT20, and ZXA20, all polyolefin unit wrap films. GLS20 and GLT20 are commercially available from Innovia Films Ltd (Wigton, Cumbria), and ZXA20 is commercially available from Innovia Films Mexico SA de CV (Sacapu, Mexico).

[0122] The samples were tested to determine the temperature at which a seal was formed. The tests were performed using a heat sealer operating at 5 psi pressure with a 0.5 second dwell time.

[0123] By determining the temperature at which a seal is formed between the naked collation film and the polyolefin film wrap, one can determine the incompatibility window over which heat sealing can be performed with minimal risk of a seal being formed between the naked collation film and the film wrap. [Table 7]

[0124] It is important that the incompatibility window has a positive value. It will be appreciated that the larger the positive incompatibility window, the more advantageous the operation. The incompatibility range or "incompatibility window" must be wide enough to allow sealing to occur without varying the heat seal temperature so that the naked collation film is sealed to the film wraps of the individual packages in the bundle.

[0125] Additionally, as can be seen from the results, the naked collation film of the present invention has the advantage that it performs substantially the same regardless of the composition of the unit wrap, and therefore different unit wrap materials can be used in conjunction with the naked collation film of the present invention without sacrificing the performance of the naked collation film.

[0126] Optical properties The optical properties of the outer and inner layers of the film were determined. Specifically, the gloss of the samples was recorded using ASTM D2457 test method. The gloss was measured using a Rhopoint glossmeter using a 45° angle. The results are shown below. [Table 8]

[0127] As will be apparent to one skilled in the art, the optical properties make the film suitable for use as a naked collation film.

[0128] Comparative Example Comparative examples of blocking biaxially oriented films were prepared using a method similar to that described above under "Film Preparation."

[0129] C1 is a comparative example according to Example 1 of EP 3034300, which is a blocking film. The sealing layer of C1 comprises a single C4-C3 polyolefin copolymer with a standard antiblock / slip package of 6% slide masterbatch ABVT3 NSC (commercialized by Schulman) in the outer layer and 1% antiblock masterbatch (commercialized by Constab) based on SiO2 particles with a diameter of 2 μm, and 6% antiblock masterbatch ABVT30N (commercialized by Schulman) in the inner layer, 1% antiblock masterbatch (commercialized by Constab) based on silica particles with a diameter of 2 μm.

[0130] Details are shown in Table 9 below.

[0131] The incompatibility window for C1 was determined following the same procedure detailed above for the inventive films. [Table 9]

[0132] Inter-pack blocking test A sheet of film was cut out using a cutting template (a rigid plate of 93 x 68 mm) and wrapped around a wooden block (teak or similar hardwood) with the test side facing outwards and positioned so that the test faces of the two wrapped blocks were in contact with each other. The wooden block had a self-adhesive felt cover on the test side, was 72 x 42 x 10 mm and weighed approximately 30 g.

[0133] The two wrapped blocks were placed perpendicularly on a metal plate with the test surfaces of the films in contact with each other and a weight of 200 g (± 2 g) was placed on top of the blocks. The samples were placed in a thermostatically controlled oven at 60°C for 72 hours, after which the samples were removed from the oven and allowed to cool for at least 30 minutes before further measurements as described below.

[0134] After cooling, the upper block was retained and the weight was removed. The sample was placed in the cradle of an electric horizontal test stand fitted with a Sauter™ gauge (Model FK50). The gauge speed was set at 800 mm / min. The test apparatus pushed the upper block along the surface of the lower block, which was held in place in the apparatus's cradle, and the peak reading was recorded as the force (in N) required to initiate relative lateral movement between the blocks, requiring lateral separation (unblocking) of the sheets.

[0135] In Table 10 below, if the force required to initiate relative lateral movement of the blocks is less than 5N, the inter-pack blocking test is a "pass." If the force required is more than 5N, the test is a "fail." [Table 10]

[0136] For experimental certainty, C1 according to the present invention, and samples 11 and 15 were tested five times in repeated tests, and the results are shown in Table 11. [Table 11]

[0137] To ensure the validity of the blocking test under various conditions, the above procedure was repeated using C1 according to the present invention, as well as samples 11 and 15, with the difference that the samples were placed in an oven for 3 hours instead of 72 hours and at a temperature of 75°C instead of 60°C, and the results are shown in Table 12. [Table 12]

[0138] As can be seen, the naked collation films used in the process of the present invention are pressed together at high pressures and temperatures for extended periods of time without forming any significant degree of blocking between them, as compared to films not according to the present invention. This means that wrapped bundles formed from films according to the present invention can be wrapped and shipped while still warm or hot following the wrapping procedure (or exposed to somewhat harsh conditions during transport or storage) without the risk of the wrapped packages sticking together and causing blocking.

[0139] Comparative Example C1, on the other hand, exhibits a wide incompatibility window, but is not suitable for use in naked collation packaging due to its tendency to block.

[0140] For a film to be "non-blocking" in accordance with the present invention, it is necessary that the film consistently, or at least on average, for 5 repeated tests, pass the blocking test under conditions of 60° for 72 hours, and preferably the film also consistently, or at least on average, for 5 repeated tests, pass the blocking test at 75° for 3 hours.

Claims

1. A non-blocking naked collation film comprising a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposing surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, and both the inner sealing layer and the outer sealing layer comprising a C4 polyolefin and at least one of a C2 and a C3 polyolefin, at least one of the sealing layers having a C4 polyolefin content greater than 10 mol% relative to the total polyolefin content of that sealing layer; one or both of the inner and outer sealing layers comprises a C2, C3, or C4 polyolefin; and At least the outer sealing layer comprises at least one copolymer or terpolymer having a melting point above 75°C; Non-blocking naked collation film.

2. 2. The non-blocking naked collation film of claim 1, wherein one or both of the inner sealing layer and the outer sealing layer comprises a blend of C2 / C3, C2 / C4 and / or C3 / C4 copolymers, and / or at least one C2 / C3 / C4 terpolymer.

3. 10. The non-blocking naked collation film of claim 1, wherein at least one of the sealing layers has a C4 polyolefin content of greater than 10.5 mol%, greater than 11.0 mol%, greater than 11.5 mol%, or greater than 12.0 mol%, based on the total polyolefin content of that sealing layer.

4. 2. The non-blocking naked collation film of claim 1, wherein the polyolefin outer sealing layer has a C4 polyolefin content of greater than 10 mol%, greater than 10.5 mol%, greater than 11.0 mol%, greater than 11.5 mol%, or greater than 12.0 mol%, based on the total polyolefin content of the outer sealing layer.

5. 5. The non-blocking naked collation film of claim 4, wherein the inner sealing layer and the outer sealing layer each have a C4 polyolefin content of greater than 10 mol%, greater than 10.5 mol%, greater than 11.0 mol%, greater than 11.5 mol%, or greater than 12.0 mol%, based on the total polyolefin content of that sealing layer.

6. 2. The non-blocking naked collation film of claim 1, wherein the average C4 polyolefin content in the inner and outer sealing layers is greater than 10 mol%, greater than 10.5 mol%, greater than 11.0 mol%, greater than 11.5 mol%, or greater than 12.0 mol%, based on the total polyolefin content of the sealing layers.

7. A non-blocking naked collation film comprising a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposing surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, both the inner and outer sealing layers comprising C2 and C4 polyolefins, and optionally a C3 polyolefin, at least one of the sealing layers having a C4:C2 molar ratio of at least 1.2; one or both of the inner sealing layer and the outer sealing layer comprises a C2, C3, or C4 polyolefin; and At least the outer sealing layer comprises at least one copolymer or terpolymer having a melting point above 75°C; Non-blocking naked collation film.

8. i. At least one of the sealing layers has a C4:C2 molar ratio of at least 1.5; or ii. the polyolefin outer sealing layer has a C4:C2 molar ratio of at least 1.2; or iii. each of the inner sealing layer and the outer sealing layer has a C4:C2 molar ratio of at least 1.2; or iv. the average C4:C2 molar ratio of the inner sealing layer and the outer sealing layer is at least 1.2; The non-blocking naked collation film of claim 7.

9. A non-blocking naked collation film, comprising: a polyolefin inner sealing layer on one surface of the film and a polyolefin outer sealing layer on an opposite surface of the film, the outer sealing layer being sealable to itself and to the inner sealing layer, both the inner and outer sealing layers comprising C3 and C4 polyolefins, and optionally a C2 polyolefin, at least one of the sealing layers having a C4:C3 molar ratio of at least 0.15; one or both of the inner sealing layer and the outer sealing layer comprises a C2, C3, or C4 polyolefin; and At least the outer sealing layer comprises at least one copolymer or terpolymer having a melting point above 75°C; Non-blocking naked collation film.

10. i. At least one of the sealing layers has a C4:C3 molar ratio of at least 0.16; or ii. the polyolefin outer sealing layer has a C4:C3 molar ratio of at least 0.15; or iii. each of the inner sealing layer and the outer sealing layer has a C4:C3 molar ratio of at least 0.15; or iv. the average C4:C3 molar ratio in the inner sealing layer and the outer sealing layer is at least 0.15; The non-blocking naked collation film of claim 9.

11. i. At least one, and preferably both, of the sealing layers has a C4:C2 molar ratio of at least 1.2; and / or ii. at least one, and preferably both, of said sealing layers has a C4:C3 molar ratio of at least 0.15; The non-blocking naked collation film of claim 1.

12. 10. The non-blocking naked collation film of claim 1 further comprising a polyolefin core layer on which the inner and outer sealing layers are formed, and optionally, at least the outer sealing layer comprises at least one copolymer or terpolymer having a melting point greater than 80°C.

13. 10. The non-blocking naked collation film of claim 1, wherein one or both of the sealing layers comprises a blend of two or more copolymers of ethylene and propylene, ethylene and butylene, propylene and butylene, and / or a terpolymer of ethylene, propylene and butylene.

14. 10. A naked collation package comprising a plurality of individually wrapped packages sealed and packaged with the non-blocking naked collation film of claim 1, optionally each individually wrapped package comprising a further polyolefin film in contact with the inner sealing layer.

15. 1. A method for forming a naked collation package, comprising: a) providing an arrangement of individually wrapped packages; b) providing a non-blocking naked collation film according to any one of claims 1 to 13; c) arranging the individually wrapped packages into an ordered configuration; d) placing said non-blocking naked collation film at least partially surrounding said custom configuration of individually wrapped packages; e) sealing the non-blocking naked collation film to itself without sealing the non-blocking naked collation film to the package; A method comprising:

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